Preparation method of low-chlorine high-purity bisphenol A type liquid epoxy resin

Abstract

The application discloses a preparation method of low-chlorine high-purity bisphenol A type liquid epoxy resin. The method comprises the following steps: mixing raw materials containing epichlorohydrin, bisphenol A and a cosolvent, adding a catalyst A, and performing etherification reaction under low-temperature condition of not more than 50 DEG C; recovering unreacted epichlorohydrin in the system after the reaction is completed to obtain an etherification product; mixing the etherification product with a solvent, adding a catalyst B, and performing ring-closing reaction under low-temperature condition of not more than 50 DEG C; performing extraction separation on the obtained reaction product to obtain an organic phase; and performing desolventizing treatment on the organic phase to obtain the bisphenol A type liquid epoxy resin product. The total chlorine content of the obtained bisphenol A type liquid epoxy resin product is low, the viscosity is low, the purity is high, the quality is good, the preparation method is simple, the process flow is short, and the cost is low.

Description

Technical Field

[0001] This invention relates to a resin preparation method, specifically a method for preparing a low-chlorine, high-purity bisphenol A type liquid epoxy resin, belonging to the field of fine chemical synthesis technology. Background Technology

[0002] Epoxy resins are an important class of thermosetting resins with wide applications ranging from high-end aerospace to basic daily life, and are essential chemical materials supporting national economic and social development. Currently, bisphenol A type epoxy resins still dominate the epoxy resin market in my country, accounting for approximately 80.1% and 79.4% of the total domestic production and consumption, respectively.

[0003] Although the synthesis of bisphenol A epoxy resins has been improved step by step both domestically and internationally, the basic epoxy resins used for high-purity, low-viscosity, and other high-performance epoxy resins still cannot meet the requirements, and imports are still the main source of supply. Therefore, developing high-purity, low-viscosity, low-chlorine or chlorine-free high-quality epoxy resins to meet the requirements of the electronics, communications, optoelectronics, and artificial intelligence industries for epoxy resin systems is currently a key focus of research.

[0004] The main process for producing bisphenol A type liquid epoxy resin involves reacting bisphenol A with epichlorohydrin under the action of a catalyst to generate bisphenol A dichlorohydrin ether, then adding an aqueous sodium hydroxide solution to the system for a cyclization reaction, followed by epichlorohydrin recovery, purification, and finally solvent removal to obtain bisphenol A type liquid epoxy resin. However, this process has a long production cycle, high reaction temperature, and vigorous reaction, resulting in numerous side reactions. In addition, the epichlorohydrin recovery process is at a high temperature, and the system contains a large amount of sodium chloride, which easily leads to the formation of a large number of epichlorohydrin side reactions, affecting product performance.

[0005] Therefore, it is necessary to develop a new method for preparing low-chlorine, high-purity bisphenol A type liquid epoxy resin, which has a series of advantages such as simple operation, low energy consumption, and good product performance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, such as poor product performance and complex operating procedures, the present invention aims to provide a method for preparing low-chlorine, high-purity bisphenol A type liquid epoxy resin. The resin product obtained by this method has a total chlorine content ≤1000ppm, a viscosity ≤10000CP (25℃), and a purity ≥90%. The process is short and cost-effective.

[0007] To achieve the above-mentioned technical objectives, this invention provides a method for preparing low-chlorine, high-purity bisphenol A type liquid epoxy resin. The method involves mixing raw materials including epichlorohydrin, bisphenol A, and a cosolvent, adding catalyst A, and carrying out an etherification reaction at a low temperature of 40–50°C. After the reaction, unreacted epichlorohydrin is recovered from the system to obtain the etherified product. The etherified product is then mixed with a solvent, and catalyst B is added to carry out a ring-closing reaction. The resulting reaction product is extracted and separated to obtain an organic phase. The organic phase is then desolventized to obtain the final product.

[0008] This invention first improves the efficiency of etherification reaction and reduces by-products through low-temperature etherification reaction, and the reaction process is easy to control. Secondly, before the ring-closure reaction, the excess unreacted epichlorohydrin raw material in the etherification reaction product is recovered, which avoids the generation of a large amount of by-products due to the reaction of large amounts of sodium chloride with epichlorohydrin after the ring-closure reaction, thus improving product purity. At the same time, the ring-closure reaction is carried out under low-temperature conditions, which can further reduce the generation of side reactions and greatly improve product purity.

[0009] As a preferred embodiment, the molar ratio of epichlorohydrin to bisphenol A is 5–10:1. Controlling the amount of epichlorohydrin within a suitable range is beneficial to improving preparation efficiency; excessive amounts will lead to increased energy consumption for epichlorohydrin recovery after the etherification reaction.

[0010] As a preferred embodiment, the co-solvent includes at least one of propylene glycol methyl ether, polyether, cyclic crown ether, quaternary ammonium salt, quaternary ammonium base, and quaternary phosphine salt. The co-solvent promotes better dissolution of bisphenol A, epichlorohydrin, and the catalyst, ensuring the reaction proceeds in a homogeneous system.

[0011] As a preferred embodiment, the mass ratio of the cosolvent to bisphenol A is 1 to 2:10.

[0012] As a preferred embodiment, catalyst A is an alkaline catalyst solution.

[0013] As a preferred embodiment, the alkaline catalyst comprises at least one of quaternary ammonium salt, sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

[0014] As a preferred embodiment, the molar ratio of catalyst A to bisphenol A is 0.2–0.5:1. Controlling the amount of catalyst A within a reasonable range is beneficial to improving reaction efficiency; too low an amount will reduce the etherification reaction efficiency, while too high an amount will result in resource waste and increased processing costs.

[0015] As a preferred embodiment, the mass concentration of catalyst A is 15-50%, more preferably 15-30%.

[0016] As a preferred embodiment, the etherification reaction conditions are: a protective atmosphere, a temperature of 40–50°C, and a time of 2–6 hours. More preferably, the etherification reaction temperature is 40–45°C, and the etherification reaction time is 4–6 hours. The protective atmosphere is an inert gas atmosphere.

[0017] As a preferred approach, after the etherification reaction is completed, unreacted epichlorohydrin in the system is recovered by vacuum distillation.

[0018] As a preferred embodiment, the temperature of the vacuum distillation is 100–160°C and the pressure is 10–50 kPa.

[0019] As a preferred embodiment, catalyst B is an alkaline catalyst solution.

[0020] As a preferred embodiment, the alkaline catalyst comprises at least one of quaternary ammonium salt, sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

[0021] As a preferred embodiment, the molar ratio of catalyst B to bisphenol A is 1.8–2:1. Controlling the amount of catalyst B within a suitable range is beneficial for improving reaction efficiency and product quality. When the amount of catalyst B is too low, the ring-closing reaction will be incomplete, resulting in the presence of unclosed ring substances in the system, and the efficiency of chlorine removal by hydrolysis will be relatively reduced. Conversely, when the amount of catalyst is too high, not only will the amount of waste polymers generated by the reaction increase, but the excessive alkaline solution will also increase the wastewater discharge and raise wastewater treatment costs.

[0022] As a preferred embodiment, the mass concentration of catalyst B is 15-50%, more preferably 15-30%.

[0023] As a preferred embodiment, the solvent includes at least one of toluene, xylene, methyl isobutyl ketone, ethyl acetate, and cyclohexane.

[0024] As a preferred embodiment, the mass ratio of the solvent to bisphenol A is 1 to 2:1.

[0025] As a preferred embodiment, the closed-loop reaction conditions are: temperature 40–50°C, pressure 10–20 kPa, and time 2–4 h. A further preferred closed-loop reaction temperature is 40–45°C.

[0026] As a preferred embodiment, the extractant used in the extraction and separation process includes at least one of toluene, xylene, methyl isobutyl ketone, ethyl acetate, and cyclohexane.

[0027] As a preferred embodiment, the mass ratio of the extractant to bisphenol A is 1 to 2:1.

[0028] As a preferred embodiment, the solvent removal process is as follows: vacuum distillation is carried out at 100–160°C and 10–50 kPa to obtain low-chlorine, high-purity bisphenol A type liquid epoxy resin.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) By controlling the etherification reaction to be carried out at a low temperature of no more than 50°C, the etherification reaction time is increased, so that the bisphenol A reaction is more complete, side reactions are reduced, and the etherification rate of the reaction is increased.

[0031] (2) Before the ring-closing reaction, the excess epichlorohydrin raw material that has not been reacted in the etherification reaction product is separated and recovered, which effectively avoids the reaction of a large amount of sodium chloride generated after the ring-closing reaction with the epichlorohydrin remaining in the etherification reaction product to generate more by-products, and significantly improves product quality.

[0032] (3) Control the closed-loop reaction to be carried out at low temperature to further reduce by-products and improve product purity and quality;

[0033] (4) After the closed-loop reaction is completed, there is no need for further purification reaction. High-purity, low-chlorine epoxy resin products can be obtained directly through extraction separation and desolventization treatment, which greatly shortens the process and reduces production costs. Attached Figure Description

[0034] Figure 1 This is a process flow diagram of Embodiment 1 of the present invention. Detailed Implementation

[0035] The present invention is illustrated by the following embodiments, which do not constitute a limitation on the scope or implementation of the present invention.

[0036] In the following examples, the total chlorine content was determined using a Bruker SPECTROCUBE polarized energy dispersive X-ray fluorescence (ED-XRF) analyzer; the number-average molecular weight and molecular weight distribution of the polymer were determined using a Shimadzu LC-20AD liquid chromatography-gel permeation chromatography (GPC); and the viscosity of the epoxy resin was measured using a rotational viscometer. All indicators were determined according to the Q / SH 1085 007-2020 standard.

[0037] Example 1

[0038] Weigh 114.09g of bisphenol A, 370.08g of epichlorohydrin, and 0.0114g of polyethylene glycol and mix them evenly. Under a N2 protective atmosphere, heat to 42℃. After the bisphenol A is completely dissolved, add 50g of 20% sodium hydroxide solution and react for 5 hours to obtain the etherified reaction material. Under a vacuum of 10kPa and 160℃, recover excess epichlorohydrin to obtain 256g of etherified product. Add 120g of toluene and under a vacuum of 15kPa and 42℃, add 150g of 20% potassium hydroxide solution dropwise. After the alkali solution is added, continue the reaction for 4 hours. Then add 120g of methyl ethyl butyl ketone and hot water to the obtained reaction solution and wash with water 5 times until the pH is neutral. Take the upper organic phase and remove the solvent under a vacuum of 10kPa and 160℃ to obtain low-chlorine high-purity bisphenol A type liquid epoxy resin.

[0039] Product specifications analysis: Total chlorine is 785 ppm, viscosity is 8220 CP, and purity is 91.25%.

[0040] Example 2

[0041] 114.09 g of bisphenol A, 416.34 g of epichlorohydrin, and 0.0114 g of propylene glycol methyl ether were weighed and mixed evenly. Under a N2 protective atmosphere, the mixture was heated to 43°C. After the bisphenol A was completely dissolved, 50 g of 20% sodium hydroxide solution was added, and the reaction was carried out for 5 h to obtain the etherified reaction material. Excess epichlorohydrin was recovered at 160°C and 10 kPa vacuum to obtain 253.6 g of etherified product. 150 g of toluene was added, and 150 g of 20% potassium hydroxide solution was added dropwise at 42°C and 15 kPa vacuum. After the alkali solution was completely added, the reaction was continued for 4 h. Then, 150 g of toluene and hot water were added to the obtained reaction solution, and the mixture was washed with water 5 times until the pH was neutral. The upper organic phase was taken, and after solvent removal at 160°C and 10 kPa vacuum, low-chlorine high-purity bisphenol A type liquid epoxy resin was obtained.

[0042] Product specifications analysis: Total chlorine is 715 ppm, viscosity is 7985 CP, and purity is 91.85%.

[0043] Example 3

[0044] Weigh 114.09g of bisphenol A, 462.6g of epichlorohydrin, and 0.0114g of 18-crown-6 and mix them thoroughly. Under a N2 protective atmosphere, heat to 42℃ and heat until bisphenol A is completely dissolved. Then add 50g of 20% sodium hydroxide solution and react for 5 hours to obtain the etherified reaction material. Under a vacuum of 10kPa and 160℃, recover excess epichlorohydrin to obtain 255.2g of etherified product. Add 180g of toluene and under a vacuum of 15kPa and 42℃, add 150g of 20% potassium hydroxide solution dropwise. After the alkali solution is added, continue the reaction for 4 hours. Then add 180g of cyclohexane and hot water to the obtained reaction solution and wash with water 5 times until the pH is neutral. Take the upper organic phase and remove the solvent under a vacuum of 10kPa and 160℃ to obtain low-chlorine high-purity bisphenol A type liquid epoxy resin.

[0045] Product index analysis: Total chlorine is 705 ppm, viscosity is 7820 CP, and purity is 91.97%.

[0046] Comparative Example 1

[0047] The epoxy resin was prepared using the method of Example 1, except that the etherification temperature was controlled at 55°C.

[0048] Analysis of the product indicators under the comparative conditions showed that the total chlorine content was 1050 ppm, the viscosity was 10680 CP, and the purity was 84.17%. The results indicate that excessively high etherification temperatures led to a highly exothermic reaction, making the etherification temperature difficult to control, accelerating side reactions, and resulting in insufficient reaction of the raw material bisphenol A, thus reducing the etherification rate and consequently lowering the product purity.

[0049] Comparative Example 2

[0050] The epoxy resin was prepared using the method of Example 1, except that epichlorohydrin was not separated and recovered immediately after the etherification reaction, but was separated and recovered immediately after the ring-closing reaction, followed by extraction separation and solvent removal.

[0051] Analysis of the product indicators under the comparative conditions showed that the total chlorine was 1200 ppm, the viscosity was 12850 CP, and the purity was 81.95%. The results indicate that the large amount of sodium chloride produced after the ring-closing reaction reacts with the epichlorohydrin remaining in the etherification reaction products to generate more byproducts, leading to higher total chlorine and viscosity in the product.

[0052] Comparative Example 3

[0053] The epoxy resin was prepared using the method of Example 1, except that the ring-closing reaction temperature was controlled at 62°C.

[0054] Analysis of the product indicators under the comparative conditions showed that the total chlorine content was 1015 ppm, the viscosity was 10250 CP, and the purity was 84.75%. The results indicate that excessively high ring-closure reaction temperatures lead to the easy opening of the generated epoxy groups, resulting in increased byproducts, higher chlorine content, higher viscosity, and lower purity in the product.

Claims

1. A method for preparing a low-chlorine, high-purity bisphenol A type liquid epoxy resin, characterized in that: The raw materials, including epichlorohydrin, bisphenol A and a cosolvent, are mixed, and catalyst A is added. The reaction is carried out at a low temperature not exceeding 50°C. After the reaction, the unreacted epichlorohydrin in the system is recovered to obtain the etherified product. The etherified product is mixed with a solvent, and catalyst B is added. The reaction is carried out at a low temperature not exceeding 50°C. The resulting reaction product is extracted and separated to obtain an organic phase. The organic phase is then desolventized to obtain the final product. The molar ratio of epichlorohydrin to bisphenol A is 5~10:1; The co-solvent includes at least one of propylene glycol methyl ether, polyether, cyclic crown ether, quaternary ammonium salt, quaternary ammonium base, and quaternary phosphine salt; The mass ratio of the co-solvent to bisphenol A is 1~2:10; the catalyst A includes at least one of quaternary ammonium salt, sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate. The conditions for the etherification reaction are: protective atmosphere, temperature of 40~45℃, and time of 2~6h; The catalyst B includes at least one of quaternary ammonium salt, sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate. The conditions for the closed-loop reaction are: temperature 40~45℃, pressure 10~20kPa, and time 2~4h.

2. The method for preparing a low-chlorine, high-purity bisphenol A type liquid epoxy resin according to claim 1, characterized in that: The molar ratio of catalyst A to bisphenol A is 0.2~0.5:1; The mass concentration of catalyst A is 15-50%.

3. The method for preparing a low-chlorine, high-purity bisphenol A type liquid epoxy resin according to claim 1, characterized in that: The molar ratio of catalyst B to bisphenol A is 1.8~2:1; The mass concentration of catalyst B is 15-50%.

4. The method for preparing a low-chlorine, high-purity bisphenol A type liquid epoxy resin according to claim 1 or 3, characterized in that: The solvent includes at least one of toluene, xylene, methyl isobutyl ketone, ethyl acetate, and cyclohexane.

5. The method for preparing a low-chlorine, high-purity bisphenol A type liquid epoxy resin according to claim 1, characterized in that: The extractant used in the extraction and separation process includes at least one of toluene, xylene, methyl isobutyl ketone, ethyl acetate, and cyclohexane.

6. The method for preparing a low-chlorine, high-purity bisphenol A type liquid epoxy resin according to claim 1, characterized in that: After the etherification reaction is completed, unreacted epichlorohydrin in the system is recovered by vacuum distillation; the vacuum distillation temperature is 100~160℃ and the pressure is 10~50kPa.

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