Hybrid carbon dioxide-based non-isocyanate polyurethane bamboo wood adhesive as well as preparation method and application thereof

Abstract

The invention discloses a hybrid carbon dioxide-based non-isocyanate polyurethane bamboo wood adhesive as well as a preparation method and application thereof. The method comprises the following steps: reacting cardanol-based diglycidyl ether, CO2 and a catalyst to obtain cardanol-based cyclic carbonate; the preparation method comprises the following steps: synthesizing cardanol-based cyclic carbonate and biomass oil-based diamine into cardanol-based non-isocyanate polyurethane of which the end group is a primary amine group; reacting the micromolecular lignin with epichlorohydrin to obtain lignin-based epoxy resin; and reacting the lignin-based epoxy resin with the cardanol-based non-isocyanate polyurethane to obtain the lignin-based epoxy resin hybridized cardanol-based non-isocyanate polyurethane adhesive. The preparation method comprises the following steps: synthesizing cardanol-based non-isocyanate polyurethane by taking biomass cardanol-based diglycidyl ether, CO2 and biomass diamine as raw materials; the lignin is epoxidized and grafted to a primary amine-terminated group of non-isocyanate polyurethane under the conditions of no catalyst and no solvent to obtain the non-isocyanate polyurethane adhesive with excellent mechanical properties.

Description

Technical Field

[0001] This invention relates to bamboo and wood adhesives, specifically to a method for synthesizing a lignin-based epoxy resin hybrid cashew phenol-based non-isocyanate polyurethane adhesive using cashew phenol derivatives, CO2, biomass diamine, and lignin, and its application. Background Technology

[0002] In recent years, formaldehyde-based adhesives have been widely used in the bamboo and wood-based panel industry due to their high bonding strength. However, their high formaldehyde release has been a major concern and will significantly limit their future development. Polyurethane (PU) adhesives, on the other hand, are widely used in structural glued laminated timber and wood-bamboo coatings due to their advantages such as no formaldehyde release, high bonding strength, and excellent water and weather resistance. Most commonly used PU adhesives are synthesized using organic solvents or water as solvents, from petroleum-derived polyols and highly toxic isocyanate compounds through prolonged high-temperature reactions. These pose potential threats to the environment and human health, and are a long-standing technical bottleneck and common scientific problem hindering their widespread application in the wood and bamboo processing industry.

[0003] Non-isocyanate polyurethanes (NIPUs) are primarily synthesized from cyclic carbonates and amines via addition polymerization. This synthetic method not only avoids the use of isocyanates but also, compared to traditional polyurethanes, produces polyurethane chains with a large number of hydroxyl groups. These hydroxyl groups can form intramolecular and intermolecular hydrogen bonds with urethane bonds, enhancing chemical resistance to nonpolar solvents. However, NIPU adhesives have not yet been utilized in the wood adhesive industry. Furthermore, NIPUs can be synthesized using greenhouse gas CO2 and biomass-based materials, reducing dependence on petroleum-based resources and providing technical support for the rational conversion of biomass materials and CO2. Currently, commonly used biomass materials include vegetable oils, terpenoids, rosin compounds, and agricultural waste, for which the theories and technologies are relatively mature. However, other biomass materials are less explored. Therefore, finding suitable biomass materials to synthesize novel CO2-based cyclic carbonates is an urgent problem to be solved in the development of green NIPUs. Cashew nut phenol, a natural phenolic compound, possesses a unique chemical structure that endows it and its derivatives with excellent high-temperature resistance and good toughness. Furthermore, cashew nut phenol exhibits special chemical properties, enabling it to undergo various polymerization reactions, such as hydroxyaldehyde condensation, esterification, and oxidation. These characteristics provide inherent advantages for the synthesis of multifunctional, high-performance polyurethane adhesives. However, research on the synthesis of cashew nut phenol and its derivatives in CO2-based cyclic carbonates is currently scarce. Summary of the Invention

[0004] To address the problems of high formaldehyde release in current bamboo and wood adhesives, the high toxicity of polyurethane adhesives, and their reliance on petroleum-based polyols, this invention provides a method for synthesizing cashew nut shell phenolic diglycidyl ether, CO2, and biomass diamine as raw materials for non-isocyanate polyurethane. Furthermore, to improve its poor mechanical properties, a method is employed to epoxidize lignin and graft it onto the terminal primary amine groups of the non-isocyanate polyurethane under catalyst-free and solvent-free conditions, resulting in a non-isocyanate polyurethane adhesive with excellent mechanical properties. This process is simple, environmentally friendly, and has sustainable development prospects.

[0005] To achieve the above objectives, the present invention provides a method for synthesizing a lignin-based epoxy resin hybrid cashew nut shell phenolic polyurethane adhesive, comprising the following steps: S1. Cashew phenolic diglycidyl ether, CO2 and catalyst are reacted at a temperature of 90-130 ℃ and a pressure of 1-2.5 MPa for 18-24 h to obtain cashew phenolic cyclic carbonate. S2. The cashew phenol-based cyclic carbonate synthesized in step S1 and biomass oil-based diamine are reacted at 25-40℃ for 10-30 min to synthesize cashew phenol-based non-isocyanate polyurethane with primary amine end groups. S3. Reaction of small-molecule lignin with epichlorohydrin at 90-100 °C for 4-5 h. NaOH solution is added dropwise to the mixture under vigorous stirring, and the reaction continues at 90-100 °C for 1-1.5 h. After the reaction is complete, the mixture is cooled to room temperature, and deionized water is introduced to precipitate the epoxy compound. The precipitate is then collected by vacuum filtration and washed to remove residual reaction impurities, yielding lignin-based epoxy resin. S4. The lignin-based epoxy resin synthesized in step S3 and the cashew phenol-based non-isocyanate polyurethane synthesized in step S2 are stirred uniformly at room temperature for 30-60 minutes to obtain a lignin-based epoxy resin hybrid cashew phenol-based non-isocyanate polyurethane adhesive.

[0006] Preferably, in step S1, the catalyst accounts for 0.5%-2% of the mass of cashew phenolic diglycidyl ether.

[0007] Preferably, the molar ratio of cashew phenolic diglycidyl ether to biomass oil-based diamine is (2~7):(2~10). The biomass oil-based diamine is preferably Priamine 1074.

[0008] Specifically, in step S3, the method for obtaining the small molecule lignin is as follows: lignin is dissolved in a solvent, stirred at room temperature for 1-3 hours, and then centrifuged to obtain solid-liquid separated lignin, wherein the lignin dissolved in the organic solvent is the small molecule lignin. The dissolved lignin is then rotary evaporated to obtain small molecule lignin particles. The solvent is ethanol, acetone, N,N dimethylformamide, or dimethyl sulfoxide.

[0009] Preferably, in step S4, the molar ratio of the lignin-based epoxy resin and the cashew phenol-based non-isocyanate polyurethane is (1~3):(1~7).

[0010] A second aspect of the present invention provides a hybrid cashew nut shell phenol-based non-isocyanate polyurethane adhesive synthesized by the above-described synthesis method, having the following structural formula: .

[0011] The third aspect of the present invention provides the application of the above-mentioned hybrid cashew nut phenol-based non-isocyanate polyurethane adhesive in the preparation of bamboo and wood adhesive materials.

[0012] Specifically, the hybrid cashew nut phenol-based non-isocyanate polyurethane adhesive is uniformly applied to the wood or bamboo veneer and then hot-pressed.

[0013] More specifically, the adhesive application rate is 140-240 g / m². 2 The hot pressing pressure is 1.5-2 MPa, the hot pressing time is 3-15 min, and the hot pressing temperature is 110-140 ℃.

[0014] Preferably, the wood or bamboo veneer is made of poplar, linden, or bamboo strips, with a thickness of 1.5-2.5 mm.

[0015] Through the above technical solution, the present invention achieves the following beneficial effects: This invention is the first to introduce cashew phenol-based diglycidyl ether and the catalyst triethylbenzylammonium chloride into a high-pressure reactor and allow CO2 to be introduced for a complete reaction at high temperature to obtain cashew phenol-based cyclic carbonate. The obtained cashew phenol-based cyclic carbonate and biomass oil-based diamine (Priamine 1074) are then rapidly synthesized at room temperature without a catalyst or solvent to produce a non-isocyanate polyurethane. By separating lignin by dissolving it in a polar solvent, it can still react with epichlorohydrin under solvent-free conditions to synthesize a lignin-based epoxy resin. This lignin-based epoxy resin is then grafted onto the cashew phenol-based non-isocyanate polyurethane to construct an adhesive with a high-mechanical-strength cross-linked network structure, which is applied for the first time in the field of wood adhesives. This process not only avoids the use of highly toxic isocyanates but also utilizes the greenhouse gas CO2 and various biomass materials for synthesis, avoiding the use of petroleum-based derivatives and providing technical support for the high-value utilization of CO2. On the one hand, it can vigorously develop a green and low-carbon economy and promote the green transformation of the industrial and energy structures of polyurethane. On the other hand, it can also provide ideas and references for the green development of bamboo and wood adhesives. Attached Figure Description

[0016] Figure 1 A roadmap for the synthesis of cashew phenolic cyclic carbonate in step 1; Figure 2 The 1H NMR spectrum of the cashew phenolic cyclic carbonate synthesized in step 1; Figure 3 To implement the chemical formula of cashew phenol-based non-isocyanate polyurethane in 1; Figure 4 Infrared spectrum of the cashew phenol-based non-isocyanate polyurethane synthesized in step 1; Figure 5 Infrared images of lignin before and after ethanol separation and epoxidation in Exercise 1; Figure 6 Infrared images of the lignin-based epoxy resin hybrid cashew phenol-based non-isocyanate polyurethane adhesive before and after curing in Implementation 1. Figure 7 To determine the bonding strength of poplar veneer with the lignin-based epoxy resin hybrid cashew phenolic non-isocyanate polyurethane adhesives in sections 1-4. Detailed Implementation

[0017] The specific embodiments of the present invention will be described in detail below with reference to examples. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0018] Example 1 like Figure 1As shown, cashew phenolic diglycidyl ether was used as a raw material to synthesize cashew phenolic cyclic carbonate under the catalysis of triethylbenzylammonium chloride. The catalyst accounted for 1% of the mass of cashew phenolic diglycidyl ether, the CO2 pressure was 2 MPa, the reaction temperature was 110 °C, and the reaction time was 20 h. NMR data of the synthesized cashew phenolic cyclic carbonate were obtained as follows: Figure 2 As shown, the disappearance of the peak intensity of the epoxy group at 2.90-3.40 ppm and the appearance of the peak of the cyclic carbonate at 4.6 ppm indicate that cashew phenolic diglycidyl ether reacted successfully with CO2.

[0019] The cashew phenol-based cyclic carbonate obtained above and oleyl diamine Priamine 1074 were reacted at 30 °C for 10 minutes in a 2:5 ratio to obtain a cashew phenol-based non-isocyanate polyurethane with terminal primary amine groups, the chemical formula of which is as follows: Figure 3 As shown. Infrared spectroscopy was performed on the synthesized cashew phenol-based non-isocyanate polyurethane, and the resulting infrared spectrum is shown below. Figure 4 As shown. The ring-opening reaction of cashew phenolic cyclic carbonate resulted in a 1795 cm⁻¹. −1 The disappearance of the C=O absorption peak is accompanied by the appearance of the NIPU characteristic peak. (1710 cm⁻¹) -1 and 1545 cm -1 The new absorption peak at 3363 cm⁻¹ belongs to the C=O stretching vibration peak and the NH stretching vibration peak in urethane esters. -1 The absorption peak at [location] corresponds to the bending vibration of the -OH group in cashew phenol-based non-isocyanate polyurethane. These results indicate the successful synthesis of cashew phenol-based non-isocyanate polyurethane.

[0020] 100 g of enzymatically hydrolyzed lignin was dissolved in 1000 mL of anhydrous ethanol and stirred at room temperature for 1 hour. The mixture was then centrifuged to separate small-molecule lignin dissolved in ethanol from undissolved large-molecule lignin. The small-molecule lignin dissolved in ethanol was then rotary evaporated to obtain solid particles. Infrared spectra of the lignin before and after separation, as well as before and after epoxidation, were analyzed. Figure 5 As shown, no significant changes were observed in the functional groups of lignin after ethanolification, indicating that the structure of lignin did not change significantly during ethanol purification. After lignin epoxidation, a significant reduction in the hydroxyl peak was observed. Furthermore, at 905 cm⁻¹... -1 The presence of a characteristic peak of epoxy groups indicates that the epoxidation reaction of lignin has been successfully carried out.

[0021] 10 g of lignin purified from ethanol was added to a three-necked flask containing 60 g epichlorohydrin, 0.1 g tetramethylammonium chloride, and 0.1 g H₂O. The reaction system was continuously stirred at 100 °C for 4 hours. After the phase transfer reaction began, 4.3 g of 20 wt% NaOH aqueous solution was added dropwise to the mixture under vigorous stirring, and the reaction was continued at 100 °C for 1 hour to complete the ring-closing reaction. Once the reaction was complete, the mixture was cooled to room temperature, and deionized water was introduced to precipitate the epoxy compound. The precipitate was then collected by vacuum filtration and washed multiple times with deionized water to remove residual reaction impurities, including sodium hydroxide, sodium chloride, TMAC, and any unreacted epichlorohydrin. Subsequently, the purified product was freeze-dried to obtain a yellow lignin-based epoxy resin.

[0022] The synthesized lignin-based epoxy resin and cashew nut phenol-based non-isocyanate polyurethane were mixed in a 3:2 ratio and stirred uniformly at 30°C for 30 minutes to obtain a lignin-based epoxy resin hybrid cashew nut phenol-based non-isocyanate polyurethane adhesive, designated as Sample 1. The infrared spectra of the lignin-based epoxy resin hybrid cashew nut phenol-based non-isocyanate polyurethane before and after curing were analyzed. Figure 6 It can be seen that as the reaction proceeds, at 905 cm -1 The epoxy groups at the site were largely consumed by the amino groups of the cashew phenol-based non-isocyanate polyurethane, indicating the successful synthesis of lignin-based epoxy resin hybrid cashew phenol-based non-isocyanate polyurethane.

[0023] The synthesized adhesive was applied to a 2 mm thick poplar veneer, with two layers of poplar veneer overlapping. The adhesive application rate was 190 g / m². 2 The hot pressing time is 15 minutes, the hot pressing temperature is 140℃, and the hot pressing pressure is 1.5 MPa.

[0024] Example 2 Cashew phenolic diglycidyl ether was used as a raw material to synthesize cashew phenolic cyclic carbonates under the catalysis of triethylbenzylammonium chloride. The catalyst accounted for 0.5% of the mass of cashew phenolic diglycidyl ether, the CO2 pressure was 1 MPa, the reaction temperature was 130 °C, and the reaction time was 18 h.

[0025] The cashew phenolic cyclic carbonate obtained above and the oleo-based diamine Priamine 1074 were reacted at 25°C for 30 minutes in a 1:2 ratio to obtain a cashew phenolic non-isocyanate polyurethane with terminal primary amine groups.

[0026] 200 g of enzymatically hydrolyzed lignin was dissolved in 1000 mL of N,N dimethylformamide and stirred at room temperature for 3 hours. The mixture was then centrifuged to separate small-molecule lignin dissolved in ethanol from undissolved large-molecule lignin. The small-molecule lignin dissolved in ethanol was then rotary evaporated to obtain lignin particles.

[0027] 10 g of lignin purified from ethanol was added to a three-necked flask containing 60 g epichlorohydrin, 0.1 g tetramethylammonium chloride, and 0.1 g H₂O. The reaction system was continuously stirred at 90 °C for 5 hours. After the phase transfer reaction began, 4.3 g of 20 wt% NaOH aqueous solution was added dropwise to the mixture under vigorous stirring, and the reaction was continued at 90 °C for 1.5 hours to complete the ring-closure reaction. Once the reaction was complete, the mixture was cooled to room temperature, and deionized water was introduced to precipitate the epoxy compound. The precipitate was then collected by vacuum filtration and washed multiple times with deionized water to remove residual reaction impurities, including sodium hydroxide, sodium chloride, TMAC, and any unreacted epichlorohydrin. Subsequently, the purified product was freeze-dried to obtain a yellow lignin-based epoxy resin.

[0028] The lignin-based epoxy resin and cashew phenol-based non-isocyanate polyurethane synthesized above were stirred uniformly at 30°C for 30 minutes in a 1:1 ratio to obtain a lignin-based epoxy resin hybrid cashew phenol-based non-isocyanate polyurethane adhesive, which was designated as Sample 2.

[0029] The synthesized adhesive was applied to a 2mm thick poplar veneer, with two layers of poplar veneer overlapping. The adhesive application rate was 140 g / m². 2 The hot pressing time is 3 minutes, the hot pressing temperature is 110℃, and the hot pressing pressure is 2 MPa.

[0030] Example 3 Cashew phenolic diglycidyl ether was used as a raw material to synthesize cashew phenolic cyclic carbonates under the catalysis of triethylbenzylammonium chloride. The catalyst accounted for 2% of the mass of cashew phenolic diglycidyl ether, the CO2 pressure was 2.5 MPa, the reaction temperature was 90 °C, and the reaction time was 24 h.

[0031] The cashew phenolic cyclic carbonate obtained above and the oleo-based diamine Priamine 1074 were reacted at 40°C for 15 minutes in a 3:5 ratio to obtain a cashew phenolic non-isocyanate polyurethane with terminal primary amine groups.

[0032] 150 g of enzymatically hydrolyzed lignin was dissolved in 1000 mL of dimethyl sulfoxide and stirred at room temperature for 2 hours. The mixture was then centrifuged to separate small-molecule lignin dissolved in ethanol from undissolved large-molecule lignin. The small-molecule lignin dissolved in ethanol was then rotary evaporated to obtain lignin particles.

[0033] 10 g of lignin purified from ethanol was added to a three-necked flask containing 60 g epichlorohydrin, 0.1 g tetramethylammonium chloride, and 0.1 g H₂O. The reaction system was continuously stirred at 100 °C for 4 hours. After the phase transfer reaction began, 4.3 g of 20 wt% NaOH aqueous solution was added dropwise to the mixture under vigorous stirring, and the reaction was continued at 100 °C for 1 hour to complete the cyclization reaction. Once the reaction was complete, the mixture was cooled to room temperature, and deionized water was introduced to precipitate the epoxy compound. The precipitate was then collected by vacuum filtration and washed multiple times with deionized water to remove residual reaction impurities, including sodium hydroxide, sodium chloride, TMAC, and any unreacted epichlorohydrin. Subsequently, the purified product was freeze-dried to obtain a yellow lignin-based epoxy resin.

[0034] The lignin-based epoxy resin and cashew phenol-based non-isocyanate polyurethane synthesized above were stirred uniformly at 30°C for 30 minutes in a 2:3 ratio to obtain a lignin-based epoxy resin hybrid cashew phenol-based non-isocyanate polyurethane adhesive, which was designated as Sample 3.

[0035] The synthesized adhesive was applied to a 2 mm thick poplar veneer, with two layers of poplar veneer overlapping. The adhesive application rate was 200 g / m². 2 The hot pressing time is 10 minutes, the hot pressing temperature is 120℃, and the hot pressing pressure is 1.5 MPa.

[0036] Example 4 Cashew phenolic diglycidyl ether was used as a raw material to synthesize cashew phenolic cyclic carbonate under the catalysis of triethylbenzylammonium chloride. The catalyst accounted for 1.5% of the mass of cashew phenolic diglycidyl ether, the CO2 pressure was 2 MPa, the reaction temperature was 100 °C, and the reaction time was 20 h.

[0037] The cashew phenolic cyclic carbonate obtained above and oleo-based diamine Priamine 1074 were reacted at 35°C for 20 minutes in a ratio of 7:10 to obtain a cashew phenolic non-isocyanate polyurethane with terminal primary amine groups, denoted as NIPU-4.

[0038] 100 g of enzymatically hydrolyzed lignin was dissolved in 1000 mL of anhydrous ethanol, and after stirring at room temperature for 1 hour, centrifugation was performed to separate small-molecule lignin dissolved in ethanol and undissolved large-molecule lignin. The small-molecule lignin dissolved in ethanol was then rotary evaporated to obtain lignin particles.

[0039] 10 g of lignin purified from ethanol was added to a three-necked flask containing 60 g epichlorohydrin, 0.1 g tetramethylammonium chloride, and 0.1 g H₂O. The reaction system was continuously stirred at 100 °C for 4 hours. After the phase transfer reaction began, 4.3 g of 20 wt% NaOH aqueous solution was added dropwise to the mixture under vigorous stirring, and the reaction was continued at 100 °C for 1 hour to complete the cyclization reaction. Once the reaction was complete, the mixture was cooled to room temperature, and deionized water was introduced to precipitate the epoxy compound. The precipitate was then collected by vacuum filtration and washed multiple times with deionized water to remove residual reaction impurities, including sodium hydroxide, sodium chloride, TMAC, and any unreacted epichlorohydrin. Subsequently, the purified product was freeze-dried to obtain a yellow lignin-based epoxy resin.

[0040] The lignin-based epoxy resin and cashew phenol-based non-isocyanate polyurethane synthesized above were stirred uniformly at 30°C for 60 minutes in a ratio of 3:7 to obtain a lignin-based epoxy resin hybrid cashew phenol-based non-isocyanate polyurethane adhesive, which was designated as sample 4.

[0041] The synthesized adhesive was applied to a 2 mm thick poplar veneer, with two layers of poplar veneer overlapping. The adhesive application rate was 240 g / m². 2 The hot pressing time is 15 minutes, the hot pressing temperature is 140℃, and the hot pressing pressure is 1.5 MPa.

[0042] Example of effect The bonding strength of the lignin-based epoxy resin hybrid cashew nut shell phenolic polyurethane adhesives prepared in Examples 1-4 to poplar veneer was tested. The bonding strength was determined according to the national standard GB / T 17657-2013. The test results are as follows. Figure 7 As shown in the figure, the wet bond strength of sample 1 can reach 2.31 MPa.

[0043] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0044] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0045] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for synthesizing a lignin-based epoxy resin hybrid cashew phenol-based non-isocyanate polyurethane adhesive, characterized in that, Includes the following steps: S1. Cashew phenolic diglycidyl ether, CO2 and catalyst are reacted at a temperature of 90-130 ℃ and a pressure of 1-2.5 MPa for 18-24 h to obtain cashew phenolic cyclic carbonate. S2. The cashew phenol-based cyclic carbonate synthesized in step S1 and biomass oil-based diamine are reacted at 25-40℃ for 10-30 min to synthesize cashew phenol-based non-isocyanate polyurethane with primary amine end groups. S3. React small molecule lignin with epichlorohydrin at 90-100 °C for 4-5 h, add NaOH solution dropwise to the mixture under vigorous stirring, and continue the reaction at 90-100 °C for 1-1.5 h to obtain lignin-based epoxy resin. S4. The lignin-based epoxy resin synthesized in step S3 and the cashew phenol-based non-isocyanate polyurethane synthesized in step S2 are stirred uniformly at room temperature for 30-60 minutes to obtain a lignin-based epoxy resin hybrid cashew phenol-based non-isocyanate polyurethane adhesive.

2. The synthesis method according to claim 1, characterized in that, In step S1, the catalyst accounts for 0.5%-2% of the mass of cashew phenolic diglycidyl ether.

3. The synthesis method according to claim 1, characterized in that, The molar ratio of cashew phenol-based diglycidyl ether to biomass oil-based diamine is (2~7):(2~10).

4. The synthesis method according to claim 1, characterized in that, In step S3, the method for obtaining the small molecule lignin is as follows: dissolve lignin in a solvent, stir at room temperature for 1-3 hours, and then centrifuge to obtain solid-liquid separated lignin, wherein the lignin dissolved in the organic solvent is small molecule lignin, and then rotary evaporate the dissolved lignin to obtain small molecule lignin particles.

5. The synthesis method according to claim 1, characterized in that, In step S4, the molar ratio of the lignin-based epoxy resin and the cashew phenol-based non-isocyanate polyurethane is (1~3):(1~7).

6. The hybrid cashew nut phenol-based non-isocyanate polyurethane adhesive synthesized by the synthesis method according to any one of claims 1 to 5, characterized in that, It has the following structural formula: 。 7. The application of the hybrid cashew phenol-based non-isocyanate polyurethane adhesive of claim 6 in the preparation of bamboo and wood adhesive materials.

8. The application according to claim 7, characterized in that, The hybrid cashew phenol-based non-isocyanate polyurethane adhesive is uniformly applied to the wood and bamboo veneer and then hot-pressed.

9. The application according to claim 8, characterized in that, The application rate of the adhesive is 140-240 g / m². 2 The hot pressing pressure is 1.5-2 MPa, the hot pressing time is 3-15 min, and the hot pressing temperature is 110-140 ℃.

10. The application according to claim 7, characterized in that, The wood and bamboo veneer is made of poplar, linden, or bamboo strips, with a thickness of 1.5-2.5 mm.

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