A bio-based adhesive, its preparation method and application

Abstract

The application provides a kind of bio-based adhesive and its preparation method and application.The bio-based adhesive of the application, biomass matrix includes the mixture of gum arabic and carboxymethyl chitosan, using carboxymethyl chitosan and gum arabic rich carboxyl, hydroxyl and other functional groups, hydrogen bond crosslinking network in adhesive is formed, at the same time, polyvinyl alcohol and reinforcing agent in the adhesive multiple polymer chains intertangle, compared with single biomass base adhesive, it plays the role of synergistic enhancing adhesive heat resistance, adhesive strength, stability and other properties;The application does not add formaldehyde in the process of adhesive preparation, achieves the standard of formaldehyde-free from the source, simple operation, green and environment-friendly;The biomass matrix material of the application is widely sourced, rich in nature, low in price, and the solvent of raw material is water, without complex organic modification, the production process does not introduce materials harmful to human health, green and harmless.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and more particularly to a bio-based adhesive, its preparation method, and its application. Background Technology

[0002] The development of adhesive technology has driven socio-economic progress, and it is currently widely used in packaging, construction, medical fields, and especially in the bonding of a large number of engineered wood products in home furnishings. Traditional adhesives for boards mainly include urea-formaldehyde resin, phenol-formaldehyde resin, and melamine resin, commonly known as "three-aldehyde adhesives." Although they have advantages such as excellent performance and low production costs, their synthesis process involves aldehydes, making them prone to releasing free formaldehyde during use. Formaldehyde poses a significant threat to human health, being classified as a Group 1 carcinogen in 2006. Its health hazards include irritation, sensitization, and mutagenicity. Inhaling excessive amounts of formaldehyde can cause headaches, fatigue, nausea, vomiting, palpitations, depression, insomnia, and even death. Currently, several standards, such as the "Limits of Hazardous Substances in Adhesives for Interior Decoration and Renovation Materials," limit the release of formaldehyde from various engineered wood products. In recent years, the development of green and environmentally friendly formaldehyde-free adhesives has gradually become a research hotspot.

[0003] Bio-based materials have been applied to the field of formaldehyde-free adhesives due to their abundant natural resources, low cost, and simple modification. Bio-based formaldehyde-free adhesives have also proven to be promising adhesives. Existing technology discloses a water-resistant bio-based adhesive that incorporates soybean meal and bio-enzymes in its preparation process. This adhesive exhibits excellent bonding strength and water resistance; however, the active sites of the bio-enzymes require harsh temperature conditions, resulting in insufficient heat resistance during preparation and use. Existing technology discloses a method for preparing demethylated nano-lignin and its fully bio-based adhesive, but its preparation process is overly complex.

[0004] Currently, single-type bio-based adhesives generally suffer from insufficient adhesive strength. Carboxymethyl chitosan is a natural polymer with biodegradable and antibacterial properties. Introducing it into adhesives can enhance antifungal performance, and the carboxyl and amino groups on the molecular chain can form a hydrogen bond network with the adhesive matrix. Existing technology discloses a method for preparing an antibacterial soybean meal adhesive; the introduction of carboxymethyl chitosan imparts antibacterial properties to the material, but the polyethyleneimine in this adhesive exhibits some cytotoxicity. Gum arabic is a gum derivative with good thickening and stability. Existing technology discloses a gum arabic-based adhesive; however, the large-scale use of diphenylmethane diisocyanate in its production process poses safety risks. Composite bio-based adhesives can combine the advantages of various bio-based materials, but the preparation process presents significant challenges. For example, the aggregation of natural polymer segments can affect the uniformity of the adhesive; therefore, the introduction of bio-based materials requires consideration of issues such as cost and material compatibility.

[0005] In summary, there is a need for a simple, green, and environmentally friendly method for preparing bio-based formaldehyde-free adhesives to address the performance and production issues present in existing technologies. Summary of the Invention

[0006] In view of this, the present invention provides a bio-based adhesive, its preparation method and application, to overcome the deficiencies in the prior art.

[0007] In a first aspect, the present invention provides a bio-based adhesive comprising the following raw materials in parts by weight: 2-10 parts of biomass matrix, 0.5-4 parts of polyvinyl alcohol, 30-100 parts of water, 0.1-0.4 parts of defoamer, 0.05-0.5 parts of preservative, 1.5-5 parts of plasticizer, 0.3-0.7 parts of thickener, and 1-3 parts of reinforcing agent;

[0008] The biomass matrix comprises a mixture of gum arabic and carboxymethyl chitosan.

[0009] Preferably, in the bio-based adhesive, the mass ratio of gum arabic to carboxymethyl chitosan is (1-5):(1-5).

[0010] Preferably, the thickener in the bio-based adhesive includes at least one of natural rubber, oxidized corn starch, oxidized mung bean starch, xanthan gum, gelatin, guar gum, agar, methylcellulose, hydroxyethylcellulose, hydroxypropyl methylcellulose, and sodium carboxymethylcellulose.

[0011] Preferably, the preservative in the bio-based adhesive includes at least one of potassium sorbate, calcium propionate, curcumin, allicin, and nano-titanium dioxide.

[0012] And / or, the plasticizer is polyethylene glycol.

[0013] Preferably, the reinforcing agent in the bio-based adhesive includes at least one of carboxylated styrene-butadiene rubber latex, oxidized natural rubber latex, ethylene vinyl acetate copolymer latex, and waterborne polyurethane.

[0014] Preferably, the defoamer in the bio-based adhesive includes at least one of polyether defoamer and silicone defoamer.

[0015] Preferably, in the bio-based adhesive, the polyether defoamer includes at least one of polyoxypropylene glycerol ether, glycerol polyoxyethylene ether, and polypropylene glycol;

[0016] The organosilicon defoamer includes at least one of fluorosiloxane, polydimethylsiloxane, and polymethylhydrosiloxane.

[0017] Secondly, the present invention also provides a method for preparing the aforementioned bio-based adhesive, comprising the following steps:

[0018] The biomass matrix was added to a portion of water, then a plasticizer was added, and the mixture was stirred to obtain the first solution;

[0019] The reinforcing agent is added to the first solution and mixed to obtain the second solution;

[0020] Add polyvinyl alcohol to the remaining water and stir to obtain a polyvinyl alcohol solution;

[0021] The second solution is added to the polyvinyl alcohol solution, followed by the addition of thickener, preservative, and defoamer. The mixture is then stirred to obtain the bio-based adhesive.

[0022] Preferably, in the preparation method of the bio-based adhesive, in the step of adding the biomass matrix to a portion of water, the water is 10 to 30 parts by weight.

[0023] The reinforcing agent is added to the first solution and mixed ultrasonically to obtain the second solution;

[0024] Polyvinyl alcohol is added to the remaining water and stirred at 80–100°C to obtain a polyvinyl alcohol solution.

[0025] Thirdly, the present invention also provides an application of the bio-based adhesive or the bio-based adhesive prepared by the preparation method described above in the processing of plywood and blockboard.

[0026] The bio-based adhesive and its preparation method of the present invention have the following advantages over the prior art:

[0027] The bio-based adhesive of this invention consists of two main parts: a biomass matrix and non-biomass materials. The biomass matrix comprises a mixture of gum arabic and carboxymethyl chitosan. This invention utilizes the abundant carboxyl and hydroxyl functional groups in carboxymethyl chitosan and gum arabic to form a hydrogen-bonded cross-linking network in the adhesive. Simultaneously, polyvinyl alcohol and reinforcing agents intertwine multiple polymer chains in this adhesive, synergistically enhancing the adhesive's heat resistance, adhesive strength, and stability compared to single biomass-based adhesives. This invention eliminates the addition of formaldehyde during adhesive preparation, achieving formaldehyde-free standards from the source. It is simple to operate and environmentally friendly. The raw materials of this invention are mainly divided into two parts: a biomass matrix and non-biomass materials. The biomass matrix material is widely available, abundant in nature, and inexpensive. Moreover, the solvent for the raw material is water, requiring no complex organic modification. The production process does not introduce any materials harmful to human health, making it green and harmless. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single digits within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0030] This application provides a bio-based adhesive comprising the following raw materials in parts by weight: 2-10 parts biomass matrix, 0.5-4 parts polyvinyl alcohol, 30-100 parts water, 0.1-0.4 parts defoamer, 0.05-0.5 parts preservative, 1.5-5 parts plasticizer, 0.3-0.7 parts thickener, and 1-3 parts reinforcing agent;

[0031] The biomass matrix includes a mixture of gum arabic and carboxymethyl chitosan.

[0032] The raw materials of the bio-based adhesive of this invention are mainly divided into two parts: biomass matrix and non-biomass materials. The biomass matrix includes a mixture of gum arabic and carboxymethyl chitosan. This invention utilizes the abundant carboxyl and hydroxyl functional groups of carboxymethyl chitosan and gum arabic to form a hydrogen-bonded cross-linking network in the adhesive. At the same time, polyvinyl alcohol and reinforcing agents intertwine multiple polymer chains in this adhesive, which, compared with single biomass-based adhesives, synergistically enhances the heat resistance, adhesive strength, stability, and other properties of the adhesive. This invention does not add formaldehyde during the adhesive preparation process, achieving the formaldehyde-free standard from the source. It is simple to operate and environmentally friendly. The raw materials of this invention are mainly divided into two parts: biomass matrix and non-biomass materials. The biomass matrix material is widely available, abundant in nature, and inexpensive. Moreover, the solvent of the raw material is water, which does not require complex organic modification. The production process does not introduce any materials that are harmful to human health, making it green and harmless.

[0033] In some embodiments, the mass ratio of gum arabic to carboxymethyl chitosan is (1-5):(1-5).

[0034] Specifically, gum arabic (also known as acacia gum) is a safe and harmless thickener that naturally solidifies in the air. It has a complex molecular structure (CAS: 9000-01-5), is a high-molecular-weight electrolyte with a molecular weight of 220,000 to 300,000, and slowly dissolves in water to form a thick, odorless viscous agent.

[0035] Carboxymethyl chitosan is an important water-soluble chitosan derivative with the chemical formula C2. 20 H 37 N3O 14 .

[0036] Specifically, polyvinyl alcohol, abbreviated as PVA, has the CAS number 9002-89-5 and the molecular formula [C2H4O]. n .

[0037] In some embodiments, the thickener includes at least one of natural rubber, oxidized corn starch, oxidized mung bean starch, xanthan gum, gelatin, guar gum, agar, methylcellulose, hydroxyethylcellulose, hydroxypropyl methylcellulose, and sodium carboxymethylcellulose.

[0038] Preferably, the thickener is xanthan gum, a high molecular weight polysaccharide composed of five sugar molecules as a unit, polymerized from the same units. Its CAS number is 11138-66-2, and its molecular formula is C8H2O. 14 Cl2N2O2.

[0039] In some embodiments, the preservative includes at least one of potassium sorbate, calcium propionate, curcumin, allicin, and nano-titanium dioxide.

[0040] Preferably, the preservative is curcumin. Curcumin is a yellow pigment extracted from the rhizomes of plants such as turmeric (Zingiber officinale) in the ginger family. It is an acidic polyphenol with a main chain consisting of unsaturated aliphatic and aromatic groups. Curcumin has CAS number 458-37-7 and molecular formula C2. 21 H 20 O6.

[0041] In some embodiments, the plasticizer is polyethylene glycol.

[0042] Specifically, polyethylene glycol has the CAS number 25322-68-3 and the molecular formula HO(CH2CH2O). n H. The polyethylene glycol used in this invention has a molecular weight of 1500 to 4000.

[0043] In some embodiments, the reinforcing agent includes at least one of carboxylated styrene-butadiene rubber latex, oxidized natural rubber latex, ethylene vinyl acetate copolymer latex, and waterborne polyurethane.

[0044] Preferably, the reinforcing agent is ethylene vinyl acetate copolymer emulsion (i.e., EVA resin), CAS number 24937-78-8, molecular formula C 18 H 30 O6X2.

[0045] In some embodiments, the defoamer includes at least one of polyether defoamer and silicone defoamer.

[0046] Specifically, polyether defoamers include at least one of polyoxypropylene glycerol ether, glycerol polyoxyethylene ether, and polypropylene glycol.

[0047] Organosilicon defoamers include at least one of fluorosiloxane, polydimethylsiloxane, and polymethylhydrosiloxane.

[0048] In some embodiments, the bio-based adhesive of the present invention comprises the following raw materials in parts by weight: 1-5 parts carboxymethyl chitosan, 5 parts gum arabic, 0.5-3.5 parts polyvinyl alcohol, 55 parts water, 0.2 parts defoamer, 0.3 parts preservative, 3 parts plasticizer, 0.5 parts thickener, and 2 parts reinforcing agent.

[0049] Based on the same inventive concept, the present invention also provides a method for preparing the above-mentioned bio-based adhesive, comprising the following steps:

[0050] S1. Add the biomass matrix to a portion of water, then add a plasticizer and stir to obtain the first solution;

[0051] S2. Add the reinforcing agent to the first solution and mix to obtain the second solution;

[0052] S3. Add polyvinyl alcohol to the remaining water and stir to obtain a polyvinyl alcohol solution;

[0053] S4. Add the second solution to the polyvinyl alcohol solution, then add the thickener, preservative, and defoamer, and stir to obtain the bio-based adhesive.

[0054] In some embodiments, in the step of adding the biomass matrix to a portion of the water, the water is 10 to 30 parts by weight; correspondingly, in the step of adding polyvinyl alcohol to the remaining water, the remaining water is 20 to 70 parts by weight.

[0055] In some embodiments, an enhancer is added to a first solution and ultrasonically mixed to obtain a second solution.

[0056] In some embodiments, polyvinyl alcohol is added to the remaining water and stirred at 80–100°C to obtain a polyvinyl alcohol solution.

[0057] In some embodiments, a second solution is added to a polyvinyl alcohol solution, followed by the addition of a thickener, preservative, and defoamer, and stirred for 1–5 hours to obtain a bio-based adhesive.

[0058] The preparation method of the bio-based adhesive of this invention utilizes the abundant carboxyl and hydroxyl functional groups of carboxymethyl chitosan and gum arabic to form a hydrogen-bonded cross-linked network in the adhesive. Simultaneously, polyvinyl alcohol and reinforcing agents intertwine multiple polymer chains within the adhesive, synergistically enhancing the adhesive's heat resistance, adhesive strength, and stability compared to single biomass-based adhesives. Compared to multiple bio-based adhesives, this method is simpler in material usage, lower in cost, and requires no organic modification. Traditional "three-aldehyde adhesive" preparation processes involve the introduction of toxic substances such as formaldehyde. Free formaldehyde can pose health hazards during use, thus the research and development of formaldehyde-free adhesives has become a hot topic. The raw materials of this invention mainly consist of two parts: a biomass matrix and non-biomass materials. The biomass matrix materials are widely available, abundant in nature, and inexpensive. Furthermore, the solvent for the raw materials is water, and the production process does not introduce any materials harmful to human health, making it green and harmless.

[0059] Based on the same inventive concept, the present invention also provides an application of the above-mentioned bio-based adhesive or the bio-based adhesive prepared by the above-mentioned preparation method in the processing of plywood and blockboard.

[0060] The following specific embodiments further illustrate the bio-based adhesive and its preparation method of this application. This section further illustrates the content of the present invention with reference to specific embodiments, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0061] In the following examples and comparative examples, carboxymethyl chitosan was purchased from Maclean's Reagents; gum arabic (powder) was purchased from Maclean's Reagents; polyvinyl alcohol was purchased from Aladdin Reagents, model 1799; defoamer: polymethylhydrosiloxane, purchased from Maclean's Reagents; preservative: curcumin, purchased from Maclean's Reagents; plasticizer: polyethylene glycol 2000, purchased from Sinopharm Group; thickener: xanthan gum (80 mesh), purchased from Maclean's Reagents; reinforcing agent: ethylene vinyl acetate copolymer emulsion, purchased from Shandong Yousuo Chemical Technology Co., Ltd., model BJ-707.

[0062] Example 1

[0063] This application provides a bio-based adhesive comprising the following raw materials: 5g carboxymethyl chitosan, 5g gum arabic, 0.5g polyvinyl alcohol, 55mL (i.e., 55g) water, 0.2g defoamer, 0.3g preservative, 3g plasticizer, 0.5g thickener, and 2g reinforcing agent.

[0064] The defoamer is polymethylhydrosiloxane;

[0065] The preservative is curcumin;

[0066] The plasticizer is polyethylene glycol 2000;

[0067] The thickener is xanthan gum;

[0068] The reinforcing agent is an ethylene vinyl acetate copolymer emulsion.

[0069] This embodiment also provides a method for preparing the above-mentioned bio-based adhesive, including the following steps:

[0070] S1. Dissolve 5g of carboxymethyl chitosan and 5g of gum arabic in 20mL (i.e., 20g) of water, then add 3g of polyethylene glycol (specifically polyethylene glycol 2000), and stir for 1 hour to obtain the first solution;

[0071] S2. Add 2g of ethylene vinyl acetate copolymer emulsion to the first solution and sonicate for 30min to obtain the second solution;

[0072] S3. Add 0.5g of polyvinyl alcohol to 35mL (i.e. 35g) of water and stir at 90℃ for 4h to obtain a polyvinyl alcohol solution.

[0073] S4. Add the second solution to the polyvinyl alcohol solution, then add 0.5g xanthan gum, 0.3g curcumin, and 0.2g defoamer, and continue stirring for 2.5h to obtain the bio-based adhesive.

[0074] Example 2

[0075] This application provides a bio-based adhesive comprising the following raw materials: 5g carboxymethyl chitosan, 5g gum arabic, 1g polyvinyl alcohol, 55mL (i.e., 55g) water, 0.2g defoamer, 0.3g preservative, 3g plasticizer, 0.5g thickener, and 2g reinforcing agent.

[0076] The defoamer is polymethylhydrosiloxane;

[0077] The preservative is curcumin;

[0078] The plasticizer is polyethylene glycol 2000;

[0079] The thickener is xanthan gum;

[0080] The reinforcing agent is an ethylene vinyl acetate copolymer emulsion.

[0081] This embodiment also provides a method for preparing the above-mentioned bio-based adhesive, including the following steps:

[0082] S1. Dissolve 5g of carboxymethyl chitosan and 5g of gum arabic in 20mL (i.e., 20g) of water, then add 3g of polyethylene glycol (specifically polyethylene glycol 2000), and stir for 1 hour to obtain the first solution;

[0083] S2. Add 2g of ethylene vinyl acetate copolymer emulsion to the first solution and sonicate for 30min to obtain the second solution;

[0084] S3. Add 1g of polyvinyl alcohol to 35mL (i.e. 35g) of water and stir at 90℃ for 4h to obtain a polyvinyl alcohol solution.

[0085] S4. Add the second solution to the polyvinyl alcohol solution, then add 0.5g xanthan gum, 0.3g curcumin, and 0.2g defoamer, and continue stirring for 2.5h to obtain the bio-based adhesive.

[0086] Example 3

[0087] This application provides a bio-based adhesive comprising the following raw materials: 5g carboxymethyl chitosan, 5g gum arabic, 1.5g polyvinyl alcohol, 55mL (i.e., 55g) water, 0.2g defoamer, 0.3g preservative, 3g plasticizer, 0.5g thickener, and 2g reinforcing agent.

[0088] The defoamer is polymethylhydrosiloxane;

[0089] The preservative is curcumin;

[0090] The plasticizer is polyethylene glycol 2000;

[0091] The thickener is xanthan gum;

[0092] The reinforcing agent is an ethylene vinyl acetate copolymer emulsion.

[0093] This embodiment also provides a method for preparing the above-mentioned bio-based adhesive, including the following steps:

[0094] S1. Dissolve 5g of carboxymethyl chitosan and 5g of gum arabic in 20mL (i.e., 20g) of water, then add 3g of polyethylene glycol (specifically polyethylene glycol 2000), and stir for 1 hour to obtain the first solution;

[0095] S2. Add 2g of ethylene vinyl acetate copolymer emulsion to the first solution and sonicate for 30min to obtain the second solution;

[0096] S3. Add 1.5g of polyvinyl alcohol to 35mL (i.e., 35g) of water and stir at 90℃ for 4h to obtain a polyvinyl alcohol solution.

[0097] S4. Add the second solution to the polyvinyl alcohol solution, then add 0.5g xanthan gum, 0.3g curcumin, and 0.2g defoamer, and continue stirring for 2.5h to obtain the bio-based adhesive.

[0098] Example 4

[0099] This application provides a bio-based adhesive comprising the following raw materials: 5g carboxymethyl chitosan, 5g gum arabic, 2g polyvinyl alcohol, 55mL (i.e., 55g) water, 0.2g defoamer, 0.3g preservative, 3g plasticizer, 0.5g thickener, and 2g reinforcing agent.

[0100] The defoamer is polymethylhydrosiloxane;

[0101] The preservative is curcumin;

[0102] The plasticizer is polyethylene glycol 2000;

[0103] The thickener is xanthan gum;

[0104] The reinforcing agent is an ethylene vinyl acetate copolymer emulsion.

[0105] This embodiment also provides a method for preparing the above-mentioned bio-based adhesive, including the following steps:

[0106] S1. Dissolve 5g of carboxymethyl chitosan and 5g of gum arabic in 20mL (i.e., 20g) of water, then add 3g of polyethylene glycol (specifically polyethylene glycol 2000), and stir for 1 hour to obtain the first solution;

[0107] S2. Add 2g of ethylene vinyl acetate copolymer emulsion to the first solution and sonicate for 30min to obtain the second solution;

[0108] S3. Add 2g of polyvinyl alcohol to 35mL (i.e., 35g) of water and stir at 90℃ for 4h to obtain a polyvinyl alcohol solution.

[0109] S4. Add the second solution to the polyvinyl alcohol solution, then add 0.5g xanthan gum, 0.3g curcumin, and 0.2g defoamer, and continue stirring for 2.5h to obtain the bio-based adhesive.

[0110] Example 5

[0111] This application provides a bio-based adhesive comprising the following raw materials: 5g carboxymethyl chitosan, 5g gum arabic, 2.5g polyvinyl alcohol, 55mL (i.e., 55g) water, 0.2g defoamer, 0.3g preservative, 3g plasticizer, 0.5g thickener, and 2g reinforcing agent.

[0112] The defoamer is polymethylhydrosiloxane;

[0113] The preservative is curcumin;

[0114] The plasticizer is polyethylene glycol 2000;

[0115] The thickener is xanthan gum;

[0116] The reinforcing agent is an ethylene vinyl acetate copolymer emulsion.

[0117] This embodiment also provides a method for preparing the above-mentioned bio-based adhesive, including the following steps:

[0118] S1. Dissolve 5g of carboxymethyl chitosan and 5g of gum arabic in 20mL (i.e., 20g) of water, then add 3g of polyethylene glycol (specifically polyethylene glycol 2000), and stir for 1 hour to obtain the first solution;

[0119] S2. Add 2g of ethylene vinyl acetate copolymer emulsion to the first solution and sonicate for 30min to obtain the second solution;

[0120] S3. Add 2.5g of polyvinyl alcohol to 35mL (i.e., 35g) of water and stir at 90℃ for 4h to obtain a polyvinyl alcohol solution.

[0121] S4. Add the second solution to the polyvinyl alcohol solution, then add 0.5g xanthan gum, 0.3g curcumin, and 0.2g defoamer, and continue stirring for 2.5h to obtain the bio-based adhesive.

[0122] Example 6

[0123] This application provides a bio-based adhesive comprising the following raw materials: 5g carboxymethyl chitosan, 5g gum arabic, 3g polyvinyl alcohol, 55mL (i.e., 55g) water, 0.2g defoamer, 0.3g preservative, 3g plasticizer, 0.5g thickener, and 2g reinforcing agent.

[0124] The defoamer is polymethylhydrosiloxane;

[0125] The preservative is curcumin;

[0126] The plasticizer is polyethylene glycol 2000;

[0127] The thickener is xanthan gum;

[0128] The reinforcing agent is an ethylene vinyl acetate copolymer emulsion.

[0129] This embodiment also provides a method for preparing the above-mentioned bio-based adhesive, including the following steps:

[0130] S1. Dissolve 5g of carboxymethyl chitosan and 5g of gum arabic in 20mL (i.e., 20g) of water, then add 3g of polyethylene glycol (specifically polyethylene glycol 2000), and stir for 1 hour to obtain the first solution;

[0131] S2. Add 2g of ethylene vinyl acetate copolymer emulsion to the first solution and sonicate for 30min to obtain the second solution;

[0132] S3. Add 3g of polyvinyl alcohol to 35mL (i.e., 35g) of water and stir at 90℃ for 4h to obtain a polyvinyl alcohol solution.

[0133] S4. Add the second solution to the polyvinyl alcohol solution, then add 0.5g xanthan gum, 0.3g curcumin, and 0.2g defoamer, and continue stirring for 2.5h to obtain the bio-based adhesive.

[0134] Example 7

[0135] This application provides a bio-based adhesive comprising the following raw materials: 5g carboxymethyl chitosan, 5g gum arabic, 3.5g polyvinyl alcohol, 55mL (i.e., 55g) water, 0.2g defoamer, 0.3g preservative, 3g plasticizer, 0.5g thickener, and 2g reinforcing agent.

[0136] The defoamer is polymethylhydrosiloxane;

[0137] The preservative is curcumin;

[0138] The plasticizer is polyethylene glycol 2000;

[0139] The thickener is xanthan gum;

[0140] The reinforcing agent is an ethylene vinyl acetate copolymer emulsion.

[0141] This embodiment also provides a method for preparing the above-mentioned bio-based adhesive, including the following steps:

[0142] S1. Dissolve 5g of carboxymethyl chitosan and 5g of gum arabic in 20mL (i.e., 20g) of water, then add 3g of polyethylene glycol (specifically polyethylene glycol 2000), and stir for 1 hour to obtain the first solution;

[0143] S2. Add 2g of ethylene vinyl acetate copolymer emulsion to the first solution and sonicate for 30min to obtain the second solution;

[0144] S3. Add 3.5g of polyvinyl alcohol to 35mL (i.e., 35g) of water and stir at 90℃ for 4h to obtain a polyvinyl alcohol solution.

[0145] S4. Add the second solution to the polyvinyl alcohol solution, then add 0.5g xanthan gum, 0.3g curcumin, and 0.2g defoamer, and continue stirring for 2.5h to obtain the bio-based adhesive.

[0146] Example 8

[0147] This application provides a bio-based adhesive comprising the following raw materials: 1g carboxymethyl chitosan, 5g gum arabic, 2.5g polyvinyl alcohol, 55mL (i.e., 55g) water, 0.2g defoamer, 0.3g preservative, 3g plasticizer, 0.5g thickener, and 2g reinforcing agent.

[0148] The defoamer is polymethylhydrosiloxane;

[0149] The preservative is curcumin;

[0150] The plasticizer is polyethylene glycol 2000;

[0151] The thickener is xanthan gum;

[0152] The reinforcing agent is an ethylene vinyl acetate copolymer emulsion.

[0153] This embodiment also provides a method for preparing the above-mentioned bio-based adhesive, including the following steps:

[0154] S1. Dissolve 1g of carboxymethyl chitosan and 5g of gum arabic in 20mL (i.e., 20g) of water, then add 3g of polyethylene glycol (specifically polyethylene glycol 2000), and stir for 1 hour to obtain the first solution;

[0155] S2. Add 2g of ethylene vinyl acetate copolymer emulsion to the first solution and sonicate for 30min to obtain the second solution;

[0156] S3. Add 2.5g of polyvinyl alcohol to 35mL (i.e., 35g) of water and stir at 90℃ for 4h to obtain a polyvinyl alcohol solution.

[0157] S4. Add the second solution to the polyvinyl alcohol solution, then add 0.5g xanthan gum, 0.3g curcumin, and 0.2g defoamer, and continue stirring for 2.5h to obtain the bio-based adhesive.

[0158] Example 9

[0159] This application provides a bio-based adhesive comprising the following raw materials: 2g carboxymethyl chitosan, 5g gum arabic, 2.5g polyvinyl alcohol, 55mL (i.e., 55g) water, 0.2g defoamer, 0.3g preservative, 3g plasticizer, 0.5g thickener, and 2g reinforcing agent.

[0160] The defoamer is polymethylhydrosiloxane;

[0161] The preservative is curcumin;

[0162] The plasticizer is polyethylene glycol 2000;

[0163] The thickener is xanthan gum;

[0164] The reinforcing agent is an ethylene vinyl acetate copolymer emulsion.

[0165] This embodiment also provides a method for preparing the above-mentioned bio-based adhesive, including the following steps:

[0166] S1. Dissolve 2g of carboxymethyl chitosan and 5g of gum arabic in 20mL (i.e., 20g) of water, then add 3g of polyethylene glycol (specifically polyethylene glycol 2000), and stir for 1 hour to obtain the first solution;

[0167] S2. Add 2g of ethylene vinyl acetate copolymer emulsion to the first solution and sonicate for 30min to obtain the second solution;

[0168] S3. Add 2.5g of polyvinyl alcohol to 35mL (i.e., 35g) of water and stir at 90℃ for 4h to obtain a polyvinyl alcohol solution.

[0169] S4. Add the second solution to the polyvinyl alcohol solution, then add 0.5g xanthan gum, 0.3g curcumin, and 0.2g defoamer, and continue stirring for 2.5h to obtain the bio-based adhesive.

[0170] Example 10

[0171] This application provides a bio-based adhesive comprising the following raw materials: 3g carboxymethyl chitosan, 5g gum arabic, 2.5g polyvinyl alcohol, 55mL (i.e., 55g) water, 0.2g defoamer, 0.3g preservative, 3g plasticizer, 0.5g thickener, and 2g reinforcing agent.

[0172] The defoamer is polymethylhydrosiloxane;

[0173] The preservative is curcumin;

[0174] The plasticizer is polyethylene glycol 2000;

[0175] The thickener is xanthan gum;

[0176] The reinforcing agent is an ethylene vinyl acetate copolymer emulsion.

[0177] This embodiment also provides a method for preparing the above-mentioned bio-based adhesive, including the following steps:

[0178] S1. Dissolve 3g of carboxymethyl chitosan and 5g of gum arabic in 20mL (i.e., 20g) of water, then add 3g of polyethylene glycol (specifically polyethylene glycol 2000), and stir for 1 hour to obtain the first solution;

[0179] S2. Add 2g of ethylene vinyl acetate copolymer emulsion to the first solution and sonicate for 30min to obtain the second solution;

[0180] S3. Add 2.5g of polyvinyl alcohol to 35mL (i.e., 35g) of water and stir at 90℃ for 4h to obtain a polyvinyl alcohol solution.

[0181] S4. Add the second solution to the polyvinyl alcohol solution, then add 0.5g xanthan gum, 0.3g curcumin, and 0.2g defoamer, and continue stirring for 2.5h to obtain the bio-based adhesive.

[0182] Comparative Example 1

[0183] This comparative example provides a bio-based adhesive comprising the following raw materials: 5g carboxymethyl chitosan, 2.5g polyvinyl alcohol, 55mL (i.e., 55g) water, 0.2g defoamer, 0.3g preservative, 3g plasticizer, 0.5g thickener, and 2g reinforcing agent.

[0184] The defoamer is polymethylhydrosiloxane;

[0185] The preservative is curcumin;

[0186] The plasticizer is polyethylene glycol 2000;

[0187] The thickener is xanthan gum;

[0188] The reinforcing agent is an ethylene vinyl acetate copolymer emulsion.

[0189] This comparative example also provides a method for preparing the above-mentioned bio-based adhesive, including the following steps:

[0190] S1. Dissolve 5g of carboxymethyl chitosan in 20mL (i.e., 20g) of water, then add 3g of polyethylene glycol (specifically polyethylene glycol 2000), and stir for 1 hour to obtain the first solution;

[0191] S2. Add 2g of ethylene vinyl acetate copolymer emulsion to the first solution and sonicate for 30min to obtain the second solution;

[0192] S3. Add 2.5g of polyvinyl alcohol to 35mL (i.e., 35g) of water and stir at 90℃ for 4h to obtain a polyvinyl alcohol solution.

[0193] S4. Add the second solution to the polyvinyl alcohol solution, then add 0.5g xanthan gum, 0.3g curcumin, and 0.2g defoamer, and continue stirring for 2.5h to obtain the bio-based adhesive.

[0194] Comparative Example 2

[0195] This comparative example provides a bio-based adhesive comprising the following raw materials: 5g carboxymethyl chitosan, 5g gum arabic, 2.5g polyvinyl alcohol, 55mL (i.e., 55g) water, 0.2g defoamer, 0.3g preservative, 3g plasticizer, and 0.5g thickener.

[0196] The defoamer is polymethylhydrosiloxane;

[0197] The preservative is curcumin;

[0198] The plasticizer is polyethylene glycol 2000;

[0199] The thickener is xanthan gum.

[0200] This comparative example also provides a method for preparing the above-mentioned bio-based adhesive, including the following steps:

[0201] S1. Dissolve 5g of carboxymethyl chitosan and 5g of gum arabic in 20mL (i.e., 20g) of water, then add 3g of polyethylene glycol (specifically polyethylene glycol 2000), and stir for 1 hour to obtain the first solution;

[0202] S2. Sonicate the first solution for 30 minutes to obtain the second solution;

[0203] S3. Add 2.5g of polyvinyl alcohol to 35mL (i.e., 35g) of water and stir at 90℃ for 4h to obtain a polyvinyl alcohol solution.

[0204] S4. Add the second solution to the polyvinyl alcohol solution, then add 0.5g xanthan gum, 0.3g curcumin, and 0.2g defoamer, and continue stirring for 2.5h to obtain the bio-based adhesive.

[0205] Performance testing

[0206] The adhesives prepared in Examples 1-10 and Comparative Examples 1-2 were used as adhesives to prepare three-layer poplar plywood. The adhesive was applied manually by brush, with the middle layer plywood applied to both sides. The veneers were 40cm × 40cm × 0.15cm poplar boards (40cm long, 40cm wide, and 0.15cm high). Before the experiment, all veneers were dried in a constant temperature drying oven at 40℃ to control the moisture content to 10-12%. The bonding strength was then tested on a universal tensile testing machine. The coated plywood was then subjected to hot-pressing in a flat vulcanizing apparatus at a pressure of 2 MPa and a temperature of 150℃ for 7 minutes. The performance of the cooled plywood was tested according to GB / T17657-1999 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels". All samples were tested in triplicate, and the average value was taken. The test results are shown in Table 1.

[0207] Table 1 - Bond strength of plywood prepared with bio-based adhesives from different embodiments

[0208]

[0209]

[0210] As can be seen from Table 1, the plywood prepared using the bio-based adhesive of the present invention has strong bonding strength; specifically, the plywood prepared using the bio-based adhesive in Example 5 has the highest bonding strength of 1.97 MPa. In Examples 1-7, as the content of polyvinyl alcohol in the bio-based adhesive increases, the bonding strength of the prepared plywood first increases and then decreases. This is because the polyvinyl alcohol molecular chains play a cross-linking and toughening role in the matrix of carboxymethyl chitosan and gum arabic. Within a certain range, the increase of polyvinyl alcohol promotes hydrogen bond cross-linking between molecular chains, increases viscosity, and when the amount is too high, the fluidity of the material deteriorates, the mobility of the molecular chains decreases, and the adhesive performance of the adhesive is affected.

[0211] As can be seen from Examples 8-10, the bonding strength of the plywood improved with the increase of carboxymethyl chitosan. The plywood prepared using the adhesive in Comparative Example 1 had a bonding strength of 1.64 MPa, indicating that the content of the biomass material gum arabic has a significant impact on the bonding strength of the adhesive. The plywood prepared using the adhesive in Comparative Example 2 had a bonding strength of 1.61 MPa. Compared with Example 5, this demonstrates the reinforcing effect of the reinforcing agent on the adhesive; adhesives lacking the reinforcing agent have insufficient cross-linking and degraded performance.

[0212] Furthermore, the adhesive prepared in Example 5 was used as the adhesive material to prepare three-layer poplar plywood, using the same method as above. The coated plywood was then placed in a flat vulcanizing apparatus for hot pressing at a pressure of 2 MPa and a temperature range of 70–170°C (specifically 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, and 170°C) for 7 minutes. The performance of the cooled plywood was tested according to GB / T17657-1999 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels". All samples were tested in triplicate, and the average value was taken. The test results are shown in Table 2.

[0213] Table 2 - Adhesive strength of the adhesive in Example 5 at different temperatures

[0214] temperature Bond strength (MPa) 70℃ 1.65 80℃ 1.72 90℃ 1.77 100℃ 1.82 110℃ 1.84 120℃ 1.87 130℃ 1.92 140℃ 1.93 150℃ 1.97 160℃ 1.94 170℃ 1.89

[0215] As shown in Table 2, the plywood prepared in Example 5 exhibits different bonding strengths at different temperatures, with higher temperatures resulting in stronger bonding. The adhesive's fluidity varies at different temperatures; increased temperature promotes contact between the adhesive and the plywood, leading to more uniform adhesion. Furthermore, the more complex the entanglement of various molecular chains in the adhesive, the higher the bonding strength of the plywood. Table 2 also shows that the bio-based adhesive exhibits relatively stable performance at high temperatures.

[0216] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A bio-based adhesive, characterized in that, The raw materials include the following parts by weight: 10 parts biomass matrix, 2.0-3.5 parts polyvinyl alcohol, 30-100 parts water, 0.2 parts defoamer, 0.3 parts preservative, 3 parts plasticizer, 0.5 parts thickener, and 2 parts reinforcing agent; The biomass matrix comprises a mixture of gum arabic and carboxymethyl chitosan; The mass ratio of gum arabic to carboxymethyl chitosan is 1:1; The thickener is xanthan gum; The preservative is curcumin; The plasticizer is polyethylene glycol; The reinforcing agent is an ethylene vinyl acetate copolymer emulsion; The defoamer is polymethylhydrosiloxane; The method for preparing the bio-based adhesive includes the following steps: The biomass matrix was added to a portion of water, then a plasticizer was added, and the mixture was stirred to obtain the first solution; The reinforcing agent is added to the first solution and mixed to obtain the second solution; Add polyvinyl alcohol to the remaining water and stir to obtain a polyvinyl alcohol solution; The second solution is added to the polyvinyl alcohol solution, followed by the addition of thickener, preservative, and defoamer. The mixture is then stirred to obtain the bio-based adhesive.

2. A method for preparing the bio-based adhesive as described in claim 1, characterized in that, Includes the following steps: The biomass matrix was added to a portion of water, then a plasticizer was added, and the mixture was stirred to obtain the first solution; The reinforcing agent is added to the first solution and mixed to obtain the second solution; Add polyvinyl alcohol to the remaining water and stir to obtain a polyvinyl alcohol solution; The second solution is added to the polyvinyl alcohol solution, followed by the addition of thickener, preservative, and defoamer. The mixture is then stirred to obtain the bio-based adhesive.

3. The method for preparing the bio-based adhesive as described in claim 2, characterized in that, In the step of adding the biomass matrix to a portion of water, the water is 10 to 30 parts by weight. The reinforcing agent is added to the first solution and mixed ultrasonically to obtain the second solution; Add polyvinyl alcohol to the remaining water and stir at 80-100°C to obtain a polyvinyl alcohol solution.

4. The application of a bio-based adhesive as described in claim 1 or a bio-based adhesive prepared by any of the preparation methods described in claims 2 to 3 in the processing of plywood and blockboard.

Images