High-performance formaldehyde-free tea seed meal wood adhesive containing microgel structure and preparation method of high-performance formaldehyde-free tea seed meal wood adhesive

Abstract

The invention provides a high-performance formaldehyde-free tea seed meal wood adhesive containing a microgel structure and a preparation method of the high-performance formaldehyde-free tea seed meal wood adhesive. The method comprises the following steps: crushing tea seeds into powder by using mechanical force, removing grease of tea seed meal by using n-hexane at room temperature, further crushing to be more than 200 meshes, reducing the particle size, and exposing active functional groups (such as amino, carboxyl and hydroxyl); the tea seed meal, the modifier and the natural polyphenol are subjected to a non-covalent self-assembly aggregation behavior under the action of microwave temperature control to form microgel, so that the viscosity of the system is reduced; during subsequent use, in the hot pressing process, the microgel is crushed, the modifier reacts with active groups in the tea seed meal to form a rigid covalent network, the natural polyphenol containing catechol groups, the modifier and the tea seed meal form a flexible non-covalent network, the tea seed meal adhesive is endowed with strong water resistance through a rigid-flexible cross-linked network, and the application prospect is good.

Description

Technical Field

[0001] The invention belongs to the field of adhesive preparation, and particularly relates to a high-performance formaldehyde-free tea seed meal wood adhesive containing a microgel structure and a preparation method thereof. Background Art

[0002] The main raw materials of formaldehyde adhesives (formaldehyde, phenol) come from petroleum and have poor renewability. Toxic substances (such as formaldehyde) are continuously released during production and use, which are harmful to human health. The products are not easy to degrade and are easy to pollute the environment. Therefore, the preparation of biomass wood adhesives with renewable biomass raw materials (such as plant protein, starch, lignin, etc.) has attracted the attention of researchers and achieved good results. However, there is still a problem of poor water resistance, especially the boiling water resistance bonding strength is still far behind that of formaldehyde adhesives. In addition, mildew, high raw material costs and the food properties of some biomass raw materials also limit the possibility of large-scale application. For this reason, it is urgent to develop a low-cost, high-performance biomass-based adhesive with anti-mildew function.

[0003] As an agricultural processing residue, tea seed meal has the advantage of lower cost compared with other biomass raw materials (such as starch). In addition, tea seed meal contains biological toxic components and is not suitable as food. It has great advantages as an adhesive raw material. Wang et al. mixed oxidatively activated tea seed meal with soybean meal in different proportions, added epoxy crosslinking agent and polyethyleneimine (PEI) for co-crosslinking, and the wet bonding strength reached 1.82 MPa, which met the GB / T 9846-2015 indoor Class II board standard (Wang H, Chen G, Zhang S, et al. Camellia meal-based formaldehyde-free adhesive with self-crosslinking, and anti-mildew performance [J]. Ind Crops Prod, 2022, 176:114280.). However, the preparation process of the adhesive is complicated, and the proportion of soybean meal added is high, which increases the cost of the adhesive and limits the industrial application of the adhesive. Summary of the invention

[0004] The purpose of the present invention is to provide a high-performance formaldehyde-free tea seed meal wood adhesive containing a microgel structure and a preparation method thereof.

[0005] To achieve the above object, the present invention adopts the following technical solution: A method for preparing a high-performance formaldehyde-free tea seed meal wood adhesive containing a microgel structure comprises the following steps: (1) Processing of tea seed meal raw material: mechanically crush the tea seed raw material to obtain crushed material larger than 20 mesh, extract with 1:1 weight ratio of n-hexane at room temperature to remove oil and obtain tea seed meal raw material; mechanically crush the tea seed meal raw material into powder larger than 200 mesh for later use; (2) At room temperature, mix tea seed meal with water and stir at 120 rpm for 10 min. Then add the modifier and continue stirring for 10 min. Then add natural polyphenols and continue stirring at 300 rpm for 10 min. Control the temperature at 35-50 °C using a microwave heating device and let it stand for 10-30 min to prepare the wood adhesive.

[0006] Preferably, the tea seed meal raw material includes: low temperature deoiled tea tree seed meal and oil tea seed meal.

[0007] Preferably, the modifier includes: cationic polyacrylamide, JH1201 resin, kymene series resins or a mixture of several thereof.

[0008] Preferably, the natural polyphenols include: tea polyphenols, tannic acid, lignin, or a mixture of several thereof.

[0009] Preferably, the water is boiler steam condensate.

[0010] Preferably, the n-hexane extraction is performed twice.

[0011] Preferably, the mass ratio of tea seed meal to water is 25-35:30-55.

[0012] Preferably, the mass ratio of tea seed meal to modifier is 25-35:10-20.

[0013] Preferably, the mass ratio of tea seed meal to natural polyphenols is 25-35:10-15.

[0014] Preferably, the method described above produces a high-performance formaldehyde-free tea seed meal wood adhesive containing a microgel structure.

[0015] Principle: Tea seeds are crushed into powder by mechanical force. At room temperature, n-hexane is used to remove the oil from the tea seed powder, and then further crushed to more than 200 meshes to reduce its particle size and expose active functional groups (such as amino, carboxyl, and hydroxyl). Tea seed meal, modifiers, and natural polyphenols undergo non-covalent self-assembly aggregation under microwave temperature control to form microgels, reducing the viscosity of the system. In subsequent use, during the hot pressing process, the microgels are broken, the modifiers react with the active groups in the tea seed meal to form a rigid covalent network, and the natural polyphenols containing catechol groups form a flexible non-covalent network with the modifiers and tea seed meal. The rigid and flexible cross-linked network gives the tea seed meal adhesive strong water resistance.

[0016] Compared with the prior art, the present invention has the following significant advantages: The present invention uses mechanical force to crush the low-temperature defatted tea seed meal, reduce the particle size, increase the surface area, and increase the reactive sites; combined with microwave temperature control treatment, the adhesive components are self-assembled to form microgels; then, during the hot pressing process, the adhesive is cured and cross-linked, and combined with the antibacterial and flame retardant effects of natural polyphenols, the tea seed meal adhesive is endowed with high mechanical strength, high environmental stability and multifunctionality (heat resistance, mildew resistance, and flame retardancy). The present invention uses agricultural processing waste as raw materials, which increases the added value of the raw materials; the adhesive is prepared at room temperature, with low energy consumption; the microgel structure of the adhesive has high cohesive strength, good bonding performance, and excellent water resistance; and has a wide range of market application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a microscopic image of the adhesive prepared in Example 1 of the present invention; Figure 2 This is a microscopic image of the adhesive solution prepared in the control group of the present invention. DETAILED DESCRIPTION

[0018] In order to make the above features and advantages of the present invention more clearly understood, the following embodiments are given for detailed description. The methods of the present invention are all conventional methods in the art unless otherwise specified.

[0019] Example 1 Tea seed meal raw materials: low temperature de-oiled tea seed meal.

[0020] Modifier: Kymene series resin.

[0021] Natural polyphenols: tea polyphenols.

[0022] Water: Boiler steam condensate.

[0023] A method for preparing a high-performance formaldehyde-free tea seed meal wood adhesive containing a microgel structure comprises the following steps: (1) Processing of tea seed meal raw material: The tea seed raw material is mechanically crushed to obtain crushed material larger than 20 mesh, and then extracted twice with 1:1 weight ratio of n-hexane at room temperature to remove oil and obtain tea seed meal raw material; the tea seed meal raw material is further mechanically crushed into powder larger than 200 mesh and set aside.

[0024] (2) At room temperature, 30 parts by weight of camellia oleifera meal was mixed with 40 parts by weight of water, and the mixture was stirred at 120 rpm for 10 min. Then, 15 parts by weight of a modifier was added, and the mixture was stirred for 10 min. Then, 13 parts by weight of natural polyphenols was added, and the mixture was stirred at 300 rpm for 10 min. The mixture was heated at 40°C using a microwave heating device, and allowed to stand for 20 min to prepare a wood adhesive.

[0025] Example 2 Tea seed meal raw materials: low temperature de-oiled tea tree seed meal.

[0026] Modifier: cationic polyacrylamide.

[0027] Natural polyphenols: tannic acid.

[0028] Water: Boiler steam condensate.

[0029] A method for preparing a high-performance formaldehyde-free tea seed meal wood adhesive containing a microgel structure comprises the following steps: (1) Processing of tea seed meal raw material: The tea seed raw material is mechanically crushed to obtain crushed material larger than 20 mesh, and then extracted twice with 1:1 weight ratio of n-hexane at room temperature to remove oil and obtain tea seed meal raw material; the tea seed meal raw material is further mechanically crushed into powder larger than 200 mesh and set aside.

[0030] (2) At room temperature, 25 parts of tea seed meal were mixed with 30 parts of water and stirred at 120 rpm for 10 min. Then 10 parts of modifier were added and stirred for 10 min. Then 10 parts of natural polyphenols were added and stirred at 300 rpm for 10 min. The temperature was controlled at 35 °C by microwave heating equipment and allowed to stand for 10 min to prepare wood adhesive.

[0031] Example 3 Tea seed meal raw materials: low temperature de-oiled tea seed meal.

[0032] Modifier: JH1201 resin.

[0033] Natural polyphenols: lignin.

[0034] Water: Boiler steam condensate.

[0035] A method for preparing a high-performance formaldehyde-free tea seed meal wood adhesive containing a microgel structure comprises the following steps: (1) Processing of tea seed meal raw material: The tea seed raw material is mechanically crushed to obtain crushed material larger than 20 mesh, and then extracted twice with 1:1 weight ratio of n-hexane at room temperature to remove oil and obtain tea seed meal raw material; the tea seed meal raw material is further mechanically crushed into powder larger than 200 mesh and set aside.

[0036] (2) At room temperature, 35 parts of camellia seed meal were mixed with 55 parts of water and stirred at 120 rpm for 10 min. Then 20 parts of a modifier were added and stirred for 10 min. Then 15 parts of natural polyphenols were added and stirred at 300 rpm for 10 min. The temperature was controlled at 50 °C by a microwave heating device and allowed to stand for 30 min to prepare a wood adhesive.

[0037] Performance: This adhesive can be used to produce particleboard, fiberboard, plywood and other artificial boards. For example, when used to make plywood, the double-sided glue application amount is 400-450 g / m 2 , which can be achieved by manual gluing or roller gluing; at room temperature, with a surface pressure of 5MPa, pre-pressing for 0.5 hours, and then hot pressing at 1.0MPa, 130℃, 0.5min / mm, the bonding strength can meet the requirements of Class II plywood in GB / T9846-2015. The prepared artificial board has no free formaldehyde release, has antibacterial and mildew-proof, and flame-retardant effects, can be widely used in furniture or decoration industry, and has broad application prospects.

[0038] Note: The preparation of the common adhesive in the control group was the same as that in Example 1 except that the modifier and natural polyphenol were not added.

[0039] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing a high-performance formaldehyde-free tea seed meal wood adhesive containing a microgel structure, characterized in that: The following steps are involved: (1) Processing of tea seed meal raw material: mechanically crush the tea seed raw material to obtain crushed material larger than 20 mesh, extract with 1:1 weight ratio of n-hexane at room temperature to remove oil and obtain tea seed meal raw material; mechanically crush the tea seed meal raw material into powder larger than 200 mesh for later use; (2) At room temperature, mix tea seed meal with water and stir at 120 rpm for 10 min. Then add the modifier and continue stirring for 10 min. Then add natural polyphenols and continue stirring at 300 rpm for 10 min. Control the temperature at 35-50°C using a microwave heating device and let it stand for 10-30 min to prepare the wood adhesive.

2. The method according to claim 1, characterized in that The raw materials of tea seed meal include: low temperature de-oiled tea tree seed meal and oil tea seed meal.

3. The method according to claim 1, characterized in that The modifier includes: cationic polyacrylamide, JH1201 resin, kymene series resin or a mixture of several of them.

4. The method according to claim 1, characterized in that: Natural polyphenols include: tea polyphenols, tannic acid, lignin or a mixture of several of them.

5. The method according to claim 1, characterized in that The water is boiler steam condensate.

6. The method according to claim 1, characterized in that The number of n-hexane extractions was 2 times.

7. The method according to claim 1, characterized in that The mass ratio of tea seed meal to water is 25-35:30-55.

8. The method according to claim 1, characterized in that The mass ratio of tea seed meal to modifier is 25-35:10-20.

9. The method according to claim 1, characterized in that: The mass ratio of tea seed meal to natural polyphenols is 25-35:10-15.

10. A high-performance formaldehyde-free tea seed meal wood adhesive containing a microgel structure prepared according to the method of any one of claims 1 to 9.

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