CN114702665B - Method for continuously preparing nylon - Google Patents

Method for continuously preparing nylon Download PDF

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Publication number
CN114702665B
CN114702665B CN202210350913.0A CN202210350913A CN114702665B CN 114702665 B CN114702665 B CN 114702665B CN 202210350913 A CN202210350913 A CN 202210350913A CN 114702665 B CN114702665 B CN 114702665B
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screw extruder
temperature
reaction
nylon
double
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CN114702665A (en
Inventor
王根林
吴健
徐志斌
丁克鸿
徐林
刘超
纪永春
高文博
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NINGXIA RUITAI TECHNOLOGY CO LTD
Jiangsu Yangnong Chemical Group Co Ltd
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NINGXIA RUITAI TECHNOLOGY CO LTD
Jiangsu Yangnong Chemical Group Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
    • C08G69/02—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids
    • C08G69/26—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from polyamines and polycarboxylic acids
    • C08G69/28—Preparatory processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/0046—Sequential or parallel reactions, e.g. for the synthesis of polypeptides or polynucleotides; Apparatus and devices for combinatorial chemistry or for making molecular arrays
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/0053—Details of the reactor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/0093—Microreactors, e.g. miniaturised or microfabricated reactors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00177—Controlling or regulating processes controlling the pH

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Polyamides (AREA)

Abstract

The invention provides a method for continuously preparing nylon, which comprises the following steps: (1) The diacid and diamine enter a micro-channel reactor to react, and a blocking agent is added in the reaction to obtain a solution after the reaction; (2) And sending the reacted solution into a first intermediate container, regulating and monitoring the pH value, sending the reacted solution with qualified pH value into a double-screw extruder unit, and cutting by a brace to obtain the nylon product. According to the method, the blocking agent is adopted, so that the decomposition problem caused by too fast reaction and too high temperature can be remarkably reduced, the micro-channel reactor is used, the heat removal amount can be timely transferred, the reaction time can be reduced as much as possible, and the continuous preparation of nylon is realized.

Description

Method for continuously preparing nylon
Technical Field
The invention relates to the technical field of nylon preparation, in particular to a method for continuously preparing nylon.
Background
Polyamide engineering Plastics (PA) are also known as nylons, and refer to linear thermoplastic polymers having amide group (-CONH) repeating structural units in the main chain. Is prepared by polycondensation of dibasic acid and diamine or amino acid. The amide groups of the nylon have polarity and form hydrogen bonds among molecules, so that the nylon has the excellent characteristics of toughness, wear resistance, impact resistance, fatigue resistance, corrosion resistance, oil resistance, solvent resistance, no toxicity, good self-extinguishing property, good electronic insulation property and the like. The device is mainly used for bearings, gears, turbines, automobile parts, oil pipes, oil tanks and the like in the aspects of mechanical instruments, automobiles, textiles and the like. Is one of the most widely used, fast-developed and most studied engineering plastics at present.
Nylon is called polyamide and nylon, which is formed by mutually and alternately polycondensating diamine molecules and diacid molecules. Nylon has excellent heat resistance and mechanical performance, high strength, high impact resistance and other features, and may be used widely in navigation, automobile, electric and electronic equipment, building, body building equipment, electric tool, industrial parts, farm machinery and other fields.
The most commonly used nylon polymerization processes at present include both nylon salt processes and melt polymerization processes. The nylon salt process generally comprises the steps of preparing a nylon salt solution in water or a strong polar organic solvent, removing water in a system under a certain temperature and pressure, and finally carrying out polycondensation under a molten state of the nylon salt to obtain the polyamide.
CN109180931a discloses a process for preparing long carbon chain nylon PA1313 and products, which is still a salt forming process in aqueous solution, by first forming salt in aqueous solution and then melt polycondensing process to prepare polyamide 1313. In the initial stage of melt polycondensation, a large amount of water is also added as a dispersing agent to ensure the stability of the quality of the final product, and the process has the following problems: 1) The nylon salt is prepared by a reaction kettle, and the process is complicated. 2) A large amount of water is consumed as a dispersion system, resulting in waste. 3) The added water is volatilized after vaporization in the polycondensation process, and a large amount of energy is consumed.
CN112062950a discloses a continuous nylon polymerization process, which uses molten polyamide as a solvent, so that the dispersed diacid and diamine directly generate salt and polymerization reaction in a polyamide dispersion system, and when one of the feed amounts changes, the material proportion is easily unbalanced, resulting in polymerization failure.
Therefore, development of a continuous nylon synthesis method capable of controlling the quality of nylon products more stably is needed.
Disclosure of Invention
In view of the problems in the prior art, the invention provides a method for continuously preparing nylon, which reduces the influence of too fast reaction on reaction temperature rise by adopting a method of combining a blocking agent and a microchannel reactor, thereby being capable of better controlling the quality of nylon products and realizing continuous production of nylon.
To achieve the purpose, the invention adopts the following technical scheme:
In a first aspect, the present invention provides a method for continuously preparing nylon, the method comprising the steps of:
(1) The diacid and diamine enter a micro-channel reactor to react, and a blocking agent is added in the reaction to obtain a solution after the reaction;
(2) And sending the reacted solution into a first intermediate container, regulating and monitoring the pH value, sending the reacted solution with qualified pH value into a double-screw extruder unit, and cutting by a brace to obtain the nylon product.
The preparation method provided by the invention can realize continuous production of nylon, and nylon products can be directly obtained through directly connecting the double screw extruder, and compared with products only prepared with nylon salt, the preparation method provided by the invention has the advantages of high production efficiency, low energy consumption, safety, environmental protection and the like.
Preferably, the diamine in step (1) comprises hexamethylenediamine.
Preferably, the diacid comprises adipic acid.
The diamine concentration is preferably 0.01 to 1000g/L, and may be, for example, 1g/L, 112g/L, 223g/L, 334g/L, 445g/L, 556g/L, 667g/L, 778g/L, 889g/L, 1000g/L, etc., but is not limited to the values recited, and other values not recited in the range are equally applicable, and preferably 500 to 800g/L.
The concentration of the diacid is preferably 0.01 to 1000g/L, and may be, for example, 1g/L, 112g/L, 223g/L, 334g/L, 445g/L, 556g/L, 667g/L, 778g/L, 889g/L, 1000g/L, or the like, but not limited to the values recited, other values not recited in the range are equally applicable, and preferably 500 to 800g/L.
The temperature of the reaction in the step (1) is preferably 30 to 220 ℃, and may be, for example, 30 ℃, 52 ℃, 73 ℃, 94 ℃, 115 ℃, 136 ℃, 157 ℃, 178 ℃, 199 ℃, 220 ℃, or the like, but is not limited to the values recited, and other values not recited in the range are equally applicable.
The residence time of the reaction is preferably 0.5 to 60min, and may be, for example, 0.5min, 8min, 15min, 21min, 28min, 34min, 41min, 47min, 54min or 60min, etc., but is not limited to the recited values, and other non-recited values within this range are equally applicable, preferably 3 to 5min.
Preferably, the capping agent in step (1) comprises a monoamine and/or a monoacid.
The amount of the blocking agent added is preferably 0.01 to 0.05% by weight of the total amount of the diacid and diamine, and may be, for example, 0.01%, 0.02%, 0.03%, 0.04%, or 0.05%, etc., but is not limited to the values recited, and other values not recited in the range are equally applicable.
Preferably, the monoamine comprises an aliphatic amine and/or an aniline.
Preferably, the aliphatic amine comprises any one or a combination of at least two of methylamine, ethylamine, hexylamine, or propylamine, wherein typical but non-limiting combinations are combinations of methylamine and ethylamine, combinations of propylamine and ethylamine, combinations of methylamine and propylamine, and combinations of hexylamine and propylamine.
Preferably, the mono-acid comprises an aliphatic acid and/or a benzoic acid.
Preferably, the aliphatic acid comprises any one or a combination of at least two of formic acid, acetic acid, caproic acid, propionic acid or butyric acid, wherein typical but non-limiting combinations are combinations of formic acid and acetic acid, propionic acid and acetic acid, formic acid and butyric acid.
The end capping agent is preferably added, so that the problem of product decomposition caused by rapid reaction heat release can be reduced, and the quality of a final product is improved.
Preferably, the monoamine has the same number of carbon atoms as the diamine.
Preferably, the number of carbon atoms of the mono-acid is the same as the number of carbon atoms of the di-acid.
According to the invention, the blocking agent is selected according to the principle, so that a product with narrower molecular weight distribution can be obtained, and the product performance is more uniform.
Preferably, when the pH value is regulated and monitored in the step (2), the second intermediate container is switched when the pH value is disqualified, diamine or diacid is added into the first intermediate container to regulate the pH value until the pH value is qualified, and the material with the regulated pH value is recycled to the microchannel reactor.
Preferably, the pH is controlled between 7.5 and 7.65, for example, 7.5, 7.52, 7.53, 7.54, 7.55, 7.58, 7.6, 7.62 or 7.65, etc., but not limited to the recited values, other non-recited values within the range are equally applicable.
Preferably, in the twin-screw extruder set in the step (2), a first twin-screw extruder and a second twin-screw extruder are provided.
Preferably, the polyamide is preheated by the first twin-screw extruder before entering the second twin-screw extruder.
The molecular weight of the polyamide is preferably 10000 to 30000, and may be 10000, 12000, 13000, 15000, 18000, 20000, 25000, 28000, 30000, or the like, for example, but not limited to the recited values, and other non-recited values within the range are equally applicable.
The temperature after the first twin-screw extruder is preheated is preferably 265 to 275 ℃, and may be 265 ℃, 267 ℃, 268 ℃, 269 ℃, 270 ℃, 271 ℃, 272 ℃, 273 ℃, 274 ℃, 275 ℃, or the like, for example, but not limited to the values recited, and other values not recited in the range are equally applicable.
Preferably, the post-reaction solution in step (2) is fed into a second twin-screw extruder.
Preferably, the mass ratio of the reacted solution in the feed of the second twin-screw extruder to the feed of the first twin-screw extruder is 100:10-0.1, for example, it may be 100:10, 100:9, 100:8, 100:7, 100:6, 100:5, 100:4, 100:3, 100:2, 100:1 or 100:0.1, etc., but not limited to the recited values, and other non-recited values in this range are equally applicable.
Preferably, the residence time of the material in the second twin-screw extruder is 1 to 20min, for example, 1min, 4min, 6min, 8min, 10min, 12min, 14min, 16min, 18min or 20min, etc., but not limited to the recited values, and other values not recited in the range are equally applicable.
Preferably, at least 7 temperature zones are provided in the second twin screw extruder in step (2).
The temperature in the first temperature zone is preferably 250 to 260 ℃, and may be 250 to 252 ℃, 253 ℃, 254 ℃, 255 ℃, 256 ℃, 257 ℃, 258 ℃, 259 ℃, 260 ℃ or the like, for example, but not limited to the values recited, and other values not recited in the range are equally applicable.
The second temperature range is preferably 260 to 270 ℃, and may be 260 to 262 ℃, 263 ℃, 264 ℃, 265 ℃, 266 ℃, 267 ℃, 268 ℃, 269 ℃, 270 ℃ or the like, for example, but not limited to the values recited, and other values not recited in the range are equally applicable.
The temperature in the third temperature zone is preferably 265 to 275 ℃, and may be 265 ℃, 267 ℃, 268 ℃, 269 ℃, 270 ℃, 271 ℃, 272 ℃, 273 ℃, 274 ℃, 275 ℃ or the like, for example, but not limited to the values recited, and other values not recited in the range are equally applicable.
The temperature in the fourth temperature zone is preferably 270 to 280 ℃, and may be 270 ℃, 272 ℃, 273 ℃, 274 ℃, 275 ℃, 276 ℃, 277 ℃, 278 ℃, 279 ℃, 280 ℃ or the like, for example, but not limited to the values recited, and other values not recited in the range are equally applicable.
The temperature in the fifth temperature zone is preferably 275 to 285 ℃, and may be 275 ℃, 277 ℃, 278 ℃, 279 ℃, 280 ℃, 281 ℃, 282 ℃, 283 ℃, 284 ℃, 285 ℃, or 285 ℃, for example, but the present invention is not limited to the values listed, and other values not listed in the range are equally applicable.
The sixth temperature range is preferably 265 to 275 ℃, and may be 265 ℃, 267 ℃, 268 ℃, 269 ℃, 270 ℃, 271 ℃, 272 ℃, 273 ℃, 274 ℃, 275 ℃, or the like, for example, but not limited to the values recited, and other values not recited in the range are equally applicable.
The seventh temperature range is preferably 260 to 270 ℃, and may be, for example, 260 ℃, 262 ℃, 263 ℃, 264 ℃, 265 ℃, 266 ℃, 267 ℃, 268 ℃, 269 ℃, 270 ℃, or the like, but is not limited to the values recited, and other values not recited in the range are equally applicable.
Preferably, at least four vacuum ports are provided in the second twin screw extruder in step (2).
The vacuum degree of each vacuum port is preferably independently-0.01 to-0.09 MPa, for example, -0.01MPa, -0.02MPa, -0.03MPa, -0.04MPa, -0.05MPa, -0.06MPa, -0.07MPa, -0.08MPa or-0.09 MPa, etc., but not limited to the values recited, and other values not recited in the range are equally applicable.
As a preferred technical scheme of the invention, the method comprises the following steps:
(1) The diacid with the concentration of 0.01-1000 g/L and diamine with the concentration of 0.01-1000 g/L enter a micro-channel reactor to react at 30-220 ℃, a blocking agent is added simultaneously in the reaction, the addition amount of the blocking agent accounts for 0.01-0.05% of the total amount of the diacid and the diamine, and the residence time of the reaction is 0.5-60 min, so as to obtain a solution after the reaction;
(2) And (2) sending the reacted solution into a first intermediate container, regulating and monitoring the pH value, switching a second intermediate container when the pH value is unqualified, adding diamine or diacid into the first intermediate container, regulating the pH value to be qualified, then circulating the material with the regulated pH value into a micro-channel reactor, sending the reacted solution with the qualified pH value into a second double-screw extruder, preheating polyamide to 265-275 ℃ by the first double-screw extruder, then sending the polyamide into the second double-screw extruder, wherein the feeding mass ratio of the reacted solution to the first double-screw extruder is 100:10-0.1, the retention time of the material in the second double-screw extruder is 1-20 min, 7 sections of temperature sections are arranged in the second double-screw extruder, the temperature ranges from 250 ℃ to 260 ℃ to 270 ℃, the temperature ranges from 265 ℃ to 275 ℃ and the temperature ranges from 260 ℃ to 270 ℃, and four vacuum ports are respectively arranged in the second double-screw extruder, and the vacuum degree of each vacuum port is respectively and independently from-0.01 MPa to-0.09 MPa by cutting to obtain nylon products.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) The continuous nylon preparation method provided by the invention can realize continuous nylon production;
(2) The nylon product prepared by the continuous preparation method provided by the invention has excellent performance, low yellow index, tensile strength of more than 74MPa below-1, narrow molecular weight distribution, molecular weight span of less than 11000 and uniform and stable performance.
Drawings
FIG. 1 is a schematic diagram of an apparatus used in the continuous nylon production method according to example 1 of the present invention.
In the figure: 1. a diacid storage device; 2. diamine storage means; 3. a first pump; 4. a second pump; 5. a microchannel reactor; 6. a pH adjuster storage device; 7. a first intermediate container; 8. a pH detecting section; 9. a second intermediate container; 10. a third pump; 11. a polyamide silo; 12. a first twin screw extruder; 13. a second twin screw extruder; 14. a water storage device; 15. a vacuum port; 16. and (5) a granulator.
Detailed Description
The technical scheme of the invention is further described below by the specific embodiments with reference to the accompanying drawings.
The present invention will be described in further detail below. The following examples are merely illustrative of the present invention and are not intended to represent or limit the scope of the invention as defined in the claims.
It is to be understood that in the description of the present invention, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first", "a second", etc. may explicitly or implicitly include one or more such feature. In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.
It should be noted that, in the description of the present invention, unless explicitly specified and limited otherwise, the terms "disposed," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art in a specific case.
Example 1
The embodiment provides a method for continuously preparing nylon, which comprises the following steps:
An apparatus for continuously preparing nylon is assembled according to the schematic diagram of fig. 1, and comprises a diacid storage device 1 and a diamine storage device 2 which are respectively connected with a micro-channel reactor 5 through a first pump 3 and a second pump 4, wherein the diacid storage device 1 is provided with a diacid inlet and a water inlet; a diamine inlet is arranged on the diamine storage device 2; the device also comprises a first intermediate container 7 and a second intermediate container 9 which are connected in parallel with the outlet of the microchannel reactor 5, wherein the first intermediate container 7 is provided with a pH detection component 8; the upper part of the second intermediate container 9 is connected with a pH regulator storage device 6; the outlet of the second intermediate container 9 is circularly connected with the middle inlet of the microchannel reactor 5 through a third pump 10; the device also comprises a second double-screw extruder 13 connected with the outlet of the first intermediate container 7, 4 vacuum ports 15 are arranged on the second double-screw extruder 13, the inlet of the second double-screw extruder 13 is also connected with a first double-screw extruder 12, the upper part of the first double-screw extruder 12 is provided with a polyamide storage bin 11, and the outlet of the second double-screw extruder 13 is sequentially connected with a water storage device 14 and a granulator 16, and the specific method comprises the following steps:
(1) Starting the first double-screw extruder and the second double-screw extruder, and controlling the feeding amount of nylon 66 in the first double-screw extruder to be 50g/min until the second double-screw extruder has fluid extrusion, wherein the residence time of materials in the second double-screw extruder is 20min;
Adipic acid is prepared into adipic acid solution with the concentration of 600g/L, the adipic acid solution is heated to be completely dissolved, then the adipic acid solution and hexamethylenediamine with the concentration of 600g/L (two materials are reacted in a microchannel reactor according to the ratio of n (adipic acid): n (hexamethylenediamine) =1:1 and the total mass of 2.5 g/min) at 220 ℃, caproic acid (mixed with adipic acid) is added into the reaction as a blocking agent, the adding amount of the blocking agent accounts for 0.01 percent of the total amount of adipic acid and hexamethylenediamine, and the residence time of the reaction is 2min, so that a solution after the reaction is obtained;
(2) The solution after reaction is sent into a first intermediate container to be regulated and monitored whether the pH value is between 7.5 and 7.65, a second intermediate container is switched when the pH value is unqualified, hexamethylenediamine or adipic acid is added into the first intermediate container to regulate the pH value to be qualified, then the material with the regulated pH value is circulated into a micro-channel reactor, the solution after the reaction with the qualified pH value is sent into a second double-screw extruder, polyamide (nylon 66, molecular weight 2200035000) is preheated to 265 ℃ by the first double-screw extruder and then enters the second double-screw extruder, the retention time of the material in the second double-screw extruder is 20min, 7 sections of temperature sections are arranged in the second double-screw extruder, 255 ℃, 265 ℃, 275 ℃, 280 ℃, 270 ℃ and 265 ℃, four vacuum ports are arranged in the second double-screw extruder, and the vacuum degree of each vacuum port is minus 0.02MPa, -0.02MPa, 0.05MPa and 0.08MPa in sequence, and nylon products are obtained by strand dicing.
Example 2
The embodiment provides a method for continuously preparing nylon, which comprises the following steps:
(1) Starting the first double-screw extruder and the second double-screw extruder, and controlling the feeding amount of nylon 66 in the first double-screw extruder to be 20g/min until the second double-screw extruder has fluid extrusion, wherein the retention time of materials in the second double-screw extruder is 15min;
Adipic acid is prepared into adipic acid solution with the concentration of 500g/L, the adipic acid solution is heated to be completely dissolved, then the adipic acid solution and hexamethylenediamine with the concentration of 500g/L (two materials are reacted in a micro-channel reactor according to the ratio of n (adipic acid): n (hexamethylenediamine) =1:1 and the total mass of 2.0 g/min) at 200 ℃, caproic acid is added into the reaction as a blocking agent, the addition amount of the blocking agent accounts for 0.02 percent of the total amount of adipic acid and hexamethylenediamine, and the residence time of the reaction is 3min, so that a reacted solution is obtained;
(2) The method comprises the steps of feeding a solution after reaction into a first intermediate container, adjusting and monitoring whether the pH value is between 7.6 and 7.65, switching a second intermediate container when the pH value is unqualified, adding hexamethylenediamine or adipic acid into the first intermediate container, adjusting the pH value to be qualified, circulating the material after adjusting the pH value into a micro-channel reactor, feeding the solution after the reaction into a second double-screw extruder after the pH value is qualified, preheating polyamide (nylon 66) to 270 ℃ through the first double-screw extruder, feeding the polyamide into the second double-screw extruder, cutting nylon granules into nylon granules, wherein the feeding mass ratio of the solution after the reaction to the first double-screw extruder is 100:10, the retention time of the material in the second double-screw extruder is 15min, 7 sections of temperature sections are arranged in the second double-screw extruder, respectively at 255 ℃, 265 ℃, 270 ℃, 275 ℃, 280 ℃ and 265 ℃, and four vacuum ports are arranged in the second double-screw extruder, and the vacuum degree of each vacuum port is respectively at-0.01 MPa, -0.02MPa, 0.06MPa and 0.09MPa, and the nylon granules are cut, so that nylon products are obtained.
Example 3
The embodiment provides a method for continuously preparing nylon, which comprises the following steps:
(1) Starting the first double-screw extruder and the second double-screw extruder, and controlling the feeding amount of nylon 66 in the first double-screw extruder to be 15g/min until the second double-screw extruder has fluid extrusion, wherein the retention time of materials in the second double-screw extruder is 10min;
preparing adipic acid into adipic acid solution with the concentration of 800g/L, heating to be completely dissolved, then, introducing the adipic acid solution and hexamethylenediamine with the concentration of 800g/L (two materials are mixed according to n (adipic acid): n (hexamethylenediamine) =1:1 and the total mass of 0.15 g/min) into a microchannel reactor for carrying out 180 ℃ reaction, wherein propylamine is simultaneously added as a blocking agent in the reaction, the addition amount of the blocking agent accounts for 0.05% of the total amount of adipic acid and hexamethylenediamine, and the residence time of the reaction is 10min, so as to obtain a reacted solution;
(2) The method comprises the steps of feeding a solution after reaction into a first intermediate container, adjusting and monitoring whether the pH value is between 7.5 and 7.55, switching a second intermediate container when the pH value is unqualified, adding hexamethylenediamine or adipic acid into the first intermediate container, adjusting the pH value to be qualified, circulating the material after adjusting the pH value into a micro-channel reactor, feeding the solution after the reaction into a second double-screw extruder after the pH value is qualified, preheating polyamide (nylon 66) to 275 ℃ through the first double-screw extruder, feeding the polyamide into the second double-screw extruder, enabling the feeding mass ratio of the solution after the reaction to the first double-screw extruder to be 100:1, enabling the retention time of the material in the second double-screw extruder to be 10min, arranging 7 sections of temperature sections in the second double-screw extruder, wherein the temperature sections are respectively 255 ℃, 265 ℃, 270 ℃, 275 ℃, 280 ℃, 265 ℃ and 270 ℃, arranging four vacuum ports in the second double-screw extruder, and cutting nylon products after the vacuum degree of each vacuum port is respectively-0.02 MPa, -0.03MPa, 0.04MPa and 0.07MPa, and obtaining nylon products through brace cutting.
Example 4
This example provides a continuous process for preparing nylon except for the provision of 600g/L of adipic acid solution and two supplies according to n (adipic acid): n (hexamethylenediamine) =1:1, the remainder being the same as in example 1, except that the total mass is 5 g/min.
Example 5
This example provides a continuous process for preparing nylon except for the provision of 600g/L of adipic acid solution and two supplies according to n (adipic acid): n (pentylenediamine) =1:1, except that the total mass was 5g/min, the first twin screw extruder fed nylon 56, the resulting product was synthetic virgin nylon 56, and the remainder was the same as in example 1.
Example 6
This example provides a continuous process for preparing nylon except for the provision of 600g/L of adipic acid solution and two supplies according to n (adipic acid): n (pentylenediamine) =1:1, except that the total mass was 2.5g/min, the first twin-screw extruder was fed with nylon 56, the resulting product was synthetic virgin nylon 56, and the remainder was the same as in example 1.
Example 7
This example provides a continuous process for preparing nylon which is the same as example 4 except that the residence time of the second twin screw extruder is 10 minutes.
Example 8
This example provides a continuous process for preparing nylon which is the same as example 1 except that caproic acid is replaced with hexylamine (mixed with hexamethylenediamine).
Example 9
This example provides a continuous process for preparing nylon which is the same as example 1 except that caproic acid is replaced with formic acid (mixed with adipic acid).
Comparative example 1
This comparative example provides a method for preparing nylon comprising weighing ultrapure water, caproic acid, adipic acid and hexamethylenediamine (in the same proportions as in example 1) and adding into a reaction kettle, and salifying for 20min when the temperature in the kettle is raised to 80 ℃. When the pressure in the kettle rises to 0.25MPa, salt solution concentration is carried out, 75% of water is removed, the valve is closed, and the temperature is continuously raised. When the pressure in the kettle rises to 1.8MPa, maintaining for 30min, and controlling the temperature to 270 ℃; opening a vacuum pump until the pressure in the kettle is-0.07 MPa; after the melt stably flows out, the melt is pulled to a water tank, cooled by the water tank and enters a granulator for granulating.
Comparative example 2
This comparative example provides a continuous process for preparing nylon, which is the same as example 1, except that no hexanoic acid is added.
The testing method comprises the following steps: the procedure described above for the conversion of nylon salt to nylon product in the other examples and comparative examples was performed with reference to the procedure described in example 1, and the yellow index of the final nylon product was tested using the HG/T3862 method. GB/T1039-1992 plastic mechanical property test method for testing tensile strength of nylon; molecular weight of nylon was measured by GPC.
The test results of the above examples and comparative examples are shown in table 1.
TABLE 1
Yellow index Tensile Strength (MPa) Molecular weight Molecular weight distribution range
Example 1 -1 76 30000 25000～33000
Example 2 -3 75 31000 26000～33000
Example 3 -2 74 29000 24000～33000
Example 4 -1 78 29000 24000～32000
Example 5 -1 75 31000 26000～34000
Example 6 -1 76 30000 25000～33000
Example 7 -1 76 29000 24000～33000
Example 8 -1 75 29000 24000～33000
Example 9 -1 74 31000 23000～34000
Comparative example 1 0 72 31000 20000～37000
Comparative example 2 0 73 35000 22000～43000
From table 1, the following points can be seen:
(1) According to the method for continuously preparing nylon, disclosed by the invention, the influence of too fast reaction on reaction temperature rise is reduced by adopting a method of combining a blocking agent and a microchannel reactor, so that the quality of a nylon product can be well controlled, wherein the yellow index of nylon is below-1, the tensile strength is above 74MPa, the molecular weight distribution is narrow, and the molecular weight span is within 11000;
(2) As can be seen from the combination of example 1 and comparative example 1, in example 1, the reaction residence time in example 1 is only 2min, whereas in comparative example 1, the reaction time is required to be kept for 30min, and continuous production is impossible, and the yellow index of the product in example 1 is only-1, while the yellow index in comparative example 1 is 0, and the molecular weight distribution range in example 1 is narrower, in the range of 25000 to 33000, while the molecular weight distribution range in comparative example 1 is wide, up to 20000 to 37000, and finally the tensile strength of the product in comparative example 1 is also lower than that in example 1, thus showing that the invention significantly improves the product performance of nylon by using the microchannel reactor in combination with the end-capping agent;
(3) It can be seen from the combination of example 1 and comparative example 2 that the addition of the capping agent in example 1 also employs a microchannel reactor compared to the absence of the capping agent in comparative example 1, and the yellowness index and molecular weight distribution in example 1 are narrower, thus indicating that the combination of the capping agent and the microchannel reactor in the present invention significantly improves the performance of the product;
(4) As can be seen from a combination of examples 1 and 9, the addition of caproic acid as the capping agent in example 1 provides a narrower molecular weight distribution and a higher tensile strength of the product obtained by the raw materials of caproic acid and adipic acid in example 1 than the addition of formic acid as the capping agent in example 9, and thus shows that the invention has a better molecular weight control effect by selecting the capping agent having the same carbon number as that of diacid and diamine.
The detailed structural features of the present invention are described in the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be apparent to those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope of the present invention and the scope of the disclosure.

Claims (19)

1. A method for continuously preparing nylon, comprising the steps of:
(1) The diacid and diamine enter a micro-channel reactor to react, and a blocking agent is added in the reaction to obtain a solution after the reaction; the diamine is hexamethylenediamine, and the diacid is adipic acid;
(2) The solution after the reaction is sent into a first intermediate container to regulate and monitor the pH value, and the solution after the reaction with qualified pH value is sent into a double screw extruder set and is subjected to bracing and cutting to obtain nylon products;
The end capping agent is caproic acid;
the addition amount of the end capping agent accounts for 0.01-0.05% of the total mass of the diacid and the diamine;
The molecular weight distribution of nylon products is narrow, and the molecular weight span is within 11000.
2. The method according to claim 1, wherein the diamine has a concentration of 0.01 to 1000g/L.
3. The method according to claim 2, wherein the diamine has a concentration of 500 to 800g/L.
4. The method of claim 1, wherein the concentration of the diacid is 0.01-1000 g/L.
5. The method of claim 4, wherein the concentration of the diacid is 500-800 g/L.
6. The method according to claim 1 or 2, wherein the temperature of the reaction in step (1) is 30-220 ℃.
7. The method according to claim 1 or 2, wherein the residence time of the reaction is 0.5-60 min.
8. The method of claim 7, wherein the residence time of the reaction is 3 to 5 minutes.
9. The method according to any one of claims 1 to 4, wherein in the step (2), when the pH is adjusted and monitored, the second intermediate container is switched when the pH is not acceptable, diamine or diacid is added to the first intermediate container to adjust the pH until the pH is acceptable, and the material after the adjustment of the pH is recycled to the microchannel reactor.
10. The method according to any one of claims 1 to 5, wherein in the twin-screw extruder set in step (2), a first twin-screw extruder and a second twin-screw extruder are provided.
11. The method of claim 10, wherein the polyamide is preheated by a first twin screw extruder before entering the second twin screw extruder.
12. The method of claim 10, wherein the temperature of the first twin screw extruder after preheating is 265-275 ℃.
13. The process of claim 10, wherein the post-reaction solution of step (2) is fed into a second twin screw extruder.
14. The method of claim 13, wherein the feed mass ratio of the reacted solution in the feed of the second twin-screw extruder to the feed of the first twin-screw extruder is 100:10-0.1.
15. The method of claim 13, wherein the residence time of the material in the second twin screw extruder is 1 to 20 minutes.
16. The method of claim 10, wherein at least 7 temperature zones are provided in the second twin screw extruder in step (2);
The temperature of the first temperature section is 250-260 ℃;
The temperature of the second temperature section is 260-270 ℃;
the temperature of the third temperature section is 265-275 ℃;
the temperature of the fourth temperature section is 270-280 ℃;
the temperature of the fifth temperature section is 275-285 ℃;
the temperature of the sixth temperature section is 265-275 ℃;
the temperature of the seventh temperature section is 260-270 ℃.
17. The method of claim 10, wherein at least four vacuum ports are provided in the second twin screw extruder in step (2).
18. The method of claim 17, wherein the vacuum level of each vacuum port is independently-0.01 to-0.09 MPa.
19. The method according to claim 1, characterized in that it comprises the steps of:
(1) Adipic acid with the concentration of 0.01-1000 g/L and hexamethylenediamine with the concentration of 0.01-1000 g/L enter a microchannel reactor to carry out a reaction at 30-220 ℃, a blocking agent is added simultaneously in the reaction, the addition amount of the blocking agent accounts for 0.01-0.05% of the total mass of diacid and diamine, the blocking agent is caproic acid, the reaction residence time is 0.5-60 min, and a solution after the reaction is obtained;
(2) And (2) sending the reacted solution into a first intermediate container, regulating and monitoring the pH value, switching a second intermediate container when the pH value is unqualified, adding diamine or diacid into the first intermediate container, regulating the pH value to be qualified, then circulating the material with the regulated pH value into a micro-channel reactor, sending the reacted solution with the qualified pH value into a second double-screw extruder, preheating polyamide to 265-275 ℃ by the first double-screw extruder, then sending the polyamide into the second double-screw extruder, wherein the feeding mass ratio of the reacted solution to the first double-screw extruder is 100:10-0.1, the retention time of the material in the second double-screw extruder is 1-20 min, 7 sections of temperature sections are arranged in the second double-screw extruder, the temperature ranges of 250-260 ℃ and 260-270 ℃ respectively, the temperature ranges of 265-275 ℃, the temperature ranges of 270-280 ℃ and the temperature ranges of 275-285 ℃, the vacuum degree of each vacuum port is respectively and independently-0.01-0.09 MPa, and cutting the nylon product is obtained by bracing.
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