Vegetable protein-based bamboo wood adhesive, preparation method thereof and application of vegetable protein-based bamboo wood adhesive in thin shaving board

Abstract

The invention discloses a vegetable protein-based bamboo and wood adhesive, a preparation method thereof and application of the vegetable protein-based bamboo and wood adhesive in a thin shaving board. The vegetable protein-based bamboo and wood adhesive is prepared from the following raw materials: cake meal isolated protein, a silane coupling agent and a composite modifier, the composite modifier is prepared from the following raw materials: pullulan modified with aldehyde groups and a compound modified with boric acid ester bonds; the compound modified with the boric acid ester bond is prepared from the following raw materials: ellagic acid and 4-hydroxymethyl phenylboronic acid. According to the vegetable protein-based bamboo wood adhesive provided by the invention, the flame retardant property is improved.

Description

Technical Field

[0001] The invention belongs to a board modifier, and in particular relates to a plant protein-based bamboo-wood adhesive, a preparation method thereof, and application of the adhesive in a thin particle board. Background Art

[0002] Fast-growing forest wood, such as poplar plantations, has the advantages of rapid growth and high yield, but its low wood density, poor mechanical strength, insufficient surface hardness, weak wear resistance and corrosion resistance and other defects limit its wide application. Compared with natural forest wood, fast-growing forest wood has a large gap in material properties and decorative properties. Therefore, improving the physical and chemical properties of fast-growing forest wood, especially through chemical modification, has become one of the key ways to enhance its application value. At present, the research direction of chemically modified wood is mainly focused on the application of wood adhesives. In particular, formaldehyde-based resins (such as urea-formaldehyde resin (UF), melamine-formaldehyde resin (MF), phenol-formaldehyde resin (PF), etc.) have become the most commonly used adhesives in the wood industry due to their excellent bonding strength, water resistance and weather resistance, accounting for about 90% of the market share. However, a major defect of formaldehyde-based resins is their formaldehyde release problem. The potential harm of formaldehyde to human health and the environment has become a focus of widespread concern, especially today when laws and regulations are becoming increasingly stringent, and the use of formaldehyde-based adhesives is facing increasing pressure. Therefore, the development of new non-toxic, green and environmentally friendly wood adhesives has become an important demand for the development of the industry. As a natural and environmentally friendly adhesive material, protein-based adhesives have received increasing attention in recent years. Protein-based adhesives use natural protein as the main component, have good biodegradability, low toxicity and excellent bonding properties, and meet the requirements of green environmental protection. However, traditional protein-based adhesives still face many technical challenges in practical applications. Specifically, protein-based adhesives have weak flame retardant properties. In order to improve the flame retardant properties of protein-based adhesives, it is usually necessary to add more flame retardants or improve their formulas, for example, introducing inorganic flame retardant materials, phosphorus-based or nitrogen-based flame retardants to improve the flame retardant effect. However, due to the chemical properties of the protein itself, the improvement of the flame retardant properties of protein-based adhesives still faces great challenges. In a fire environment, the performance of protein-based adhesives is still poor. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a plant protein-based bamboo-wood adhesive, which improves the flame retardant performance.

[0004] According to a first aspect of the present invention, a plant protein-based bamboo-wood adhesive is provided. The raw materials for preparing the plant protein-based bamboo-wood adhesive include: cake protein isolate, a silane coupling agent and a composite modifier;

[0005] The raw materials for preparing the composite modifier include: pullulan modified with aldehyde groups and a compound modified with borate ester bonds;

[0006] The raw materials for preparing the compound modified with a boronate ester bond include ellagic acid and 4-hydroxymethylphenylboronic acid.

[0007] According to the first aspect of the present invention, there are at least the following beneficial effects:

[0008] Pullulan modified with aldehyde groups has a long molecular chain structure, which provides an important basis for the subsequent extension of the molecular chain and the formation of a double cross-linked network; ellagic acid has a symmetrical molecular structure, and the functional groups on both sides can react with 4-hydroxymethylphenylboronic acid to promote the extension of the polymer chain, thereby providing favorable conditions for the subsequent formation of a double cross-linked network. Specifically, 4-hydroxymethylphenylboronic acid has two active groups, a boric acid group and a hydroxyl group, wherein the hydroxyl group can participate in the aldol condensation reaction with the aldehyde group in the pullulan dialdehyde molecule to generate a covalent bond, further enhancing the cross-linking density of the material. Therefore, the system can achieve efficient cross-linking network construction through the synergistic effect of multi-step reactions, significantly improving the structural stability and performance of the material. Under the above conditions, 4-hydroxymethylphenylboronic acid can be fully and evenly distributed in the adhesive and the board, so that the flame retardant properties of the board are significantly improved.

[0009] According to some embodiments of the present invention, the pullulan modified with an aldehyde group comprises pullulan dialdehyde.

[0010] According to some embodiments of the present invention, the cake protein isolate includes at least one of tung oil cake, camellia oil cake, soybean cake and litsea cubeba cake.

[0011] According to some embodiments of the present invention, the silane coupling agent includes at least one of bis(3-aminopropyl)-terminated polydimethylsiloxane and aminoethylaminopropylpolydimethylsiloxane.

[0012] The above silane coupling agent has amino groups, which can react with aldehyde groups and form covalent condensation with organic long chains. In addition, the diphenol structure on ellagic acid can react with boric acid to form borate ester bonds, thereby forming an organic-inorganic hybrid three-crosslinked network structure. This can enhance the hydrophobicity, mechanical properties and hardness of the board on the one hand, and the flame retardant properties on the other hand.

[0013] According to a second aspect of the present invention, a method for preparing a plant protein-based bamboo-wood adhesive is provided, comprising: dispersing the composite modifier, the silane coupling agent and the cake protein isolate and then heating them for reaction.

[0014] According to some embodiments of the present invention, the ratio of the composite modifier, the silane coupling agent and the cake protein isolate is 10-20:5-10:15-30 in parts by weight.

[0015] According to some embodiments of the present invention, the temperature of the heating reaction is 50-80°C.

[0016] According to a second aspect of the present invention, a method for preparing a plant protein-based bamboo-wood adhesive is proposed, comprising: dispersing 10 to 20 parts of the composite modifier, 5 to 10 parts of the silane coupling agent, 15 to 30 parts of the cake protein isolate, 40 to 45 parts of water, and 2 to 3 parts of an initiator and then heating them for reaction.

[0017] According to some embodiments of the present invention, the method for preparing the composite modifier comprises the following steps: mixing the pullulan modified with an aldehyde group and the compound modified with a borate bond and heating them for reaction.

[0018] According to some embodiments of the present invention, the pullulan modified with an aldehyde group and the compound modified with a borate ester bond are mixed in a mass ratio of 1:1-2, and then heated at 70-80° C. for reaction.

[0019] According to some embodiments of the present invention, the method for preparing the compound modified with a boronate ester bond comprises: mixing the ellagic acid and the 4-hydroxymethylphenylboronic acid and then heating them for reaction.

[0020] According to some embodiments of the present invention, the method for preparing the compound modified with a boronate ester bond comprises: mixing 8 to 10 parts of the ellagic acid, 15 to 20 parts of the 4-hydroxymethylphenylboronic acid and water by weight, and heating the mixture at 75 to 80° C. for reaction.

[0021] According to some embodiments of the present invention, the method for preparing the pullulan modified with an aldehyde group comprises: dispersing pullulan and sodium periodate and then heating them to react to obtain pullulan dialdehyde.

[0022] According to a third aspect of the present invention, a thin particle board is provided, wherein the raw materials for preparing the artificial board include a plant protein-based bamboo-wood adhesive. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0024] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0025] Unless otherwise specified, "room temperature" in the present invention means 25°C±5°C.

[0026] Unless otherwise specified, "about" in the present invention means that the allowable error is within ±2%.

[0027] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0028] The first aspect of the present invention provides a plant protein-based bamboo-wood adhesive, wherein the raw materials for preparing the plant protein-based bamboo-wood adhesive include: cake protein isolate, a silane coupling agent and a composite modifier;

[0029] The raw materials for preparing the composite modifier include: pullulan modified with aldehyde groups and a compound modified with borate ester bonds;

[0030] The raw materials for preparing the compound modified with a boronate ester bond include ellagic acid and 4-hydroxymethylphenylboronic acid.

[0031] Pullulan modified with aldehyde groups has a long molecular chain structure, which provides an important basis for the subsequent extension of the molecular chain and the formation of a double cross-linked network; ellagic acid has a symmetrical molecular structure, and the functional groups on both sides can react with 4-hydroxymethylphenylboronic acid to promote the extension of the polymer chain, thereby providing favorable conditions for the subsequent formation of a double cross-linked network. Specifically, 4-hydroxymethylphenylboronic acid has two active groups, a boric acid group and a hydroxyl group, wherein the hydroxyl group can participate in the aldol condensation reaction with the aldehyde group in the pullulan dialdehyde molecule to generate a covalent bond, further enhancing the cross-linking density of the material. Therefore, the system can achieve efficient cross-linking network construction through the synergistic effect of multi-step reactions, significantly improving the structural stability and performance of the material. Under the above conditions, 4-hydroxymethylphenylboronic acid can be fully and evenly distributed in the adhesive and the board, so that the flame retardant properties of the board are significantly improved.

[0032] In combination with the first aspect, in some embodiments of the present invention, the cake protein isolate includes at least one of tung oil cake, camellia oil cake, soybean cake and litsea cubeba cake.

[0033] In combination with the first aspect, in some embodiments of the present invention, the silane coupling agent includes at least one of bis(3-aminopropyl)-terminated polydimethylsiloxane and aminoethylaminopropyl polydimethylsiloxane.

[0034] The above silane coupling agent has amino groups, which can react with aldehyde groups and form covalent condensation with organic long chains. In addition, the diphenol structure on ellagic acid can react with boric acid to form borate ester bonds, thereby forming an organic-inorganic hybrid three-crosslinked network structure. This can enhance the hydrophobicity, mechanical properties and hardness of the board on the one hand, and the flame retardant properties on the other hand.

[0035] In combination with the second aspect, in some embodiments of the present invention, a method for preparing a plant protein-based bamboo-wood adhesive is proposed, comprising: dispersing the composite modifier, the silane coupling agent and the cake protein isolate and then heating them for reaction.

[0036] In combination with the second aspect, in some embodiments of the present invention, the method for preparing the composite modifier comprises the following steps: mixing the pullulan modified with an aldehyde group and the compound modified with a borate bond and heating them for reaction.

[0037] In combination with the second aspect, in some embodiments of the present invention, the ratio of the composite modifier, the silane coupling agent and the cake protein isolate is 10-20:5-10:15-30 by weight.

[0038] In combination with the second aspect, in some embodiments of the present invention, the temperature of the heating reaction is 50-80°C.

[0039] In combination with the second aspect, in some embodiments of the present invention, the method for preparing the compound modified with a boronate ester bond comprises: mixing the ellagic acid and the 4-hydroxymethylphenylboronic acid and then heating them for reaction.

[0040] According to some embodiments of the present invention, the pullulan modified with an aldehyde group and the compound modified with a borate ester bond are mixed in a mass ratio of 1:1-2, and then heated at 70-80° C. for reaction.

[0041] In combination with the second aspect, in some embodiments of the present invention, the method for preparing the pullulan modified with an aldehyde group comprises: dispersing pullulan and sodium periodate and then heating them to react to obtain pullulan dialdehyde.

[0042] In combination with the second aspect, in some embodiments of the present invention, the method for preparing the compound modified with a boronate ester bond comprises: mixing the ellagic acid and the 4-hydroxymethylphenylboronic acid and then heating them for reaction.

[0043] In combination with the second aspect, in some embodiments of the present invention, the preparation method of the compound modified with a borate ester bond includes: mixing 8 to 10 parts of the ellagic acid, 15 to 20 parts of the 4-hydroxymethylphenylboronic acid and water by weight, and heating the mixture at 75 to 80°C for reaction.

[0044] In combination with the third aspect, in some embodiments of the present invention, a thin particle board is provided, and the raw materials for preparing the artificial board include plant protein-based bamboo-wood adhesive.

[0045] In the present invention, the system can realize efficient cross-linking network construction through the synergistic effect of multi-step reaction, significantly improve the structural stability and performance of the material, and 4-hydroxymethylphenylboronic acid can be fully and evenly distributed in the adhesive and the plate under the above system, so that the flame retardant performance of the plate is significantly improved. The pullulan polysaccharide modified with aldehyde groups has a longer molecular chain structure, which provides an important basis for the extension of subsequent molecular chains and the formation of double cross-linked networks; ellagic acid has a symmetrical molecular structure, and the functional groups on both sides of it can react with 4-hydroxymethylphenylboronic acid to promote the extension of polymer chains, thereby providing favorable conditions for the formation of subsequent double cross-linked networks. Specifically, 4-hydroxymethylphenylboronic acid has two active groups of boric acid group and hydroxyl group at the same time, wherein the hydroxyl group can participate in the aldol condensation reaction with the aldehyde group in the pullulan dialdehyde molecule to generate a covalent bond, further strengthening the cross-linking density of the material.

[0046] Example 1

[0047] This embodiment discloses a plant protein-based bamboo-wood adhesive and a preparation method thereof, and the specific steps are as follows:

[0048] By weight, 20 parts of a composite modifier, 10 parts of bis(3-aminopropyl)-terminated polydimethylsiloxane (CAS No.: 106214-84-0), 25 parts of meal protein isolate, 43 parts of water, and 2 parts of an initiator (CuI) were mixed in proportion, stirred continuously until uniform, and then reacted at 60° C. for 30 minutes to obtain a modified meal protein isolate-based adhesive;

[0049] The preparation method of the composite modifier is as follows:

[0050] A1. By weight, 10 parts of pullulan polysaccharide and 5 parts of sodium periodate were mixed with water in proportion, heated (80° C.) to react to obtain pullulan dialdehyde;

[0051] A2. 10 parts of ellagic acid and 20 parts of 4-hydroxymethylphenylboronic acid are mixed with water, and then heated at 75°C to react to generate a compound having a borate ester bond;

[0052] A3. Pullulan dialdehyde and a compound having a borate ester bond are mixed and heated at 50°C for reaction to obtain a composite modifier.

[0053] Example 2

[0054] This embodiment discloses a plant protein-based bamboo-wood adhesive and a preparation method thereof. The difference from Embodiment 1 is that the amount of the composite modifier added is 10 parts, and the rest is the same as Embodiment 1.

[0055] Example 3

[0056] This embodiment discloses a plant protein-based bamboo-wood adhesive and a preparation method thereof. The difference from Embodiment 1 is that aminoethylaminopropyl polydimethylsiloxane replaces bis(3-aminopropyl)-terminated polydimethylsiloxane, and the rest is the same as Embodiment 1.

[0057] Example 4

[0058] This embodiment discloses a plant protein-based bamboo-wood adhesive and a preparation method thereof. The difference from Embodiment 1 is that the amount of bis(3-aminopropyl)-terminated polydimethylsiloxane added is 5 parts, and the rest is the same as Embodiment 1.

[0059] Example 5

[0060] This embodiment discloses a plant protein-based bamboo-wood adhesive and a preparation method thereof. The difference from Embodiment 1 is that the amount of ellagic acid added is 8 parts, and the rest is the same as Embodiment 1.

[0061] Comparative Example 1

[0062] This comparative example discloses a method for preparing a water-resistant plant protein adhesive. The difference between this comparative example and Example 1 is that ellagic acid is replaced by catechol, and other conditions are the same.

[0063] Comparative Example 2

[0064] This comparative example discloses a method for preparing a water-resistant plant protein adhesive. The difference between this comparative example and Example 1 is that pullulan is replaced by dextran, and the other conditions are the same.

[0065] Comparative Example 3

[0066] This comparative example discloses a method for preparing a plant protein-based bamboo-wood adhesive. The difference between this comparative example and Example 1 is that 4-carboxyphenylboric acid is used to replace 4-hydroxymethylphenylboric acid in Example 1, and the other conditions are the same.

[0067] Comparative Example 4

[0068] This comparative example discloses a method for preparing a water-resistant plant protein adhesive. The difference between this comparative example and Example 1 is that γ-aminopropyltrimethoxysilane is used to replace the bis(3-aminopropyl)-terminated polydimethylsiloxane, and the other conditions are the same.

[0069] Test Example 1

[0070] This test example tests the performance of the thin particleboard obtained in the comparative example of the embodiment, and the test results are shown in Table 1. Thin particles refer to boards with a thickness of 2 to 8 mm, and the raw material length is 0.8 to 4 mm, the aspect ratio is 15 mm, and the thickness is 0.2 to 0.25 mm. Preparation of thin bamboo particleboard: Thin particles refer to boards with a thickness of 6 mm, and the raw material length is 0.8 to 4 mm, and the thickness is 0.2 to 0.25 mm. Using a thickness gauge with a thickness of 6 mm, a flat pressing method is used to prepare a board with a length, width and thickness of 600 mm × 600 mm × 6 mm for testing.

[0071] Table 1 Performance test

[0072]

[0073] In Comparative Example 1, catechol is used to replace ellagic acid. By comparing the structures, it can be found that both contain catechol structures, but the ellagic acid structure is more complex, with two catechol structures, and also has an ester structure, which is more prone to related reactions in terms of reactivity, and has more reactivity in structure. After replacing with catechol in Comparative Example 1, catechol and 4-hydroxymethylphenylboronic acid can only react in one step, and chain extension cannot occur. The generated compound does not have the conditions to participate in subsequent reactions, so the subsequent components are only simply blended, and the subsequent product adhesive cannot fully react during the curing process, and cannot react with the protein component to form a multi-crosslinked organic-inorganic hybrid network structure. Therefore, the mechanical properties of the board in Comparative Example 1 are poor, and the blank is directly scattered after the immersion test. Because the components are simply blended, after being blended with wood shavings in time, the flame retardant components of the adhesive are unevenly distributed in the board, resulting in a low limiting oxygen index value.

[0074] In comparative example 2, dextran is used to replace pullulan. By comparing the structures, it can be found that dextran refers to a homopolysaccharide composed of glucose as a monosaccharide, and the glucose units are connected by glycosidic bonds, with side chains and branched structures. However, pullulan is a linear polysaccharide formed by polymerizing maltotriose repeating units connected by α-1,4 glycosidic bonds through α-1,6 glycosidic bonds. The spatial structure is different from that of dextran, and the difference in reactivity is significant. Therefore, in the subsequent reaction, the hydroxyl groups on the dextran cannot be fully hydroformylated, and have obvious side chains and branched structures. In the subsequent reaction, the aldehyde group cannot be fully exposed to participate in the relevant reaction, resulting in insufficient reaction. The subsequent product adhesive cannot fully react during the curing process, and cannot react with the protein component to form a multi-crosslinked organic-inorganic hybrid network structure. Therefore, the mechanical properties of the board in comparative example 2 are poor, and the blank is directly scattered after the immersion test. Because the components are simply blended, after being blended with wood shavings in time, the flame retardant components of the adhesive are unevenly distributed in the board, resulting in a low limiting oxygen index value.

[0075] In Comparative Example 3, 4-carboxyphenylboric acid replaces 4-hydroxymethylphenylboric acid. By comparing the structures, it can be found that the two are similar in structure, and the difference is the difference between the hydroxyl group and the carboxyl group on the benzene ring. After replacing with 4-carboxyphenylboric acid in Comparative Example 3, it cannot participate in the relevant reaction, so the subsequent components are only simply blended, and the subsequent product adhesive cannot fully react during the curing process, and cannot react with the protein component to form a multi-crosslinked organic-inorganic hybrid network structure. Therefore, the mechanical properties of the board in Comparative Example 3 are poor, and the blank is directly scattered after the immersion test. Because the components are simply blended, after being blended with wood chips in time, the flame retardant component of the adhesive is unevenly distributed in the board, resulting in a low limiting oxygen index value.

[0076] In Comparative Example 4, γ-aminopropyltrimethoxysilane replaces bis(3-aminopropyl)-terminated polydimethylsiloxane. Both are silane coupling agents. Although they both contain amino groups, their structures are different. The molecular chain of γ-aminopropyltrimethoxysilane is relatively short and contains one amino group. It cannot be chain extended in the reaction, and its reactivity is relatively weak, which makes it impossible to participate in related reactions. The subsequent components are mainly simply blended. The subsequent product adhesive cannot fully react during the curing process, and cannot react with the protein component to form a multi-crosslinked organic-inorganic hybrid network structure. Therefore, the mechanical properties of the board in Comparative Example 4 are poor, and the blank is directly scattered after the immersion test. Because the components are simply blended, after being blended with wood chips in time, the flame retardant component of the adhesive is unevenly distributed in the board, resulting in a low limiting oxygen index value.

[0077] The embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A plant protein-based bamboo-wood adhesive, characterized in that: The raw materials for preparing the plant protein-based bamboo-wood adhesive include: cake protein isolate, silane coupling agent and composite modifier; The raw materials for preparing the composite modifier include: pullulan modified with aldehyde groups and a compound modified with borate ester bonds; The raw materials for preparing the compound modified with a boronate ester bond include ellagic acid and 4-hydroxymethylphenylboronic acid.

2. The plant protein-based bamboo-wood adhesive according to claim 1, characterized in that: The cake protein isolate comprises at least one of tung oil cake, camellia oil cake, soybean cake and litsea cubeba cake.

3. The plant protein-based bamboo-wood adhesive according to claim 1, characterized in that: The silane coupling agent includes at least one of bis(3-aminopropyl)-terminated polydimethylsiloxane and aminoethylaminopropyl polydimethylsiloxane.

4. A method for preparing the plant protein-based bamboo-wood adhesive as claimed in any one of claims 1 to 3, characterized in that: include: The composite modifier, the silane coupling agent and the cake protein isolate are dispersed and then heated for reaction.

5. The preparation method according to claim 4, characterized in that: In parts by weight, the composite modifier, the silane coupling agent and the cake protein isolate are in a ratio of 10-20:5-10:15-30.

6. The preparation method according to claim 4, characterized in that: The temperature of the heating reaction is 50-80°C.

7. The preparation method according to claim 4, characterized in that: The preparation method of the composite modifier comprises the following steps: mixing the pullulan modified with aldehyde group and the compound modified with borate bond in a mass ratio of 1:1-2, and heating at 70-80°C for reaction.

8. The preparation method according to claim 7, characterized in that: The preparation method of the compound modified with a boronate ester bond comprises: mixing 8 to 10 parts of ellagic acid, 15 to 20 parts of 4-hydroxymethylphenylboronic acid and water by weight, and heating at 75 to 80° C. for reaction.

9. The preparation method according to claim 7, characterized in that: The preparation method of the pullulan modified with aldehyde groups comprises: dispersing pullulan and sodium periodate and then heating them for reaction to obtain pullulan dialdehyde.

10. A thin particle board, characterized in that: The raw materials for preparing the thin particle board include the plant protein-based bamboo-wood adhesive described in any one of claims 1 to 3.

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