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CN-122010740-A - Preparation method of bio-based nylon 4T salt

CN122010740ACN 122010740 ACN122010740 ACN 122010740ACN-122010740-A

Abstract

The application provides a preparation method of bio-based nylon 4T salt, and relates to the technical field of nylon synthesis. The preparation method comprises the steps of mixing 1, 4-butanediamine with an aqueous solution containing alcohol to form a reaction base solution, then adding terephthalic acid in batches to perform neutralization reaction to generate a soluble nylon 4T salt intermediate product, adding a precipitator to perform alcohol precipitation to crystallize and separate out the product, and performing solid-liquid separation and washing to obtain the nylon 4T salt. The preparation method effectively avoids caking phenomenon caused by local supersaturation and instantaneous heat release by feeding in batches, maintains the homogeneous phase of a reaction system, improves the process controllability and safety, and simultaneously obtains crystals with uniform particle size by alcohol precipitation crystallization, is easy to separate, and can obtain a high-purity and low-moisture bio-based nylon 4T salt product by matching with the mild drying condition of the application.

Inventors

  • SHI XIAOYAN
  • GAO ZHIKUN
  • JIANG TAO

Assignees

  • 华润化学材料科技股份有限公司

Dates

Publication Date
20260512
Application Date
20260203

Claims (10)

  1. 1. A method for preparing bio-based nylon 4T salt, comprising the steps of: (A) Mixing 1, 4-butanediamine with an aqueous solution containing alcohol to form a reaction base solution, and adding terephthalic acid into the reaction base solution in batches to perform a neutralization reaction to generate a soluble nylon 4T salt intermediate product; (B) Adding a precipitator into the nylon 4T salt intermediate product solution for alcohol precipitation to crystallize and separate out the nylon 4T salt, and carrying out solid-liquid separation and washing on the separated crystals to obtain the nylon 4T salt.
  2. 2. The preparation method of the bio-based nylon 4T salt according to claim 1, wherein the mass fraction of the alcohol in the alcohol-containing aqueous solution is 30% -40% wt, and the mass of the alcohol is 7-7.5 times of the mass of the 1, 4-butanediol; preferably, when terephthalic acid is added into the reaction base solution in batches, the total amount of the terephthalic acid added in each batch is 10-15%, and after each batch is added, the reaction system is clarified and then the next batch is put into; Preferably, the temperature of the neutralization reaction is controlled to be 40-60 ℃, and the pH value of the reaction end point is 7.2-7.5.
  3. 3. The method for preparing the bio-based nylon 4T salt according to claim 1, wherein the precipitant is one or more selected from methanol, ethanol, isopropanol or n-butanol; Preferably, the precipitant is introduced into the bottom of the solution as a gas-liquid mixture by a nitrogen-sparge stirrer as the precipitant is added; Preferably, the reaction temperature of the alcohol precipitation is 20-40 ℃ and the time is 1.0-2.0 h.
  4. 4. The method for preparing a biobased nylon 4T salt according to claim 1, wherein the step of solid-liquid separating and washing the precipitated crystals comprises: and standing for 0.5-1.0 h after alcohol precipitation is finished, layering solid and liquid, discharging supernatant, sending the bottom suspension into a rotary vacuum filter press for filtering, and washing a filter cake with alcohol for 1-2 times to obtain nylon 4T salt.
  5. 5. The method for producing a biobased nylon 4T salt according to claim 1, further comprising a step of recovering an organic solvent component in a filtrate and/or a washing liquid containing the organic solvent produced when the crystals precipitated in the step (B) are subjected to solid-liquid separation and washing, by membrane separation, and returning at least a part of the recovered organic solvent to the alcohol precipitation and/or washing step for recycling.
  6. 6. The method for preparing the bio-based nylon 4T salt according to claim 1, further comprising the step of vacuum drying the nylon 4T salt of the step (B) to obtain a fine nylon 4T salt; Preferably, the temperature of the vacuum drying is 40-60 ℃ and the time is 6-12 hours.
  7. 7. The preparation method of the bio-based nylon 4T salt according to any one of claims 1 to 6, wherein a production system for implementing the preparation method of the bio-based nylon 4T salt comprises a neutralization reaction kettle (1), an alcohol precipitation tank (2), a rotary vacuum filter (4), a vacuum drying oven (5), a primary membrane separation device (6), a secondary membrane separation device (7), an alcohol-water storage tank (8) and a recycled alcohol storage tank (10), wherein: A neutralization reaction kettle (1) for mixing 1, 4-butanediamine with an aqueous solution containing alcohol and receiving terephthalic acid added in batches for neutralization reaction; The alcohol precipitation tank (2) is communicated with the neutralization reaction kettle (1) through a pipeline and is used for receiving the neutralized solution and adding a precipitant for crystallization precipitation; The rotary vacuum filter (4) is connected with a bottom discharge port of the alcohol precipitation tank (2) and is used for filtering and alcohol washing precipitated crystals; Nylon 4T salt obtained at the discharge end of the rotary vacuum filter (4) is manually transferred to a vacuum drying oven (5) for vacuum drying; the first-stage membrane separation device (6) and the second-stage membrane separation device (7) are respectively connected with a filtrate outlet and an alcohol washing liquid outlet of the rotary vacuum filter (4) and are used for carrying out step separation on liquid containing organic solvent; The alcohol-water storage tank (8) is connected with a permeate outlet of the primary membrane separation device (6) and is used for storing dilute alcohol-water solution which can be reused for preparing reaction base solution; the recycling alcohol storage tank (10) is connected with a concentrated solution outlet of the secondary membrane separation device (7) and is used for storing high-purity recycling alcohol and supplying the high-purity recycling alcohol to the alcohol precipitation tank (2) and/or the rotary vacuum filter (4) for recycling.
  8. 8. The method for preparing biobased nylon 4T salt according to claim 7, characterized in that the alcohol precipitation tank (2) is provided with a nitrogen blowing stirrer (2 b) which is introduced into the tank in the form of a gas-liquid mixture from a recycled alcohol storage tank (10) or an externally fed alcohol precipitant through a small Kong Jianglai at the bottom of the hollow shaft body; preferably, a U-shaped pipe (2 e) is arranged outside the alcohol precipitation tank (2), one end of the U-shaped pipe is connected with the upper part of the side wall of the tank body, and the other end of the U-shaped pipe is provided with a plurality of liquid discharge outlets with stop valves distributed along the height direction and used for selectively discharging supernatant after standing and sedimentation; preferably, the production system further comprises a fresh alcohol storage tank (9), the fresh alcohol storage tank (9) being connected to the feed inlet of the alcohol precipitation tank (2) for replenishing precipitant.
  9. 9. The preparation method of the bio-based nylon 4T salt according to claim 7, wherein the neutralization reaction kettle (1) is provided with a rotary valve (1 d) and a weighing module for controlling the batch addition amount of terephthalic acid.
  10. 10. The method for preparing the bio-based nylon 4T salt according to claim 7, wherein a transfer pump is arranged between the alcohol precipitation tank (2) and the rotary vacuum filter (4) for transferring the high-concentration suspension; preferably, the transfer pump is a screw pump (3).

Description

Preparation method of bio-based nylon 4T salt Technical Field The invention relates to the technical field of nylon synthesis, in particular to a preparation method of bio-based nylon 4T salt. Background Nylon 4T (PA 4T) is a high-performance semi-aromatic polyamide material prepared by polycondensation reaction of 1, 4-butanediamine (DBA) and terephthalic acid (PTA) as raw materials. It has been widely used in the fields of electronics and electricity, automobiles and high-end industries because of its high crystallinity, excellent high temperature resistance, mechanical strength, ultra-low water absorption, good dimensional stability and lead-free soldering compatibility. The bio-based nylon 4T refers to the key monomer 1, 4-butanediamine of the bio-based nylon 4T is derived from a biomass fermentation process, is not a full-chain petroleum route, and accords with the production concept of green sustainable development. However, PA4T has a melting point higher than its decomposition temperature and cannot be directly melt-processed, so that commercial products are mostly copolymerized with PA66 and/or PA6 to lower the melting point, thereby realizing practical application. Industrially, a three-stage production process of salt formation, prepolymerization and final polymerization is generally adopted for PA4T, wherein nylon 4T salt is used as a polycondensation precursor, DBA and PTA can be ensured to participate in the reaction in an equimolar ratio, side reaction is reduced, and control of the polymerization process and stability of product quality are facilitated. In addition, compared with 1, 4-butanediamine which is volatile and has certain toxicity, the nylon 4T salt is easier to store and transport, has higher safety, and can remarkably reduce the storage and logistics cost. At present, the synthesis of nylon salt mainly adopts a water phase neutralization method, an organic solvent method or a solvent-free method. The common technological concept is that the dibasic acid and diamine are subjected to neutralization reaction in a water phase or an organic phase under the condition of equal molar ratio, and then the high-purity nylon salt crystal is obtained through the steps of crystallization, filtration, drying and the like. The specific method comprises an aqueous solution-crystallization method, an organic solvent-crystallization method and a solvent-free salification method. For example, CN118496104A in the prior art discloses a green preparation method of bio-based semi-aromatic nylon 5X salt, which comprises the steps of dropwise adding a bio-based pentanediamine aqueous solution into an aromatic diacid suspension under the protection of inert gas, assisting in ultrasonic and/or microwave enhanced mass transfer, cooling and crystallizing, adding a seed crystal for leaching and filtering, and finally drying to obtain refined salt. CN113698288a discloses a method and a device for continuously preparing powdered nylon salt, and the nylon salt solution after adjusting the pH is quickly evaporated to solvent by spray drying technology, and the powdered product is directly obtained. CN101456804B proposes a semi-aromatic nylon salt obtained by performing neutralization reaction in an organic solvent such as N-methylpyrrolidone (NMP) or Dimethylformamide (DMF), and washing the precipitate after centrifugal separation. CN115725072a discloses a preparation method of nylon dry salt, the diacid and diamine are directly supplied into a double screw extruder, mixed and reacted under the condition of no solvent and extruded, and the nylon dry salt with the water content lower than 20 wt% is obtained. However, the above method has significant limitations when applied to nylon 4T salt synthesis. Firstly, terephthalic acid is indissolvable in water at normal temperature and pressure, the solubility in methanol is only 1.01 g/100g, and if 1, 4-butanediamine solution is added into PTA suspension liquid in a dropwise manner, the mass transfer effect is poor, and the generated nylon salt possibly wraps the incompletely reacted PTA, so that the purity of the product is affected. Secondly, if an organic solvent system such as NMP or DMF is adopted, the solubility can be improved, but the subsequent solvent recovery energy consumption is high, the production cost is increased, and the risk of environmental pollution exists. And when the purification is carried out by adopting a cooling or evaporating crystallization mode, the solubility of the nylon 4T salt in water is less changed along with the temperature (the solubility of the nylon 4T salt is reduced from 60 ℃ to 5 ℃ and only reduced from 59.32g/100g of water to 41.18g/100g of water), so that the crystallization output is limited and the energy consumption is high. Finally, although the solvent-free salification method omits a crystallization process, the operation is simple, the raw material proportion is difficult to precisely control because the 1, 4-butanedi