Adhesive as well as preparation method and bonding system thereof

Abstract

The invention discloses an adhesive, a preparation method thereof and a bonding system, raw materials of the adhesive comprise vegetable protein, a cross-linking agent and a modifier, the cross-linking agent contains an epoxy group and a hydrophilic group, and the modifier contains a triazine ring structure. The adhesive at least comprises a cross-linked structure of the following components: a cross-linked structure between the vegetable protein and the cross-linking agent, a cross-linked structure between the cross-linking agent and the modifier, and a cross-linked structure between the vegetable protein and the modifier. The adhesive provided by the invention has good heat resistance and hydrophilicity.

Description

Technical Field

[0001] The present application relates to the field of bonding technology, and in particular to an adhesive and a preparation method thereof, and a bonding system. Background Art

[0002] Plant protein-based adhesives are adhesives made primarily from plant proteins (such as soybeans, corn, and wheat). Plant proteins exhibit excellent adhesive properties after appropriate chemical or physical treatment. Due to their natural origin, they are safe, biodegradable, and renewable, and are used in areas such as wood processing, electronic packaging, and medical materials. Soy protein glue is a typical plant protein-based adhesive, primarily made from soy flour, a rich source of protein. Modification or formulation adjustments can optimize its adhesive properties.

[0003] Current plant protein-based adhesives have the following drawbacks: insufficient heat resistance, prone to degradation and loss of adhesion at high temperatures; and highly heat-resistant plant protein adhesives exhibit strong hydrophobicity after curing, limiting their use in humid environments or for biocompatibility applications. In other words, existing plant protein-based adhesives struggle to simultaneously meet the requirements for both high-temperature resistance and hydrophilicity.

[0004] Therefore, it is necessary to provide an adhesive with good heat resistance and hydrophilicity. Summary of the Invention

[0005] The present application provides an adhesive and a preparation method thereof, and an adhesive system, which are used to solve the problem that existing plant protein-based adhesives are difficult to simultaneously meet the requirements of high temperature resistance and hydrophilicity.

[0006] The present application discloses an adhesive, the raw materials of which include the following components: plant protein, a cross-linking agent, and a modifier. The cross-linking agent contains an epoxy group and a hydrophilic group, and the modifier contains a triazine ring structure. The adhesive includes at least a cross-linked structure of the following components: a cross-linked structure between the plant protein and the cross-linking agent, a cross-linked structure between the cross-linking agent and the modifier, and a cross-linked structure between the plant protein and the modifier.

[0007] In one implementation of the present application, the plant protein includes at least one of the following: soy protein, gluten, corn protein, peanut protein, potato protein, and pea protein.

[0008] In one implementation of the present application, the cross-linking agent includes at least one of the following: polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, dimethylol propionic acid diglycidyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, and pentaerythritol polyglycidyl ether.

[0009] In one implementation of the present application, the modifier includes at least one of the following structures: Wherein, R1 to R8 are each independently selected from: amino, hydroxy, aminoalkyl, hydroxyalkyl.

[0010] In one implementation of the present application, the modifier includes at least one of the following: 2,4,6-triamino-1,3,5-triazine (melamine), 2,4-diamino-1,3,5-triazine, and 2,4-diamino-6-hydroxy-1,3,5-triazine.

[0011] In one implementation of the present application, the raw material of the adhesive further includes a filler, and the filler includes nanocellulose.

[0012] In one implementation of the present application, the raw materials of the adhesive include, by weight: 80 to 120 parts of the plant protein, 15 to 25 parts of the cross-linking agent, 5 to 10 parts of the modifier, and 8 to 15 parts of the filler.

[0013] The present application also discloses a method for preparing an adhesive, which is used to prepare the above-mentioned adhesive. The preparation method includes: dispersing plant protein and a modifier in deionized water, and obtaining a pre-cross-linked product under alkaline conditions; adding a cross-linking agent to the pre-cross-linked product, mixing, and conducting a cross-linking reaction to obtain a reaction product to obtain the adhesive; wherein the cross-linking agent contains an epoxy group and a hydrophilic group, and the modifier contains a triazine ring structure, and the adhesive includes at least a cross-linked structure of the following components: a cross-linked structure between the plant protein and the cross-linking agent, a cross-linked structure between the cross-linking agent and the modifier, and a cross-linked structure between the plant protein and the modifier.

[0014] The present application also discloses a bonding system, comprising a curing agent and the above-mentioned adhesive, wherein the curing agent comprises a polyether polyol containing an isocyanate group, and the curing agent is used to cure the adhesive.

[0015] In one implementation of the present application, the mass fraction of the isocyanate group in the polyether polyol is 3% to 5%.

[0016] In one implementation of the present application, the polyether polyol contains a polyoxypropylene segment and a polyoxyethylene segment, wherein the mass fraction of the polyoxyethylene segment in the polyether polyol is ≥75%.

[0017] The beneficial effects of this application are:

[0018] The adhesive of the present application can improve the hydrophilicity of the adhesive by using a crosslinking agent containing a hydrophilic group, and can improve the heat resistance of the adhesive by using a modifier containing a triazine ring, thereby providing an adhesive with good heat resistance and hydrophilicity. DETAILED DESCRIPTION

[0019] The present invention is described in further detail below by specific embodiments. In the following embodiments, many details are described in order to make the present application better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other materials or methods. In some cases, some operations related to the present application are not shown or described in the specification. This is to avoid the core part of the present application being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail. They can fully understand the related operations based on the description in the specification and the general technical knowledge in this area.

[0020] In addition, the features, operations, or characteristics described in this specification may be combined in any appropriate manner to form various embodiments. Furthermore, the steps or actions in the method description may be reordered or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various sequences in this specification are provided solely for the purpose of clearly describing an embodiment and are not intended to be mandatory, unless otherwise specified.

[0021] The serial numbers assigned to the components in this document, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning.

[0022] Existing plant protein-based adhesives have the following shortcomings: insufficient temperature resistance (≤120°C) and easy degradation and loss of adhesion at high temperatures; high-temperature-resistant plant protein adhesives are highly hydrophobic after curing (contact angle >90°), limiting their application in humid environments or biocompatibility scenarios; and they rely on toxic cross-linking agents such as formaldehyde, making them less environmentally friendly.

[0023] In view of this, the present application provides an adhesive with good heat resistance and hydrophilicity. The adhesive of the present application can remain stable in high temperature environments (≥150°C); after curing, it is insoluble in water but has good hydrophilicity, with a contact angle with water of less than 45°; it does not contain formaldehyde and is environmentally friendly.

[0024] In one embodiment, an adhesive is provided.

[0025] In one specific embodiment, the adhesive's raw materials include plant protein, a crosslinker, and a modifier. The crosslinker contains an epoxy group and a hydrophilic group, and the modifier contains a triazine ring structure. The adhesive includes at least the following crosslinked structures: a crosslinked structure between the plant protein and the crosslinker, a crosslinked structure between the crosslinker and the modifier, and a crosslinked structure between the plant protein and the modifier. It should be noted that the crosslinked structures in this application are not limited to structures formed by chemical bonds, but also include structures formed by hydrogen bonds and van der Waals forces. Plant protein, as an adhesive raw material, has the following advantages: it has film-forming properties and can form a continuous film under certain conditions, effectively achieving adhesion to objects; plant protein molecules contain a large number of polar groups, such as hydroxyl, amino, and carboxyl groups, which can form hydrogen bonds with polar groups on the surface of the adherend, generating adhesion; van der Waals forces exist between the plant protein molecules and the adherend surface, helping to improve the bonding strength between the adhesive and the adherend; plant protein is widely available, a renewable resource, and has good biodegradability.

[0026] In a specific embodiment, the plant protein includes, but is not limited to, soy protein, gluten, corn protein, peanut protein, potato protein, and pea protein. The plant protein may also be protein from other plant sources.

[0027] In one specific embodiment, the modifier contains a triazine ring structure. It should be noted that the triazine ring structure is a six-membered heterocyclic ring containing three nitrogen atoms, with a chemical formula of C3H3N3. Depending on the position of the nitrogen atoms in the ring, the triazine ring has three isomers: 1,2,3-triazine, 1,2,4-triazine, and 1,3,5-triazine. The introduction of the triazine ring structure can provide the adhesive with higher thermal stability.

[0028] In a specific embodiment, at least one of the following structures is included: Wherein, R1 to R8 are each independently selected from: amino, hydroxyl, aminoalkyl (aminoalkyl refers to a structure in which one or more amino groups are connected to an alkyl chain, for example: aminoethyl -CH2CH2NH2), hydroxyalkyl (hydroxyalkyl refers to a structure in which one or more hydroxyl groups are connected to an alkyl chain, for example: hydroxymethyl -CH2OH). For example, R1 can be selected from amino, hydroxyl, aminoalkyl, hydroxyalkyl, and R2 can also be selected from amino, hydroxyl, aminoalkyl, and hydroxyalkyl. Further, R1 to R8 are each independently amino or hydroxyl. Further still, at least one of R1, R2, and R3 is amino, at least one of R4, R5, and R6 is amino, and at least one of R7 and R8 is amino.

[0029] In one embodiment, the modifier comprises at least one of the following structures: Wherein, R1 to R3 are each independently selected from: amino, hydroxyl, aminoalkyl, hydroxyalkyl. It should be noted that 1,3,5-triazine (s-triazine) has a high degree of symmetry. The symmetrical molecular structure makes the intermolecular forces more uniform and the molecular arrangement more compact and orderly. During the heating process, this orderly structure can better resist the damage caused by thermal motion and maintain the stability of the molecule. At the same time, the symmetry also makes the physical and chemical properties of the molecule in all directions more consistent, and it is not easy to have thermal instability caused by local structural differences. Therefore, the thermal stability of the adhesive can be further improved. Furthermore, R1 to R3 are each independently amino or hydroxyl. Further, at least one of R1, R2, and R3 is an amino group. Further, R1, R2, and R3 are all amino groups.

[0030] In one embodiment, the modifier includes at least one of the following: 2,4,6-triamino-1,3,5-triazine (melamine), 2,4-diamino-1,3,5-triazine, and 2,4-diamino-6-hydroxy-1,3,5-triazine. It should be noted that the triazine ring structure can improve thermal stability, and the multiple amino groups on the ring can undergo a ring-opening grafting reaction with the epoxy groups of the crosslinking agent.

[0031] In one embodiment, the crosslinking agent contains epoxy groups. It has high reactivity and can undergo nucleophilic ring-opening reaction with the amino group of the modifier and the amino group in the protein molecule to form a covalent bond, so that the modifier and the protein molecules are cross-linked through the cross-linking agent.

[0032] In one embodiment, the crosslinking agent contains a hydrophilic group, which may include at least one of the following: a hydroxyl group (-OH), an amino group (-NH2), a carboxyl group (-COOH), a phosphate group (-PO3H2), or an oxyethylene group (-CH2CH2O-).

[0033] In a specific embodiment, the cross-linking agent may include at least one of the following: polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, dimethylol propionic acid diglycidyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, and pentaerythritol polyglycidyl ether. It should be noted that the polyethylene glycol segment in the polyethylene glycol diglycidyl ether molecule is composed of repeated oxyethylene (-CH2CH2O-) units, in which the ether bond oxygen atom has a lone pair of electrons and can form hydrogen bonds with hydrogen atoms in water molecules, thereby showing hydrophilicity; the glycerol part of glycerol diglycidyl ether contains multiple hydroxyl groups, which are strong hydrophilic groups and can form hydrogen bonds with water molecules, making glycerol diglycidyl ether have a certain hydrophilicity; the dimethylolpropionic acid part of dimethylolpropionic acid diglycidyl ether contains two hydroxyl groups and one carboxyl group, and the carboxyl group can partially ionize hydrogen ions in water and can form hydrogen bonds with water molecules. The hydroxyl group can also form hydrogen bonds with water, so the substance has hydrophilicity; the ethylene glycol part of ethylene glycol diglycidyl ether contains two hydroxyl groups, which can form hydrogen bonds with water molecules, thereby giving the substance A certain degree of hydrophilicity; the 1,4-butanediol part of 1,4-butanediol diglycidyl ether contains two hydroxyl groups, and the hydroxyl groups form hydrogen bonds with water molecules, which makes the substance hydrophilic; polypropylene glycol diglycidyl ether is similar to polyethylene glycol diglycidyl ether. The ether bond oxygen atoms in the polypropylene glycol chain segment can form hydrogen bonds with water molecules, making it hydrophilic to a certain extent. However, due to the presence of methyl groups in the structure of polypropylene glycol, its hydrophilicity is usually slightly weaker than that of polyethylene glycol diglycidyl ether; the sorbitol in sorbitol polyglycidyl ether is a polyol and contains multiple hydroxyl groups. These hydroxyl groups can form hydrogen bonds with water molecules, which is the main reason for the hydrophilicity of sorbitol polyglycidyl ether; the pentaerythritol in pentaerythritol polyglycidyl ether contains four hydroxyl groups, and the hydrogen bonding between hydroxyl groups and water molecules makes pentaerythritol polyglycidyl ether hydrophilic.

[0034] In one embodiment, the cross-linking agent may be polyethylene glycol diglycidyl ether.

[0035] In a specific embodiment, the molecular weight of polyethylene glycol diglycidyl ether can be 400 Da to 1000 Da. For example, the molecular weight of polyethylene glycol diglycidyl ether can be 400 Da, 500 Da, 600 Da, 700 Da, 800 Da, 900 Da or 1000 Da.

[0036] In one embodiment, the adhesive has a three-dimensional cross-linked network structure.

[0037] In a specific embodiment, the adhesive may include at least one of the following cross-linked structures: a cross-linked structure between a plant protein and a cross-linking agent, a cross-linked structure between a cross-linking agent and a modifier, and a cross-linked structure between a plant protein and a modifier. It should be noted that the cross-linked structure between a plant protein and a cross-linking agent refers to a connection between one plant protein molecule and one cross-linking agent molecule, the cross-linked structure between a modifier and one modifier refers to a connection between one modifier molecule and one modifier molecule, and the cross-linked structure between a plant protein and a modifier refers to a connection between one plant protein molecule and one modifier molecule.

[0038] In a specific embodiment, the adhesive comprises at least a cross-linked structure of the following components: a cross-linked structure between the plant protein and the cross-linking agent, a cross-linked structure between the cross-linking agent and the modifier, and a cross-linked structure between the plant protein and the modifier.

[0039] In a specific embodiment, the following components can be cross-linked by a cross-linking agent: cross-linking between plant proteins, and / or cross-linking between modifiers, and / or cross-linking between plant proteins and modifiers.

[0040] In a specific embodiment, the raw material of the adhesive may further include fillers.

[0041] In a specific embodiment, the filler may include nanocellulose. It should be noted that nanocellulose is a cellulose material with nanoscale characteristics. Nanocellulose is mainly composed of cellulose molecules. Cellulose is a linear polymer composed of glucose units connected by β-1,4-glycosidic bonds. In nanocellulose, cellulose molecular chains are aggregated together through interactions such as hydrogen bonds to form a fiber structure with nanoscale dimensions. Its diameter is usually between a few nanometers and hundreds of nanometers, and its length can range from tens of nanometers to several microns. The addition of nanocellulose can synergistically improve the hydrophilicity of the adhesive with a cross-linking agent, and at the same time can improve the heat resistance and strength of the colloid itself, because nanocellulose is essentially cellulose, which has high heat resistance and a temperature resistance of more than 200°C. Nanocellulose, as a filler, can play a role in nano-reinforcement. The principle of nano-reinforcement is as follows: nanomaterials have extremely small sizes (usually between 1 and 100 nanometers) and large specific surface areas, which enable them to form a large number of interfacial bonds with the matrix material. When the matrix material is subjected to external forces, the nanomaterials can transfer stress through the interface, thereby effectively dispersing the external forces and improving the strength and toughness of the material; the highly active surface of the nanomaterials can also chemically react or physically adsorb with the matrix to form chemical bonds or physical cross-linking points, increasing the cross-linking density inside the matrix and further improving the performance of the material.

[0042] In a specific embodiment, the raw material of the adhesive may further include a solvent.

[0043] In one embodiment, the solvent may be water.

[0044] In one specific embodiment, the adhesive raw materials may include 80 to 120 parts by weight of plant protein. For example, the adhesive raw materials may include 80, 90, 100, 110, or 120 parts of plant protein. It should be noted that using an appropriate amount of plant protein can provide the adhesive with suitable bonding strength.

[0045] In a specific embodiment, the adhesive raw materials may include 15 to 25 parts by weight of a crosslinking agent. For example, the adhesive raw materials may include 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 parts of a crosslinking agent. It should be noted that by using an appropriate amount of crosslinking agent, the adhesive can be provided with suitable bonding strength, curing time, and hydrophilicity.

[0046] In a specific embodiment, the raw materials of the adhesive may include 5 to 10 parts of a modifier by weight. For example, the raw materials of the adhesive may include 5, 6, 7, 8, 9, or 10 parts of a modifier. It should be noted that by using an appropriate amount of the modifier, the adhesive can be provided with suitable heat resistance and hydrophilicity. Since triazine ring structure substances such as melamine are poorly soluble in water, their addition will weaken the hydrophilicity of the adhesive. Therefore, adding too much modifier will lead to poor wettability of the adhesive with water, while adding too little modifier may not sufficiently improve the heat resistance.

[0047] In one specific embodiment, the adhesive raw materials may include 8 to 15 parts of filler by weight. For example, the adhesive raw materials may include 8, 9, 10, 11, 12, 13, 14, or 15 parts of filler. It should be noted that by using an appropriate amount of filler, the adhesive can be provided with suitable heat resistance, hydrophilicity, strength, etc.

[0048] In a specific embodiment, the adhesive raw materials may include 200 to 250 parts by weight of solvent. For example, the adhesive raw materials may include 200, 210, 220, 230, 240, or 250 parts of solvent. It should be noted that by using an appropriate amount of solvent, the adhesive can provide suitable viscosity, curing speed, and bonding strength.

[0049] It should be noted that in the adhesive of the present application, the raw materials are interrelated and synergistic with each other, and through appropriate proportions, an adhesive with good hydrophilicity and heat resistance, appropriate bonding strength and appropriate curing rate is obtained.

[0050] In a specific embodiment, the adhesive can remain stable in a high temperature (≥150° C.) environment with almost no degradation (degradation rate is less than 1%).

[0051] In a specific embodiment, the adhesive is insoluble in water after curing, but has good hydrophilicity, with a contact angle with water less than 45°.

[0052] In a specific embodiment, the adhesive does not contain formaldehyde and is environmentally friendly.

[0053] This application also relates to a method for preparing an adhesive. The method may include: dispersing a plant protein and a modifier in deionized water under alkaline conditions to obtain a pre-crosslinked product (step S100); adding a crosslinking agent to the pre-crosslinked product, mixing the mixture, and performing a crosslinking reaction to obtain a reaction product, thereby obtaining an adhesive (step S200). It should be noted that the various components and their proportions involved in the preparation method can be found in the aforementioned content.

[0054] In a specific embodiment, in step S100, the plant protein and the modifier are placed in an alkaline environment (pH 10-11), which can activate the plant protein and the modifier, deprotonate the primary amino groups (-NH2) in the plant protein and the modifier, and generate highly reactive -NH - .

[0055] In a specific embodiment, in step S100, by pre-crosslinking the plant protein and the modifier, the adhesive system can be made more uniform, and the modifier can be more evenly distributed on the adhesive molecular chain, which can facilitate better utilization of the modifier to improve the heat resistance of the adhesive.

[0056] In a specific embodiment, in step S200 , the cross-linking reaction is performed at 70° C. to 90° C. The cross-linking reaction time may be 2 hours to 4 hours.

[0057] In a specific embodiment, step S200 further includes mixing the reaction product and the filler at 40° C. to 60° C. The mixing may include at least one of ultrasonic dispersion and stirring. The mixing time may be 20 min to 40 min.

[0058] The present application also relates to an adhesive system comprising a curing agent and the aforementioned adhesive. The adhesive system of the present application may also be referred to as a "two-component adhesive." A two-component adhesive is an adhesive system composed of two independent components, typically a base adhesive and a curing agent, which are packaged separately and need to be mixed in a specific ratio before use to convert the fluid adhesive into a solid with high strength and durability to achieve its bonding effect.

[0059] In one embodiment, the curing agent comprises a polyether polyol containing isocyanate groups (-N=C=O). It should be noted that the isocyanate groups can react with the amino groups on the soy protein, increasing the degree of crosslinking and improving heat resistance. Furthermore, the curing agent is also hydrophilic, which can help improve the hydrophilicity of the adhesive system. Furthermore, the isocyanate groups are highly reactive and can complete the reaction at room temperature. Therefore, the adhesive and curing agent of this application can be processed at room temperature (below 30°C).

[0060] In a specific embodiment, the content of isocyanate groups in a polyether polyol containing isocyanate groups can be 3% to 5%. The content of 3% to 5% here refers to a mass fraction of 3% to 5%. For example, the content of isocyanate groups in a polyether polyol containing isocyanate groups can be 3%, 3.5%, 4%, 4.5%, or 5%. It should be noted that an appropriate isocyanate group content is conducive to achieving appropriate bonding strength and hydrophilicity in the adhesive. Too low an isocyanate group content may result in insufficient crosslinking of the adhesive, affecting curing. Too high an isocyanate group content may result in a lack of hydrophilicity in the cured colloid.

[0061] In a specific embodiment, the polyether polyol contains PO segments (segments formed by polymerization of propylene oxide (PO)) and EO segments (segments formed by polymerization of ethylene oxide (EO), wherein the EO link content accounts for more than 75%, which helps to ensure that the curing agent has a certain degree of hydrophilicity. Here, the EO link content accounts for more than 75% means that the mass fraction of EO links in the polyether polyol is more than 75%. For example, the EO link content in the polyether polyol is 75%, 80% or 85%, etc.

[0062] In a specific embodiment, the weight percentage of the curing agent may be 8 to 15 parts. For example, the weight percentage of the curing agent may be 8, 9, 10, 11, 12, 13, 14 or 15 parts.

[0063] This application also relates to a method for using an adhesive system, comprising: mixing a curing agent and an adhesive in a predetermined ratio to form a mixture; placing the mixture on an object to be bonded, and curing the mixture at room temperature to achieve bond strength. The amounts of the curing agent and adhesive used may refer to the weight percentages of the aforementioned components.

[0064] The present invention is further described in detail below by specific experimental process and experimental data examples. The following examples are only used to further illustrate the present invention and should not be construed as limiting the present invention. In the present embodiment, unless otherwise specified, the reagents and instruments used are all commercially available, and the experimental operations are all carried out in accordance with the product specifications and conventional experimental specifications.

[0065] Example:

[0066] (1) Preparation of adhesive:

[0067] Pre-crosslinking: Disperse 100g of soy protein isolate (SPI) and 5g of melamine in 200g of deionized water, add NaOH to adjust the pH to 10.5, and stir at 70℃ for 1h. This step can cause pre-crosslinking between the soy protein isolate and melamine, making the adhesive system more uniform, evenly distributing the melamine on the molecular chain, and improving the heat resistance of the adhesive. In addition, this step can also deprotonate the primary amino groups (-NH2) in the soy protein isolate and melamine to generate highly reactive -NH - .

[0068] Epoxy ring-opening grafting reaction: 15 g of polyethylene glycol diglycidyl ether (molecular weight about 600 Da) was added and reacted at 80° C. for 3 h to generate a graft copolymer.

[0069] Nanocellulose composite: 10 g of nanocellulose was added, stirred evenly, and ultrasonically dispersed at 50°C for 30 min to obtain an adhesive.

[0070] (2) Curing:

[0071] Add 10g of curing agent (polyether polyol with isocyanate groups, isocyanate group content of 5%, wherein the polyether polyol contains PO segments and EO segments, and the EO segment content accounts for 80%) to the adhesive, stir evenly, and let it stand at room temperature for more than 24 hours to achieve bonding strength.

[0072] (3) Testing:

[0073] In accordance with the requirements of ISO 4587 "Adhesives - Determination of tensile lap shear strength of high-strength adhesives", the following performance tests were performed on the cured adhesive. The test conditions and results are as follows:

[0074] Temperature resistance test: The shear strength of the adhesive was measured at 150°C and the result was 1.02 MPa.

[0075] Heat and humidity resistance test: under the conditions of 85°C and 85% RH (relative humidity), the strength retention rate was 83% after 1000 hours.

[0076] The above content is a further detailed description of the present application in conjunction with specific implementation methods, and the specific implementation of the present application cannot be considered to be limited to these descriptions. For ordinary technicians in the technical field to which the present application belongs, several simple deductions or substitutions can be made without departing from the concept of the present application.

Claims

1. An adhesive, characterized in that: The raw materials of the adhesive include the following components: plant protein, a cross-linking agent, and a modifier. The cross-linking agent contains an epoxy group and a hydrophilic group, and the modifier contains a triazine ring structure. The adhesive includes at least a cross-linked structure of the following components: a cross-linked structure between the plant protein and the cross-linking agent, a cross-linked structure between the cross-linking agent and the modifier, and a cross-linked structure between the plant protein and the modifier.

2. The adhesive according to claim 1, characterized in that The plant protein comprises at least one of the following: soy protein, gluten, corn protein, peanut protein, potato protein, and pea protein.

3. The adhesive according to claim 1, characterized in that The crosslinking agent includes at least one of the following: polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, dimethylol propionic acid diglycidyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, and pentaerythritol polyglycidyl ether.

4. The adhesive according to claim 1, characterized in that The modifier comprises at least one of the following structures: Wherein, R1 to R8 are each independently selected from: amino, hydroxy, aminoalkyl, hydroxyalkyl.

5. The adhesive according to claim 4, characterized in that The modifier includes at least one of the following: 2,4,6-triamino-1,3,5-triazine, 2,4-diamino-1,3,5-triazine, and 2,4-diamino-6-hydroxy-1,3,5-triazine.

6. The adhesive according to claim 1, characterized in that The raw materials of the adhesive further include fillers, and the fillers include nanocellulose.

7. The adhesive according to claim 6, characterized in that In parts by weight, the raw materials of the adhesive include: 80 to 120 parts of the plant protein, 15 to 25 parts of the cross-linking agent, 5 to 10 parts of the modifier, and 8 to 15 parts of the filler.

8. A method for preparing an adhesive, characterized in that: For preparing the adhesive according to any one of claims 1 to 7, the preparation method comprises: Dispersing the plant protein and the modifier in deionized water under alkaline conditions to obtain a pre-crosslinked product; adding a crosslinking agent to the pre-crosslinked product and mixing them to perform a crosslinking reaction to obtain a reaction product, thereby obtaining the adhesive; Among them, the cross-linking agent contains an epoxy group and a hydrophilic group, the modifier contains a triazine ring structure, and the adhesive includes at least a cross-linking structure of the following components: a cross-linking structure between the plant protein and the cross-linking agent, a cross-linking structure between the cross-linking agent and the modifier, and a cross-linking structure between the plant protein and the modifier.

9. An adhesive system, characterized in that: The adhesive comprises a curing agent and the adhesive according to any one of claims 1 to 7, wherein the curing agent comprises a polyether polyol containing an isocyanate group, and the curing agent is used to cure the adhesive.

10. The adhesive system according to claim 9, characterized in that In the polyether polyol, the mass fraction of isocyanate groups is 3% to 5%; And / or, the polyether polyol contains a polyoxypropylene segment and a polyoxyethylene segment, wherein, in the polyether polyol, the mass fraction of the polyoxyethylene segment is ≥75%.

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