Nylon salt synthesis mass transfer strengthening device
By designing a specific asymmetric arc-shaped stirrer, the problems of high temperature, long time, easy yellowing, small particle size and high energy consumption in the preparation of nylon salt are solved, and the synthesis of high-quality nylon salt is achieved, with good industrial application prospects.
Patent Information
- Application Number
- CN202411747116.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-02
- Publication Date
- 2025-02-28
AI Technical Summary
In the prior art, the preparation of nylon salts has problems such as excessive salt formation temperature, long salt formation time, easy yellowing color, small particle size and high energy consumption, resulting in poor quality of nylon products and limiting its industrial application.
A stirrer for strengthening the mass transfer of nylon salt synthesis was designed. The asymmetric arc stirrer made of 316L material was used. Combined with the bottom end of the stirrer with an arc structure, the shearing effect on the fluid is enhanced, thereby improving the mass transfer process of the reaction liquid.
Through the use of this stirring device, the quality of nylon salt is significantly improved, the salt formation temperature and time is reduced, the color and particle size of the product are improved, and the energy consumption is lower, and it has good industrial application potential.
Smart Images
Figure CN119524774A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of nylon, in particular to a synthetic mass transfer enhancement device for nylon salt. Background Art
[0002] Polyamide, referred to as PA, commonly known as nylon, is a general term for polymers containing amide groups (-NH-C=O) in the repeating units of the main chain of the macromolecule. It can be obtained by evaporating a salt solution prepared from aliphatic dicarboxylic acids and diamines and then heating them to polymerize them, such as nylon 612.
[0003] As the precursor of nylon polymer, nylon salt plays a vital role in ensuring the quality of nylon products. However, under the current technical level, there are some problems in the preparation of nylon salt: the salt-forming temperature is too high, the salt-forming time is long, the color is prone to yellowing, the particle size is small, and the energy consumption is high. These problems have seriously restricted the development and industrial application of nylon products.
[0004] The industry generally uses the intermittent salt process. The particle size distribution of dodecanedioic acid powder is relatively wide, resulting in a relatively large bulk density, such as 0.6-0.7g / cm3. The general stirring method has major defects and is not conducive to obtaining high-quality salt solutions. Therefore, it is of great significance to change the stirring device to enhance mass transfer for the production of high-quality nylon salt. Summary of the invention
[0005] The object of the present invention is to provide a scheme for strengthening mass transfer in nylon salt synthesis, which can effectively improve the quality of nylon salt.
[0006] In order to achieve the above-mentioned purpose, the present invention provides the following device design features, test process and test device scheme: A stirrer for enhancing mass transfer in nylon salt synthesis, comprising the following features: Feature 1: The stirring paddle is made of 316L material; Feature 2: The stirring paddle is an asymmetric arc-shaped structure. The support rod is located at the center of the stirring paddle. The angle of the left part of the stirring paddle is 45° to 60°, and the angle of the right part of the stirring paddle is 15° to 30°. There is a notch in the left part of the stirring paddle, which is circular in shape. The notch is mainly used to balance the mass of the left and right sides of the stirring paddle so that the center of gravity of the stirring paddle is located on the support rod or the extension line of the support rod. Feature 3: The bottom of the agitator is an arc-shaped structure with an angle of 60° to 75°. The maximum curvature is located at 40° to 45°, and the curvature at the maximum curvature is 4.5 / r to 5 / r, where r is the radius of the blade.
[0007] Feature 4: The stirring paddle is at the bottom of the reactor, and the lowest point is 1 cm away from the reactor.
[0008] Feature 5: When the stirring paddle rotates, the notch in the paddle effectively enhances the shearing effect on the fluid and the mass transfer process of the reaction liquid.
[0009] A nylon 612 salt synthesis process for verification comprises the following steps: Step (1): adding a certain amount of dodecanedioic acid to anhydrous ethanol, and stirring thoroughly at room temperature to form a dodecanedioic acid ethanol solution; slowly dripping hexamethylenediamine into the dodecanedioic acid ethanol solution to react, and obtaining a nylon salt solution to be purified.
[0010] Step (2): placing the nylon salt solution to be purified under heating conditions and stirring, adding a certain amount of seed crystals after stirring for a period of time, and continuing the reaction for a period of time.
[0011] Step (3): After the salt-forming reaction is completed, solid-liquid separation is performed by suction filtration, followed by ethanol washing and vacuum drying to obtain nylon 612 salt solid.
[0012] 2. In the step (2), 0.001 to 0.010 g of seed crystals are added to every 10 mL of salt solution (to increase the crystallization rate).
[0013] 3. In the step (2), the reaction is continued for 2 to 4 hours after the seed crystals are added.
[0014] 4. Wherein, the heating method in step (2) is a water bath at a temperature of 60 to 70°C.
[0015] 5. In the step (1), 5 ml of anhydrous ethanol is added to each gram of dodecanedioic acid.
[0016] 6. Wherein, in step (1), the molar ratio of hexamethylenediamine to dodecanedioic acid is 1.0 to 1.1.
[0017] 7. Wherein, the reaction time in step (1) at room temperature is 20 to 60 minutes.
[0018] 8. Wherein, the stirring time in the water bath condition in the step (2) is 120 to 240 minutes.
[0019] 9. Wherein, the stirring rate in step (2) at room temperature is 200 to 400 r / min.
[0020] 10. Wherein, the drying condition in step (3) is drying in a vacuum oven at 60-80°C for 6-15h.
[0021] A stirring device for enhancing mass transfer in nylon salt synthesis includes the following equipment: A reaction liquid preparation device, the reaction liquid preparation device comprises a pre-dissolving device, a feeding device and a stirring tank provided with nitrogen protection which are connected in sequence, and the pre-dissolving device is used for preparing a solution of aliphatic dicarboxylic acid and hexamethylenediamine, the feeding device is connected to the reactor through a pipeline, and the pipeline inlet is located above the reactor, and the reaction liquid preparation device is used for dissolving the reaction materials; A stirring device, under which the aliphatic dicarboxylic acid and hexamethylenediamine solution can react in the reactor to generate a high-quality nylon salt solution; specifically including: Figure 2 The following parts are shown: 1. Mixing chamber; 2. Feed connection port; 3. Motor; 4. Support; 5. Discharge port; 6. Nitrogen; 7. Gas pipeline; 8. Secondary pressure reducing valve; A nylon salt synthesis reactor, in which aliphatic dicarboxylic acid and hexamethylenediamine solution can undergo a chemical reaction to generate a high-quality nylon salt product; A nylon salt separation device, in which nylon salt and ethanol solution can be separated into solid and liquid, and purified to obtain nylon salt solid; In one embodiment, the preparation device further includes a reaction liquid storage tank, which is connected to the nylon salt synthesis reactor and is used to store the aliphatic dicarboxylic acid suspension prepared by the reaction liquid preparation device. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 The diagram is a schematic diagram of the structure of the stirring paddle of the present invention, wherein the left diagram is a schematic diagram of the main view structure, and the right diagram is a schematic diagram of the top view structure; Figure 2 The schematic diagram of the structure of the stirring device for enhancing the mass transfer of nylon salt synthesis of the present invention, wherein the left figure is a schematic diagram of the overall structure, and the right figure is a schematic diagram of the internal cross-sectional structure; Figure 3 Schematic diagram of the stirring device for implementation and comparison of the present invention; Figure 4 This is a schematic diagram of the stirring device for testing the enhanced mass transfer of nylon salt synthesis according to the present invention, in which: 11, dodecanedioic acid preparation device 12, hexamethylenediamine preparation device 13, nylon salt synthesis reactor 14, nylon salt separation device DETAILED DESCRIPTION
[0023] For ease of understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention 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 understanding of the disclosure of the present invention more thorough and comprehensive.
[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific implementation methods or embodiments and are not intended to limit the present invention. Example 1
[0025] Weigh 20g of hexamethylenediamine and dissolve it in 100ml of anhydrous ethanol. Stir it thoroughly under stirring in a water bath at 25°C to form an ethanol solution of hexamethylenediamine. Weigh 40g of dodecanedioic acid and dissolve it in 200ml of anhydrous ethanol. Stir it thoroughly under stirring in a water bath at 25°C to form an ethanol solution of hexamethylenediamine. Slowly drop the ethanol solution of dodecanedioic acid into the ethanol solution of hexamethylenediamine and use the stirring device of the present invention to carry out a mixing reaction. The reaction temperature is 60°C. After reacting for 2h, the nylon salt solution is placed at room temperature for stirring at a stirring rate of 400r / min. After reacting at room temperature for 0.5h, add 0.005g of seed (dodecanedioic acid) and continue stirring for 1h. After the salt-forming reaction is completed, solid-liquid separation is carried out by suction filtration, the solid is washed with anhydrous ethanol, and the obtained nylon salt solid is placed in a vacuum oven at 70°C and dried for 12 hours.
[0026] The product obtained after drying was weighed and its yield was calculated, which was 99%. The concentration of the reactants was tested. The results showed that the purity of the obtained nylon salt was high. Example 2
[0027] Weigh 40g of hexamethylenediamine and dissolve it in 200ml of anhydrous ethanol, stir it thoroughly under stirring in a water bath at 25°C to form an ethanol solution of hexamethylenediamine. Weigh 80g of dodecanedioic acid and dissolve it in 400ml of anhydrous ethanol, stir it thoroughly under stirring in a water bath at 25°C to form an ethanol solution of hexamethylenediamine. Slowly add the ethanol solution of dodecanedioic acid dropwise to the ethanol solution of hexamethylenediamine and use the stirring device of the present invention to carry out a mixing reaction, the reaction temperature is 60°C, after reacting for 2h, place the nylon salt solution at room temperature for stirring, and the stirring rate is 400r / min. After reacting at room temperature for 0.5h, add 0.005g of seed (dodecanedioic acid) and continue stirring for 1h. After the salt-forming reaction is completed, solid-liquid separation is carried out by suction filtration, the solid is washed with anhydrous ethanol, and the obtained nylon salt solid is placed in a vacuum oven at 70°C and dried for 12 hours.
[0028] The product obtained after drying was weighed and its yield was calculated, which was 98%. Example 3
[0029] Weigh 80g of hexamethylenediamine and dissolve it in 400ml of anhydrous ethanol, stir it thoroughly under stirring in a water bath at 25°C to form an ethanol solution of hexamethylenediamine. Weigh 160g of dodecanedioic acid and dissolve it in 800ml of anhydrous ethanol, stir it thoroughly under stirring in a water bath at 25°C to form an ethanol solution of hexamethylenediamine. Slowly add the ethanol solution of dodecanedioic acid dropwise to the ethanol solution of hexamethylenediamine and use the stirring device of the present invention to carry out a mixing reaction. After reacting for 2h, place the nylon salt solution at room temperature and stir it at a stirring rate of 400r / min. After reacting at room temperature for 0.5h, add 0.005g of seed (dodecanedioic acid) and continue stirring for 1h. After the salt-forming reaction is completed, solid-liquid separation is carried out by suction filtration, the solid is washed with anhydrous ethanol, and the obtained nylon salt solid is placed in a vacuum oven at 70°C and dried for 12 hours.
[0030] The product obtained after drying was weighed and its yield was calculated, which was 98%.
[0031] The above embodiments show that the device is still stable after being enlarged.
[0032] Comparative Example 1 Except for the use of a conventional two-impeller stirring device during the experiment, everything else was the same as Example 1: The results showed that the yield of nylon salt was 91%, wherein the obtained nylon salt contained a higher content of reactants and its quality was lower than that of the nylon salt obtained in the implementation case.
[0033] Comparative Example 2 Except for the use of a conventional three-impeller stirring device during the experiment, everything else was the same as Example 1: The results showed that the yield of nylon salt was 92%, wherein the obtained nylon salt contained a higher content of reactants and its quality was lower than that of the nylon salt obtained in the implementation case.
[0034] Comparative Example 3 The other steps are the same as those in Example 1, except that the stirring device is changed to a four-impeller stirring device. It is found that the yield of nylon salt is 94%, wherein the obtained nylon salt contains a higher content of reactants, and its quality is lower than that of the nylon salt obtained in the implementation case.
[0035] In summary, the present invention utilizes a change in the stirring device to improve mass transfer in the process of synthesizing nylon salt. The device not only has low energy consumption, but also effectively obtains high-purity nylon 612 salt crystals with good crystal color and short salt formation time, and has good development prospects and potential for industrial application.
[0036] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.
Claims
1. An agitator for enhancing mass transfer in nylon salt synthesis, comprising the following features: Feature 1: The stirring paddle is made of 316L material; Feature 2: The stirring paddle is an asymmetric arc-shaped structure. The support rod is located at the center of the stirring paddle. The angle of the left part of the stirring paddle is 45° to 60°, and the angle of the right part of the stirring paddle is 15° to 30°. There is a notch in the left part of the stirring paddle, which is circular in shape. The notch is mainly used to balance the mass of the left and right sides of the stirring paddle so that the center of gravity of the stirring paddle is located on the support rod or the extension line of the support rod. Feature 3: The bottom of the agitator is an arc-shaped structure with an angle of 60° to 75°; the maximum curvature is located at 40° to 45°, and the curvature at the maximum curvature is 4.5 / r to 5 / r, where r is the radius of the blade; Feature 4: The stirring paddle is at the bottom of the reactor, and the lowest point is 1 cm away from the reactor; Feature 5: When the stirring paddle rotates, the notch in the paddle effectively enhances the shearing effect on the fluid and the mass transfer process of the reaction liquid.
2. A nylon 612 salt synthesis process for verification, comprising the following steps: Step (1): adding a certain amount of dodecanedioic acid to anhydrous ethanol, stirring well at room temperature to form a dodecanedioic acid ethanol solution; slowly dripping hexamethylenediamine into the dodecanedioic acid ethanol solution to react, to obtain a nylon salt solution to be purified; Step (2): placing the nylon salt solution to be purified under heating conditions and stirring, adding a certain amount of seed crystals after stirring for a period of time, and continuing the reaction for a period of time; Step (3): After the salt-forming reaction is completed, solid-liquid separation is performed by suction filtration, followed by ethanol washing and vacuum drying to obtain nylon 612 salt solid.
3. A stirring device for enhancing mass transfer in nylon salt synthesis, characterized in that: include: A reaction liquid preparation device, the reaction liquid preparation device comprises a pre-dissolving device, a feeding device and a stirring tank provided with nitrogen protection which are connected in sequence, and the pre-dissolving device is used for preparing a solution of aliphatic dicarboxylic acid and hexamethylenediamine, the feeding device is connected to the reactor through a pipeline, and the pipeline inlet is located above the reactor, and the stirring device is used for dissolving the reaction materials; A stirring device, under which the aliphatic dicarboxylic acid and hexamethylenediamine solution can react in the reactor to generate a high-quality nylon salt solution; A nylon salt synthesis reactor, in which aliphatic dicarboxylic acid and hexamethylenediamine solution can undergo a chemical reaction to produce a high-quality nylon salt product; A nylon salt separation device is provided, in which nylon salt and ethanol solution can be separated into solid and liquid, and purified to obtain nylon salt solid.
4. A stirring device for enhancing mass transfer in nylon salt synthesis according to claim 3, characterized in that: The preparation device also includes a reaction liquid storage tank, which is connected to the nylon salt synthesis reactor and is used to store the aliphatic dicarboxylic acid suspension prepared by the reaction liquid preparation equipment.
5. The stirring device for enhancing mass transfer in nylon salt synthesis according to claim 3, characterized in that: The preparation device also includes a stirring tank, which is connected to the main body of the reaction liquid preparation equipment and is used to produce the aliphatic dicarboxylic acid solution and hexamethylenediamine solution required for the reaction.