Cardanol-rosin bio-based epoxy resin as well as preparation method and application thereof

Abstract

The invention discloses cardanol-rosin bio-based epoxy resin, which is prepared from the following raw materials in parts by weight: 100 to 300 parts of cardanol, 700 to 900 parts of thiohydracrylic acid, 150 to 200 parts of cardanol glycidyl ether, 20 to 60 parts of metachloroperbenzoic acid, 100 to 300 parts of glycidyl ether, 0.6 to 1.5 parts of catalyst, 0.3 to 1.5 parts of polymerization inhibitor and 5 to 30 parts of acrylic acid rosin. According to the cardanol-rosin bio-based epoxy resin disclosed by the invention, a flexible long-chain structure of cardanol and a rigid phenanthrene ring skeleton of rosin are subjected to molecular-level collaborative design, and the obtained epoxy resin has rigidity and toughness balance. The invention further discloses a preparation method and application of the cardanol-rosin bio-based epoxy resin.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and in particular relates to a cardanol-rosin bio-based epoxy resin and a preparation method and application thereof. Background Art

[0002] Traditional epoxy resins rely heavily on petroleum-based raw materials (such as bisphenol A epoxy resins), resulting in environmental pollution, high flammability, brittleness, and insufficient heat resistance. Bio-based resins, with their renewable, environmentally friendly, and low-toxic properties, have become a promising alternative to traditional resins. While bio-based epoxy resins (such as cardanol and rosin-based) can alleviate resource dependence, single bio-based sources present performance limitations. Cardanol-based resins exhibit poor thermal stability, while rosin-based resins exhibit significant brittleness.

[0003] Existing compounding technologies struggle to balance the performance and environmental friendliness of epoxy resins due to poor interfacial compatibility, complex processes, and limited biobased content. This invention addresses this technological gap by designing an epoxy resin that achieves a synergistic breakthrough in combining high biobased content with excellent thermal stability, addressing the urgent need for green, high-performance materials in fields such as aerospace and new energy vehicles. Summary of the Invention

[0004] The purpose of the present invention is to provide a cardanol-rosin bio-based epoxy resin and its preparation method and application, so as to solve the technical problem that it is difficult to strike a balance between the performance and environmental protection of epoxy resin.

[0005] According to a first aspect of the present invention, a cardanol-rosin bio-based epoxy resin is provided. The raw materials thereof include, by weight, 100-300 parts of cardanol, 700-900 parts of mercaptopropionic acid, 150-200 parts of cardanol glycidyl ether, 20-60 parts of m-chloroperbenzoic acid, 100-300 parts of glycidyl ether, 0.6-1.5 parts of a catalyst, 0.3-1.5 parts of an inhibitor, and 5-30 parts of acrylic rosin.

[0006] It should be noted that among the above raw materials, cardanol and mercaptopropionic acid can be prepared by a photoclick reaction to obtain cardanol mercapto acid; cardanol glycidyl ether is reacted with m-chloroperbenzoic acid to obtain epoxy cardanol glycidyl ether, which can be used as a reactive diluent to dilute the resin.

[0007] In some embodiments, the glycidyl ether has three or more branched structures, and has an epoxy group in each of the branched structures.

[0008] In some embodiments, the glycidyl ether is selected from at least one of glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol triglycidyl ether, and pentaerythritol triglycidyl ether.

[0009] In some embodiments, the glycidyl ether has an epoxy equivalent weight of 128-180 g / mol.

[0010] In some embodiments, the catalyst is selected from at least one of benzyltriethylammonium chloride, dibutyltin dilaurate, triethylamine, benzyldiamine, and triphenylphosphine.

[0011] In some embodiments, the polymerization inhibitor is selected from at least one of hydroquinone, p-tert-butylcatechol, and catechol.

[0012] According to a second aspect of the present invention, there is provided a method for preparing a cardanol-rosin bio-based epoxy resin, comprising the following steps: (1) performing a photo-click reaction between cardanol and mercaptopropionic acid to obtain cardanol mercapto acid; (2) mixing cardanol glycidyl ether with m-chloroperbenzoic acid to carry out epoxidation reaction to obtain epoxy cardanol glycidyl ether; (3) Under the action of a catalyst and an inhibitor, cardanol mercapto acid and acrylic rosin are esterified with glycidyl ether, and finally a diluent, epoxy cardanol glycidyl ether, is added to obtain a cardanol-rosin bio-based epoxy resin.

[0013] In some embodiments, in step (2), after the cardanol glycidyl ether and m-chloroperbenzoic acid are mixed, sodium carbonate is added to the mixed system, and the amount of sodium carbonate used is 10-30 parts by weight.

[0014] In some embodiments, in step (3), the glycidyl ether is first subjected to an esterification reaction with acrylic rosin under the action of a catalyst and a polymerization inhibitor, and then the cardanol mercapto acid is added to continue the reaction.

[0015] The present invention prepares a high-biobased epoxy resin using cardanol, acrylic rosin and glycidyl ether as main raw materials. Cardanol and mercaptopropionic acid are subjected to a photoclick reaction to prepare a cardanol-based polyacid, which is then reacted with acrylic rosin and glycerol triglycidyl ether to prepare bio-based epoxy resins in different proportions. The high-biobased epoxy resin not only has good thermal stability and mechanical properties, but also fully embodies the concept of green chemistry, providing related industries with a high-performance, environmentally friendly new material solution.

[0016] Cardanol contains benzene rings, phenol, and long side chain aliphatic groups. Its side chain double bonds can be modified through photo-click reactions, introducing new functional groups to further obtain carboxylic acid structures, which can participate in the ring-opening of epoxy. Furthermore, the long side chain aliphatic groups of cardanol can increase the toughness of vinyl resins. Acrylic rosin, with natural rosin acid as its core skeleton, contains a rigid phenanthrene ring structure, acrylate groups, and reactive carboxylic acid functional groups. Furthermore, the carboxylic acid groups can undergo ring-opening reactions with epoxy groups, enhancing the strength of the interfacial chemical bond. Furthermore, the rigid skeleton of the phenanthrene rings of rosin acid can effectively enhance the heat resistance of the resin, while the flexible design of the cardanol side chains can alleviate the brittle defects of rosin-based materials, achieving a balance between rigidity and toughness.

[0017] In some embodiments, the method for preparing the cardanol-rosin bio-based epoxy resin comprises the following steps: (1) reacting cardanol with mercaptopropionic acid and a photoinitiator under ultraviolet light (UV) with a wavelength of 300-400 nm for 3-7 hours, and observing the complete disappearance of the double bond peak of the reaction product by infrared spectroscopy, thus reaching the reaction endpoint, and obtaining cardanol mercapto acid; (2) dissolving m-chloroperbenzoic acid in an organic solvent at 0-4° C. to obtain a first organic solvent, dissolving cardanol glycidyl ether in an organic solvent to obtain a second organic solvent, and then dropwise adding the second organic solvent to the first organic solvent to perform an epoxidation reaction, and purifying to obtain epoxy cardanol glycidyl ether; (3) reacting the glycidyl ether, catalyst, polymerization inhibitor and acrylic rosin at 95-130° C. for 0.5-3 hours until the acid value is less than 30 mg KOH / g, then adding the cardanol mercapto acid prepared in step (1), continuing to react at 85-110° C. for 1-4 hours until the acid value is less than 30 mg KOH / g, then cooling to below 80° C., adding the epoxy cardanol glycidyl ether prepared in step (2), and mixing uniformly to obtain the product.

[0018] In some embodiments, the ratio of cardanol to mercaptopropionic acid in step (1) is 1 mol: (3.5-6.0) mol, preferably 1 mol: (4.0-5.0) mol.

[0019] In some embodiments, the photoinitiator in step (1) is selected from at least one of benzophenone, 2-hydroxy-2-methylpropiophenone (PI-1173), and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO).

[0020] In some embodiments, in step (1), after the reaction of cardanol and mercaptopropionic acid, cardanol mercapto acid can be obtained by the following purification step: dissolving the product of the reaction of cardanol and mercaptopropionic acid with an organic solvent, then transferring the organic solvent to a separatory funnel, washing with deionized water until the aqueous phase is no longer turbid, and then removing the organic solvent by rotary evaporation of the organic phase at 45° C. Specifically, the organic solvent is dichloromethane, which acts as a solvent to extract the cardanol mercapto acid from the product.

[0021] In some embodiments, in step (2), the organic solvent is dichloromethane.

[0022] In some embodiments, in step (2), after the second organic solvent is dropwise added to the first organic solvent, sodium carbonate is added to the first organic solvent, stirred, and the epoxidation reaction is carried out. Specifically, the purpose of adding sodium carbonate is to provide an alkaline environment for the epoxidation reaction, thereby neutralizing the byproduct acid (m-chlorobenzoic acid) produced during the epoxidation reaction of m-CPBA, thereby ensuring that the epoxidation reaction proceeds in a positive direction. The amount of sodium carbonate used is 10-30 parts by weight, and the mixture is stirred for 20-40 minutes after adding the sodium carbonate.

[0023] In some embodiments, in step (2), the purification method is to first remove the solid by suction filtration, then remove the organic solvent by rotary evaporation, then dissolve the product after rotary evaporation with ether, then wash with saturated sodium salt solution, then remove moisture with a desiccant, filter and retain the filtrate, and then remove the solvent in vacuo.

[0024] Specifically, the solid is first removed by filtration, and then the organic solvent is removed by rotary evaporation. The product after rotary evaporation is then dissolved in ether, and then washed three times with saturated Na2S2O3, saturated NaHCO3, and saturated NaCl respectively. The moisture is then removed with anhydrous MgSO4, the filtrate is filtered and retained, and the solvent is then removed in vacuo. The epoxy value is determined to obtain epoxy cardanol glycidyl ether.

[0025] In some embodiments, in step (3), the amount of cardanol mercapto acid used is 10-50 parts by weight, and the amount of epoxy cardanol glycidyl ether used is 100-200 parts by weight.

[0026] In some embodiments, in step (3), the molar ratio of glycidyl ether, cardanol mercapto acid, and acrylic rosin is 1:(0.04-0.18):(0.04-0.18). Preferably, the molar ratio of glycidyl ether, cardanol mercapto acid, and acrylic rosin is 1:(0.08-0.11):(0.08-0.11).

[0027] In some embodiments, in step (3), the amount of the catalyst is 0.4-2.0 wt % of the total mass of glycidyl ether, cardanol mercapto acid, and acrylic rosin. Preferably, the amount of the catalyst is 0.4-1.0 wt % of the total mass of glycidyl ether, cardanol mercapto acid, and acrylic rosin.

[0028] In some embodiments, in step (3), the amount of the polymerization inhibitor is 0.015-0.05 wt % of the total mass of glycidyl ether, cardanol mercapto acid, and acrylic rosin. Preferably, the amount of the polymerization inhibitor is 0.015-0.025 wt % of the total mass of glycidyl ether, cardanol mercapto acid, and acrylic rosin.

[0029] According to a third aspect of the present invention, there is provided the use of cardanol-rosin bio-based epoxy resin in the preparation of adhesives and packaging materials.

[0030] Specifically, adhesives and packaging materials can be used in technical fields such as aerospace, new energy vehicles, smart materials, and environmental remediation.

[0031] The beneficial effects of the present invention include: (1) The cardanol-rosin bio-based epoxy resin of the present invention uses cardanol and acrylic rosin as raw materials, has a high bio-based content, and has both the flexible long-chain structure of cardanol and the rigid phenanthrene ring skeleton of rosin.

[0032] (2) The present invention uses molecular-level collaborative design to combine the flexible long-chain structure of cardanol with the rigid phenanthrene ring skeleton of rosin, and utilizes the carboxylic acid groups of acrylic rosin and cardanol mercapto acid to undergo ring-opening esterification with the epoxy groups of glycidyl ether to construct a bio-based epoxy resin system with both rigidity and toughness balance. Specifically, the phenanthrene ring structure of rosin forms a rigid network with high cross-linking density through the ring-opening reaction of carboxylic acid and epoxy groups, while the C15 long side chain of cardanol containing unsaturated double bonds also has a structure with difunctional carboxylic acid groups after modification. It can also give the system toughness through cross-linking and dynamic hydrogen bond recombination, thereby overcoming the defect of unbalanced performance of a single bio-based resin. As the amount of cardanol mercapto acid and acrylic rosin changes, the glass transition temperature of the heat-cured film shows regular changes, thereby making it possible to regularly regulate the glass transition temperature of the heat-cured film.

[0033] (3) The resin prepared by the present invention has a uniform appearance without stratification and a low viscosity, and is suitable for preparing adhesives and packaging materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a reaction scheme of the cardanol mercapto acid of the present invention; Figure 2 is the reaction scheme of epoxy cardanol glycidyl ether of the present invention; Figure 3 is a reaction scheme of the cardanol-rosin bio-based epoxy resin of the present invention; Figure 4 This is a Fourier transform infrared spectrum of cardanol and cardanol mercapto acid in Example 1 of the present invention; Figure 5 This is the hydrogen nuclear magnetic resonance spectrum of the cardanol-rosin bio-based epoxy resin in Example 1 of the present invention; Figure 6 The system shear rate-viscosity curves of the cardanol-rosin bio-based epoxy resins of Examples 1-3 of the present invention, the rosin-based epoxy resin of Comparative Example 1, and the cardanol-based epoxy resin of Comparative Example 2 are shown. DETAILED DESCRIPTION

[0035] The present invention will be further described in detail below with reference to the accompanying drawings, but the embodiments of the present invention are not limited thereto. The raw materials and reagents involved in the following examples can all be obtained from commercial channels.

[0036] The preparation method of the cardanol-rosin bio-based epoxy resin of the present invention comprises the following steps: (1) Cardanol (CA) is photo-clicked with mercaptopropionic acid to obtain cardanol mercapto acid (CAMP); (2) epoxidizing cardanol glycidyl ether with m-chloroperbenzoic acid to obtain epoxy cardanol glycidyl ether; (3) Under the action of a catalyst and an inhibitor, glycidyl ether is first esterified with acrylic rosin (AAR), and then cardanol mercapto acid is added to the reaction system to react with glycidyl ether for esterification, and finally the diluent epoxy cardanol glycidyl ether is added to obtain cardanol-rosin bio-based epoxy resin (GTAAC).

[0037] Among them, the reaction route of cardanol mercapto acid is shown in Figure 1 The reaction route of epoxy cardanol glycidyl ether is shown in Figure 2 The reaction route of cardanol-rosin bio-based epoxy resin is shown in Figure 3 .

[0038] It should be noted that the melting point of acrylic rosin is around 120°C. The reason acrylic rosin is added first in the present invention is to allow it to melt and react with the glycidyl ether. If cardanol mercapto acid is added first to react with the glycidyl ether, the temperature will be too high when the acrylic rosin reacts with it, potentially leading to excessive crosslinking and direct solidification of the grafted groups.

[0039] Example 1 This embodiment provides a method for preparing a cardanol-rosin bio-based epoxy resin, comprising the following steps: (1) 150.0 g of cardanol, 882.2 g of mercaptopropionic acid and 3.3 g of PI-1173 photoinitiator were placed in a 500 mL round-bottom flask, stirred magnetically and irradiated under 365 nm ultraviolet light. The reaction endpoint was reached when the double bond peak disappeared completely by infrared observation. Then 300 g of dichloromethane was added to the round-bottom flask to dissolve the solution and the solution was transferred to a separatory funnel. The solution was washed with deionized water until the water layer was no longer turbid. The organic phase was then rotary evaporated at 45 °C to remove dichloromethane to obtain light yellow transparent cardanol mercapto acid.

[0040] (2) In an ice-water bath at 0-4°C, dissolve 43.9 g of m-chloroperbenzoic acid in an appropriate amount of dichloromethane and transfer the solvent to a 1000 mL three-necked flask. Then dissolve 178.4 g of cardanol glycidyl ether in an appropriate amount of dichloromethane and transfer the solvent to a 250 mL constant pressure funnel. Slowly drip the dichloromethane in the constant pressure funnel into the three-necked flask at 250 r·min. -1 Stir the solvent in the three-necked flask at a stirring rate of 100 [min / min]. After the addition is complete, slowly add 18.3 g of Na₂CO₃ to the flask and continue stirring for 30 minutes. After stirring, filter to remove impurities and remove the solvent by rotary evaporation. The product after rotary evaporation is dissolved in an appropriate amount of ether and then washed three times with saturated Na₂S₂O₃, saturated NaHCO₃, and saturated NaCl, respectively. Remove moisture with anhydrous MgSO₄, filter, and remove the solvent in vacuo to obtain a light yellow epoxy cardanol glycidyl ether.

[0041] (3) In a 500 mL round-bottom flask, 196.89 g of glycerol triglycidyl ether (epoxy equivalent of 143-154 g / mol) and 33.83 g of acrylic rosin were added and heated to 120°C and mixed evenly. 0.0506 g of hydroquinone (a polymerization inhibitor) and 1.2620 g of benzyltriethylammonium chloride (a catalyst) were then added and reacted at 120°C until the acid value was less than 30 mgKOH / g. 22.53 g of cardanol mercapto acid was then added to the reaction system and reacted at 110°C until the acid value was less than 30 mgKOH / g. After the reaction system was cooled to below 80°C, 155.30 g of epoxy cardanol glycidyl ether was added and mixed evenly to obtain a light yellow transparent cardanol-rosin bio-based epoxy resin.

[0042] Cardanol (CA) and cardanol mercapto acid (CAMP) were characterized by Fourier transform infrared spectroscopy (FT-IR). Figure 4 As shown. Figure 4 It can be seen that in the FT-IR spectrum of CA, the 3010 cm -1 The characteristic peak at 2928 cm corresponds to the CH characteristic stretching vibration of C=CH on the side chain; -1 and 2855 cm -1The characteristic peak at 3010 cm corresponds to the asymmetric stretching of methylene and methyl groups in the long fatty chain. In the FT-IR spectrum of CAMP, it can be found that after the photo-click reaction of cardanol and mercaptopropionic acid, the peak at 3010 cm -1 The peak of 2500-2600 cm-1 disappeared, indicating that mercaptopropionic acid reacted completely with the double bond of the cardanol side chain, and a new peak of 2500-2600 cm-1 appeared. -1 The peak at 1704 cm is attributed to the characteristic absorption peak of -SH; -1 The peak at corresponds to the carbonyl peak of C=O on the carboxyl group, indicating that cardanol has been successfully grafted with mercaptopropionic acid, and the product is cardanol mercapto acid. FT-IR results show that cardanol mercapto acid was successfully synthesized.

[0043] Cardanol mercapto acid (CAMP), acrylic rosin (AAR), and cardanol-rosin bio-based epoxy resin (GTAAC) were characterized by nuclear magnetic resonance hydrogen spectrum. Figure 5 As shown. Figure 5 It can be seen that in CAMP 1 In the H NMR spectrum, the peak at 12.20-12.30 ppm corresponds to the hydrogen on the -COOH of mercaptopropionic acid, and the peak at 6.50-7.10 ppm is the characteristic chemical shift of the double bond on the benzene ring; 1 In the H NMR spectrum, the peak at 12.20-12.30 ppm corresponds to the hydrogen on the -COOH of rosin acrylate, and the peak at 5.20-5.30 ppm is the characteristic chemical shift of the carbon-carbon double bond; 1 In the HNMR spectrum, the peak at 6.50-7.10 ppm corresponds to the characteristic chemical shift of the double bond on the benzene ring of CAMP, the peak at 5.20-5.30 ppm corresponds to the characteristic chemical shift of the carbon-carbon double bond on AAR, and the peak at 12.20-12.30 ppm disappears. These results confirm the successful synthesis of GTAAC.

[0044] Example 2 This embodiment provides a method for preparing a cardanol-rosin bio-based epoxy resin, comprising the following steps: (1) 150.0 g of cardanol, 882.2 g of mercaptopropionic acid and 3.3 g of PI-1173 photoinitiator were placed in a 500 mL round-bottom flask, stirred magnetically and irradiated under 365 nm ultraviolet light. The reaction endpoint was reached when the double bond peak disappeared completely by infrared observation. Then 300 g of dichloromethane was added to the round-bottom flask to dissolve the solution and the solution was transferred to a separatory funnel. The solution was washed with deionized water until the water layer was no longer turbid. The organic phase was then rotary evaporated at 45 °C to remove dichloromethane to obtain light yellow transparent cardanol mercapto acid.

[0045] (2) In an ice-water bath at 0-4°C, dissolve 43.9 g of m-chloroperbenzoic acid in an appropriate amount of dichloromethane and transfer the solvent to a 1000 mL three-necked flask. Then dissolve 178.4 g of cardanol glycidyl ether in an appropriate amount of dichloromethane and transfer the solvent to a 250 mL constant pressure funnel. Slowly drip the dichloromethane in the constant pressure funnel into the three-necked flask at 250 r·min. -1 Stir the solvent in the three-necked flask at a stirring rate of 100 [min / min]. After the addition is complete, slowly add 18.3 g of Na₂CO₃ to the flask and continue stirring for 30 minutes. After stirring, filter to remove impurities and remove the solvent by rotary evaporation. The product after rotary evaporation is dissolved in an appropriate amount of ether and then washed three times with saturated Na₂S₂O₃, saturated NaHCO₃, and saturated NaCl, respectively. Remove moisture with anhydrous MgSO₄, filter, and remove the solvent in vacuo to obtain a light yellow epoxy cardanol glycidyl ether.

[0046] (3) 196.89 g of glycerol triglycidyl ether (epoxy equivalent of 143-154 g / mol) and 25.38 g of acrylic rosin were placed in a 500 mL round-bottom flask, heated to 120°C and mixed evenly. 0.0512 g of hydroquinone (a polymerization inhibitor) and 1.2802 g of benzyltriethylammonium chloride (a catalyst) were then added and reacted at 120°C until the acid value was less than 30 mgKOH / g. 33.78 g of cardanol mercapto acid was then added to the reaction system and reacted at 110°C until the acid value was less than 30 mgKOH / g. After the reaction system was cooled to below 80°C, 155.30 g of epoxy cardanol glycidyl ether was added and mixed evenly to obtain a light yellow transparent cardanol-rosin bio-based epoxy resin.

[0047] Example 3 This embodiment provides a method for preparing a cardanol-rosin bio-based epoxy resin, comprising the following steps: (1) 150.0 g of cardanol, 882.2 g of mercaptopropionic acid and 3.3 g of PI-1173 photoinitiator were placed in a 500 mL round-bottom flask, stirred magnetically and irradiated under 365 nm ultraviolet light. The reaction endpoint was reached when the double bond peak disappeared completely by infrared observation. Then 300 g of dichloromethane was added to the round-bottom flask to dissolve the solution and the solution was transferred to a separatory funnel. The solution was washed with deionized water until the water layer was no longer turbid. The organic phase was then rotary evaporated at 45 °C to remove dichloromethane to obtain light yellow transparent cardanol mercapto acid.

[0048] (2) In an ice-water bath at 0-4°C, dissolve 43.9 g of m-chloroperbenzoic acid in an appropriate amount of dichloromethane and transfer the solvent to a 1000 mL three-necked flask. Then dissolve 178.4 g of cardanol glycidyl ether in an appropriate amount of dichloromethane and transfer the solvent to a 250 mL constant pressure funnel. Slowly drip the dichloromethane in the constant pressure funnel into the three-necked flask at 250 r·min. -1 Stir the solvent in the three-necked flask at a stirring rate of 100 [min / min]. After the addition is complete, slowly add 18.3 g of Na₂CO₃ to the flask and continue stirring for 30 minutes. After stirring, filter to remove impurities and remove the solvent by rotary evaporation. The product after rotary evaporation is dissolved in an appropriate amount of ether and then washed three times with saturated Na₂S₂O₃, saturated NaHCO₃, and saturated NaCl, respectively. Remove moisture with anhydrous MgSO₄, filter, and remove the solvent in vacuo to obtain a light yellow epoxy cardanol glycidyl ether.

[0049] (3) 196.89 g of glycerol triglycidyl ether (epoxy equivalent of 143-154 g / mol) and 16.92 g of acrylic rosin were placed in a 500 mL round-bottom flask, heated to 120°C and mixed evenly. 0.0517 g of hydroquinone (a polymerization inhibitor) and 1.2943 g of benzyltriethylammonium chloride (a catalyst) were then added and reacted at 120°C until the acid value was less than 30 mgKOH / g. 45.04 g of cardanol mercapto acid was then added to the reaction system and reacted at 110°C until the acid value was less than 30 mgKOH / g. After the reaction system was cooled to below 80°C, 155.30 g of epoxy cardanol glycidyl ether was added and mixed evenly to obtain a light yellow transparent cardanol-rosin bio-based epoxy resin.

[0050] Comparative Example 1 This comparative example provides a method for preparing a rosin-based epoxy resin, comprising the following steps: (1) In an ice-water bath at 0-4°C, dissolve 43.9 g of m-chloroperbenzoic acid in an appropriate amount of dichloromethane and transfer the solvent to a 1000 mL three-necked flask. Then dissolve 178.4 g of cardanol glycidyl ether in an appropriate amount of dichloromethane and transfer the solvent to a 250 mL constant pressure funnel. Slowly drip the dichloromethane in the constant pressure funnel into the three-necked flask at 250 r·min. -1 Stir the solvent in the three-necked flask at a stirring rate of 100 [min / min]. After the addition is complete, slowly add 18.3 g of Na₂CO₃ to the flask and continue stirring for 30 minutes. After stirring, filter to remove impurities and remove the solvent by rotary evaporation. The product after rotary evaporation is dissolved in an appropriate amount of ether and then washed three times with saturated Na₂S₂O₃, saturated NaHCO₃, and saturated NaCl, respectively. Remove moisture with anhydrous MgSO₄, filter, and remove the solvent in vacuo to obtain a light yellow epoxy cardanol glycidyl ether.

[0051] (2) In a 500 mL round-bottom flask, 196.89 g of propylene glycol triglycidyl ether (epoxy equivalent of 143-154 g / mol) and 50.75 g of acrylic rosin were added, heated to 120 °C and mixed evenly. Then, 0.0495 g of hydroquinone (a polymerization inhibitor) and 1.2381 g of benzyltriethylammonium chloride (a catalyst) were added and reacted at 120 °C until the acid value was less than 30 mgKOH / g. After the reaction system was cooled to below 80 °C, 155.30 g of epoxy cardanol glycidyl ether was added and mixed evenly to obtain a light yellow transparent rosin-based epoxy resin.

[0052] Comparative Example 2 This comparative example provides a method for preparing a cardanol-based epoxy resin, comprising the following steps: (1) 150.0 g of cardanol, 882.2 g of mercaptopropionic acid and 3.3 g of PI-1173 photoinitiator were placed in a 500 mL round-bottom flask, stirred magnetically and irradiated under 365 nm ultraviolet light. The reaction endpoint was reached when the double bond peak disappeared completely by infrared observation. Then 300 g of dichloromethane was added to the round-bottom flask to dissolve the solution and the solution was transferred to a separatory funnel. The solution was washed with deionized water until the water layer was no longer turbid. The organic phase was then rotary evaporated at 45 °C to remove dichloromethane to obtain light yellow transparent cardanol mercapto acid.

[0053] (2) In an ice-water bath at 0-4°C, dissolve 43.9 g of m-chloroperbenzoic acid in an appropriate amount of dichloromethane and transfer the solvent to a 1000 mL three-necked flask. Then dissolve 178.4 g of cardanol glycidyl ether in an appropriate amount of dichloromethane and transfer the solvent to a 250 mL constant pressure funnel. Slowly drip the dichloromethane in the constant pressure funnel into the three-necked flask at 250 r·min. -1 Stir the solvent in the three-necked flask at a stirring rate of 100 [min / min]. After the addition is complete, slowly add 18.3 g of Na₂CO₃ to the flask and continue stirring for 30 minutes. After stirring, filter to remove impurities and remove the solvent by rotary evaporation. The product after rotary evaporation is dissolved in an appropriate amount of ether and then washed three times with saturated Na₂S₂O₃, saturated NaHCO₃, and saturated NaCl, respectively. Remove moisture with anhydrous MgSO₄, filter, and remove the solvent in vacuo to obtain a light yellow epoxy cardanol glycidyl ether.

[0054] (3) In a 500 mL round-bottom flask, 196.89 g of glycerol triglycidyl ether (epoxy equivalent weight: 143-154 g / mol) and 67.56 g of cardanol mercapto acid were added. 0.0517 g of hydroquinone (a polymerization inhibitor) and 1.2943 g of benzyltriethylammonium chloride (a catalyst) were then added. The temperature was raised to 110°C and the mixture was reacted until the acid value was less than 30 mgKOH / g. After the reaction system was cooled to below 80°C, 155.30 g of epoxy cardanol glycidyl ether was added and mixed uniformly to obtain a cardanol-based epoxy resin.

[0055] In order to detect the comprehensive mechanical properties and thermal stability of the cardanol-rosin bio-based epoxy resin prepared by the present invention, the cardanol-rosin bio-based epoxy resins prepared in Examples 1-3, the rosin-based epoxy resin prepared in Comparative Example 1, and the cardanol-based epoxy resin systems prepared in Comparative Example 2 were subjected to viscosity tests. The resins were then made into heat-cured films, and the obtained resin cured films were subjected to plastic tensile properties tests, dynamic thermal mechanical properties tests, and thermogravimetric tests.

[0056] 1. Preparation of resin thermal curing film The cardanol-rosin bio-based epoxy resins prepared in Examples 1-3, the rosin-based epoxy resin prepared in Comparative Example 1, and the cardanol-based epoxy resin prepared in Comparative Example 2 were mixed uniformly with a curing agent. The mixture was then placed in a vacuum drying oven (80°C) for two hours to produce a heat-cured film. The curing agent used was DMP-30, and the amount of curing agent used was approximately 10% by weight of the total resin mass.

[0057] 2. Test methods (1) Viscosity test: The viscosity of the sample was measured using the MCR 502 modular intelligent advanced rheometer from Anton Paar. The experiment used a cone-plate measuring fixture (geometric parameters: diameter Φ25±0.01 mm, cone angle 2°±0.1°), and the cone-plate-base plate gap was calibrated to (104±1) μm using a laser positioning system. In the closed-loop temperature control mode, the isothermal condition of (25.0±0.1)°C was maintained, and the steady-state shear sweep mode was used with 12 logarithmic gradient segments covering a shear rate window of three orders of magnitude (10 -2 ~10 2 s -1 For accuracy, each sample was measured three times and the average value was taken.

[0058] (2) Plastic tensile properties test: The tensile properties test was performed using a Shimadzu AGS-X 1 kN universal tester. The dumbbell-shaped sample specifications were based on GB / T 1040.2-2006, and the crosshead speed was 1 mm min. -1Young's modulus is the ratio of tensile strength to elongation at break. For accuracy, three measurements were performed on each sample and the average value was taken.

[0059] (3) Dynamic thermomechanical properties test: A Netzsch DMA 242E dynamic thermomechanical instrument was used, with the tensile mode selected and the oscillation frequency set to 1 Hz. During the test, the sample was first cooled to -80°C with liquid nitrogen and kept at -50°C for 3 minutes, then heated at 5°C / min. -1 The sample was heated to 180°C at a rate of 100°C. The sample size was 32 mm × 5 mm × 3 mm (length × width × thickness). The glass transition temperature (T g ) corresponds to the peak temperature on the tanδ vs. temperature curve. For accuracy, three measurements were performed on each sample and the average value was taken.

[0060] (4) Thermogravimetric test: The following thermogravimetric analysis test was performed using a Netzsch STA 449C thermal analyzer. The temperature range required for the thermogravimetric test of the sample was set to 35-650°C, and the heating rate was 10°C·min -1 During the test, the nitrogen environment was maintained and the nitrogen introduction rate was 60 mL min -1 For the sake of accuracy, three measurements were performed on each sample and the average value was taken.

[0061] The viscosity test results of the resin system are as follows: Figure 6 As shown. Figure 6 It can be seen that the viscosity of the cardanol-rosin bio-based epoxy resin of the present invention decreases from 3073 mPa·s to 1123 mPa·s as the ratio of CAMP to AAR changes. This shows that CAMP can effectively reduce the viscosity of the resin system. This can be explained by the fact that CAMP has a certain surface activity and can be distributed on the liquid surface or phase interface in the resin system. In the resin system, the presence of surface tension will have a certain hindering effect on the flow of the fluid, and the addition of CAMP can reduce the surface tension of the system. When the surface tension is reduced, the surface resistance that the resin system needs to overcome during the flow process is reduced, thereby enhancing the fluidity of the entire system and reducing the viscosity.

[0062] Table 1 shows the comprehensive mechanical properties of each heat-cured film after plastic tensile testing. As can be seen from Table 1, the toughness of the cardanol-rosin bio-based epoxy resin of the present invention gradually increases with the addition of CAMP. This is because the long CAMP chains facilitate the sliding of the resin molecular segments, absorbing impact energy and slowing crack propagation, significantly improving the elongation at break of the cured film. However, the excessive introduction of long carbon chains results in a certain decrease in tensile strength.

[0063] Table 1 Comprehensive mechanical properties of thermally cured films Tensile strength (MPa) Elongation at break (%) Elastic modulus (MPa) Comparative Example 1 27.56±0.31 29.67±0.23 92.89±3.92 Example 1 21.73±0.42 32.96±0.45 65.93±4.79 Example 2 14.45±0.16 40.49±0.44 35.69±5.81 Example 3 11.31±0.27 45.64±0.41 24.78±3.16 Comparative Example 2 11.12±0.52 54.24±0.38 20.50±2.89 The thermal stability of each heat-cured film was tested by thermogravimetric method, and the results are shown in Table 2. As can be seen from Table 2, the decomposition stage of the cardanol-rosin bio-based epoxy resin of the present invention at 320°C to 470°C is mainly the thermal decomposition of ester bonds and aromatic structures. 50% The thermal degradation temperature remained essentially unchanged, primarily concentrated between 340-400°C. The carbon residue rate increased with increasing CAMP content, as the methylene group in the CAMP side chain reduces product release. Furthermore, the cured film samples from Examples 1-3 all exhibited relatively high thermal degradation temperatures (360-378°C), demonstrating the excellent thermal stability of the coatings prepared from the cardanol-rosin bio-based epoxy resin.

[0064] Table 2 Thermal stability results of heat-cured films

[0065] The dynamic thermomechanical properties of each heat-cured film were tested, and the results of its thermomechanical properties are shown in Table 3. With the addition of CAMP, that is, the mass ratio of CAMP to AAR in the resin system decreases, the E' 25 and T g The possible reason is that as the proportion of CAMP increases, its long chains may hinder the formation of cross-linking points, resulting in a decrease in cross-linking density. g At the same time, the long chain of CAMP increases the toughness of the heat-cured film, which increases the loss factor peak. On the contrary, a high proportion of AAR in the resin system may increase the crosslinking density, making T g The modulus is higher in the low temperature zone, but the modulus decreases slowly at high temperature due to the close cross-linking. And with the increase of CAMP content, the ν e The initial increase followed by a decrease can be explained by the structures of CAMP and AAR. As the amount of CAMP increases, on the one hand, the long alkyl chain of CAMP creates a steric hindrance, reducing the crosslink density, while its flexible segments enhance the toughness of the cured film. On the other hand, AAR provides rigid structural units, and the high reactivity of the carboxylic acid and epoxy groups promotes the formation of a crosslinked network, increasing the crosslink density. Therefore, when AAR and CAMP reach a certain appropriate ratio, the resin system achieves a structure that is both rigid and flexible, and at this point, the crosslink density reaches its highest level.

[0066] Table 3 Thermal stability results of heat-cured films

[0067] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the inventive concept of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. Cardanol-rosin bio-based epoxy resin, characterized in that The raw materials include, by weight, 100-300 parts of cardanol, 700-900 parts of mercaptopropionic acid, 150-200 parts of cardanol glycidyl ether, 20-60 parts of m-chloroperbenzoic acid, 100-300 parts of glycidyl ether, 0.6-1.5 parts of a catalyst, 0.3-1.5 parts of a polymerization inhibitor and 5-30 parts of acrylic rosin.

2. The cardanol-rosin bio-based epoxy resin according to claim 1, characterized in that The glycidyl ether is selected from at least one of glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol triglycidyl ether, and pentaerythritol triglycidyl ether.

3. The cardanol-rosin bio-based epoxy resin according to claim 1, characterized in that The catalyst is selected from at least one of benzyltriethylammonium chloride, dibutyltin dilaurate, triethylamine, benzyldiamine, and triphenylphosphine.

4. The cardanol-rosin bio-based epoxy resin according to claim 1, characterized in that The polymerization inhibitor is selected from at least one of hydroquinone, p-tert-butylcatechol and catechol.

5. The method for preparing the cardanol-rosin bio-based epoxy resin according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) performing a photo-click reaction between cardanol and mercaptopropionic acid to obtain cardanol mercapto acid; (2) mixing cardanol glycidyl ether with m-chloroperbenzoic acid to carry out epoxidation reaction to obtain epoxy cardanol glycidyl ether; (3) Under the action of a catalyst and a polymerization inhibitor, the cardanol mercapto acid and the acrylic rosin are subjected to an esterification reaction with glycidyl ether, and finally epoxy cardanol glycidyl ether is added to obtain a cardanol-rosin bio-based epoxy resin.

6. The preparation method according to claim 5, characterized in that In step (2), the cardanol glycidyl ether and the m-chloroperbenzoic acid are mixed, and then sodium carbonate is added to the mixed system; the amount of sodium carbonate used is 10-30 parts by weight.

7. The preparation method according to claim 5, characterized in that In step (3), the amount of the cardanol mercapto acid is 10-50 parts by weight; the amount of the epoxy cardanol glycidyl ether is 100-200 parts by weight.

8. The preparation method according to claim 5, characterized in that In step (3), under the action of a catalyst and a polymerization inhibitor, the glycidyl ether and acrylic rosin are first subjected to an esterification reaction, and then the cardanol mercapto acid is added to continue the reaction.

9. The preparation method according to claim 5, characterized in that In step (3), the amount of the catalyst is 0.4-2.0wt% of the total mass of glycidyl ether, cardanol mercapto acid and acrylic rosin; the amount of the polymerization inhibitor is 0.015-0.05wt% of the total mass of glycidyl ether, cardanol mercapto acid and acrylic rosin.

10. Use of the cardanol-rosin bio-based epoxy resin according to any one of claims 1 to 4 in the preparation of adhesives and packaging materials.

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