A method and system for continuous salt formation of long carbon chain polyamides

Abstract

The application discloses a long carbon chain polyamide continuous salting method and system, and the method comprises the following steps: mixing a long carbon chain binary acid dispersion liquid I and a long carbon chain binary amine dispersion liquid II in a mixer, and then feeding the mixture into a reaction kettle to obtain a reaction product; the reaction product is divided into two streams, a first stream of the reaction product is circulated back into the reaction kettle, and a second stream of the reaction product is taken out. In the method, the conversion rate of the reaction kettle binary acid is greater than 99.50%, the particle size of the obtained solid salt particles is located in the range of 20-40 microns, the particle size distribution is narrow, and the impurity content in the solid salt is less than 0.20 wt%.

Description

Technical Field

[0001] This invention belongs to the field of production technology of long carbon chain polyamide salts, and particularly relates to the control process of salt formation of long carbon chain polyamide salts. Specifically, it relates to a method and system for continuous salt formation of long carbon chain polyamides. Background Technology

[0002] Long-chain polyamides refer to polyamides with ten or more methylene groups in their chain segments. As the number of methylene carbon chains increases, the concentration of amide groups decreases, and the properties of the polyamide change. Therefore, long-chain polyamides possess most of the general properties of ordinary polyamides, such as good mechanical properties, wear resistance, lubricity, solvent resistance, and ease of molding and processing, in addition to unique advantages such as low water absorption, good dimensional stability, and excellent dielectric properties. Due to their superior properties compared to short-chain polyamides, they are a key research area both domestically and internationally.

[0003] As the number of carbon chains increases, the solubility of diacids and diamines in water gradually decreases, requiring heating to completely dissolve them. Therefore, most disclosed long-chain polyamide production processes require dissolving diacids and diamines in organic solvents and then mixing them intermittently to produce long-chain polyamide salts.

[0004] CN112778517A discloses a continuous production method for long-chain nylon 1018 salt, including steps such as reacting octadecanoic acid, decanediamine and water in a reactor, crystallizing the resulting nylon 1018 salt aqueous solution through a crystallizer, and obtaining nylon 1018 salt by solid-liquid separation of the nylon 1018 salt suspension. This invention is only applicable to the salt formation of short-chain dicolic acids and short-chain diamines that are easily soluble in water.

[0005] CN212167418U discloses a raw material preparation device for continuous nylon salt formation. A dibasic acid rotary discharge valve is located at the bottom of the dibasic acid silo. The outlet of the rotary discharge valve is connected to the feed port of the dibasic acid slurry preparation tank, and its rotation speed is controlled by the liquid level in the dibasic acid slurry preparation tank. A spray column is located at the top of the dibasic acid slurry preparation tank, with an exhaust bend at the top and nozzles at the top. The water supply pipes for the nozzles are connected to a dibasic acid preparation pure water flow meter and a dibasic acid preparation pure water control device. The valve is connected to the pure water supply pipe. The inner cavity of the dicarboxylic acid slurry mixing tank is equipped with a frame-type stirrer. The bottom outlet is connected to the inlet of the dicarboxylic acid slurry delivery pump. The dicarboxylic acid slurry supply pipe at the outlet of the dicarboxylic acid slurry delivery pump is equipped with an online density meter and a flow meter for dicarboxylic acid slurry, and is connected to the dicarboxylic acid inlet of the primary salt-forming tank. The dicarboxylic acid mixing pure water flow meter is controlled by the online density meter for dicarboxylic acid slurry. This invention provides a solution only for the continuous mixing of short-chain dicarboxylic acids that are easily soluble in water.

[0006] CN111039791A discloses a method and apparatus for the continuous production of long-chain nylon salt aqueous solution. The method involves melting a long-chain diacid, mixing it with a long-chain diamine and water, and performing a two-stage salt-forming reaction. After adjusting the pH of the aqueous solution, a nylon salt aqueous solution for use in polycondensation reactions is obtained. The apparatus includes a continuous melting unit for the long-chain diacid and a corresponding control system, a salt-forming reaction unit, and a corresponding control system and salt storage unit. A drawback of this invention is that the long-chain diacid and long-chain diamine must be dissolved in water under high temperature and high pressure conditions, which increases both equipment costs and energy consumption. Summary of the Invention

[0007] In order to overcome the problems existing in the prior art, the present invention provides a method and system for continuous salt formation of long carbon chain polyamide, which mainly solves the problems of poor batch stability of intermittent salt formation, high labor costs, difficulty in equipment scale-up, and lack of reliable control scheme for continuous salt formation process in polyamide production.

[0008] Existing patents and literature reports on nylon salt formation processes mostly focus on intermittent salt formation processes for short-chain, water-soluble diacids or diamines. There is little attention paid to continuous salt formation processes for long-chain nylon salts, and almost no control schemes are available for the salt formation reaction process of long-chain nylon salts. This invention proposes for the first time a stable control process for the salt formation reaction of long-chain nylon salts. Experimental verification shows that the obtained nylon salt has fewer impurities and higher quality, providing a good foundation for the subsequent production of long-chain nylon resins.

[0009] One of the objectives of this invention is to provide a method for the continuous salt formation of long-chain polyamides, comprising: mixing a dispersion I containing a long-chain dicarboxylic acid and a dispersion II containing a long-chain diamine in a mixer and then entering a reaction vessel to react and obtain a reaction product, wherein the reaction product is divided into two streams, the first stream of reaction product is recycled back into the reaction vessel, and the second stream of reaction product is collected externally.

[0010] In this process, long-chain dicarboxylic acids and long-chain diamines undergo partial reactions in the mixer, while the remainder is completed in the reaction vessel.

[0011] In a preferred embodiment, the long-chain dicarboxylic acid is selected from C7 to C14 dicarboxylic acids, and the long-chain diamine is selected from C9 to C14 diamines.

[0012] In a further preferred embodiment, the long-chain dicarboxylic acid is selected from C8 to C14 dicarboxylic acids, and the long-chain diamine is selected from C10 to C14 diamines.

[0013] In a preferred embodiment, a long-chain dicarboxylic acid is mixed with dispersant I to obtain dispersion I containing the long-chain dicarboxylic acid, and / or a long-chain diamine is mixed with dispersant II to obtain dispersion II containing the long-chain diamine.

[0014] In a further preferred embodiment, dispersant I and dispersant II are each independently selected from organic solvents, preferably from one or more organic alcohol solvents (e.g., C2-C8 organic alcohols), and more preferably from one or more of ethanol, isopropanol, and tert-butanol.

[0015] In a further preferred embodiment, the mass concentration of the long-chain dicarboxylic acid in dispersion I is 10-40 wt%, preferably 15-30 wt%, and / or the mass concentration of the long-chain diamine in dispersion II is 30-70 wt%, preferably 40-60 wt%.

[0016] For example, the mass concentration of the long-chain dicarboxylic acid in dispersion I is 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%, 22 wt%, 25 wt%, 28 wt%, 30 wt%, 35 wt%, or 40 wt%, and the mass concentration of the long-chain diamine in dispersion II is 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, or 70 wt%.

[0017] In a preferred embodiment, a stirring device is provided inside the reaction vessel.

[0018] The salt containing amide bonds in the reaction vessel has a density of 1000–1200 kg / m³. 3 Preferred weight: 1000–1180 kg / m³ 3 For example, 1000 kg / m 3 1020kg / m 3 1040kg / m 3 1060kg / m 3 1080kg / m 3 1100kg / m 3 1120kg / m 3 1140kg / m 3 1160kg / m 3 1180kg / m 3 Or 1200kg / m 3 .

[0019] In a further preferred embodiment, the amide-containing salt in the reaction vessel is controlled to be in a fully suspended state (or uniformly mixed). The amide-containing salt is generated by a neutralization reaction between a long-chain dicarboxylic acid and a long-chain diamine, and this neutralization reaction is an exothermic reaction.

[0020] In a preferred embodiment, the first reaction product first enters the mixer and mixes with dispersion I and dispersion II, and then they are fed together into the reaction vessel.

[0021] In a further preferred embodiment, after long-term operation, the weight ratio of the first reaction product to the total weight of dispersion I and dispersion II is (8-50):1, preferably (8-40):1, for example 8:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1 or 50:1.

[0022] In this design, the first reaction product has a multiple mass flow rate relative to the feed (dispersion I and dispersion II). This means the exothermic neutralization reaction of dispersion I and dispersion II is carried out by a larger flow rate, resulting in a significant decrease in reaction temperature rise. Furthermore, the concentrations of unreacted long-chain dicarboxylic acids and unreacted long-chain diamines in the first reaction product are very low, requiring a long residence time for complete reaction. In this technical solution, the first reaction product, containing low concentrations of long-chain dicarboxylic acids and long-chain diamines, is forcibly mixed with high-concentration dispersions I and II in the mixer, significantly shortening the reaction time and improving reactor utilization efficiency.

[0023] In a preferred embodiment, the reaction products are cooled by a heat exchanger and then divided into the two streams. A refrigerant inlet pipeline and a refrigerant outlet pipeline are provided on the heat exchanger, and a refrigerant outlet control valve V3 is provided on the refrigerant outlet pipeline. Preferably, the opening degree of the refrigerant outlet control valve V3 is controlled by a first control module TIC.

[0024] The heat exchanger uses a refrigerant to cool the reaction products.

[0025] In a further preferred embodiment, the reaction product is pressurized by a pump and then sent into the heat exchanger, wherein the pump is a slurry pump for conveying solid-liquid two-phase materials.

[0026] In a preferred embodiment, a temperature detector TE is provided at the mixer outlet, and both the temperature detector TE and the refrigerant discharge control valve V3 are electrically connected to the first control module TIC.

[0027] In a further preferred embodiment, the temperature detector TE detects the material temperature at the discharge end of the mixer and transmits the material temperature to the first control module TIC. The first control module TIC then controls the opening of the refrigerant discharge valve V3 to control the refrigerant flow rate of the heat exchanger.

[0028] In a further preferred embodiment, when the material temperature exceeds a set value, the first control module TIC controls the opening of the refrigerant discharge control valve V3 to increase until the material temperature returns to the set value; when the material temperature is lower than the set value, the first control module TIC controls the opening of the refrigerant discharge control valve V3 to decrease until the material temperature returns to the set value; wherein, the set value is 67±3℃.

[0029] In a preferred embodiment, the real-time mass flow rate of the dispersion I is detected. When the mass flow rate of the dispersion I fluctuates, the detected real-time mass flow rate signal of the dispersion I is transmitted to the first control module TIC. The first control module TIC adjusts the flow rate value of the refrigerant required by the heat exchanger according to formula (1) and adjusts the opening degree of the refrigerant discharge valve V3 in advance.

[0030] The conventional operation in the existing technology is as follows: when the mass flow rate of dispersion I is detected by real-time signal FC1 and changes due to external factors, FY adjusts the flow rate of FC2 by proportional control (which will cause the flow rate of FC2 to change). Since both FC1 and FC2 have changed, the temperature after the reaction (the temperature detected by TE) will change. TE transmits the temperature signal to TIC and then adjusts the opening of V3. However, this will result in a large lag.

[0031] m 冷媒 *C p冷媒 *▲T=A*m 二酸 *c 二酸 Equation (1)

[0032] In equation (1), m 冷媒 The refrigerant discharge mass flow rate from the heat exchanger is expressed in kg / h; C p冷媒 ▲T represents the constant-pressure heat capacity of the refrigerant, kJ / (kg·K); ▲T represents the temperature difference between the refrigerant outlet and inlet, K; m 二酸 c is the real-time mass flow rate of dispersion I, kg / h; 二酸 The mass percentage of diacid in dispersion I is wt%; A is a coefficient, kJ / kg, and A is 1.40 to 1.60, preferably 1.45 to 1.55, for example 1.4, 1.42, 1.44, 1.46, 1.48, 1.5, 1.52, 1.54 or 1.55.

[0033] Among them, FC1 detects the mass flow rate m of dispersion I in real time.二酸 Based on the mass flow rate fluctuation of dispersion I, the first control module is input to control the refrigerant discharge flow rate in advance. The temperature of the reaction system can be kept stable by controlling the above formula (1).

[0034] Preferably, a dispersion I feed line and a dispersion II feed line are provided at the feed end of the mixer, a dispersion I mass flow meter FC1 is provided on the dispersion I feed line, and a dispersion II mass flow meter FC2 is provided on the dispersion II feed line.

[0035] More preferably, the dispersion liquid I mass flow meter FC1 and the refrigerant discharge valve V3 are both electrically connected to the first control module TIC, and the first control module TIC controls the opening degree of the refrigerant discharge valve V3 through formula (1).

[0036] In a preferred embodiment, the mixer is a static mixer, designed to ensure good dispersion and thorough mixing between dispersion I and dispersion II.

[0037] The static mixer can be any type of static mixer disclosed in the prior art, as long as it can promote good dispersion and thorough mixing between dispersion I and dispersion II. For example, it can be an SK type static mixer.

[0038] In a preferred embodiment, the feed molar ratio of the long-chain dicarboxylic acid to the long-chain diamine is controlled to be 1:(1 to 1.10), preferably 1:(1 to 1.08), for example 1:1, 1:1.02, 1:1.04, 1:1.06, 1:1.08 or 1.10.

[0039] In a preferred embodiment, the reaction product (from the discharge end of the reactor) is subjected to online near-infrared detection to obtain an online near-infrared detection signal, the online near-infrared detection signal including the real-time alkalinity value (pH) of the reaction product.

[0040] More preferably, the real-time feed mass flow rate ratio K of dispersion II (diamine) and dispersion I (diacid) is adjusted according to the real-time alkalinity value pH obtained from the online near-infrared detection signal, and then the mass flow rate of dispersion II is controlled according to the real-time feed mass flow rate ratio K and the mass flow rate of dispersion I.

[0041] In this process, the feed flow rate of dispersion I is kept constant, and the feed flow rate of dispersion II is controlled according to the K value.

[0042] In a further preferred embodiment, the real-time feed mass flow rate ratio K is obtained according to equation (2):

[0043]

[0044] In equation (2), pH is the real-time alkalinity value obtained from the online near-infrared detection signal, and c 二酸 c 二胺 These represent the mass percentages of diacid in dispersion I and diamine in dispersion II, respectively. 二酸 M 二胺 α represents the molecular weights of the diacid and diamine, respectively; α represents the conversion rate of the diacid, i.e., the conversion rate at the pH value obtained from the online near-infrared detection signal; and B is the proportionality coefficient, with a value of 0.990–1.010, preferably 0.995–1.005, such as 0.990, 0.992, 0.994, 0.996, 0.998, 1.000, 1.002, 1.004, 1.006, 1.008, or 1.010.

[0045] The system includes an online near-infrared analyzer controller. Based on the real-time alkalinity value (pH) of the reaction product stream, the real-time feed mass ratio (K) of dispersion I and / or dispersion II is obtained. Then, the opening of the dispersion II feed regulating valve is adjusted according to formula (3) to change the raw material ratio.

[0046] In a preferred embodiment, the residence time of the material in the reactor is 2 to 8 hours, preferably 2 to 6 hours, for example 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours.

[0047] A second objective of this invention is to provide a system for the continuous salt formation of long-chain polyamides, preferably used for the method described in one objective of this invention. The system includes a mixer and a reactor. A dispersion I feed line and a dispersion II feed line are provided at the feed end of the mixer. A mixture conveying line is provided between the discharge end of the mixer and the feed end of the reactor. A reaction product circulation line is provided between the discharge end of the reactor and the feed end of the mixer. An external bypass line for the reaction product is provided on the reaction product circulation line.

[0048] A stirring device is installed inside the reaction vessel.

[0049] In a preferred embodiment, a heat exchanger is provided on the reaction product circulation pipeline (preferably before the reaction product external bypass pipeline along the material flow direction).

[0050] In a further preferred embodiment, a refrigerant inlet pipeline and a refrigerant outlet pipeline are provided on the heat exchanger, and a refrigerant flow regulating valve V3 is provided on the refrigerant outlet pipeline.

[0051] In a further preferred embodiment, a temperature sensor is independently installed on the refrigerant outlet pipeline and the refrigerant inlet pipeline of the heat exchanger to detect the temperature difference between the refrigerant outlet and the inlet.

[0052] In a preferred embodiment, a booster pump is provided on the reaction product circulation line (preferably before the heat exchanger along the material flow direction).

[0053] In a preferred embodiment, the system further includes a first control module TIC for controlling the opening degree of the refrigerant flow regulating valve V3.

[0054] In a preferred embodiment, a temperature detector TE is provided on the mixed material conveying pipeline to detect the material temperature from the mixer outlet.

[0055] In a further preferred embodiment, the temperature detector TE and the refrigerant flow regulating valve V3 are both electrically connected to the first control module TIC.

[0056] The temperature detector TE detects the material temperature at the discharge end of the mixer and transmits the material temperature to the first control module TIC. The first control module TIC then controls the opening of the refrigerant discharge valve V3 to control the refrigerant flow rate of the heat exchanger.

[0057] In a further preferred embodiment, when the material temperature exceeds a set value, the first control module TIC controls the opening of the refrigerant discharge control valve V3 to increase until the material temperature returns to the set value; when the material temperature is lower than the set value, the first control module TIC controls the opening of the refrigerant discharge control valve V3 to decrease until the material temperature returns to the set value; wherein, the set value is 67±3℃.

[0058] In a preferred embodiment, a mass flow meter FC1 for dispersing liquid I is installed on the feed line of dispersing liquid I to detect the real-time mass flow rate of dispersing liquid I; and a mass flow meter FC2 for dispersing liquid II is installed on the feed line of dispersing liquid II to detect the real-time mass flow rate of dispersing liquid II.

[0059] In a further preferred embodiment, the dispersion liquid I mass flow meter FC1 and the refrigerant flow regulating valve V3 are both electrically connected to the first control module TIC, preferably in the manner shown in equation (1).

[0060] The dispersion liquid I mass flow meter FC1 transmits the detected real-time mass flow rate of dispersion liquid I to the first control module TIC, and the first control module TIC controls the refrigerant flow regulating valve V3 according to equation (1):

[0061] m 冷媒 *C p冷媒 *▲T=A*m 二酸 *c 二酸 Equation (1)

[0062] In equation (1), m 冷媒 The refrigerant discharge mass flow rate from the heat exchanger is expressed in kg / h; C p冷媒 ▲T represents the constant-pressure heat capacity of the refrigerant, kJ / (kg·K); ▲T represents the temperature difference between the refrigerant outlet and inlet, K; m 二酸 c is the real-time mass flow rate of dispersion I, kg / h; 二酸 The mass percentage of diacid in dispersion I is wt%; A is a coefficient, kJ / kg, and A is 1.40 to 1.60, preferably 1.45 to 1.55, for example 1.4, 1.42, 1.44, 1.46, 1.48, 1.5, 1.52, 1.54 or 1.55.

[0063] In a preferred embodiment, the mixer is a static mixer (e.g., SK type) with multiple mixing unit internals disposed therein.

[0064] In a preferred embodiment,

[0065] An online near-infrared detector is installed on the reaction product circulation line (preferably before the booster pump in the direction of salt material flow) to detect online near-infrared detection signals, including the real-time alkalinity value (pH) of the reaction product; and / or,

[0066] A mass flow meter FC1 for dispersion I and a flow regulating valve for dispersion I are installed on the feed line of dispersion I; a mass flow meter FC2 for dispersion II and a flow regulating valve for dispersion II are installed on the feed line of dispersion II; and / or,

[0067] The system further includes a second control module FY, used to adjust the mass flow rate of dispersion II based on the mass flow rate of dispersion I.

[0068] In a further preferred embodiment, the online near-infrared detector and the dispersion II flow regulating valve are each independently electrically connected to the second control module FY, and the second control module FY obtains the real-time feed mass flow ratio K of the dispersion II and the dispersion I according to formula (2).

[0069] In a further preferred embodiment, the dispersion I mass flow meter FC1, the dispersion II mass flow meter FC2, and the dispersion II flow regulating valve are each independently electrically connected to the second control module FY, preferably in the manner shown in equation (3); wherein, the second control module FY obtains the mass flow rate of dispersion II based on the real-time feed mass flow rate ratio K and the mass flow rate of dispersion I, and uses the dispersion II flow regulating valve to control the mass flow rate of dispersion II.

[0070]

[0071] In equation (3), m 二酸 The real-time mass flow rate of dispersion I is kg / h; m 二胺 , where is the real-time mass flow rate of dispersion II, kg / h.

[0072] In this process, the mass flow rate of dispersion I is kept constant, while the mass flow rate of dispersion II is controlled based on the K value, thereby changing the raw material ratio.

[0073] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0074] Compared with the prior art, the present invention has the following beneficial effects:

[0075] (1) It solves the problems of poor batch stability of intermittent salt formation, high labor costs, difficulty in equipment scale-up, and lack of reliable control scheme for continuous salt formation process in the production of long carbon chain polyamide.

[0076] (2) The conversion rate of diacid in the reactor is ≥99.50%, the particle size of the obtained solid salt particles is 20-40 μm, the particle size distribution is narrow, and the impurity content in the solid salt is <0.20 wt%. Attached Figure Description

[0077] Figure 1 A schematic diagram of the system described in this invention is shown.

[0078] exist Figure 1The components are as follows: 111 Dispersion I (diacid) stream, 112 Dispersion II (diamine) stream, 113 Mixed stream, 114 Reaction product stream, 115 Pressurized reaction product stream, 116 Second reaction product stream (crude product externally sourced stream), 117 First reaction product stream (circulating stream), 121 Refrigerant feed stream, 122 Refrigerant discharge stream, E Heat exchanger, R Reactor, P Circulating pump, M Mixer, V1 Dispersion I flow control valve, V2 Dispersion II flow control valve, V3 Refrigerant flow control valve, FC1 - Dispersion I mass flow meter FC1, FC2 - Dispersion II mass flow meter FC2, TE Temperature detector, TIC First control module, FY Second control module, AC Online near-infrared controller.

[0079] In this invention, after the reaction product stream 114 flows out from the bottom of the reactor R, it is pressurized by the circulating pump P and sent to the heat exchanger E for cooling. After cooling, it is divided into two streams: one is the crude product stream 116, which is sent out of the system, and the other is the circulating stream 117, which enters the mixer M. After being fully mixed with the dispersion I containing long-chain dicarboxylic acid and the dispersion II containing long-chain diamine in the mixer M, it is returned to the reactor R.

[0080] When the temperature detector TE detects that the temperature of the mixed material 113 exceeds or falls below the set temperature, the first control module TIC controls the refrigerant discharge control valve V3 of the heat exchanger to regulate the discharge of refrigerant until the temperature of the mixed material 113 returns to the set value.

[0081] When the mass flow rate of dispersion I (diacid) stream 111 fluctuates, the first control module TIC controls the refrigerant discharge control valve V3 in advance according to formula (1) to regulate the discharge of refrigerant, so as to achieve the purpose of stabilizing the temperature of the mixed stream 113 in advance.

[0082] The online near-infrared controller AC detects the real-time alkalinity (pH) of the reaction product stream 114 in real time, and obtains the flow ratio (K) of dispersion II (diamine) stream and dispersion I (diacid) stream based on the real-time alkalinity (pH) and the second control module FY. Keeping the mass flow rate of dispersion I constant, the second control module FY then uses the flow ratio (K) and the mass flow rate of dispersion I stream to adjust the mass flow rate of dispersion II stream, so as to ensure that the real-time alkalinity (pH) of the reaction product stream 114 is within a suitable range or within the theoretical range. Detailed Implementation

[0083] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection 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 are still within the scope of protection of the present invention.

[0084] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0085] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0086] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0087] The mixer used in this embodiment is a common SK-type mixer, such as the stainless steel SK-type mixer produced by Shanghai Anquan Machinery Co., Ltd.

[0088] The conversion rate of diacid in the reactor was obtained as follows:

[0089]

[0090] Where: m 出料 The mass flow rate of the outflow material is kg / h; c 二酸出料 The mass percentage of diacid in the discharge stream; m 二酸进料 The mass flow rate of the feed diacid solution is kg / h; c 二酸进料 This represents the mass percentage of diacid in the feed diacid solution.

[0091] The particle size of the obtained solid salt particles was obtained by laser particle size analyzer.

[0092] The impurity content in solid salt is obtained as follows: the mixture of solid salt and ethanol is detected by gas chromatography or liquid chromatography.

[0093]

Example 1

[0094] use Figure 1 The system shown has a C12 dicarboxylic acid and a C12 diamine. The molar ratio of the long-chain dicarboxylic acid to the long-chain diamine is 1:1.04. The long-chain dicarboxylic acid is mixed with dispersant I to obtain a dispersion I with a mass concentration of 25 wt%, and / or the long-chain diamine is mixed with dispersant II to obtain a dispersion II with a mass concentration of 50 wt%.

[0095] Dispersion I containing a long-chain dicarboxylic acid and dispersion II containing a long-chain diamine are mixed in a mixer and then fed into a reaction vessel to obtain reaction products. The reaction products are pressurized by a slurry pump and sent to a heat exchanger, where they are cooled and separated into two streams. The first stream of reaction products is recycled back into the reaction vessel, while the second stream is collected externally. The first stream of reaction products first enters the mixer and mixes with dispersions I and II before being fed together into the reaction vessel. A stirring device is installed in the reaction vessel, and the density of the amide-containing salt in the reaction vessel is 1160 kg / m³. 3 After long-term operation, the weight ratio of the first reaction product to the total weight of dispersion I and dispersion II is 25:1.

[0096] A refrigerant inlet line and a refrigerant outlet line are provided on the heat exchanger. A refrigerant outlet control valve V3 is installed on the refrigerant outlet line. The opening degree of the refrigerant outlet control valve V3 is controlled by a first control module TIC. A temperature detector TE is installed at the mixer outlet. Both the temperature detector TE and the refrigerant outlet control valve V3 are electrically connected to the first control module TIC. The temperature detector TE detects the material temperature at the mixer outlet and transmits the material temperature to the first control module TIC. The first control module TIC then controls the opening degree of the refrigerant outlet valve V3 to control the refrigerant flow rate in the heat exchanger. Specifically, when the material temperature exceeds a set value, the first control module TIC controls the opening degree of the refrigerant outlet control valve V3 to increase until the material temperature returns to the set value. When the material temperature is lower than the set value, the first control module TIC controls the opening degree of the refrigerant outlet control valve V3 to decrease until the material temperature returns to the set value. The set value is 67±3℃.

[0097] The real-time mass flow rate of the dispersion I is detected. When the mass flow rate of the dispersion I fluctuates, the detected real-time mass flow rate signal of the dispersion I is transmitted to the first control module TIC as a feedforward control signal of the temperature controller TE. The first control module TIC adjusts the flow rate of the refrigerant required by the heat exchanger according to equation (1) and adjusts the opening of the refrigerant discharge valve V3 in advance. In equation (1), A is 1.50.

[0098] The reaction product (from the outlet of the reactor) is subjected to online near-infrared detection to obtain an online near-infrared detection signal, which includes the real-time alkalinity value of the reaction product. The real-time feed flow ratio K of dispersion I and dispersion II is obtained according to equation (2), and the mass flow rate of dispersion II is adjusted according to equation (3); in equation (2), B is taken as 1.0.

[0099] The residence time of the materials in the reactor is 5 hours.

[0100] In Example 1, the conversion rate of diacid in the reactor was 99.85%, the particle size of the obtained solid salt particles was 25-40 μm, the proportion of particles with a diameter of 30-40 μm was 94.5%, and the impurity content in the solid salt was 0.1 wt%.

[0101]

Example 2

[0102] use Figure 1 The system shown has a C9 dicarboxylic acid and a C14 diamine. The molar ratio of the long-chain dicarboxylic acid to the long-chain diamine is 1:1.08. The long-chain dicarboxylic acid is mixed with dispersant I to obtain a dispersion I with a mass concentration of 30 wt%, and / or the long-chain diamine is mixed with dispersant II to obtain a dispersion II with a mass concentration of 40 wt%.

[0103] Dispersion I containing a long-chain dicarboxylic acid and dispersion II containing a long-chain diamine are mixed in a mixer and then fed into a reaction vessel to obtain reaction products. The reaction products are pressurized by a slurry pump and sent to a heat exchanger, where they are cooled and separated into two streams. The first stream of reaction products is recycled back into the reaction vessel, while the second stream is collected externally. The first stream of reaction products first enters the mixer and mixes with dispersions I and II before being fed together into the reaction vessel. A stirring device is installed in the reaction vessel, and the density of the amide-containing salt in the reaction vessel is 1180 kg / m³. 3 After long-term operation, the weight ratio of the first reaction product to the total weight of dispersion I and dispersion II is 8:1.

[0104] A refrigerant inlet line and a refrigerant outlet line are provided on the heat exchanger. A refrigerant outlet control valve V3 is installed on the refrigerant outlet line. The opening degree of the refrigerant outlet control valve V3 is controlled by a first control module TIC. A temperature detector TE is installed at the mixer outlet. Both the temperature detector TE and the refrigerant outlet control valve V3 are electrically connected to the first control module TIC. The temperature detector TE detects the material temperature at the mixer outlet and transmits the material temperature to the first control module TIC. The first control module TIC then controls the opening degree of the refrigerant outlet valve V3 to control the refrigerant flow rate in the heat exchanger. Specifically, when the material temperature exceeds a set value, the first control module TIC controls the opening degree of the refrigerant outlet control valve V3 to increase until the material temperature returns to the set value. When the material temperature is lower than the set value, the first control module TIC controls the opening degree of the refrigerant outlet control valve V3 to decrease until the material temperature returns to the set value. The set value is 67±3℃.

[0105] The real-time mass flow rate of the dispersion I is detected. When the mass flow rate of the dispersion I fluctuates, the detected real-time mass flow rate signal of the dispersion I is transmitted to the first control module TIC as a feedforward control signal of the temperature controller TE. The first control module TIC adjusts the flow rate of the refrigerant required by the heat exchanger according to equation (1) and adjusts the opening of the refrigerant discharge valve V3 in advance. In equation (1), A is 1.45.

[0106] The reaction product (from the outlet of the reactor) is subjected to online near-infrared detection to obtain an online near-infrared detection signal, which includes the real-time alkalinity value of the reaction product. The real-time feed flow ratio K of dispersion I and dispersion II is obtained according to equation (2), and the mass flow rate of dispersion II is adjusted according to equation (3); in equation (2), B is taken as 1.005.

[0107] The residence time of the materials in the reactor is 2 hours.

[0108] In Example 1, the conversion rate of diacid in the reactor was 99.7%, the particle size of the obtained solid salt particles was between 20 and 36 μm, the proportion of particles with a size of 30 to 36 μm was 95.5%, and the impurity content in the solid salt was 0.12 wt%.

[0109]

Example 3

[0110] use Figure 1 The system shown has a C14 dicarboxylic acid and a C10 diamine. The molar ratio of the long-chain dicarboxylic acid to the long-chain diamine is 1:1.00. The long-chain dicarboxylic acid is mixed with dispersant I to obtain a dispersion I with a mass concentration of 15 wt%, and / or the long-chain diamine is mixed with dispersant II to obtain a dispersion II with a mass concentration of 60 wt%.

[0111] Dispersion I containing a long-chain dicarboxylic acid and dispersion II containing a long-chain diamine are mixed in a mixer and then fed into a reaction vessel to obtain reaction products. The reaction products are pressurized by a slurry pump and sent to a heat exchanger, where they are cooled and separated into two streams. The first stream of reaction products is recycled back into the reaction vessel, while the second stream is collected externally. The first stream of reaction products first enters the mixer and mixes with dispersions I and II before being fed together into the reaction vessel. A stirring device is installed in the reaction vessel, and the density of the amide-containing salt in the reaction vessel is 1040 kg / m³. 3 After long-term operation, the weight ratio of the first reaction product to the total weight of dispersion I and dispersion II is 40:1.

[0112] A refrigerant inlet line and a refrigerant outlet line are provided on the heat exchanger. A refrigerant outlet control valve V3 is installed on the refrigerant outlet line. The opening degree of the refrigerant outlet control valve V3 is controlled by a first control module TIC. A temperature detector TE is installed at the mixer outlet. Both the temperature detector TE and the refrigerant outlet control valve V3 are electrically connected to the first control module TIC. The temperature detector TE detects the material temperature at the mixer outlet and transmits the material temperature to the first control module TIC. The first control module TIC then controls the opening degree of the refrigerant outlet valve V3 to control the refrigerant flow rate in the heat exchanger. Specifically, when the material temperature exceeds a set value, the first control module TIC controls the opening degree of the refrigerant outlet control valve V3 to increase until the material temperature returns to the set value. When the material temperature is lower than the set value, the first control module TIC controls the opening degree of the refrigerant outlet control valve V3 to decrease until the material temperature returns to the set value. The set value is 67±3℃.

[0113] The real-time mass flow rate of the dispersion I is detected. When the mass flow rate of the dispersion I fluctuates, the detected real-time mass flow rate signal of the dispersion I is transmitted to the first control module TIC as a feedforward control signal of the temperature controller TE. The first control module TIC adjusts the flow rate of the refrigerant required by the heat exchanger according to equation (1) and adjusts the opening of the refrigerant discharge valve V3 in advance. In equation (1), A is 1.55.

[0114] The reaction product (from the outlet of the reactor) is subjected to online near-infrared detection to obtain an online near-infrared detection signal, which includes the real-time alkalinity value of the reaction product. The real-time feed flow ratio K of dispersion I and dispersion II is obtained according to equation (2), and the mass flow rate of dispersion II is adjusted according to equation (3); in equation (2), B is 0.995.

[0115] The residence time of the materials in the reactor is 6 hours.

[0116] In Example 1, the conversion rate of diacid in the reactor was 99.95%, the particle size of the obtained solid salt particles was between 28 and 40 μm, the proportion of particles between 30 and 40 μm was 96.0%, and the impurity content in the solid salt was 0.07% wt%.

[0117]

Example 4

[0118] The process of Example 1 was repeated, except that when the mass flow rate of dispersion I fluctuated, the opening of refrigerant discharge valve V3 was not adjusted in advance using formula (1).

[0119] In Example 4, the conversion rate of diacid in the reactor was 99.50%, the particle size of the obtained solid salt particles was between 20 and 40 μm, the proportion of particles between 30 and 40 μm was 90.5%, and the impurity content in the solid salt was 0.14 wt%.

[0120] Comparative Example 1

[0121] The process of Example 1 is repeated, except that all reaction products are collected externally and are not recycled back into the reactor. Long-chain dicarboxylic acids and long-chain diamines are also mixed in the mixer before entering the reactor.

[0122] In Comparative Example 1, the conversion rate of diacid in the reactor was 95.2%, and the particle size of the obtained solid salt particles was between 10 and 60 μm (the distribution was significantly wider), with 30 to 40 μm accounting for 70.1%, and the impurity content in the solid salt was 2.14 wt%.

[0123] Comparative Example 2

[0124] The process of Example 1 was repeated, except that all reaction products were collected externally and not recycled back into the reactor, and there was no mixer; long-chain dicarboxylic acids and long-chain diamines were directly introduced into the reactor.

[0125] In Comparative Example 2, the conversion rate of diacid in the reactor was 91.7%, and the particle size of the obtained solid salt particles was between 10 and 60 μm (the distribution was significantly wider), with 30 to 40 μm accounting for 64.8%, and the impurity content in the solid salt was 3.14 wt%.

[0126] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for continuous salt formation of long-chain polyamide, comprising: Dispersion I containing long-chain dicarboxylic acid and dispersion II containing long-chain diamine are mixed in a mixer and then fed into a reaction vessel to obtain reaction products. The reaction products are divided into two streams: the first stream of reaction products is recycled back into the reaction vessel, and the second stream of reaction products is collected externally.

2. The method according to claim 1, characterized in that, The long-chain dicarboxylic acid is selected from C7 to C14 dicarboxylic acids, and the long-chain diamine is selected from C9 to C14 diamines; preferably, the long-chain dicarboxylic acid is selected from C8 to C14 dicarboxylic acids, and the long-chain diamine is selected from C10 to C14 diamines. And / or, Dispersion I containing the long-chain dicarboxylic acid is obtained by mixing the long-chain dicarboxylic acid with dispersant I, and / or dispersion II containing the long-chain diamine is obtained by mixing the long-chain diamine with dispersant II; preferably, dispersant I and dispersant II are each independently selected from organic solvents, preferably from one or more organic alcohol solvents; And / or, The long-chain dicarboxylic acid in dispersion I has a mass concentration of 10–40 wt%, preferably 15–30 wt%, and / or the long-chain diamine in dispersion II has a mass concentration of 30–70 wt%, preferably 40–60 wt%.

3. The method according to claim 1, characterized in that, The first reaction product first enters the mixer and mixes with dispersion I and dispersion II, and then they are sent together into the reaction vessel; preferably, the weight ratio of the first reaction product to the total weight of dispersion I and dispersion II is (8-50):1, more preferably (8-40):

1.

4. The method according to any one of claims 1 to 3, characterized in that, The reaction products are cooled by a heat exchanger and then divided into two streams. A refrigerant inlet pipeline and a refrigerant outlet pipeline are provided on the heat exchanger. A refrigerant outlet control valve V3 is provided on the refrigerant outlet pipeline. Preferably, the opening degree of the refrigerant outlet control valve V3 is controlled by a first control module TIC.

5. The method according to claim 4, characterized in that, A temperature detector TE is installed at the mixer outlet. Both the temperature detector TE and the refrigerant discharge control valve V3 are electrically connected to the first control module TIC. Preferably, the temperature detector TE detects the material temperature at the discharge end of the mixer and transmits the material temperature to the first control module TIC, which then controls the opening of the refrigerant discharge valve V3 to control the refrigerant flow rate of the heat exchanger. More preferably, when the material temperature exceeds the set value, the first control module TIC controls the opening of the refrigerant discharge control valve V3 to increase until the material temperature returns to the set value; when the material temperature is lower than the set value, the first control module TIC controls the opening of the refrigerant discharge control valve V3 to decrease until the material temperature returns to the set value; wherein, the set value is 67±3℃.

6. The method according to claim 4, characterized in that, The real-time mass flow rate of the dispersion I is detected. When the mass flow rate of the dispersion I fluctuates, the detected real-time mass flow rate signal of the dispersion I is transmitted to the first control module TIC. The first control module TIC adjusts the required flow rate of the refrigerant to the heat exchanger according to equation (1) and adjusts the opening of the refrigerant discharge valve V3 in advance. m 冷媒 *C p冷媒 *▲T=A*m 二酸 *c 二酸 Equation (1) In equation (1), m 冷媒 The refrigerant discharge mass flow rate from the heat exchanger is expressed in kg / h; C p冷媒 ▲T represents the constant-pressure heat capacity of the refrigerant, kJ / (kg·K); ▲T represents the temperature difference between the refrigerant outlet and inlet, K; m 二酸 c is the real-time mass flow rate of dispersion I, kg / h; 二酸 The mass percentage of diacid in dispersion I is wt%; A is a coefficient, kJ / kg, and A is 1.40 to 1.60; preferably 1.45 to 1.

55.

7. The method according to claim 4, characterized in that, The feed molar ratio of the long-chain dicarboxylic acid to the long-chain diamine is controlled to be 1:(1-1.10), preferably 1:(1-1.08); Preferably, the reaction product is subjected to online near-infrared detection to obtain an online near-infrared detection signal, wherein the online near-infrared detection signal includes the real-time alkalinity value (pH) of the reaction product; More preferably, the real-time feed flow rate ratio K of dispersion II and dispersion I is adjusted according to the real-time alkalinity value pH obtained from the online near-infrared detection signal, and the mass flow rate of dispersion II is then controlled according to the real-time feed flow rate ratio K and the mass flow rate of dispersion I.

8. A system for continuous salt formation of long-chain polyamide, preferably used for the method described in any one of claims 1 to 7, the system comprising a mixer and a reactor, wherein a dispersion I feed line and a dispersion II feed line are provided at the feed end of the mixer, a mixture conveying line is provided between the discharge end of the mixer and the feed end of the reactor, a reaction product circulation line is provided between the discharge end of the reactor and the feed end of the mixer, and a reaction product external bypass line is provided on the reaction product circulation line.

9. The system according to claim 8, characterized in that, A heat exchanger is installed on the reaction product circulation pipeline (preferably before the reaction product external bypass pipeline along the material flow direction); preferably, a refrigerant inlet pipeline and a refrigerant outlet pipeline are installed on the heat exchanger, and a refrigerant flow regulating valve V3 is installed on the refrigerant outlet pipeline; and / or, The system further includes a first control module (TIC).

10. The system according to claim 9, characterized in that, A temperature detector TE is installed on the mixed material conveying pipeline to detect the material temperature from the discharge end of the mixer; preferably, the temperature detector TE and the refrigerant flow regulating valve V3 are both electrically connected to the first control module TIC.

11. The system according to claim 9, characterized in that, A mass flow meter FC1 for dispersion I is installed on the feed line of dispersion I to detect the real-time mass flow rate of dispersion I. A mass flow meter FC2 for dispersant II is installed on the feed line of dispersant II to detect the real-time mass flow rate of dispersant II. Preferably, the dispersion liquid I mass flow meter FC1 and the refrigerant flow regulating valve V3 are both electrically connected to the first control module TIC, preferably in the manner shown in equation (1).

12. The system according to claim 9, characterized in that, An online near-infrared detector is installed on the reaction product circulation pipeline to detect online near-infrared detection signals, including the real-time alkalinity value (pH) of the reaction product; and / or, A mass flow meter FC1 for dispersion I and a flow regulating valve for dispersion I are installed on the feed line of dispersion I; a mass flow meter FC2 for dispersion II and a flow regulating valve for dispersion II are installed on the feed line of dispersion II; and / or, The system further includes a second control module FY, used to adjust the mass flow rate of dispersion II based on the mass flow rate of dispersion I.

13. The system according to claim 12, characterized in that, The online near-infrared detector and the dispersion II flow regulating valve are each independently electrically connected to the second control module FY to obtain the real-time feed mass flow ratio K of dispersion II and dispersion I. Preferably, the dispersion I mass flow meter FC1, the dispersion II mass flow meter FC2, and the dispersion II flow regulating valve are each independently electrically connected to the second control module FY.

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