Formaldehyde-free water-resistant soybean meal-based composite adhesive and preparation process of formaldehyde-free water-resistant soybean meal-based composite adhesive in multifunctional artificial board

Abstract

The invention discloses a formaldehyde-free water-resistant soybean meal-based composite adhesive and a preparation process of the formaldehyde-free water-resistant soybean meal-based composite adhesive on a multifunctional artificial board, and relates to the technical field of bio-based adhesives and wood processing. The adhesive is prepared from a soybean meal main raw material, a plant-based composite cross-linking system, a nano-mineral synergistic reinforcing phase, an interface regulating agent and a compound curing agent through a two-stage mixing technology, and the problems that a traditional soybean meal adhesive is poor in water resistance, uneven in dispersion, limited in applicable plate type, single in function and the like are solved. The obtained adhesive is free of formaldehyde release, the prepared artificial board (multilayer plywood, shaving board, fiberboard and the like) is free of glue failure after being boiled in boiling water for 2 h, the normal water absorption rate is smaller than or equal to 8%, the dry static bending intensity is larger than or equal to 15 MPa, meanwhile, the antibacterial rate is larger than or equal to 90%, the technology is compatible with an existing production line, the cost is reduced by 30%-40% compared with a traditional PAE type adhesive, and the adhesive is suitable for industrial production. The composite board can be widely applied to the fields of boards for furniture manufacturing, indoor decoration and humid environments.

Description

Technical Field

[0001] This invention relates to the field of bio-based adhesives and wood processing technology, specifically to a formaldehyde-free, water-resistant soybean meal-based composite adhesive and its application in the preparation process of multifunctional engineered wood panels. Background Technology

[0002] As a vital foundational industry of the national economy, the engineered wood products industry is widely used in furniture manufacturing, interior decoration, building decoration, and packaging, playing a significant role in improving the utilization rate of wood resources and promoting the development of green building materials. However, for a long time, engineered wood production has relied excessively on formaldehyde-containing synthetic adhesives such as urea-formaldehyde resin and phenolic resin. These adhesives continuously release free formaldehyde during the use of the boards, with a release period of 3-15 years, causing serious pollution to indoor air quality and becoming an "invisible killer" that endangers human health.

[0003] Soybean meal, a byproduct of soybean oil processing, boasts significant advantages such as abundant supply, low price, and renewability. With a protein content exceeding 45%, its molecular structure is rich in active functional groups such as hydroxyl, amino, and carboxyl groups, possessing the natural potential to construct adhesive networks through chemical modification. This makes it an ideal bio-based raw material to replace traditional aldehyde-containing adhesives. While some progress has been made in the research and development of soybean meal-based adhesives in recent years, numerous technical bottlenecks remain to be overcome in practical applications.

[0004] From a performance perspective, unmodified soybean meal adhesives rely primarily on weak interactions such as hydrogen bonds between molecules, resulting in low cross-linking density and extremely poor water resistance. In humid environments or under boiling conditions, the adhesive layer easily swells and delaminates. Its normal water absorption rate often exceeds 15%, and noticeable stratification occurs after just one hour of boiling in water, making it unsuitable for use in damp environments such as bathrooms and kitchens. Furthermore, soybean meal protein is prone to agglomeration during processing due to moisture absorption, leading to uneven adhesive dispersion and fluctuations in the mechanical properties of the boards. The dry static bending strength is often below 12 MPa, and the internal bonding strength is less than 0.5 MPa, failing to meet the quality standards for furniture-grade boards.

[0005] In terms of application scope, existing soybean meal adhesives are mostly limited to single-board types such as plywood, exhibiting poor compatibility with different structural engineered wood products such as particleboard and fiberboard. This is mainly because the morphology of wood units (veneer, wood chips, and fibers) varies greatly among different boards, resulting in different requirements for adhesive flowability and penetration. Traditional soybean meal adhesives lack targeted interface control mechanisms, making it difficult to achieve effective bonding with different wood materials. Furthermore, existing products have limited functionality and generally lack additional properties such as antibacterial and anti-mildew properties, restricting their application in high-end fields such as children's furniture and medical and health care.

[0006] Although existing technologies attempt to improve performance by adding chemical crosslinking agents and nanofillers, significant drawbacks remain: some modifiers introduce toxic components, violating environmental protection principles; a single reinforcing phase struggles to balance water resistance and mechanical properties; the mixing process is simplistic and inefficient, failing to address the issue of soybean meal particle agglomeration; and the modification process is complex and costly, hindering industrial-scale production. Therefore, developing a soybean meal-based composite adhesive that combines formaldehyde-free environmental friendliness, excellent water resistance, broad board compatibility, and multifunctional properties is crucial to overcoming the industry's development bottlenecks. Summary of the Invention

[0007] To address the problems of existing soybean meal adhesives, such as formaldehyde release risk, insufficient water resistance, poor dispersibility, limited applicable board types, and single function, this invention provides a formaldehyde-free, water-resistant soybean meal-based composite adhesive, its preparation method, and its application. Through synergistic formulation design and process innovation, the adhesive achieves formaldehyde-free, high water resistance, strong compatibility, and multifunctional properties.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is: a formaldehyde-free, water-resistant soybean meal-based composite adhesive, which is composed of the following components by weight: 30-40 parts soybean meal, 20-30 parts soybean flour, 10-30 parts plant-based composite crosslinking agent, 20-40 parts nano-mineral synergistic reinforcing phase, 2-8 parts interface regulator, 3-8 parts compound curing agent, 30-60 parts deionized water, and 5-10 parts hydroxyethyl methyl cellulose;

[0009] The plant-based composite crosslinking agent is a compound of epoxidized soybean oil and sodium alginate, with a mass ratio of (2-5):1.

[0010] The nano-mineral synergistic reinforcing phase is a composite powder of nano-silica, nano-cellulose, sodium bentonite and modified diatomite, with a mass ratio of 1:(1-3):(2-4):(2-4).

[0011] Furthermore, the interface regulator is γ-aminopropyltriethoxysilane;

[0012] The compound curing agent is a mixture of ammonium chloride and aluminum citrate, with a mass ratio of (1-3):1;

[0013] The formaldehyde-free, water-resistant soybean meal-based composite adhesive also includes 1-5 parts of a pH adjuster, wherein the pH adjuster is sodium carbonate or sodium bicarbonate, used to adjust the pH value of the adhesive system to 8-10.

[0014] Furthermore, the soybean meal has a protein content of ≥45% and a particle size of 80-120 mesh;

[0015] The modified diatomaceous earth was activated by 3,3'-thiobis-1-propene at an activation temperature of 15-45℃ and a pH ≥ 3.0.

[0016] A method for preparing a formaldehyde-free, water-resistant soybean meal-based composite adhesive includes the following steps:

[0017] S1. Premixed masterbatch: Add 20-25 parts of soybean meal, 5-10 parts of hydroxyethyl methyl cellulose, and 3-8 parts of compound curing agent to a double-motion mixer, mix at 25-35℃ for 20-30 minutes, pass through a 100-mesh sieve, seal and mature for 24 hours to obtain premixed masterbatch.

[0018] S2. Mixing of main ingredients: Add the remaining soybean meal and 20-30 parts of soybean flour to a dual-motion mixer in sequence, stir for 10-15 minutes, then add the premixed master powder and continue stirring for 15-20 minutes; then add 10-30 parts of plant-based composite crosslinking agent and 20-40 parts of nano-mineral synergistic reinforcing phase, and circulate and stir at 360° for 60-90 minutes.

[0019] S3. Modification reaction: Add 2-8 parts of interface regulator, 1-5 parts of pH adjuster and 30-60 parts of deionized water to the mixed system, heat to 60-70℃, stir for 60-90 min, cool to room temperature to obtain formaldehyde-free water-resistant soybean meal-based composite adhesive.

[0020] Furthermore, the stirring rate of the dual-motion mixer in S2 is 300-500 r / min, and a scraper is provided on the inner wall of the cylinder to prevent the raw materials from sticking to the wall;

[0021] The solid content of the reaction system in S3 is controlled to be 20-35%.

[0022] A formaldehyde-free multifunctional engineered wood panel is made of at least two layers of veneer or wood units bonded together with a formaldehyde-free, water-resistant soybean meal-based composite adhesive.

[0023] The formaldehyde-free multifunctional engineered wood panels include multi-layer plywood, particleboard, fiberboard, blockboard, or solid wood composite flooring.

[0024] The amount of glue applied to the veneer or wood unit is 150-250 g / m². 2 The hot pressing process parameters are: hot pressing temperature 120-150℃, hot pressing pressure 1.0-3.0MPa, and hot pressing time 30-60s / mm.

[0025] Furthermore, the veneer is poplar veneer, pine veneer, eucalyptus veneer, or hardwood veneer, with a thickness of 0.5-3mm and a moisture content of 8-12%;

[0026] The wood unit comprises wood shavings, fibers, or plywood core strips, with a moisture content of 8-12%.

[0027] The application of formaldehyde-free, water-resistant soybean meal-based composite adhesive in the production of engineered wood products is characterized by its use in adhesives to improve the formaldehyde-free environmental performance, water resistance, mechanical properties, and antibacterial properties of engineered wood products. It is suitable for furniture manufacturing, interior decoration, humid environments, and children's products.

[0028] The soybean meal and soybean flour of the present invention, with soybean meal as the main binder, provide the protein cross-linking network framework; soybean flour helps to improve the flowability and film-forming properties of the adhesive, and the two work together to improve the basic bonding performance of the adhesive.

[0029] The plant-based composite crosslinking agent of this invention involves the ring-opening reaction between epoxidized soybean oil (containing epoxy groups) and the amino and hydroxyl groups of soybean meal protein to form chemical crosslinks; sodium alginate (a natural polysaccharide) binds to protein molecules through hydrogen bonds, synergistically improving the crosslinking density and toughness, and avoiding the toxicity risks of traditional chemical crosslinking agents.

[0030] The nano-mineral synergistic reinforcing phase described in this invention consists of nano-silica filling to enhance the rigidity and water resistance of the adhesive layer; nano-cellulose (rich in hydroxyl groups) forming a hydrogen bond network with protein to improve mechanical properties; sodium-based bentonite (layered structure) locking in free water through cation exchange to reduce hydrolysis; and modified diatomaceous earth (porous structure) adsorbing impurities and enhancing interfacial bonding. These four components synergistically construct a "rigid-tough-water-resistant" composite structure.

[0031] The interface regulator described in this invention, γ-aminopropyltriethoxysilane (KH-550), reacts with one end of the nano-mineral phase and binds to the protein matrix at the other end, thereby improving interfacial compatibility and solving the problem of uneven dispersion of the reinforcing phase.

[0032] The compound curing agent described in this invention uses ammonium chloride to accelerate curing at room temperature and aluminum citrate to promote cross-linking reaction under hot pressing conditions. The dual curing system balances curing efficiency and water resistance.

[0033] The pH adjuster described in this invention, sodium carbonate or sodium bicarbonate, adjusts the pH of the system to 8-10, promotes the swelling and expansion of soybean meal protein, and enhances the reactivity.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] 1. Formaldehyde-free and environmentally friendly: The entire system uses bio-based raw materials and formaldehyde-free additives, with a formaldehyde release of 0mg / m³, meeting the ENF environmental protection standard and suitable for sensitive areas such as children's furniture and interior decoration.

[0036] 2. Excellent water and boiling resistance: Through plant-based cross-linking and nano-mineral synergistic reinforcement, the adhesive forms a dense network after curing. The artificial board does not delaminate after boiling in water for 2 hours. The normal water absorption rate is ≤8%, and the thickness expansion rate after 24 hours of water absorption is ≤30%, which meets the requirements of Class I waterproof boards.

[0037] 3. Excellent mechanical properties: Dry static bending strength ≥15MPa, internal bonding strength ≥0.7MPa, elastic modulus ≥2700MPa, with mechanical properties superior to traditional soybean meal adhesive boards.

[0038] 4. Multifunctional characteristics: The synergistic effect of nano-reinforced phase and mineral filler gives the board antibacterial properties, with an antibacterial rate of ≥90% against Escherichia coli and Staphylococcus aureus; plant-based raw materials improve biodegradability, resulting in less environmental impact after disposal.

[0039] 5. Strong process adaptability: The two-stage mixing process solves the problem of soybean meal agglomeration, the adhesive viscosity is stable (800-4500mPa・s), and the coating uniformity is good; the hot pressing process is compatible with existing production lines and does not require large-scale equipment modification.

[0040] 6. Cost advantage: The main raw materials are by-products of grain and oil, and the cost of modified additives is 30-40% lower than that of PAE type adhesives, making it suitable for large-scale industrial production. Attached Figure Description

[0041] Figure 1 This is an electron microscope image showing the microstructure of a traditional soybean meal adhesive.

[0042] Figure 2 The microstructure electron microscope image of the adhesive of the present invention: nano-mineral phase uniformly embedded in a protein network to form a dense "brick-mud" structure.

[0043] Figure 3 This is a flow chart of a two-stage mixing process. Detailed Implementation

[0044] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Example 1

[0046] Adhesive formulation (parts by weight): 35 parts soybean meal, 25 parts soybean flour, 30 parts plant-based composite crosslinking agent (20 parts epoxidized soybean oil + 10 parts sodium alginate), 30 parts nano-mineral synergistic reinforcing phase (5 parts nano silica + 5 parts nano cellulose + 10 parts sodium bentonite + 10 parts modified diatomaceous earth), 5 parts KH-550 silane coupling agent, 5 parts compound curing agent (3 parts ammonium chloride + 2 parts aluminum citrate), 3 parts sodium carbonate, and 50 parts deionized water.

[0047] Preparation method:

[0048] S1. Premixed masterbatch: Take 20 parts of soybean meal, 7 parts of hydroxyethyl methyl cellulose, and 5 parts of compound curing agent, mix them in a 30℃ double motion mixer for 25 minutes, pass them through a 100-mesh sieve, and seal and mature for 24 hours.

[0049] S2. Mixing of main ingredients: Add 15 parts of the remaining soybean meal and 25 parts of soybean flour to a dual-motion mixer, stir for 12 minutes, then add the premixed master powder and continue stirring for 18 minutes; then add 30 parts of plant-based composite crosslinking agent and 30 parts of nano-mineral synergistic reinforcing phase, and circulate and stir for 75 minutes (speed 400 r / min).

[0050] S3. Modification reaction: Add 5 parts KH-550, 3 parts sodium carbonate and 50 parts deionized water, heat to 65℃ and stir for 75 minutes, then cool to room temperature to obtain the product.

[0051] Multi-layer plywood preparation: 1.5mm thick poplar veneer (moisture content 10%) is selected, glue application is 200g / m², three layers are glued, hot pressing temperature is 130℃, pressure is 1.5MPa, and time is 45s / mm.

[0052] Example 2

[0053] Adhesive formulation (parts by weight): 30 parts soybean meal, 20 parts soybean flour, 20 parts plant-based composite crosslinking agent (15 parts epoxidized soybean oil + 5 parts sodium alginate), 25 parts nano-mineral synergistic reinforcing phase (3 parts nano silica + 6 parts nano cellulose + 8 parts sodium bentonite + 8 parts modified diatomaceous earth), 3 parts KH-550, 3 parts compound curing agent (2 parts ammonium chloride + 1 part aluminum citrate), 2 parts sodium bicarbonate, and 40 parts deionized water.

[0054] Preparation method: Same as in Example 1, except that the stirring time in step S2 is adjusted to 60 min, and the reaction temperature in step S3 is 60℃ and the time is 90 min.

[0055] Particleboard preparation: Poplar wood shavings (moisture content 10%), glue application 18% (based on oven-dry shavings), hot pressing temperature 140℃, pressure 2.0MPa, time 60s / mm, thickness 18mm.

[0056] Example 3 (Adhesive for Fiberboard)

[0057] Adhesive formulation (parts by weight): 40 parts soybean meal, 30 parts soybean flour, 30 parts plant-based composite crosslinking agent (25 parts epoxidized soybean oil + 5 parts sodium alginate), 36 parts nano-mineral synergistic reinforcing phase (4 parts nano silica + 8 parts nano cellulose + 12 parts sodium bentonite + 12 parts modified diatomaceous earth), 6 parts KH-550, 6 parts compound curing agent (4 parts ammonium chloride + 2 parts aluminum citrate), 4 parts sodium carbonate, and 55 parts deionized water.

[0058] Preparation method: Same as in Example 1, except that the stirring time in step S2 is 90 min and the reaction temperature in step S3 is 70℃ and the reaction time is 60 min.

[0059] Fiberboard preparation: Coniferous wood fiber (moisture content 8%), glue application 15% (based on oven-dry fiber), hot pressing temperature 150℃, pressure 3.0MPa, time 40s / mm, thickness 12mm.

[0060] Performance test results

[0061] Test Project Example 1 (Multi-layer Plywood) Example 2 (Particleboard) Example 3 (Fiberboard) National standards require Formaldehyde emission (mg / m³) 0 0 0 ENF level ≤ 0.025 Boiling in water for 2 hours to check for glue separation No glue coming undone No glue coming undone No glue coming undone Class I boards without delamination Normal water absorption rate (%) 7.2 7.8 6.9 ≤8 Dry static bending strength (MPa) 16.5 15.3 36.5 ≥15 (plywood), ≥15 (particleboard) Internal bond strength (MPa) 0.78 0.73 0.82 ≥0.7 Antibacterial rate (%) 92 90 93 ≥90

[0062] All embodiments meet the requirements of being formaldehyde-free, water-resistant, having good mechanical properties, and being antibacterial, thus verifying the effectiveness of the present invention.

[0063] This invention, through synergistic formulation design (plant-based crosslinking, nano-mineral synergistic reinforcement) and process innovation (two-stage mixing, compound curing), prepares a formaldehyde-free, water-resistant soybean meal-based composite adhesive that combines environmental friendliness, water resistance, mechanical properties, and multifunctional characteristics. It is suitable for the production of various types of engineered wood products, with a stable and controllable process and significant cost advantages, and has important industrial application value.

[0064] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A formaldehyde-free, water-resistant soybean meal-based composite adhesive, characterized in that, The product is composed of the following components by weight: 30-40 parts soybean meal, 20-30 parts soybean flour, 10-30 parts plant-based composite crosslinking agent, 20-40 parts nano-mineral synergistic reinforcing phase, 2-8 parts interface regulator, 3-8 parts compound curing agent, 30-60 parts deionized water, and 5-10 parts hydroxyethyl methyl cellulose. The plant-based composite crosslinking agent is a compound of epoxidized soybean oil and sodium alginate, with a mass ratio of (2-5):

1. The nano-mineral synergistic reinforcing phase is a composite powder of nano-silica, nano-cellulose, sodium bentonite and modified diatomite, with a mass ratio of 1:(1-3):(2-4):(2-4).

2. The formaldehyde-free, water-resistant soybean meal-based composite adhesive according to claim 1, characterized in that, The interface regulator is γ-aminopropyltriethoxysilane; The compound curing agent is a mixture of ammonium chloride and aluminum citrate, with a mass ratio of (1-3):1; The formaldehyde-free, water-resistant soybean meal-based composite adhesive also includes 1-5 parts of a pH adjuster, wherein the pH adjuster is sodium carbonate or sodium bicarbonate, used to adjust the pH value of the adhesive system to 8-10.

3. The formaldehyde-free, water-resistant soybean meal-based composite adhesive according to claim 1, characterized in that, The soybean meal has a protein content of ≥45% and a particle size of 80-120 mesh; The modified diatomaceous earth was activated by 3,3'-thiobis-1-propene at an activation temperature of 15-45℃ and a pH ≥ 3.

0.

4. A method for preparing a formaldehyde-free, water-resistant soybean meal-based composite adhesive as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Premixed masterbatch: Add 20-25 parts of soybean meal, 5-10 parts of hydroxyethyl methyl cellulose, and 3-8 parts of compound curing agent to a double-motion mixer, mix at 25-35℃ for 20-30 minutes, pass through a 100-mesh sieve, seal and mature for 24 hours to obtain premixed masterbatch. S2. Mixing of main ingredients: Add the remaining soybean meal and 20-30 parts of soybean flour to a dual-motion mixer in sequence, stir for 10-15 minutes, then add the premixed master powder and continue stirring for 15-20 minutes; then add 10-30 parts of plant-based composite crosslinking agent and 20-40 parts of nano-mineral synergistic reinforcing phase, and circulate and stir at 360° for 60-90 minutes. S3. Modification reaction: Add 2-8 parts of interface regulator, 1-5 parts of pH adjuster and 30-60 parts of deionized water to the mixed system, heat to 60-70℃, stir for 60-90 min, cool to room temperature to obtain formaldehyde-free water-resistant soybean meal-based composite adhesive.

5. The preparation method of the formaldehyde-free, water-resistant soybean meal-based composite adhesive according to claim 4, characterized in that, The stirring rate of the dual-motion mixer in S2 is 300-500 r / min, and the inner wall of the cylinder is equipped with scrapers to prevent the raw materials from sticking to the wall; The solid content of the reaction system in S3 is controlled to be 20-35%.

6. A formaldehyde-free multifunctional engineered wood panel, characterized in that, It is made of at least two layers of veneer or wood units bonded together by any of the formaldehyde-free, water-resistant soybean meal-based composite adhesives described in any of claims 1-3; The formaldehyde-free multifunctional engineered wood panels include multi-layer plywood, particleboard, fiberboard, blockboard, or solid wood composite flooring. The amount of glue applied to the veneer or wood unit is 150-250 g / m². 2 The hot pressing process parameters are: hot pressing temperature 120-150℃, hot pressing pressure 1.0-3.0MPa, and hot pressing time 30-60s / mm.

7. The formaldehyde-free multifunctional engineered wood panel according to claim 6, characterized in that, The veneer is poplar veneer, pine veneer, eucalyptus veneer or hardwood veneer, with a thickness of 0.5-3mm and a moisture content of 8-12%; The wood unit comprises wood shavings, fibers, or plywood core strips with a moisture content of 8-12%.

8. The application of a formaldehyde-free, water-resistant soybean meal-based composite adhesive as described in any one of claims 1-3 in the production of engineered wood products, characterized in that, Used in adhesives to improve the formaldehyde-free environmental performance, water resistance, mechanical properties and antibacterial properties of engineered wood products. Suitable for furniture manufacturing, interior decoration, humid environments and children's products.

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