A furan resin material and a method for producing the same

Abstract

The application discloses a furan resin material and a preparation method thereof. The material is composed of the following components in parts by weight: furfuryl alcohol 75-85 parts, formaldehyde 10-20 parts, urea 5-15 parts, a double-furan end group amide monomer F-ED 15-25 parts, p-toluene sulfonic acid 3-5 parts, and water 2-4 parts. The preparation steps of the F-ED monomer include: taking N-(4-aminophenyl) ethylenediamine as a starting raw material, protecting by t-butoxy carbonyl, amidating with furan formyl chloride, deprotecting, and purifying by column chromatography to obtain the F-ED monomer. In the preparation, the furfuryl alcohol, the formaldehyde and the urea are pre-polycondensated under an alkaline condition, then the F-ED monomer and the p-toluene sulfonic acid are added, and after mixing and defoaming, the resin material is obtained through stepwise temperature rising and solidification. By introducing the double-furan end group amide monomer, the crosslinking density and the mechanical properties of the furan resin are improved, the preparation process is simple, and the furan resin material is suitable for the fields of casting and adhesive and the like.

Description

Technical Field

[0001] This invention relates to the field of resin materials, and more specifically to a furan resin material and its preparation method. Background Technology

[0002] Furan resins are thermosetting resins made primarily from furfuryl alcohol or furfural. They possess excellent acid and alkali resistance, heat resistance, and electrical insulation properties, and are widely used in the foundry industry, anti-corrosion coatings, and composite materials. However, traditional furran resins exhibit high crosslinking density and rigid molecular chains after curing, resulting in significant brittleness and poor impact resistance, severely limiting their application in high-end structural materials. Furthermore, furran resins experience substantial volume shrinkage during curing, easily generating internal stress and microcracks, affecting the dimensional stability and long-term mechanical reliability of the finished products. Self-hardening furan resin sand casting technology has been under development since the 1970s. By 2014, China's annual consumption of self-hardening furan resin had reached 368,000 tons, producing approximately 9 million tons of castings annually. It is widely used in the production of medium and large castings in industries such as machine tools, construction machinery, power, shipbuilding, and rail transportation. The dimensional accuracy of these castings can reach CT8–CT10, with surface roughness ranging from Ra12.5 to 50 μm, and the scrap rate can be stably controlled below 5%. Studies have shown that furan resins, under acid catalysis, transform from a two-dimensional linear structure to a three-dimensional network structure through condensation and addition polymerization, binding sand particles to form a rigid framework. The curing process is influenced by multiple factors, including the content of furfuryl alcohol and urea-formaldehyde in the resin, the type and amount of curing agent, and ambient temperature and humidity. Higher urea-formaldehyde content results in stronger reactivity, while higher furfuryl alcohol content requires stronger acidic conditions to achieve the necessary curing speed and strength. However, traditional furan resins exhibit high crosslinking density and rigid molecular chains after curing, leading to significant brittleness, poor impact resistance, and substantial volume shrinkage during curing, which easily generates internal stress and microcracks, limiting their application in high-end structural materials. Existing modification technologies often employ physical blending with rubber elastomers, thermoplastic resins, or inorganic nanoparticles, but these suffer from problems such as uneven filler dispersion, weak interfacial bonding, and easy agglomeration and sedimentation. Furthermore, the lack of strong chemical bonds between the modifier and the resin matrix leads to interface debonding during long-term use, resulting in performance degradation. Therefore, there is an urgent need to develop chemical modification methods that can achieve reinforcement and toughening at the molecular level.

[0003] To improve the toughness of furan resins, existing technologies often employ physical blending to introduce rubber elastomers, thermoplastic resins, or inorganic nanoparticles. However, physical blending suffers from problems such as uneven filler dispersion, weak interfacial bonding with the matrix, and easy agglomeration and sedimentation, resulting in limited toughening effects and often at the expense of the resin's heat resistance and modulus. Furthermore, commercially available coupling agents or unfunctionalized fillers lack strong chemical bonds with the resin matrix, leading to interface debonding and performance degradation during long-term use. Another approach involves designing reactive toughening monomers at the molecular level and copolymerizing them into the crosslinking network of the furan resin. This improves toughness while maintaining the resin's intrinsic heat resistance, avoiding the phase separation problems associated with physical blending. However, the synthesis of amide monomers with dual furan end groups is currently cumbersome, difficult to purify, and prone to side reactions, limiting their application in furan resin modification. Summary of the Invention

[0004] The technical problem to be solved: The purpose of this invention is to develop a type of bisfuran-terminated amide monomer (F-ED) and introduce it as a copolymer component into a furfuryl alcohol-formaldehyde-urea polycondensation system. Under acid catalysis, it forms a covalent cross-linked network with the resin matrix, thereby simultaneously achieving toughening and reducing shrinkage at the molecular scale, overcoming the defects of traditional physical blending modification. The invention also aims to synthesize a simple bisfuran-terminated amide monomer that can form a covalent cross-linked network with a furan resin matrix and use it to prepare furan resin materials with both good mechanical properties and low shrinkage.

[0005] Technical solution: A furan resin material, composed of the following parts by weight: 75-85 parts furfuryl alcohol, 10-20 parts formaldehyde, 5-15 parts urea, 15-25 parts bisfuran-terminated amide monomer F-ED, 3-5 parts p-toluenesulfonic acid, and 2-4 parts water.

[0006] Preferably, the amide monomer F-ED with bisfuran end groups comprises the following preparation steps: S1-1. N-(4-aminophenyl)ethylenediamine was dissolved in anhydrous dichloromethane, and 4-dimethylaminopyridine and ditert-butyl dicarbonate were added. The mixture was stirred at room temperature under nitrogen protection. The reaction solution was washed successively with sodium bicarbonate solution and saturated brine. The solution was dried over anhydrous sodium sulfate and rotary evaporated to obtain the Boc protected intermediate.

[0007] S1-2. Dissolve the Boc protecting intermediate in anhydrous dichloromethane, add triethylamine, cool in an ice-salt bath, and slowly add a dichloromethane solution of furanoyl chloride. React at low temperature. After the reaction is complete, filter to remove triethylamine hydrochloride. Wash the reaction solution with sodium bicarbonate solution and saturated brine in sequence. Dry with anhydrous sodium sulfate and rotary evaporate to obtain the Boc protecting product. S1-3. The protected product of bisamide Boc was dissolved in dichloromethane, cooled in an ice bath under nitrogen protection, and trifluoroacetic acid was slowly added. The reaction was stirred at room temperature. The reaction solution was slowly poured into ice water to quench the reaction, extracted with dichloromethane, and the organic phase was washed successively with saturated sodium bicarbonate solution and saturated brine. After drying, the crude product was obtained by rotary evaporation. S1-4. The crude product from step S1-3 was purified by column chromatography using petroleum ether-ethyl acetate as the eluent. The target component was collected and evaporated to dryness to obtain the F-ED monomer.

[0008] Preferably, in step S1-1, the molar ratio of N-(4-aminophenyl)ethylenediamine, ditert-butyl dicarbonate and 4-dimethylaminopyridine is 1:(1.1-1.3):(0.05-0.1), the reaction temperature is 20-30℃, and the reaction time is 4-12h. Preferably, in steps S1-2, the molar ratio of the Boc protected intermediate, triethylamine, and furanoyl chloride is 1:(2.0-2.5):(2.0-2.2), the reaction temperature is -10 to 0°C, and the reaction time is 1-4 h.

[0009] Preferably, in steps S1-3, the molar ratio of the bisamide Boc protected product to trifluoroacetic acid is 1:(10-20), the reaction temperature is 0-30℃, and the reaction time is 2-3h.

[0010] Preferably, the eluent used in the column chromatography purification in steps S1-4 is petroleum ether to ethyl acetate in a volume ratio of 1:2, with the addition of 0.1-0.5% triethylamine.

[0011] Preferably, the preparation method of the above-mentioned furan resin material includes the following preparation steps: S1. Mix furfuryl alcohol, formaldehyde, and urea, add an alkaline catalyst to adjust the pH to 8-10, and stir the reaction at 60-80℃ for 1-2 hours to obtain the prepolymer. S2. Add the bisfuran-terminated amide monomer F-ED to the prepolymer, stir until homogeneous, then add p-toluenesulfonic acid and water, stir until homogeneous, and degas under vacuum for 10-15 minutes. S3. Inject the degassed mixture into a mold and cure it using a stepped heating process: first, keep it at 60℃ for 1-2 hours, then at 80℃ for 2 hours, and finally at 100℃ for 4-6 hours to obtain furan resin material.

[0012] Preferably, the alkaline catalyst is sodium hydroxide, potassium hydroxide, or ammonia.

[0013] Synthetic route of the bisfuran-terminated amide monomer F-ED:

[0014] Beneficial effects: The furan resin of the present invention has the following advantages: 1. This invention designs and synthesizes a double furan-terminated amide monomer, F-ED, whose molecular structure contains flexible amide segments and two reactive furan end groups. During acid-catalyzed curing, the furan groups at both ends of F-ED can undergo a polycondensation reaction with the hydroxymethyl group of furfuryl alcohol, embedding themselves covalently into the crosslinking network of the furan resin. The flexible amide segments act as internal toughening agents in the crosslinking network, effectively absorbing impact energy and alleviating stress concentration, thereby improving the impact toughness and crack resistance of the resin and overcoming the defects of phase separation and decreased heat resistance caused by traditional physical blending toughening. 2. The F-ED monomer introduced in this invention has a long molecular chain segment, which can adjust the topology of the crosslinking network during the curing process and reduce the total crosslinking shrinkage rate of the system; at the same time, hydrogen bonding can be formed between amide groups, which helps the orderly stacking of molecular chains, reduces the generation of microcracks, and improves the dimensional stability and mechanical reliability of the product. 3. The F-ED monomer introduced in this invention is covalently bonded to the resin network, forming a homogeneous structure with the matrix. This eliminates the problems of weak interfacial bonding between fillers and the matrix, and easy debonding during long-term use, common in traditional physical blending. All components participate in the chemical reaction, resulting in excellent overall material integrity and long-lasting stable mechanical properties. 4. The F-ED monomer preparation method provided by this invention uses N-(4-aminophenyl)ethylenediamine as the starting material, and proceeds through tert-butoxycarbonyl protection, furanyl chloride amidation, deprotection, and column chromatography purification. The conditions of each step are mild, the operation is simple, and the target product has high yield and good purity, making it suitable for large-scale preparation.

[0015] 5. This invention employs a furfuryl alcohol-formaldehyde-urea prepolymerization process, which is compatible with existing furan resin production equipment; the F-ED monomer can be added directly after prepolymerization without altering the original process flow, making it easy to promote and apply. Curing utilizes a stepped temperature ramping program, providing a wide process window and facilitating control. Attached Figure Description

[0016] Figure 1 Infrared spectra of Example 4 and Comparative Example 8; Detailed Implementation

[0017] The present invention will be further described below with reference to embodiments. These embodiments are illustrative of the present invention, but the present invention is not limited to these embodiments: Example 1

[0018] The preparation steps of the amide monomer F-ED with bisfuran end groups are as follows: S1-1. In a dry three-necked flask, add 3.34 g of N-(4-aminophenyl)ethylenediamine and 80 ml of anhydrous dichloromethane, and stir magnetically to dissolve. Add 0.24 g of 4-dimethylaminopyridine (DMAP), purge with nitrogen three times, and then add 4.80 g of di-tert-butyl dicarbonate. Stir the reaction under nitrogen protection at room temperature for 12 h. Monitor the reaction by TLC, with petroleum ether to ethyl acetate as the developing solvent at a ratio of 1:1. Stop the reaction when the starting material spot completely disappears. After the reaction is complete, transfer the reaction solution to a separatory funnel, wash once with 50 ml of saturated sodium bicarbonate solution, and then wash once with 50 ml of saturated brine. Separate the organic phase, dry with anhydrous sodium sulfate for 2 h, filter to remove the drying agent, and evaporate the filtrate under reduced pressure below 35 °C to remove the solvent, yielding a pale yellow oily liquid, which is the Boc-protected intermediate. S1-2. Dissolve 20 mmol of the Boc protecting intermediate obtained in the previous step in 100 ml of anhydrous dichloromethane, add 5.06 g of triethylamine, stir magnetically to dissolve, and place the reaction flask in an ice-salt bath to cool. A 3:1 mixture of ice and sodium chloride can lower the temperature to -10 °C. Dissolve 5.76 g of furanoyl chloride in 20 ml of anhydrous dichloromethane and place it in a constant-pressure dropping funnel; add it slowly dropwise at a rate of 1 ml / 15 min, for a total addition time of approximately 1 hour. During the dropwise addition, the temperature of the reaction solution was strictly controlled not to exceed 0℃. After the dropwise addition was completed, the mixture was stirred at -10℃ for 1 hour, and then raised to 0℃ and stirred for 3 hours. Nitrogen protection was maintained throughout the process. After the reaction was completed, the reaction solution was filtered with diatomaceous earth to remove the white precipitate of triethylamine hydrochloride. The filter cake was washed twice with 20 ml of dichloromethane. The filtrates were combined and washed once with 50 ml of saturated sodium bicarbonate solution, and then twice with 50 ml of saturated saline solution. The organic phase was separated, dried with anhydrous sodium sulfate for 2 hours, and the filtrate was evaporated under reduced pressure below 35℃ to remove the solvent, yielding a pale yellow viscous liquid, which is the protected product of diamide Boc. S1-3. Dissolve the 20 mmol of the protected product of bisamide Boc obtained in the previous step in 40 ml of dichloromethane and cool it to 0°C in an ice-water bath. Prepare 40 ml of trifluoroacetic acid and slowly add it to the reaction solution in 5-6 portions, with an interval of about 10 min between each addition. During the addition process, a large amount of heat is released and accompanied by vigorous bubble generation. Carefully control the addition rate to prevent splashing. After the trifluoroacetic acid is added, remove the ice bath and stir the reaction at room temperature for 3 h. After the reaction is completed, remove the trifluoroacetic acid and dichloromethane by rotary evaporation under reduced pressure below 35°C. Redissolve the residue in 50 ml of dichloromethane. Cool the solution in an ice-water bath and slowly add saturated sodium bicarbonate solution to neutralize the pH to 7-8. A large amount of carbon dioxide bubbles are generated during the neutralization process. Carefully control the addition rate to prevent liquid overflow. Separate the liquid and wash the organic phase twice with 30 ml of saturated brine. Separate the organic phase and dry it with anhydrous sodium sulfate for 2 h; filter, and remove the solvent from the filtrate by rotary evaporation under reduced pressure below 35°C to obtain the crude product.

[0019] S1-4. Column chromatography purification: Take 200g of silica gel and dry pack the column; dissolve the crude product in a small amount of dichloromethane, add silica gel and mix, dry under reduced pressure and then load the sample. Use a mixture of petroleum ether and ethyl acetate as the eluent, elute in a 1:1 ratio, combine the eluents, and remove the solvent by rotary evaporation under reduced pressure below 35℃ to obtain a pale yellow to light brown viscous liquid or a low-melting-point solid, which is the target product, the bisfuran-terminated amide monomer F-ED.

[0020] Example 2

[0021] The preparation steps of the amide monomer F-ED with bisfuran end groups are as follows: S1-1. In a dry three-necked flask, add 3.34 g of N-(4-aminophenyl)ethylenediamine and 80 ml of anhydrous dichloromethane, and stir magnetically to dissolve. Add 0.12 g of 4-dimethylaminopyridine (DMAP), purge with nitrogen three times, and then add 4.80 g of di-tert-butyl dicarbonate. Stir the reaction under nitrogen protection at room temperature for 8 h. Monitor the reaction by TLC, with petroleum ether to ethyl acetate as the developing solvent at a ratio of 1:1. Stop the reaction when the starting material spot completely disappears. After the reaction is complete, transfer the reaction solution to a separatory funnel, wash once with 50 ml of saturated sodium bicarbonate solution, and then wash once with 50 ml of saturated brine. Separate the organic phase, dry with anhydrous sodium sulfate for 2 h, filter to remove the drying agent, and evaporate the filtrate under reduced pressure below 35 °C to remove the solvent, yielding a pale yellow oily liquid, which is the Boc-protected intermediate. S1-2. Dissolve 20 mmol of the Boc protecting intermediate obtained in the previous step in 100 ml of anhydrous dichloromethane, add 4.05 g of triethylamine, stir magnetically to dissolve, and place the reaction flask in an ice-salt bath to cool. A 3:1 mixture of ice and sodium chloride can lower the temperature to -10 °C. Dissolve 5.22 g of furanoyl chloride in 20 ml of anhydrous dichloromethane and place it in a constant-pressure dropping funnel; add it slowly dropwise at a rate of 1 ml / 15 min, for a total addition time of approximately 1 hour. During the dropwise addition, the temperature of the reaction solution was strictly controlled not to exceed 0℃. After the dropwise addition was completed, the mixture was stirred at -10℃ for 0.5h, and then raised to 0℃ and stirred for 3h. Nitrogen protection was maintained throughout the process. After the reaction was completed, the reaction solution was filtered with diatomaceous earth to remove the white precipitate of triethylamine hydrochloride. The filter cake was washed twice with 20ml of dichloromethane. The filtrates were combined and washed once with 50ml of saturated sodium bicarbonate solution, and then twice with 50ml of saturated saline solution. The organic phase was separated, dried with anhydrous sodium sulfate for 2h, and the filtrate was evaporated under reduced pressure below 35℃ to remove the solvent, yielding a pale yellow viscous liquid, which is the protected product of diamide Boc. S1-3. Dissolve the 20 mmol of the protected product of bisamide Boc obtained in the previous step in 40 ml of dichloromethane and cool it to 0°C in an ice-water bath. Prepare 23 ml of trifluoroacetic acid and slowly add it to the reaction solution in 5-6 portions, with an interval of about 10 min between each addition. During the addition process, a large amount of heat is released and accompanied by vigorous bubble generation. Carefully control the addition rate to prevent splashing. After the trifluoroacetic acid is added, remove the ice bath and stir the reaction at room temperature for 3 h. After the reaction is completed, remove the trifluoroacetic acid and dichloromethane by rotary evaporation under reduced pressure below 35°C. Redissolve the residue in 50 ml of dichloromethane. Cool the solution in an ice-water bath and slowly add saturated sodium bicarbonate solution to neutralize the pH to 7-8. A large amount of carbon dioxide bubbles are generated during the neutralization process. Carefully control the addition rate to prevent liquid overflow. Separate the liquid and wash the organic phase twice with 30 ml of saturated brine. Separate the organic phase and dry it with anhydrous sodium sulfate for 2 h; filter, and remove the solvent from the filtrate by rotary evaporation under reduced pressure below 35°C to obtain the crude product.

[0022] S1-4. Column chromatography purification: Take 200g of silica gel and dry pack the column; dissolve the crude product in a small amount of dichloromethane, add silica gel and mix, dry under reduced pressure and then load the sample. Use a mixture of petroleum ether and ethyl acetate as the eluent, elute in a 1:1 ratio, combine the eluents, and remove the solvent by rotary evaporation under reduced pressure below 35℃ to obtain a pale yellow to light brown viscous liquid or a low-melting-point solid, which is the target product, the bisfuran-terminated amide monomer F-ED.

[0023] Comparative Example 1 The preparation steps of the amide monomer F-ED with bisfuran end groups are as follows: S1-1. In a dry three-necked flask, add 3.34 g of N-(4-aminophenyl)ethylenediamine and 80 ml of anhydrous dichloromethane, and stir magnetically to dissolve. Add 0.6 g of 4-dimethylaminopyridine (DMAP), purge with nitrogen three times, and then add 3.92 g of di-tert-butyl dicarbonate. Stir the reaction under nitrogen protection at room temperature for 18 h. Monitor the reaction by TLC, with petroleum ether to ethyl acetate as the developing solvent at a ratio of 1:1. Stop the reaction when the starting material spot completely disappears. After the reaction, transfer the reaction solution to a separatory funnel, wash once with 50 ml of saturated sodium bicarbonate solution, and then wash once with 50 ml of saturated brine. Separate the organic phase, dry with anhydrous sodium sulfate for 2 h, filter to remove the drying agent, and evaporate the filtrate under reduced pressure below 35 °C to remove the solvent, yielding a pale yellow oily liquid, which is the Boc-protected intermediate. S1-2. Dissolve 20 mmol of the Boc protecting intermediate obtained in the previous step in 100 ml of anhydrous dichloromethane, add 2.02 g of triethylamine, stir magnetically to dissolve, and place the reaction flask in an ice-salt bath to cool. A 3:1 mixture of ice and sodium chloride can lower the temperature to -10°C. Dissolve 6.53 g of furanoyl chloride in 20 ml of anhydrous dichloromethane and place it in a constant-pressure dropping funnel; add it slowly dropwise at a rate of 1 ml / 15 min, for a total addition time of approximately 1 hour. During the dropwise addition, the temperature of the reaction solution was strictly controlled not to exceed 0℃. After the dropwise addition was completed, the mixture was stirred at 5℃ for 0.5h, and then raised to 0℃ and stirred for 3h. Nitrogen protection was maintained throughout the process. After the reaction was completed, the reaction solution was filtered with diatomaceous earth to remove the white precipitate of triethylamine hydrochloride. The filter cake was washed twice with 20ml of dichloromethane. The filtrates were combined and washed once with 50ml of saturated sodium bicarbonate solution, and then twice with 50ml of saturated saline solution. The organic phase was separated, dried with anhydrous sodium sulfate for 2 hours, and the filtrate was evaporated under reduced pressure below 35℃ to remove the solvent, yielding a pale yellow viscous liquid, which is the protected product of diamide Boc. S1-3. Dissolve the 20 mmol of the protected product of bisamide Boc obtained in the previous step in 40 ml of dichloromethane and cool it to 0°C in an ice-water bath. Prepare 10 ml of trifluoroacetic acid and slowly add it to the reaction solution in 5-6 portions, with an interval of about 10 min between each addition. During the addition process, a large amount of heat is released and accompanied by vigorous bubble generation. Carefully control the addition rate to prevent splashing. After the trifluoroacetic acid is added, remove the ice bath and stir the reaction at room temperature for 3 h. After the reaction is completed, remove the trifluoroacetic acid and dichloromethane by rotary evaporation under reduced pressure below 35°C. Redissolve the residue in 50 ml of dichloromethane. Cool the solution in an ice-water bath and slowly add saturated sodium bicarbonate solution to neutralize the pH to 7-8. A large amount of carbon dioxide bubbles are generated during the neutralization process. Carefully control the addition rate to prevent liquid overflow. Separate the liquid and wash the organic phase twice with 30 ml of saturated brine. Separate the organic phase and dry it with anhydrous sodium sulfate for 2 h; filter, and remove the solvent from the filtrate by rotary evaporation under reduced pressure below 35°C to obtain the crude product.

[0024] S1-4. Column chromatography purification: Take 200g of silica gel and pack it into a dry column. Dissolve the crude product in a small amount of dichloromethane, add silica gel and mix. Dry under reduced pressure and then load the sample. Use a mixture of petroleum ether and ethyl acetate as the eluent at a ratio of 3:1. Combine the eluents and remove the solvent by rotary evaporation under reduced pressure below 35°C to obtain a pale yellow to light brown viscous liquid or a low-melting-point solid, which is the target product, the bisfuran-terminated amide monomer F-ED.

[0025] Table 1

[0026] In Table 1 above, several key parameters of Comparative Example 1 deviated significantly from the preferred range, resulting in a total yield of only 5% across the four steps.

[0027] Example 3

[0028] The preparation method of the above-mentioned furan resin material includes the following preparation steps: S1. Mix 75 parts furfuryl alcohol, 10 parts formaldehyde, and 5 parts urea, add 1 part sodium hydroxide (an alkaline catalyst) to adjust the pH to 10, and stir the reaction at 80°C for 1 hour to obtain the prepolymer. S2. Add the bisfuran-terminated amide monomer F-ED to the prepolymer, stir until homogeneous, then add p-toluenesulfonic acid and water, stir until homogeneous, and degas under vacuum for 15 minutes; S3. Inject the degassed mixture into a mold and cure it using a stepped heating process: first, keep it at 60℃ for 2 hours, then at 80℃ for 2 hours, and finally at 100℃ for 5 hours to obtain furan resin material.

[0029] Example 4

[0030] The preparation method of the above-mentioned furan resin material includes the following preparation steps: S1. Mix 80 parts furfuryl alcohol, 15 parts formaldehyde, and 10 parts urea, add 1 part potassium hydroxide as an alkaline catalyst to adjust the pH to 10, and stir the reaction at 80°C for 1 hour to obtain the prepolymer. S2. Add the bisfuran-terminated amide monomer F-ED to the prepolymer, stir until homogeneous, then add p-toluenesulfonic acid and water, stir until homogeneous, and degas under vacuum for 15 minutes; S3. Inject the degassed mixture into a mold and cure it using a stepped heating process: first, keep it at 60℃ for 2 hours, then at 80℃ for 2 hours, and finally at 100℃ for 5 hours to obtain furan resin material.

[0031] Example 5

[0032] The preparation method of the above-mentioned furan resin material includes the following preparation steps: S1. Mix 85 parts furfuryl alcohol, 20 parts formaldehyde, and 15 parts urea, add 2 parts alkaline catalyst sodium hydroxide to adjust the pH to 10, stir and react at 80°C for 1 hour to obtain the prepolymer. S2. Add the bisfuran-terminated amide monomer F-ED to the prepolymer, stir until homogeneous, then add p-toluenesulfonic acid and water, stir until homogeneous, and degas under vacuum for 15 minutes; S3. Inject the degassed mixture into a mold and cure it using a stepped heating process: first, keep it at 60℃ for 2 hours, then at 80℃ for 2 hours, and finally at 100℃ for 5 hours to obtain furan resin material.

[0033] Example 6

[0034] The preparation method of the above-mentioned furan resin material includes the following preparation steps: S1. Mix 78 parts furfuryl alcohol, 12 parts formaldehyde, and 8 parts urea, add 2 parts potassium hydroxide as an alkaline catalyst to adjust the pH to 10, and stir the reaction at 80°C for 1 hour to obtain the prepolymer. S2. Add the bisfuran-terminated amide monomer F-ED to the prepolymer, stir until homogeneous, then add p-toluenesulfonic acid and water, stir until homogeneous, and degas under vacuum for 15 minutes; S3. Inject the degassed mixture into a mold and cure it using a stepped heating process: first, keep it at 60℃ for 2 hours, then at 80℃ for 2 hours, and finally at 100℃ for 5 hours to obtain furan resin material.

[0035] Comparative Example 2 The main difference between Comparative Example 2 and Example 4 is that 10 parts by weight of F-ED monomer were added in S1, and furfuryl alcohol was changed to 90 parts, while the rest remained unchanged.

[0036] Comparative Example 3 The main difference between Comparative Example 3 and Example 4 is that 30 parts by weight of F-ED monomer were added in S1, and furfuryl alcohol was changed to 70 parts, while the rest remained unchanged.

[0037] Comparative Example 4 The main difference between Comparative Example 4 and Example 4 is that F-ED monomer is not added in S1.

[0038] Comparative Example 5 The main difference between Comparative Example 5 and Example 4 is that 8 parts by weight of p-toluenesulfonic acid were added in S2.

[0039] Comparative Example 6 The main difference between Comparative Example 6 and Example 4 is that in S3, the temperature was directly maintained at 100°C for 6 hours without pre-curing at 60°C and 80°C.

[0040] Comparative Example 7 The main difference between Comparative Example 7 and Example 4 is that urea is not added, while the other components and preparation methods are the same.

[0041] Comparative Example 8 The main difference between Comparative Example 8 and Example 4 is that the latter uses commercially available furan resin.

[0042] Performance testing: Infrared testing: Fourier transform infrared spectrometer was used, with a wavenumber range of 4000-400 cm⁻¹. -1 4 cm resolution -1Scan 16-32 times; Before testing 2 mg of sample and 200 mg of KBr, collect the background data using the liquid film method, then place the sample in the sample chamber or on an ATR crystal to collect the spectrum. After obtaining the spectrum, perform baseline correction and peak position calibration.

[0043] Hardness Testing: Refer to GB / T 2648I "Test Methods for Mixtures". Before testing, calibrate the hardness tester on a standard block. Place the furan resin cured samples (50mm × 50mm × 6mm in size, cast according to their respective formulations and curing processes) prepared in each example and comparative example on a horizontal hard platform. Measure the hardness at five different locations on the sample surface. During testing, press the indenter foot of the hardness tester firmly onto the sample surface, with the indenter perpendicular to the sample surface, and read the maximum hardness value within one second. Measure five points on each sample and take the arithmetic mean as the final hardness value.

[0044] Tensile strength: Referring to the standard test method for self-hardening furan resin for casting, the core sand was mixed with the resin at a mass ratio of 100:1.5 for 2 minutes. Immediately after mixing, the mixture was filled into a figure-eight shaped standard specimen mold and allowed to cure at room temperature. One hour after the start of sample preparation, the specimen was removed from the mold and placed on a universal testing machine. The test was conducted at a tensile rate of 10 mm / min, and the maximum tensile load at fracture was recorded.

[0045] Table 2

[0046] According to Table 2, Example 4 achieved a hardness of 95, with 1-hour strength of 2.34 MPa and 24-hour strength of 3.12 MPa, both the highest. This indicates that under moderate furfuryl alcohol content and appropriate F-ED conditions, the prepolymerization and crosslinking network reached an optimal balance. Example 5 had slightly lower hardness, possibly due to excessive network flexibility caused by an excessively high F-ED ratio. Examples 3 and 6 were at moderate levels. The strengths of Comparative Examples 2 and 3 were lower than those of the Examples, indicating that insufficient F-ED content resulted in insufficient crosslinking density and limited toughening effect, while excessive F-ED content introduced too many flexible segments, thus reducing mechanical properties. Comparative Example 4, which did not contain F-ED, had a high resin network rigidity but internal stress... The results showed that the overall mechanical properties of furan resin were poor. In Comparative Example 5, excessive acid catalyst led to rapid curing, microcracks in the system, and a sharp decrease in hardness and strength. Comparative Example 6 used a one-step high-temperature curing process without a low-temperature pre-curing stage, resulting in disordered molecular chain arrangement, concentrated internal stress, and performance inferior to the gradient heating process. Comparative Example 7 lacked urea, had insufficient pre-condensation, numerous network defects, and low strength and hardness. Comparative Example 8 used commercially available ordinary furan resin without added F-ED and with an unoptimized formulation, resulting in poor performance. These data indicate that this invention effectively improves the comprehensive mechanical properties of furan resin by introducing the bis-furan terminal amide monomer F-ED, optimizing the component ratio, and employing a step-curing process.

[0047] from Figure 1 It can be seen from this that in the range of 500-1500 cm -1 The absorption intensity of Comparative Example 8 remained consistently above 0.90, while the absorption intensity of Example 4 in this region was only 0.20-0.60, and showed a significant increasing trend with increasing wavenumber. This indicates that the F-ED monomer introduced in this invention successfully bonded to the resin network, bringing characteristic absorptions such as amide bonds, and significantly altering the molecular skeleton vibration and substituent structure; in the 1500-3500 cm⁻¹ range... -1 The absorption intensity of Example 4 gradually increased and approached the 0.99-1.00 level of Comparative Example 8, indicating that the modification did not destroy the main structure of the furan resin, but rather introduced the primary amine bonds NH and C=O, thereby significantly enriching the chemical composition while maintaining the main skeleton. The infrared spectral data fully confirmed that the modified furan resin prepared in this invention has significantly different chemical structural characteristics compared with commercially available products, and the F-ED monomer and F-ED@m-BN have been effectively anchored in the resin network through chemical bonds.

[0048] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A furan resin material, characterized in that: Composed of the following parts by weight: 75-85 parts furfuryl alcohol, 10-20 parts formaldehyde, 5-15 parts urea, 15-25 parts bisfuran-terminated amide monomer F-ED, and 3-5 parts p-toluenesulfonic acid.

2. The furan resin material according to claim 1, characterized in that: The preparation steps of the amide monomer F-ED with bisfuran end groups are as follows: S1-1. N-(4-aminophenyl)ethylenediamine was dissolved in anhydrous dichloromethane, and 4-dimethylaminopyridine and ditert-butyl dicarbonate were added. The mixture was stirred at room temperature under nitrogen protection. The reaction solution was washed successively with sodium bicarbonate solution and saturated brine, dried over anhydrous sodium sulfate, and rotary evaporated to obtain the Boc protected intermediate. S1-2. Dissolve the Boc protecting intermediate in anhydrous dichloromethane, add triethylamine, cool in an ice-salt bath, and slowly add a dichloromethane solution of furanoyl chloride. React at low temperature. After the reaction is complete, filter to remove triethylamine hydrochloride. Wash the reaction solution with sodium bicarbonate solution and saturated brine in sequence. Dry with anhydrous sodium sulfate and rotary evaporate to obtain the Boc protecting product. S1-3. The protected product of bisamide Boc was dissolved in dichloromethane, cooled in an ice bath under nitrogen protection, and trifluoroacetic acid was slowly added. The reaction was stirred at room temperature. The reaction solution was slowly poured into ice water to quench the reaction, extracted with dichloromethane, and the organic phase was washed successively with saturated sodium bicarbonate solution and saturated brine. After drying, the crude product was obtained by rotary evaporation. S1-4. The crude product from step S1-3 was purified by column chromatography using petroleum ether-ethyl acetate as the eluent. The target component was collected and evaporated to dryness to obtain the F-ED monomer.

3. The furan resin material according to claim 2, characterized in that: In step S1-1, the molar ratio of N-(4-aminophenyl)ethylenediamine, ditert-butyl dicarbonate, and 4-dimethylaminopyridine is 1:(1.1-1.3):(0.05-0.1), the reaction temperature is 20-30℃, and the reaction time is 4-12h.

4. The furan resin material according to claim 2, characterized in that: In steps S1-2, the molar ratio of Boc protecting intermediate, triethylamine, and furanoyl chloride is 1:(2.0-2.5):(2.0-2.2), the reaction temperature is -10 to 0℃, and the reaction time is 1-4 h.

5. The furan resin material according to claim 2, characterized in that: In steps S1-3, the molar ratio of the bisamide Boc protected product to trifluoroacetic acid is 1:(10-20), the reaction temperature is 0-30℃, and the reaction time is 2-3h.

6. The furan resin material according to claim 2, characterized in that: In steps S1-4, the eluent for column chromatography purification is petroleum ether to ethyl acetate in a volume ratio of 1:2, with the addition of 0.1-0.5% triethylamine.

7. The method for preparing furan resin material according to claim 1, characterized in that, The preparation steps include the following: S1. Mix furfuryl alcohol, formaldehyde, and urea, add an alkaline catalyst to adjust the pH to 8-10, and stir the reaction at 60-80℃ for 1-2 hours to obtain the prepolymer. S2. Add the bisfuran-terminated amide monomer F-ED to the prepolymer, stir until homogeneous, then add p-toluenesulfonic acid, stir until homogeneous, and degas under vacuum for 10-15 minutes. S3. Inject the degassed mixture into a mold and cure it using a stepped heating process: first, keep it at 60℃ for 1-2 hours, then at 80℃ for 2 hours, and finally at 100℃ for 4-6 hours to obtain furan resin material.

8. The method for preparing furan resin material according to claim 7, characterized in that: The alkaline catalyst is sodium hydroxide, potassium hydroxide, or ammonia.

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