Preparation method and application of high-strength, mildew-proof and low-cost cottonseed meal protein adhesive

Abstract

The invention discloses a preparation method and application of a high-strength, mildew-proof and low-cost cottonseed meal protein adhesive. The preparation method comprises the following steps: compounding L-lysine and 4-carboxyphenylboronic acid through a coupling reaction to prepare lysine borate, adding the prepared lysine borate into the cottonseed meal protein adhesive, adding a proper amount of transglutaminase, and uniformly stirring to obtain the novel high-strength, mildew-proof and low-cost cottonseed meal protein adhesive based on the skin bionic strategy. The innovation points of the invention are as follows: by simulating a peptide bond between protein and polysaccharide in skin and forming a compact cross-linked layer through dehydration condensation reaction, using transglutaminase to construct a grain-lysine isopeptide bond, and introducing boric acid to form a covalent boron-oxygen-six-ring structure, a dual cross-linked network is constructed. The cottonseed meal protein adhesive has the advantages that the bonding strength, mildew resistance and other properties of the cottonseed meal protein adhesive can be remarkably improved only by using trace transglutaminase and boron oxygen six-ring as cross-linking agents, and the preparation cost of the adhesive is reduced.

Description

Technical Field

[0001] The present invention relates to the field of environment-friendly wood adhesives, and particularly to a preparation method of a high-strength, mildew-proof, and low-cost cottonseed meal protein adhesive based on a skin bionic strategy. Background Art

[0002] As of 2021, the annual output of wood-based panels in China has reached 337 million square meters, accounting for 37.06% of the global wood-based panel output. Wood-based panels are widely used in wood processing applications such as furniture manufacturing, interior decoration, and construction. As a key component in the manufacture of wood-based panels, adhesives have a significant impact on the performance of the panels and environmental friendliness. In the late 20th century, the wood adhesive market was dominated by petroleum-based adhesives (such as UF, PF, MF, etc.), which had advantages such as good strength, water resistance, and low price. However, such adhesives not only have a problem of relying on fossil resources but also release volatile organic pollutants (VOCs), posing a huge hidden danger to the natural environment and human health. With the increasingly serious problem of resource depletion, the development of green and environment-friendly biomass adhesives has become an industry trend.

[0003] As an environment-friendly and renewable biomass adhesive, plant protein adhesives have advantages such as renewable raw materials, reduced environmental pollution, and efficient resource utilization, and have gradually become the mainstream of the development of green adhesives. However, the intermolecular forces between plant protein molecular chains are weak, the cross-linking is insufficient, and the network structure is uneven and unstable, resulting in low bonding strength and poor water resistance. In addition, plant protein adhesives contain nutrients such as polysaccharides, which are prone to induce the growth of microorganisms, and the spread of mold spores also endangers human health, hindering the large-scale promotion of the industrial production of plant protein adhesives. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-strength, mildew-proof, and low-cost cottonseed meal protein adhesive based on a skin bionic strategy and its preparation method to overcome the problems raised in the above technical background. The adhesive has a high-density cross-linked network structure, which can improve the gluing performance and mildew-proof performance and reduce the production cost.

[0005] Technical Problems to be Solved

[0006] Aiming at the poor water resistance of ordinary plant protein adhesives in the prior art and the fact that the modification with chemical cross-linking agents will damage the environmental protection advantages of plant protein adhesives and affect their sustainable development in the wood industry. Therefore, the present invention aims to use transglutaminase as a bio-enzyme cross-linking agent for cottonseed meal protein adhesives, and construct a double cross-linked network structure with lysine-modified phenylboronic acid through γ-lysine isopeptide bonds and covalent boroxine ring structures to improve the water-resistant bonding performance and mildew-proof property without using chemical cross-linking agents.

[0007] Technical solution

[0008] In view of the deficiencies of the prior art, the present invention provides the following technical solution: Design an enzymatic crosslinking method, and construct a γ-Lysine isopeptide bond crosslinking network based on transglutaminase, which significantly enhances the interfacial adhesion and cohesion of cottonseed meal protein adhesives. Without using fossil crosslinkers at all, a cottonseed meal protein adhesive with high water-resistant bonding strength, mildew-proof and flame-retardant properties is developed. The high-strength, mildew-proof and low-cost cottonseed meal protein adhesive described in the present invention is made of the following components: cottonseed meal, water, transglutaminase, boric acid, catalyst.

[0009] A high-strength, mildew-proof and low-cost cottonseed meal protein adhesive based on a skin biomimetic strategy, and the weight composition of each component is: 10-20 parts of cottonseed meal protein powder, 70-85 parts of water, 0-0.4 parts of transglutaminase, 0-0.6 parts of lysine borate.

[0010] The protein content in the cottonseed meal protein powder exceeds 95%.

[0011] The transglutaminase is 100U / g.

[0012] The lysine borate is synthesized by the coupling reaction of 4-carboxyphenylboronic acid with a purity of 97% and L-lysine with a purity of 98%: Dissolve 1.66 g of 4-carboxyphenylboronic acid in 30 ml of 0.1 mol / L 2-morpholinoethanesulfonic acid solution, add 2.97 g of N-ethylcarbodiimide hydrochloride and 1.15 g of N-hydroxysuccinimide. Subsequently, stir at a temperature of 40 °C for 45 minutes. Use an appropriate amount of sodium dihydrogen phosphate solution to adjust the pH value of the reactant system to 7, then perform ultrasonic treatment for 5 minutes, add 2.9 g of L-lysine, and stir for 5 hours.

[0013] A high-strength, mildew-proof and low-cost cottonseed meal protein adhesive based on a skin biomimetic strategy and its preparation method, including the following steps:

[0014] (1) Mix the cottonseed meal protein powder and water, stir for 15 minutes until evenly mixed, and perform denaturation treatment for 20 minutes under an ultrasonic cell disruptor to obtain a deformed cottonseed meal protein adhesive.

[0015] (2) Add lysine borate to the denatured cottonseed meal protein adhesive, then add transglutaminase, and stir at 55 °C for 10 minutes. Quickly cool the mixture to room temperature to obtain a high-strength, mildew-proof and low-cost cottonseed meal protein adhesive based on a skin biomimetic strategy.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] 1. By combining the γ - lysine isopeptide bond and the covalent boroxine ring structure, the invention promotes the formation of a highly dense cross - linked network structure in the cottonseed meal protein adhesive, which can simultaneously improve the water - resistant gluing strength and the mildew - proof performance of the cottonseed meal protein adhesive.

[0018] 2. On this basis, the invention effectively improves the flame resistance of the adhesive after curing and enhances the flame retardancy of the artificial board.

[0019] 3. Compared with most of the existing cottonseed meal protein adhesives, the cottonseed meal protein adhesive developed by the invention only uses a small amount of transglutaminase and boroxine ring as cross - linkers, significantly reducing the usage amount of chemical cross - linkers and having great environmental and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below in conjunction with the drawings and embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them:

[0021] Figure 1 It is a schematic diagram of the wet shear strength of the samples of the embodiments and comparative examples of a high - strength, mildew - proof and low - cost cottonseed meal protein adhesive of the present invention.

[0022] Figure 2 It is a schematic diagram of the mildew - proof performance of the samples of the embodiments and comparative examples of a high - strength, mildew - proof and low - cost cottonseed meal protein adhesive of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The following specific examples illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0024] Example 1:

[0025] (1) Mix 2 parts of 4 - carboxyphenylboronic acid and 3 parts of L - lysine and stir for 5 hours to obtain lysine borate ester.

[0026] (2) Disperse 15 parts of cottonseed meal protein powder in 85 parts of water, stir at room temperature for 15 minutes until evenly mixed, and perform denaturation treatment for 20 minutes under an ultrasonic cell disruptor to obtain the denatured cottonseed meal protein adhesive.

[0027] (2) Add 0.2 part of the lysine borate ester prepared in step (1) to the dispersion in step (3) and mix evenly, then add 0.4 part of transglutaminase. After mixing evenly, a novel cottonseed meal protein adhesive based on skin bionic strategy is obtained.

[0028] Example 2:

[0029] (1) Mix 2 parts of 4-carboxyphenylboronic acid and 3 parts of L-lysine and stir for 5 hours to obtain lysine borate ester.

[0030] (2) Disperse 15 parts of cottonseed meal protein powder in 85 parts of water, stir at room temperature for 15 minutes until evenly mixed, and perform denaturation treatment for 20 minutes under an ultrasonic cell disruptor to obtain the deformed cottonseed meal protein adhesive.

[0031] (3) Add 0.4 part of the lysine borate ester prepared in step (1) to the dispersion in step (3) and mix evenly, then add 0.4 part of transglutaminase, and mix evenly to obtain a novel cottonseed meal protein adhesive based on skin bionic strategy.

[0032] Example 3:

[0033] (1) Mix 2 parts of 4-carboxyphenylboronic acid and 3 parts of L-lysine and stir for 5 hours to obtain lysine borate ester.

[0034] (2) Disperse 15 parts of cottonseed meal protein powder in 85 parts of water, stir at room temperature for 15 minutes until evenly mixed, and perform denaturation treatment for 20 minutes under an ultrasonic cell disruptor to obtain the deformed cottonseed meal protein adhesive.

[0035] (3) Add 0.6 part of the lysine borate ester prepared in step (1) to the cottonseed meal protein adhesive in step (3) and mix evenly, then add 0.4 part of transglutaminase, and mix evenly to obtain a novel cottonseed meal protein adhesive based on skin bionic strategy.

[0036] Comparative Example 1:

[0037] (1) Mix 2 parts of 4-carboxyphenylboronic acid and 3 parts of L-lysine and stir for 5 hours to obtain lysine borate ester.

[0038] (2) Disperse 15 parts of cottonseed meal protein powder in 85 parts of water, stir at room temperature for 15 minutes until evenly mixed, and perform denaturation treatment for 20 minutes under an ultrasonic cell disruptor to obtain the deformed cottonseed meal protein adhesive.

[0039] (3) Add 0.6 part of the lysine borate ester prepared in step (1) to the cottonseed meal protein adhesive in step (2), and mix evenly to obtain a lysine borate ester-modified cottonseed meal protein adhesive.

[0040] Comparative Example 2:

[0041] (1) Disperse 15 parts of cottonseed meal protein powder in 85 parts of water, stir at room temperature for 15 minutes until evenly mixed, and perform denaturation treatment for 20 minutes under an ultrasonic cell disruptor to obtain the denatured cottonseed meal protein adhesive.

[0042] (2) Add 0.4 part of transglutaminase to the cottonseed meal protein adhesive in step (1), and mix evenly to obtain the transglutaminase-modified cottonseed meal protein adhesive.

[0043] Comparative Example 3:

[0044] (1) Disperse 30 parts of cottonseed meal protein powder in 40 parts of water, stir at room temperature for 15 minutes until evenly mixed, and perform denaturation treatment for 20 minutes under an ultrasonic cell disruptor to obtain the denatured cottonseed meal protein adhesive.

[0045] (2) Add 30 parts of polyamide polyamine-epichlorohydrin with a solid content of 12.5% to the cottonseed meal protein adhesive in step (1), and mix evenly to obtain the polyamide polyamine-epichlorohydrin-modified cottonseed meal protein adhesive.

[0046] Comparative Example 4:

[0047] (1) Disperse 18 parts of cottonseed meal protein powder in 70 parts of water, stir at room temperature for 15 minutes until evenly mixed, and perform denaturation treatment for 20 minutes under an ultrasonic cell disruptor to obtain the denatured cottonseed meal protein adhesive.

[0048] (2) Add 12 parts of tris(2,3-epoxypropyl)amine to the cottonseed meal protein adhesive in step (1), and mix evenly to obtain the tris(2,3-epoxypropyl)amine-modified cottonseed meal protein adhesive.

[0049] Comparative Example 5:

[0050] Disperse 15 parts of cottonseed meal protein powder in 85 parts of water, stir at room temperature for 15 minutes until evenly mixed, and perform denaturation treatment for 20 minutes under an ultrasonic cell disruptor to obtain the denatured cottonseed meal protein adhesive.

[0051] Detect the bonding strength performance of the produced plywood products according to the detection method of GB / T 17657-1999 "Test Methods for Physical and Chemical Properties of Wood-Based Panels and Decorated Wood-Based Panels", and the detection results are as Figure 1 and Figure 2 shown.

[0052] In view of the problem that plant protein adhesives rely on fossil crosslinking agents, the present invention designs enzymatic crosslinking, constructs a γ-lysine isopeptide bond crosslinking network based on glutamine transaminase, realizes a significant enhancement of the interfacial adhesion and cohesion of cottonseed meal protein adhesives, and develops a cottonseed meal protein adhesive with high water-resistant bonding strength, mildew-proof and flame-retardant properties without using fossil crosslinking agents at all. See the attached Figure 1, it can be seen that when the ratio of lysine borate ester and transglutaminase is fixed, the wet bonding strength of the novel cottonseed meal protein adhesive prepared based on the skin bionic strategy is improved. The water-resistant bonding strength of Example 3 is increased to 1.55 MPa, which is 72% higher than that of the cottonseed meal protein adhesive of Comparative Example 1. Moreover, the total addition amount of transglutaminase and lysine-boroxine polymer is only 1.0%, and the wet shear strength of the plywood prepared is higher than that of the cottonseed meal protein adhesives with other high chemical cross-linking agent addition amounts in Comparative Example 3.

[0053] Refer to the appendix Figure 2 , it can be seen that the mildew-proof storage period of Example 3 is extended to 15 days, and it has antibacterial effects on Escherichia coli and Staphylococcus aureus, which can meet the usage requirements of the plywood industry for adhesives. In contrast, the mildew-proof storage period of Comparative Example 1 is extended to 3 days, and that of Comparative Example 2 is extended to 2 days.

[0054] Therefore, introducing transglutaminase into the plant protein adhesive system of the present invention can provide a novel and promising way to solve the problems of insufficient water-resistant bonding strength and dependence on chemical cross-linking agents in the industrial production of plant protein adhesives.

[0055] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. However, they are not used to limit the present invention. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

Claims

1. A method for preparing a high-strength, mildew-proof, low-cost cottonseed meal protein adhesive and its application, characterized in that: It is composed of the following raw materials: cottonseed meal, water, transglutaminase, boric acid and catalyst.

2. A high-strength, mildew-proof, low-cost cottonseed meal protein adhesive according to claim 1, characterized in that: By imitating the dense cross-linked layer formed by the peptide bond and dehydration condensation reaction between proteins and polysaccharides in the skin, transglutaminase was used to construct the glutamic-lysine isopeptide bond, and boric acid was introduced to form a covalent boron oxide six ring structure to construct a double cross-linked network inside the soy protein adhesive. The formation of the glutamic-lysine isopeptide bond makes the connection between soy protein molecules tighter, improving the mechanical strength of the adhesive. At the same time, the introduction of the boron oxide six ring further enhances the interaction between molecules and forms a more stable network structure. This double cross-linked network enables the adhesive to disperse and resist stress more effectively when subjected to external forces, thereby improving its wet bonding strength and durability.

3. A high-strength, mildew-proof, low-cost cottonseed meal protein adhesive according to claim 2, characterized in that: The preparation method of lysine-boryl hexacyclic polymer comprises the following steps: S1. Weigh 1.66 g of 4-carboxyphenylboronic acid, dissolve it in 0.1 mol / L 2-morpholineethanesulfonic acid solution (30 mL), add 2.97 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 1.15 g of N-hydroxysuccinimide, heat the system to 40 ° C and stir for 45 min to activate the carboxyl group. S2. Use 0.1 mol / L Na2HPO4 solution to adjust the pH of the mixed solution to 7.0, then ultrasonically treat the mixed solution for 5 minutes, add 2.9 g of L-lysine, and stir at room temperature for 5 hours. S3. Centrifuge the mixed solution at 8000 rpm for 5 min, wash the precipitate three times with deionized water, and finally dry it in a vacuum drying oven at 60° C. to obtain a lysine-boryl hexacyclic polymer.

4. A high-strength, mildew-proof, low-cost cottonseed meal protein adhesive according to claim 3, characterized in that: Boric acid molecules are connected to soybean protein chains under the catalysis of transglutaminase, which can destroy the cell wall and cell membrane structure of microorganisms, thereby inhibiting their growth and reproduction. This antibacterial and antifungal effect enables the adhesive to maintain stability and safety for a long time during use, significantly improving its antifungal and antibacterial properties.

5. A high-strength, mildew-proof, low-cost cottonseed meal protein adhesive according to claim 3, characterized in that: The formation of the six-ring structure of boron and oxygen enables the adhesive to form a dense carbonized layer during the combustion process, effectively isolating oxygen and heat transfer, thereby slowing down the combustion speed and reducing the heat release rate. This improvement in flame retardancy allows the adhesive to maintain good flame retardancy under extreme conditions such as fire.

6. Use of the high-strength, mildew-proof, low-cost cottonseed meal protein adhesive as claimed in claim 5 in wood processing and artificial boards.

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