Method and system for continuously preparing long-carbon-chain nylon salt, obtained long-carbon-chain nylon salt and application

Abstract

The invention provides a method and a system for continuously preparing long-carbon-chain nylon salt, the obtained long-carbon-chain nylon salt and application of the long-carbon-chain nylon salt. The preparation method comprises the following steps: rapidly mixing and reacting diamine and binary acid solutions, neutralizing and adjusting the pH value, filtering, washing and purging in a continuous pressurizing rotary drum filter, and finally drying and removing a solvent to obtain the long carbon chain nylon salt. The system comprises a binary acid dissolving kettle, a diamine dissolving kettle, a mixer, a continuous salifying reactor, a continuous pressurizing rotary drum filter and a continuous tower type dryer. The method provided by the invention can realize continuous production of high-efficiency, low-energy-consumption and high-quality nylon salt, has higher production efficiency and smaller size of required equipment, and is suitable for preparing various nylon salts produced by a solvent crystallization method.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and more particularly to a method and system for continuously preparing a long carbon chain nylon salt, and the obtained long carbon chain nylon salt and its application. Background Art

[0002] Long carbon chain nylon, such as nylon 1212, has the characteristics of low density, low water absorption, good dimensional stability, excellent chemical resistance, corrosion resistance, wear resistance, fatigue resistance and good low-temperature impact resistance. It is mainly used in the automotive, electrical, machinery and other industries, such as coil skeletons, insulation layers of wires and cables, fuel oil pipelines, hydraulic system pipelines, conduits, etc.

[0003] In general, in order to prepare long-chain nylon with an equimolar ratio of monomers, it is necessary to prepare long-chain nylon salt first. The usual method for preparing long-chain nylon salt is to add diamine and dibasic acid solution to an intermittent reactor to react for a period of time, and then cool and centrifuge to obtain nylon salt. However, this method uses an intermittent reactor as a neutralization reactor, which has low mixing efficiency and takes a long time; and it needs to go through processes such as cooling and heating and drying, which requires high energy consumption; centrifugal separation has a lot of residual solvent, which may contain unreacted monomers.

[0004] The existing technology for producing long carbon chain nylon salts usually adopts an intermittent method. Patent CN113698288A discloses a continuous preparation technology for nylon salts, which adopts a method of directly adding materials to a reactor for reaction and subsequently removing the solvent by a spray drying method. However, this method is only applicable to the production of soluble nylon salts, and the direct mixing reaction effect is poor, which may lead to incomplete reaction. At the same time, the spray drying method has high requirements for raw materials, and slurry cannot be dried by this method.

[0005] Therefore, it is necessary to study a continuous preparation method of long carbon chain nylon salt, which can not only ensure the complete reaction of diamine and diacid, but also prepare long carbon chain nylon salt with very low solubility in solvent, and the drying method can be used for slurry. Summary of the invention

[0006] In order to solve the technical problems existing in the prior art, the present invention provides a method and system for continuously preparing a long carbon chain nylon salt, and the obtained long carbon chain nylon salt and application.

[0007] In order to overcome the problems of long reaction time, large equipment size, low production efficiency, insufficient reaction, solvent and monomer residues in the prior art for preparing long carbon chain nylon salt, the present invention proposes a method for continuously preparing long carbon chain nylon salt.

[0008] In the prior art, the preparation of long-chain nylon salts in a reaction kettle is generally carried out intermittently. For example, during stirring reaction in a neutralization kettle, after the reaction is completed, it is then concentrated and separated. As a neutralization reactor, the reaction kettle has problems such as low mixing efficiency, high energy consumption, more solvent residues, and unreacted monomers. The present invention adopts a continuous reaction device and method (such as a mixer, a salt-forming reactor, a rotary drum filter, a dryer, etc.), without going through the cooling-heating process, realizing the continuous production of high-efficiency, low-energy-consumption, and high-quality nylon salts, with higher production efficiency and smaller required equipment size.

[0009] In the present invention, by using a mixer to promote the mixing of a dibasic acid and a diamine and rapid heat removal, the reaction can proceed rapidly and stably, avoiding the situation of too high reaction temperature or incomplete reaction, and can improve production efficiency and reduce the volume of the reaction equipment; subsequently, continuous filtration and drying are carried out through a continuous pressure rotary drum filter, and the generated solid nylon salt can be separated, which is suitable for preparing various nylon salts produced by the solvent crystallization method.

[0010] One of the purposes of the present invention is to provide a method for continuously preparing long-chain nylon salts, including:

[0011] After the solutions of the diamine and the dibasic acid are rapidly mixed and reacted, the pH is neutralized and adjusted, and then filtered, washed, and purged in a continuous pressure rotary drum filter, and finally dried to remove the solvent to obtain the long-chain nylon salt.

[0012] In a preferred embodiment of the present invention,

[0013] The method includes the following steps:

[0014] (1) Dissolve the dibasic acid with solvent A and the diamine with solvent B by heating respectively;

[0015] (2) Continuously and continuously add the diamine solution and the dibasic acid solution obtained in step (1) into a mixer for rapid mixing and reaction to obtain a nylon salt slurry;

[0016] (3) Add the nylon salt slurry obtained in step (2) into a continuous salt-forming reactor for neutralization reaction, stabilization, and pH adjustment;

[0017] (4) Add the nylon salt slurry with adjusted pH obtained in step (3) into a continuous pressure rotary drum filter for filtration, washing, and purging to obtain wet nylon salt;

[0018] (5) Add the wet nylon salt obtained in step (4) into a continuous dryer for drying to remove the solvent to obtain the long-chain nylon salt.

[0019] In a preferred embodiment of the present invention,

[0020] In step (1),

[0021] The dibasic acid is at least one of dibasic acids having 5 to 20 carbon atoms, preferably at least one of dibasic acids having 6 to 14 carbon atoms; for example, dibasic acids of C6, C7, C8, C9, C10, C11, C12, C13, and C14;

[0022] The diamine is at least one of diamines having 5 to 20 carbon atoms, preferably at least one of diamines having 6 to 14 carbon atoms; for example, diamines of C6, C7, C8, C9, C10, C11, C12, C13, and C14;

[0023] The solvent A and the solvent B are each independently selected from at least one of methanol, ethanol, and propanol;

[0024] The weight ratio of the dibasic acid to the solvent A is 1:(2 to 10);

[0025] When the dibasic acid is mixed with the solvent A, it is heated to 50 to 95 °C and maintained for 10 to 60 min;

[0026] The weight ratio of the diamine to the solvent B is 1:(1 to 6);

[0027] When the diamine is mixed with the solvent B, it is heated to 40 to 90 °C and maintained for 10 to 60 min.

[0028] In a preferred embodiment of the present invention,

[0029] In step (2),

[0030] The molar ratio of the dibasic acid to the diamine is 1:(0.99 to 1.05), preferably 1:(0.99 to 1.02); and / or,

[0031] The mixer is a static mixer or a dynamic mixer, and the static mixer is preferably of the SV type, SK type, or SL type;

[0032] The temperature in the mixer is 60 to 80 °C.

[0033] The mixing time is 1 to 600 s. The mixing time refers to the residence time of the fluid in the mixer and is equal to the fluid volume divided by the fluid flow rate.

[0034] The nylon salt formation reaction is a strongly exothermic reaction, and a solid is formed after the liquids are mixed. The mixer needs to have good mixing effect and heat removal effect.

[0035] In a preferred embodiment of the present invention,

[0036] In step (3),

[0037] The continuous salt formation reactor is a continuous stirred tank reactor; and / or,

[0038] The neutralization reaction is carried out at a stable temperature of 60 to 80 °C; and / or,

[0039] The neutralization reaction is carried out for a stable time of 0.1 to 1.0 h; and / or,

[0040] Adjust the pH to 6.5 to 7.5.

[0041] In a preferred embodiment of the present invention,

[0042] In step (4),

[0043] The continuous pressure drum filter includes a slurry feeding and filtering area, a filter cake washing area, a filter cake drying area, and a filter cake discharging area;

[0044] A plurality of process sections are distributed in a circle inside the continuous pressure drum filter, and the sizes of the respective process sections are adjusted according to the actual process operation requirements; a plurality of filter cake grooves are provided in the drum, and the filter cake grooves are radially distributed around the central axis of the drum, and the included angle between the filter cake grooves is 10 to 20°, and filter cloths are covered on the filter cake grooves to achieve solid-liquid separation. The slurry is continuously input into the pressure drum filter (7) from the slurry feeding port (10) under the action of pump pressure and is filtered in the slurry feeding and filtering area (11). Filter cake grooves are provided in the drum, and the filtrate passes through the filter cloth and then enters the internal filtrate pipe and is discharged from the filtrate outlet (15). The filter cake enters the washing area (12), and one-stage or multi-stage filter cake washing can be set. The washing liquid passes through the filter cloth and then enters the internal filtrate pipe and is discharged from the filtrate outlet (15); the filter cake after washing is dried in the drying area (13) by blowing with compressed nitrogen; discharging is carried out in the discharging area (14) under normal pressure and is realized by a scraper and gas backwashing. After discharging, the filter cloth is rinsed and regenerated, and the filter cake is obtained from the filter cake outlet (16).

[0045] The continuous pressure drum filter can continuously separate most of the nylon salt and the solvent in the subsequent nylon salt slurry, ensuring the continuity of production.

[0046] The filtration pressure is 0.1 to 1.0 MPa; and / or,

[0047] The filtration temperature is 20 to 80 °C.

[0048] In a preferred embodiment of the present invention,

[0049] In step (5),

[0050] The continuous dryer is a continuous tower dryer or a continuous rake dryer; preferably vacuum drying, and further preferably,

[0051] The drying temperature is 60 to 100 °C; and / or,

[0052] The drying time is 0.5 to 4.0 h; and / or,

[0053] The vacuum pressure is 0.01 to 10 kPa.

[0054] The second object of the present invention is to provide a system for continuously preparing long-chain nylon salt, including a dibasic acid dissolving kettle, a diamine dissolving kettle, a mixer, a continuous salifying reactor, a continuous pressure drum filter and a continuous tower dryer; the dibasic acid dissolving kettle and the diamine dissolving kettle are respectively connected to the mixer through metering pumps, and the mixer, the continuous salifying reactor, the continuous pressure drum filter and the continuous tower dryer are connected in sequence;

[0055] Preferably, the mixer and the continuous salifying reactor have good heat dissipation effect, and can make the temperature rise not exceed 5°C after the mixing reaction of dibasic acid and diamine;

[0056] The continuous pressure drum filter includes a slurry feeding and filtering area, a filter cake washing area, a filter cake drying area and a filter cake discharging area.

[0057] The third object of the present invention is to provide a long-chain nylon salt obtained by the above method or system; preferably, the particle size of the long-chain nylon salt is 10 to 100 μm, and the solvent content is less than or equal to 0.5 wt%.

[0058] The fourth object of the present invention is to provide an application of the continuous preparation of long-chain nylon salt in the field of long-chain nylon.

[0059] Compared with the prior art, the beneficial effects of the present invention:

[0060] In the prior art, long-chain nylon salt is generally prepared intermittently in a reaction kettle. As a neutralization reactor, the reaction kettle has problems such as low mixing efficiency, high energy consumption, more solvent residues, and unreacted monomers. The present invention adopts a continuous reaction device and method (mixer, salifying reactor, drum filter, dryer, etc.), without going through the cooling-heating process, and realizes the continuous production of high-efficiency, low-energy-consumption and high-quality nylon salt.

[0061] The present invention uses a mixer to promote the mixing of dibasic acid and diamine and rapid heat dissipation, so that the reaction can proceed quickly and stably, avoiding the situation of too high reaction temperature or incomplete reaction, and can improve production efficiency and reduce the volume of reaction equipment; subsequently, continuous filtration and drying are carried out through a continuous pressure drum filter, which can separate the generated solid nylon salt and is suitable for preparing various nylon salts produced by the solvent crystallization method. Description of the Drawings

[0062] Figure 1 It is a schematic diagram of the system for continuously preparing long-chain nylon salt of the present invention;

[0063] Among them, 1 - dibasic acid dissolving kettle; 2 - diamine dissolving kettle; 3 - mixer; 4 - continuous salifying reactor; 5 - slurry pump; 6 - heat exchanger; 7 - continuous pressure drum filter; 8 - continuous tower dryer; 9 - nylon salt solid storage tank;

[0064] Figure 2 It is a schematic structural diagram of the continuous pressure drum filter of the present invention;

[0065] Among them, 10 - slurry feed inlet, 11 - slurry feeding and filtering area, 12 - washing area, 13 - drying area, 14 - discharging area, 15 - filtrate outlet, 16 - filter cake outlet. Specific embodiments

[0066] The present invention will be specifically described below in conjunction with specific drawings and embodiments. It is necessary to point out here that the following embodiments are only for further illustration of the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the protection scope of the present invention.

[0067] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0068] The raw materials used in the examples and comparative examples, if not specifically defined, are those disclosed in the prior art. For example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0069] Testing methods:

[0070] Particle size test: Using a laser particle size analyzer, with ethanol as the solvent, test the particle size distribution of nylon 1212 salt.

[0071] Solvent content: The solvent content of the sample is determined by thermogravimetric method.

[0072] Molar ratio: Titration analysis, titrate the amino group content of nylon salt with an acid standard solution, and titrate the carboxyl group content of nylon salt with a base standard solution.

[0073] Figure 1Schematic diagram of the system for continuously preparing long-chain nylon salt of the present invention; wherein, 1 - dibasic acid dissolving kettle; 2 - diamine dissolving kettle; 3 - mixer; 4 - continuous salifying reactor; 5 - slurry pump; 6 - heat exchanger; 7 - continuous pressure drum filter; 8 - continuous tower dryer; 9 - nylon salt solid storage tank.

[0074] The dibasic acid is heated and dissolved in the dibasic acid dissolving kettle (1) with solvent A, and the diamine is heated and dissolved in the diamine dissolving kettle (2) with solvent B. The obtained diamine solution and dibasic acid solution are continuously added to the mixer (3) for rapid mixing and reaction to obtain a nylon salt slurry, which is continuously added to the continuous salifying reactor for neutralization reaction, stabilization, and pH adjustment. The slurry pump (5) and heat exchanger (6) play the role of removing the reaction heat through external circulation and promoting uniform mixing. The slurry continuously enters the continuous pressure drum filter (7) for filtration, washing, and purging to obtain wet nylon salt. The obtained wet nylon salt is added to the continuous dryer (8) for drying to remove the solvent, and then the long-chain nylon salt is stored in the nylon salt solid storage tank (9).

[0075] Figure 2 Schematic diagram of the structure of the continuous pressure drum filter of the present invention; the continuous pressure drum filter includes a slurry feeding and filtering area, a filter cake washing area, a filter cake drying area, and a filter cake discharging area;

[0076] Wherein, 10 - slurry inlet, 11 - slurry feeding and filtering area, 12 - washing area, 13 - drying area, 14 - discharging area, 15 - filtrate outlet, 16 - filter cake outlet.

[0077] A plurality of process sections are distributed in a circle inside the continuous pressure drum filter, and the sizes of the respective process sections are adjusted according to the actual process operation requirements; a plurality of filter cake grooves are provided in the drum, and the filter cake grooves are radially distributed around the central axis of the drum, and the included angle between the filter cake grooves is 10 - 20°, and filter cloths are covered on the filter cake grooves to achieve solid-liquid separation.

[0078] The slurry is continuously input into the pressure drum filter (7) from the slurry inlet (10) under the action of pump pressure and is filtered in the slurry feeding and filtering area (11). Filter cake grooves are provided in the drum, and the filtrate passes through the filter cloth and enters the internal filtrate pipe and is discharged from the filtrate outlet (15). The filter cake enters the washing area (12), and one-stage or multi-stage filter cake washing can be set. The washing liquid passes through the filter cloth and enters the internal filtrate pipe and is discharged from the filtrate outlet (15); the washed filter cake is dried in the drying area (13) and purged with compressed nitrogen; discharging is carried out in the discharging area (14) under normal pressure and is achieved through a scraper and gas back blowing. After discharging, the filter cloth is rinsed and regenerated, and the filter cake is obtained from the filter cake outlet (16).

[0079] The continuous pressure drum filter can continuously separate most of the nylon salt and solvent in the subsequent nylon salt slurry, ensuring the continuity of production.

[0080]

Example 1

[0081] 1. Monomer dissolution: (1) 9000 g (39.1 mol) of dodecanedioic acid and 45000 g of ethanol are added to the diacid dissolution kettle, heated to 75 °C for dissolution, and maintained for 30 min; (2) 7914 g (39.5 mol) of dodecanediamine and 15828 g of ethanol are added to the diamine dissolution kettle, heated to 60 °C for dissolution, and maintained for 30 min;

[0082] 2. Monomer mixing: The obtained dodecanedioic acid solution is added to the SK type static mixer at a rate of 22.7 kg / h, and the dodecanediamine solution is added at a rate of 10.0 kg / h by a metering pump. The addition rate is such that the mixing molar ratio of dodecanedioic acid and dodecanediamine is 1:1.01. The residence time in the mixer is 10 s, and the temperature of the mixer is maintained at 75 °C by forced heat exchange;

[0083] 3. Neutralization reaction: The nylon salt slurry is added to the continuous salting reactor, with a residence time of 0.5 h, a temperature of 75 °C, and the pH of the slurry in the reactor is maintained at 7.0 by an on-line pH meter and a regulating pump;

[0084] 4. Nylon salt filtration: The nylon salt slurry from the salting reactor is added to a continuous pressure drum filter for filtration, solvent washing, nitrogen purging, and discharging processes. The filtration pressure is 0.3 MPa, and the filtration temperature is 75 °C;

[0085] 5. Nylon salt drying: The wet nylon salt is added to a continuous tower dryer for vacuum drying to obtain a dried nylon salt product. The temperature is 80 °C, the vacuum pressure is 1.0 kPa, and the drying time is 1.0 h.

[0086]

Example 2

[0087] 1. Monomer dissolution: (1) 9000 g (61.6 mol) of adipic acid and 45000 g of ethanol are added to the diacid dissolution kettle, heated to 75 °C for dissolution, and maintained for 30 min; (2) 7228 g (62.2 mol) of hexanediamine and 14456 g of ethanol are added to the diamine dissolution kettle, heated to 60 °C for dissolution, and maintained for 30 min;

[0088] 2. Monomer mixing: Use a metering pump to add adipic acid solution at a rate of 24.9 kg / h and hexamethylenediamine solution at a rate of 10.0 kg / h into an SK-type static mixer. The addition rate is based on ensuring that the mixing molar ratio of adipic acid to hexamethylenediamine is 1:1.01. The residence time in the mixer is 10 s, and the temperature of the mixer is maintained at 75 °C through forced heat exchange.

[0089] 3. The neutralization reaction steps are the same as those in Example 1.

[0090] 4. The nylon salt filtration steps are the same as those in Example 1.

[0091] 5. The nylon salt drying steps are the same as those in Example 1.

[0092]

Example 3

[0093] 1. Monomer dissolution: (1) Add 9000 g (39.1 mol) of dodecanedioic acid and 45000 g of ethanol into the diacid dissolution kettle, heat to 75 °C for dissolution, and maintain for 30 min; (2) Add 6806 g (39.5 mol) of sebac diamine and 13612 g of ethanol into the diamine dissolution kettle, heat to 60 °C for dissolution, and maintain for 30 min.

[0094] 2. Monomer mixing: Use a metering pump to add dodecanedioic acid solution at a rate of 26.4 kg / h and sebac diamine solution at a rate of 10.0 kg / h into an SK-type static mixer. The addition rate is based on ensuring that the mixing molar ratio of dodecanedioic acid to sebac diamine is 1:1.01. The residence time in the mixer is 10 s, and the temperature of the mixer is maintained at 75 °C through forced heat exchange.

[0095] 3. The neutralization reaction steps are the same as those in Example 1.

[0096] 4. The nylon salt filtration steps are the same as those in Example 1.

[0097] 5. Nylon salt drying: Add the wet nylon salt into a continuous rake dryer for vacuum drying to obtain a dried nylon salt product. The temperature is 80 °C, the vacuum pressure is 1.0 kPa, and the drying time is 1.0 h.

[0098]

Example 4

[0099] 1. Monomer dissolution: (1) Add 9000 g (34.8 mol) of tetradecanedioic acid and 45000 g of ethanol into the diacid dissolution kettle, heat to 75 °C for dissolution, and maintain for 30 min; (2) Add 8018 g (35.1 mol) of tetradecane diamine and 16036 g of ethanol into the diamine dissolution kettle, heat to 60 °C for dissolution, and maintain for 30 min.

[0100] 2. Monomer mixing: Using a metering pump, add the tetradecanedioic acid solution at a rate of 22.4 kg / h and the tetradecanediamine solution at a rate of 10.0 kg / h into the SK type static mixer. The addition rate is based on ensuring that the mixing molar ratio of tetradecanedioic acid to tetradecanediamine is 1:1.01. The residence time in the mixer is 10 s, and the temperature of the mixer is maintained at 75 °C through forced heat exchange.

[0101] 3. The neutralization reaction steps are the same as in Example 1.

[0102] 4. The nylon salt filtration steps are the same as in Example 1.

[0103] 5. Nylon salt drying: Add the wet nylon salt to a continuous rake dryer for vacuum drying to obtain a dried nylon salt product. The temperature is 80 °C, the vacuum pressure is 1.0 kPa, and the drying time is 1.0 h.

[0104]

Example 5

[0105] 1. Monomer dissolution: (1) Add 9000 g (39.1 mol) of dodecanedioic acid and 18000 g of methanol to the diacid dissolution kettle, heat to 50 °C for dissolution, and maintain for 50 min; (2) Add 7914 g (39.5 mol) of dodecanediamine and 7914 g of methanol to the diamine dissolution kettle, heat to 40 °C for dissolution, and maintain for 50 min.

[0106] 2. Monomer mixing: Using a metering pump, add the dodecanedioic acid solution at a rate of 17.1 kg / h and the dodecanediamine solution at a rate of 10.0 kg / h into the SK type static mixer. The addition rate is based on ensuring that the mixing molar ratio of dodecanedioic acid to dodecanediamine is 1:1.01. The residence time in the mixer is 10 s, and the temperature of the mixer is maintained at 75 °C through forced heat exchange.

[0107] 3. The neutralization reaction steps are the same as in Example 1.

[0108] 4. The nylon salt filtration steps are the same as in Example 1.

[0109] 5. The nylon salt drying steps are the same as in Example 1.

[0110]

Example 6

[0111] 1. Monomer dissolution: (1) Add 9000 g (39.1 mol) of dodecanedioic acid and 90000 g of propanol to the diacid dissolution kettle, heat to 95 °C for dissolution, and maintain for 10 min; (2) Add 7914 g (39.5 mol) of dodecanediamine and 47484 g of propanol to the diamine dissolution kettle, heat to 90 °C for dissolution, and maintain for 10 min.

[0112] 2. Monomer mixing: Use a metering pump to add dodecanedioic acid solution at a rate of 17.9 kg / h and dodecanediamine solution at a rate of 10.0 kg / h into an SK-type static mixer. The addition rate is based on ensuring that the mixing molar ratio of dodecanedioic acid to dodecanediamine is 1:1.01. The residence time in the mixer is 10 s, and the temperature of the mixer is maintained at 75 °C through forced heat exchange.

[0113] 3. The neutralization reaction steps are the same as those in Example 1.

[0114] 4. The nylon salt filtration steps are the same as those in Example 1.

[0115] 5. The nylon salt drying steps are the same as those in Example 1.

[0116]

Example 7

[0117] 1. The monomer dissolution steps are the same as those in Example 1.

[0118] 2. Monomer mixing: Use a metering pump to add dodecanedioic acid solution at a rate of 22.7 kg / h and dodecanediamine solution at a rate of 10.0 kg / h into an SK-type static mixer. The addition rate is based on ensuring that the mixing molar ratio of dodecanedioic acid to dodecanediamine is 1:1.01. The residence time in the mixer is 600 s, and the temperature of the mixer is maintained at 60 °C through forced heat exchange.

[0119] 3. Neutralization reaction: Add the nylon salt slurry into a continuous salification reactor, with a residence time of 1.0 h, maintain the temperature at 60 °C, and keep the pH of the slurry in the reactor at 6.5 through an on-line pH meter and a regulating pump.

[0120] 4. The nylon salt filtration steps are the same as those in Example 1.

[0121] 5. The nylon salt drying steps are the same as those in Example 1.

[0122]

Example 8

[0123] 1. The monomer dissolution steps are the same as those in Example 1.

[0124] 2. Monomer mixing: Use a metering pump to add dodecanedioic acid solution at a rate of 22.7 kg / h and dodecanediamine solution at a rate of 10.0 kg / h into an SK-type static mixer. The addition rate is based on ensuring that the mixing molar ratio of dodecanedioic acid to dodecanediamine is 1:1.01. The residence time in the mixer is 1 s, and the temperature of the mixer is maintained at 80 °C through forced heat exchange.

[0125] 3. Neutralization reaction: Add the nylon salt slurry into a continuous salification reactor, with a residence time of 0.1 h, maintain the temperature at 80 °C, and keep the pH of the slurry in the reactor at 7.5 through an on-line pH meter and a regulating pump.

[0126] 4. The nylon salt filtration step is the same as that in Example 1;

[0127] 5. The nylon salt drying step is the same as that in Example 1.

[0128]

Example 9

[0129] 1. The monomer dissolution step is the same as that in Example 1;

[0130] 2. The monomer mixing step is the same as that in Example 1;

[0131] 3. The neutralization reaction step is the same as that in Example 1;

[0132] 4. Nylon salt filtration: The nylon salt slurry from the salt-forming reactor is added to a continuous pressure rotary drum filter for filtration, solvent washing, nitrogen purging, and discharging processes. The filtration pressure is 0.1 MPa and the filtration temperature is 80 °C;

[0133] 5. Nylon salt drying: The wet nylon salt is added to a continuous tower dryer for vacuum drying to obtain a dried nylon salt product. The temperature is 100 °C, the vacuum pressure is 10 kPa, and the drying time is 0.5 h.

[0134]

Example 10

[0135] 1. The monomer dissolution step is the same as that in Example 1;

[0136] 2. The monomer mixing step is the same as that in Example 1;

[0137] 3. The neutralization reaction step is the same as that in Example 1;

[0138] 4. Nylon salt filtration: The nylon salt slurry from the salt-forming reactor is added to a continuous pressure rotary drum filter for filtration, solvent washing, nitrogen purging, and discharging processes. The filtration pressure is 1.0 MPa and the filtration temperature is 40 °C;

[0139] 5. Nylon salt drying: The wet nylon salt is added to a continuous tower dryer for vacuum drying to obtain a dried nylon salt product. The temperature is 60 °C, the vacuum pressure is 0.01 kPa, and the drying time is 4.0 h.

[0140]

Comparative Example 1

[0141] Nylon intermittent salification: (1) Add 9000 g (39.1 mol) of dodecanedioic acid and 45000 g of ethanol to the neutralization kettle, heat to 75 °C for dissolution, and hold for 30 minutes; (2) Add 7914 g (39.5 mol) of dodecanediamine and 15828 g of ethanol to the dissolution kettle, heat to 60 °C for dissolution, and hold for 30 minutes; (3) Pump all the dodecanediamine ethanol solution into the neutralization kettle through a feeding pump, with a feeding time of 1.0 h. React while stirring, control the reaction temperature at 75 °C, continue to react for 1.0 hour after feeding, adjust the pH of the reaction solution to 7.0 by adding dodecanedioic acid or dodecanediamine, cool the neutralization kettle to a temperature below 30 °C, filter the nylon salt solution through a filter, and dry it in an oven to obtain nylon 1212 salt solid.

[0142] The average particle size and solvent content of the nylon salts obtained in Examples 1 to 10 and Comparative Example 1 were tested, and the test results are listed in Table 1.

[0143] Table 1 Performance test results of Examples 1 to 10 and Comparative Example 1

[0144] Item Average particle size, μm Solvent content, wt% Example 1 45 0.1 Example 2 38 0.1 Example 3 42 0.1 Example 4 56 0.1 Example 5 32 0.3 Example 6 54 0.4 Example 7 48 0.1 Example 8 34 0.1 Example 9 44 0.2 Example 10 46 0.05 Comparative Example 1 52 0.5

[0145] Compared with Example 1, Comparative Example 1 adopted intermittent operation, and the obtained nylon 1212 salt solid had a larger particle size and a higher solvent content, which proved that the nylon salt obtained by the continuous preparation method of the present invention was efficient and low-energy-consuming, and solved the problems of low mixing efficiency and more solvent residues in the intermittent preparation of long-chain nylon salts in the prior art.

[0146] In Examples 1 to 10, long-chain nylon salts were continuously prepared through a continuous reaction device. The obtained nylon salts had a smaller particle size and a low solvent residue, and there was no need for a cooling-heating process during preparation, which was efficient and low-energy-consuming. The continuous production obtained high-quality nylon salts, which were suitable for the preparation of various nylon salts produced by the solvent crystallization method.

Claims

1. A method for continuously preparing long carbon chain nylon salt, comprising: After rapidly mixing and reacting a solution of diamine and dibasic acid, adjusting the pH by neutralization, then filtering, washing, and purging in a continuous pressure drum filter, and finally drying to remove the solvent to obtain the long carbon chain nylon salt.

2. The method for continuously preparing long carbon chain nylon salt according to claim 1, characterized in that it comprises the following steps: (1) Dissolving the dibasic acid with solvent A and the diamine with solvent B by heating respectively; (2) Continuously adding the diamine solution and the dibasic acid solution obtained in step (1) into a mixer for rapid mixing and reaction to obtain a nylon salt slurry; (3) Adding the nylon salt slurry obtained in step (2) into a continuous salting reactor for neutralization reaction, stabilization, and adjusting the pH; (4) Adding the nylon salt slurry with adjusted pH obtained in step (3) into a continuous pressure drum filter for filtering, washing, and purging to obtain wet nylon salt; (5) Adding the wet nylon salt obtained in step (4) into a continuous dryer for drying to remove the solvent to obtain the long carbon chain nylon salt.

3. The method for continuously preparing long carbon chain nylon salt according to claim 2, characterized in that: In step (1), the dibasic acid is at least one of dibasic acids with C5 - C20, preferably at least one of dibasic acids with C6 - C14; and / or, the diamine is at least one of diamines with C5 - C20, preferably at least one of diamines with C6 - C14; and / or, the solvent A and the solvent B are each independently selected from at least one of methanol, ethanol, and propanol; and / or, the weight ratio of the dibasic acid to the solvent A is 1:(2 - 10); and / or, when the dibasic acid is mixed with the solvent A, it is heated to 50 - 95°C and maintained for 10 - 60 min; and / or, the weight ratio of the diamine to the solvent B is 1:(1 - 6); and / or, when the diamine is mixed with the solvent B, it is heated to 40 - 90°C and maintained for 10 - 60 min.

4. The method for continuously preparing long carbon chain nylon salt according to claim 2, characterized in that: In step (2), the molar dosage ratio of the dibasic acid to the diamine is 1:(0.99 - 1.05), preferably 1:(0.99 - 1.02); and / or, the mixer is a static mixer or a dynamic mixer, and the static mixer is preferably of SV type, SK type, or SL type; and / or, the temperature in the mixer is 60 - 80°C; and / or, the mixing time is 1 - 600 s.

5. The method for continuously preparing long carbon chain nylon salt according to claim 2, characterized in that: In step (3), the continuous salting reactor is a continuous stirred tank reactor; and / or, the temperature for the neutralization reaction and stabilization is 60 - 80°C; and / or, the time for the neutralization reaction and stabilization is 0.1 - 1.0 h; and / or, adjusting the pH to 6.5 - 7.

5.

6. The method for continuously preparing long carbon chain nylon salt according to claim 2, characterized in that: In step (4), The continuous pressure drum filter includes a slurry feeding and filtering area, a filter cake washing area, a filter cake drying area, and a filter cake discharging area; and / or, The filtration pressure is 0.1 to 1.0 MPa; and / or, The filtration temperature is 20 to 80 °C.

7. The method for continuously preparing long-chain nylon salt according to claim 2, characterized in that: In step (5), The continuous dryer is a continuous tower dryer or a continuous rake dryer; preferably vacuum drying, and further preferably, The drying temperature is 60 to 100 °C; and / or, The drying time is 0.5 to 4.0 h; and / or, The vacuum pressure is 0.01 to 10 kPa.

8. A system for continuously preparing long-chain nylon salt by using the method according to claims 1 to 7, comprising a dibasic acid dissolving kettle, a diamine dissolving kettle, a mixer, a continuous salt-forming reactor, a continuous pressure drum filter, and a continuous tower dryer; the dibasic acid dissolving kettle and the diamine dissolving kettle are respectively connected to the mixer through metering pumps, and the mixer, the continuous salt-forming reactor, the continuous pressure drum filter, and the continuous tower dryer are connected in sequence; Preferably, the mixer and the continuous salt-forming reactor can make the temperature rise not exceed 5 °C after the dibasic acid and the diamine are mixed and reacted; and / or, The continuous pressure drum filter includes a slurry feeding and filtering area, a filter cake washing area, a filter cake drying area, and a filter cake discharging area.

9. A long-chain nylon salt prepared by the method according to any one of claims 1 to 7 or the system according to claim 8; preferably, the particle size of the long-chain nylon salt is 10 to 100 μm, and the solvent content is less than or equal to 0.5 wt%.

10. An application of the long-chain nylon salt according to claim 9 in the field of long-chain nylon.

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