Liquid bisphenol f-type epoxy resin and method for producing the same

Abstract

This application relates to the technical field of epoxy resin preparation, specifically disclosing a liquid bisphenol F type epoxy resin and its preparation method. The preparation method includes the following steps: S1: Under an inert atmosphere, phenol, catalyst A, and methanol are added to a reactor, the temperature is raised, some formaldehyde is added, the reaction proceeds, then catalyst B and the remaining formaldehyde are added, the reaction continues, solid-liquid separation is performed, neutralization is carried out, and purification is achieved to obtain bisphenol F; S2: Under an inert atmosphere, bisphenol F and toluene are mixed evenly, an acid-binding agent and trimethylchlorosilane are added, the reaction proceeds at 25-30°C, epichlorohydrin and a phase transfer catalyst are added, the temperature is raised, fluoride is added in portions over at least 45 minutes, the reaction continues, pH is dynamically adjusted, the reaction proceeds, washing is performed, the layers are separated, and purification is achieved to obtain the liquid bisphenol F type epoxy resin. The liquid bisphenol F type epoxy resin obtained in this application has the characteristics of moderate epoxy equivalent, low viscosity, and extremely low hydrolyzable chlorine content.

Description

Technical Field

[0001] This application relates to the technical field of epoxy resin preparation, and more specifically, to a liquid bisphenol F type epoxy resin and a method for preparing the same. Background Technology

[0002] Bisphenol F epoxy resins, due to their low viscosity, high flexibility, and strong impact resistance, have been widely used in electrical and electronic, rail transportation, and new energy fields, especially in specific applications such as wind turbine blades, electronic ducts, and adhesives. Bisphenol F is a mixture of three isomers: 4,4'-dihydroxydiphenylmethane (para-para isomer), 2,4'-dihydroxydiphenylmethane (ortho-para isomer), and 2,2'-dihydroxydiphenylmethane (ortho-ortho isomer). Existing research indicates that the isomer distribution significantly affects the performance of bisphenol F epoxy resins. Mainstream technologies pursue high 4,4'-dihydroxydiphenylmethane content, believing that higher 4,4'-dihydroxydiphenylmethane content is more beneficial for reducing resin viscosity and improving curing performance.

[0003] Patent application CN101429273 discloses a method for preparing wind power-grade bisphenol F epoxy resin. The method involves using formaldehyde and phenol as raw materials, and in an organic solvent, with phosphoric acid as a catalyst, performing phenolic condensation. The condensation is followed by recrystallization from toluene and freezing to obtain bisphenol F with a high para-4,4'-dihydroxydiphenylmethane content. Then, using the aforementioned bisphenol F and epichlorohydrin as raw materials, a ring-opening addition etherification reaction is first carried out in the presence of the quaternary ammonium salt benzyltrimethylammonium chloride catalyst to generate a bisphenol F dichlorohydrin ether intermediate. Next, solid alkali is added in batches to carry out a primary ring-closure epoxidation dechlorination reaction. After separating excess epichlorohydrin, a secondary ring-closure epoxidation dechlorination reaction is carried out with dilute alkali and toluene solvent. Finally, after processes such as toluene solvent crystallization, hot water washing, and vacuum drying, a bisphenol F epoxy resin product with high epoxy value and low viscosity is obtained. Dichloropropanol is added during the ring-opening etherification stage of bisphenol F and epichlorohydrin to generate bisphenol F dichlorohydrin ether.

[0004] In this technical solution, the preparation of high-purity 4,4'-dihydroxydiphenylmethane typically relies on recrystallization or special catalytic processes, which not only results in high production costs but also leads to significant waste treatment challenges due to the use of organic solvents such as toluene, making it difficult to meet the requirements of green and environmentally friendly industrialization. More importantly, blindly pursuing high 4,4'-dihydroxydiphenylmethane content can cause the resin molecular chains to become overly regular, significantly increasing brittleness after curing. Summary of the Invention

[0005] To obtain a liquid bisphenol F epoxy resin that combines low viscosity and high toughness, this application provides a liquid bisphenol F type epoxy resin and its preparation method, comprising the following steps: In a first aspect, this application provides a method for preparing liquid bisphenol F type epoxy resin, using the following technical solution: A method for preparing liquid bisphenol F type epoxy resin includes the following steps: S1: Under an inert atmosphere, phenol, catalyst A and methanol are added to the reactor, the temperature is raised to 60~70℃, some formaldehyde is added, the reaction is carried out for 1~2 hours, then catalyst B and the remaining formaldehyde are added, the reaction is carried out for 2~4 hours, solid-liquid separation is performed, neutralization is carried out, and purification is carried out to obtain bisphenol F. S2: Under an inert atmosphere, bisphenol F and toluene are mixed evenly, and an acid-binding agent and trimethylchlorosilane are added. After reacting at 25-30°C for 90-120 min, epichlorohydrin and a phase transfer catalyst are added, and the temperature is raised to 60-70°C. Fluoride is added in portions over a period of not less than 45 min, and the reaction continues for 90-120 min. The pH is dynamically adjusted to 10.5-11.0, and the reaction is carried out for 3-5 h. The mixture is washed, separated into layers, and purified to obtain liquid bisphenol F type epoxy resin. Catalyst A comprises silica-supported hafnium boron and oxalic acid; catalyst B is hydroxyapatite-supported lanthanum zinc; the phase transfer catalyst is a quaternary ammonium salt.

[0006] In this technical solution, during stage S1, the isomer distribution of bisphenol F is regulated by stepwise addition of hafnium boron supported on silica and lanthanum zinc supported on hydroxyapatite. The hafnium species on the surface of the hafnium boron supported on silica provide strong Lewis acidic sites, synergistically catalyzing the condensation reaction of phenol and formaldehyde with oxalic acid (a protic acid). The lanthanum zinc supported on hydroxyapatite, through the synergistic effect of lanthanum and zinc doping on its surface, participates in the catalysis of subsequent reaction stages. By stepwise addition of the two catalysts and control of the reaction conditions, the isomer distribution range of bisphenol F can be regulated.

[0007] In the initial stage of step S2, under low temperature conditions, the phenolic hydroxyl groups in the bisphenol F molecule are partially silanized and protected through the synergistic effect of the acid-binding agent and trimethylchlorosilane, with the remainder existing in free form. Subsequently, upon the addition of epichlorohydrin, the unprotected free phenolic hydroxyl groups begin to react during the heating process. Simultaneously, fluoride is slowly added over at least 60 minutes, and fluoride ions gradually catalyze the desaturation of the trimethylsilyl group, allowing the protected phenolic hydroxyl groups to be slowly released and participate in the reaction. This slow-release mechanism effectively avoids the violent local reactions, epichlorohydrin hydrolysis consumption, and increased byproducts caused by the instantaneous exposure of large amounts of phenolic hydroxyl groups, making the reaction more moderate and targeted.

[0008] Preferably, the molar ratio of phenol, formaldehyde, acid-binding agent, trimethylchlorosilane, epichlorohydrin and fluoride is (3~5):1:(0.8~1.4):(0.8~1.4):(5~8):(0.08~0.2).

[0009] In this technical solution, partial protection of the phenolic hydroxyl groups in bisphenol F is achieved by controlling the dosage of trimethylchlorosilane and the acid-binding agent. This dosage ensures that a sufficient number of hydroxyl groups are protected to achieve a sustained-release effect, while avoiding waste and subsequent deprotection burden caused by excessive protective reagents. Simultaneously, the dosage of fluoride is controlled at a catalytic level to ensure a moderate rate of deprotection reaction, achieving a gradual and controllable release of the protected phenolic hydroxyl groups.

[0010] Preferably, in step S1, the formaldehyde portion accounts for 40% to 60% of the total formaldehyde usage.

[0011] Preferably, in step S1, the bisphenol F contains 35% to 45% 4,4'-dihydroxydiphenylmethane, 35% to 45% 2,4'-dihydroxydiphenylmethane, and no more than 10% 2,2'-dihydroxydiphenylmethane.

[0012] In this technical solution, the bisphenol F in this ratio range is treated by the S2 step of the first protection and then slow release process, and the resulting liquid bisphenol F type epoxy resin has comprehensive properties such as moderate viscosity, good storage stability and high toughness.

[0013] Preferably, the mass ratio of 4,4'-dihydroxydiphenylmethane to 2,4'-dihydroxydiphenylmethane is (1.0~1.15):1.

[0014] Preferably, the 2,2'-dihydroxydiphenylmethane contains no more than 8% bisphenol F.

[0015] Preferably, the method for preparing the silicon dioxide-supported hafnium boron includes the following steps: Mesoporous silica was dispersed in water, a hafnium source was added and mixed evenly, the pH was adjusted to 8.5-9.5, and the mixture was soaked for 6-12 hours. The temperature was raised to 60-80℃ and aged for 2-4 hours. After cooling, the pH was adjusted to 7.5-8.0, a boron source was added and mixed evenly, the temperature was raised to 40-50℃ and the mixture was soaked for 3-6 hours. Solid-liquid separation was performed, followed by washing, drying, calcination at 500-550℃ for 2-3 hours, and cooling to obtain silica-supported hafnium boron.

[0016] Preferably, the mass ratio of the mesoporous silica, hafnium source and boron source is 100:(8~10):(3~5).

[0017] Preferably, the hafnium source is HfOCl2·8H2O.

[0018] Preferably, the boron source is H3BO3.

[0019] In this technical solution, mesoporous silica and a hafnium source are mixed under alkaline conditions. Hafnium ions are hydrolyzed and precipitated to form hafnium hydroxide, which is uniformly loaded onto the surface and pores of silica. After heating and aging, the hafnium species form chemical bonds with the carrier surface through dehydration condensation, resulting in a stable structure. Subsequently, the system is adjusted back to a weakly alkaline state, and a boron source is added. Boric acid bonds with surface hydroxyl groups through hydrogen bonding. After drying and calcination, the two are co-loaded on mesoporous silica in a highly dispersed state to obtain a hafnium-boron co-doped catalyst.

[0020] Preferably, the preparation method of the La-Zn dual-doped hydroxyapatite includes the following steps: Hydroxyapatite was dispersed in water, and lanthanum and zinc sources were added to adjust the pH to 8-9. The mixture was soaked for 6-12 hours, heated to 50-70℃, aged for 2-4 hours, separated from solids, washed, dried, calcined at 450-550℃ for 2-4 hours, and cooled to obtain La-Zn double-doped hydroxyapatite.

[0021] Preferably, the mass ratio of the hydroxyapatite, lanthanum source and zinc source is 100:(2~4):(6~8).

[0022] Preferably, the lanthanum source is lanthanum nitrate hexahydrate.

[0023] Preferably, the zinc source is zinc nitrate hexahydrate.

[0024] In this technical solution, hydroxyapatite is dispersed in water, and lanthanum and zinc sources are added to adjust the pH. Lanthanum and zinc ions hydrolyze to form hydroxide precipitates, which are uniformly loaded onto the surface and pores of the support. After heating and aging, the precipitate further bonds with the support surface; subsequent drying and calcination form stable doping sites. La doping can regulate the intensity of basic sites on the catalyst surface, while Zn doping can optimize the distribution of acidic sites. The two work synergistically to regulate the ortho- and para-reactive activity of phenol and stabilize the ratio of bisphenol F isomers.

[0025] Preferably, the inert atmosphere is a low-pressure inert atmosphere, and the pressure is 0.02~0.05MPa.

[0026] Preferably, in step S2, after neutralization, the following steps are also included: after separation, take the organic phase, add 3% to 5% of silanized nano-alumina by mass of the organic phase, heat to 50 to 55°C, react for 45 to 60 minutes, separate into layers, purify, and obtain liquid bisphenol F type epoxy resin.

[0027] Preferably, the method for preparing the silanized nano-alumina includes the following steps: Nano-alumina was uniformly dispersed in an ethanol aqueous solution, and silane coupling agents KH550 and KH560 were added and mixed evenly. The pH was adjusted to 4.0-5.0, the temperature was raised to 50-60℃, and the reaction was carried out for 3-4 hours. The solid and liquid were separated, washed, and dried to obtain silanized nano-alumina.

[0028] Preferably, the mass ratio of the nano-alumina, silane coupling agent KH550 and silane coupling agent KH560 is 1:(0.1~0.2):(0.1~0.2).

[0029] Preferably, the particle size of the nano-alumina is 10~50nm.

[0030] In this technical solution, the modified nano-alumina is added after neutralization to achieve chemical bonding between the nanoparticles and the resin matrix, so that the nanoparticles are chemically anchored and uniformly dispersed in the resin. This not only maintains the low viscosity characteristics of the resin in this application, but also significantly improves the mechanical properties and thermal stability of the subsequently cured product.

[0031] Secondly, this application provides a liquid bisphenol F type epoxy resin prepared by the above-described preparation method.

[0032] In this technical solution, bisphenol F with a specific isomer ratio is first obtained through a stepwise catalytic reaction; then, through a process of protection followed by slow release, the phenolic hydroxyl groups are controlled to participate in the reaction in a specific time sequence. The resulting liquid bisphenol F epoxy resin has the characteristics of moderate viscosity and low hydrolyzable chlorine content.

[0033] In summary, this application has the following beneficial effects: This application employs a bifunctional catalyst system to catalyze the stepwise condensation reaction of phenol and formaldehyde, regulating the isomer distribution of bisphenol F and laying the foundation for achieving a balance between low viscosity and high toughness in subsequent epoxy resin synthesis. Simultaneously, in the epoxy resin synthesis, trimethylchlorosilane is first used to protect the phenolic hydroxyl groups, followed by slow catalytic deprotection via fluoride, allowing the phenolic hydroxyl groups to be gradually released and participate in the ring-closing reaction, effectively suppressing local overheating and side reactions. The resulting liquid bisphenol F type epoxy resin possesses both moderate viscosity and high toughness. Attached Figure Description

[0034] Figure 1 This is the liquid phase spectrum of bisphenol F in Example 2 of this application; Figure 2 This is the liquid phase spectrum of bisphenol F in Example 3 of this application; Figure 3 The liquid phase spectrum of bisphenol F in Comparative Example 2 of this application; Figure 4 This is a gel permeation chromatogram of the liquid bisphenol F epoxy resin in Example 2 of this application; Figure 5This is a gel permeation chromatogram of the liquid bisphenol F epoxy resin in Example 3 of this application. Detailed Implementation

[0035] The present application will be further described in detail below with reference to the embodiments.

[0036] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0037] Preparation Examples 1-3: Hafnium Boron Supported on Silica Preparation Example 1 The preparation method of silicon dioxide-supported hafnium boron in this example includes the following steps: 200g of mesoporous silica and 1L of water were added to a reactor and placed in an ultrasonic dispersion device. After dispersion for 20 minutes at an ultrasonic power of 300W and a frequency of 40kHz, 16g of HfOCl2·8H2O was added, and the stirring device was turned on at a speed of 200r / min. The mixture was stirred and mixed evenly. The pH was adjusted to 8.5 with 8% ammonia water and stirred and soaked for 6 hours. The temperature was raised to 60℃ and aged for 2 hours. The mixture was then allowed to cool naturally to room temperature. The pH was adjusted to 7.5 with 5% glacial acetic acid, and 6g of H3BO3 was added. The temperature was raised to 40℃ and stirred and soaked for 3 hours. After centrifugation, the mixture was washed twice with 85% ethanol aqueous solution and dried at 60℃ for 3 hours. The mixture was then transferred to a heating device and heated to 500℃ at a heating rate of 3℃ / min. The mixture was calcined for 3 hours and allowed to cool naturally to room temperature. After physical dispersion, silica-supported hafnium boron was obtained.

[0038] Among them, mesoporous silica has a specific surface area of ​​300~500 m². 2 / g, with a particle size of 200nm~300nm.

[0039] Preparation Example 2 The preparation method of silicon dioxide-supported hafnium boron in this example includes the following steps: 200g of mesoporous silica and 1L of water were added to a reactor and placed in an ultrasonic dispersion device. After dispersion for 20 minutes at an ultrasonic power of 300W and a frequency of 40kHz, 20g of HfOCl2·8H2O was added, and the stirring device was turned on at a speed of 200r / min. The mixture was stirred until homogeneous. The pH was adjusted to 9.5 with 8% ammonia water and stirred for 12 hours. The temperature was raised to 80℃ and aged for 4 hours. The mixture was then allowed to cool naturally to room temperature. The pH was adjusted to 8.0 with 5% glacial acetic acid, and 10g of H3BO3 was added. The temperature was raised to 50℃ and stirred for 6 hours. After centrifugation, the mixture was washed twice with 85% ethanol aqueous solution and dried at 60℃ for 3 hours. The mixture was then transferred to a heating device and heated to 500℃ at a heating rate of 3℃ / min. The mixture was calcined for 3 hours and allowed to cool naturally to room temperature. After physical dispersion, silica-supported hafnium boron was obtained.

[0040] Among them, mesoporous silica has a specific surface area of ​​300~500 m². 2 / g, with a particle size of 200nm~300nm.

[0041] Preparation Example 3 The preparation method of silicon dioxide-supported hafnium boron in this example includes the following steps: 200g of mesoporous silica and 1L of water were added to a reactor and placed in an ultrasonic dispersion device. After dispersion for 20 minutes at an ultrasonic power of 300W and a frequency of 40kHz, 18g of HfOCl2·8H2O was added, and the stirring device was turned on at a speed of 200r / min. The mixture was stirred and mixed evenly. The pH was adjusted to 9.0 with 8% ammonia water and stirred and soaked for 10 hours. The temperature was raised to 75℃ and aged for 3 hours. The mixture was then allowed to cool naturally to room temperature. The pH was adjusted to 8.0 with 5% glacial acetic acid, and 8.5g of H3BO3 was added. The temperature was raised to 45℃ and stirred and soaked for 5 hours. After centrifugation, the mixture was washed twice with 85% ethanol aqueous solution and dried at 60℃ for 3 hours. The mixture was then transferred to a heating device and heated to 500℃ at a heating rate of 3℃ / min. The mixture was calcined for 3 hours and allowed to cool naturally to room temperature. After physical dispersion, silica-supported hafnium boron was obtained.

[0042] Among them, mesoporous silica has a specific surface area of ​​300~500 m². 2 / g, with a particle size of 200nm~300nm.

[0043] Preparation Examples 4-6: Hydroxyapatite-supported lanthanum zinc Preparation Example 4 The preparation method of hydroxyapatite-supported lanthanum zinc in this example includes the following steps: 200g of hydroxyapatite and 1L of water were added to a reactor and placed in an ultrasonic dispersion device. After dispersion for 20 minutes at an ultrasonic power of 300W and a frequency of 40kHz, 4g of lanthanum nitrate hexahydrate and 12g of zinc nitrate hexahydrate were added. The stirring device was turned on and the speed was 200r / min. The mixture was stirred and mixed evenly. The pH was adjusted to 8.0 with 8% ammonia water. The mixture was stirred and soaked for 6 hours, heated to 50℃, aged for 2 hours, centrifuged, rinsed twice with deionized water, dried at 60℃ for 4 hours, heated to 450℃ at a heating rate of 3℃ / min, calcined for 4 hours, and then naturally cooled to room temperature. After physical dispersion, La-Zn double-doped hydroxyapatite was obtained.

[0044] The hydroxyapatite has a particle size distribution of 200 nm to 500 nm and a specific surface area of ​​40 to 80 m². 2 / g.

[0045] Preparation Example 5 The preparation method of hydroxyapatite-supported lanthanum zinc in this example includes the following steps: 200g of hydroxyapatite and 1L of water were added to a reactor and placed in an ultrasonic dispersion device. After dispersion for 20 minutes at an ultrasonic power of 300W and a frequency of 40kHz, 8g of lanthanum nitrate hexahydrate and 16g of zinc nitrate hexahydrate were added. The stirring device was turned on and the speed was 200r / min. The mixture was stirred and mixed evenly. The pH was adjusted to 9.0 with 8% ammonia water. The mixture was stirred and soaked for 12 hours. The temperature was raised to 70℃ and aged for 4 hours. After centrifugation, the mixture was washed twice with deionized water and dried at 60℃ for 4 hours. The temperature was raised to 550℃ at a rate of 3℃ / min and calcined for 2 hours. The mixture was then naturally cooled to room temperature. After physical dispersion, La-Zn double-doped hydroxyapatite was obtained.

[0046] The hydroxyapatite has a particle size distribution of 200 nm to 500 nm and a specific surface area of ​​40 to 80 m². 2 / g.

[0047] Preparation Example 6 The preparation method of hydroxyapatite-supported lanthanum zinc in this example includes the following steps: 200g of hydroxyapatite and 1L of water were added to a reactor and placed in an ultrasonic dispersion device. After dispersion for 20 minutes at an ultrasonic power of 300W and a frequency of 40kHz, 6g of lanthanum nitrate hexahydrate and 15g of zinc nitrate hexahydrate were added. The stirring device was turned on and the speed was 200r / min. The mixture was stirred and mixed evenly. The pH was adjusted to 8.5 with 8% ammonia water. The mixture was stirred and soaked for 10 hours. The temperature was raised to 65℃ and aged for 3 hours. After centrifugation, the mixture was washed twice with deionized water and dried at 60℃ for 4 hours. The temperature was raised to 500℃ at a rate of 3℃ / min and calcined for 3 hours. After natural cooling to room temperature, La-Zn double-doped hydroxyapatite was obtained after physical dispersion.

[0048] The hydroxyapatite has a particle size distribution of 200 nm to 500 nm and a specific surface area of ​​40 to 80 m². 2 / g.

[0049] Example 1 The preparation method of liquid bisphenol F type epoxy resin in this embodiment includes the following steps: S1: Under a nitrogen atmosphere of low pressure (0.02 MPa), 3 mol of phenol, 0.5 g of silica-supported hafnium boron from Preparation Example 1, 0.3 g of oxalic acid, and 500 mL of methanol were added to a reactor. The temperature was raised to 60 °C, and 32.5 g of 37% formaldehyde aqueous solution (approximately 0.4 mol of formaldehyde) was added. The mixture was stirred at 150 rpm for 1 h. Then, 0.6 g of hydroxyapatite-supported lanthanum zinc from Preparation Example 4 and 49.0 g of 37% formaldehyde aqueous solution were added. The temperature was kept constant at 60 °C, and the mixture was stirred at 150 rpm for 2 h. After filtration, the mixture was neutralized to pH 7 with 5% ammonia water and distilled under reduced pressure to obtain bisphenol F. In S2, under a low-pressure (0.02 MPa) nitrogen atmosphere, bisphenol F obtained in S1 and 300 mL of toluene were added to the reactor. Stirring was started at 200 rpm until homogeneous. Then, 0.8 mol of triethylamine was added and mixed thoroughly. Next, 0.8 mol of trimethylchlorosilane was slowly added dropwise. After the addition was complete, the reaction was carried out at 25 °C for 90 min. Then, 5 mol of epichlorohydrin and 2 g of tetrabutylammonium bromide were added, and the temperature was raised to 60 °C. Finally, 0.08 mol of anhydrous potassium fluoride (dried at 150 °C for 2 h before use) was added in four equal portions. Add the solution to the reaction system at 15-minute intervals. After each addition, continue the reaction for 90 minutes. Add a 30% sodium hydroxide solution to adjust the pH to 10.5. Maintain a constant temperature of 60°C for 3 hours. Monitor the pH during the reaction and maintain it at 10.5. After the reaction, cool to room temperature, add 50 mL of deionized water, stir and wash, allow to stand and separate into layers. Take the organic phase, wash it with deionized water until neutral, dry it with anhydrous sodium sulfate, and remove toluene and unreacted epichlorohydrin by vacuum distillation to obtain liquid bisphenol F type epoxy resin.

[0050] Test results showed: epoxy equivalent 166 g / mol; rotational viscosity at 25°C 2253 mPa·s; inorganic chlorine content 1.2 ppm; hydrolyzed chlorine content 0.0134%. The prepared liquid bisphenol F epoxy resin and diethylenetriamine curing agent were mixed evenly according to a stoichiometric ratio (approximately 9 parts diethylenetriamine per 100 parts resin). The mixture was then coated onto a polytetrafluoroethylene mold, with a coating thickness controlled at 1.0 mm. The mixture was cured at 80°C for 2 hours, followed by curing at 100°C for 30 minutes to obtain a standard test sample. The tensile strength was measured to be 88.5 MPa, the elongation at break to be 7.2%, and the unnotched impact strength to be 13.6 kJ / m². 2 .

[0051] Example 2 The preparation method of liquid bisphenol F type epoxy resin in this embodiment includes the following steps: S1: Under a low-pressure (0.05 MPa) nitrogen atmosphere, 5 mol of phenol, 1 g of silica-supported hafnium boron from Preparation Example 2, 0.5 g of oxalic acid, and 500 mL of methanol were added to a reactor. The temperature was raised to 70°C, and 40.5 g of a 37% formaldehyde aqueous solution (approximately 0.5 mol of formaldehyde) was added. The mixture was stirred at 150 rpm for 2 h. Then, 1.2 g of hydroxyapatite-supported lanthanum zinc from Preparation Example 5 and 40.5 g of a 37% formaldehyde aqueous solution were added. The temperature was kept constant at 70°C, and the mixture was stirred at 150 rpm for 4 h. After filtration, the mixture was neutralized to pH 7 with 5% ammonia water and distilled under reduced pressure to obtain bisphenol F. S2: Under a low-pressure (0.05 MPa) nitrogen atmosphere, bisphenol F obtained in S1 and 300 mL of toluene were added to the reactor. Stirring was started at 200 rpm until homogeneous. 1.4 mol of triethylamine was added and mixed thoroughly. Then, 1.4 mol of trimethylchlorosilane was slowly added dropwise. After the addition was complete, the reaction was carried out at 30°C for 120 min. Then, 8 mol of epichlorohydrin and 4 g of tetrabutylammonium bromide were added. The temperature was raised to 60°C. 0.2 mol of anhydrous potassium fluoride (dried at 150°C for 2 h before use) was added in 8 equal portions. Add the solution to the reaction system at 15-minute intervals. After each addition, continue the reaction for 90 minutes. Add a 30% sodium hydroxide solution to adjust the pH to 11.0. Maintain a constant temperature of 60°C for 5 hours. Monitor the pH during the reaction and maintain it at 11.0. After the reaction, cool to room temperature, add 50 mL of deionized water, stir and wash, allow to stand and separate into layers. Take the organic phase, wash it with deionized water until neutral, dry it with anhydrous sodium sulfate, and remove toluene and unreacted epichlorohydrin by vacuum distillation to obtain liquid bisphenol F type epoxy resin.

[0052] Test results showed: epoxy equivalent of 164 g / mol; rotational viscosity at 25°C of 2178 mPa·s; inorganic chlorine content of 1.0 ppm; and hydrolyzed chlorine content of 0.0121%. The prepared liquid bisphenol F epoxy resin and diethylenetriamine curing agent were mixed evenly according to a stoichiometric ratio (approximately 9 parts diethylenetriamine per 100 parts resin). The mixture was then coated onto a polytetrafluoroethylene mold, with a coating thickness controlled at 1.0 mm. The mixture was cured at 80°C for 2 hours, followed by curing at 100°C for 30 minutes to obtain a standard test sample. The tensile strength was measured to be 89.2 MPa, the elongation at break to be 7.5%, and the unnotched impact strength to be 14.2 kJ / m². 2 .

[0053] Example 3 The preparation method of liquid bisphenol F type epoxy resin in this embodiment includes the following steps: S1: Under a nitrogen atmosphere of low pressure (0.05 MPa), 4 mol of phenol, 0.8 g of silica-supported hafnium boron from Preparation Example 3, 0.4 g of oxalic acid and 500 mL of methanol were added to the reactor. The temperature was raised to 65 °C, and 49.0 g of 37% formaldehyde aqueous solution (approximately 0.6 mol of formaldehyde) was added. The mixture was stirred at 150 rpm for 1.5 h. Then, 1.0 g of hydroxyapatite-supported lanthanum zinc from Preparation Example 6 and 32.5 g of 37% formaldehyde aqueous solution were added. The temperature was kept constant at 65 °C, and the mixture was stirred at 150 rpm for 3 h. After filtration, the mixture was neutralized to pH 7 with 5% ammonia water and distilled under reduced pressure to obtain bisphenol F. S2: Under a low-pressure (0.05 MPa) nitrogen atmosphere, bisphenol F obtained in S1 and 300 mL of toluene were added to the reactor. Stirring was started at 200 rpm until homogeneous. 1.1 mol of triethylamine was added and mixed thoroughly. Then, 1.1 mol of trimethylchlorosilane was slowly added dropwise. After the addition was complete, the reaction was carried out at 30 °C for 110 min. Then, 7 mol of epichlorohydrin and 3 g of tetrabutylammonium bromide were added. The temperature was raised to 60 °C. 0.15 mol of anhydrous potassium fluoride (dried at 150 °C for 2 h before use) was added in 6 equal portions. Add the solution to the reaction system at 15-minute intervals. After each addition, continue the reaction for 90 minutes. Add a 30% sodium hydroxide solution to adjust the pH to 11.0. Maintain a constant temperature of 60°C for 4 hours. Monitor the pH during the reaction and maintain it at 11.0. After the reaction, cool to room temperature, add 50 mL of deionized water, stir and wash, allow to stand and separate into layers. Take the organic phase, wash it with deionized water until neutral, dry it with anhydrous sodium sulfate, and remove toluene and unreacted epichlorohydrin by vacuum distillation to obtain liquid bisphenol F epoxy resin.

[0054] Test results showed: epoxy equivalent 167 g / mol; rotational viscosity at 25°C 2310 mPa·s; inorganic chlorine content 1.1 ppm; hydrolyzed chlorine content 0.0128%. The prepared liquid bisphenol F epoxy resin and diethylenetriamine curing agent were mixed evenly according to a stoichiometric ratio (approximately 9 parts diethylenetriamine per 100 parts resin). The mixture was then coated onto a polytetrafluoroethylene mold, with a coating thickness controlled at 1.0 mm. The mixture was cured at 80°C for 2 hours, followed by curing at 100°C for 30 minutes to obtain a standard test sample. The tensile strength was measured to be 88.8 MPa, the elongation at break to be 7.3%, and the unnotched impact strength to be 13.9 kJ / m². 2 .

[0055] Example 4 The preparation method of liquid bisphenol F type epoxy resin in this embodiment includes the following steps: S1: Under a nitrogen atmosphere of low pressure (0.05 MPa), 4 mol of phenol, 0.8 g of silica-supported hafnium boron from Preparation Example 2, 0.4 g of oxalic acid, and 500 mL of methanol were added to a reactor. The temperature was raised to 65°C, and 49.0 g of 37% formaldehyde aqueous solution (approximately 0.6 mol of formaldehyde) was added. The mixture was stirred at 150 rpm for 1.5 h. Then, 1.0 g of hydroxyapatite-supported lanthanum zinc from Preparation Example 5 and 32.5 g of 37% formaldehyde aqueous solution were added. The temperature was kept constant at 65°C, and the mixture was stirred at 150 rpm for 3 h. After filtration, the mixture was neutralized to pH 7 with 5% ammonia water and distilled under reduced pressure to obtain bisphenol F. S2: Under a low-pressure (0.05 MPa) nitrogen atmosphere, bisphenol F obtained in S1 and 300 mL of toluene were added to the reactor. The stirring was started at 200 rpm and the mixture was stirred until homogeneous. 1.1 mol of triethylamine was added and mixed thoroughly. Then, 1.1 mol of trimethylchlorosilane was slowly added dropwise. After the addition was complete, the reaction was carried out at 30 °C for 120 min. Then, 7 mol of epichlorohydrin and 3 g of tetrabutylammonium bromide were added. The temperature was raised to 60 °C. 0.15 mol of anhydrous potassium fluoride (dried at 150 °C for 2 h before use) was added to the reaction system in 6 equal portions, with each addition 15 min apart. After the addition was completed, the reaction continued for 90 min. A 30% sodium hydroxide solution was added dropwise to adjust the pH to 11.0. The reaction was maintained at 60℃ for 4 h. During the reaction, the pH was monitored with a pH meter and maintained at 11.0. After the reaction was completed, the mixture was cooled to room temperature, 50 mL of deionized water was added and stirred and washed. The mixture was allowed to stand and separate into layers. The organic phase was taken, and 3% of silanized nano-alumina was added. The mixture was heated to 50℃ and stirred and dispersed for 45 min. The mixture was washed with deionized water until neutral and dried with anhydrous sodium sulfate. Toluene and unreacted epichlorohydrin were removed by vacuum distillation to obtain liquid bisphenol F type epoxy resin.

[0056] The preparation method of silanized alumina includes the following steps: 20g of nano-alumina with a particle size of 10-50nm was added to 200g of 75% ethanol aqueous solution and placed in an ultrasonic dispersion device. After dispersion for 15min under ultrasonic power of 300W and frequency of 40kHz, 2g of silane coupling agent KH550 and 2g of silane coupling agent KH560 were added and stirred until uniform. The pH was adjusted to 4.0 with 5% glacial acetic acid, the temperature was raised to 50℃, and the reaction was stirred for 4h. After centrifugation, the nano-alumina was washed three times with anhydrous ethanol and dried at 60℃ to constant weight to obtain silanized nano-alumina.

[0057] Test results showed: epoxy equivalent 169 g / mol; rotational viscosity at 25°C 2467 mPa·s; inorganic chlorine content 0.9 ppm; hydrolyzed chlorine content 0.0115%. The prepared liquid bisphenol F epoxy resin and diethylenetriamine curing agent were mixed evenly according to a stoichiometric ratio (approximately 9 parts diethylenetriamine per 100 parts resin). The mixture was then coated onto a polytetrafluoroethylene mold, with a coating thickness controlled at 1.0 mm. The mixture was cured at 80°C for 2 hours, followed by curing at 100°C for 30 minutes to obtain a standard test sample. The tensile strength was measured to be 90.2 MPa, the elongation at break to be 8.3%, and the unnotched impact strength to be 15.1 kJ / m². 2 .

[0058] Example 5 The difference between this embodiment and embodiment 4 is that: S2: Under a low-pressure (0.05 MPa) nitrogen atmosphere, bisphenol F obtained in S1 and 300 mL of toluene were added to the reactor. The stirring was started at 200 rpm and the mixture was stirred until homogeneous. 1.1 mol of triethylamine was added and mixed thoroughly. Then, 1.1 mol of trimethylchlorosilane was slowly added dropwise. After the addition was complete, the reaction was carried out at 30 °C for 120 min. Then, 7 mol of epichlorohydrin and 3 g of tetrabutylammonium bromide were added. The temperature was raised to 60 °C. 0.15 mol of anhydrous potassium fluoride (dried at 150 °C for 2 h before use) was added to the reaction system in 6 equal portions, with each addition 15 min apart. After the addition was completed, the reaction continued for 90 min. A 30% sodium hydroxide solution was added dropwise to adjust the pH to 11.0. The reaction was maintained at 60℃ for 4 h. During the reaction, the pH was monitored with a pH meter and maintained at 11.0. After the reaction was completed, the mixture was cooled to room temperature, 50 mL of deionized water was added and stirred and washed. The mixture was allowed to stand and separate into layers. The organic phase was taken, and 5% of silanized nano-alumina was added. The mixture was heated to 55℃ and stirred and dispersed for 60 min. The mixture was washed with deionized water until neutral and dried with anhydrous sodium sulfate. Toluene and unreacted epichlorohydrin were removed by vacuum distillation to obtain liquid bisphenol F type epoxy resin.

[0059] The preparation method of silanized alumina includes the following steps: 20g of nano-alumina with a particle size of 10-50nm was added to 200g of 75% ethanol aqueous solution and placed in an ultrasonic dispersion device. After dispersion for 15min under ultrasonic power of 300W and frequency of 40kHz, 4g of silane coupling agent KH550 and 4g of silane coupling agent KH560 were added and stirred until uniform. The pH was adjusted to 5.0 with 5% glacial acetic acid, the temperature was raised to 60℃, and the reaction was stirred for 3h. After centrifugation, the nano-alumina was washed three times with anhydrous ethanol and dried at 60℃ to constant weight to obtain silanized nano-alumina.

[0060] The rest is the same as in Example 4.

[0061] Test results showed: epoxy equivalent 172 g / mol; rotational viscosity at 25°C 2791 mPa·s; inorganic chlorine content 0.8 ppm; hydrolyzed chlorine content 0.0107%. The prepared liquid bisphenol F epoxy resin and diethylenetriamine curing agent were mixed evenly according to a stoichiometric ratio (approximately 9 parts diethylenetriamine per 100 parts resin). The mixture was then coated onto a polytetrafluoroethylene mold, with a coating thickness controlled at 1.0 mm. The mixture was cured at 80°C for 2 hours, followed by curing at 100°C for 30 minutes to obtain a standard test sample. The tensile strength was measured to be 90.8 MPa, the elongation at break to be 8.7%, and the unnotched impact strength to be 15.8 kJ / m². 2 .

[0062] Comparative Example 1 The difference between this comparative example and Example 1 is as follows: S2: Under a low-pressure (0.02 MPa) nitrogen atmosphere, bisphenol F obtained in S1 and 300 mL of toluene were added to the reactor. Stirring was started at 200 rpm. 5 mol of epichlorohydrin and 2 g of tetrabutylammonium bromide were added. The temperature was raised to 60 °C and the reaction was carried out for 135 min. A 30% sodium hydroxide solution was added dropwise to adjust the pH to 10.5. The reaction was maintained at 60 °C for 3 h. During the reaction, the pH was monitored by a pH meter and maintained at 10.5. After the reaction was completed, the mixture was cooled to room temperature. 50 mL of deionized water was added and the mixture was stirred and washed. The mixture was allowed to stand and separate into layers. The organic phase was taken and washed with deionized water until neutral. It was then dried with anhydrous sodium sulfate. Toluene and unreacted epichlorohydrin were removed by vacuum distillation to obtain liquid bisphenol F epoxy resin.

[0063] Everything else is the same as in Example 1.

[0064] Test results showed: epoxy equivalent of 182 g / mol; rotational viscosity at 25°C of 3863 mPa·s; inorganic chlorine content of 8.7 ppm; and hydrolyzed chlorine content of 0.1162%. The prepared liquid bisphenol F epoxy resin and diethylenetriamine curing agent were mixed evenly according to a stoichiometric ratio (approximately 9 parts diethylenetriamine per 100 parts resin). The mixture was then coated onto a polytetrafluoroethylene mold, with a coating thickness controlled at 1.0 mm. The mixture was cured at 80°C for 2 hours, followed by curing at 100°C for 30 minutes to obtain a standard test sample. The tensile strength was measured to be 80.2 MPa, the elongation at break was 5.1%, and the unnotched impact strength was 10.3 kJ / m². 2 .

[0065] Comparative Example 2 The difference between this comparative example and Example 1 is as follows: S1: Under a low-pressure (0.02 MPa) nitrogen atmosphere, 3 mol of phenol, 0.5 g of silica-supported hafnium boron from Preparation Example 1, 0.3 g of oxalic acid, and 500 mL of methanol were added to a reactor. The temperature was raised to 60 °C, and 32.5 g of a 37% formaldehyde aqueous solution (approximately 0.4 mol of formaldehyde) was added. The mixture was stirred at 150 rpm for 1 h. Then, 0.6 g of oxalic acid and 49.0 g of a 37% formaldehyde aqueous solution were added. The temperature was kept constant at 60 °C, and the mixture was stirred at 150 rpm for 2 h. After filtration, the mixture was neutralized to pH 7 with 5% ammonia water and distilled under reduced pressure to obtain bisphenol F. Everything else is the same as in Example 1.

[0066] Test results showed: epoxy equivalent 176 g / mol; rotational viscosity at 25°C 3151 mPa·s; inorganic chlorine content 7.2 ppm; hydrolyzed chlorine content 0.0592%. The prepared liquid bisphenol F epoxy resin and diethylenetriamine curing agent were mixed evenly according to a stoichiometric ratio (approximately 9 parts diethylenetriamine per 100 parts resin). The mixture was then coated onto a polytetrafluoroethylene mold, with a coating thickness controlled at 1.0 mm. The mixture was cured at 80°C for 2 hours, followed by curing at 100°C for 30 minutes to obtain a standard test sample. The tensile strength was measured to be 83.5 MPa, the elongation at break to be 5.8%, and the unnotched impact strength to be 11.5 kJ / m². 2 .

[0067] Comparative Example 3 The difference between this comparative example and Example 1 is as follows: S1: Under a low-pressure (0.02 MPa) nitrogen atmosphere, 3 mol of phenol, 0.8 g of oxalic acid, and 500 mL of methanol were added to a reactor. The temperature was raised to 60°C, and 32.5 g of a 37% formaldehyde aqueous solution (approximately 0.4 mol of formaldehyde) was added. The mixture was stirred at 150 rpm for 1 hour. Then, 0.6 g of oxalic acid and 49.0 g of a 37% formaldehyde aqueous solution were added. The temperature was kept constant at 60°C, and the mixture was stirred at 150 rpm for 2 hours. After filtration, the mixture was neutralized to pH 7 with 5% ammonia water and distilled under reduced pressure to obtain bisphenol F. Everything else is the same as in Example 1.

[0068] Test results showed: epoxy equivalent of 175 g / mol; rotational viscosity at 25°C of 3549 mPa·s; inorganic chlorine content of 7.8 ppm; and hydrolyzed chlorine content of 0.0617%. The prepared liquid bisphenol F epoxy resin and diethylenetriamine curing agent were mixed evenly according to a stoichiometric ratio (approximately 9 parts diethylenetriamine per 100 parts resin). The mixture was then coated onto a polytetrafluoroethylene mold, with a coating thickness controlled at 1.0 mm. The mixture was cured at 80°C for 2 hours, followed by curing at 100°C for 30 minutes to obtain a standard test sample. The tensile strength was measured to be 81.3 MPa, the elongation at break was 5.5%, and the unnotched impact strength was 12.1 kJ / m². 2 .

[0069] Combination Figures 1-5 The detection data analysis of Examples 1-5 and Comparative Examples 1-3 is as follows: In Examples 1-3 of this application, the distribution of bisphenol F isomers was precisely controlled by a stepwise dual-catalyst system, and an epoxidation process of phenolic hydroxyl protection-slow-release deprotection was adopted. The prepared liquid bisphenol F type epoxy resin has the characteristics of moderate epoxy equivalent, low viscosity, and extremely low chlorine content.

[0070] Examples 4-5 further introduce silanized nano-alumina modification based on the above. While maintaining low viscosity and extremely low chlorine content, the tensile strength, elongation at break and impact resistance after curing are slightly improved through the chemical bonding and interfacial reinforcement between nanoparticles and resin matrix. At the same time, the residual chlorine content is further reduced, and the long-term reliability of the resin is optimized.

[0071] In Comparative Example 1, no phenolic hydroxyl preprotection or deprotection was used. During the reaction, a large number of phenolic hydroxyl groups were exposed instantaneously, resulting in violent local reactions and an increase in epichlorohydrin hydrolysis side reactions. As a result, the viscosity of the obtained resin increased significantly and the chlorine content increased dramatically. Comparative Example 2 only used silica-supported hafnium boron and oxalic acid as a catalyst and did not add hydroxyapatite-supported lanthanum zinc catalyst. Comparative Example 3 used oxalic acid as a single catalyst. Neither of these methods could effectively control the distribution of bisphenol F isomers. The isomer ratio was unbalanced and the polymer byproducts increased, which directly led to higher viscosity and excessive chlorine content in the obtained resin, and the mechanical properties were inferior to those of the embodiments in this application.

[0072] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing liquid bisphenol F type epoxy resin, characterized in that, Includes the following steps: S1: Under an inert atmosphere, phenol, catalyst A and methanol are added to the reactor, the temperature is raised to 60~70℃, some formaldehyde is added, the reaction is carried out for 1~2 hours, then catalyst B and the remaining formaldehyde are added, the reaction is carried out for 2~4 hours, solid-liquid separation is performed, neutralization is carried out, and purification is carried out to obtain bisphenol F. S2: Under an inert atmosphere, bisphenol F and toluene are mixed evenly, and an acid-binding agent and trimethylchlorosilane are added. After reacting at 25-30°C for 90-120 min, epichlorohydrin and a phase transfer catalyst are added, and the temperature is raised to 60-70°C. Fluoride is added in portions over a period of not less than 45 min, and the reaction continues for 90-120 min. The pH is dynamically adjusted to 10.5-11.0, and the reaction is carried out for 3-5 h. The mixture is washed, separated into layers, and purified to obtain liquid bisphenol F type epoxy resin. Catalyst A comprises silica-supported hafnium boron and oxalic acid; catalyst B is hydroxyapatite-supported lanthanum zinc; the phase transfer catalyst is a quaternary ammonium salt.

2. The method for preparing liquid bisphenol F type epoxy resin according to claim 1, characterized in that, The molar ratio of phenol, formaldehyde, acid-binding agent, trimethylchlorosilane, epichlorohydrin and fluoride is (3~5):1:(0.8~1.4):(0.8~1.4):(5~8):(0.08~0.2).

3. The method for preparing liquid bisphenol F type epoxy resin according to claim 1, characterized in that, In step S1, the formaldehyde portion accounts for 40% to 60% of the total formaldehyde usage.

4. The method for preparing liquid bisphenol F type epoxy resin according to claim 1, characterized in that, The method for preparing silicon dioxide-supported hafnium boron includes the following steps: Mesoporous silica was dispersed in water, a hafnium source was added and mixed evenly, the pH was adjusted to 8.5-9.5, and the mixture was soaked for 6-12 hours. The temperature was raised to 60-80℃ and aged for 2-4 hours. After cooling, the pH was adjusted to 7.5-8.0, a boron source was added and mixed evenly, the temperature was raised to 40-50℃ and the mixture was soaked for 3-6 hours. Solid-liquid separation was performed, followed by washing, drying, calcination at 500-550℃ for 2-3 hours, and cooling to obtain silica-supported hafnium boron.

5. The method for preparing liquid bisphenol F type epoxy resin according to claim 4, characterized in that, The mass ratio of the mesoporous silica, hafnium source and boron source is 100:(8~10):(3~5).

6. The method for preparing liquid bisphenol F type epoxy resin according to claim 1, characterized in that, The preparation method of the La-Zn dual-doped hydroxyapatite includes the following steps: Hydroxyapatite was dispersed in water, and lanthanum and zinc sources were added to adjust the pH to 8-9. The mixture was soaked for 6-12 hours, heated to 50-70℃, aged for 2-4 hours, separated from solids, washed, dried, calcined at 450-550℃ for 2-4 hours, and cooled to obtain La-Zn double-doped hydroxyapatite.

7. The method for preparing liquid bisphenol F type epoxy resin according to claim 6, characterized in that, The mass ratio of the hydroxyapatite, lanthanum source and zinc source is 100:(2~4):(6~8).

8. The method for preparing liquid bisphenol F type epoxy resin according to claim 1, characterized in that, In step S2, after neutralization, the following steps are also included: after separation, take the organic phase, add 3% to 5% of silanized nano-alumina by mass of the organic phase, heat to 50 to 55°C, react for 45 to 60 minutes, separate into layers, purify, and obtain liquid bisphenol F type epoxy resin.

9. The method for preparing liquid bisphenol F type epoxy resin according to claim 8, characterized in that, The method for preparing the silanized nano-alumina includes the following steps: Nano-alumina was uniformly dispersed in an ethanol aqueous solution, and silane coupling agents KH550 and KH560 were added and mixed evenly. The pH was adjusted to 4.0-5.0, the temperature was raised to 50-60℃, and the reaction was carried out for 3-4 hours. The solid and liquid were separated, washed, and dried to obtain silanized nano-alumina.

10. A liquid bisphenol F type epoxy resin prepared by the preparation method according to any one of claims 1 to 9.

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