CN115894249A - Preparation method of nylon 66 salt and nylon 66 prepared by preparation method - Google Patents
Preparation method of nylon 66 salt and nylon 66 prepared by preparation method Download PDFInfo
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- CN115894249A CN115894249A CN202211506478.2A CN202211506478A CN115894249A CN 115894249 A CN115894249 A CN 115894249A CN 202211506478 A CN202211506478 A CN 202211506478A CN 115894249 A CN115894249 A CN 115894249A
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- nylon
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- adipic acid
- hexamethylenediamine
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- 229920002302 Nylon 6,6 Polymers 0.000 title claims abstract description 259
- 150000003839 salts Chemical class 0.000 title claims abstract description 138
- 238000002360 preparation method Methods 0.000 title claims abstract description 36
- NAQMVNRVTILPCV-UHFFFAOYSA-N hexane-1,6-diamine Chemical compound NCCCCCCN NAQMVNRVTILPCV-UHFFFAOYSA-N 0.000 claims abstract description 206
- 239000000243 solution Substances 0.000 claims abstract description 186
- WNLRTRBMVRJNCN-UHFFFAOYSA-N adipic acid Chemical compound OC(=O)CCCCC(O)=O WNLRTRBMVRJNCN-UHFFFAOYSA-N 0.000 claims abstract description 166
- 239000001361 adipic acid Substances 0.000 claims abstract description 82
- 235000011037 adipic acid Nutrition 0.000 claims abstract description 82
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 61
- 238000000034 method Methods 0.000 claims abstract description 55
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- 238000006068 polycondensation reaction Methods 0.000 claims abstract description 21
- 239000012045 crude solution Substances 0.000 claims abstract description 20
- 238000007670 refining Methods 0.000 claims abstract description 3
- 238000006243 chemical reaction Methods 0.000 claims description 111
- 239000012266 salt solution Substances 0.000 claims description 54
- 239000007787 solid Substances 0.000 claims description 49
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 41
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- 230000035484 reaction time Effects 0.000 claims description 4
- 229910052799 carbon Inorganic materials 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims 1
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 6
- 229910017604 nitric acid Inorganic materials 0.000 description 6
- 238000010998 test method Methods 0.000 description 6
- 239000002253 acid Substances 0.000 description 5
- 238000002411 thermogravimetry Methods 0.000 description 5
- 239000004952 Polyamide Substances 0.000 description 4
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- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 239000004677 Nylon Substances 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
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- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
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- 239000001307 helium Substances 0.000 description 1
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- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- SYECJBOWSGTPLU-UHFFFAOYSA-N hexane-1,1-diamine Chemical compound CCCCCC(N)N SYECJBOWSGTPLU-UHFFFAOYSA-N 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 229910052754 neon Inorganic materials 0.000 description 1
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention relates to the technical field of preparation of nylon 66 salt, and particularly discloses a preparation method of nylon 66 salt and nylon 66 prepared by the preparation method. The method comprises the following steps: dissolving adipic acid in water to prepare an adipic acid solution; dissolving hexamethylene diamine in water to prepare a hexamethylene diamine solution; taking a certain amount of hexamethylenediamine solution, dropwise adding the hexamethylenediamine solution into an adipic acid solution under the stirring of water bath at 40-60 ℃ to obtain a carboxyl-terminated intermediate solution; taking a certain amount of adipic acid solution, dropwise adding the adipic acid solution into a hexamethylenediamine solution under the stirring of a water bath at the temperature of 30-40 ℃ to obtain an amino-terminated intermediate solution; dropwise adding the amino-terminated intermediate solution into the carboxyl-terminated intermediate solution under the stirring condition of 30-60 ℃, and completely reacting to obtain a nylon 66 salt crude solution; introducing inert gas all the time; refining to obtain nylon 66 salt. The prepared nylon 66 salt has high purity and low UV index, is convenient to store and transport, is beneficial to synthesizing nylon 66 by polycondensation, and is easier to obtain high-quality nylon 66.
Description
Technical Field
The invention belongs to the technical field of preparation of nylon 66 salt, and particularly relates to a preparation method of nylon 66 salt and nylon 66 prepared by the preparation method.
Background
Nylon, also known as Polyamide (PA), is a generic name for polymers containing recurring amide groups in the molecular main chain. The nylon can be prepared by condensation polymerization of diamine and dibasic acid, and various polyamides can be prepared according to the difference of carbon atoms in the diamine and the dibasic acid, wherein the varieties of the polyamides are dozens, and the polyamide-66 (namely the nylon 66) has excellent comprehensive performance, excellent mechanical property, heat resistance, wear resistance and self-lubricating property, and can be widely applied to the fields of automobile industry, electronic and electrical industry, clothing, decoration, building materials and the like.
The nylon 66 salt is a monomer of nylon 66, and in order to ensure that diamine and diacid react at an equal molar ratio to obtain high molecular weight nylon 66 in the process of synthesizing nylon 66, diamine and diacid are generally synthesized into nylon 66 salt first, and then the polycondensation reaction for producing nylon 66 is carried out, so that side reactions such as amine volatilization, decarboxylation and the like in the polycondensation process are prevented.
The preparation of nylon 66 salt is divided into an aqueous solution method and a solvent crystallization method. The most common aqueous solution method is to dissolve or disperse the dibasic acid and the diamine in water respectively, then mix the dibasic acid and the diamine for neutralization reaction, judge the reaction end point according to the pH value of the mixed solution, and obtain the nylon 66 salt through the processes of separation, purification, drying and the like after the reaction is finished. In the salt-forming process, the free diamine is gradually reduced along with the reaction until the salt-forming reaction is finished. However, if the diacid and diamine are not uniformly mixed during the reaction process, the content of unreacted free diamine in the produced nylon 66 salt product is too high, which has a serious influence on the quality of the nylon 66 salt. In addition, because the amine is unstable in air, side reactions are easy to occur when the amine is heated or oxygen is generated, the quality of the nylon 66 salt is deteriorated, the color is yellow, and the changes can generate adverse effects on the polymerization of the nylon 66 salt, thereby seriously affecting the quality of the polymer nylon 66. Therefore, in order to obtain high-quality nylon 66, it is necessary to ensure that the polymerized monomeric nylon 66 salt has a high purity with less impurities.
Disclosure of Invention
Aiming at the problems in the existing preparation process of the nylon 66 salt, the invention provides a preparation method of the nylon 66 salt and the nylon 66 prepared by the preparation method, the nylon 66 salt prepared by the preparation method has less impurities and high purity, and the polycondensation product of the nylon 66 salt, namely the nylon 66, has high relative viscosity and excellent performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of nylon 66 salt comprises the following steps:
(1) Dissolving adipic acid in water to prepare an adipic acid solution; dissolving hexamethylene diamine in water to prepare a hexamethylene diamine solution;
(2) Dropwise adding a certain amount of the hexamethylenediamine solution into a certain amount of the adipic acid solution under the protection of inert gas and the stirring condition of a water bath at 40-60 ℃ to obtain a carboxyl-terminated intermediate solution;
(3) Dropwise adding a certain amount of the adipic acid solution into a certain amount of the hexamethylenediamine solution under the protection of inert gas and the stirring condition of a water bath at 30-40 ℃ to obtain an amino-terminated intermediate solution;
(4) Dropwise adding the amino-terminated intermediate solution into the carboxyl-terminated intermediate solution under the stirring condition of 30-60 ℃ under the protection of inert gas, and completely reacting to obtain a nylon 66 salt crude solution;
(5) And refining the crude solution of the nylon 66 salt to obtain a nylon 66 salt solid.
In the preparation process of the nylon 66 salt, the hexamethylenediamine solution is dropwise added into an adipic acid solution with the same molar quantity or excessive amount as the hexamethylenediamine in the step (2) to obtain a carboxyl-terminated intermediate solution, the reaction temperature is strictly controlled within the range of 40-60 ℃, the hexamethylenediamine is oxidized due to overhigh temperature to influence the quality of the generated nylon 66 salt, and the reaction rate is slow due to overlow temperature to further influence the reaction. In addition, the usage amount of the hexamethylene diamine in the step is less, the temperature can be properly increased within the range of 40-60 ℃, the hexamethylene diamine can be ensured not to be oxidized, and the reaction rate can be properly increased. The reaction of this step is as follows:
then, step (3) of adding the adipic acid solution dropwise to a solution of hexamethylenediamine in an equimolar or excess amount to adipic acid gives an amine-terminated intermediate solution, and for the same reason, the reaction temperature is strictly controlled. In addition, the amount of hexamethylenediamine used in this step is large, and the temperature needs to be controlled to be lower than that in step (2) by 30 ℃ to 40 ℃ to ensure that hexamethylenediamine is not easily oxidized. The reaction of this step is as follows:
and (3) in the step (4), the amino-terminated intermediate solution is dropwise added into the carboxyl-terminated intermediate solution to obtain a crude nylon 66 salt solution, and the temperature is controlled within the range of 30-60 ℃ in the step to ensure the product quality. The reaction of this step is as follows:
compared with the prior art, the preparation method of the nylon 66 salt has at least the following beneficial effects:
1. in the preparation method, firstly, a hexamethylenediamine solution is dropwise added into an adipic acid solution with the same molar amount as or excessive hexamethylenediamine to obtain a carboxyl-terminated intermediate solution; dripping the adipic acid solution into a hexamethylenediamine solution with the same molar quantity or excessive amount as adipic acid to obtain an amino-terminated intermediate solution, and dripping the amino-terminated intermediate solution into a carboxyl-terminated intermediate solution to obtain a nylon 66 salt crude solution. By the segmented dropwise adding method, the oxidation of the hexanediamine can be effectively inhibited, the side reaction is less, the preparation speed can be increased, the operation is easy, and the efficiency and the success rate can be improved.
2. The nylon 66 prepared by the method has the advantages of less impurities, high purity, low UV index and pseudo nitric acid content, convenient storage and transportation, favorable synthesis of nylon 66 polymer by polycondensation reaction, and easier obtainment of high-quality nylon 66 polymer.
In one embodiment, in step (1), the concentration of the adipic acid solution is 40 to 60wt%, and the concentration of the hexamethylenediamine solution is 40 to 60wt%.
Preferably, the concentration of the adipic acid solution is 50wt% and the concentration of the hexamethylenediamine solution is 50wt%.
In one embodiment, in step (2), the molar ratio of hexamethylenediamine to adipic acid is 1: (1-5) weighing the hexamethylenediamine solution and the adipic acid solution according to the stoichiometric amount.
Preferably, in the step (2), the molar ratio of the hexamethylene diamine to the adipic acid is 1:2 and the adipic acid solution were weighed out.
In one embodiment, in the step (3), the molar ratio of the hexamethylene diamine to the adipic acid (1-5): 1 and the hexamethylenediamine solution and the adipic acid solution are weighed out.
Preferably, in step (3), the molar ratio of hexamethylenediamine to adipic acid is 2:1 and the hexamethylenediamine solution and the adipic acid solution are weighed out.
In the step (2), hexamethylenediamine reacts with adipic acid and other substances or adipic acid is excessive, so that a carboxyl-terminated intermediate can be obtained; in the step (3), the hexamethylenediamine reacts with adipic acid and other substances or the hexamethylenediamine is excessive, so that an amino-terminated intermediate can be obtained. In the traditional preparation process, the hexamethylene diamine solution needs to be slowly dripped into the adipic acid solution, side reactions are more, the dripping speed of the hexamethylene diamine solution and the pH and temperature changes of a reaction system need to be strictly controlled, the requirements on the operation process are strict, and the reaction process is slow. Compared with the traditional preparation process, the preparation method provided by the embodiment of the invention has the advantages that the carboxyl-terminated intermediate and the amino-terminated intermediate are respectively obtained by dropwise adding in sections, and then the two intermediates are reacted, so that the oxidation of diamine can be reduced, few byproducts are generated, and the preparation method is favorable for obtaining high-quality nylon 66 salt.
In one example, in the step (4), the pH of the reaction solution is adjusted with the hexamethylenediamine so that the pH =7.6 to 8.0.
In one embodiment, the specific process of step (5) includes: adding activated carbon into the crude nylon 66 salt solution, filtering to obtain a nylon 66 salt solution, carrying out reduced pressure distillation on the nylon 66 salt solution, and carrying out vacuum drying on the solid obtained after the reduced pressure distillation to obtain a nylon 66 salt solid.
The crude solution of the nylon 66 salt is refined, and is sequentially subjected to adsorption, filtration, reduced pressure distillation and drying processes to obtain dry and pure nylon 66 salt solid, so that high-quality polymerization monomers are provided for synthesizing a nylon 66 polymer through subsequent condensation polymerization of the nylon 66 salt, and the quality of the prepared nylon 66 polymer is ensured.
Specifically, the using amount of the activated carbon is 1-5 wt% of the crude solution of the nylon 66 salt, the temperature of the reduced pressure distillation is 70-100 ℃, the temperature of the vacuum drying is 70-90 ℃, and the drying time is 12-24 hours.
Preferably, the using amount of the activated carbon is 1-2 wt% of the crude solution of the nylon 66 salt, and the temperature of the reduced pressure distillation is 70-80 ℃.
Active carbon is added into the crude solution of the nylon 66 salt, so that the color can be decolored and impurities such as unreacted micromolecules can be removed. The amount of the activated carbon is not strictly required, so long as impurities in the crude nylon 66 salt solution are adsorbed and removed, and on the premise of ensuring the adsorption and removal effects, less activated carbon is used as far as possible, so that on one hand, the amount of the activated carbon can be saved, resources are saved, on the other hand, the less activated carbon is beneficial to subsequent filtering operation, and the efficiency is improved, therefore, the amount of the activated carbon can be set to be 1-2 wt% of the crude nylon 66 salt solution.
It is to be understood that the inert gas is not particularly limited, and may be a common inert gas such as nitrogen, argon, helium, neon, or the like.
The invention also provides a method for preparing nylon 66 from the nylon 66 salt prepared by the preparation method of the nylon 66 salt, which comprises the following steps:
a: dissolving the nylon 66 salt solid in water to prepare a nylon 66 salt solution; putting the nylon 66 salt solution into a reaction kettle, vacuumizing, and introducing N 2 ；
B: opening a stirring device, raising the temperature in the reaction kettle, and carrying out prepolymerization reaction;
c: continuously raising the temperature in the reaction kettle, releasing the pressure in the reaction kettle to normal pressure, and carrying out polycondensation reaction;
d: vacuumizing, and reacting for a certain time to obtain the nylon 66.
In one embodiment, in the step B, the temperature in the reaction kettle is 180-230 ℃, the pressure in the reaction kettle is 1.2-2.0 MPa, and the prepolymerization reaction time is 0.5-5 h.
Preferably, in the step B, the temperature in the reaction kettle is 200-220 ℃, the pressure in the reaction kettle is 1.7-1.8 MPa, and the prepolymerization time is 1-2 h.
In one embodiment, in the step C, the temperature in the reaction kettle is 260-290 ℃, and the time of the polycondensation reaction is 0.5-5 h.
Preferably, in the step C, the temperature in the reaction kettle is 270-280 ℃, and the time of the polycondensation reaction is 1-2 h.
In one embodiment, in the step D, the reaction time after vacuumizing is 0.1-2 h.
Preferably, in the step D, the reaction time after vacuumizing is 0.2 h-0.5 h.
The nylon 66 prepared by the method has less salt impurities and high purity, is more favorable for the polycondensation reaction, ensures the quality of the nylon 66 polymer prepared by the method, and has high relative viscosity and excellent performance of the nylon 66.
Drawings
FIG. 1: infrared spectroscopic analysis of Nylon 66 salt obtained in example 1.
FIG. 2: analysis of the nylon 66 salt TG obtained in example 1.
FIG. 3: DSC analysis of the nylon 66 salt obtained in example 1.
FIG. 4: infrared spectroscopic analysis of Nylon 66 obtained in example 1.
FIG. 5: TG analysis of nylon 66 obtained in example 1.
FIG. 6: DSC analysis of nylon 66 obtained in example 1.
FIG. 7: XRD analysis of nylon 66 obtained in example 1.
Detailed Description
The invention is further described with reference to specific examples. It should be noted that the following examples are only for illustrating the present invention and are not to be construed as limiting the technical solutions described in the present invention, and all the technical solutions and modifications thereof which do not depart from the present invention should be covered within the scope of the claims of the present invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the invention, "a plurality" means at least two, e.g., two, three, etc., unless explicitly specified otherwise. In the description of the present invention, "a plurality" means at least one, e.g., one, two, etc., unless specifically limited otherwise.
The words "preferably," "more preferably," and the like, in the present disclosure mean embodiments of the disclosure that may, in some instances, provide certain benefits. However, other embodiments may be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the invention.
When a range of values is disclosed herein, the range is considered to be continuous and includes both the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. Further, when multiple range-describing features or characteristics are provided, the ranges may be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The following are specific examples, and the raw materials used in the examples are all commercially available products unless otherwise specified.
Example 1
The preparation method of the nylon 66 salt specifically comprises the following steps:
(1) Weighing 219.3 (1.50 mol) of adipic acid, dissolving in water, and preparing into an adipic acid solution with the mass fraction of 50%; weighing 174.3g (1.50 mol) of hexamethylenediamine, and dissolving in water to prepare a hexamethylenediamine solution with the mass fraction of 50%;
(2) Taking 116.2g of hexamethylenediamine solution, dropwise adding the hexamethylenediamine solution into 292.4g of adipic acid solution under the condition of water bath stirring at the temperature of 40 ℃, and introducing inert gas for protection to obtain a carboxyl-terminated intermediate solution;
(3) Taking 146.2g of adipic acid solution, dropwise adding the adipic acid solution into 232.4g of hexamethylenediamine solution under the condition of water bath stirring at the temperature of 30 ℃, and introducing inert gas for protection during the process to obtain an amino-terminated intermediate solution;
(4) Dropwise adding the amido-terminated intermediate solution into the carboxyl-terminated intermediate solution under the stirring condition of 30 ℃, completely reacting to obtain a nylon 66 salt crude solution, controlling the reaction temperature in the process, introducing inert gas for protection, testing the pH value of the solution, and finally adding a trace amount of hexamethylenediamine to adjust the pH = 7.6-8.0;
(5) Adding activated carbon with the mass of 1% relative to the mass of the crude nylon 66 salt solution, decolorizing and adsorbing small molecular impurities, filtering after 2h to obtain a nylon 66 salt solution, carrying out reduced pressure distillation on the nylon 66 salt solution, and drying the solid obtained after the reduced pressure distillation in a vacuum drying oven at 70 ℃ for 12h to obtain a dried nylon 66 salt solid.
The method for preparing nylon 66 from the nylon 66 salt solid comprises the following steps:
a: dissolving the nylon 66 salt solid in water to prepare 80wt% nylon 66 salt solution; putting into a reaction kettle, vacuumizing, checking the air tightness of the reaction kettle, and introducing N 2 Repeating the steps for three times;
b: opening the stirring device, raising the temperature in the reaction kettle to 180 ℃, reacting for 0.5h, and carrying out prepolymerization reaction;
c: continuously raising the temperature in the reaction kettle to 260 ℃, slowly releasing the pressure in the reaction kettle to normal pressure, and carrying out thermal insulation polycondensation for 5 hours at the normal pressure;
d: vacuumizing and reacting for 2h to obtain nylon 66, opening the kettle and discharging.
Example 2
The preparation method of the nylon 66 salt specifically comprises the following steps:
(1) Weighing 219.3 (1.50 mol) of adipic acid, dissolving in water, and preparing into an adipic acid solution with the mass fraction of 40%; weighing 174.3g (1.50 mol) of hexamethylenediamine, and dissolving in water to prepare a hexamethylenediamine solution with the mass fraction of 40%;
(2) Taking 145.25g of hexamethylenediamine solution, dropwise adding the hexamethylenediamine solution into 365.5g of adipic acid solution under the condition of water bath stirring at 50 ℃, and introducing inert gas for protection during the dripping of the hexamethylenediamine solution to obtain a carboxyl-terminated intermediate solution;
(3) 182.75g of adipic acid solution is taken and added dropwise into 290.0g of hexamethylenediamine solution under the condition of stirring in a water bath at the temperature of 35 ℃, and inert gas is introduced for protection in the process to obtain an amino-terminated intermediate solution;
(4) Dropwise adding the amido-terminated intermediate solution into the carboxyl-terminated intermediate solution under the stirring condition of 40 ℃, completely reacting to obtain a nylon 66 salt crude solution, controlling the reaction temperature in the process, introducing inert gas for protection, testing the pH value of the solution, and finally adding a trace amount of hexamethylenediamine to adjust the pH = 7.6-8.0;
(5) Adding activated carbon with the mass of 2% relative to the mass of the crude nylon 66 salt solution, decolorizing and adsorbing small molecular impurities, filtering after 2h to obtain a nylon 66 salt solution, carrying out reduced pressure distillation on the nylon 66 salt solution, and drying the solid obtained after the reduced pressure distillation in a vacuum drying oven at 80 ℃ for 18h to obtain a dried nylon 66 salt solid.
The method for preparing nylon 66 from the nylon 66 salt solid comprises the following steps:
a: dissolving the nylon 66 salt solid in water to prepare 80wt% nylon 66 salt solution; putting into a reaction kettle, vacuumizing, checking the air tightness of the reaction kettle, and introducing N 2 Repeating the steps for three times;
b: opening the stirring device, raising the temperature in the reaction kettle to 200 ℃, reacting for 2 hours, and carrying out prepolymerization reaction;
c: continuously raising the temperature in the reaction kettle to 270 ℃, slowly releasing the pressure in the reaction kettle to normal pressure, and carrying out thermal insulation polycondensation for 2 hours at the normal pressure;
d: vacuumizing and reacting for 0.5h to obtain nylon 66, and opening the kettle to discharge.
Example 3
The preparation method of the nylon 66 salt specifically comprises the following steps:
(1) Weighing 219.3 (1.50 mol) of adipic acid, dissolving in water, and preparing an adipic acid solution with the mass fraction of 60%; weighing 174.3g (1.50 mol) of hexamethylenediamine, and dissolving in water to prepare a hexamethylenediamine solution with the mass fraction of 60%;
(2) 96.83g of hexamethylenediamine solution is taken and added dropwise into 243.67g of adipic acid solution under the condition of water bath stirring at the temperature of 60 ℃, and inert gas is introduced for protection during the process to obtain a carboxyl-terminated intermediate solution;
(3) Taking 121.83g of adipic acid solution, dropwise adding the adipic acid solution into 193.67g of hexamethylenediamine solution under the condition of stirring in a water bath at the temperature of 30 ℃, and introducing inert gas for protection during the process to obtain an amino-terminated intermediate solution;
(4) Dropwise adding the amido-terminated intermediate solution into the carboxyl-terminated intermediate solution under the stirring condition of 60 ℃, completely reacting to obtain a nylon 66 salt crude solution, controlling the reaction temperature in the process, introducing inert gas for protection, testing the pH value of the solution, and finally adding a trace amount of hexamethylenediamine to adjust the pH = 7.6-8.0;
(5) Adding activated carbon with the mass of 3% relative to the mass of the crude nylon 66 salt solution, decolorizing and adsorbing small molecular impurities, filtering after 2h to obtain a nylon 66 salt solution, carrying out reduced pressure distillation on the nylon 66 salt solution, and drying the solid obtained after the reduced pressure distillation in a vacuum drying oven at 90 ℃ for 24h to obtain a dried nylon 66 salt solid.
The method for preparing nylon 66 from the nylon 66 salt solid comprises the following steps:
a: dissolving the nylon 66 salt solid in water to prepare 80wt% nylon 66 salt solution; putting into a reaction kettle, vacuumizing, checking the air tightness of the reaction kettle, and introducing N 2 Repeating the steps for three times;
b: opening the stirring device, raising the temperature in the reaction kettle to 220 ℃, reacting for 2 hours, and carrying out prepolymerization reaction;
c: continuously raising the temperature in the reaction kettle to 290 ℃, slowly releasing the pressure in the reaction kettle to normal pressure, and carrying out heat preservation and polycondensation for 0.5h at the normal pressure;
d: vacuumizing and reacting for 6min to obtain nylon 66, opening the kettle and discharging.
Example 4
The preparation method of the nylon 66 salt specifically comprises the following steps:
(1) Weighing 219.3 (1.50 mol) of adipic acid, dissolving in water, and preparing into an adipic acid solution with the mass fraction of 50%; weighing 174.3g (1.50 mol) of hexamethylenediamine, and dissolving in water to prepare a hexamethylenediamine solution with the mass fraction of 50%;
(2) Taking 116.2g of hexamethylenediamine solution, dropwise adding the hexamethylenediamine solution into 328.95g of adipic acid solution under the condition of water bath stirring at the temperature of 60 ℃, and introducing inert gas for protection to obtain a carboxyl-terminated intermediate solution;
(3) Taking 109.65g of adipic acid solution, dropwise adding the adipic acid solution into 232.4g of hexamethylenediamine solution under the condition of water bath stirring at the temperature of 40 ℃, and introducing inert gas for protection to obtain an amino-terminated intermediate solution;
(4) Dropwise adding the amido-terminated intermediate solution into the carboxyl-terminated intermediate solution under the stirring condition of 40 ℃, completely reacting to obtain a nylon 66 salt crude solution, controlling the reaction temperature in the process, introducing inert gas for protection, testing the pH value of the solution, and finally adding a trace amount of hexamethylenediamine to adjust the pH = 7.6-8.0;
(5) Adding activated carbon with the mass of 5% relative to the mass of the crude nylon 66 salt solution, decolorizing and adsorbing small molecular impurities, filtering after 2h to obtain a nylon 66 salt solution, carrying out reduced pressure distillation on the nylon 66 salt solution, and drying the solid obtained after the reduced pressure distillation in a vacuum drying oven at 70 ℃ for 24h to obtain a dried nylon 66 salt solid.
The method for preparing nylon 66 from the nylon 66 salt solid comprises the following steps:
a: dissolving the nylon 66 salt solid in water to prepare 80wt% nylon 66 salt solution; putting into a reaction kettle, vacuumizing, checking the air tightness of the reaction kettle, and introducing N 2 Repeating the steps for three times;
b: opening the stirring device, raising the temperature in the reaction kettle to 230 ℃, reacting for 5 hours, and carrying out prepolymerization reaction;
c: continuously raising the temperature in the reaction kettle to 280 ℃, slowly releasing the pressure in the reaction kettle to normal pressure, and carrying out polycondensation for 1h under the normal pressure;
d: vacuumizing and reacting for 12min to obtain nylon 66, opening the kettle and discharging.
Example 5
The preparation method of the nylon 66 salt specifically comprises the following steps:
(1) Weighing 219.3 (1.50 mol) of adipic acid, dissolving in water, and preparing into an adipic acid solution with the mass fraction of 50%; weighing 174.3g (1.50 mol) of hexamethylenediamine, and dissolving in water to prepare a hexamethylenediamine solution with the mass fraction of 50%;
(2) Taking 116.2g of hexamethylenediamine solution, dropwise adding the hexamethylenediamine solution into 219.3g of adipic acid solution under the condition of water bath stirring at the temperature of 60 ℃, and introducing inert gas for protection to obtain a carboxyl-terminated intermediate solution;
(3) Adding 219.3g of adipic acid solution dropwise into 232.4g of hexamethylenediamine solution under the condition of water bath stirring at 30 ℃, and introducing inert gas for protection to obtain an amino-terminated intermediate solution;
(4) Dropwise adding the amino-terminated intermediate solution into the carboxyl-terminated intermediate solution under the stirring condition of 40 ℃, completely reacting to obtain a nylon 66 salt crude solution, controlling the reaction temperature in the process, introducing inert gas for protection, testing the pH value of the solution, and finally adding trace hexamethylene diamine to adjust the pH = 7.6-8.0;
(5) Adding activated carbon accounting for 1% of the mass of the crude nylon 66 salt solution, decoloring and adsorbing small molecular impurities, filtering after 2 hours to obtain a nylon 66 salt solution, carrying out reduced pressure distillation on the nylon 66 salt solution, and drying the solid obtained after the reduced pressure distillation in a vacuum drying oven at 70 ℃ for 24 hours to obtain a dried nylon 66 salt solid.
The method for preparing nylon 66 from the nylon 66 salt solid comprises the following steps:
a: dissolving the nylon 66 salt solid in water to prepare 80wt% nylon 66 salt solution; putting into a reaction kettle, vacuumizing, checking the air tightness of the reaction kettle, and introducing N 2 Repeating the steps for three times;
b: opening the stirring device, raising the temperature in the reaction kettle to 210 ℃, reacting for 2 hours, and carrying out prepolymerization reaction;
c: continuously raising the temperature in the reaction kettle to 280 ℃, slowly releasing the pressure in the reaction kettle to normal pressure, and carrying out thermal insulation polycondensation for 2 hours at the normal pressure;
d: vacuumizing and reacting for 10min to obtain nylon 66, opening the kettle and discharging.
Example 6
The preparation method of the nylon 66 salt specifically comprises the following steps:
(1) Weighing 219.3 (1.50 mol) of adipic acid, dissolving in water, and preparing into an adipic acid solution with the mass fraction of 50%; weighing 174.3g (1.50 mol) of hexamethylenediamine, and dissolving in water to prepare a hexamethylenediamine solution with the mass fraction of 50%;
(2) Taking 116.2g of hexamethylenediamine solution, dropwise adding the hexamethylenediamine solution into 365.5g of adipic acid solution under the condition of stirring in a water bath at 60 ℃, and introducing inert gas for protection to obtain a carboxyl-terminated intermediate solution;
(3) Dripping 73.1 adipic acid solution into 232.4g of hexamethylenediamine solution under the condition of water bath stirring at the temperature of 30 ℃, and introducing inert gas for protection to obtain an amino-terminated intermediate solution;
(4) Dropwise adding the amido-terminated intermediate solution into the carboxyl-terminated intermediate solution under the stirring condition of 40 ℃, completely reacting to obtain a nylon 66 salt crude solution, controlling the reaction temperature in the process, introducing inert gas for protection, testing the pH value of the solution, and finally adding a trace amount of hexamethylenediamine to adjust the pH = 7.6-8.0;
(5) Adding activated carbon accounting for 1% of the mass of the crude nylon 66 salt solution, decoloring and adsorbing small molecular impurities, filtering after 2 hours to obtain a nylon 66 salt solution, carrying out reduced pressure distillation on the nylon 66 salt solution, and drying the solid obtained after the reduced pressure distillation in a vacuum drying oven at 70 ℃ for 24 hours to obtain a dried nylon 66 salt solid.
The method for preparing nylon 66 from the nylon 66 salt solid comprises the following steps:
a: dissolving the nylon 66 salt solid in water to prepare 80wt% nylon 66 salt solution; putting into a reaction kettle, vacuumizing, checking the air tightness of the reaction kettle, and introducing N 2 Repeating the steps for three times;
b: opening the stirring device, raising the temperature in the reaction kettle to 210 ℃, reacting for 2 hours, and carrying out prepolymerization reaction;
c: continuously raising the temperature in the reaction kettle to 280 ℃, slowly releasing the pressure in the reaction kettle to normal pressure, and carrying out polycondensation for 1h under the normal pressure;
d: vacuumizing and reacting for 10min to obtain nylon 66, opening the kettle and discharging.
Example 7
The preparation method of the nylon 66 salt specifically comprises the following steps:
(1) Weighing 219.3 (1.50 mol) of adipic acid, dissolving in water, and preparing into an adipic acid solution with the mass fraction of 50%; weighing 174.3g (1.50 mol) of hexamethylenediamine, and dissolving in water to prepare a hexamethylenediamine solution with the mass fraction of 50%;
(2) 58.1g of hexamethylenediamine solution is taken and added dropwise into 292.4g of adipic acid solution under the condition of water bath stirring at the temperature of 60 ℃, and inert gas is introduced for protection during the process to obtain a carboxyl-terminated intermediate solution;
(3) Taking 146.2g of adipic acid solution, dropwise adding the adipic acid solution into 290.5g of hexamethylenediamine solution under the condition of water bath stirring at the temperature of 30 ℃, and introducing inert gas for protection to obtain an amino-terminated intermediate solution;
(4) Dropwise adding the amino-terminated intermediate solution into the carboxyl-terminated intermediate solution under the stirring condition of 40 ℃, completely reacting to obtain a nylon 66 salt crude solution, controlling the reaction temperature in the process, introducing inert gas for protection, testing the pH value of the solution, and finally adding trace hexamethylene diamine to adjust the pH = 7.6-8.0;
(5) Adding activated carbon accounting for 1% of the mass of the crude nylon 66 salt solution, decoloring and adsorbing small molecular impurities, filtering after 2 hours to obtain a nylon 66 salt solution, carrying out reduced pressure distillation on the nylon 66 salt solution, and drying the solid obtained after the reduced pressure distillation in a vacuum drying oven at 70 ℃ for 24 hours to obtain a dried nylon 66 salt solid.
The method for preparing nylon 66 from the nylon 66 salt solid comprises the following steps:
a: dissolving the nylon 66 salt solid in water to prepare 80wt% nylon 66 salt solution; putting into a reaction kettle, vacuumizing and checking the reactionThe air tightness of the kettle is sealed by introducing N 2 Repeating the steps for three times;
b: opening the stirring device, raising the temperature in the reaction kettle to 210 ℃, reacting for 2 hours, and carrying out prepolymerization reaction;
c: continuously raising the temperature in the reaction kettle to 280 ℃, simultaneously slowly releasing the pressure in the reaction kettle to normal pressure, and carrying out heat preservation and polycondensation for 1 hour at the normal pressure;
d: vacuumizing and reacting for 10min to obtain nylon 66, opening the kettle and discharging.
Example 8
The preparation method of the nylon 66 salt specifically comprises the following steps:
(1) Weighing 219.3 (1.50 mol) of adipic acid, dissolving in water, and preparing into an adipic acid solution with the mass fraction of 50%; weighing 174.3g (1.50 mol) of hexamethylenediamine, and dissolving in water to prepare a hexamethylenediamine solution with the mass fraction of 50%;
(2) 58.1g of hexamethylenediamine solution is taken and added dropwise into 219.3g of adipic acid solution under the condition of water bath stirring at 60 ℃, and inert gas is introduced for protection during the process to obtain a carboxyl-terminated intermediate solution;
(3) 219.3g of adipic acid solution is taken and added dropwise into 290.5g of hexamethylenediamine solution under the condition of stirring in a water bath at the temperature of 30 ℃, and inert gas is introduced for protection in the process to obtain an amino-terminated intermediate solution;
(4) Dropwise adding the amino-terminated intermediate solution into the carboxyl-terminated intermediate solution under the stirring condition of 40 ℃, completely reacting to obtain a nylon 66 salt crude solution, controlling the reaction temperature in the process, introducing inert gas for protection, testing the pH value of the solution, and finally adding trace hexamethylene diamine to adjust the pH = 7.6-8.0;
(5) Adding activated carbon accounting for 1% of the mass of the crude nylon 66 salt solution, decoloring and adsorbing small molecular impurities, filtering after 2 hours to obtain a nylon 66 salt solution, carrying out reduced pressure distillation on the nylon 66 salt solution, and drying the solid obtained after the reduced pressure distillation in a vacuum drying oven at 70 ℃ for 24 hours to obtain a dried nylon 66 salt solid.
The method for preparing nylon 66 from the nylon 66 salt solid comprises the following steps:
a: dissolving nylon 66 salt solid in water to prepareObtaining 80wt% nylon 66 salt solution; putting into a reaction kettle, vacuumizing, checking the air tightness of the reaction kettle, and introducing N 2 Repeating the steps for three times;
b: opening the stirring device, raising the temperature in the reaction kettle to 210 ℃, reacting for 2 hours, and carrying out prepolymerization reaction;
c: continuously raising the temperature in the reaction kettle to 280 ℃, slowly releasing the pressure in the reaction kettle to normal pressure, and carrying out polycondensation for 1h under the normal pressure;
d: vacuumizing and reacting for 10min to obtain nylon 66, opening the kettle and discharging.
Comparative example 1
The preparation method of the nylon 66 salt specifically comprises the following steps:
(1) Weighing 219.3 (1.50 mol) of adipic acid, dissolving in water, and preparing into an adipic acid solution with the mass fraction of 50%; weighing 174.3g (1.50 mol) of hexamethylenediamine, and dissolving in water to prepare a hexamethylenediamine solution with the mass fraction of 50%;
(2) Heating an adipic acid solution to 40 ℃, stirring at a constant speed, keeping nitrogen purging, slowly dropwise adding a hexamethylenediamine solution, keeping the temperature of the system at 40-45 ℃, monitoring the pH and temperature change of the reaction system by using a precise acidometer and a thermometer in the adding process, stopping dropwise adding the hexamethylenediamine solution before testing the pH each time, testing the pH value after the system is stable, continuously dropwise adding the hexamethylenediamine solution, and repeating the steps until the pH = 7.8-8, which is the reaction end point, so as to obtain a crude nylon 66 salt solution;
(3) Adding activated carbon with the mass of 1% relative to the mass of the crude nylon 66 salt solution, decoloring and adsorbing small molecular impurities, and filtering after 2 hours to obtain a nylon 66 salt solution;
(4) Distilling the solution of the nylon 66 salt under reduced pressure, and drying the solid after the reduced pressure distillation in a vacuum drying oven at 70 ℃ for 24 hours to obtain the dried solid of the nylon 66 salt.
The method for preparing nylon 66 from the nylon 66 salt solid comprises the following steps:
a: dissolving the nylon 66 salt solid in water to prepare 80wt% nylon 66 salt solution; putting into a reaction kettle, vacuumizing, checking the air tightness of the reaction kettle, and introducing N 2 Repeating the steps for three times;
b: opening the stirring device, raising the temperature in the reaction kettle to 210 ℃, reacting for 2 hours, and carrying out prepolymerization reaction;
c: continuously raising the temperature in the reaction kettle to 280 ℃, slowly releasing the pressure in the reaction kettle to normal pressure, and carrying out polycondensation for 1h under the normal pressure;
d: vacuumizing and reacting for 10min to obtain nylon 66, opening the kettle and discharging.
Comparative example 2
The preparation method of the nylon 66 salt specifically comprises the following steps:
(1) Weighing 219.3 (1.50 mol) of adipic acid, dissolving in water, and preparing into an adipic acid solution with the mass fraction of 50%; weighing 174.3g (1.50 mol) of hexamethylenediamine, and dissolving in water to prepare a hexamethylenediamine solution with the mass fraction of 50%;
(2) Heating an adipic acid solution to 50 ℃, stirring at a constant speed, keeping nitrogen purging, slowly dropwise adding a hexamethylenediamine solution, keeping the temperature of the system at 50-55 ℃, monitoring the pH and temperature change of the reaction system by using a precise acidometer and a thermometer in the adding process, stopping dropwise adding the hexamethylenediamine solution before testing the pH each time, testing the pH value after the system is stable, continuously dropwise adding the hexamethylenediamine solution, and repeating the steps until the pH = 7.8-8, which is the reaction end point, so as to obtain a crude nylon 66 salt solution;
(3) Adding activated carbon with the mass of 1% relative to the mass of the crude nylon 66 salt solution, decoloring and adsorbing small molecular impurities, and filtering after 2 hours to obtain a nylon 66 salt solution;
(4) Distilling the nylon 66 salt solution under reduced pressure, and drying the solid after the reduced pressure distillation in a vacuum drying oven at 70 ℃ for 24h to obtain dry nylon 66 salt solid.
The method for preparing nylon 66 from the nylon 66 salt solid comprises the following steps:
a: dissolving the nylon 66 salt solid in water to prepare 80wt% nylon 66 salt solution; putting into a reaction kettle, vacuumizing, checking the air tightness of the reaction kettle, and introducing N 2 Repeating the steps for three times;
b: opening the stirring device, raising the temperature in the reaction kettle to 210 ℃, reacting for 2 hours, and carrying out prepolymerization reaction;
c: continuously raising the temperature in the reaction kettle to 280 ℃, slowly releasing the pressure in the reaction kettle to normal pressure, and carrying out polycondensation for 1h under the normal pressure;
d: vacuumizing and reacting for 10min to obtain nylon 66, opening the kettle and discharging.
Test examples
The nylon 66 salt and the nylon 66 prepared in the examples 1 to 8 and the comparative examples 1 to 2 were subjected to performance index tests, specifically including the pH value, the total volatile alkali content, the pseudo nitric acid content, the UV index and the relative viscosity of the nylon 66. The specific test method is as follows:
1. determination of the pH of Nylon 66 salt
A10 g nylon 66 salt sample is taken to prepare a nylon 66 salt aqueous solution with the mass fraction of 10%, and the pH value of the nylon 66 salt is tested at 25 ℃ according to a test method specified in the standard GB/T9724-2007.
2. Determination of total volatile alkali content in nylon 66 salt
The total volatile alkali content, expressed in mL, is expressed in mL of the standard solution of sulfuric acid consumed by 100g of nylon 66 salt, measured according to the test method specified in standard SH/T1498.3-1997.
3. Determination of content of pseudo nitric acid in nylon 66 salt
The content of pseudonitric acid in the nylon 66 salt, in mg/kg, calculated as nitric acid, was determined according to the test method specified in standard SH/T1498.4-1997.
4. And detecting the UV index of the nylon 66 salt.
Measured according to the test method specified in the standard SH/T1498.7-1997, the UV index is the absorbance A at a wavelength of 279nm at a concentration of 0.1% (m/V) in the solution of nylon 66 salt and a cell thickness of 1cm, the UV index = A × 10 -3 。
5. Relative viscosity measurement of Nylon 66
The determination is carried out according to the test method specified in the standard GB/T12006.1-2009
TABLE 1 measurement results of performance indexes of nylon 66 salt and nylon 66 of examples and comparative examples
As can be seen from Table 1, the performance index data in comparative examples 1-8 and comparative examples 1-2 show that the total volatile alkali content, the pseudo nitric acid content and the UV index of the nylon 66 salt in examples 1-8 are obviously lower than those in comparative examples 1-2, which indicates that the nylon 66 salt prepared by the method of the present application has less impurities and high purity. The relative viscosity of the nylon 66 prepared in the embodiments 1-8 of the invention is obviously higher than that of the comparative examples 1-2, and the performance is excellent.
The IR spectrum of the nylon 66 salt prepared in example 1 is shown in FIG. 1 at wave number of 2500-3200 cm -1 Having a broad and strong absorption band of-NH 3 + The stretching vibration of (2); 2930cm -1 Stretching vibration with absorption peak of-CH-; 2864cm -1 Stretching vibration with absorption peak of-CH-; 2210cm -1 The nearby absorption peak is-NH 3 + Frequency doubling and frequency combination; 1645cm -1 Has an absorption peak of-NH 3 + Bending vibration of (2); 1518cm -1 The nearby absorption peak is-COO - The stretching vibration of (2). 1385cm -1 Is of the formula-NH 3 +- COO-characteristic absorption peak, which proves that adipic acid reacts with hexamethylene diamine to generate nylon 66 salt.
The thermogravimetric analysis (TG) of the nylon 66 salt prepared in example 1 is shown in fig. 2, from which it can be seen that the maximum decomposition rate temperature of the nylon 66 salt is 219 ℃.
The differential scanning calorimetry (DSC curve) of the nylon 66 salt prepared in example 1 is shown in FIG. 3, in which an endothermic peak at 203 ℃ appears in a temperature rise curve corresponding to the melting point of the nylon 66 salt, and an exothermic peak at 218 ℃ appears in a temperature drop curve corresponding to the crystallization temperature of a mixture of the nylon 66 salt and a prepolymer (a product of a prepolymerization reaction of the nylon 66 salt).
The IR spectrum of nylon 66 prepared in example 1 is shown in FIG. 4, comparing the IR spectra of nylon 66 salt and nylon 66, the disappearance of the absorption peak of ammonium salt with the characteristic peak of amide group band (3299 cm) -1 ) The occurrence of the reaction proves that the nylon 66 salt has a condensation polymerization reaction to generate amido bond, and the product is obtainedNylon 66.
The TG profile of the nylon 66 prepared in example 1 is shown in fig. 5, from which it can be seen that the maximum decomposition rate of the nylon 66 is at 434 ℃.
The DSC curve of nylon 66 prepared in example 1 is shown in fig. 6, and only one endothermic peak (exothermic peak) appears in both the temperature-increasing curve and the temperature-decreasing curve, and it was found that nylon 66 had a melting point of 263 ℃ and a crystallization temperature of 228 ℃ by analysis.
The X-ray diffraction (XRD) of the nylon 66 prepared in example 1 is shown in fig. 7, which has two distinct diffraction peaks with small intensity difference, and conforms to the XRD pattern characteristics of the nylon 66.
Both the nylon 66 salt and the nylon 66 prepared in examples 2-8 achieved substantially the same technical results as example 1.
In conclusion, the method for preparing the nylon 66 salt has mild reaction conditions and is easy to operate. The UV index value of nylon 66 salt prepared by the invention is far less than that of industrial standard superior product, namely 0.1 multiplied by 10 -3 And the requirement of the content of the pseudo nitric acid of 25mg/kg is favorable for preparing the nylon 66 polymer by a subsequent polymerization process.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents or improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A preparation method of nylon 66 salt is characterized by comprising the following steps: the method comprises the following steps:
(1) Dissolving adipic acid in water to prepare an adipic acid solution; dissolving hexamethylene diamine in water to prepare a hexamethylene diamine solution;
(2) Dropwise adding a certain amount of the hexamethylenediamine solution into a certain amount of the adipic acid solution under the protection of inert gas and the water bath stirring condition of 40-60 ℃ to obtain a carboxyl-terminated intermediate solution;
(3) Dropwise adding a certain amount of the adipic acid solution into a certain amount of the hexamethylenediamine solution under the protection of inert gas and the stirring condition of a water bath at 30-40 ℃ to obtain an amino-terminated intermediate solution;
(4) Dropwise adding the amino-terminated intermediate solution into the carboxyl-terminated intermediate solution under the stirring condition of 30-60 ℃ under the protection of inert gas, and completely reacting to obtain a nylon 66 salt crude solution;
(5) And refining the crude solution of the nylon 66 salt to obtain a nylon 66 salt solid.
2. The method of claim 1, wherein the nylon 66 salt is prepared by: in the step (1), the concentration of the adipic acid solution is 40-60 wt%, and the concentration of the hexamethylenediamine solution is 40-60 wt%.
3. The method of claim 2 for preparing a nylon 66 salt, wherein: in the step (1), the concentration of the adipic acid solution is 50wt%, and the concentration of the hexamethylenediamine solution is 50wt%.
4. The method of claim 1, wherein the nylon 66 salt is prepared by: in the step (2), the molar ratio of hexamethylene diamine to adipic acid is 1: (1-5) weighing the hexamethylenediamine solution and the adipic acid solution according to the stoichiometric amount; and/or
In the step (3), the molar ratio of hexamethylene diamine to adipic acid (1-5): 1 and the hexamethylenediamine solution and the adipic acid solution are weighed out.
5. The method of claim 1 for preparing a nylon 66 salt, wherein: in the step (4), the reaction solution is adjusted to have a pH =7.6 to 8.0 with the hexamethylenediamine.
6. The method of claim 1 for preparing a nylon 66 salt, wherein: the specific process of the step (5) comprises the following steps: adding activated carbon into the crude nylon 66 salt solution, filtering to obtain a nylon 66 salt solution, carrying out reduced pressure distillation on the nylon 66 salt solution, and carrying out vacuum drying on the solid obtained after the reduced pressure distillation to obtain a nylon 66 salt solid.
7. The method of claim 6 for preparing nylon 66 salt, wherein: the dosage of the active carbon is 1-5 wt% of the crude solution of the nylon 66 salt, the temperature of the reduced pressure distillation is 70-100 ℃, the temperature of the vacuum drying is 70-90 ℃, and the drying time is 12-24 h.
8. The method of claim 7, wherein the nylon 66 salt is prepared by: the dosage of the active carbon is 1-2 wt% of the crude solution of the nylon 66 salt, and the temperature of the reduced pressure distillation is 70-80 ℃.
9. A method for preparing nylon 66 from a nylon 66 salt prepared by the method for preparing a nylon 66 salt according to any one of claims 1 to 8, characterized in that: the method comprises the following steps:
a: dissolving the nylon 66 salt solid in water to prepare a nylon 66 salt solution; putting the nylon 66 salt solution into a reaction kettle, vacuumizing, and introducing N 2 ；
B: opening a stirring device, raising the temperature in the reaction kettle, and carrying out prepolymerization reaction;
c: continuously raising the temperature in the reaction kettle, releasing the pressure in the reaction kettle to normal pressure, and carrying out polycondensation reaction;
d: vacuumizing, and reacting for a certain time to obtain the nylon 66.
10. The process for preparing nylon 66 of claim 9 wherein: in the step B, the temperature in the reaction kettle is 180-230 ℃, the pressure in the reaction kettle is 1.2-2.0 MPa, and the prepolymerization time is 0.5-5 h; and/or
In the step C, the temperature in the reaction kettle is 260-290 ℃, and the time of the polycondensation reaction is 0.5-5 h; and/or
In the step D, the reaction time after vacuumizing is 0.1-2 h.
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