Hydrophobic weather-resistant formaldehyde-free adhesive based on eutectic solvent liquefied bagasse and preparation method of hydrophobic weather-resistant formaldehyde-free adhesive

Abstract

The invention belongs to the technical field of biomass materials and macromolecular adhesives, and particularly relates to a hydrophobic weather-resistant formaldehyde-free adhesive based on eutectic solvent liquefied bagasse and a preparation method of the hydrophobic weather-resistant formaldehyde-free adhesive. Menthol and n-decanoic acid are used as hydrophobic eutectic solvents and react with bagasse to prepare a bio-based adhesive prepolymer, the bio-based adhesive prepolymer is used for preparing the hydrophobic weather-resistant formaldehyde-free adhesive, and the hydrophobic weather-resistant formaldehyde-free adhesive has excellent hydrophobicity and weather resistance and high bio-based content.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of biomass materials and polymer adhesives, and more particularly relates to a hydrophobic weather-resistant formaldehyde-free adhesive based on eutectic solvent liquefied bagasse and a preparation method thereof. BACKGROUND

[0002] The wood-based panel industry is the basis of the wood processing and furniture manufacturing industry, and its production is heavily dependent on adhesives. At present, the mainstream aldehyde-based adhesives such as urea-formaldehyde resin and phenol-formaldehyde resin on the market have low cost and high bonding strength, but they continuously release toxic and harmful gases such as formaldehyde during production and use, which poses a serious threat to the environment and human health.

[0003] With the increasing emphasis on environmental protection and health, the development of green, non-toxic and renewable bio-based adhesives has become an irreversible trend. However, the existing bio-based adhesives (such as soybean protein glue, starch glue, and lignin glue) have a fatal weakness of poor water resistance. The matrix of these adhesives is rich in hydrophilic groups (-OH, -NH2, -COOH), and the glue layer will quickly absorb water and swell in the presence of water or in a humid environment, resulting in a sharp decrease in bonding strength or even complete failure, which greatly limits their application in structural and weather-resistant applications.

[0004] At the same time, bagasse, as a large amount of agricultural waste from the sugar industry, is a valuable biomass polymer resource, but it is currently mostly burned or discarded at low value. How to convert it into high-performance materials is a difficult problem that needs to be solved in the field.

[0005] Therefore, it is of great economic and environmental significance to develop a bio-based adhesive that can not only utilize waste biomass such as bagasse at high value, but also fundamentally solve the water resistance bottleneck of bio-based adhesives and achieve "zero formaldehyde" addition. SUMMARY

[0006] The purpose of the present application is to provide a hydrophobic weather-resistant formaldehyde-free adhesive based on eutectic solvent liquefied bagasse and a preparation method thereof, and more particularly to provide a formaldehyde-free adhesive with high bio-based content, zero formaldehyde addition, high strength, high hydrophobicity, and high weather resistance to solve the problems of the prior art.

[0007] To achieve the above purpose, the present application provides the following solutions: One of the technical solutions of the present application is to provide a bio-based adhesive prepolymer, the raw materials of which include, by mass fraction, 50-90 parts of a hydrophobic eutectic solvent (HDES) and 10-50 parts of bagasse. The hydrophobic eutectic solvent includes menthol and lauric acid.

[0008] Furthermore, the molar ratio of menthol to decanoic acid is 1:1-3.

[0009] The second technical solution of the present invention provides a method for preparing the above-mentioned bio-based adhesive prepolymer, the steps of which include: Mix bagasse and a hydrophobic eutectic solvent, heat to 90-170℃, and stir to react. The resulting yellowish-brown, homogeneous, viscous liquid is the bio-based adhesive prepolymer.

[0010] Furthermore, the stirring reaction time is 1.5-5 hours.

[0011] The third technical solution of the present invention provides an application of the above-mentioned bio-based adhesive prepolymer in the preparation of formaldehyde-free adhesives.

[0012] Fourth technical solution of the present invention: Provides a hydrophobic, weather-resistant, formaldehyde-free adhesive, comprising, by weight, the following raw materials: The above-mentioned bio-based adhesive prepolymer consists of 100 parts, curing agent 5-20 parts, diluent 1-15 parts, filler 5-30 parts, and functional additive 0.5-5 parts; The curing agent is a formaldehyde-free multifunctional crosslinking agent; The diluent is a bio-based solvent or a reactive diluent; The filler includes at least one of wood flour, bamboo flour, calcium carbonate, and kaolin. The functional additives include at least one of silane coupling agents, defoamers, and leveling agents.

[0013] Furthermore, the curing agent includes polyisocyanates, bio-based epoxy resins, citric acid, or maleic anhydride.

[0014] Furthermore, the diluent includes furfural, methyl levulinate, biodiesel, or epoxidized soybean oil.

[0015] Fifth technical solution of the present invention: A method for preparing the above-mentioned hydrophobic and weather-resistant formaldehyde-free adhesive, comprising the following steps: Component A is obtained by mixing bio-based adhesive prepolymer, diluent, filler and functional additives; The hydrophobic, weather-resistant, formaldehyde-free adhesive is obtained by mixing the curing agent (component B) with component A.

[0016] The sixth technical solution of the present invention provides an application of the above-mentioned hydrophobic and weather-resistant formaldehyde-free adhesive in the preparation of artificial boards.

[0017] The present invention discloses the following technical effects: This invention provides a formaldehyde-free adhesive prepared from biomass waste (bagasse). The bagasse is liquefied under mild conditions using a hydrophobic eutectic solvent (HDES) and compounded with a curing agent and additives. This formaldehyde-free adhesive has excellent hydrophobicity, weather resistance and high bio-based content.

[0018] The HDES used in this invention is strongly hydrophobic. During liquefaction, it encapsulates and permeates bagasse, partially esterifying its hydrophilic groups. After curing, it forms an "oil-encapsulated solid" system with hydrophobic HDES as the continuous phase. After cross-linking, it constructs a dense, non-polar three-dimensional network that effectively repels water molecules. This results in a significantly higher wet shear strength retention rate for plywood after immersion in water or boiling, compared to traditional protein and starch adhesives, making it suitable for outdoor and humid environments. At around 150℃ (90-170℃), HDES acts as both a solvent and an acid catalyst, promoting partial depolymerization of lignin and hemicellulose in bagasse, releasing a large number of active hydroxyl groups for efficient cross-linking with the curing agent. The liquefied product exhibits excellent wettability to wood and can form strong chemical bonds with the hydroxyl groups on the wood surface, ensuring high bonding strength. Furthermore, the viscosity, open time, and curing speed of the adhesive can be controlled by adjusting the amount of diluent and curing agent, adapting it to different hot-pressing processes.

[0019] This invention uses inexpensive and abundant bagasse to replace petroleum-based synthetic resins, with mild reaction conditions and low energy consumption. HDES is derived from plants and coconut / palm kernel oil, which is biodegradable, realizing the high-value utilization of biomass waste. The process is environmentally friendly, and from raw materials to curing agents, there is no addition or release of toxic and harmful substances such as formaldehyde and phenol, which meets indoor air quality standards. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the preparation process of the bio-based adhesive prepolymer in this invention. Detailed Implementation

[0021] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0022] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0023] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0024] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0025] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0026] Unless otherwise specified, all raw materials and reagents involved in the specific embodiments of this invention are commercially available products.

[0027] Unless otherwise specified, room temperature and ambient temperature in the specific embodiments of this invention refer to 20-30℃.

[0028] Unless otherwise specified, the term "parts" in the specific embodiments of this invention refers to "parts by mass".

[0029] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0030] In some specific embodiments, the present invention provides a method for preparing a hydrophobic, weather-resistant, formaldehyde-free adhesive, comprising the following steps: S1. Menthol and n-decanoic acid are mixed in a molar ratio of 1:1-3 and stirred at 50-80°C until a homogeneous and transparent liquid is formed to obtain HDES. S2. Mix 50-90 parts of HDES with 10-50 parts of dried and pulverized bagasse powder, heat to 90-170℃, and stir and react at this temperature for 1.5-5 hours to obtain a yellowish-brown, homogeneous, viscous liquid, which is the bio-based adhesive prepolymer. S3. Mix 100 parts of bio-based adhesive prepolymer, 1-15 parts of diluent, 5-30 parts of filler and 0.5-5 parts of functional additive to obtain component A; The diluent is a bio-based solvent or a reactive diluent, including furfural, methyl levulinate, biodiesel, or epoxidized soybean oil; the filler includes at least one of wood flour, bamboo flour, calcium carbonate, and kaolin; the functional additives include at least one of silane coupling agents, defoamers, and leveling agents; the silane coupling agents include at least one of γ-aminopropyltriethoxysilane (KH-550), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792), and γ-glycidoxypropyltrimethoxysilane (KH560); the defoamers include at least one of paraffin oil defoamers, silicone defoamers, and polyether defoamers; and the leveling agents include at least one of acrylate leveling agents, modified alkyd resin leveling agents, and polydimethylsiloxane. S4. Using the curing agent as component B, mix it with component A and stir at high speed (800 rpm) until uniform to obtain a hydrophobic, weather-resistant, formaldehyde-free adhesive. The curing agent is a formaldehyde-free multifunctional crosslinking agent, including polyisocyanates, bio-based epoxy resins, citric acid, or maleic anhydride.

[0031] These small molecules in the diluent have extremely low initial viscosity, which rapidly reduces the overall viscosity of the adhesive and improves wettability to wood vessels and cell cavities. During the subsequent hot-press curing stage, the epoxy groups or double bonds in the diluent react with the curing agent in the system and are permanently woven into the three-dimensional network. The core reaction of solidification is the formation of carbamate bonds between the isocyanate groups (-NCO) and the hydroxyl groups (-OH) in liquefied bagasse, as follows: ; Because the acid catalysis of HDES releases a large number of active hydroxyl groups, this reaction is extremely rapid under hot-pressing conditions and can construct a rigid network with high cross-linking density.

[0032] Example 1 The preparation steps of the hydrophobic, weather-resistant, formaldehyde-free adhesive include: S1. Mix 42.9 g of menthol (approximately 0.285 mol) and 57.1 g of n-decanoic acid (approximately 0.285 mol), and stir at 70 °C until a homogeneous and transparent liquid is formed (approximately 30 min) to obtain HDES; S2. Mix HDES with dried and pulverized bagasse powder at a mass ratio of 2:1, heat to 150℃, and stir at this temperature for 2 hours to obtain a yellowish-brown, homogeneous, viscous liquid, which is the bio-based adhesive prepolymer. S3. Mix 100 parts of bio-based adhesive prepolymer, 8 parts of diluent (furfural), 20 parts of filler (wood flour), and 2 parts of functional additives (1.5 parts KH-560 and 0.5 parts organosilicon defoamer BYK-066) evenly (2000 rpm) to obtain component A; S4. Mix 15 parts of curing agent (polymethylene polyphenyl polyisocyanate) as component B with component A, and stir at high speed (800 rpm) until homogeneous to obtain a hydrophobic and weather-resistant formaldehyde-free adhesive.

[0033] Example 2 The preparation steps of the hydrophobic, weather-resistant, formaldehyde-free adhesive include: S1. Mix 27.3g of menthol (approximately 0.18 mol) and 72.7g of n-decanoic acid (approximately 0.36 mol), and stir at 70°C until a homogeneous and transparent liquid is formed to obtain HDES; S2. Mix 90 parts of HDES with 30 parts of dried and pulverized bagasse powder, heat to 160℃, and stir and react at this temperature for 1.5 hours to obtain a yellowish-brown, homogeneous, viscous liquid, which is the bio-based adhesive prepolymer. S3. Mix 100 parts of bio-based adhesive prepolymer, 8 parts of diluent (methyl levulinate), 15 parts of filler (heavy calcium carbonate), and 1.5 parts of functional additives (1 part KH-550 and 0.5 parts polyether modified siloxane leveling agent) at 2000 rpm to obtain component A. S4. Mix 20 parts of curing agent (polymethylene polyphenyl polyisocyanate) as component B with component A, and stir at high speed (800 rpm) until homogeneous to obtain a hydrophobic and weather-resistant formaldehyde-free adhesive.

[0034] Comparative Example 1 The only difference from Example 1 is the use of a different prepolymer. The specific steps are as follows: S1. Glycerol and dried and pulverized bagasse powder are mixed at a mass ratio of 2:1, and 3 parts of concentrated sulfuric acid are added as a catalyst. The mixture is heated to 160°C and stirred at this temperature for 2 hours to obtain a dark brown viscous liquid, which is the prepolymer C. S2. Mix 100 parts of prepolymer C, 15 parts of diluent (epoxidized soybean oil), 20 parts of filler (wood flour), and 2 parts of functional additives (1 part KH-550 and 0.5 parts polyether modified siloxane leveling agent) evenly (2000 rpm) to obtain component A. S3. Mix 15 parts of curing agent (polymethylene polyphenyl polyisocyanate) as component B with component A, and stir at high speed (800 rpm) until homogeneous to obtain adhesive.

[0035] Comparative Example 2 Commercially available E1 grade urea-formaldehyde resin (UF) can be used after adding 1.5% ammonium chloride curing agent according to its instructions and mixing evenly.

[0036] Comparative Example 3 The preparation steps of the adhesive include: S1. Mix 42.9 g of menthol (approximately 0.285 mol) and 57.1 g of n-decanoic acid (approximately 0.285 mol), and stir at 70 °C until a homogeneous and transparent liquid is formed (approximately 30 min) to obtain HDES; S2. Mix HDES with dried and pulverized bagasse powder at a mass ratio of 2:1, heat to 150℃, and stir at this temperature for 2 hours to obtain a yellowish-brown, homogeneous, viscous liquid, which is the bio-based adhesive prepolymer. S3. Mix 100 parts of bio-based adhesive prepolymer, 1 part of diluent (biodiesel), 20 parts of filler (wood flour) and 2 parts of functional additives (1 part KH-550 and 0.5 parts polyether modified siloxane leveling agent) evenly (2000 rpm) to obtain adhesive.

[0037] Comparative Example 4 The preparation steps of starch-based adhesives include: Add 400 g of water, 7 g of sodium hypochlorite (oxidant), and 10 g of sodium hydroxide solution (30 wt%, gelatinizing agent) to 100 g of corn starch, stir well, then add 150 g of warm water (50 ℃) to reduce viscosity, 2 g of borax (crosslinking agent), 1 g of sodium thiosulfate (terminating agent), and 0.3 g of sodium benzoate (preservative), and mix well to obtain starch-based adhesive.

[0038] Test case The adhesives obtained in Examples 1-2 and Comparative Examples 1-4 were used in the preparation of wood-based panels. The specific steps are as follows: The prepared adhesive was applied manually at a rate of 180 g / m 2 Apply glue to the upper and lower surfaces of the eucalyptus veneer according to the glue application amount. After applying the glue, let it stand for 10 minutes. Then, assemble the blank with two eucalyptus veneers on the outside and one eucalyptus veneer on the inside. Then, place it in a hot press and hot press for 10 minutes at a temperature of 120℃ and a pressure of 1.2MPa. After pressing, cool it for later use.

[0039] The performance of the prepared wood-based panels was tested in accordance with the national standard GB / T 17657-2022, and the formaldehyde emission was tested using the internationally accepted environmental climate chamber method (EN 717-1) (the formaldehyde test results are in mg / L). The results are shown in Table 1.

[0040] Table 1 By comparing the data in Table 1, it can be seen that the adhesives prepared under the HDES system (Examples 1 and 2) have better wet strength retention compared to Comparative Examples 1-4. Compared to commercially available E1 grade urea-formaldehyde resin (Comparative Example 2), the adhesives prepared under the HDES system have similar dry shear strength but better wet shear strength, and the wet strength retention is 20% higher than that of urea-formaldehyde resin. At the same time, the formaldehyde content of the adhesive prepared under the eutectic system is less than 0.005 mg / L, while that of urea-formaldehyde resin is 0.09 mg / L. It can be seen that the adhesives prepared by the present invention are more environmentally friendly, and the wet strength retention further demonstrates that the formaldehyde-free adhesives prepared by the present invention have excellent hydrophobicity.

[0041] Figure 1 This is a schematic diagram of the preparation process of the bio-based adhesive prepolymer in this invention.

[0042] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0043] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A bio-based adhesive prepolymer, characterized in that, By weight, the raw materials include: 50-90 parts of hydrophobic eutectic solvent and 10-50 parts of bagasse; The hydrophobic eutectic solvent includes menthol and n-decanoic acid.

2. The bio-based adhesive prepolymer as described in claim 1, characterized in that, The molar ratio of menthol to decanoic acid is 1:1-3.

3. A method for preparing the bio-based adhesive prepolymer according to claim 1 or 2, characterized in that the step... include: Mix bagasse and a hydrophobic eutectic solvent, heat to 90-170℃, and stir to react. The resulting yellowish-brown, homogeneous, viscous liquid is the bio-based adhesive prepolymer.

4. The preparation method according to claim 3, characterized in that, The stirring reaction time is 1.5-5 hours.

5. The use of the bio-based adhesive prepolymer according to claim 1 or 2 in the preparation of formaldehyde-free adhesives.

6. A hydrophobic, weather-resistant, formaldehyde-free adhesive, characterized in that, By weight, the raw materials include: The bio-based adhesive prepolymer of claim 1 or 2 comprises 100 parts, curing agent 5-20 parts, diluent 1-15 parts, filler 5-30 parts, and functional additive 0.5-5 parts; The curing agent is a formaldehyde-free multifunctional crosslinking agent; The diluent is a bio-based solvent or a reactive diluent; The filler includes at least one of wood flour, bamboo flour, calcium carbonate, and kaolin. The functional additives include at least one of silane coupling agents, defoamers, and leveling agents.

7. The hydrophobic, weather-resistant, formaldehyde-free adhesive as described in claim 6, characterized in that, The curing agent includes polyisocyanates, bio-based epoxy resins, citric acid, or maleic anhydride.

8. The hydrophobic, weather-resistant, formaldehyde-free adhesive as described in claim 6, characterized in that, The diluents include furfural, methyl levulinate, biodiesel, or epoxidized soybean oil.

9. A method for preparing a hydrophobic, weather-resistant, formaldehyde-free adhesive according to any one of claims 6-8, characterized in that the step... include: Component A is obtained by mixing bio-based adhesive prepolymer, diluent, filler and functional additives; The hydrophobic, weather-resistant, formaldehyde-free adhesive is obtained by mixing the curing agent (component B) with component A.

10. The application of the hydrophobic, weather-resistant, formaldehyde-free adhesive according to any one of claims 6-8 in the preparation of engineered wood products.

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