Preparation of high-water-retention peanut meal formaldehyde-free adhesive and application of high-water-retention peanut meal formaldehyde-free adhesive in impregnated bond paper veneer core-board

Abstract

The invention belongs to the technical field of adhesives for artificial boards, and particularly relates to preparation of a high-water-retention peanut meal formaldehyde-free adhesive and application of the high-water-retention peanut meal formaldehyde-free adhesive in impregnated bond paper veneer blockboards. The peanut meal subjected to enzymolysis treatment is used as a main raw material, epoxy hyperbranched hydroxyethyl cellulose is introduced as a water-retaining agent and a cross-linking agent, and inorganic calcium salt is used as a synergistic auxiliary agent, so that the high-water-retention peanut meal formaldehyde-free adhesive is obtained. The high-water-retention formaldehyde-free adhesive prepared by the preparation method disclosed by the invention can be used for remarkably improving the water retention and the bonding strength, prolonging the opening time in a dry environment and effectively improving the pre-pressing forming quality and the water resistance of a plate, and is suitable for the field of manufacturing of green artificial boards.

Description

Technical Field

[0001] The invention relates to a formaldehyde-free adhesive, in particular to the preparation of a high-water-retention peanut meal formaldehyde-free adhesive and its application in impregnated film paper veneer blockboard, belonging to the technical field of adhesives for artificial boards. Background Art

[0002] As demand for indoor environmental protection continues to rise, plant-protein-based adhesives are gaining widespread attention due to their formaldehyde-free, renewable, and biodegradable properties. Peanut meal, a low-cost oil byproduct rich in hydrophobic amino acids and long-chain protein structures, has the potential to serve as a high-performance plant-based adhesive. However, due to its dense natural protein structure and rigid molecular chains, it suffers from poor water solubility and low reactivity. This leads to poor water resistance and unstable bond strength during adhesive preparation, hindering its widespread application, and related research and technology remain limited. Furthermore, the industrial production of board materials typically requires multiple steps, including gluing, forming, cold pressing, core trimming, and hot pressing. Especially in northern regions during winter or in dry climates, where air humidity is low and glue evaporates quickly, the water retention of the adhesive significantly impacts gluing operations, board quality, and production efficiency. Poor adhesive water retention can easily lead to glue drying, resulting in poor pre-pressing formability, decreased hot pressing strength, and ultimately, poor performance and stability of the finished board material. It is particularly noteworthy that there is often a performance conflict between water retention and water resistance in material design: the former requires good affinity and retention of water, while the latter emphasizes the ability of the cross-linked network to resist water erosion, and it is difficult to take both into account.

[0003] For example, patent application CN 119505803A discloses a high-strength, high-water-retention soybean meal-based adhesive and its preparation method. The adhesive primarily comprises soybean protein meal, glucose oxidase, calcium sulfate oligomers, ethylene glycol diglycidyl ether, and water. While this adhesive addresses the conflict between bonding strength and water retention, its water resistance still needs improvement.

[0004] Therefore, there is an urgent need to develop a plant protein-based adhesive that has good water retention capacity, adapts to the industrial sizing rhythm, has excellent water-resistant bonding strength, and is suitable for green artificial board application scenarios, so as to promote its application in actual production. Summary of the Invention

[0005] The present invention addresses the above-mentioned issues and provides a highly water-retaining, formaldehyde-free peanut meal adhesive. This adhesive uses peanut meal as its primary protein source. Enzymatic hydrolysis mildly degrades the protein to enhance reactivity. Epoxy hyperbranched hydroxyethyl cellulose is introduced as a water-retaining agent and crosslinker to construct a three-dimensional crosslinked network. Furthermore, an inorganic calcium salt is introduced to facilitate ionic crosslinking and water-retention regulation, thereby simultaneously enhancing the adhesive's water retention and bonding strength.

[0006] The technical solutions of the present invention for solving the above problems are as follows:

[0007] A high water-retention peanut meal formaldehyde-free adhesive, comprising peanut meal dry powder and a cross-linking agent:

[0008] The peanut meal powder is prepared by treating peanut meal with cellulase and protease in sequence to obtain an enzymatic hydrolysate, and then drying the enzymatic hydrolysate;

[0009] The cross-linking agent is epoxy hyperbranched hydroxyethyl cellulose;

[0010] By mass, 20 to 40 parts of peanut meal dry powder and 4 to 6 parts of cross-linking agent.

[0011] In the above technical solution of the present invention, the structural formula of epoxy hyperbranched hydroxyethyl cellulose is generally as follows:

[0012]

[0013] Among them, R1=H or CH2CH2OH, R2=C2~C5.

[0014] As a preferred embodiment of the above technical solution, the adhesive further includes 60 to 80 parts by mass of water.

[0015] As a preferred embodiment of the above technical solution, the adhesive further includes 10 to 15 parts by mass of an inorganic calcium salt.

[0016] As a preferred embodiment of the above technical solution, the amount of the cellulase is 0.4-0.6wt% of the mass of the peanut meal; the protease is trypsin, and the amount is 0.1-0.3wt% of the mass of the peanut meal.

[0017] As a preferred embodiment of the above technical solution, the peanut meal has a mesh size of 150 to 200 meshes, a crude protein content of ≥47%, a moisture content of ≤12%, and an oil content of ≤2%.

[0018] Peanut meal usually has a high residual oil content, which can have negative effects if used directly. Therefore, in the above technical solution of the present invention, peanut meal with an oil content of ≤2% is selected, or the peanut meal is further de-oiled to control the oil content to ≤2%.

[0019] As a preferred embodiment of the above technical solution, the inorganic calcium salt is selected from at least one of calcium chloride, calcium phosphate, calcium phosphate and calcium sulfate.

[0020] As a preferred embodiment of the above technical solution, the epoxy hyperbranched hydroxyethyl cellulose is obtained by esterifying a hyperbranched polyhydroxy intermediate with hydroxyethyl cellulose to obtain hyperbranched hydroxyethyl cellulose, and then epoxidizing the hyperbranched hydroxyethyl cellulose with a difunctional epoxy ether substance.

[0021] As a preferred embodiment of the above technical solution, the preparation method of the epoxy hyperbranched hydroxyethyl cellulose comprises the following steps:

[0022] S1. Mix 100 parts by mole of maleic anhydride and 90 to 150 parts by mole of pentaerythritol, and stir continuously for at least 1 hour at 60 to 90° C. under an inert atmosphere to obtain a polyhydroxy intermediate;

[0023] S2, then adding 10 to 30 molar parts of hydroxyethyl cellulose, reacting at 90 to 120° C., and after the reaction, precipitating with a first organic solvent having a polarity between toluene and ethyl acetate, and drying to obtain hyperbranched hydroxyethyl cellulose;

[0024] S3. Add 20 parts of hyperbranched hydroxyethyl cellulose and 10 to 15 parts by mole of a difunctional epoxy ether into 200 to 500 parts of a second organic solvent having a polarity not less than acetone, and stir continuously for at least 2 hours at 90 to 120° C. under an inert atmosphere; after the reaction, precipitate with a third organic solvent having a polarity between toluene and ethyl acetate, and dry to obtain epoxy hyperbranched hydroxyethyl cellulose.

[0025] As a preferred embodiment of the above technical solution, the bifunctional epoxy ether substance is at least one selected from polypropylene glycol diglycidyl ether, 1,4-butanediol glycidyl ether, ethylene glycol diglycidyl ether, and neopentyl glycol diglycidyl ether.

[0026] Another object of the present invention is to provide an application of the adhesive.

[0027] The technical solution is as follows:

[0028] The application of the high water-retention peanut meal formaldehyde-free adhesive in impregnated film paper veneer blockboard comprises the following steps:

[0029] Step 1: Glue the poplar board core with a glue amount of 220g / m 2 After applying the glue, eucalyptus or poplar veneers are glued together to form a slab. The slab is cold-pressed at a unit pressure of 0.6MPa for 40 minutes, and then hot-pressed in a three-stage hot press to produce the substrate. The specific hot press parameters are: first stage unit pressure of 0.65-0.6MPa, holding pressure for 540s, second stage unit pressure of 0.5-0.4MPa, holding pressure for 180s, and third stage unit pressure of 0.3-0.25MPa, holding pressure for 420s.

[0030] Step 2: After the substrate has been sawed, scraped, cured, and sanded, it is glued for the second time and then laminated with the ultra-thin fiberboard. The ultra-thin fiberboard has a high density and strong covering power, which can ensure the quality of the board surface and enhance the surface's crack resistance. The second glue is also made of high-water-retention peanut meal formaldehyde-free adhesive, with a glue coating amount of 200g / m 2 The hot-pressing and cold-pressing parameters are the same as before. After sanding and sawing, the finished board is pressed with impregnated adhesive film paper. The hot-pressing temperature is 120-130°C, the unit pressure is 0.6-0.8 MPa, and the hot-pressing time is 420-540 seconds. The final product is the impregnated adhesive film paper veneer blockboard.

[0031] The present invention provides a high-water-retention peanut meal formaldehyde-free adhesive. This method first gently treats peanut meal protein through enzymatic hydrolysis. This mild enzymatic hydrolysis selectively breaks hydrogen bonds and partially hydrophobic structures within the protein molecules, degrading them into structures such as polypeptides, polypolypeptides, and oligopeptides. This releases more active groups, improves reactivity, and lays the foundation for subsequent cross-linking reactions. Furthermore, compared to traditional alkaline chemical treatments, this enzymatic hydrolysis method avoids problems such as excessive protein degradation and ammonia release caused by over-hydrolysis, effectively improving the environmental friendliness and processing safety of the adhesive.

[0032] The present invention uses hydroxyethyl cellulose as the structural "core" and connects polyhydroxy intermediates as "branches" through esterification reaction to synthesize hyperbranched hydroxyethyl cellulose with a highly branched structure. This structure is rich in reactive hydroxyl groups and chain end sites, exhibiting good moisture retention and flexibility, thereby extending the open time in a dry environment and avoiding slab pre-pressing failure.

[0033] The epoxidized hyperbranched hydroxyethyl cellulose provided by this invention can covalently bond with amino and carboxyl groups in enzymatically hydrolyzed peanut meal protein molecules, forming a highly cross-linked three-dimensional network structure, significantly improving bonding strength. Its multi-branched structure also exhibits excellent interfacial adaptability, allowing it to fully spread across the wood surface during the pre-pressing stage, effectively improving pre-pressing performance and enhancing interfacial adhesion.

[0034] The present invention also introduces inorganic calcium salt as a synergistic crosslinking agent. On the one hand, calcium ions are used to crosslink with the active groups in the enzymatic protein structure and epoxy hyperbranched hydroxyethyl cellulose. 2+ -O" coordination bonds form ionic crosslinks, reinforcing the covalent crosslinking network based on hydroxyl-amino and hydroxyl-carboxyl groups to form a dual crosslinking system, improving the density and crosslinking degree of the overall structure; on the other hand, calcium salts can adjust the colloid's water content, delaying water migration and synergistically improving water retention. The interface between calcium ions and wood can also enhance interfacial adsorption and mechanical bite effects, further improving pre-compression adhesion.

[0035] In summary, the present invention has the following beneficial effects:

[0036] 1. The present invention uses peanut meal, a byproduct of plant protein, as the main raw material. It is widely available, renewable, and economical. Compared with low-temperature soybean meal commonly used in plant protein adhesives, the raw material cost can be reduced by about 2,000 yuan / ton, which has a significant cost advantage, helps reduce overall production costs, and improves the feasibility and promotion of industrial applications.

[0037] 2. The present invention uses an enzymatic hydrolysis process to activate peanut meal protein. Compared with the traditional alkaline hydrolysis method, the enzymatic hydrolysis process conditions are mild and the amount of enzyme added is small, which can effectively avoid excessive degradation of protein structure and the release of harmful gases such as ammonia, thereby improving the environmental friendliness and industrial operation safety of the adhesive;

[0038] 3. The present invention uses hydroxyethyl cellulose as the basic raw material, which is rich in hydrophilic groups in its structure and has good water absorption and water retention capabilities. After hyperbranching and epoxidation modification, the reactivity with the active groups in the enzymatic protein is improved, and the "hooking" ability in the microstructure of the wood surface is enhanced. It can form a stable three-dimensional network in the colloid, improving the water resistance of the adhesive. At the same time, it can also effectively extend the opening time and reduce the risk of pre-pressing failure.

[0039] 4. The present invention introduces inorganic calcium salt as a synergistic additive in the formula to form "Ca 2+ -O" coordination structure, constructing an ionic-covalent synergistic cross-linking network to improve the structural density of the colloid; it can also adjust the colloid's water content, delay water migration, and enhance water retention; it interacts with the carboxyl structure or micropores on the wood surface, enhancing interfacial affinity and micro-mechanical bite, further improving pre-compression adhesion. DETAILED DESCRIPTION

[0040] This specific implementation is merely an explanation of the present invention and is not intended to limit the present invention. Any changes made by those skilled in the art after reading the specification of the present invention will be protected by patent law as long as they are within the scope of the claims.

[0041] Example 1

[0042] A high-water-retention peanut meal formaldehyde-free adhesive is composed of the following components in parts by weight: 25 parts of peanut meal dry powder, 60 parts of water, 10 parts of calcium phosphate, and 5 parts of epoxy hyperbranched hydroxyethyl cellulose.

[0043] The peanut meal enzymatic hydrolysate dry powder is prepared by a method comprising the following steps:

[0044] Add about 3 / 5 volume of water to a 100L industrial reactor, heat to 40°C, set the stirring speed to 120rpm, add 5kg of peanut meal powder passed through a 150-mesh sieve while stirring, add 30g of cellulase for enzymatic hydrolysis for 0.5 hour, then add 10g of trypsin and continue enzymatic hydrolysis for 0.5 hour to obtain an enzymatic hydrolyzate, and after drying, obtain about 2.5kg (25 parts) of the peanut meal dry powder.

[0045] The epoxy hyperbranched hydroxyethyl cellulose is prepared by a method comprising the following steps:

[0046] S1. Add 3.8 kg of maleic anhydride and 5.0 kg of pentaerythritol to a 10 L industrial reactor, mix, and continuously stir for 2 h under a nitrogen atmosphere at 75 ° C to obtain a polyhydroxy intermediate. The reaction mechanism is as follows:

[0047] For the convenience of expression, the polyhydroxy intermediate is represented as follows:

[0048]

[0049] S2. Then, 0.3 kg of hydroxyethyl cellulose was added and reacted at 100°C for 2 h. The resulting solution was precipitated with ether and dried in a vacuum oven at 45°C for 48 h to obtain about 0.46 kg of hyperbranched hydroxyethyl cellulose. The reaction mechanism is as follows:

[0050]

[0051] Wherein, R1=H or CH2CH2OH;

[0052] S3. In a 20 L industrial reactor, 0.46 kg of hyperbranched hydroxyethyl cellulose and 0.35 kg of ethylene glycol diglycidyl ether were added to 7.8 L of dimethyl sulfoxide, and the mixture was stirred continuously for 6 h under a nitrogen atmosphere at 95 ° C. The resulting solution was precipitated with ether and dried in a vacuum oven at 45 ° C. for 48 h to obtain about 0.5 kg (5 parts) of epoxy hyperbranched hydroxyethyl cellulose. The reaction mechanism is roughly as follows:

[0053]

[0054] Wherein, R1=H or CH2CH2OH.

[0055] The calcium phosphate was passed through a 600-mesh sieve and 1.0 kg (10 parts) was taken.

[0056] The high water-retention peanut meal formaldehyde-free adhesive is prepared by a method comprising the following steps:

[0057] The above 25 parts of peanut meal dry powder, 60 parts of water, 10 parts of calcium phosphate and 5 parts of epoxy hyperbranched hydroxyethyl cellulose are mixed evenly to obtain a high water-retaining peanut meal formaldehyde-free adhesive.

[0058] Example 2

[0059] A high water-retention peanut meal formaldehyde-free adhesive is different from Example 1 in that the amount of epoxy hyperbranched hydroxyethyl cellulose used is 0.4 kg (4 parts).

[0060] Example 3

[0061] A high water-retention peanut meal formaldehyde-free adhesive is different from Example 1 in that the amount of epoxy hyperbranched hydroxyethyl cellulose used is 0.6 kg (6 parts).

[0062] The adhesives of Examples 1 to 3 were used to prepare three corresponding impregnated adhesive film paper facing blockboards. The details are as follows:

[0063] Step 1: Glue the poplar board core with a glue amount of 220g / m 2 The glue used was the high-water-retention peanut meal formaldehyde-free adhesive prepared in Examples 1-3 above. After applying the glue, poplar veneers were glued together to form slabs. The slabs were cold-pressed at a unit pressure of 0.6 MPa for 40 minutes, and then hot-pressed under a three-stage hot press to produce the substrate. The specific hot press parameters were: first stage unit pressure of 0.65-0.6 MPa, holding pressure for 540 seconds, second stage unit pressure of 0.5-0.4 MPa, holding pressure for 180 seconds, and third stage unit pressure of 0.3-0.25 MPa, holding pressure for 420 seconds.

[0064] Step 2: After the substrate has been sawed, scraped, cured, and sanded, it is subjected to secondary gluing and laminated to the ultra-thin fiberboard. The secondary gluing also uses the high water-retention peanut meal formaldehyde-free adhesive prepared in Examples 1 to 3 above; the glue coating amount is 200g / m 2 The hot-pressing and cold-pressing parameters are the same as before. After sanding and sawing, the finished board is pressed with impregnated paper. The hot-pressing temperature is 120-130°C, the unit pressure is 0.6-0.8 MPa, and the hot-pressing time is 420-540 seconds. The finished board is impregnated with paper.

[0065] The immersion peeling properties of the corresponding specimens of Examples 1 to 3 were tested according to the method specified in GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels". The test results are shown in Table 1.

[0066] Table 1 Immersion stripping performance results of Examples 1 to 3

[0067] Example 1 Example 2 Example 3 Type III immersion stripping qualified qualified qualified Type II immersion stripping qualified qualified qualified

[0068] As shown in the table above, the eco-friendly boards prepared using the adhesive of the present invention in Examples 1-3 all passed both the Type III and Type II immersion peel tests, demonstrating that the adhesive of the present invention exhibits excellent bonding properties to wood and imparts excellent adaptability to humid environments. Given that the addition amount consistently meets performance requirements, Example 2, with 4 parts of epoxy hyperbranched hydroxyethyl cellulose, was selected as the optimal addition amount.

[0069] Comparative Example 1

[0070] A formaldehyde-free adhesive is different from Example 2 in that no calcium phosphate is added to the adhesive.

[0071] Comparative Example 2

[0072] A formaldehyde-free adhesive is different from Example 2 in that epoxy hyperbranched hydroxyethyl cellulose is not added to the adhesive.

[0073] The adhesives of Example 2 and Comparative Examples 1 and 2 were used to prepare three corresponding eco-boards. The details are as follows:

[0074] Step 1: Glue the poplar board core with a glue amount of 220g / m 2 The adhesive used was the adhesive prepared in Example 2 and Comparative Examples 1-2. After applying the adhesive, poplar veneers were glued together to form a slab. The slab was cold-pressed at a unit pressure of 0.6 MPa for 40 minutes, and then hot-pressed under a three-stage hot-pressing process to produce a substrate. The specific hot-pressing parameters were: first stage unit pressure of 0.65-0.6 MPa, holding pressure for 540 seconds, second stage unit pressure of 0.5-0.4 MPa, holding pressure for 180 seconds, and third stage unit pressure of 0.3-0.25 MPa, holding pressure for 420 seconds.

[0075] Step 2: After the substrate has been sawed, scraped, cured, and sanded, a second adhesive is applied to the substrate and the upper and lower surfaces are bonded to the ultra-thin fiberboard. The second adhesive is also applied using the adhesive prepared in Example 2 and Comparative Examples 1-2; the amount of adhesive applied is 200 g / m 2 The hot-pressing and cold-pressing parameters are the same as before. After sanding and sawing, the finished board is pressed with impregnated paper. The hot-pressing temperature is 120-130°C, the unit pressure is 0.6-0.8 MPa, and the hot-pressing time is 420-540 seconds. The finished board is impregnated with paper.

[0076] According to the method specified in GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels", the immersion and peeling properties of the corresponding test pieces of Example 2 and Comparative Examples 1 and 2 were tested, and the drying time and pre-pressing effect were compared. The test results are shown in Table 2.

[0077] Table 2 Performance test results of Example 2 and Comparative Examples 1-2

[0078] Example 2 Comparative Example 1 Comparative Example 2 Type III immersion stripping qualified qualified Unqualified Type II immersion stripping qualified Unqualified Unqualified Drying time / min 75 55 40 Pre-pressing No delamination, good forming Local delamination and poor molding Complete delamination and poor molding

[0079] As can be seen from Table 2 above, Example 2 passed both the Class III and Class II immersion peeling tests, indicating that the adhesive prepared by the present invention still has strong peeling resistance under high temperature boiling conditions.

[0080] Although Comparative Example 1 (without the addition of calcium phosphate) passed the Class III test, it failed under the more stringent Class II conditions, indicating that calcium salt has a synergistic enhancement effect in the cross-linked network. Its introduction helps to build a denser ionic-covalent double cross-linked structure, thereby improving water resistance and cross-linking stability.

[0081] Comparative Example 2 (without epoxy hyperbranched hydroxyethyl cellulose) failed both Type II and Type III immersion peel tests, demonstrating that epoxy hyperbranched hydroxyethyl cellulose plays a key role in improving the bond strength and wet stability between the protein glue and wood. Its multi-branched structure not only increases the number of reactive sites with the protein molecules, increasing the crosslink density, but also improves interfacial adaptability and flexibility.

[0082] In terms of drying time and pre-pressing performance, Example 2 achieved a drying time of 75 minutes, significantly outperforming Comparative Example 1 (55 minutes) and Comparative Example 2 (40 minutes). This effectively extended the open time, meeting the requirements for sizing and embryo formation in actual production. Furthermore, the pre-pressing performance was excellent, with no delamination, demonstrating excellent water retention and initial adhesion. Comparative Example 2, on the other hand, exhibited complete delamination and poor forming, further demonstrating the significant contribution of hydroxyethyl cellulose in slowing moisture migration and improving interfacial adhesion.

[0083] In summary, epoxy hyperbranched hydroxyethyl cellulose and inorganic calcium salt in the present invention respectively play a synergistic role in enhancing cross-linking, improving water retention, improving interfacial adhesion and molding effects, significantly improving the overall performance of the adhesive, and are the key to achieving the high water retention capacity of the present invention.

Claims

1. A high water-retention peanut meal formaldehyde-free adhesive comprising peanut meal dry powder and a cross-linking agent, characterized in that: The peanut meal dry powder is prepared by treating peanut meal with cellulase and protease in sequence to obtain an enzymatic hydrolysate, and then drying the enzymatic hydrolysate; The cross-linking agent is epoxy hyperbranched hydroxyethyl cellulose; By mass, 20-40 parts of peanut meal powder and 4-6 parts of cross-linking agent.

2. The high water-retention peanut meal formaldehyde-free adhesive according to claim 1, characterized in that: The adhesive further comprises 60 to 80 parts by mass of water.

3. A high water retention peanut meal formaldehyde-free adhesive according to claim 1 or 2, characterized in that: The adhesive further comprises 10 to 15 parts by mass of an inorganic calcium salt.

4. A high water-retention peanut meal formaldehyde-free adhesive according to claim 1 or 2, characterized in that: The amount of the cellulase used is 0.4-0.6 wt% of the peanut meal mass; the protease is trypsin, and the amount of the protease used is 0.1-0.3 wt% of the peanut meal mass.

5. A high water-retention peanut meal formaldehyde-free adhesive according to claim 1 or 2, characterized in that: The peanut meal has a mesh size of 150-200 meshes, a crude protein content of ≥47%, a moisture content of ≤12%, and an oil content of ≤2%.

6. A high water-retention peanut meal formaldehyde-free adhesive according to claim 1 or 2, characterized in that: The inorganic calcium salt is selected from at least one of calcium chloride, calcium phosphate, calcium phosphate and calcium sulfate.

7. The high water-retention peanut meal formaldehyde-free adhesive according to claim 1 or 2, characterized in that: The epoxy hyperbranched hydroxyethyl cellulose is obtained by subjecting a hyperbranched polyhydroxy intermediate to an esterification reaction with hydroxyethyl cellulose to obtain the hyperbranched hydroxyethyl cellulose, and then subjecting the hyperbranched hydroxyethyl cellulose to an epoxidation reaction with a difunctional epoxy ether substance.

8. The high water-retention peanut meal formaldehyde-free adhesive according to claim 7, characterized in that: The preparation method of the epoxy hyperbranched hydroxyethyl cellulose comprises the following steps: S1. Mix 100 parts by mole of maleic anhydride and 90 to 150 parts by mole of pentaerythritol, and stir continuously for at least 1 hour at 60 to 90° C. under an inert atmosphere to obtain a polyhydroxy intermediate; S2, then adding 10 to 30 molar parts of hydroxyethyl cellulose, reacting at 90 to 120° C., and after the reaction, precipitating with a first organic solvent having a polarity between toluene and ethyl acetate, and drying to obtain hyperbranched hydroxyethyl cellulose; S3. Add 20 parts of hyperbranched hydroxyethyl cellulose and 10-15 parts by mole of a difunctional epoxy ether into 200-500 parts of a second organic solvent having a polarity not less than acetone, and stir continuously for at least 2 hours at 90-120° C. under an inert atmosphere; after the reaction, precipitate with a third organic solvent having a polarity between toluene and ethyl acetate, and then dry to obtain epoxy hyperbranched hydroxyethyl cellulose.

9. The high water-retention peanut meal formaldehyde-free adhesive according to claim 8, characterized in that: The bifunctional epoxy ether substance is selected from at least one of polypropylene glycol diglycidyl ether, 1,4-butanediol glycidyl ether, ethylene glycol diglycidyl ether, and neopentyl glycol diglycidyl ether.

10. Use of the high water-retention peanut meal formaldehyde-free adhesive according to any one of claims 1 to 9 in impregnated plastic film paper facing blockboard.

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