阅读说明：本技术 一种尼龙盐的合成方法 (Synthetic method of nylon salt ) 是由 程瑾 曹长海 李澜鹏 王宜迪 李秀峥 张利建 彭绍忠 于 2019-10-31 设计创作，主要内容包括：本发明涉及一种尼龙盐的合成方法,先制得二元酸溶液和二元胺溶液,将二元胺溶液流加至二元酸溶液中,当加入量达到二元胺溶液总量90%～95%时,按照一定速度排出反应液至pH监测室,同时以相同流速加入水,开启搅拌并检测pH,当pH为7.0～7.4时,停止流加,反应体系经过滤、干燥得尼龙盐。本发明通过有效检测控制反应终点pH,降低了产品中游离酸和游离胺含量,可以制得高品质尼龙盐。(The invention relates to a synthesis method of nylon salt, which comprises the steps of firstly preparing a dibasic acid solution and a diamine solution, adding the diamine solution into the dibasic acid solution in a flowing manner, discharging a reaction solution into a pH monitoring chamber at a certain speed when the adding amount reaches 90-95% of the total amount of the diamine solution, simultaneously adding water at the same flow rate, starting stirring and detecting the pH, stopping adding in the flowing manner when the pH is 7.0-7.4, and filtering and drying a reaction system to obtain the nylon salt. The invention effectively detects and controls the pH value of the reaction end point, reduces the content of free acid and free amine in the product and can prepare high-quality nylon salt.)

1. A synthetic method of nylon salt is characterized by comprising the following steps: dissolving a binary acid in an organic solvent to prepare a binary acid solution; dissolving diamine in the same organic solvent to prepare a diamine solution; adding a diamine solution into the diamine solution in a flowing manner, discharging the reaction solution to a pH monitoring chamber at a speed of one thousandth/min to one millionth/min of the total volume of the reaction solution when the addition amount reaches 90-95% of the total amount of the diamine solution, adding water at the same flow rate, starting stirring and detecting the pH, stopping the adding in the flowing manner when the pH is 7.0-7.4, and preserving the heat for 30-60 min; the reaction system is filtered and dried to obtain the nylon salt.

2. The method of claim 1, wherein: the dibasic acid is at least one of linear chain dibasic acid and aromatic dibasic acid of which the carboxyl is at two ends of a carbon chain, and the linear chain dibasic acid is C4-C18 dibasic acid.

3. The method of claim 2, wherein: the straight-chain dibasic acid is at least one of succinic acid, adipic acid, azelaic acid, sebacic acid and dodecanedioic acid; the aromatic dibasic acid is at least one of terephthalic acid and phthalic acid.

4. The method of claim 1, wherein: the organic solvent is ethanol, and the volume content of water in the ethanol is 2-20%, preferably 5-10%.

5. The method of claim 1, 2, 3 or 4, wherein: mixing dibasic acid and an organic solvent, and heating until the dibasic acid is dissolved, wherein the heating temperature is 50-75 ℃, and preferably 60-70 ℃.

6. The method of claim 1, 2, 3 or 4, wherein: the mass ratio of the dibasic acid to the organic solvent is 1: 1-1: 10, preferably 1: 5-1: 10.

7. The method of claim 1, wherein: the diamine is at least one of linear diamine and aromatic diamine with amino groups at two ends of a carbon chain, and preferably at least one of aliphatic diamine of C4-C18.

8. The method of claim 7, wherein: the diamine is at least one of butanediamine, hexanediamine, heptanediamine, octanediamine, nonanediamine and decanediamine; the aromatic diamine is at least one of p-phenylenediamine and o-phenylenediamine.

9. The method of claim 1, wherein: in the diamine solution, the mass ratio of the diamine to the organic solvent is 1: 0.5-1: 5, preferably 1: 1-1: 2.

10. The method of claim 1, wherein: diamine and diacid are prepared according to the theoretical molar ratio of 1: 1.

11. The method of claim 1, wherein: the flow-adding speed of the diamine solution is one-thirtieth/min to one-two hundredth/min of the volume of the diamine solution.

12. The method of claim 1, wherein: the pH monitoring chamber is a container with a stirring and pH detection system, and the reaction solution and water are simultaneously fed into the pool for pH detection.

13. The method of claim 1, wherein: the filtration adopts suction filtration, and the pressure is-0.1 MPa-0 MPa; the obtained nylon salt is dried at the temperature of 55-120 ℃ to constant weight.

Technical Field

The invention belongs to the field of synthesis of nylon salt, and particularly relates to a synthesis method of nylon salt.

Background

The nylon salt is formed by reacting dibasic acid with diamine, and various nylon salt products can be prepared by utilizing different dibasic acids and different diamines. The nylon salt is a prerequisite for synthesizing nylon, so that the quality of the nylon salt product has great influence on the quality of a nylon polymerization product, and the nylon salt which contains less impurities, has high yield and high quality becomes a key link in nylon production.

In the prior art, the synthesis of nylon salt usually adopts a solvent method, i.e. acid and amine are respectively dissolved in a solvent, then are mixed together for neutralization reaction, the reaction end point is judged according to the pH value, and then the nylon salt is obtained by separation, purification and drying. When water is used as a solvent, impurities and nylon salt in a system can not be effectively separated in the purification process, so that the impurities of the nylon salt are high, and the yield is low. When an organic solvent is used as a reaction solvent, the end point of the neutralization reaction cannot be effectively controlled in an organic system due to the limitation of the existing pH measuring equipment, so that the content of free acid and free amine of the nylon salt is increased.

CN101456804A discloses a preparation method of semi-aromatic nylon salt, which comprises the steps of carrying out neutralization reaction on aromatic dibasic acid and aliphatic diamine in an organic solvent, carrying out centrifugal separation, and washing the obtained precipitate to obtain the semi-aromatic nylon salt. The selected organic solvent is N-methyl pyrrolidone or dimethylformamide, can dissolve aromatic dibasic acid and aliphatic diamine but can not dissolve semi-aromatic nylon salt, and can easily separate and purify the generated nylon salt.

CN105777553A discloses a preparation method of nylon salt, which comprises the following steps: 1) providing a saturated nylon salt solution; 2) adding diamine and diacid into the solution obtained in the step 1), and then separating out nylon salt solid from the solution; 3) and (3) carrying out solid-liquid separation on the product obtained in the step 2) to obtain the nylon salt solid. The method can be used for reaction at room temperature, and by-product impurities possibly generated in the high-temperature reaction can be reduced due to the fact that high-temperature heating is avoided, so that the nylon yellowing phenomenon of the nylon salt in the subsequent polymerization process can be reduced. However, impurities generated under non-high temperature conditions are not effectively removed.

The preparation process mainly adopts dibasic acid and diamine substrate with higher purity. In addition, the reaction end point is difficult to control, so that the product contains free acid and free amine, and the quality of the nylon salt is poor, and the nylon salt cannot be applied to and polymerized to prepare nylon products.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a synthesis method of a nylon salt. The invention effectively detects and controls the pH value of the reaction end point, reduces the content of free acid and free amine in the product and can prepare high-quality nylon salt.

The synthesis method of the nylon salt provided by the invention comprises the following steps: dissolving a binary acid in an organic solvent to prepare a binary acid solution; dissolving diamine in the same organic solvent to prepare a diamine solution; adding a diamine solution into the diamine solution in a flowing manner, discharging the reaction solution to a pH monitoring chamber at a speed of one thousandth/min to one millionth/min of the total volume of the reaction solution when the flow rate reaches 90-95% of the total amount of the diamine solution, adding water into the pH monitoring chamber at the same flow rate, starting stirring and detecting the pH, stopping adding in the flowing manner when the pH is 7.0-7.4, and keeping the temperature for 30-60 min; the reaction system is filtered and dried to obtain the nylon salt.

In the invention, the dibasic acid is at least one of linear chain dibasic acid, aromatic dibasic acid and the like of which the carboxyl is at two ends of a carbon chain, the linear chain dibasic acid is C4-C18 dibasic acid, and specifically can be at least one of succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid and the like; the aromatic dibasic acid is at least one of terephthalic acid, phthalic acid and the like.

In the invention, the organic solvent is ethanol, and the volume content of water in the ethanol is 2-20%, preferably 5-10%.

In the invention, the dibasic acid and the organic solvent are mixed and heated until the dibasic acid is dissolved, wherein the heating temperature is 50-75 ℃, and preferably 60-70 ℃. The mass ratio of the dibasic acid to the organic solvent is 1: 1-1: 10, preferably 1: 5-1: 10.

In the present invention, the diamine is at least one of a linear diamine having an amino group at both ends of a carbon chain, an aromatic diamine, and the like, and may be at least one of a C4-C18 aliphatic diamine, specifically at least one of butanediamine, hexanediamine, heptanediamine, octanediamine, nonanediamine, decanediamine, and the like; the aromatic diamine is at least one of p-phenylenediamine, o-phenylenediamine and the like.

In the invention, in the diamine solution, the mass ratio of the diamine to the organic solvent is 1: 0.5-1: 5, preferably 1: 1-1: 2.

In the invention, diamine and diacid are prepared according to the theoretical molar ratio of 1: 1.

In the invention, the flow-adding speed of the diamine solution is one-thirtieth/min to one-twenty-one percent/min of the volume of the diamine solution.

In the invention, the pH monitoring chamber is a container with a stirring and pH detection system, and the reaction solution and water can be simultaneously fed into the pool for pH detection.

In the invention, the filtration adopts suction filtration, and the pressure is-0.1 MPa-0 MPa. Drying the obtained nylon salt at 55-120 ℃ to constant weight to obtain the dry nylon salt.

The invention effectively detects and controls the pH value of the reaction end point, reduces the content of free acid and free amine in the nylon salt and has high product yield. The yield can be improved and water-soluble impurities can be further removed by taking the hydrous ethanol as a solvent, so that the high-quality nylon salt can be prepared.

Detailed Description

The method and effect of preparing nylon salt according to the present invention are further illustrated by the following examples. The embodiments are implemented on the premise of the technical scheme of the invention, and detailed implementation modes and specific operation processes are given, but the protection scope of the invention is not limited by the following embodiments.

The experimental procedures in the following examples are, unless otherwise specified, conventional in the art. The experimental materials used in the following examples were purchased from a conventional biochemical reagent store unless otherwise specified.

The nylon salt yield = nylon salt mass/(dibasic acid mass + diamine mass) × 100%. The detection of free acids and free amines in nylon salts is described in synthetic fibers, 1980, (4): 27-29.

Example 1

Weighing 500g of dodecanedioic acid, adding into 3000g of 95% ethanol solution, stirring at 300rpm, heating to 60 ℃, and dissolving the dodecanedioic acid completely to obtain dodecanedioic acid ethanol solution;

weighing 252.6g of 1, 6-hexamethylenediamine, and dissolving in 252.6g of 95% ethanol to obtain 1, 6-hexamethylenediamine ethanol solution;

adding the 1, 6-hexamethylene diamine ethanol solution into the dodecadioic acid ethanol solution at the flow velocity of V₂/30mL/min（V₂Volume of 1, 6-hexamethylenediamine ethanol solution), and after 90% volume of 1, 6-hexamethylenediamine ethanol solution is added, the flow rate is controlled to be V₁10000 mL/min to a pH monitoring chamber (V)₁The total volume of the reaction solution), water is added into a pH monitoring chamber at the same flow rate, stirring is started, the pH is detected, when the pH of the reaction system is =7.0, the flow addition is stopped, and the temperature is kept for 30 min. Filtering under-0.1 MPa, and drying at 55 ℃ to constant weight to obtain the dry nylon salt. The yield of the nylon salt is 95.2 percent, the content of free acid is 0.12 percent, and the content of free amine is 0.10 percent.

Example 2

Weighing 500g of dodecanedioic acid, adding into 3000g of 90% ethanol solution, stirring at 200rpm, heating to 70 ℃, and dissolving the dodecanedioic acid completely to obtain dodecanedioic acid ethanol solution;

weighing 252.6g of 1, 6-hexamethylenediamine, and dissolving in 252.6g of 90% ethanol to obtain 1, 6-hexamethylenediamine ethanol solution;

adding the ethanol solution of 1, 6-hexamethylene diamine into the ethanol solution of dodecanedioic acidIn the medium, the flow rate is V₂/100 mL/min（V₂Volume of 1, 6-hexamethylenediamine ethanol solution), and after adding 95% volume of 1, 6-hexamethylenediamine ethanol solution, controlling the flow rate to be V₁10000 mL/min to a pH monitoring chamber (V)₁The total volume of the reaction solution), water is added into a pH monitoring chamber at the same flow rate, stirring is started, the pH is detected, when the pH of the reaction system is =7.2, the flow addition is stopped, and the temperature is kept for 30 min. Filtering under-0.1 MPa, and drying at 55 ℃ to constant weight to obtain the dry nylon salt. The yield of the nylon salt is 94.5%, the content of free acid is 0.09%, and the content of free amine is 0.11%.

Example 3

Weighing 500g of dodecanedioic acid, adding into 3000g of 95% ethanol solution, stirring at 500rpm, heating to 65 ℃, and dissolving the dodecanedioic acid completely to obtain dodecanedioic acid ethanol solution;

weighing 252.6g of 1, 6-hexamethylenediamine, and dissolving in 252.6g of 95% ethanol to obtain 1, 6-hexamethylenediamine ethanol solution;

adding the 1, 6-hexamethylene diamine ethanol solution into the dodecadioic acid ethanol solution at the flow velocity of V₂/60 mL/min（V₂Volume of 1, 6-hexamethylenediamine ethanol solution), and after 90% volume of 1, 6-hexamethylenediamine ethanol solution is added, the flow rate is controlled to be V₁The reaction solution was discharged to a pH monitoring chamber (V) at 100000 mL/min₁The total volume of the reaction solution), water is added into a pH monitoring chamber at the same flow rate, stirring is started, the pH is detected, when the pH of the reaction system is =7.4, the flow addition is stopped, and the temperature is kept for 30 min. Filtering under-0.1 MPa, and drying at 55 ℃ to constant weight to obtain the dry nylon salt. The yield of the nylon salt is 96.3 percent, the content of free acid is 0.08 percent, and the content of free amine is 0.15 percent.

Example 4

The difference from example 1 is that: succinic acid is used to replace dodecanedioic acid. The yield of the nylon salt is 96.1 percent, the content of free acid is 0.08 percent, and the content of free amine is 0.07 percent.

Example 5

The difference from example 1 is that: sebacic acid was used instead of dodecanedioic acid. The yield of the nylon salt is 95.8 percent, the content of free acid is 0.10 percent, and the content of free amine is 0.09 percent.

Example 6

The difference from example 1 is that: terephthalic acid was used instead of dodecanedioic acid. The yield of the nylon salt is 95.5 percent, the content of free acid is 0.11 percent, and the content of free amine is 0.09 percent.

Example 7

The difference from example 1 is that: decamethylene diamine was used instead of 1, 6-hexamethylene diamine. The yield of the nylon salt is 94.5 percent, the content of free acid is 0.13 percent, and the content of free amine is 0.12 percent.

Example 8

The difference from example 1 is that: 80% ethanol solution was used instead of 95% ethanol solution. The yield of the nylon salt is 92.1 percent, the content of free acid is 0.07 percent, and the content of free amine is 0.06 percent.

Example 9

The difference from example 1 is that: when the reaction system pH =7.4, the feed was stopped. The yield of the nylon salt is 95.4 percent, the content of free acid is 0.05 percent, and the content of free amine is 0.15 percent.

Comparative example 1

The difference from example 1 is that: the end point of the reaction is determined by directly detecting the pH in a conventional manner. The yield of the nylon salt is 93.5 percent, the content of free acid is 0.35 percent, and the content of free amine is 0.43 percent.

Comparative example 2

The difference from example 1 is that: absolute ethyl alcohol is adopted. The yield of nylon salt is 93.8%, the content of free acid is 0.32%, and the content of free amine is 0.39%.