Preparation apparatus and preparation process for nylon salt solution

Abstract

A preparation apparatus and a preparation process for a nylon salt solution. The preparation apparatus comprises a suspension preparation device (10), a first salt-forming kettle (16) and a second salt-forming kettle (18) which are communicated in sequence. The suspension preparation device comprises a charging device (11), a continuous feeding device (12), a high-speed shearing pump (13) and a preparation kettle (14), wherein the high-speed shearing pump (13) and the preparation kettle (14) are circularly communicated by means of two communicating pipes (131); the second salt-forming kettle (18) is provided with a second diamine feeding pipe (181) and a third diamine feeding pipe (182), and is further provided with a circulating pipe (184); and an online near-infrared monitoring device (185) is arranged on the circulating pipe (184) of the second salt-forming kettle.

Description

Device and process for preparing a nylon salt solution

[0001] Related applications

[0002] The present application claims priority to the Chinese patent application No. 202410624089.2, filed on May 20, 2024, entitled “Device and process for preparing a nylon salt solution”, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of nylon, in particular to a device and process for preparing a nylon salt solution. BACKGROUND

[0004] Polyamide (PA), commonly known as nylon, is a general term for high polymers containing amide groups (-NH-C=O) in the repeating units of the main chain. It can be prepared by evaporating a salt solution of aliphatic dicarboxylic acid and diamine and then heating it to polymerize, such as nylon 66. However, this method requires that the dicarboxylic acid and diamine in the salt solution have a consistent molar balance. For example, when producing nylon 66 from adipic acid (AA) and hexamethylene diamine (HMD), an unbalanced molar ratio will result in a lower molecular weight and affect the dyeability of the nylon yarn.

[0005] In the early stage of the industry, the batch salt process was generally used, which constantly sampled and tested the amine acid molar ratio in the salt-making kettle to achieve molar balance. However, the batch process is not suitable for large-scale industrial production. In addition, aliphatic dicarboxylic acids, such as adipic acid powder, have a wide particle size distribution, resulting in a bulk density in a large range, such as 0.6-0.7 g / cm 3 The general volumetric metering method has a large error, which is not conducive to obtaining a salt solution with a consistent molar ratio.

[0006] SUMMARY

[0007] Therefore, it is necessary to provide a device and process for preparing a nylon salt solution to address the above problems. The molar ratio of dicarboxylic acid and diamine in the nylon salt solution obtained by using the device and process is more accurate.

[0008] The application discloses a preparation device for nylon salt solution, which comprises a suspension preparation device, the suspension preparation device comprises feeding equipment, continuous feeding equipment, a high-speed shearing pump and a preparation kettle provided with a water inlet pipe, which are sequentially communicated, and the high-speed shearing pump and the preparation kettle are circularly communicated through two communication pipes, the feeding equipment is used for feeding aliphatic dicarboxylic acid, the continuous feeding equipment is used for feeding aliphatic dicarboxylic acid into the high-speed shearing pump, and the aliphatic dicarboxylic acid and water can be circularly prepared into aliphatic dicarboxylic acid suspension between the high-speed shearing pump and the preparation kettle; a first salt making kettle is communicated with the suspension preparation device, and the first salt making kettle is provided with a first diamine feeding pipe for preparing the aliphatic dicarboxylic acid suspension and diamine into a primary nylon salt solution; a second salt making kettle is communicated with the first salt making kettle, and the second salt making kettle is provided with a second diamine feeding pipe and a third diamine feeding pipe for preparing the primary nylon salt solution and diamine into a nylon salt solution, wherein the second salt making kettle is further provided with a circulation pipe, and an on-line near-infrared monitoring device is further arranged on the circulation pipe of the second salt making kettle, which is used for monitoring the molar ratio of dicarboxylic acid and diamine in the nylon salt solution, and the feeding amount of diamine in the third diamine feeding pipe is controlled according to the monitoring result.

[0009] In one of the embodiments, the preparation device further comprises a suspension storage tank, which is communicated with the suspension preparation device and is used for storing the aliphatic dicarboxylic acid suspension prepared by the suspension preparation device, and the first salt making kettle is communicated with the suspension storage tank; and / or the preparation device further comprises a primary nylon salt storage tank, which is communicated with the first salt making kettle and is used for storing the primary nylon salt solution prepared by the first salt making kettle, and the second salt making kettle is communicated with the primary nylon salt storage tank; and / or the preparation device further comprises a nylon salt storage tank, which is communicated with the second salt making kettle and is used for storing the nylon salt solution prepared by the second salt making kettle.

[0010] In one of the embodiments, the number of the suspension preparation devices is one or more than two, and each of the suspension preparation devices is communicated with the suspension storage tank.

[0011] In one of the embodiments, the suspension storage tank is provided with a circulation pipe for circulating the aliphatic dicarboxylic acid suspension in the suspension storage tank; and / or the primary nylon salt storage tank is provided with a circulation pipe for circulating the primary nylon salt solution in the primary nylon salt storage tank; and / or the first salt making kettle is provided with a circulation pipe for circulating the primary nylon salt solution in the first salt making kettle.

[0012] In one of the embodiments, an on-line density meter is further arranged on the circulating pipeline of the suspension storage tank, for monitoring and feeding back the concentration change of the aliphatic dicarboxylic acid suspension in real time.

[0013] In one of the embodiments, a first heat exchanger is arranged on the circulating pipeline of the first salt-forming kettle; and / or, a second heat exchanger is arranged on the circulating pipeline of the second salt-forming kettle.

[0014] In one of the embodiments, the on-line near-infrared monitoring device is a non-contact on-line near-infrared monitoring device.

[0015] A preparation process of a nylon salt solution, using the preparation device of the nylon salt solution, comprising the following steps: water is introduced into the preparation kettle through a water inlet pipe, and a high-speed shearing pump is started to circulate water between the preparation kettle and the high-speed shearing pump; aliphatic dicarboxylic acid is fed through a feeding device and mixed with water in the high-speed shearing pump through a continuous feeding device, and circulated between the high-speed shearing pump and the preparation kettle to prepare an aliphatic dicarboxylic acid suspension; the aliphatic dicarboxylic acid suspension is transferred to a first salt-forming kettle, and diamine is added to the first salt-forming kettle through a first diamine feeding pipe to prepare a primary nylon salt solution; the primary nylon salt solution is transferred to a second salt-forming kettle, and diamine is added to the second salt-forming kettle through a second diamine feeding pipe and a third diamine feeding pipe to prepare a nylon salt solution, wherein the amount of diamine fed through the third diamine feeding pipe is controlled by an on-line near-infrared monitoring device arranged on the circulating pipeline of the second salt-forming kettle.

[0016] In one of the embodiments, the aliphatic dicarboxylic acid suspension prepared by the suspension preparation device is transferred to a suspension storage tank, and then the aliphatic dicarboxylic acid suspension in the suspension storage tank is transferred to a first salt-forming kettle; and / or, the primary nylon salt solution prepared by the first salt-forming kettle is transferred to a primary nylon salt storage tank, and then the primary nylon salt solution in the primary nylon salt storage tank is transferred to a second salt-forming kettle; and / or, the nylon salt solution prepared by the second salt-forming kettle is transferred to a nylon salt storage tank.

[0017] In one of the embodiments, the preparation process further satisfies at least one of the following conditions: (1) the concentration of the aliphatic dicarboxylic acid suspension is 35wt%-52wt%; (2) the molar ratio of dicarboxylic acid to diamine in the primary nylon salt solution is 1.5:1-3:1, and the concentration is 40wt%-62wt%; (3) the concentration of the nylon salt solution is 50wt%-65wt%.

[0018] The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the application will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the accompanying drawings needed in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the accompanying drawings in the following description only are a part of the embodiments of the application, and for those skilled in the art, other drawings can be obtained from the disclosed drawings without any creative effort.

[0020] Fig. 1 is a structural schematic diagram of a preparation device of a nylon salt solution according to the application.

[0021] Fig. 2 is a schematic diagram of a non-contact online near-infrared monitoring device according to the application.

[0022] Fig. 1 is a structural schematic diagram of a preparation device of a nylon salt solution according to the application. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the application will be described clearly and completely in combination with the accompanying drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without any creative effort fall within the protection scope of the application.

[0024] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0025] In order to facilitate the understanding of the present application, the present application will be described in more detail below. However, it should be understood that the present application can be implemented in many different forms, and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the disclosure of the present application more thorough and comprehensive.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the specification of the present application is only for the purpose of describing the specific embodiments or examples of the present application, and is not intended to limit the present application. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0027] The prior art adopts a loss-in-weight metering, i.e. gravimetric metering, method to solve the problem of accurate metering of aliphatic dicarboxylic acid during feeding. The metered aliphatic dicarboxylic acid is continuously dispersed in a single continuous stirred tank reactor, while introducing a diamine and water to obtain a salt solution with a certain concentration and ratio, and then introducing it into a storage tank for temporary storage or used in another continuous stirred tank reactor, while introducing a second diamine, and introducing a third diamine through online pH feedback to obtain a salt solution with a desired equilibrium molar ratio.

[0028] However, on the one hand, the loss of weight scale is generally divided into two modes of weight and volume, that is, when the material liquid level in the loss of weight scale buffer bin is high, the weight change can continuously output the weight signal to the rear end, but as the liquid level gradually decreases, because the reduction of the material will cause the loss of weight signal to fluctuate, until the liquid level is lowered to a low level, it needs to be switched to a volume feeding mode, that is, the output frequency of the loss of weight scale is fixed, and the loss of weight signal is fixed before the mode switching. In the volume mode, the loss of weight scale buffer is replenished. Although the replenishment time can be completed in a short time, and then switched back to the weight mode, but in the volume mode of fixed frequency output, it causes a large error and fluctuation in the metering of aliphatic dicarboxylic acid, which is not conducive to the expected molar ratio. In addition, the general loss of weight scale is used after accurately metering a small amount of material per unit time, which leads to the fact that as the polyamide production capacity increases, it is difficult to choose a suitable loss of weight scale, or it needs to invest in expensive loss of weight scale, and at the same time, a larger volume of loss of weight scale further expands the metering error of aliphatic dicarboxylic acid because of the long switching time between the loss of weight mode and the volume mode, which is not conducive to the expected molar ratio of the salt solution. On the other hand, the solid aliphatic dicarboxylic acid is directly mixed with the diamine and water to prepare the salt solution, and the oxygen in the air entrained by the solid aliphatic dicarboxylic acid is easy to oxidize the salt solution, thereby bringing about the undesirable color and affecting the product quality.

[0029] In addition, although the molar ratio of the salt solution can be adjusted by controlling the rate and flow of the subsequent introduction of the diamine. As in the prior art, the subsequent introduction of the diamine into the recirculation pipeline includes one or more pumps, and can also include temperature control devices such as coils, jackets or devices containing heat exchangers, temperature measuring devices and controllers. The temperature control device can control the temperature of the nylon salt solution in the recirculation loop, thereby preventing boiling or churning of the nylon salt solution. That is, this recirculation pipeline needs to dilute and cool the high-concentration nylon salt to a suitable working environment of pH and temperature (25-30°C) for online pH measurement. This requires additional valves, pipelines, heat exchangers, pumps and other devices and instruments, which are complicated and increase investment. Most importantly, the pH is relatively harsh for the working environment, such as fluctuations in detection temperature and concentration will bring about a large detection error, which in turn affects the above-mentioned patent to adjust the addition of diamine by pH feedback. In addition, it cannot be ignored that because of the dilution of the salt solution, unnecessary water is introduced, which will bring about a large fluctuation in the concentration of the salt solution, which is also not conducive to the subsequent polymerization.

[0030] As shown in FIG. 1, the device for preparing the nylon salt solution provided by the present application includes, in sequence, a suspension preparation device for preparing an aliphatic dicarboxylic acid suspension, a first salt making kettle 16 for preparing a primary nylon salt solution, and a second salt making kettle 18 for preparing a nylon salt solution.

[0031] Further, the preparation device can further comprise a suspension storage tank 15 for storing the aliphatic dicarboxylic acid suspension, the suspension storage tank 15 being respectively connected to the suspension preparation equipment and the first salting kettle 16; and / or, the preparation device can further comprise a primary nylon salt storage tank 17 for storing the primary nylon salt solution, the primary nylon salt storage tank 17 being respectively connected to the first salting kettle 16 and the second salting kettle 18; and / or, the preparation device can further comprise a nylon salt storage tank 19 for storing the nylon salt solution, the nylon salt storage tank 19 being connected to the second salting kettle 18.

[0032] The suspension preparation equipment comprises a feeding device 11, a continuous feeding device 12, a high-speed shearing pump 13 and a preparation kettle 14, and the preparation kettle 14 is further provided with a water inlet pipe 141 for feeding water into the preparation kettle 14 for preparing the suspension.

[0033] In the suspension preparation equipment, the feeding device 11, the continuous feeding device 12 and the high-speed shearing pump 13 are sequentially connected, wherein the feeding device 11 is used for feeding the aliphatic dicarboxylic acid, and the continuous feeding device 12 is used for feeding the aliphatic dicarboxylic acid into the high-speed shearing pump 13. In addition, the high-speed shearing pump 13 and the preparation kettle 14 are connected through two connecting pipes 131, so that the aliphatic dicarboxylic acid and water can circulate between the high-speed shearing pump 13 and the preparation kettle 14 to prepare the aliphatic dicarboxylic acid suspension.

[0034] In some embodiments, the feeding device 11 is provided with a vibrator to assist the rapid feeding of the aliphatic dicarboxylic acid, and the continuous feeding device 12 is selected from a screw feeder or a rotary feeder.

[0035] When the suspension preparation equipment of the present application is used to prepare the aliphatic dicarboxylic acid suspension, the high-speed shearing pump 13 can generate a micro-negative pressure when circulating the material, such as when circulating water and the mixture of water and aliphatic dicarboxylic acid, so that the high-speed shearing pump 13 forms a vacuum suction state, so that the aliphatic dicarboxylic acid is rapidly and completely dispersed into the suspension; at the same time, the high-speed shearing pump 13 can form water mist. Further, when the suspension preparation equipment of the present application is used to prepare the aliphatic dicarboxylic acid suspension, the agglomeration between the aliphatic dicarboxylic acid powders can be avoided, and the water can be rapidly contacted with the aliphatic dicarboxylic acid powders to form an ideal and uniform dispersion solution.

[0036] In addition, the aliphatic dicarboxylic acid is directly fed by weight, such as directly purchasing ton-bagged aliphatic dicarboxylic acid, and the weight error is generally within 0.5%, which is small and can accurately measure the feeding amount.

[0037] Therefore, the application can effectively solve the problem of feeding error caused by using the loss-in-weight scale in the prior art, and can make the molar ratio of the dicarboxylic acid and the diamine in the nylon salt solution obtained in subsequent salt formation more accurate.

[0038] In addition, the preparation kettle 14 can also be provided with a first nitrogen pipe 142 for introducing nitrogen into the preparation kettle 14, so that when the aliphatic dicarboxylic acid suspension is prepared by using the suspension preparation device of the application, the air entrained in the aliphatic dicarboxylic acid feeding can also be replaced by nitrogen, thereby reducing the risk of oxidation of the subsequent salt solution.

[0039] Specifically, the suspension storage tank 15 is connected to the suspension preparation device and is used for storing the aliphatic dicarboxylic acid suspension prepared by the suspension preparation device. It can be understood that the connection mode of the suspension storage tank 15 and the suspension preparation device is not limited, and the suspension storage tank 15 can be directly connected to the preparation kettle 14 through a pipeline or can be connected to any communication pipeline between the preparation kettle 14 and the high-speed shearing pump 13 through a pipeline.

[0040] In some embodiments, the suspension storage tank 15 is provided with a suspension storage tank circulating pipeline 151 for circulating the aliphatic dicarboxylic acid suspension in the suspension storage tank 15, so as to ensure that the aliphatic dicarboxylic acid suspension is in a uniform state. The suspension storage tank circulating pipeline 151 can include a circulating pump and a spray head, and the aliphatic dicarboxylic acid suspension flows in the pipeline through the circulating pump and is sprayed out through the spray head to mix with the aliphatic dicarboxylic acid suspension in the suspension storage tank 15 again.

[0041] Further, the suspension storage tank circulating pipeline 151 is also provided with an online densimeter 152 for real-time monitoring and feedback of the concentration change of the aliphatic dicarboxylic acid suspension, so as to make the molar ratio of the dicarboxylic acid and the diamine in the nylon salt solution obtained in subsequent salt formation more accurate.

[0042] In some embodiments, the number of the suspension preparation devices is one set or more than two sets, and each set of the suspension preparation device is connected to the suspension storage tank 15, and the design is specifically according to the production capacity requirement, so as to improve the efficiency.

[0043] Specifically, when there is no suspension tank 15, the first salt making kettle 16 is directly connected to the suspension preparation device, and when there is a suspension tank 15, the first salt making kettle 16 is connected to the suspension tank 15, and can receive the aliphatic dicarboxylic acid suspension in the suspension preparation device or the suspension tank 15. The first salt making kettle 16 is also provided with a first diamine feeding pipe 161 for feeding diamine into the first salt making kettle 16, and the amount of diamine fed can be controlled by a flow meter and a regulating valve. Thus, the first salt making kettle 16 can be used to prepare the aliphatic dicarboxylic acid suspension and diamine into a primary nylon salt solution. In some embodiments, the first salt making kettle 16 is also provided with a stirrer for assisting the mixing and salt making of the aliphatic dicarboxylic acid suspension and diamine. It can be understood that when the first salt making kettle 16 is connected to the suspension tank 15, the connection mode is not limited, and the first salt making kettle 16 can be directly connected to the suspension tank 15 through a pipe or connected to the circulating pipe 151 of the suspension tank 15 through a pipe. When the first salt making kettle 16 is connected to the suspension preparation device, the connection mode is not limited, and the first salt making kettle 16 can be directly connected to the preparation kettle 14 through a pipe or connected to any connecting pipe between the preparation kettle 14 and the high-speed shearing pump 13 through a pipe.

[0044] In some embodiments, the first salt making kettle 16 can also be provided with a second nitrogen pipe 162 for feeding nitrogen into the first salt making kettle 16, so that when the primary nylon salt solution is prepared, the air entrained in the diamine feeding can be replaced by nitrogen, thereby reducing the risk of oxidation of the salt solution.

[0045] In some embodiments, the first salt making kettle 16 is provided with a first salt making kettle circulating pipe 163 for circulating the primary nylon salt solution in the first salt making kettle. A circulating pump can be provided on the first salt making kettle circulating pipe 163. Further, the first salt making kettle circulating pipe 163 is also provided with a first heat exchanger 164, so that when the primary nylon salt solution circulates in the first salt making kettle circulating pipe 163, the temperature can be controlled by the first heat exchanger 164.

[0046] Specifically, the primary nylon salt tank 17 is connected to the first salt making kettle 16 for storing the primary nylon salt solution prepared by the first salt making kettle 16. It can be understood that the connection mode of the primary nylon salt tank 17 and the first salt making kettle 16 is not limited, and the primary nylon salt tank 17 can be directly connected to the first salt making kettle 16 through a pipe or connected to the first salt making kettle circulating pipe 163 through a pipe.

[0047] In some embodiments, the primary nylon salt storage tank 17 is provided with a primary nylon salt storage tank circulating pipeline 171 for circulating the primary nylon salt solution in the primary nylon salt storage tank 17, which can include a circulating pump and a spray head, the primary nylon salt solution flows in the pipeline by the circulating pump and is sprayed out by the spray head to be mixed with the primary nylon salt solution in the primary nylon salt storage tank 17 again.

[0048] In some embodiments, the primary nylon salt storage tank 17 can also be provided with a third nitrogen pipe 172 for introducing nitrogen into the primary nylon salt storage tank 17 to reduce the risk of oxidation of the primary nylon salt solution.

[0049] In some embodiments, an online density meter can also be provided on the primary nylon salt storage tank circulating pipeline 171 for real-time monitoring and feedback of the concentration change of the primary nylon salt solution.

[0050] Specifically, when there is no primary nylon salt storage tank 17, the second salting kettle 18 is directly communicated with the first salting kettle 16, and when there is a primary nylon salt storage tank 17, the second salting kettle 18 is communicated with the primary nylon salt storage tank 17 and can receive the primary nylon salt solution in the first salting kettle 16 or the primary nylon salt storage tank 17, and the second salting kettle 18 has a second diamine feeding pipe 181 and a third diamine feeding pipe 182 for introducing diamines into the second salting kettle 18, respectively, and the amount of diamines introduced into the second diamine feeding pipe 181 and the third diamine feeding pipe 182 can be controlled by a flow meter and an adjusting valve. Therefore, the second salting kettle 18 can be used to prepare a nylon salt solution by mixing the primary nylon salt solution with diamines.

[0051] In some embodiments, the second salting kettle 18 can also be provided with a fourth nitrogen pipe 183 for introducing nitrogen into the second salting kettle 18, so that the air entrained in the diamine feeding can be replaced by nitrogen, reducing the risk of oxidation of the salt solution.

[0052] More specifically, the second salting kettle 18 also has a second salting kettle circulating pipeline 184, and an online near-infrared monitoring device 185 is provided on the second salting kettle circulating pipeline 184 for monitoring the molar ratio of dicarboxylic acid and diamine in the nylon salt solution, and controlling the feeding amount of diamines in the third diamine feeding pipe 182 according to the monitoring result, so that a nylon salt solution with a more accurate molar ratio of dicarboxylic acid and diamine can be obtained.

[0053] The online near-infrared monitoring device 185 is used to monitor the molar ratio of the dicarboxylic acid and the diamine in the nylon salt solution, which avoids the concentration problem caused by sampling and adding additional water for dilution. Compared with the pH detection which is sensitive to temperature, the online near-infrared monitoring device 185 can stably measure at a temperature of ±10°C, thereby avoiding the imbalance of the molar ratio caused by the temperature influence in the pH detection.

[0054] In addition, the online near-infrared monitoring device 185 is simple to install and operate, and can simultaneously feed back the key information such as the amine group / carboxyl group ratio in the nylon salt solution and the salt solution concentration. Unlike the online pH detector or the refractometer, the online near-infrared monitoring device 185 does not need to be additionally provided with a bypass loop, a heat exchanger, and special pipelines with an adjusting valve and a flowmeter, thereby greatly saving the construction and use costs.

[0055] Further, as shown in FIG. 2, in some embodiments of the present application, the online near-infrared monitoring device 185 is a non-contact online near-infrared monitoring device, which includes a large-spot light source 185a and a receiver 185c, and the circulating pipeline 184 of the second salt formation kettle is provided with a transparent section 185b. Therefore, compared with the contact online near-infrared monitoring device which may have a test error caused by the gas bubbles in the nylon salt solution, the monitoring result of the non-contact online near-infrared monitoring device is more accurate. At the same time, the use cost and maintenance cost of the non-contact online near-infrared monitoring device are also more economical than those of the contact online near-infrared monitoring device.

[0056] In some embodiments, the second salt formation kettle 18 further has a stirrer for assisting the primary nylon salt solution to rapidly complete the mixing and salt formation with the diamine. It can be understood that when the second salt formation kettle 18 is communicated with the first salt formation kettle 16, the communication manner is not limited, and the second salt formation kettle 18 can be directly communicated with the first salt formation kettle 16 through a pipeline or communicated with the circulating pipeline 163 of the first salt formation kettle through a pipeline. When the second salt formation kettle 18 is communicated with the primary nylon salt storage tank 17, the communication manner is not limited, and the second salt formation kettle 18 can be directly communicated with the primary nylon salt storage tank 17 through a pipeline or communicated with the circulating pipeline 171 of the primary nylon salt storage tank through a pipeline.

[0057] In some embodiments, the circulating pipeline 184 of the second salt formation kettle can be provided with a circulating pump. Further, the circulating pipeline 184 of the second salt formation kettle is further provided with a second heat exchanger 186, so that the temperature of the nylon salt solution circulating in the circulating pipeline 184 of the second salt formation kettle can be controlled through the second heat exchanger 186.

[0058] Specifically, the nylon salt storage tank 19 is connected to the second salt making kettle 18 for storing the nylon salt solution prepared by the second salt making kettle 18. It can be understood that the connection mode of the nylon salt storage tank 19 and the second salt making kettle 18 is not limited, which can be directly connected to the second salt making kettle 18 through a pipeline, or connected to the circulating pipeline 184 of the second salt making kettle through a pipeline.

[0059] In some embodiments, the nylon salt storage tank 19 is provided with a nylon salt storage tank circulating pipeline 191 for circulating the nylon salt solution in the nylon salt storage tank 19. The nylon salt storage tank circulating pipeline 191 can include a circulating pump and a spray head, and the nylon salt solution flows in the pipeline through the circulating pump and is sprayed out through the spray head, and is mixed with the nylon salt solution in the nylon salt storage tank 19.

[0060] In some embodiments, the nylon salt storage tank 19 can also be provided with a fifth nitrogen pipe 192 for introducing nitrogen into the nylon salt storage tank 19 to reduce the risk of oxidation of the salt solution in the nylon salt storage tank 19.

[0061] The application also provides a process for preparing a nylon salt solution using the preparation device, comprising the following steps:

[0062] Water is introduced into the preparation kettle 14 through the water inlet pipe 141, and the high-speed shearing pump 13 is started to circulate the water between the preparation kettle 14 and the high-speed shearing pump 13, so that the high-speed shearing pump 13 forms a micro-negative pressure, then the aliphatic dicarboxylic acid is fed through the feeding device 11 and mixed with water in the high-speed shearing pump 13 and circulated between the high-speed shearing pump 13 and the preparation kettle 14 to prepare an aliphatic dicarboxylic acid suspension, and the aliphatic dicarboxylic acid suspension is transferred to the suspension storage tank 15 or directly to the first salt making kettle 16.

[0063] In some embodiments, after the aliphatic dicarboxylic acid feeding is completed, the continuous feeding device 12 is closed, and the circulation between the high-speed shearing pump 13 and the preparation kettle 14 continues, which can obtain a more uniform aliphatic dicarboxylic acid suspension.

[0064] In some embodiments, the aliphatic dicarboxylic acid suspension in the suspension storage tank 15 is circulated through the suspension storage tank circulating pipeline 151 to ensure that the aliphatic dicarboxylic acid suspension is in a uniform state, and the concentration change of the aliphatic dicarboxylic acid suspension is monitored and fed back in real time by the online densimeter 152 during circulation, so as to accurately control the amount during preparation of the primary nylon salt.

[0065] In some embodiments, the concentration of the aliphatic dicarboxylic acid suspension is 35wt%-52wt%, and the concentration fluctuation is less than 0.1wt%, even less than 0.05wt% by using the preparation process of the present application.

[0066] In some embodiments, the aliphatic dicarboxylic acid is selected from C4-C12 dicarboxylic acids, such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, and the like.

[0067] When the aliphatic dicarboxylic acid suspension is transferred to the first salt-making kettle 16, a diamine is added to the first salt-making kettle 16 through the first diamine feeding pipe 161 to prepare a primary nylon salt solution. In some embodiments, the concentration of the aliphatic dicarboxylic acid suspension is monitored and fed back in real time by the online densitometer 152, and the feeding amount is controlled according to the required molar ratio of dicarboxylic acid to diamine in the primary nylon salt solution. In some embodiments, the molar ratio of dicarboxylic acid to diamine in the primary nylon salt solution is 1.5:1-3:1, and the concentration is 40wt%-62wt%. In some embodiments, the molar ratio of dicarboxylic acid to diamine is 2:1-2.5:1, and the concentration is 50wt%-60wt%.

[0068] In some embodiments, the primary nylon salt solution in the first salt-making kettle 16 is circulated through the circulation pipe 163 of the first salt-making kettle, and the temperature is controlled at 50℃-80℃ by the first heat exchanger 164.

[0069] Then, the primary nylon salt solution in the first salt-making kettle 16 is transferred to the primary nylon salt storage tank 17 or directly to the second salt-making kettle 18. When the primary nylon salt solution is transferred to the second salt-making kettle 18, a diamine is added to the second salt-making kettle 18 through the second diamine feeding pipe 181 and the third diamine feeding pipe 182 to prepare a nylon salt solution, which is directly used in the polyamide production process or is transferred to the nylon salt storage tank 19.

[0070] In some embodiments, the total feeding amount of diamine in the second diamine feeding pipe 181 and the third diamine feeding pipe 182 is controlled according to the required concentration and molar ratio of dicarboxylic acid to diamine of the final nylon salt solution. The diamine feeding amount of the third diamine feeding pipe 182 is controlled by the online near-infrared monitoring device 185 on the circulation pipe 184 of the second salt-making kettle. In some embodiments, the concentration of the nylon salt solution is 50wt%-65wt%.

[0071] In some embodiments, the nylon salt solution in the second salt-making kettle 18 is circulated through the circulation pipe 184 of the second salt-making kettle, and the temperature is controlled at 60℃-110℃ by the second heat exchanger 186.

[0072] In some embodiments, the diamine is selected from C4-C12 diamines, such as 1,4-butanediamine, 1,-5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, lauryl diamine, and the like.

[0073] In the following, the preparation device and the preparation process of the nylon salt solution will be further illustrated by the following specific examples.

[0074] Example 1

[0075] The ton bag of adipic acid is hoisted to the bag opening position by the electric hoist of the feeding device 11. At the same time, 1500 kg of pure water is injected into the preparation kettle 14, and the high-speed shearing pump 13 is started to make the pure water in the preparation kettle 14 circulate between the high-speed shearing pump 13 and the preparation kettle 14. When the above circulation is established, the ton bag of adipic acid is opened, and the continuous feeding device 12 is used to feed the high-speed shearing pump 13. The feeding can be completed within 6 minutes, and the adipic acid is mixed with water, and the adipic acid suspension is obtained by circulating between the high-speed shearing pump 13 and the preparation kettle 14, and stored in the suspension storage tank 15. The concentration is 39.9 wt% by feeding back through the online densimeter 113.

[0076] The adipic acid suspension with a concentration of 39.9 wt% is measured as 1577 kg, and is transferred to the first salt formation kettle 16. The adipic diamine with a concentration of 200 kg is measured, and is added to the first salt formation kettle 16 through the first diamine feeding pipe 161. The primary nylon salt solution is prepared in the first salt formation kettle 16, and the temperature of the primary nylon salt solution is controlled at 65°C by the first heat exchanger 164. The concentration is 52.5 wt%. The amine-acid ratio of the primary nylon salt solution is 1:2.49 by offline sampling test, and the measurement error is 0.39% converted to adipic acid.

[0077] Comparative Example 1

[0078] The adipic acid is measured as 1000 kg by the loss-in-weight scale, and the loss-in-weight signal is fed back to the adipic diamine 317.8 kg and the water 1192 kg. The required adipic diamine and water are measured in equal proportions to obtain the primary nylon salt solution with a concentration of 52.5 wt% and an amine-acid ratio of 1:2.5. The 1000 kg of adipic acid is completed by feeding through three times of volume mode. The temperature of the primary nylon salt solution is controlled at 65°C by the heat exchanger. The amine-acid ratio of the primary nylon salt solution is 1:2.45 by offline sampling test, and the measurement error is 2% converted to adipic acid.

[0079] From the example 1 and the comparative example 1, it can be seen that the primary nylon salt solution prepared from the adipic acid suspension prepared by the preparation device and the preparation process of the present application can obtain a more close target amine-acid ratio, that is, the accuracy of the adipic acid measurement is higher.

[0080] Example 2

[0081] The primary nylon salt solution with an amine acid ratio of 1:2.5 and a concentration of 55wt% is continuously fed into the second salting kettle 18 at a flow rate of 1000kg / h, while the hexamethylenediamine in the second diamine feeding pipe 181 is fed at a flow rate of 122.8kg / h, and pure water is fed at a flow rate of 47kg / h, to prepare a nylon salt solution with an amine acid ratio of 1:1 and a concentration of 60wt% in the second salting kettle 18. The hexamethylenediamine in the third diamine feeding pipe 182 is fed back by the non-contact online near-infrared monitoring device to obtain a nylon salt solution with an amine acid ratio of 1:1 and a concentration of 60wt%. After starting the preparation, offline sampling is performed every 1 hour, and the sampled nylon salt solution is diluted to 10wt% and cooled to 25°C to test the amine acid ratio, which is compared and monitored, and the results are shown in Table 1.

[0082] Comparative Example 2

[0083] Comparative Example 2 and Example 2 only differ in that the hexamethylenediamine in the third diamine feeding pipe is fed through the bypass pipeline provided with a flowmeter and an adjusting valve to control the flow rate of the salt solution at 50kg / h, and an equal proportion of pure water is added to dilute the solution from 60wt% to about 10wt%, and then the temperature of the solution is controlled at 25±1°C by the heat exchanger. The pH of the diluted and cooled salt solution is monitored online after the heat exchanger, and the flow rate of the hexamethylenediamine in the third diamine feeding pipe is adjusted according to the laboratory model feedback. After starting the preparation, offline sampling is performed every 1 hour, and the sampled salt solution is diluted to 10wt% and cooled to 25°C to test the amine acid ratio, which is compared and monitored, and the results are shown in Table 1.

[0084] Table 1

[0085] As can be seen from Table 1, the online near-infrared monitoring device is used to adjust the hexamethylenediamine in the third diamine feeding pipe to prepare the expected amine acid ratio, and the fluctuation is small. The pH is monitored online, and the data fluctuation is large due to the influence of uncontrollable factors such as fluctuation of dilution concentration, detection temperature, etc. The deviated amine acid ratio is not conducive to the subsequent polymerization, especially the control of the end group of the finished product, which has a great influence on the downstream application, such as the spinning field.

[0086] Compared with the prior art, the application has the following beneficial effects: first, the aliphatic dicarboxylic acid is directly fed in a weight measurement manner, and the feeding amount can be accurately measured; second, when the aliphatic dicarboxylic acid suspension is prepared by using the suspension preparation device, the high-speed shearing pump can generate a micro-negative pressure when circulating the material, so that the high-speed shearing pump forms a vacuum suction state, so that the aliphatic dicarboxylic acid is rapidly and completely dispersed into the suspension, and at the same time, the high-speed shearing pump can form water mist; further, when the aliphatic dicarboxylic acid suspension is prepared by using the suspension preparation device, the agglomeration between the aliphatic dicarboxylic acid powders can be avoided, and the water can be quickly contacted with the aliphatic dicarboxylic acid powders to form an ideal and uniform dispersion solution; third, the on-line near-infrared monitoring device is used to monitor the molar ratio of the dicarboxylic acid and the diamine in the nylon salt solution, which avoids the concentration problem caused by sampling and adding additional water dilution, and at the same time, the on-line near-infrared monitoring device can stably measure at a temperature of ±10℃. Therefore, the molar ratio of the dicarboxylic acid and the diamine in the nylon salt solution obtained by using the preparation device and the preparation process is more accurate.

[0087] The technical features of the above-mentioned embodiments can be combined arbitrarily, and in order to make the description simple, all possible combinations of the technical features in the above-mentioned embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0088] The above-mentioned embodiments only express several implementation manners of the application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which are all within the protection scope of the application. Therefore, the protection scope of the patent of the application should be subject to the appended claims.

Claims

1. An apparatus for preparing a nylon salt solution, characterized by comprising: The application relates to a preparation device for preparing nylon salt, which comprises a suspension preparation device, a first salting kettle, a second salting kettle and a suspension storage tank. The suspension preparation device comprises feeding equipment, continuous feeding equipment, a high-speed shearing pump and a preparation kettle provided with a water inlet pipe, and the high-speed shearing pump and the preparation kettle are connected through two communication pipes; the feeding equipment is used for feeding aliphatic dicarboxylic acid; the continuous feeding equipment is used for feeding aliphatic dicarboxylic acid into the high-speed shearing pump; and aliphatic dicarboxylic acid and water can be circulated and mixed in the high-speed shearing pump and the preparation kettle to prepare aliphatic dicarboxylic acid suspension. The first salting kettle is connected with the suspension preparation device and has a first diamine feeding pipe for preparing a primary nylon salt solution by mixing the aliphatic dicarboxylic acid suspension with diamine. The second salting kettle is connected with the first salting kettle and has a second diamine feeding pipe and a third diamine feeding pipe for preparing a nylon salt solution by mixing the primary nylon salt solution with diamine; the second salting kettle further has a second salting kettle circulation pipe, and an on-line near-infrared monitoring device is arranged on the second salting kettle circulation pipe to monitor the molar ratio of the aliphatic dicarboxylic acid and the diamine in the nylon salt solution and control the feeding amount of the diamine in the third diamine feeding pipe according to the monitoring result.

2. The device for preparing a solution of a nylon salt according to claim 1, wherein, The preparation device further comprises a suspension storage tank connected with the suspension preparation device for storing the aliphatic dicarboxylic acid suspension prepared by the suspension preparation device; the first salting kettle is connected with the suspension storage tank; and / or the preparation device further comprises a primary nylon salt storage tank connected with the first salting kettle for storing the primary nylon salt solution prepared by the first salting kettle; the second salting kettle is connected with the primary nylon salt storage tank; and / or the preparation device further comprises a nylon salt storage tank connected with the second salting kettle for storing the nylon salt solution prepared by the second salting kettle.

3. The device for preparing a solution of a nylon salt according to claim 2, wherein, The number of the suspension preparation devices is one or more than two, and each suspension preparation device is connected with the suspension storage tank.

4. The device for preparing a solution of a nylon salt according to claim 2, wherein, The suspension storage tank is provided with a suspension storage tank circulation pipe for circulating the aliphatic dicarboxylic acid suspension in the suspension storage tank; and / or the primary nylon salt storage tank is provided with a primary nylon salt storage tank circulation pipe for circulating the primary nylon salt solution in the primary nylon salt storage tank; and / or the first salting kettle is provided with a first salting kettle circulation pipe for circulating the primary nylon salt solution in the first salting kettle.

5. The device for preparing a solution of a nylon salt according to claim 4, wherein, An on-line densimeter is arranged on the suspension storage tank circulation pipe to monitor and feedback the concentration change of the aliphatic dicarboxylic acid suspension in real time.

6. The device for preparing a solution of a nylon salt according to claim 4, characterized in that, A first heat exchanger is arranged on the circulation pipe of the first salting kettle; and / or a second heat exchanger is arranged on the circulation pipe of the second salting kettle.

7. The device for preparing a solution of a nylon salt according to claim 1, wherein, The on-line near-infrared monitoring device is a non-contact on-line near-infrared monitoring device.

8. A process for the formulation of a nylon salt solution characterized by, A preparation device of the nylon salt solution as claimed in any one of claims 1-7, comprising the following steps: water is introduced into the preparation kettle through a water inlet pipe, and a high-speed shearing pump is started to circulate water between the preparation kettle and the high-speed shearing pump; aliphatic dicarboxylic acid is introduced through a feeding device and mixed with water in the high-speed shearing pump and circulated between the high-speed shearing pump and the preparation kettle to prepare an aliphatic dicarboxylic acid suspension; the aliphatic dicarboxylic acid suspension is transferred to a first salting kettle, and diamine is added to the first salting kettle through a first diamine feeding pipe to prepare a primary nylon salt solution; the primary nylon salt solution is transferred to a second salting kettle, and the diamine is added to the second salting kettle through a second diamine feeding pipe and a third diamine feeding pipe to prepare a nylon salt solution, wherein the amount of diamine fed through the third diamine feeding pipe is controlled by an online near-infrared monitoring device on the circulating pipe of the second salting kettle.

9. The process for the formulation of a nylon salt solution according to claim 8, wherein, the aliphatic dicarboxylic acid suspension prepared by the suspension preparation device is transferred to a suspension storage tank, and then the aliphatic dicarboxylic acid suspension in the suspension storage tank is transferred to a first salting kettle; and / or, the primary nylon salt solution prepared by the first salting kettle is transferred to a primary nylon salt storage tank, and then the primary nylon salt solution in the primary nylon salt storage tank is transferred to a second salting kettle; and / or, the nylon salt solution prepared by the second salting kettle is transferred to a nylon salt storage tank.

10. The process for the formulation of a nylon salt solution according to claim 8 or 9, wherein, The preparation process also satisfies at least one of the following conditions: (1) the concentration of the aliphatic dicarboxylic acid suspension is 35wt%-52wt%; (2) the molar ratio of dicarboxylic acid to diamine in the primary nylon salt solution is 1.5:1-3:1, and the concentration is 40wt%-62wt%; (3) the concentration of the nylon salt solution is 50wt%-65wt%.

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