A production process for ENF-grade impregnated film paper veneer plywood

Abstract

The present invention relates to a production process for ENF-grade impregnated film paper facing plywood, which includes the synthesis of a low-melting ionic liquid, purification of lignin, catalytic degradation and purification of lignin using the low-melting ionic liquid, preparation of a MUF co-condensation resin, preparation of a lignin-based adhesive, preparation of dopa-methacrylamide (DMA), preparation of a CNF / P (HEMA-co-DMA) adhesive, and preparation of an antibacterial and mildew-proof agent-impregnated film paper facing plywood. The present invention innovatively combines catalytic degradation activation technology, a free radical polymerization method, and an alkaline catalysis method to prepare a material having the advantages of good mechanical and water resistance, high bonding strength, and lower formaldehyde emission.

Description

Technical Field

[0001] The invention relates to a production process of ENF-grade impregnated film paper veneer plywood. Background Art

[0002] As consumer values ​​of environmental protection, energy conservation, and health gain increasing popularity, healthy, safe, and green building and home improvement materials will become a new consumer trend. Impregnated paper-faced plywood is a new type of environmentally friendly decorative panel. Its unique solid wood feel, excellent structural stability, low formaldehyde emissions, and aesthetically pleasing decorative effects, along with its surface resistance to discoloration and peeling, and ease of processing, meet consumers' demand for high-quality home furnishings. It has been widely used in panel furniture and holds a promising market. However, current research on the functionalities of impregnated paper-faced plywood focuses primarily on flame retardancy and formaldehyde emission reduction, and its performance research is still in its early stages.

[0003] The multi-layer hot presses used in plywood production suffer from uneven heating temperatures on the hot press platens, which directly impacts the mechanical properties and quality of the finished plywood. To address the formaldehyde pollution caused by the extensive use of urea-formaldehyde resin, improving urea-formaldehyde resin production processes and microstructure, and producing environmentally friendly urea-formaldehyde resin adhesives with low free formaldehyde content and low formaldehyde-emission wood-based panels have become the focus of numerous researchers and manufacturers both domestically and internationally. my country began developing and promoting low-toxicity urea-formaldehyde resins in the late 1970s. However, urea-formaldehyde resins used in the wood-based panel industry still suffer from high free formaldehyde content, resulting in reduced physical and chemical properties such as bonding strength after modification. Summary of the Invention

[0004] The present invention provides a production process for ENF-grade impregnated film paper veneer plywood, comprising the following steps: synthesis of a low-melting ionic liquid, purification of lignin, catalytic degradation and purification of lignin by using the low-melting ionic liquid, preparation of a multi-component co-condensation modified uric acid resin, preparation of a lignin-based adhesive, preparation of dopamethyl acrylamide (DMA), preparation of a CNF / P (HEMA-co-DMA) adhesive, liquefaction of bamboo powder, synthesis of a liquefied bamboo phenolic resin, and preparation of an antibacterial and mildew-proof agent-impregnated film paper veneer plywood.

[0005] Preferably, step (1) the synthesis of the eutectic ionic liquid

[0006] First, dry Urea and ZnCl2, mix them in proportion and place them in a conical flask. After the reaction melts, stir them magnetically until they become a colorless and transparent liquid.

[0007] Step (2) Purification of lignin

[0008] Industrial alkali lignin is dissolved in water to form a solution of a certain concentration, stirred evenly with a stirrer, and a NaOH solution of an appropriate concentration is added to adjust the pH to a certain range. The solution is stirred continuously until the alkali lignin is completely dissolved. The alkali lignin solution is then centrifuged in a centrifuge, and the precipitate is discarded after centrifugation to obtain a supernatant. Concentrated sulfuric acid is added to the supernatant to adjust the pH to a certain value. The solution is centrifuged again, and the supernatant is discarded after centrifugation to obtain a precipitate. The precipitate is washed with dilute acid adjusted to a certain pH value, stirred evenly, and centrifuged in a centrifuge to obtain a precipitate. The precipitate is placed in an enamel dish and dried in a water bath at a certain temperature. After the surface moisture is completely evaporated, the precipitate is placed in a vacuum drying oven at a certain temperature to obtain chemically purified lignin.

[0009] Step (3) Urea / ZnCl2 eutectic ionic liquid catalyzes the degradation and purification of alkali lignin

[0010] According to different solid-liquid ratios, the purified lignin prepared in step (2) is added to the two Urea / ZnCl2 low eutectic ionic liquids prepared in step (1), and the reaction is carried out for different times under temperature conditions. After the reaction, the lignin is purified by an industrial alkaline lignin purification method, and the obtained product is the lignin activated by the Urea / ZnCl2 low eutectic ionic liquid;

[0011] Step (4) Preparation of MUF cocondensation resin

[0012] The formaldehyde solution is added to a three-necked flask at once, the pH value is adjusted with sodium hydroxide, and the mixture is stirred and heated to a certain temperature, then kept warm. The pH value of the reaction system is adjusted, and the state of the resin in water at a fixed temperature is measured during the reaction. When the resin becomes cloudy, the pH value is adjusted, and M (melamine) is added. The amount of M is an appropriate percentage of the urea quality, and the reaction is continued at a certain temperature. When the resin is dropped into water and turbidity appears, urea is added, and the reaction is continued at an appropriate temperature. When the resin forms a flocculent precipitate, the temperature is lowered and the pH value is adjusted again to synthesize a MUF (formaldehyde-melamine-urea) co-condensation resin.

[0013] Step (5) Preparation of lignin-based adhesive

[0014] First, polyethylene glycol and concentrated sulfuric acid are uniformly mixed under magnetic stirring conditions, and then the activated lignin in step (3) and the mixed solution are placed in a three-necked flask; after the two are uniformly mixed, the three-necked flask containing polyethylene glycol and activated lignin is placed in a pre-heated oil bath pot for cooking; when the cooking is completed, the oil bath pot is immediately removed, and the three-necked flask is placed in cold water to quickly lower the temperature to terminate the reaction in the three-necked flask; the dioxane solution is poured into the mixture after the reaction to dissolve the reaction product, and all the reaction products are transferred from the three-necked flask to a funnel for filtration to separate and remove the solution that does not participate in the reaction The corresponding residue is washed several times with a dioxane solution to ensure that all the liquefied product is dissolved in the solution; the liquefied solution obtained after filtration is evaporated using a rotary evaporator under certain temperature conditions to remove water and dioxane in the solution to obtain a liquefied product; the evaporated liquefied product is then poured into a certain amount of distilled water and magnetically stirred to separate free polyethylene glycol from the liquefied product and dissolve it in the distilled water to separate it from the obtained precipitate; the stirred mixture is then centrifuged to separate the solution and the precipitate; and finally the precipitate is taken out and vacuum dried to obtain a lignin-based adhesive.

[0015] Step (6) Preparation of protected dopamethacrylamide (DMA)

[0016] DOPA (dopamine hydrochloride) is weighed and added to a three-necked flask containing CH2Cl2. Stirring is performed at room temperature to completely disperse the mixture. TEA is then added, followed by dropwise addition of triethylsilane and TEA (triethylamine) using a constant-pressure separatory funnel. The mixture is allowed to react at room temperature for a period of time. Finally, methacryloyl chloride and TEA are added dropwise using a constant-pressure separatory funnel. The mixture is allowed to react at room temperature. After the reaction, CH2Cl2 is evaporated to dryness using a rotary evaporator, extracted with ethyl acetate, and unreacted materials are removed with a NaHSO4 solution. The organic layer is washed with a saturated NaCl solution, dried with Na2SO4, and finally concentrated using a rotary evaporator. The protected DMA is purified by column chromatography using a n-hexane / ethyl acetate mixture as the eluent, ultimately yielding a colorless, highly viscous liquid.

[0017] Step (7) Preparation of CNF / P(HEMA-co-DMA) adhesive

[0018] The protected DMA, HEMA (hydroxyethyl methacrylate) and AIBN obtained in step (6) were weighed and added to a round-bottom flask containing ethanol. After a freeze-thaw cycle, nitrogen was injected into the round-bottom flask. The copolymer was copolymerized at a certain temperature for a certain time, and HCl was used to deprotect the copolymer. The copolymer was then precipitated with ether and filtered. Finally, it was dried under vacuum to obtain a P(HEMA-co-DMA) copolymer. The P(HEMA-co-DMA) copolymer was dissolved in ethanol, and a CNF suspension was added to the P(HEMA-co-DMA) copolymer solution, and the mixture was stirred to obtain a composite adhesive with a CNF concentration.

[0019] Step (8) Preparation of antibacterial and mildew-proof agent impregnated film paper veneer plywood

[0020] The fir core board is made according to the finger-jointing process technology of integrated wood, and then the sanded strips are grooved on both sides, and then hot-pressed and glued with lignin-based adhesive. For the middle board, CNF / P (HEMA-co-DMA) adhesive is used to splice the middle board through a splicing machine to ensure that there is no overlap on the surface after hot-pressing and gluing with the core board. The core board and the middle board are hot-pressed and glued with MUF co-condensation resin, and then repaired by scraping mud. After curing and sanding, the surface is covered with veneer. Finally, the base material that can be used for covering the impregnated film paper is made through processes such as scraping mud, curing, and sanding; finally, the hot pressing process is carried out, and the hot pressing pressure is within a certain range, and hot pressing is carried out after pre-pressing for a period of time; the pre-pressing and hot pressing are repeated until the glue is applied, and the temperature is adjusted within a certain range for the hot pressing time, and the antibacterial and mildew-proof impregnated film paper with the best performance is pressed onto the surface of the base material to obtain the antibacterial and mildew-proof agent impregnated film paper veneered plywood.

[0021] Preferably, step (1) the synthesis of the eutectic ionic liquid

[0022] First, dry Urea (urea) and ZnCl2 (zinc chloride). Place Urea in a vacuum drying oven at 75-85°C and dry for 10-15 hours. Mix Urea and ZnCl2 in a conical flask at a molar fraction of 10-40% of ZnCl2. The mixture is placed in a conical flask at a reaction temperature between 60-100°C. After melting, stir magnetically until it becomes a colorless, transparent liquid.

[0023] The advantage of the present invention is that molten ZnCl2 has good electrical conductivity. When the temperature is too low, the activity is insufficient to react. When the temperature is high, the energy barrier of at least one substance can be broken to enable the melting reaction.

[0024] Preferably, step (2) lignin purification

[0025] Industrial alkali lignin is dissolved in water to form a solution with a concentration of about 10-15%, and the solution is stirred evenly with a stirrer. A 10-15% NaOH solution is added to adjust the pH to about 10-15, and the solution is stirred continuously until the alkali lignin is completely dissolved. The alkali lignin solution is then centrifuged in a centrifuge, the precipitate is discarded, and the supernatant is collected. 10-15% sulfuric acid is added to the supernatant to adjust the pH to below 2-5. The solution is centrifuged again, the supernatant is discarded, and the precipitate is collected. The precipitate is washed with dilute acid with a pH of about 2-5, stirred evenly, and centrifuged in a centrifuge to collect the precipitate. The precipitate is placed in an enamel dish and dried in a water bath at about 40-50°C. After the surface moisture is completely evaporated, the precipitate is placed in a vacuum drying oven at 45-55°C and dried for 12-24 hours to obtain chemically purified lignin.

[0026] As a preference, step (3) Urea / ZnCl2 eutectic ionic liquid catalyzes the degradation and purification of alkali lignin

[0027] According to different solid-liquid ratios (1:20-1:70), the purified lignin prepared in step (2) is added to the two Urea / ZnCl2 low eutectic ionic liquids prepared in step (1), and the reaction is carried out at a temperature of 60-100°C for different times (1H-8H). After the reaction, the lignin is purified by an industrial alkaline lignin purification method, and the obtained product is lignin activated by the Urea / ZnCl2 low eutectic ionic liquid.

[0028] The advantages of the present invention are that the activated lignin increases the reaction active sites, the low-melting ionic liquid has smaller surface tension, density and viscosity, the ion concentration in the system is higher, and the ion mobility is better, so that the number of active ions in the system is increased, thereby promoting the full progress of the reaction.

[0029] Preferably, step (4) preparation of MUF co-condensation resin

[0030] The formaldehyde solution is added to a three-necked flask at once, and the pH is adjusted to 7.0-8.0 with sodium hydroxide. The flask is stirred and heated to 85-90°C over 30-40 minutes, followed by holding for 55-60 minutes. The pH of the reaction system is adjusted to 4.6-4.8. During the reaction, the state of the resin in 15-20°C water is measured. When the resin becomes cloudy, the pH is adjusted to 5.0-9.0, and M (melamine) is added at an amount of 5-15% of the urea quality. The reaction is carried out at 60-85°C for 1-2 hours. When the resin becomes cloudy when dropped into water, urea is added, and the reaction is continued at 75-80°C. When the resin forms a flocculent precipitate, the temperature is lowered and the pH is adjusted to approximately 5.0-8.0, thereby synthesizing a MUF (formaldehyde-melamine-urea) co-condensation resin.

[0031] The advantages of the present invention include reduced methylol content in the MUF cocondensation resin, increased free urea content, and reduced degree of polycondensation. Rational optimization of the molecular structure of the MUF cocondensation resin can fundamentally improve performance. The solids content and curing time of the MUF cocondensation resin both show a certain upward trend, while the free formaldehyde content shows a significant downward trend. The melamine resin can fully flow and melt, forming a wear-resistant and scratch-resistant transparent coating on the surface of the board, thereby exhibiting excellent wear and scratch resistance. Melamine can bind a large amount of formaldehyde, thereby reducing the free formaldehyde content.

[0032] Preferably, step (5) preparation of lignin-based adhesive

[0033] First, polyethylene glycol 350-400 and 1-5% concentrated sulfuric acid are uniformly mixed under magnetic stirring conditions; then the activated lignin in step (3) and the mixed solution are placed in a 900-1000 mL three-necked flask; after the two are uniformly mixed, the three-necked flask containing polyethylene glycol and activated lignin is placed in an oil bath pot heated in advance at a temperature of 100-170°C for steaming for 1-4 hours; when the steaming is completed, the oil bath pot is immediately removed, and the three-necked flask is placed in cold water to quickly lower the temperature to stop the three-necked flask. The reaction is carried out as follows: a 50-100% volume concentration of dioxane solution is poured into the reaction mixture to dissolve the reaction product, and all the reaction products are transferred from the three-necked flask to a funnel for filtration to separate and remove the unreacted residue in the solution, and the residue is washed multiple times with a 50-100% dioxane solution to ensure that all the liquefied products are dissolved in the solution; the liquefied solution obtained after filtration is evaporated using a rotary evaporator at a temperature of 45-50°C to remove water and dioxane from the solution to obtain a liquefied product. The evaporated liquefied product is then poured into a certain amount of distilled water and magnetically stirred for 1-4 hours to separate the free polyethylene glycol from the liquefied product and dissolve it in distilled water to separate it from the resulting precipitate. The stirred mixture is then centrifuged to separate the solution and the precipitate to obtain a lignin-based adhesive.

[0034] The advantages of the present invention are that costs can be reduced and efficient utilization of biomass resources can be achieved. Lignin can partially replace phenol to prepare lignin-modified phenolic resin adhesives because the molecule has active functional groups such as alcoholic hydroxyl groups and phenolic hydroxyl groups, which are similar to the structure of phenolic resin.

[0035] Preferably, step (6) preparation of protected dopa methacrylamide (DMA)

[0036] Weigh 5.0-9.0 g DOPA (dopamine hydrochloride) and add it to a three-necked flask containing 150-200 mL CH2Cl2, stir at room temperature to make it completely dispersed, add 3.0-6.6 mL TEA; then use a constant pressure separatory funnel to add 15.0-17.0 mL triethylsilyl chloride and 10-14.0 mL LTEA dropwise, after the addition is complete, react at room temperature for 1-4 h; finally, use a constant pressure separatory funnel to add 1-5 mL methacryloyl chloride and 5.0-8.0 mL LTEA dropwise, the mixture is reacted at room temperature for 10-15 h, after the reaction, use a rotary evaporator to evaporate CH2Cl2 to dryness, extract with ethyl acetate, remove unreacted substances with 1-4 mol / L NaHSO4 solution, saturated Na The organic layer was washed with Cl solution, dried with Na2SO4, and finally concentrated using a rotary evaporator. The protected DMA was purified by column chromatography using a n-hexane / ethyl acetate mixture as the eluent. 12-15 g of a colorless, highly viscous liquid was obtained with a yield of 60-67%.

[0037] The advantages of the present invention are that the protected dopamethacrylamide (DMA) has many advantages such as low density, renewability, biocompatibility, biodegradability and good surface reactivity, which enhances the mechanical properties, customizability, design flexibility and processability of materials such as hydrogels and adhesives.

[0038] As a preference, step (7) preparation of CNF / P(HEMA-co-DMA) adhesive

[0039] 0.40-1 g of the protected DMA obtained in step (6), 1-4 g of HEMA (hydroxyethyl methacrylate) and 160-165 mg of AIBN were weighed and added to a round-bottom flask containing 25-30 mL of ethanol; after 3-6 freeze-thaw cycles, nitrogen was injected into the round-bottom flask; copolymerization was carried out at 65-75°C for 10-14 h, the copolymer was deprotected using 1-3 mol / L HCl (hydrogen chloride), and then the copolymer was precipitated with ether and filtered, and finally vacuum dried at 45-50°C for 10-15 h to obtain P(HEMA-co-DMA) copolymer; the P(HEMA-co-DMA) copolymer was dissolved in 1-3 mL of ethanol, and 0.045-0.512 g of CNF suspension was added to the P(HEMA-co-DMA) copolymer solution and stirred to prepare a composite adhesive with a CNF concentration of 0.1-0.8 wt%.

[0040] The advantages of the present invention are that the copolymer has high stability, the copolymer and the adhesive are conducive to cell adhesion and proliferation, and have good biocompatibility, and the cohesion is increased, thereby enhancing the adhesive performance.

[0041] As a preferred method, step (8) is to prepare the plywood with antibacterial and mildew-proof agent impregnated with film paper facing.

[0042] The fir core board is made according to the finger-jointed process technology of integrated wood, and then sanded to make the thickness deviation ≤0.2-0.5 mm, and the strips with a width-to-thickness ratio ≥2-5 mm are double-sided grooved, and then hot-pressed and glued with lignin-based adhesive to ensure the thickness deviation and surface flatness of the final product; Middle board: CNF / P (HEMA-co-DMA) adhesive is used to make the middle board spliced ​​by a splicing machine to ensure that there is no overlap on the surface after hot-pressing and gluing with the core board, and the gap is ≤0.5-1mm) The core board and the middle board are hot-pressed and glued with MUF co-condensation resin, and then scraped and repaired. After curing and sanding, the surface is covered with a veneer with a thickness of ≥0.8-1mm. Finally, through the processes of scraping, curing, sanding, etc., it is made into a base material for covering with impregnated film paper; finally, it is hot-pressed with a pressure of 0.1-0.6 MPa, pre-pressed for 1-5h, and hot-pressed for 16-20 min, 125-150℃; 0.5-0.8MPa, pre-pressing 0.5-1.0 h, hot pressing 12-15min, after gluing, temperature 118-125℃, hot pressing time 6-8 min, hot pressing pressure 0.7-1.0 MPa; then the best performance antibacterial and mildew-proof impregnated film paper is pressed on the surface of the substrate to obtain antibacterial and mildew-proof agent impregnated film paper veneer plywood.

[0043] The advantages of adopting the present invention are that the prepared antibacterial and mildew-proof impregnated film paper veneer plywood has extremely high antibacterial and mildew-proof functions and improved durability, surface scratch resistance and surface wear resistance, and improves the ability of the impregnated film paper to resist sharp and hard objects and the ability to resist loss under certain friction conditions.

[0044] In summary, the present invention has the following beneficial effects:

[0045] 1. The advantage of the present invention is that molten ZnCl2 has good electrical conductivity. When the temperature is too low, the activity is insufficient to react. When the temperature is high, the energy barrier of at least one substance can be broken, so that it can melt and react.

[0046] 2. The advantages of the present invention are that the activated lignin increases the reaction active sites, the low-melting ionic liquid has a smaller surface tension, density, and viscosity, the ion concentration in the system is higher, and the ion mobility is better, which increases the number of active ions in the system and promotes the full progress of the reaction.

[0047] 3. The present invention offers the advantages of reducing the methylol content of the MUF cocondensation resin, increasing the free urea content, and reducing the degree of polycondensation. Rational optimization of the molecular structure of the MUF cocondensation resin can fundamentally improve performance. The solids content and curing time of the MUF cocondensation resin both show a moderately increasing trend, while the free formaldehyde content shows a significant decreasing trend. The melamine resin is able to fully flow and melt, forming a wear-resistant and scratch-resistant transparent coating on the surface of the board, thereby exhibiting excellent wear and scratch resistance. Melamine can bind a large amount of formaldehyde, thereby reducing the free formaldehyde content.

[0048] 4. The advantages of the present invention are that it reduces costs and achieves the purpose of efficient utilization of biomass resources. Lignin can partially replace phenol to prepare lignin-modified phenolic resin adhesive because the molecule has active functional groups such as alcoholic hydroxyl and phenolic hydroxyl groups, which are similar to the structure of phenolic resin.

[0049] 5. The advantages of the present invention are that the protected dopamethacrylamide (DMA) has many advantages such as low density, renewability, biocompatibility, biodegradability and good surface reactivity, which enhances the mechanical properties of materials such as hydrogels and adhesives, customizability, design flexibility and processability.

[0050] 6. The advantages of the present invention are that the copolymer has high stability, the copolymer and the adhesive are conducive to cell adhesion and proliferation, have good biocompatibility, and increase cohesion, thereby enhancing its adhesive properties.

[0051] 7. The advantages of the present invention are that the prepared antibacterial and mildew-proof impregnated film paper veneer plywood has extremely high antibacterial and mildew-proof functions and improved durability, surface scratch resistance and surface wear resistance, improved ability of the impregnated film paper to resist sharp and hard objects, and the ability to resist wear under certain friction conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a production process of ENF grade impregnated film paper veneer plywood DETAILED DESCRIPTION

[0053] Example 1

[0054] Step (1) Synthesis of eutectic ionic liquid

[0055] First, Urea and ZnCl2 were dried. Urea was placed in a vacuum drying oven at 75°C for 10 hours. Urea and ZnCl2 were mixed in a conical flask at a molar fraction of 10% by weight of ZnCl2. The synthesis reaction temperature was between 60°C. After melting, the mixture was magnetically stirred until it became a colorless and transparent liquid.

[0056] Step (2) Purification of lignin

[0057] Dissolve industrial alkali lignin in water to form a solution with a concentration of approximately 10, stir evenly with a stirrer, add a 10% NaOH solution to adjust the pH to 10, and continue stirring until the alkali lignin is completely dissolved; then centrifuge the alkali lignin solution, discard the precipitate, and take the supernatant; add 10% sulfuric acid to the supernatant to adjust the pH to below 2; centrifuge again, discard the supernatant, and take the precipitate; wash the precipitate with dilute acid at a pH of approximately 2, stir evenly, centrifuge again, and take the precipitate; place the precipitate in an enamel dish and dry it in a water bath at approximately 40°C. After the surface moisture is completely evaporated, place it in a vacuum drying oven at 45°C and dry it for 12 hours to obtain purified lignin;

[0058] Step (3) Urea / ZnCl2 eutectic ionic liquid catalyzes the degradation and purification of alkali lignin

[0059] According to different solid-liquid ratios (1:20-1:70), the purified lignin prepared in step (2) was added to the two Urea / ZnCl2 low eutectic ionic liquids prepared in step (1), and the reaction was carried out at a temperature of 60°C for different times (1H). After the reaction, the lignin was purified by an industrial alkaline lignin purification method, and the obtained product was lignin activated by the Urea / ZnCl2 low eutectic ionic liquid;

[0060] Step (4) Preparation of MUF co-condensation resin: Add formaldehyde solution into a three-necked flask at once, adjust the pH to 7.0 with sodium hydroxide, stir and heat, heat to 85°C for 30 minutes and then keep warm for 55 minutes; adjust the pH value of the reaction system to 4.6, measure the state of the resin in 15°C water during the reaction, and when the resin becomes cloudy, adjust the pH value to 5.0, add M (melamine), the amount of melamine is 5% of the quality of urea, and react at 60°C for 1 hour; when the resin is dropped into water and a single point of turbidity appears, add urea, continue to react at 75°C, and when the resin appears flocculent precipitation, cool and adjust the pH value to about 5.0 to synthesize MUF (formaldehyde-melamine-urea) co-condensation resin;

[0061] Step (5) Preparation of lignin-based adhesive

[0062] First, polyethylene glycol 350 and 1% concentrated sulfuric acid are uniformly mixed under magnetic stirring conditions; then the activated lignin in step (3) and the mixed solution are placed in a 900 mL three-necked flask; after the two are uniformly mixed, the three-necked flask containing polyethylene glycol and activated lignin is placed in an oil bath pot heated in advance at a temperature of 100°C and steamed for 1 hour; when the steaming is completed, the oil bath pot is immediately removed, and the three-necked flask is placed in cold water to quickly lower the temperature to terminate the reaction in the three-necked flask. ; Pour a 50% volume concentration of dioxane solution into the reaction mixture to dissolve the reaction product, and transfer all the reaction products from the three-necked flask to a funnel for filtration to separate and remove the residues that did not participate in the reaction in the solution, and wash the residues with 50% dioxane solution several times to ensure that all the liquefied products are dissolved in the solution; secondly, use a rotary evaporator to evaporate the liquefied solution obtained after filtration at a temperature of 45°C, remove water and dioxane in the solution, and obtain a liquefied product. The evaporated liquefied product is then poured into a certain amount of distilled water and magnetically stirred for 1 hour to separate the free polyethylene glycol from the liquefied product and dissolve it in distilled water, separate it from the obtained precipitate, and then centrifuge the stirred mixture to separate the solution and the precipitate to obtain a lignin-based adhesive;

[0063] Step (6) Preparation of protected dopamethacrylamide (DMA)

[0064] 5.0 g of DOPA was weighed and added to a three-necked flask containing 150 mL of CH2Cl2. The mixture was stirred at room temperature to completely disperse the DOPA. 3.0 mL of TEA was then added dropwise using a constant-pressure separatory funnel. The mixture was allowed to react at room temperature for 1 h. Finally, 1 mL of methacryloyl chloride and 5.0 mL of TEA were added dropwise using a constant-pressure separatory funnel. The mixture was allowed to react at room temperature for 10 h. After the reaction, the CH2Cl2 was evaporated to dryness using a rotary evaporator, extracted with ethyl acetate, and unreacted materials were removed with a 1 mol / L NaHSO4 solution. The organic layer was washed with a saturated NaCl solution, dried with Na2SO4, and finally concentrated using a rotary evaporator. The protected DMA was purified by column chromatography using a n-hexane / ethyl acetate mixture as the eluent. 12 g of a colorless, high-viscosity liquid was obtained with a yield of 60%.

[0065] Step (7) Preparation of CNF / P(HEMA-co-DMA) adhesive

[0066] 0.40 g of the protected DMA obtained in step (6), 1 g of HEMA and 160 mg of AIBN were weighed and added to a round-bottom flask containing 25 mL of ethanol; after three freeze-thaw cycles, nitrogen was injected into the round-bottom flask; copolymerization was carried out at 65°C for 10 h, the copolymer was deprotected using 1 mol / L HCl, and then the copolymer was precipitated with ether and filtered, and finally dried in vacuo at 40°C for 10 h to obtain P(HEMA-co-DMA) copolymer; the P(HEMA-co-DMA) copolymer was dissolved in 1 mL of ethanol, and 0.045 g of CNF suspension was added to the P(HEMA-co-DMA) copolymer solution and stirred to obtain a composite adhesive with a CNF concentration of 0.1 wt%;

[0067] Step (8) Preparation of antibacterial and mildew-proof agent impregnated film paper veneer plywood

[0068] The fir core board is made according to the finger-jointed process technology of integrated wood, and then sanded to make the thickness deviation ≤0.2mm, and the strips with a width-to-thickness ratio ≥2mm are double-sided grooved, and then hot-pressed and glued with lignin-based adhesive to ensure the thickness deviation and surface flatness of the final product; Middle board: CNF / P (HEMA-co-DMA) adhesive is used to make the middle board spliced ​​by a splicing machine to ensure that there is no overlap on the surface after hot-pressing and gluing with the core board, and the gap is ≤0.5mm. The core board and the middle board are hot-pressed and glued with MUF co-condensation resin, and then scraped and repaired. After curing and sanding, the surface is covered with treated veneer, and finally through the processes of scraping, curing, sanding, etc. It is made into a base material for covering impregnated film paper; finally, it is hot-pressed with a pressure of 0.1 MPa, pre-pressing for 2h, hot pressing for 17 min, 135℃; 0.6MPa, pre-pressing 0.6 h, hot pressing for 13 minutes, after gluing: temperature 120℃, hot pressing time 7 minutes, hot pressing pressure 0.8MPa; then the best performance antibacterial and mildew-proof impregnated film paper is pressed on the surface of the substrate to obtain antibacterial and mildew-proof agent impregnated film paper veneer plywood.

[0069] Example 2

[0070] Step (1) Synthesis of eutectic ionic liquid

[0071] First, Urea and ZnCl2 were dried. Urea was placed in a vacuum drying oven at 76°C for 12 hours. Urea and ZnCl2 were mixed in a conical flask at a molar fraction of 20% by weight of ZnCl2. The synthesis reaction temperature was between 70°C. After melting, the mixture was magnetically stirred until it became a colorless and transparent liquid.

[0072] Step (2) Purification of lignin

[0073] Industrial alkali lignin is dissolved in water to form a solution with a concentration of approximately 11%. The solution is stirred evenly with a stirrer, and an appropriate amount of 11% NaOH solution is added to adjust the pH to approximately 12. The solution is stirred continuously until the alkali lignin is completely dissolved. The alkali lignin solution is then centrifuged in a centrifuge, the precipitate is discarded, and the supernatant is taken. 13% sulfuric acid is added to the supernatant to adjust the pH to below 3. The solution is centrifuged again, the supernatant is discarded, and the precipitate is taken. The precipitate is washed with dilute acid with a pH of approximately 3, stirred evenly, and centrifuged in a centrifuge to take the precipitate. The precipitate is placed in an enamel dish and dried in a water bath at approximately 45°C. After the surface moisture is completely evaporated, the precipitate is placed in a vacuum drying oven at 50°C and dried for 12 hours to obtain chemically purified lignin.

[0074] Step (3) Urea / ZnCl2 eutectic ionic liquid catalyzes the degradation and purification of alkali lignin

[0075] According to different solid-liquid ratios (1:20-1:70), the purified lignin prepared in step (2) was added to the two Urea / ZnCl2 low eutectic ionic liquids prepared in step (1), and the reaction was carried out at a temperature of 100°C for different times (3 hours). After the reaction, the lignin was purified by an industrial alkaline lignin purification method, and the obtained product was lignin activated by the Urea / ZnCl2 low eutectic ionic liquid;

[0076] Step (4) Preparation of MUF cocondensation resin

[0077] The formaldehyde solution was added to a three-necked flask at once, and the pH was adjusted to 7.5 with sodium hydroxide. The flask was stirred and heated to 86°C over 35 minutes, then kept warm for 58 minutes. The pH of the reaction system was adjusted to 4.7. During the reaction, the state of the resin in 15°C water was measured. When the resin became cloudy, the pH was adjusted to 5.0, and M (melamine) was added at a concentration of 10% of the urea quality. The reaction was carried out at 66°C for 1 hour. When the resin showed turbidity when dropped into water, urea was added, and the reaction was continued at 75°C. When the resin formed a flocculent precipitate, the temperature was lowered and the pH was adjusted to approximately 5.5, thereby synthesizing a MUF (formaldehyde-melamine-urea) co-condensation resin.

[0078] Step (5) Preparation of lignin-based adhesive

[0079] First, polyethylene glycol 360 and 2% concentrated sulfuric acid are uniformly mixed under magnetic stirring conditions; then the activated lignin in step (3) and the mixed solution are placed in a 950 mL three-necked flask; after the two are uniformly mixed, the three-necked flask containing polyethylene glycol and activated lignin is placed in an oil bath pot heated in advance at a temperature of 120°C and steamed for 2 hours; when the steaming is completed, the oil bath pot is immediately removed, and the three-necked flask is placed in cold water to quickly lower the temperature to terminate the reaction in the three-necked flask. ; Pour a 60% volume concentration of dioxane solution into the reaction mixture to dissolve the reaction product, and transfer all the reaction products from the three-necked flask to a funnel for filtration to separate and remove the residues that did not participate in the reaction in the solution, and wash the residues with 60% dioxane solution several times to ensure that all the liquefied products are dissolved in the solution; secondly, use a rotary evaporator to evaporate the liquefied solution obtained after filtration at a temperature of 46°C, remove water and dioxane in the solution, and obtain a liquefied product. The evaporated liquefied product is then poured into a certain amount of distilled water and magnetically stirred for 2 hours to separate the free polyethylene glycol from the liquefied product and dissolve it in distilled water, separate it from the obtained precipitate, and then centrifuge the stirred mixture to separate the solution and the precipitate to obtain a lignin-based adhesive;

[0080] Step (6) Preparation of protected dopamethacrylamide (DMA)

[0081] 6.0 g of DOPA was weighed and added to a three-necked flask containing 160 mL of CH2Cl2. The mixture was stirred at room temperature to completely disperse the DOPA. 4.0 mL of TEA was then added. 16.0 mL of triethylsilyl chloride and 11 mL of TEA were then added dropwise using a constant-pressure separatory funnel. The mixture was allowed to react at room temperature for 2 h. Finally, 3 mL of methacryloyl chloride and 6.0 mL of TEA were added dropwise using a constant-pressure separatory funnel. The mixture was allowed to react at room temperature for 12 h. After the reaction, the CH2Cl2 was evaporated to dryness using a rotary evaporator, extracted with ethyl acetate, and unreacted materials were removed with a 2 mol / L NaHSO4 solution. The organic layer was washed with a saturated NaCl solution, dried with Na2SO4, and finally concentrated using a rotary evaporator. The protected DMA was purified by column chromatography using a n-hexane / ethyl acetate mixture as the eluent. 13 g of a colorless, high-viscosity liquid was obtained with a yield of 64%.

[0082] Step (7) Preparation of CNF / P(HEMA-co-DMA) adhesive

[0083] 0.5 g of the protected DMA obtained in step (6), 2 g of HEMA and 162 mg of AIBN were weighed and added to a round-bottom flask containing 26 mL of ethanol; after 5 freeze-thaw cycles, nitrogen was injected into the round-bottom flask; copolymerization was carried out at 66 ° C for 12 h, and the copolymer was deprotected using 2 mol / L HCl, and then the copolymer was precipitated with ether and filtered, and finally dried in vacuo at 47 ° C for 13 h to obtain P (HEMA-co-DMA) copolymer; the P (HEMA-co-DMA) copolymer was dissolved in 2 mL of ethanol, and 0.045 g of CNF suspension was added to the P (HEMA-co-DMA) copolymer solution and stirred to obtain a composite adhesive with a CNF concentration of 0.2 wt%;

[0084] Step (8) Preparation of antibacterial and mildew-proof agent impregnated film paper veneer plywood

[0085] The fir core board is made according to the finger-jointed process technology of integrated wood, and then sanded to make the thickness deviation ≤0.4mm, and the strips with a width-to-thickness ratio ≥3mm are double-sided grooved, and then hot-pressed and glued with lignin-based adhesive to ensure the thickness deviation and surface flatness of the final product; Middle board: CNF / P (HEMA-co-DMA) adhesive is used to make the middle board spliced ​​by a splicing machine to ensure that there is no overlap on the surface after hot-pressing and gluing with the core board, and the gap is ≤0.6mm. The core board and the middle board are hot-pressed and glued with MUF co-condensation resin, and then scraped and repaired. After curing and sanding, the surface is covered with a veneer with a thickness of ≥0.9mm. Finally, through the processes of scraping, curing, sanding, etc., it is made into a base material for covering impregnated film paper; finally, it is hot-pressed with a pressure of 0.1MPa, pre-pressing for 1h, hot pressing for 16min, 125℃; 0.5MPa, pre-pressing for 0.5h, hot pressing for 12 min, after gluing, the temperature was 118℃, the hot pressing time was 6 min, and the hot pressing pressure was 0.7 MPa; then the antibacterial and mildew-proof impregnated film paper with the best performance was pressed onto the surface of the substrate to obtain the antibacterial and mildew-proof agent impregnated film paper veneer plywood.

[0086] Example 3

[0087] Step (1) Synthesis of eutectic ionic liquid

[0088] First, Urea and ZnCl2 were dried. Urea was placed in a vacuum drying oven at 80°C for 12 hours. Urea and ZnCl2 were mixed in a conical flask at a molar fraction of 30% by weight of ZnCl2. The synthesis reaction temperature was 80°C. After melting, the mixture was magnetically stirred until it became a colorless and transparent liquid.

[0089] Step (2) Purification of lignin

[0090] Industrial alkali lignin is dissolved in water to form a solution with a concentration of approximately 14%, stirred evenly with a stirrer, and an appropriate amount of 13% NaOH solution is added to adjust the pH to approximately 13. Stirring is continued until the alkali lignin is completely dissolved. The alkali lignin solution is then centrifuged in a centrifuge, the precipitate is discarded, and the supernatant is taken. 13% sulfuric acid is added to the supernatant to adjust the pH to below 3. Centrifugation is performed again, the supernatant is discarded, and the precipitate is taken. The precipitate is washed with dilute acid with a pH of approximately 3, stirred evenly, and centrifuged in a centrifuge to take the precipitate. The precipitate is placed in an enamel dish and dried in a water bath at approximately 45°C. After the surface moisture is completely evaporated, it is placed in a vacuum drying oven at 50°C and dried for 24 hours to obtain chemically purified lignin.

[0091] Step (3) Urea / ZnCl2 eutectic ionic liquid catalyzes the degradation and purification of alkali lignin

[0092] According to different solid-liquid ratios (1:20-1:70), the purified lignin prepared in step (2) was added to the two Urea / ZnCl2 low eutectic ionic liquids prepared in step (1), and the reaction was carried out at a temperature of 90°C for different times (6 hours). After the reaction, the lignin was purified by an industrial alkaline lignin purification method, and the obtained product was lignin activated by the Urea / ZnCl2 low eutectic ionic liquid;

[0093] Step (4) Preparation of MUF cocondensation resin

[0094] The formaldehyde solution was added to a three-necked flask at once, and the pH was adjusted to 8.0 with sodium hydroxide. The flask was stirred and heated to 90°C over 40 minutes, then kept warm for 60 minutes. The pH of the reaction system was adjusted to 4.8. During the reaction, the state of the resin in 20°C water was measured. When the resin became cloudy, the pH was adjusted to 9.0, and M (melamine) was added at an amount equal to 15% of the urea quality. The reaction was carried out at 85°C for 2 hours. When the resin became cloudy when dropped into water, urea was added, and the reaction was continued at 80°C. When the resin formed a flocculent precipitate, the temperature was lowered and the pH was adjusted to approximately 8.0, thereby synthesizing a MUF (formaldehyde-melamine-urea) co-condensation resin.

[0095] Step (5) Preparation of lignin-based adhesive

[0096] First, polyethylene glycol 400 and 5% concentrated sulfuric acid are uniformly mixed under magnetic stirring conditions; then the activated lignin in step (3) and the mixed solution are placed in a 1000 mL three-necked flask; after the two are uniformly mixed, the three-necked flask containing polyethylene glycol and activated lignin is placed in an oil bath pot heated in advance at a temperature of 170°C and steamed for 4 hours; when the steaming is completed, the oil bath pot is immediately removed, and the three-necked flask is placed in cold water to quickly lower the temperature to terminate the reaction in the three-necked flask; A 100% volume concentration of dioxane solution was poured into the reaction mixture to dissolve the reaction product. All the reaction products were transferred from the three-necked flask to a funnel for filtration to separate and remove the residues that did not participate in the reaction. The residues were washed several times with a 100% dioxane solution to ensure that all the liquefied products were dissolved in the solution. The liquefied solution obtained after filtration was evaporated using a rotary evaporator at a temperature of 50°C to remove water and dioxane from the solution to obtain a liquefied product. The evaporated liquefied product was then poured into a certain amount of distilled water and magnetically stirred for 4 hours to separate the free polyethylene glycol from the liquefied product and dissolve it in distilled water to separate it from the precipitate. The stirred mixture was then centrifuged to separate the solution and the precipitate to obtain a lignin-based adhesive.

[0097] Step (6) Preparation of protected dopamethacrylamide (DMA)

[0098] 9.0 g of DOPA was weighed and added to a three-necked flask containing 200 mL of CH2Cl2. The mixture was stirred at room temperature to completely disperse the DOPA. 6.6 mL of TEA was then added. 17.0 mL of triethylsilyl chloride and 14.0 mL of LTEA were then added dropwise using a constant-pressure separatory funnel. The mixture was allowed to react at room temperature for 4 h. Finally, 5 mL of methacryloyl chloride and 5.0-8.0 mL of LTEA were added dropwise using a constant-pressure separatory funnel. The mixture was allowed to react at room temperature for 15 h. After the reaction, the CH2Cl2 was evaporated to dryness using a rotary evaporator, extracted with ethyl acetate, and unreacted materials were removed with a 4 mol / L NaHSO4 solution. The organic layer was washed with a saturated NaCl solution, dried with Na2SO4, and finally concentrated using a rotary evaporator. The protected DMA was purified by column chromatography using a n-hexane / ethyl acetate mixture as the eluent. 15 g of a colorless, high-viscosity liquid was obtained with a yield of 67%.

[0099] Step (7) Preparation of CNF / P(HEMA-co-DMA) adhesive

[0100] 1 g of the protected DMA obtained in step (6), 4 g of HEMA and 165 mg of AIBN were weighed and added to a round-bottom flask containing 30 mL of ethanol; after 6 freeze-thaw cycles, nitrogen was injected into the round-bottom flask; copolymerization was carried out at 75 °C for 10 h, the copolymer was deprotected using 3 mol / L HCl, and then the copolymer was precipitated with ether and filtered, and finally dried under vacuum at 50 °C for 15 h to obtain P(HEMA-co-DMA) copolymer; the P(HEMA-co-DMA) copolymer was dissolved in 3 mL of ethanol, and 0.512 g of CNF suspension was added to the P(HEMA-co-DMA) copolymer solution and stirred to obtain a composite adhesive with a CNF concentration of 0.8 wt%;

[0101] Step (8) Preparation of antibacterial and mildew-proof agent impregnated film paper veneer plywood

[0102] The fir core board is made according to the finger-jointed process technology of integrated wood, and then sanded to make the thickness deviation ≤0.5mm, and the strips with a width-to-thickness ratio ≥5mm are double-sided grooved, and then hot-pressed and glued with lignin-based adhesive to ensure the thickness deviation and surface flatness of the final product; Middle board: CNF / P (HEMA-co-DMA) adhesive is used to make the middle board spliced ​​by a splicing machine to ensure that there is no overlap on the surface after hot-pressing and gluing with the core board, and the gap is ≤1mm) The core board and the middle board are hot-pressed and glued with MUF co-condensation resin, and then scraped and repaired. After curing and sanding, the surface is covered with a veneer with a thickness of ≥1mm. Finally, through the processes of scraping, curing, sanding, etc., it is made into a base material for covering impregnated film paper; finally, it is hot-pressed with a hot-pressing pressure of 0.1 MPa, pre-pressing for 1 h, hot pressing for 16 min, 125℃; 0.6MPa, pre-pressing 0.5 h, hot pressing for 14 minutes, after gluing: temperature 119 ° C, hot pressing time 6 minutes, hot pressing pressure 0.7 MPa; then the antibacterial and mildew-proof impregnated film paper with the best performance is pressed on the surface of the substrate, and the antibacterial and mildew-proof impregnated film paper with the best performance is pressed on the surface of the substrate to obtain the antibacterial and mildew-proof agent impregnated film paper veneer plywood.

[0103] Example 4

[0104] Step (1) Synthesis of eutectic ionic liquid

[0105] First, Urea and ZnCl2 were dried. Urea was placed in a vacuum drying oven at 80°C for 12 hours. Urea and ZnCl2 were mixed in a conical flask at a molar fraction of 10%, 20%, 30%, and 40% of ZnCl2. The reaction temperatures were 60°C, 80°C, and 100°C, respectively. After melting, the mixture was magnetically stirred until it became a colorless and transparent liquid.

[0106] Step (2) Purification of lignin

[0107] Dissolve industrial alkali lignin in water to form a solution with a concentration of about 10%, stir it evenly with a stirrer, add an appropriate amount of 10% NaOH solution to adjust the pH to about 11, and continue stirring until the alkali lignin is completely dissolved. Then place the alkali lignin solution in a centrifuge for centrifugation. After centrifugation, discard the precipitate and take the supernatant. Add 10% sulfuric acid to the clear liquid to adjust the pH to below 3. Centrifuge again, discard the supernatant after centrifugation, and take the precipitate. Wash the precipitate with dilute acid with a pH of about 4, stir it evenly, place it in a centrifuge for centrifugation, and take the precipitate; place the precipitate in an enamel dish and dry it in a water bath at about 45°C. After the surface moisture is completely evaporated, place it in a 50°C vacuum drying oven and dry it for 24 hours to obtain chemically purified lignin;

[0108] Step (3) Urea / ZnCl2 eutectic ionic liquid catalyzes the degradation and purification of alkali lignin

[0109] According to different solid-liquid ratios (1:20-1:70), the purified lignin prepared in step (2) was added to the two Urea / ZnCl2 eutectic ionic liquids prepared in step (1), and the reaction was carried out at a temperature of 100°C for different times (1H, 2H, 8H). After the reaction, the lignin was purified by an industrial alkaline lignin purification method, and the obtained product was lignin activated by the Urea / ZnCl2 eutectic ionic liquid;

[0110] Step (4) Preparation of MUF cocondensation resin

[0111] The formaldehyde solution was added to a three-necked flask at once, and the pH was adjusted to 7.5 with sodium hydroxide. The flask was stirred and heated to 90°C over 40 minutes, then kept warm for 60 minutes. The pH of the reaction system was adjusted to 4.7. During the reaction, the state of the resin in 20°C water was measured. When the resin became cloudy, the pH was adjusted to 9.0, and M (melamine) was added at a concentration of 10% of the urea quality. The reaction was carried out at 85°C for 2 hours. When the resin became cloudy when dropped into water, urea was added, and the reaction was continued at 80°C. When the resin formed a flocculent precipitate, the temperature was lowered and the pH was adjusted to approximately 8.0, thereby synthesizing a MUF (formaldehyde-melamine-urea) co-condensation resin.

[0112] Step (5) Preparation of lignin-based adhesive

[0113] First, polyethylene glycol 400 and 1% concentrated sulfuric acid are uniformly mixed under magnetic stirring conditions. Then, the activated lignin in step (3) and the mixed solution are placed in a 1000 mL three-necked flask; after the two are uniformly mixed, the three-necked flask containing polyethylene glycol and activated lignin is placed in an oil bath pot heated in advance at a temperature of 160°C for steaming for 2 hours. When the steaming is completed, the oil bath pot is immediately removed, and the three-necked flask is placed in cold water to quickly lower the temperature to terminate the reaction in the three-necked flask. A dioxane solution with a volume concentration of 80% is poured into the mixture after the reaction to dissolve the reaction product, and all the reaction products are transferred from the three-necked flask to a funnel for filtration to separate and remove the residues that have not participated in the reaction in the solution, and the residues are washed with 80% dioxane solution several times to ensure that all liquefied products are dissolved in the solution. The liquefied solution obtained after filtration is then evaporated using a rotary evaporator at a temperature of 45-50°C to remove water and dioxane from the solution, thereby obtaining a liquefied product. The evaporated liquefied product is then poured into a certain amount of distilled water and magnetically stirred for 2 hours to separate the free polyethylene glycol from the liquefied product and dissolve it in the distilled water, separating it from the resulting precipitate. The stirred mixture is then centrifuged to separate the solution from the precipitate, ultimately obtaining a lignin-based adhesive.

[0114] Step (6) Preparation of protected dopamethacrylamide (DMA)

[0115] 9.0 g of DOPA was weighed and added to a three-necked flask containing 180 mL of CH₂Cl₂. Stirring was performed at room temperature until completely dispersed, and 6.6 mL of LTEA was added. Subsequently, 16.0 mL of triethylsilyl chloride and 14.0 mL of LTEA were added dropwise using a constant-pressure separatory funnel. The reaction was allowed to proceed at room temperature for 4 h. Finally, 4.7 mL of methacryloyl chloride and 7.5 mL of LTEA were added dropwise using a constant-pressure separatory funnel. The mixture was allowed to react at room temperature for 12 h. After the reaction, the CH₂Cl₂ was evaporated to dryness using a rotary evaporator, extracted with ethyl acetate, and unreacted material was removed with a 1 mol / L NaHSO₄ solution. The organic layer was washed with saturated NaCl solution, dried with Na₂SO₄, and finally concentrated using a rotary evaporator. The protected DMA was purified by column chromatography using a hexane / ethyl acetate mixture as the eluent. The resulting product was 14.2 g of a colorless, highly viscous liquid with a yield of 66.7%.

[0116] Step (7) Preparation of CNF / P(HEMA-co-DMA) adhesive

[0117] 0.45 g of the protected DMA obtained in step (6), 1.17 g of HEMA, and 164 mg of AIBN were weighed and added to a round-bottom flask containing 30 mL of ethanol. After five freeze-thaw cycles, nitrogen was injected into the round-bottom flask. Copolymerization was carried out at 70°C for 14 h. The copolymer was deprotected using 1 mol / L HCl, and then precipitated with ether and filtered. Finally, the copolymer was dried under vacuum at 50°C for 12 h to obtain P(HEMA-co-DMA) copolymer. P(HEMA-co-DMA) copolymer was dissolved in 1 mL of ethanol, and 0.045 g, 0.095 g, 0.148 g, 0.207 g, 0.272 g, 0.344 g, 0.432 g, and 0.512 g of CNF suspension were added to the P(HEMA-co-DMA) copolymer solution, respectively, and stirred to prepare composite adhesives with CNF concentrations of 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, and 0.8 wt%.

[0118] Step (8) Preparation of antibacterial and mildew-proof agent impregnated film paper veneer plywood

[0119] The fir core board is made according to the finger-jointing process of integrated wood, and then sanded to make the thickness deviation ≤0.2mm, and the strips with a width-to-thickness ratio ≥3mm are double-sided grooved, and then hot-pressed with lignin-based adhesive to ensure the thickness deviation and surface flatness of the final product; Middle board: CNF / P (HEMA-co-DMA) adhesive is used to make the middle board spliced ​​by a splicing machine to ensure that there is no overlap on the surface after hot-pressing and gluing with the core board, and the gap is ≤0.5mm). The core board and the middle board are hot-pressed and glued with MUF co-condensation resin, and then scraped and repaired. After curing and sanding, the surface is covered with a veneer with a thickness of ≥0.8mm. Finally, through the processes of scraping, curing, sanding, etc., it is made into a base material for covering with impregnated film paper, and finally through the hot pressing process. The hot pressing pressure is 0.6 MPa, pre-pressing for 1 h, hot pressing for 16 min, 125℃; 0.6 MPa, pre-pressing for 0.5 h, hot pressing for 12 min, and after gluing, the antibacterial and mildew-proof impregnated film paper with the best performance was pressed onto the surface of the substrate at a temperature of 130°C, a hot pressing time of 7 min, and a hot pressing pressure of 0.8 MPa to obtain the antibacterial and mildew-proof agent impregnated film paper veneer plywood.

[0120] Comparative Example 1

[0121] Step (1) Synthesis of eutectic ionic liquid

[0122] First, dry Urea and ZnCl2. Place Urea in a vacuum drying oven at 90°C for 20 hours. Mix Urea and ZnCl2 in a conical flask at a molar fraction of 50% with ZnCl2. Keep the reaction temperature at 50°C. After melting, stir magnetically until the mixture becomes a colorless, transparent liquid.

[0123] Step (2) Purification of lignin

[0124] Industrial alkali lignin is dissolved in water to form a solution with a concentration of approximately 20%. The solution is stirred evenly with a stirrer, and an appropriate amount of 20% NaOH solution is added to adjust the pH to approximately 20. The solution is stirred continuously until the alkali lignin is completely dissolved. The alkali lignin solution is then centrifuged in a centrifuge, the precipitate is discarded, and the supernatant is taken. 20% sulfuric acid is added to the supernatant to adjust the pH to below 3. The solution is centrifuged again, the supernatant is discarded, and the precipitate is taken. The precipitate is washed with dilute acid with a pH of approximately 3, stirred evenly, and centrifuged in a centrifuge to take the precipitate. The precipitate is placed in an enamel dish and dried in a water bath at approximately 45°C. After the surface moisture is completely evaporated, the precipitate is placed in a vacuum drying oven at 60°C and dried for 12 hours to obtain chemically purified lignin.

[0125] Step (3) Urea / ZnCl2 eutectic ionic liquid catalyzes the degradation and purification of alkali lignin

[0126] According to different solid-liquid ratios (1:20-1:70), the purified lignin prepared in step (2) was added to the two Urea / ZnCl2 low eutectic ionic liquids prepared in step (1), and the reaction was carried out at a temperature of 70°C for different times (3 hours). After the reaction, the lignin was purified by an industrial alkaline lignin purification method, and the obtained product was lignin activated by the Urea / ZnCl2 low eutectic ionic liquid;

[0127] Step (4) Preparation of MUF cocondensation resin

[0128] The formaldehyde solution was added to a three-necked flask at once, and the pH was adjusted to 10.0 with sodium hydroxide. The mixture was stirred and heated to 100°C over 60 minutes, then kept warm for 120 minutes. The pH of the reaction system was adjusted to 5.0. During the reaction, the state of the resin in 30°C water was measured. When the resin became cloudy, the pH was adjusted to 10.0, and M (melamine) was added at a concentration of 20% of the urea quality. The reaction was continued at 100°C for 5 hours. When the resin became cloudy when dropped into water, urea was added, and the reaction was continued at 100°C. When the resin formed a flocculent precipitate, the temperature was lowered and the pH was adjusted to approximately 12.0, thereby synthesizing a MUF (formaldehyde-melamine-urea) co-condensation resin.

[0129] Step (5) Preparation of lignin-based adhesive

[0130] First, polyethylene glycol 360 and 2% concentrated sulfuric acid are uniformly mixed under magnetic stirring conditions; then the activated lignin in step (3) and the mixed solution are placed in a 95 mL three-necked flask; after the two are uniformly mixed, the three-necked flask containing polyethylene glycol and activated lignin is placed in an oil bath pot heated in advance at a temperature of 120°C and steamed for 2 hours; when the steaming is completed, the oil bath pot is immediately removed, and the three-necked flask is placed in cold water to quickly lower the temperature to terminate the reaction in the three-necked flask; A 60% volume concentration of dioxane solution was poured into the reaction mixture to dissolve the reaction product, and all the reaction products were transferred from the three-necked flask to a funnel for filtration to separate and remove the residue that did not participate in the reaction in the solution. The residue was washed several times with a 60% dioxane solution to ensure that all the liquefied products were dissolved in the solution. The liquefied solution obtained after filtration was evaporated using a rotary evaporator at a temperature of 46°C to remove water and dioxane from the solution to obtain a liquefied product. The evaporated liquefied product was then poured into a certain amount of distilled water and magnetically stirred for 10 hours to separate the free polyethylene glycol from the liquefied product and dissolve it in distilled water to separate it from the obtained precipitate. The stirred mixture was then centrifuged to separate the solution and the precipitate to obtain a lignin-based adhesive.

[0131] Step (6) Preparation of antibacterial and mildew-proof agent impregnated film paper veneer plywood

[0132] The fir core board is made according to the finger-jointed process technology of integrated wood, and then sanded to make the thickness deviation ≤0.4mm, and the strips with a width-to-thickness ratio ≥3mm are double-sided grooved, and then hot-pressed and glued with lignin-based adhesive to ensure the thickness deviation and surface flatness of the final product; Middle board: MUF co-condensation resin is used to make the middle board spliced ​​by a splicing machine to ensure that there is no overlap on the surface after hot-pressing and gluing with the core board, and the gap is ≤0.6mm. The core board and the middle board are hot-pressed and glued with lignin-based adhesive, and then scraped and repaired. After curing and sanding, the surface is covered with a veneer with a thickness of ≥0.9mm. Finally, through the processes of scraping, curing, sanding, etc., it is made into a base material that can be used to cover the impregnated film paper; finally, it is hot-pressed with a pressure of 1 MPa, pre-pressed for 10h, and hot pressed for 30 min, 150℃; 1MPa, pre-pressing for 0.5h, hot pressing for 20min, after gluing: temperature 120℃, hot pressing time 10min, hot pressing pressure 2.0MPa; then the antibacterial and mildew-proof impregnated film paper with the best performance is pressed on the surface of the substrate to obtain the antibacterial and mildew-proof agent impregnated film paper veneer plywood.

[0133] Comparative Example 2

[0134] Step (1) Synthesis of eutectic ionic liquid

[0135] First, Urea and ZnCl2 were dried. Urea was placed in a vacuum drying oven at 100°C for 12 hours. Urea and ZnCl2 were mixed in a conical flask at a molar fraction of 30% by weight of ZnCl2. The reaction temperature was set at 100°C. After melting, the mixture was magnetically stirred until it became a colorless and transparent liquid.

[0136] Step (2) Purification of lignin

[0137] Industrial alkali lignin is dissolved in water to form a solution with a concentration of approximately 50%, stirred evenly with a stirrer, and an appropriate amount of 53% NaOH solution is added to adjust the pH to approximately 20. Stirring is continued until the alkali lignin is completely dissolved. The alkali lignin solution is then centrifuged in a centrifuge, the precipitate is discarded, and the supernatant is taken. 13% sulfuric acid is added to the supernatant to adjust the pH to below 3. Centrifugation is performed again, the supernatant is discarded, and the precipitate is taken. The precipitate is washed with dilute acid with a pH of approximately 3, stirred evenly, and centrifuged in a centrifuge to take the precipitate. The precipitate is placed in an enamel dish and dried in a water bath at approximately 45°C. After the surface moisture is completely evaporated, it is placed in a vacuum drying oven at 50°C and dried for 24 hours to obtain chemically purified lignin.

[0138] Step (3) Preparation of lignin-based adhesive

[0139] First, polyethylene glycol 400 and 60% concentrated sulfuric acid were uniformly mixed under magnetic stirring conditions; the lignin purified in step 2 and the mixed solution were then placed in a 1000 mL three-necked flask; after the two were uniformly mixed, the three-necked flask containing polyethylene glycol and activated lignin was placed in a pre-heated oil bath at 170°C for cooking for 10 hours; when the cooking was completed, the oil bath was immediately removed, and the three-necked flask was placed in cold water to quickly lower the temperature to terminate the reaction in the three-necked flask; A 100% volume concentration of dioxane solution was poured into the reaction mixture to dissolve the reaction product. All the reaction products were transferred from the three-necked flask to a funnel for filtration to separate and remove the residues that did not participate in the reaction. The residues were washed several times with a 100% dioxane solution to ensure that all the liquefied products were dissolved in the solution. The liquefied solution obtained after filtration was evaporated using a rotary evaporator at a temperature of 50°C to remove water and dioxane from the solution to obtain a liquefied product. The evaporated liquefied product was then poured into a certain amount of distilled water and magnetically stirred for 4 hours to separate the free polyethylene glycol from the liquefied product and dissolve it in distilled water to separate it from the precipitate. The stirred mixture was then centrifuged to separate the solution and the precipitate to obtain a lignin-based adhesive.

[0140] Step (4) Preparation of protected dopamethacrylamide (DMA)

[0141] 10 g of DOPA was weighed and added to a three-necked flask containing 500 mL of CH2Cl2. The mixture was stirred at room temperature to completely disperse the DOPA. 7.0 mL of TEA was then added dropwise using a constant-pressure separatory funnel. The mixture was allowed to react at room temperature for 10 h. Finally, 8 mL of methacryloyl chloride and 10 mL of TEA were added dropwise using a constant-pressure separatory funnel. The mixture was allowed to react at room temperature for 30 h. After the reaction, the CH2Cl2 was evaporated to dryness using a rotary evaporator, extracted with ethyl acetate, and unreacted materials were removed with a 4 mol / L NaHSO4 solution. The organic layer was washed with a saturated NaCl solution, dried with Na2SO4, and finally concentrated using a rotary evaporator. The protected DMA was purified by column chromatography using a n-hexane / ethyl acetate mixture as the eluent. 2 g of a colorless, high-viscosity liquid was obtained with a yield of 67%.

[0142] Step (5) Preparation of CNF / P(HEMA-co-DMA) adhesive

[0143] 1 g of the protected DMA obtained in step (6), 4 g of HEMA (hydroxyethyl methacrylate) and 165 mg of AIBN were weighed and added to a round-bottom flask containing 30 mL of ethanol; after 9 freeze-thaw cycles, nitrogen was injected into the round-bottom flask; copolymerization was carried out at 75°C for 20 h, and the copolymer was deprotected using 3 mol / L HCl (hydrogen chloride), and then the copolymer was precipitated with ether and filtered, and finally dried under vacuum at 50°C for 15 h to obtain P(HEMA-co-DMA) copolymer; the P(HEMA-co-DMA) copolymer was dissolved in 3 mL of ethanol, and 1 g of CNF suspension was added to the P(HEMA-co-DMA) copolymer solution and stirred to obtain a composite adhesive with a CNF concentration of 3 wt%;

[0144] Step (6) Preparation of antibacterial and mildew-proof agent impregnated film paper veneer plywood

[0145] The fir core board is made according to the finger-jointed process technology of integrated wood, and then sanded to make the thickness deviation ≤0.5mm, and the strips with a width-to-thickness ratio ≥5mm are double-sided grooved, and then hot-pressed and glued with lignin-based adhesive to ensure the thickness deviation and surface flatness of the final product; Middle board: CNF / P (HEMA-co-DMA) adhesive is used to make the middle board spliced ​​by a splicing machine to ensure that there is no overlap on the surface after hot-pressing and gluing with the core board, and the gap is ≤1mm) The core board and the middle board are hot-pressed and glued with MUF co-condensation resin, and then scraped and repaired. After curing and sanding, the surface is covered with a veneer with a thickness of ≥1mm. Finally, through the processes of scraping, curing, sanding, etc., it is made into a base material for covering impregnated film paper; finally, it is hot-pressed with a hot-pressing pressure of 0.8 MPa, pre-pressing for 2h, hot pressing for 13min, 120℃; 0.1MPa, pre-pressing 0.3 h, hot pressing for 10 minutes, after gluing: temperature 100℃, hot pressing time 3 minutes, hot pressing pressure 0.5 MPa; then the antibacterial and mildew-proof impregnated film paper with the best performance is pressed on the surface of the substrate, and the antibacterial and mildew-proof impregnated film paper with the best performance is pressed on the surface of the substrate to obtain the antibacterial and mildew-proof agent impregnated film paper veneer plywood.

[0146] Comparison of detection experiments:

[0147] The ENF-grade impregnated film paper veneer plywood comparative products 1 and 2 obtained in Examples 1 to 4 were tested. The specific testing method is as follows:

[0148] Determination of phenolic hydroxyl content in lignin

[0149] The phenolic structure forms phenol oxide ions in alkaline solutions, which strengthen the conjugated system with the benzene ring, increasing the intensity of the ultraviolet absorption peak and shifting it toward the long-wave direction. Therefore, by utilizing the characteristic of the ultraviolet spectrum changes of phenolic compounds in alkaline solutions and neutral or slightly acidic solutions, the ionization differential spectroscopy method can be used to quantitatively detect phenolic hydroxyl groups.

[0150] Weigh 10-15 mg of alkali lignin sample and dissolve it in 10 mL of dioxane solution. Then, take three 2 mL portions of the dioxane lignin solution and add them to three 50 mL volumetric flasks. Dilute one portion to the mark with pH 6 buffer, another portion to the mark with pH 12 buffer, and the final portion to the mark with 0.2 mol / L NaOH solution. Shake thoroughly. Pour the solution into a quartz cuvette and measure the absorbance at 300 nm and 360 nm relative to a pH 6 blank solution.

[0151] Bond strength test method

[0152] Use an electric saw to cut a wooden block of the following specifications from a specimen with a moisture content that meets the requirements. Then perform a dry test. Clamp the ends of the specimen in a pair of movable fixtures on the testing machine so that they are aligned. The center of the specimen should pass through the axis of the movable fixtures. The distance between the clamping point and the specimen notch should be within 5°. Load the specimen at a constant rate to failure. The loading rate is 10 MPa (min). The maximum failure load should be read accurately to the nearest SN.

[0153] Thermal properties test method

[0154] Weigh 3-5 mg of a completely dehydrated dry sample and place it in a test crucible. Heat the sample at a rate of 10°C / min in a flowing N2 environment, with the N2 flow rate controlled within the range of 20-2 mL / min. The temperature rise range is 30°C-800°C, and the sample is analyzed using a thermogravimetric analyzer (TG-DTG).

[0155] Table 1 Determination of phenolic hydroxyl content in lignin

[0156] Example Phenolic hydroxyl / -OH 1 4.114 2 3.622 3 4.217 4 6.678 Comparative Example 1 3,533 Comparative Example 2 2.463

[0157] As shown in Table 1, Example 4 performed best, while Comparative Example 2 performed poorly. The total phenolic hydroxyl content increased significantly after treatment with the Urea (urea) / ZnCl2 (zinc chloride) eutectic ionic liquid. The high phenolic hydroxyl content in Example 4 is beneficial for improving activity. The treated lignin is primarily in the form of phenolic hydroxyl groups, resulting in a higher number of reactive sites.

[0158] Table 2 Plywood bonding strength test method

[0159] Example Bonding strength MPa 1 0.92 2 0.93 3 1.10 4 1.21 Comparative Example 1 0.61 Comparative Example 2 0.48

[0160] As shown in Table 2, Example 4 is the best and Comparative Example 2 is the worst. The plywood prepared in Example 4 has higher bonding strength, and the resin used in the plywood prepared in this example has a more stable structure, improved water resistance, and reduced formaldehyde emission.

[0161] Table 3 Thermal performance measurement

[0162] Example Thermal performance measurement / ℃ 1 90 2 100 3 110 4 130 Comparative Example 1 80 Comparative Example 2 70

[0163] As shown in Table 3, Example 4 is the best and Comparative Example 2 is the worst. The higher temperature in Example 4 exacerbates the consumption of the active groups of the resin itself, releases more heat, and has excellent overall performance. On the contrary, the lower temperature will hinder the curing reaction, resulting in a decrease in the released heat, which cannot be well and evenly aggregated, forming an uneven surface structure, which is detrimental to the bonding strength.

[0164] This specific embodiment is merely an explanation of the present invention and does not limit the present invention. After reading this specification, those skilled in the art can make non-creative modifications to this embodiment as needed, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A production process for ENF-grade impregnated film paper veneer plywood, characterized in that: Including the synthesis of eutectic ionic liquids, purification of lignin, catalytic degradation and purification of lignin by eutectic ionic liquids, preparation of MUF co-condensation resins, preparation of lignin-based adhesives, preparation of dopamethacrylamide (DMA), preparation of CNF / P (HEMA-co-DMA) adhesives, preparation of antibacterial and mildew-proof agent impregnated film paper veneer plywood; Step (1) Synthesis of eutectic ionic liquid First, dry Urea and ZnCl2, mix them in proportion and place them in a conical flask. After the reaction melts, stir them magnetically until they become a colorless and transparent liquid. Step (2) Purification of lignin Industrial alkali lignin is dissolved in water to form a solution of a certain concentration, stirred evenly with a stirrer, and a NaOH solution of an appropriate concentration is added to adjust the pH to a certain range. The solution is stirred continuously until the alkali lignin is completely dissolved. The alkali lignin solution is then centrifuged in a centrifuge, and the precipitate is discarded after centrifugation to obtain a supernatant. Concentrated sulfuric acid is added to the supernatant to adjust the pH to a certain value. The solution is centrifuged again, and the supernatant is discarded after centrifugation to obtain a precipitate. The precipitate is washed with dilute acid adjusted to a certain pH value, stirred evenly, and centrifuged in a centrifuge to obtain a precipitate. The precipitate is placed in an enamel dish and dried in a water bath at a certain temperature. After the surface moisture is completely evaporated, the precipitate is placed in a vacuum drying oven at a certain temperature to obtain chemically purified lignin. Step (3) Urea / ZnCl2 eutectic ionic liquid catalyzes the degradation and purification of alkali lignin According to different solid-liquid ratios, the purified lignin prepared in step (2) is added to the two Urea / ZnCl2 low eutectic ionic liquids prepared in step (1), and the reaction is carried out for different times under temperature conditions. After the reaction, the lignin is purified by an industrial alkaline lignin purification method, and the obtained product is the lignin activated by the Urea / ZnCl2 low eutectic ionic liquid; Step (4) Preparation of MUF cocondensation resin The formaldehyde solution is added to a three-necked flask at once, the pH value is adjusted with sodium hydroxide, and the mixture is stirred and heated to a certain temperature, then kept warm. The pH value of the reaction system is adjusted, and the state of the resin in water at a fixed temperature is measured during the reaction. When the resin becomes cloudy, the pH value is adjusted, and (M) melamine is added in an amount that is an appropriate percentage of the urea quality, and the reaction is carried out at a certain temperature. When the resin is dropped into water and turbidity appears, urea is added, and the reaction is continued at an appropriate temperature. When the resin forms a flocculent precipitate, the temperature is lowered and the pH value is adjusted again to synthesize a MUF (formaldehyde-melamine-urea) co-condensation resin. Step (5) Preparation of lignin-based adhesive First, polyethylene glycol and concentrated sulfuric acid are uniformly mixed under magnetic stirring conditions, and then the activated lignin in step (3) and the mixed solution are placed in a three-necked flask; after the two are uniformly mixed, the three-necked flask containing polyethylene glycol and activated lignin is placed in a pre-heated oil bath for cooking; when the cooking is completed, the oil bath is immediately removed, and the three-necked flask is placed in cold water to quickly lower the temperature to terminate the reaction in the three-necked flask; a dioxane solution is poured into the mixture after the reaction to dissolve the reaction product, and all the reaction products are transferred from the three-necked flask to a funnel for filtration to separate and remove the residue that does not participate in the reaction in the solution, and the residue is washed with the dioxane solution multiple times to ensure that all the liquefied products are dissolved in the solution; Next, the liquefied solution obtained after filtration is evaporated using a rotary evaporator under certain temperature conditions to remove water and dioxane from the solution to obtain a liquefied product. The evaporated liquefied product is then poured into a certain amount of distilled water and subjected to magnetic stirring to separate free polyethylene glycol from the liquefied product and dissolve it in the distilled water to separate it from the obtained precipitate. The stirred mixture is then centrifuged to separate the solution from the precipitate. Finally, the precipitate is removed and vacuum dried to obtain a lignin-based adhesive. Step (6) Preparation of protected dopamethacrylamide (DMA) DOPA (dopamine hydrochloride) was weighed and added to a three-necked flask containing CH2Cl2. The mixture was stirred at room temperature to completely disperse the mixture. TEA (triethylamine) was then added dropwise using a constant pressure separatory funnel. Triethylchlorosilane and TEA were then added dropwise using a constant pressure separatory funnel. The mixture was allowed to react at room temperature for a period of time. Finally, methacryloyl chloride and TEA were added dropwise using a constant pressure separatory funnel. The mixture was allowed to react at room temperature. After the reaction, CH2Cl2 was evaporated to dryness using a rotary evaporator, extracted with ethyl acetate, and unreacted substances were removed with a NaHSO4 solution. The organic layer was washed with a saturated NaCl solution, dried with Na2SO4, and finally concentrated using a rotary evaporator. The protected DMA was purified by column chromatography using a mixture of n-hexane / ethyl acetate as the eluent to obtain a colorless, highly viscous liquid. Step (7) Preparation of CNF / P(HEMA-co-DMA) adhesive The protected DMA, HEMA (hydroxyethyl methacrylate) and AIBN (azobisisobutyronitrile) obtained in step (6) were weighed and added to a round-bottom flask containing ethanol. After a freeze-thaw cycle, nitrogen was injected into the round-bottom flask. The copolymer was copolymerized at a certain temperature for a certain time, and HCl (hydrogen chloride) was used to deprotect the copolymer. The copolymer was then precipitated with ether and filtered. Finally, it was dried under vacuum to obtain a P(HEMA-co-DMA) copolymer. The P(HEMA-co-DMA) copolymer was dissolved in ethanol, and a CNF (cellulose nanofibril) suspension was added to the P(HEMA-co-DMA) copolymer solution, and stirred to obtain a composite adhesive with a CNF concentration. Step (8) Preparation of antibacterial and mildew-proof agent impregnated film paper veneer plywood The fir core board is made according to the finger-jointing process technology of integrated wood, and then the sanded strips are grooved on both sides, and then hot-pressed and glued with lignin-based adhesive. The middle board: CNF / P (HEMA-co-DMA) adhesive is used to make the middle board spliced ​​by a splicing machine to ensure that there is no overlap on the surface after hot-pressing and gluing with the core board. The core board and the middle board are hot-pressed and glued with MUF co-condensation resin, and then repaired by scraping mud. After curing and sanding, the surface is covered with treated veneer, and finally a base material that can be used for covering impregnated film paper is made through the scraping mud, curing and sanding processes; finally, the hot pressing process is carried out, the hot pressing pressure is within a certain range, and hot pressing is carried out after pre-pressing for a period of time; the pre-pressing and hot pressing are repeated until the glue is applied, and the temperature is adjusted within a certain range for the hot pressing time, and the antibacterial and mildew-proof impregnated film paper with the best performance is pressed onto the surface of the base material to obtain the antibacterial and mildew-proof agent impregnated film paper veneer.

2. The process for producing ENF-grade impregnated film paper veneer plywood according to claim 1, characterized in that: Step (1) Synthesis of eutectic ionic liquid First, dry Urea and ZnCl2. Place Urea in a vacuum drying oven at 75-85°C and dry for 10-15 hours. Mix Urea and ZnCl2 in a conical flask at a molar fraction of 10-40% of ZnCl2. The reaction temperature is between 60-100°C. After melting, stir magnetically until it becomes a colorless and transparent liquid.

3. The process for producing ENF-grade impregnated film paper veneer plywood according to claim 2, characterized in that: Step (2) Purification of lignin Industrial alkali lignin is dissolved in water to form a solution with a concentration of 10-15%, and the solution is stirred evenly with a stirrer. An appropriate amount of 10-15% NaOH solution is added to adjust the pH to 10-15, and the solution is stirred continuously until the alkali lignin is completely dissolved. The alkali lignin solution is then centrifuged in a centrifuge, the precipitate is discarded, and the supernatant is taken. 10-15% sulfuric acid is added to the supernatant to adjust the pH to 2-5. The solution is centrifuged again, the supernatant is discarded, and the precipitate is taken. The precipitate is washed with dilute acid with a pH of 2-5, stirred evenly, and centrifuged in a centrifuge to take the precipitate. The precipitate is placed in an enamel dish and dried in a water bath at 40-50°C. After the surface moisture is completely evaporated, the precipitate is placed in a vacuum drying oven at 45-55°C and dried for 12-24 hours to obtain chemically purified lignin.

4. The process for producing ENF-grade impregnated film paper veneer plywood according to claim 3, characterized in that: Step (3) Urea / ZnCl2 eutectic ionic liquid catalyzes the degradation and purification of alkali lignin According to different solid-liquid ratios of 1:20-1:70, the purified lignin prepared in step (2) is added to the Urea / ZnCl2 low eutectic ionic liquid prepared in step (1), and the reaction is carried out at a temperature of 60-100°C for different times of 1h-8h. After the reaction, the lignin is purified by an industrial alkaline lignin purification method, and the obtained product is lignin activated by the Urea / ZnCl2 low eutectic ionic liquid.

5. The process for producing ENF-grade impregnated film paper veneer plywood according to claim 4, characterized in that: Step (4) Preparation of MUF cocondensation resin The formaldehyde solution is added to a three-necked flask at once, and the pH is adjusted to 7.0-8.0 with sodium hydroxide. The flask is stirred and heated to 85-90°C over 30-40 minutes, followed by holding for 55-60 minutes. The pH of the reaction system is adjusted to 4.6-4.

8. During the reaction, the state of the resin in 15-20°C water is measured. When the resin becomes cloudy, the pH is adjusted to 5.0-9.0, and M (melamine) is added at an amount of 5-15% of the urea quality. The reaction is carried out at 60-85°C for 1-2 hours. When the resin becomes cloudy when dropped into water, urea is added, and the reaction is continued at 75-80°C. When the resin forms a flocculent precipitate, the temperature is lowered and the pH is adjusted to 5.0-8.0 to synthesize a MUF (formaldehyde-melamine-urea) co-condensation resin.

6. The process for producing ENF-grade impregnated film paper veneer plywood according to claim 5, characterized in that: Step (5) Preparation of lignin-based adhesive First, polyethylene glycol 350-400 and 1-5% concentrated sulfuric acid are uniformly mixed under magnetic stirring conditions; then the activated lignin in step (3) and the mixed solution are loaded into a 900-1000 mL three-necked flask; after the two are uniformly mixed, the three-necked flask containing polyethylene glycol and activated lignin is placed in an oil bath pot heated in advance at a temperature of 100-170°C for steaming for 1-4 hours; when the steaming is completed, the oil bath pot is immediately removed, and the three-necked flask is placed in cold water to quickly lower the temperature to terminate the reaction in the three-necked flask; a dioxane solution with a volume concentration of 50-100% is poured into the mixture after the reaction to dissolve the reaction product, and all the reaction products are transferred from the three-necked flask to a funnel for filtration to separate and remove the residue that does not participate in the reaction in the solution, and the residue is washed several times with 50-100% dioxane solution to ensure that all the liquefied products are dissolved in the solution; Secondly, the liquefied solution obtained after filtration is evaporated using a rotary evaporator at a temperature of 45-50°C to remove water and dioxane in the solution to obtain a liquefied product. The evaporated liquefied product is then poured into a certain amount of distilled water and magnetically stirred for 1-4 hours to separate the free polyethylene glycol from the liquefied product and dissolve it in distilled water to separate it from the obtained precipitate. The stirred mixture is then centrifuged to separate the solution and the precipitate to obtain a lignin-based adhesive.

7. The process for producing ENF-grade impregnated film paper veneer plywood according to claim 6, characterized in that: Step (6) Preparation of protected dopamethacrylamide (DMA) Weigh 5.0-9.0 g of DOPA (dopamine hydrochloride) and add it to a three-necked flask containing 150-200 mL of CH2Cl2. Stir at room temperature to completely disperse it. Add 3.0-6.6 mL of TEA (triethylamine). Then, use a constant pressure separatory funnel to dropwise add 15.0-17.0 mL of triethylsilane and 10-14.0 mL of TEA. After the addition, react at room temperature for 1-4 hours. Finally, use a constant pressure separatory funnel to dropwise add 1-5 mL of methacryloyl chloride and 5.0-8.0 mL of TEA. The mixture is reacted at room temperature for 10-15 hours. h. After the reaction, CH2Cl2 was evaporated to dryness using a rotary evaporator, extracted with ethyl acetate, and unreacted materials were removed with 1-4 mol / L NaHSO4 solution. The organic layer was washed with saturated NaCl solution and dried with Na2SO4. Finally, the organic solution was concentrated using a rotary evaporator. The protected DMA was purified by column chromatography using a n-hexane / ethyl acetate mixture as the eluent. 12-15 g of a colorless, highly viscous liquid was obtained with a yield of 60-67%.

8. The process for producing ENF-grade impregnated film paper veneer plywood according to claim 7, characterized in that: Step (7) Preparation of CNF / P(HEMA-co-DMA) adhesive 0.40-1 g of the protected DMA obtained in step (6), 1-4 g of HEMA (hydroxyethyl methacrylate) and 160-165 mg of AIBN were weighed and added to a round-bottom flask containing 25-30 mL of ethanol; after 3-6 freeze-thaw cycles, nitrogen was injected into the round-bottom flask; copolymerization was carried out at 65-75°C for 10-14 h, the copolymer was deprotected using 1-3 mol / L HCl (hydrogen chloride), and then the copolymer was precipitated with ether and filtered, and finally vacuum dried at 45-50°C for 10-15 h to obtain P(HEMA-co-DMA) copolymer; the P(HEMA-co-DMA) copolymer was dissolved in 1-3 mL of ethanol, and 0.045-0.512 g of CNF suspension was added to the P(HEMA-co-DMA) copolymer solution and stirred to prepare a composite adhesive with a CNF concentration of 0.1-0.8 wt%.

9. The process for producing ENF-grade impregnated film paper veneer plywood according to claim 8, characterized in that: Step (8) Preparation of antibacterial and mildew-proof agent impregnated film paper veneer plywood The fir core board is manufactured using the finger-jointed process of glulam, then sanded to a thickness tolerance of 0.2-0.5mm. The strips, with a width-to-thickness ratio of 2-5, are double-sided grooved and then hot-pressed with a lignin-based adhesive to ensure the thickness tolerance and surface smoothness of the final product. Middle plate: Use CNF / P (HEMA-co-DMA) adhesive to make the middle plate spliced ​​by the splicing machine to ensure that there is no overlap on the surface after hot pressing and gluing with the core plate, and the gap is 0.5-1mm. The core plate and the middle plate are hot pressed and glued with MUF co-condensation resin, and then scraped and repaired. After curing and sanding, the surface is covered with a veneer with a thickness of 0.8-1mm. Finally, the base material for covering the impregnated film paper is made through the scraping, curing and sanding processes; finally, the hot pressing process is carried out, the hot pressing pressure is 0.1-0.6 MPa, pre-pressing 1-5h, hot pressing 16-20 min, 125-150℃; 0.5-0.8MPa, pre-pressing 0.5-1.0 h, hot pressing 12-15min, after gluing: temperature 118-125℃, hot pressing time 6-8 min, hot pressing pressure 0.7-1.0 MPa; and then pressing the best-performing antibacterial and mildew-proof impregnated film paper onto the surface of the substrate to obtain the antibacterial and mildew-proof agent impregnated film paper veneer plywood.

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