Method for preparing low-viscosity bisphenol A epoxy resin

Abstract

The invention provides a method for preparing low-viscosity bisphenol A epoxy resin, and relates to the field of high polymer material preparation. The method comprises the step of reacting bisphenol A with epoxy chloropropane in the presence of a palladium compound modified quaternary ammonium salt catalyst to prepare the bisphenol A epoxy resin. The palladium compound modified quaternary ammonium salt catalyst has the effect of enabling epoxy chloropropane to be subjected to effective ring opening, the ring opening rate can be increased, the use amount of epoxy chloropropane is reduced, and due to the fact that the ring opening rate is increased, low-molecular-weight and low-viscosity epoxy resin can be synthesized more easily. Meanwhile, other comprehensive properties (mechanical properties and heat resistance) are not obviously reduced. The method disclosed by the invention has the characteristics of high reaction efficiency and excellent comprehensive performance of the product.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials and relates to a preparation method of polymer materials, in particular to a preparation method of bisphenol A epoxy resin. Background Art

[0002] Epoxy resin is widely used in the power industry due to its excellent mechanical strength and electrical insulation properties. It is an important insulating material for power electronic packaging devices, GIS, and other equipment. Currently, domestic bisphenol A epoxy resin lags significantly behind foreign counterparts in terms of micromolecular weight distribution and macroscopic properties. For example, the resin's high viscosity makes it difficult to flow and has poor workability on the construction site. Large amounts of solvents and reactive diluents are generally added to reduce its viscosity. Most solvents are toxic, flammable, and explosive, posing a risk to production safety and polluting the environment. Furthermore, the addition of most reactive diluents can be highly irritating to the skin and can reduce the product's mechanical and thermal properties to a certain extent.

[0003] To obtain epoxy resins with low viscosity and excellent overall performance, existing resins can be modified and then blended or copolymerized with new modifiers to produce material systems with excellent overall performance. This is an important and effective way to achieve high performance and multifunctionality of resins and develop new materials. Organosilicon modification is one of the common low-viscosity modification methods. Currently, the main approaches for modifying epoxy resins with organosilicon include reactive end group reactions, generating block copolymers using siloxane coupling agents, replacing some side groups of siloxanes, and pre-preparing polysiloxane particles. However, due to the significant difference in the solubility parameters of silicone rubber and organosilicones with epoxy resins, simple blending results in excessive interfacial tension between the two phases, large dispersed phase domains, and poor modification results.

[0004] On the other hand, reducing viscosity by improving the preparation process of bisphenol A epoxy resin is also a commonly used method. Patent CN117186359A discloses a method for preparing a high-purity, low-viscosity, non-crystallizing epoxy resin. The preparation steps include adding liquid caustic soda to a bisphenol A / epichlorohydrin solution once to obtain a first reaction solution after reaction; adding liquid caustic soda to the first reaction solution a second time, and obtaining a crude product after purification after the reaction is completed; and distilling the crude product to obtain a high-purity, low-viscosity, non-crystallizing epoxy resin. This method obtains an epoxy resin with a high organic chlorine content by controlling the amount of caustic soda added, making the epoxy resin high in purity, low in viscosity, and non-crystallizing. However, the efficiency of the liquid caustic soda catalyzed reaction is low, and the post-processing method of this method is complex and requires strict control of distillation conditions, resulting in a still high viscosity product.

[0005] The document "Synthesis and Characterization of Low-Viscosity, Easy-to-Mix Bisphenol A-Type Resin" discloses a method for synthesizing a bisphenol A-type epoxy resin. The method involves adding a certain amount of bisphenol A to a four-necked flask equipped with an electric stirrer, a thermometer, and a reflux condenser. An appropriate amount of epichlorohydrin is added, stirred, and heated to 40°C to completely dissolve the bisphenol A. An appropriate amount of tetramethylammonium bromide is then added and etherified at 80°C for 5 hours. The temperature is then lowered to 50°C, and 0.3 mol of a 30% NaOH solution is added dropwise, allowing the reaction to proceed for 5 hours. After the reaction is complete, excess epichlorohydrin is recovered under reduced pressure. The reaction solution is then poured into a clean four-necked flask, an appropriate amount of toluene is added, the temperature is raised to 65°C, and stirred to fully dissolve the bisphenol A. Finally, 0.2 mol of a 30% NaOH solution is added and allowed to react for 5 hours. After completion, the flask contents were washed with 65°C deionized water until neutral. The organic layer was separated and filtered into a 250mL stoppered ground-mouth bottle. An appropriate amount of anhydrous sodium sulfate was added to the filtrate, which was then covered and allowed to stand for 12 hours. The anhydrous sodium sulfate was filtered out and the mixture was subjected to vacuum distillation at 92.5 kPa and 20-100°C to obtain a transparent, impurity-free bisphenol A epoxy resin. The bisphenol A product was added to a four-necked flask equipped with an electric stirrer, a thermometer, and a reflux condenser. An appropriate amount of epichlorohydrin was added and stirred. The mixture was heated until the bisphenol A product was completely dissolved. An appropriate amount of oxalic acid was added and formaldehyde was added dropwise at 70°C (1 drop every 10 seconds) over a period of 2 hours. The temperature was then raised to 75-80°C and the reaction was continued for 4 hours. After the reaction was complete, an appropriate amount of tetramethylammonium bromide was added and the mixture was etherified at 80°C for 3 hours. The temperature was then lowered to 45°C and an alkali solution was added dropwise, with the reaction maintained for 3 hours. After the reaction is completed, the liquid in the flask is washed with 65°C deionized water and adjusted to neutrality. The organic layer is separated and filtered into a 250mL ground-mouth bottle with a stopper. An appropriate amount of anhydrous sodium sulfate is added to the filtrate. After 1 hour, the anhydrous sodium sulfate is filtered out and vacuum distillation is performed to obtain a transparent, impurity-free bisphenol A linear novolac epoxy resin.

[0006] The above method involves two reaction processes, and the steps are lengthy and complicated, time-consuming, and unfavorable for industrial production.

[0007] Furthermore, domestic companies often use ammonium salts as catalysts when preparing bisphenol A epoxy resin using a two-step process. This production process has the advantages of performing the ring-opening and ring-closing reactions in separate steps, allowing the ring-opening reaction to proceed in the absence of water, and providing a certain degree of catalyst selectivity. This method suppresses side reactions and reduces polymerization. However, a disadvantage of this process is that the catalyst has a certain emulsifying effect, making separation from the product difficult, significantly affecting product curing, and significantly shortening the service life of the cured epoxy resin.

[0008] In view of this, it is of great significance to improve the preparation method of bisphenol A epoxy resin to obtain a method with simple steps, which can obtain low-viscosity epoxy resin and easily separate the catalyst. Summary of the Invention

[0009] The present invention addresses the problems existing in the prior art and provides a method for preparing a low-viscosity bisphenol A epoxy resin. The method can further accelerate the reaction rate, reduce the amount of epichlorohydrin used, lower the degradation cost, synthesize a low-viscosity epoxy resin with excellent comprehensive properties such as heat resistance and mechanical properties, and can also reduce the difficulty of catalyst separation to a certain extent and simplify post-processing operations.

[0010] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0011] A method for preparing a low-viscosity bisphenol A epoxy resin comprises reacting bisphenol A with epichlorohydrin in the presence of a quaternary ammonium salt catalyst modified by a palladium compound to prepare the bisphenol A epoxy resin.

[0012] Furthermore, the palladium compound-modified quaternary ammonium salt catalyst is prepared by impregnating and modifying the quaternary ammonium salt with a palladium-containing compound.

[0013] Furthermore, the palladium-containing compound is selected from any one of palladium oxide, chloride, nitrate, sulfate and carbonate.

[0014] Furthermore, the palladium-containing compound is palladium chloride.

[0015] Furthermore, the quaternary ammonium salt is selected from any one of benzyltriethylammonium chloride, benzyltrimethylammonium chloride, tetrabutylammonium chloride, tetraethylammonium bromide, tetrabutylammonium bromide, and diethylammonium chloride.

[0016] Furthermore, the preparation method of the palladium compound modified quaternary ammonium salt catalyst comprises: mixing a sodium hydroxide solution, a palladium-containing compound, and a quaternary ammonium salt for a certain period of time to obtain the palladium compound modified quaternary ammonium salt catalyst.

[0017] Furthermore, the mass concentration of the sodium hydroxide solution is 2-10%.

[0018] Furthermore, the molar ratio of the sodium hydroxide, the palladium-containing compound, and the quaternary ammonium salt is (0.01-0.5):(0.001-0.1):1.

[0019] Furthermore, the mixing time is 10 min-2 h.

[0020] Furthermore, a method for preparing a low-viscosity bisphenol A epoxy resin comprises the following steps:

[0021] (1) mixing bisphenol A, epichlorohydrin, and a palladium compound-modified quaternary ammonium salt catalyst, and reacting for a certain period of time to obtain an etherification product;

[0022] (2) adding sodium hydroxide to the product of step (1) and reacting for a certain period of time to obtain a cyclization reaction product;

[0023] (3) heating to remove epichlorohydrin;

[0024] (4) adding toluene to dissolve, adding sodium hydroxide, and reacting for a certain time to obtain a crude product;

[0025] (5) post-treating the crude product to obtain the low-viscosity bisphenol A epoxy resin.

[0026] Furthermore, in step (1), the molar ratio of bisphenol A to epichlorohydrin is 1:(2-4); and the amount of the palladium compound-modified quaternary ammonium salt catalyst used is (0.2-0.4)% of the mass of bisphenol A.

[0027] Furthermore, the reaction temperature of step (1) is 70-90° C., and the reaction time is 3-5.5 h.

[0028] Furthermore, the molar ratio of sodium hydroxide to bisphenol A added in step (2) is (1-2.5):1, and the sodium hydroxide is preferably added dropwise.

[0029] Furthermore, the reaction temperature of step (2) is 50-55° C., the reaction pressure is 0.005-0.03 MPa, and the reaction time is 1-3 h.

[0030] Furthermore, in step (3), the temperature is raised to 130-150° C. to remove epichlorohydrin.

[0031] Furthermore, the molar ratio of sodium hydroxide to bisphenol A added in step (4) is (0.1-0.5):1.

[0032] Furthermore, the reaction temperature of step (4) is 70-90° C., and the reaction time is 1.5-3 h.

[0033] Furthermore, the post-treatment process in step (5) includes: adding an organic solvent and water to perform desalination at a certain temperature, adding an acidic compound to perform neutralization, washing with water, and removing the solvent to obtain a low-viscosity bisphenol A epoxy resin.

[0034] Furthermore, the organic solvent is preferably toluene; the desalination temperature is 60-80° C.; and the acidic compound is preferably phosphoric acid.

[0035] Furthermore, the post-treatment process of step (5) may also include: adding an organic reagent to dilute the crude product and filtering it, washing the filtrate with water until it is neutral, removing the organic reagent and water, adding ethyl acetate, filtering out the white solid to obtain a clear and transparent oily liquid, removing the ethyl acetate, and drying to obtain a low-viscosity bisphenol A epoxy resin.

[0036] Furthermore, the organic reagent is preferably methyl isobutyl ketone.

[0037] The low-viscosity bisphenol A epoxy resin prepared by the present invention can be further cured during use. The curing process is as follows: the resin can be cured using commonly used curing agents such as amines or acid anhydrides. For example, Me-THPA (methyltetrahydroaniline) is used to cure the modified epoxy resin. The epoxy resin and the curing agent are mixed in an equivalent ratio.

[0038] The specific curing process is as follows:

[0039] 1) After spraying the release agent, assemble the mold and place it in a 100-130℃ oven for preheating for 1.5-2.5h.

[0040] 2) Add the measured resin and curing agent into the reactor, stir and degas under vacuum for 20-40 minutes at a temperature of 100-120°C.

[0041] 3) Pour the castable into the preheated mold and place it in a vacuum box for degassing for 2-8 minutes.

[0042] 4) Place the mold in an oven for curing at 120-150°C for 15-35 hours.

[0043] The obtained solid epoxy resin was subjected to performance tests.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention uses a palladium-containing compound-modified quaternary ammonium salt catalyst. The palladium-containing compound has the effect of effectively opening the ring of epichlorohydrin, can accelerate the ring opening rate, reduce the usage of epichlorohydrin, and because the ring opening rate is accelerated, it is easier to synthesize low-molecular-weight, low-viscosity epoxy resins. At the same time, other comprehensive properties (mechanical properties and heat resistance) do not significantly decrease. It has the characteristics of high reaction efficiency and excellent product comprehensive performance. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of embodiments of the present invention, rather than all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. In addition, it is worth noting that the raw materials involved in the present invention are all common commercially available products unless otherwise specified.

[0047] Example 1

[0048] A sodium hydroxide solution with a mass fraction of 6% is mixed with palladium chloride and benzyltriethylammonium chloride, wherein the molar ratio of sodium hydroxide, palladium chloride and benzyltriethylammonium chloride is 0.1:0.01:1, and the mixture is uniformly mixed and allowed to stand for 30 minutes to prepare a modified catalyst.

[0049] 1) The molar ratio of bisphenol A to epichlorohydrin is 1:4, and the modified catalyst is used in an amount of 0.4% by weight of bisphenol A. The reaction is carried out at 80° C. for 5 hours to obtain an etherification product.

[0050] 2) Sodium hydroxide was added to the etherification product in an amount of BPA:NaOH=1:2 (mol). The reaction temperature was 55° C. and the pressure was 0.01 MPa. The reaction was continued for 2 hours after the addition of sodium hydroxide.

[0051] 3) Raise the temperature to 140℃ to remove water and epichlorohydrin until no liquid drips from the receiving bottle.

[0052] 4) Purification reaction: add toluene to dissolve (the amount of toluene should make the density of the "resin-toluene solution" less than the density of water), add sodium hydroxide, the amount of sodium hydroxide added is BPA:NaOH=1:0.2 (mol), the reaction temperature is 80°C, and the reaction is carried out at normal pressure for 1.5 hours.

[0053] 5) Post-treatment: adding toluene and water at 60-80°C for desalination, then adding phosphoric acid for neutralization, and washing with water until the upper layer solution becomes transparent, heating to 140-150°C for desolvation to obtain epoxy resin.

[0054] Example 2

[0055] A sodium hydroxide solution with a mass fraction of 3% is mixed with palladium chloride and benzyltriethylammonium chloride, wherein the molar ratio of sodium hydroxide, palladium chloride and benzyltriethylammonium chloride is 0.08:0.002:1, and the mixture is evenly mixed and allowed to stand for 10 minutes to prepare a modified catalyst.

[0056] 1) The equivalent ratio of bisphenol A to epichlorohydrin is 1:2, and the modified catalyst is used in an amount of 0.4% by weight of bisphenol A. The reaction is carried out at 80° C. for 5 hours to obtain an etherification product.

[0057] 2) Sodium hydroxide was added to the etherification product in an amount of BPA:NaOH=1:2 (mol). The reaction temperature was 55° C. and the pressure was 0.01 MPa. The reaction was continued for 2 hours after the addition of sodium hydroxide.

[0058] 3) Raise the temperature to 140℃ to remove water and epichlorohydrin until no liquid drips from the receiving bottle.

[0059] 4) Purification reaction: add toluene to dissolve (the amount of toluene should make the density of the "resin-toluene solution" less than the density of water), add sodium hydroxide, the amount of sodium hydroxide added is BPA:NaOH = 1:0.2 (mol), the reaction temperature is 80°C, and the reaction is carried out at normal pressure for 2 hours.

[0060] 5) Post-treatment: adding toluene and water at 60-80°C for desalination, then adding phosphoric acid for neutralization, and washing with water until the upper layer solution becomes transparent, heating to 140-150°C for desolvation to obtain epoxy resin.

[0061] Example 3

[0062] A sodium hydroxide solution with a mass fraction of 6% is mixed with palladium sulfate and benzyltrimethylammonium chloride, wherein the molar ratio of sodium hydroxide, palladium sulfate and benzyltrimethylammonium chloride is 0.1:0.01:1, and the mixture is uniformly mixed and allowed to stand for 30 minutes to prepare a modified catalyst.

[0063] 1) The molar ratio of bisphenol A to epichlorohydrin is 1:4, and the modified catalyst is used in an amount of 0.4% by weight of bisphenol A. The reaction is carried out at 80° C. for 5 hours to obtain an etherification product.

[0064] 2) Sodium hydroxide was added to the etherification product in an amount of BPA:NaOH=1:2 (mol). The reaction temperature was 55° C. and the pressure was 0.01 MPa. The reaction was continued for 2 hours after the addition of sodium hydroxide.

[0065] 3) Raise the temperature to 140℃ to remove water and epichlorohydrin until no liquid drips from the receiving bottle.

[0066] 4) Purification reaction: add toluene to dissolve (the amount of toluene should make the density of the "resin-toluene solution" less than the density of water), add sodium hydroxide, the amount of sodium hydroxide added is BPA:NaOH=1:0.2 (mol), the reaction temperature is 80°C, and the reaction is carried out at normal pressure for 1.5 hours.

[0067] 5) Post-treatment: adding toluene and water at 60-80°C for desalination, then adding phosphoric acid for neutralization, and washing with water until the upper layer solution becomes transparent, heating to 140-150°C for desolvation to obtain epoxy resin.

[0068] Example 4

[0069] A sodium hydroxide solution with a mass fraction of 8% is mixed with palladium oxide and tetrabutylammonium bromide, wherein the molar ratio of sodium hydroxide, palladium oxide and tetrabutylammonium bromide is 0.1:0.01:1, and the mixture is mixed evenly and allowed to stand for 20 minutes to prepare a modified catalyst.

[0070] 1) The molar ratio of bisphenol A to epichlorohydrin is 1:4, and the modified catalyst is used in an amount of 0.2% by weight of bisphenol A. The reaction is carried out at 80° C. for 5 hours to obtain an etherification product.

[0071] 2) Sodium hydroxide was added to the etherification product in an amount of BPA:NaOH=1:2 (mol). The reaction temperature was 55° C. and the pressure was 0.01 MPa. The reaction was continued for 2 hours after the addition of sodium hydroxide.

[0072] 3) Raise the temperature to 140℃ to remove water and epichlorohydrin until no liquid drips from the receiving bottle.

[0073] 4) Purification reaction: add toluene to dissolve (the amount of toluene should make the density of the "resin-toluene solution" less than the density of water), add sodium hydroxide, the amount of sodium hydroxide added is BPA:NaOH=1:0.2 (mol), the reaction temperature is 80°C, and the reaction is carried out at normal pressure for 1.5 hours.

[0074] 5) Post-treatment: adding toluene and water at 60-80°C for desalination, then adding phosphoric acid for neutralization, and washing with water until the upper layer solution becomes transparent, heating to 140-150°C for desolvation to obtain epoxy resin.

[0075] Example 5

[0076] A sodium hydroxide solution with a mass fraction of 6% is mixed with palladium chloride and tetrabutylammonium chloride, wherein the molar ratio of sodium hydroxide, palladium chloride and tetrabutylammonium chloride is 0.1:0.05:1, and the mixture is evenly mixed and allowed to stand for 30 minutes to prepare a modified catalyst.

[0077] 1) The molar ratio of bisphenol A to epichlorohydrin is 1:4, and the modified catalyst is used in an amount of 0.4% by weight of bisphenol A. The reaction is carried out at 80° C. for 5 hours to obtain an etherification product.

[0078] 2) Sodium hydroxide was added to the etherification product in an amount of BPA:NaOH=1:2 (mol). The reaction temperature was 55° C. and the pressure was 0.01 MPa. The reaction was continued for 2 hours after the addition of sodium hydroxide.

[0079] 3) Raise the temperature to 140℃ to remove water and epichlorohydrin until no liquid drips from the receiving bottle.

[0080] 4) Purification reaction: add toluene to dissolve (the amount of toluene should make the density of the "resin-toluene solution" less than the density of water), add sodium hydroxide, the amount of sodium hydroxide added is BPA:NaOH=1:0.2 (mol), the reaction temperature is 80°C, and the reaction is carried out at normal pressure for 1.5 hours.

[0081] 5) Post-treatment: Methyl isobutyl ketone was added to dilute the crude product and filtered, the filtrate was washed with water until neutral, the methyl isobutyl ketone and water were removed, ethyl acetate was added, and the white solid was removed by filtration to obtain a clear and transparent oily liquid, the ethyl acetate was removed, and the epoxy resin was obtained by drying.

[0082] Comparative Example

[0083] 1) The equivalent ratio of bisphenol A to epichlorohydrin is 1:4, and unmodified benzyltriethylammonium chloride is used as a catalyst in an amount of 0.4% by weight of bisphenol A. The reaction is carried out at 80° C. for 5 hours to obtain an etherification product.

[0084] 2) Sodium hydroxide was added to the etherification product in an amount of BPA:NaOH=1:2 (mol). The reaction temperature was 55° C. and the pressure was 0.01 MPa. The reaction was continued for 2 hours after the addition of sodium hydroxide.

[0085] 3) Raise the temperature to 140℃ to remove water and epichlorohydrin until no liquid drips from the receiving bottle.

[0086] 4) Purification reaction: After dissolving in toluene (the amount of toluene should be such that the density of the "resin-toluene solution" is less than the density of water), sodium hydroxide is added in an amount of BPA:NaOH = 1:0.2 (mol). The reaction temperature is 80°C and the reaction is carried out at normal pressure for 1.5 hours.

[0087] 5) Post-treatment: adding toluene and water at 60-80°C for desalination, then adding phosphoric acid for neutralization, and washing with water until the upper layer solution becomes transparent, heating to 140-150°C for desolvation to obtain epoxy resin.

[0088] Performance Testing

[0089] The performance comparison of the epoxy resins synthesized in the above examples and comparative examples is shown in the following table. Among them, the viscosity test is based on GB / T 22314-2008, using a GEMINI200 rheometer (Netzsch, Germany), and the shear stress is constant at 10Pa. The tensile strength test is based on the international standard ISO 527-1:1993, using a universal testing machine. The impact strength test is based on the international standard ISO-179-1:2010, using an impact strength tester. The glass transition temperature test is based on the international standard ISO11357-2-2014, measured by differential scanning calorimetry (DSC-60plus, Shimadzu, Japan), the mass of the sample to be tested is about 6 mg, the test temperature range is 25-260°C, and the nitrogen purge rate is 50 mL / min.

[0090]

[0091] The above results show that the epoxy resin prepared according to the present invention has the characteristics of low viscosity and excellent comprehensive performance, which is conducive to the compounding of epoxy resin with various fillers, fibers, etc. and their subsequent processing, and improves the performance of epoxy cured products and their composite materials.

[0092] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a low-viscosity bisphenol A epoxy resin, comprising reacting bisphenol A with epichlorohydrin in the presence of a quaternary ammonium salt catalyst modified by a palladium compound to prepare the bisphenol A epoxy resin.

2. The method according to claim 1, characterized in that The palladium compound-modified quaternary ammonium salt catalyst is prepared by impregnating and modifying the quaternary ammonium salt with a palladium-containing compound.

3. The method according to claim 1, characterized in that The preparation method of the palladium compound modified quaternary ammonium salt catalyst comprises: mixing a sodium hydroxide solution, a palladium-containing compound and a quaternary ammonium salt for a certain time to obtain the palladium compound modified quaternary ammonium salt catalyst.

4. The method according to claim 3, characterized in that The palladium-containing compound is selected from one or more of palladium oxide, chloride, nitrate, sulfate and carbonate.

5. The method according to claim 4, characterized in that The palladium-containing compound is palladium chloride.

6. The method according to claim 3, characterized in that The quaternary ammonium salt is selected from one or more of benzyltriethylammonium chloride, benzyltrimethylammonium chloride, tetrabutylammonium chloride, tetraethylammonium bromide, tetrabutylammonium bromide, and diethylammonium chloride.

7. The method according to claim 3, characterized in that The mass concentration of the sodium hydroxide solution is 2-10%, the molar ratio of the sodium hydroxide, the palladium-containing compound and the quaternary ammonium salt is (0.01-0.5):(0.001-0.1):1, and the mixing time is 10 minutes to 2 hours.

8. The method according to any one of claims 1 to 7, characterized in that The method for preparing low-viscosity bisphenol A epoxy resin specifically comprises the following steps: (1) mixing bisphenol A, epichlorohydrin, and a palladium compound-modified quaternary ammonium salt catalyst, and reacting for a certain period of time to obtain an etherification product; (2) adding sodium hydroxide to the product of step (1) and reacting for a certain period of time to obtain a cyclization reaction product; (3) heating to remove epichlorohydrin; (4) adding toluene to dissolve, adding sodium hydroxide, and reacting for a certain time to obtain a crude product; (5) post-treating the crude product to obtain the low-viscosity bisphenol A epoxy resin.

9. The method according to claim 8, characterized in that In step (1), the molar ratio of bisphenol A to epichlorohydrin is 1:(2-4), the amount of the palladium compound-modified quaternary ammonium salt catalyst is (0.2-0.4)% of the mass of bisphenol A, and the molar ratio of sodium hydroxide to bisphenol A added in step (2) is (1-2.5):

1.

10. The method according to claim 8, characterized in that The reaction temperature of step (1) is 70-90° C., and the reaction time is 3-5.5 h.

11. The method according to claim 8, characterized in that The reaction temperature of step (2) is 50-55° C., the reaction pressure is 0.005-0.03 MPa, and the reaction time is 1-3 h.

12. The method according to claim 8, characterized in that The molar ratio of sodium hydroxide to bisphenol A added in step (4) is (0.1-0.5):1, the reaction temperature of step (4) is 70-90° C., and the reaction time is 1.5-3 hours.

13. The method according to claim 8, characterized in that The post-treatment process in step (5) includes: adding an organic solvent and water to perform desalination at a certain temperature, adding an acidic compound to perform neutralization, washing with water, and removing the solvent to obtain a low-viscosity bisphenol A epoxy resin.

Images