Preparation method and application of microgel reinforced and toughened formaldehyde-free wood adhesive

Abstract

The invention discloses a preparation method and application of a microgel reinforced and toughened formaldehyde-free wood adhesive, the microgel reinforced and toughened formaldehyde-free wood adhesive mainly comprises 70-105 parts of light-burned heavy magnesium oxide, 60-70 parts of magnesium chloride hexahydrate, 35-45 parts of water, 10-15 parts of microgel hybrid, 10-15 parts of hybrid fiber and 10-15 parts of filler, and the microgel reinforced and toughened formaldehyde-free wood adhesive is prepared from 70-105 parts of light-burned heavy magnesium oxide, 60-70 parts of magnesium chloride hexahydrate and 35-45 parts of water. The addition amount of the microgel hybrid is 1.6-2.0% of the total mass of the light-burned heavy magnesium oxide, the magnesium chloride hexahydrate and the water, the addition amount of the hybrid fiber is 2% of the total mass of the light-burned heavy magnesium oxide, the magnesium chloride hexahydrate, the water and the filler, and the addition amount of the filler is 25-30% of the mass of the light-burned heavy magnesium oxide. The magnesium oxychloride cement adhesive solves the problems of high brittleness and poor impact resistance of the magnesium oxychloride cement adhesive in the prior art, the toughness of the adhesive is improved, and the technical breakthrough of impact resistance of the magnesium oxychloride cement adhesive artificial board is realized. In addition, the problems that the magnesium oxychloride cement is poor in water resistance and a weak interface layer exists at a cementing interface can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic cementitious materials, and particularly to a preparation method and application of a microgel-reinforced and toughened formaldehyde-free wood adhesive. Background Art

[0002] Under the background of the country's "dual carbon" goal, new requirements have been put forward for the wood-based panel manufacturing industry, and it is necessary to promote the research and development and popularization of green and low-carbon building materials. However, currently, the adhesives used in wood-based panels are mainly "three-aldehyde types". Aldehyde resin adhesives will release formaldehyde during production and use, causing environmental pollution and harming human health. Moreover, raw materials such as phenol are derived from non-renewable resources. In recent years, biomass resources such as starch, tannin, soy protein, lignin, and chitosan have been developed to prepare various formaldehyde-free adhesives, but they generally have problems such as poor water resistance, easy mildew, and poor mechanical properties of the products in application. Therefore, developing inorganic adhesives for use in wood to fundamentally solve the problem of formaldehyde pollution in the living environment has become a major scientific and technological reform direction for the green and high-quality development of the wood-based panel industry.

[0003] Magnesium oxychloride cement is a ternary cementitious system of MgO-MgCl2-H2O prepared from light-burned magnesia, magnesium chloride, and water, and has properties such as fire and heat resistance, carbon sequestration characteristics, short setting time, air hardening at room temperature, and excellent strength. Compared with other cement materials, magnesium oxychloride cement is more suitable for bonding wood materials. Magnesium oxychloride cement is an air-hardening material, and its curing process does not require wet curing. It can be cured at normal temperature and pressure, has high strength, low alkalinity, and does not corrode wood. In addition, magnesium chloride and the like are derived from waste, and its large-scale use can reduce the environmental burden. Magnesium oxychloride cement can solve the problems of formaldehyde release and fire hazards in wood-based panels, but it needs to overcome the problems of poor bonding strength and unstable performance caused by the weak interface layer between wood / magnesium oxychloride cement. Summary of the Invention

[0004] Aiming at the existing research, the purpose of the present invention is to provide an inorganic adhesive, which can effectively solve the inherent brittleness problem of magnesium oxychloride cement and enhance the toughness of the product. In addition, it can also solve the problems of poor water resistance of magnesium oxychloride cement and the existence of a weak interface layer at the bonding interface.

[0005] A microgel-reinforced and toughened formaldehyde-free wood adhesive, which comprises:

[0006] Light-burned heavy magnesia, magnesium chloride hexahydrate, water, microgel hybrid, hybrid fiber, filler.

[0007] Among them, 70 - 105 parts of light-burned heavy magnesium oxide, 60 - 70 parts of magnesium chloride hexahydrate, and 35 - 45 parts of water are used. The addition amount of the microgel hybrid is 1.6 - 2.0% of the total mass of light-burned heavy magnesium oxide, magnesium chloride hexahydrate, and water. The addition amount of the hybrid fiber is 2% of the total mass of light-burned heavy magnesium oxide, magnesium chloride hexahydrate, water, and filler. The addition amount of the filler is 25 - 30% of the mass replacing light-burned heavy magnesium oxide.

[0008] As a preferred embodiment of the preparation method of the microgel-reinforced and toughened formaldehyde-free wood adhesive of the present invention, the calcination temperature of the light-burned heavy magnesium oxide needs to be <1000°C. Further preferably, MgO with a calcination temperature in the range of 800 - 900°C is used. The activity of the light-burned magnesium oxide is 60 - 70%, and the magnesium oxide content is 80 - 90%.

[0009] 1. As a preferred embodiment of the preparation method of the microgel-reinforced and toughened formaldehyde-free wood adhesive of the present invention, among them, the hybrid fiber is a mixed combination of polyethylene fiber and basalt fiber, where the polyethylene fiber is 62.5% and the basalt fiber is 37.5%.

[0010] As a preferred embodiment of the preparation method of the microgel-reinforced and toughened formaldehyde-free wood adhesive of the present invention, among them, the filler is any one or more of mine tailing powder, slag, silica fume, fly ash, waste silicon powder, talc powder, diatomaceous earth, etc.

[0011] As a preferred embodiment of the preparation method of the microgel-reinforced and toughened formaldehyde-free wood adhesive of the present invention, among them, the particle size of the filler is ≥120 mesh.

[0012] A preparation method of a microgel-reinforced and toughened formaldehyde-free wood adhesive, the specific steps are as follows:

[0013] S1. Weigh magnesium chloride hexahydrate and completely dissolve it in water to form a uniform MgCl2 aqueous solution;

[0014] S2. Weigh light-burned heavy magnesium oxide and filler and mix them evenly, then add them to the MgCl2 aqueous solution and stir to form a uniform magnesium oxychloride cement slurry;

[0015] S3. Weigh the hybrid fiber and add it to the magnesium oxychloride cement slurry obtained in step S2, and stir at a speed of 10000 rpm for 5 min;

[0016] S4. Uniformly disperse the microgel hybrid into the magnesium oxychloride cement slurry obtained in step S3, and stir evenly to obtain the microgel-reinforced and toughened formaldehyde-free wood adhesive.

[0017] As a preferred embodiment of the preparation method of the microgel-reinforced and toughened formaldehyde-free wood adhesive of the present invention, the specific preparation steps of the microgel hybrid are as follows:

[0018] Dissolve a certain amount of quaternized chitosan, acrylic acid and citric acid in deionized water one by one, stir well to form a transparent mixed solution;

[0019] Add a certain amount of acrylamide and stir evenly;

[0020] Add the crosslinking agent N,N′-methylenebisacrylamide and stir magnetically at room temperature for 30 min;

[0021] Finally, add an appropriate amount of initiator ammonium persulfate and biomass acid in sequence, and stir well for a period of time to obtain the microgel hybrid.

[0022] As a preferred embodiment of the preparation method of the microgel-reinforced and toughened formaldehyde-free wood adhesive of the present invention, the biomass acid is any one or more of gallic acid, caffeic acid, chlorogenic acid, tannic acid and protocatechuic acid.

[0023] As a preferred embodiment of the preparation method of the microgel-reinforced and toughened formaldehyde-free wood adhesive of the present invention, the mixing is carried out under the condition of room temperature (25±2 °C).

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The microgel hybrid in the present invention can form a randomly distributed crosslinked network in the cement matrix, avoiding the aggregation of large and discrete polymer phases that weaken the mechanical properties of the whole structure. The gel network is tightly combined with the crystal to form a dense matrix, which can effectively improve the water resistance of magnesium oxychloride cement and endow it with toughness;

[0026] 2. There is a good bonding ability between the fiber and the magnesium oxychloride cement matrix, which can further enhance the toughness of magnesium oxychloride cement. The addition of fillers can not only obtain mechanical property enhancement, but also reduce the cost of magnesium oxychloride cement to a certain extent;

[0027] 3. The preparation process of the microgel-reinforced and toughened formaldehyde-free wood adhesive provided by the present invention is simple and the production cost is low. No "three wastes" are generated during the production process, which conforms to the concept of sustainable development. The microgel-reinforced and toughened magnesium oxychloride cement can be widely used in the fields of construction, fire and heat resistance, decoration, packaging, etc., which helps to promote the sustainable development of the construction industry and realize the coordinated development of economy, society and environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] 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 be obtained based on these drawings. Among them:

[0029] Figure 1 Schematic diagram of the compressive strength of the samples of Example 1 and Comparative Example 1 of a microgel-reinforced and toughened formaldehyde-free wood adhesive of the present invention at 3d, 7d, and 28d. Specific embodiments

[0030] To make the above objects, features, and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below with reference to the drawings. It should be understood that the examples given in the embodiments of the present invention are only for the purpose of illustration and are not used to limit the scope of the present invention. Those skilled in the art can make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention, and all belong to the scope of the present invention.

[0031] The experimental methods used in the embodiments of the present invention are all conventional operation methods unless otherwise specified. The materials, reagents, etc. used in the embodiments of the present invention can be obtained from the market unless otherwise specified.

[0032] The present invention provides a microgel-reinforced and toughened formaldehyde-free wood adhesive and a preparation method thereof, which solves the problem of the inherent brittleness of magnesium oxychloride cement in the prior art and enhances the toughness of the product. In addition, it can also solve the problems of poor water resistance of magnesium oxychloride cement and the existence of a weak interface layer at the bonding interface.

[0033] The microgel-reinforced and toughened formaldehyde-free wood adhesive includes:

[0034] Light-burned heavy magnesium oxide, magnesium chloride hexahydrate, water, microgel hybrid, hybrid fiber, filler.

[0035] Among them, 70-105 parts of light-burned heavy magnesium oxide, 60-70 parts of magnesium chloride hexahydrate, 35-45 parts of water, the addition amount of the microgel hybrid is 1.6-2.0% of the total mass of light-burned heavy magnesium oxide, magnesium chloride hexahydrate and water, the addition amount of the hybrid fiber is 2% of the total mass of light-burned heavy magnesium oxide, magnesium chloride hexahydrate, water and filler, and the addition amount of the filler is 25-30% of the mass of the replaced light-burned heavy magnesium oxide.

[0036] Among them, the calcination temperature for manufacturing the light-burned heavy magnesium oxide needs to be <1000°C. Further preferably, the MgO with a calcination temperature in the range of 800-900°C is used. The activity of the light-burned magnesium oxide is 60-70%, and the magnesium oxide content is 80-90%. The hybrid fiber is a mixed combination of polyethylene fiber and basalt fiber, among which the polyethylene fiber is 62.5% and the basalt fiber is 37.5%. The filler is any one or more of mine tailings powder, slag, silica fume, fly ash, waste silicon powder, talc powder, diatomite, etc. The particle size of the filler is ≥120 mesh.

[0037] The preparation method of this kind of microgel-reinforced and toughened formaldehyde-free wood adhesive is as follows:

[0038] S1. Weigh magnesium chloride hexahydrate and completely dissolve it in water to form a uniform MgCl2 aqueous solution;

[0039] S2. Weigh the light-burned heavy magnesium oxide and the filler, mix them evenly, and add them to the MgCl2 aqueous solution and stir to form a uniform magnesium oxychloride cement slurry;

[0040] S3. Weigh the hybrid fiber, add it to the magnesium oxychloride cement slurry obtained in step S2, and stir at a speed of 10000 rpm for 5 min;

[0041] S4. Uniformly disperse the microgel hybrid into the magnesium oxychloride cement slurry obtained in step S3, stir evenly, and obtain the microgel-reinforced and toughened formaldehyde-free wood adhesive.

[0042] Among them, the specific preparation steps of the microgel hybrid are as follows:

[0043] Dissolve 2.0-5.0 kg of quaternized chitosan, 0.5-2.1 kg of acrylic acid, and 5.5-9.5 kg of citric acid in 25 kg of deionized water one by one, stir well to form a transparent mixed solution; then add 12.5 kg of acrylamide and stir well; add 5.0 g of cross-linking agent N,N′-methylenebisacrylamide, and stir magnetically at room temperature for 30 min; finally, add 50 g of initiator ammonium persulfate and 45-55 g of biomass acid in sequence, and stir well for a period of time to obtain the microgel hybrid. As a preference, the biomass acid can be any one or more of gallic acid, caffeic acid, chlorogenic acid, tannic acid, and protocatechuic acid.

[0044] In order to verify the performance of the above microgel-reinforced and toughened formaldehyde-free wood adhesive of the present invention, the following Examples 1-6 and Comparative Examples 1-5 are provided for comparative verification.

[0045] Example 1

[0046] A preparation method of a microgel-reinforced and toughened formaldehyde-free wood adhesive includes the following steps:

[0047] S1. Weigh 60 kg of magnesium chloride hexahydrate and completely dissolve it in 37 kg of water to form a homogeneous aqueous MgCl₂ solution;

[0048] S2. Weigh 77.4 kg of light-burned heavy magnesium oxide and 25.9 kg of filler, mix them evenly, and add them to the aqueous MgCl₂ solution and stir to form a homogeneous magnesium oxychloride cement slurry;

[0049] S3. Weigh 4.0 kg of hybrid fiber, add it to the magnesium oxychloride cement slurry obtained in step S2, and stir at a speed of 10,000 rpm for 5 minutes;

[0050] S4. Uniformly disperse 2.79 kg of microgel hybrid into the magnesium oxychloride cement slurry obtained in step S3, stir evenly to obtain a microgel-reinforced and toughened formaldehyde-free wood adhesive.

[0051] Example 2

[0052] S1. Weigh 60 kg of magnesium chloride hexahydrate and completely dissolve it in 37 kg of water to form a homogeneous aqueous MgCl₂ solution;

[0053] S2. Weigh 77.4 kg of light-burned heavy magnesium oxide and 25.9 kg of filler, mix them evenly, and add them to the aqueous MgCl₂ solution and stir to form a homogeneous magnesium oxychloride cement slurry;

[0054] S3. Weigh 4.0 kg of hybrid fiber, add it to the magnesium oxychloride cement slurry obtained in step S2, and stir at a speed of 10,000 rpm for 5 minutes;

[0055] S4. Uniformly disperse 3.14 kg of microgel hybrid into the magnesium oxychloride cement slurry obtained in step S3, stir evenly to obtain a microgel-reinforced and toughened formaldehyde-free wood adhesive.

[0056] Example 3

[0057] S1. Weigh 60 kg of magnesium chloride hexahydrate and completely dissolve it in 37 kg of water to form a homogeneous aqueous MgCl₂ solution;

[0058] S2. Weigh 77.4 kg of light-burned heavy magnesium oxide and 25.9 kg of filler, mix them evenly, and add them to the aqueous MgCl₂ solution and stir to form a homogeneous magnesium oxychloride cement slurry;

[0059] S3. Weigh 4.0 kg of hybrid fiber, add it to the magnesium oxychloride cement slurry obtained in step S2, and stir at a speed of 10,000 rpm for 5 minutes;

[0060] S4. Uniformly disperse 3.49 kg of microgel hybrid into the magnesium oxychloride cement slurry obtained in step S3, stir evenly to obtain a microgel-reinforced and toughened formaldehyde-free wood adhesive.

[0061] Example 4

[0062] S1. Weigh 60 kg of magnesium chloride hexahydrate and completely dissolve it in 37 kg of water to form a uniform aqueous MgCl₂ solution;

[0063] S2. Weigh 72.2 kg of light-burned heavy magnesium oxide and 31.0 kg of filler, mix them evenly, and add them to the aqueous MgCl₂ solution and stir to form a uniform magnesium oxychloride cement slurry;

[0064] S3. Weigh 4.0 kg of hybrid fiber, add it to the magnesium oxychloride cement slurry obtained in step S2, and stir at a speed of 10,000 rpm for 5 min;

[0065] S4. Disperse 2.70 kg of microgel hybrid evenly into the magnesium oxychloride cement slurry obtained in step S3, stir evenly to obtain a microgel-reinforced and toughened formaldehyde-free wood adhesive.

[0066] Example 5

[0067] S1. Weigh 60 kg of magnesium chloride hexahydrate and completely dissolve it in 37 kg of water to form a uniform aqueous MgCl₂ solution;

[0068] S2. Weigh 72.2 kg of light-burned heavy magnesium oxide and 31.0 kg of filler, mix them evenly, and add them to the aqueous MgCl₂ solution and stir to form a uniform magnesium oxychloride cement slurry;

[0069] S3. Weigh 4.0 kg of hybrid fiber, add it to the magnesium oxychloride cement slurry obtained in step S2, and stir at a speed of 10,000 rpm for 5 min;

[0070] S4. Disperse 3.05 kg of microgel hybrid evenly into the magnesium oxychloride cement slurry obtained in step S3, stir evenly to obtain a microgel-reinforced and toughened formaldehyde-free wood adhesive.

[0071] Example 6

[0072] S1. Weigh 60 kg of magnesium chloride hexahydrate and completely dissolve it in 37 kg of water to form a uniform aqueous MgCl₂ solution;

[0073] S2. Weigh 72.2 kg of light-burned heavy magnesium oxide and 31.0 kg of filler, mix them evenly, and add them to the aqueous MgCl₂ solution and stir to form a uniform magnesium oxychloride cement slurry;

[0074] S3. Weigh 4.0 kg of hybrid fiber, add it to the magnesium oxychloride cement slurry obtained in step S2, and stir at a speed of 10,000 rpm for 5 min;

[0075] S4. Uniformly disperse 3.38 kg of the microgel hybrid into the magnesium oxychloride cement slurry obtained in step S3, and stir evenly to obtain a microgel-reinforced and toughened formaldehyde-free wood adhesive.

[0076] Comparative Example 1

[0077] S1. Weigh 60 kg of magnesium chloride hexahydrate and completely dissolve it in 37 kg of water to form a uniform MgCl2 aqueous solution;

[0078] S2. Weigh 103 kg of light-burned heavy magnesium oxide, add it to the MgCl2 aqueous solution, and stir to form a uniform magnesium oxychloride cement slurry.

[0079] Comparative Example 2

[0080] S1. Weigh 60 kg of magnesium chloride hexahydrate and completely dissolve it in 37 kg of water to form a uniform MgCl2 aqueous solution;

[0081] S2. Weigh 77.4 kg of light-burned heavy magnesium oxide and 25.9 kg of filler, mix them evenly, add them to the MgCl2 aqueous solution, and stir to form a uniform magnesium oxychloride cement slurry.

[0082] Comparative Example 3

[0083] S1. Weigh 60 kg of magnesium chloride hexahydrate and completely dissolve it in 37 kg of water to form a uniform MgCl2 aqueous solution;

[0084] S2. Weigh 72.2 kg of light-burned heavy magnesium oxide and 31.0 kg of filler, mix them evenly, add them to the MgCl2 aqueous solution, and stir to form a uniform magnesium oxychloride cement slurry.

[0085] Comparative Example 4

[0086] S1. Weigh 60 kg of magnesium chloride hexahydrate and completely dissolve it in 37 kg of water to form a uniform MgCl2 aqueous solution;

[0087] S2. Weigh 77.4 kg of light-burned heavy magnesium oxide and 25.9 kg of filler, mix them evenly, add them to the MgCl2 aqueous solution, and stir to form a uniform magnesium oxychloride cement slurry;

[0088] S3. Weigh 4.0 kg of hybrid fiber, add it to the magnesium oxychloride cement slurry obtained in step S2, and stir at a speed of 10,000 rpm for 5 minutes.

[0089] Comparative Example 5

[0090] S1. Weigh 60 kg of magnesium chloride hexahydrate and completely dissolve it in 37 kg of water to form a uniform MgCl2 aqueous solution;

[0091] S2. Weigh 72.2 kg of light-burned heavy magnesium oxide and 31.0 kg of filler, mix them evenly, and add them to the aqueous MgCl2 solution, then stir to form a uniform magnesium oxychloride cement slurry.

[0092] S3. Weigh 4.0 kg of hybrid fiber, add it to the magnesium oxychloride cement slurry obtained in step S2, and stir at a speed of 10,000 rpm for 5 minutes.

[0093] For the microgel-reinforced and toughened formaldehyde-free wood adhesives prepared in Examples 1 to 6 and the adhesives prepared in Comparative Examples 1 to 5, pour them into a mold (20 mm × 20 mm × 20 mm), after shaking evenly, put the mold into a constant temperature and humidity chamber (25 °C, 5% RH) for curing, and then MOC strength specimens can be obtained.

[0094] For the microgel-reinforced and toughened formaldehyde-free wood adhesives prepared in Examples 1 to 6 and the adhesives prepared in Comparative Examples 1 to 5, pour them into a test mold of 40 mm × 40 mm × 160 mm and vibrate to form. Demold after 48 hours, and measure the flexural strength after curing in a standard curing room for 7 days or 28 days.

[0095] For the microgel-reinforced and toughened formaldehyde-free wood adhesives prepared in Examples 1 to 6 and the adhesives prepared in Comparative Examples 1 to 5, use basswood with a size of 65 mm × 25 mm × 4 mm (length × width × thickness) as the substrate.

[0096] Gluing: Glue both sides of the core board, and the glue application amount is 350 - 400 g / m 2 ;

[0097] Pressing: The pressure is 0.8 MPa and the time is 6 minutes.

[0098] Curing: Cure in a constant temperature and humidity chamber (25 °C, 60 ± 5% RH) for 24 hours, then release the pressure and continue to store for 6 days for testing.

[0099] Detect the formaldehyde release amount of the produced plywood products according to the detection method of GB / T17657 - 1999 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorated Wood-based Panels".

[0100] The experimental results show that the formaldehyde release amount of the three-layer plywood manufactured by the microgel-reinforced and toughened formaldehyde-free wood adhesive of the present invention is not detected. As Figure 1As shown, in the examples, the compressive strength of the microgel-reinforced and toughened formaldehyde-free wood adhesive reaches over 67 MPa for the 3-day compressive strength, over 72 MPa for the 7-day compressive strength, and over 56 MPa for the compressive strength after soaking in water for 7 days. Compared with Comparative Examples 1-5, the water resistance coefficient of the microgel-reinforced and toughened formaldehyde-free wood adhesive in Examples 1-6 reaches over 0.83, and the water resistance is significantly improved; compared with Comparative Example 1, the flexural strength in Examples 1-6 is significantly improved, indicating that the inherent brittleness problem of magnesium oxychloride cement has been significantly improved, and the toughness of the modified adhesive has been increased.

[0101] Although the present invention has been described above with reference to the embodiments, various modifications can be made thereto and components thereof can be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the features in the embodiments disclosed in the present invention can be combined with each other in any way, and the exhaustive description of the situations of these combinations is omitted in this specification only for the consideration of saving space and resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A microgel-reinforced and toughened formaldehyde-free wood adhesive, characterized in that, Comprising: Light-burned heavy magnesium oxide, magnesium chloride hexahydrate, water, microgel hybrid, hybrid fiber, filler; Among them, 70 - 105 parts of light-burned heavy magnesium oxide, 60 - 70 parts of magnesium chloride hexahydrate, 35 - 45 parts of water, the addition amount of the microgel hybrid is 1.6 - 2.0% of the total mass of light-burned heavy magnesium oxide, magnesium chloride hexahydrate and water, the addition amount of the hybrid fiber is 2% of the total mass of light-burned heavy magnesium oxide, magnesium chloride hexahydrate, water and filler, and the addition amount of the filler is 25 - 30% of the mass replacing light-burned heavy magnesium oxide.

2. The microgel-reinforced and toughened formaldehyde-free wood adhesive according to claim 1, wherein The calcination temperature for manufacturing the light-burned heavy magnesium oxide needs to be <1000 °C, and MgO with a calcination temperature in the range of 800 - 900 °C is further preferably used. The activity of the light-burned magnesium oxide is 60 - 70%, and the magnesium oxide content is 80 - 90%.

3. The microgel-reinforced and toughened formaldehyde-free wood adhesive according to claim 1, wherein The hybrid fiber is a mixed combination of polyethylene fiber and basalt fiber, among which the polyethylene fiber is 10 - 50% and the basalt fiber is 50 - 90%.

4. The microgel-reinforced and toughened formaldehyde-free wood adhesive according to claim 1, characterized in that The filler is any one or more of mine tailing powder, slag, silica fume, fly ash, waste silicon powder, talc powder, diatomaceous earth, etc.

5. The microgel-reinforced and toughened formaldehyde-free wood adhesive according to claim 1, wherein The particle size of the filler ≥ 120 mesh.

6. A preparation method of a microgel-reinforced and toughened formaldehyde-free wood adhesive as described in any one of claims 1-5, characterized in that, The specific steps are as follows: S1. Weigh magnesium chloride hexahydrate and completely dissolve it in water to form a uniform MgCl₂ aqueous solution; S2. Weigh light-burned heavy magnesium oxide and filler and mix them evenly, then add them to the MgCl₂ aqueous solution and stir to form a uniform magnesium oxychloride cement slurry; S3. Weigh the hybrid fiber and add it to the magnesium oxychloride cement slurry obtained in step S2, and stir at a speed of 10000 rpm for 5 min; S4. Uniformly disperse the microgel hybrid into the magnesium oxychloride cement slurry obtained in step S3, and stir evenly to obtain a microgel-reinforced and toughened formaldehyde-free wood adhesive.

7. The preparation method of a microgel-reinforced and toughened formaldehyde-free wood adhesive according to claim 6, characterized in that, The specific preparation steps of the microgel hybrid are as follows: S1. Dissolve a certain amount of quaternized chitosan, acrylic acid and citric acid in deionized water one by one, and stir well to form a transparent mixed solution; S2. Add a certain amount of acrylamide and crosslinking agent N,N′-methylenebisacrylamide, and stir magnetically at room temperature for 30 min; S3. Finally, add an appropriate amount of initiator ammonium persulfate and biomass acid in sequence, and stir well for a period of time to obtain the microgel hybrid.

8. The preparation method of a microgel-reinforced and toughened formaldehyde-free wood adhesive according to claim 7, characterized in that, The biomass acid is any one or more of gallic acid, caffeic acid, chlorogenic acid, tannic acid and protocatechuic acid.

9. The preparation method of a microgel-reinforced and toughened formaldehyde-free wood adhesive according to claims 6-7, characterized in that, The mixing is carried out under the condition of room temperature (25 ± 2 °C).

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