Enhanced magnesium cementing material as well as preparation method and application thereof

Abstract

The invention relates to an enhanced magnesium cementing material and a preparation method thereof. The enhanced magnesium cementing material is prepared from the following raw materials in parts by weight: 1-5 parts of carbon dot modified hydrosol, 5-15 parts of magnesium sulfate, 25-35 parts of magnesium chloride, 95-105 parts of magnesium oxide and 0.001-0.01 part of boric acid, and the carbon dot modified hydrosol is prepared by hydrothermal reaction of a hydrosol precursor in the presence of a cross-linking agent and an oxidizing agent, the condition of the hydrothermal reaction is that the temperature is 120-150 DEG C. The carbon dot modified hydrosol provided by the invention has excellent permeability and bonding strength, the magnesium oxychloride inorganic glue enhances the mechanical strength of the cementing material, the magnesium sulfate inorganic glue enhances the water resistance of the cementing material, and under the cooperation of the three, the obtained cementing material has the advantages of high mechanical and bonding strength and good water resistance; the flame-retardant effect is relatively good. The invention further relates to plywood containing the enhanced magnesium cementing material and a preparation method of the plywood.

Description

Technical Field

[0001] The invention relates to the technical field of artificial boards, and in particular to a reinforced magnesium cementitious material and a preparation method thereof, a plywood containing the reinforced magnesium cementitious material and a preparation method thereof. Background Art

[0002] Plywood is a three-layer or multi-layer board material made by peeling wood segments into veneers or planing wood blocks into veneers, and then gluing them with cementing materials. As the most produced and used man-made board, it is widely used in furniture manufacturing, construction, packaging and other fields. At present, more than 10 million tons of cementing materials are consumed annually in the process of plywood manufacturing, and aldehyde resins are widely used with a proportion of more than 90%. This type of cementing material will release free formaldehyde during production and use, which is harmful to human health. At the same time, this type of man-made board is a combustible material like wood, and there is a fire hazard. Therefore, it is necessary to develop wood cementing materials that are free of formaldehyde and have flame retardant effects to prepare plywood, which has great development prospects.

[0003] Among the existing inorganic gelling materials, magnesium sulfate gelling material is a gelling system formed by mixing active magnesium oxide and magnesium sulfate solution in a certain proportion, which has a series of advantages such as simple preparation process, light weight, fast coagulation speed, green environmental protection, fire resistance and good compatibility with wood. However, the application of magnesium sulfate gelling material in the field of artificial boards is also limited by its own low strength and weak interface bonding with wood. Summary of the invention

[0004] In view of the above problems, one of the purposes of the present invention is to provide a reinforced magnesium cementitious material with high mechanical strength and high bonding strength and a preparation method thereof. The reinforced magnesium cementitious material comprises a magnesium sulfate / magnesium oxychloride / carbon point modified hydrosol composite system, has the advantages of high mechanical and bonding strength, good water resistance, and good flame retardant effect.

[0005] Another object of the present invention is to provide a plywood comprising the above-mentioned enhanced magnesium cementitious material having high mechanical strength and high bonding strength and a preparation method thereof.

[0006] To this end, in a first aspect, the present invention provides a reinforced magnesium cementitious material, the raw materials of which include, by weight:

[0007]

[0008] The carbon dot modified hydrosol is prepared by hydrothermal reaction of a hydrosol precursor in the presence of a crosslinking agent and an oxidant, and the conditions of the hydrothermal reaction include: a temperature of 120 to 150°C.

[0009] The carbon point modified hydrosol of the present invention can generate carbon nanomaterials (carbon quantum dots, also referred to as carbon dots) by hydrothermal reaction (depolymerization, self-assembly) of hydrosol precursor, oxidant and crosslinking agent, which has good water solubility, can self-crosslink into film after drying and can no longer be dissolved in water, and has excellent strength and water resistance. During the hydrothermal reaction, a part of the carbon-containing material in the hydrothermal system forms carbon points, and a part of the hydrosol is depolymerized. Since the reaction temperature is not the traditional high temperature of more than 200°C, the system still maintains good film-forming properties. Therefore, when the carbon point modified hydrosol is mixed with the inorganic gelling components of magnesium chloride, magnesium oxide and magnesium sulfate, the carbon point modified hydrosol is evenly distributed in the inorganic gelling system and coated on the surface of the veneer. Due to the high temperature hydrothermal breaking the molecular state of the original system, the original linear as the main body is transformed into a modified system with nanoparticles and broken small molecular segments as the main body, which can also form a good combination with the wood, and it is easy to form a more solid anchoring effect with the help of the micropores on the surface of the veneer.

[0010] Aiming at the problems that the existing magnesium sulfate inorganic gelling materials have low mechanical strength, the magnesium oxychloride inorganic gelling materials have poor water resistance, and the inorganic glue and wood have weak interface bonding, the present invention uses carbon point modified hydrosol to compound magnesium oxychloride and magnesium sulfate inorganic glue, the carbon point modified hydrosol used has excellent permeability and bonding strength, the magnesium oxychloride inorganic glue enhances the mechanical strength of the gelling material, and the magnesium sulfate inorganic glue enhances the water resistance of the gelling material, and the obtained gelling material has the advantages of high mechanical and bonding strength, good water resistance, and good flame retardant effect under the combination of the three.

[0011] As a specific embodiment of the present invention, the conditions of the hydrothermal reaction also include: in a closed environment, time 1 to 3 hours.

[0012] As a specific embodiment of the present invention, the hydrosol precursor is selected from at least one of hyaluronic acid, gelatin, chitosan and sodium alginate.

[0013] As a specific embodiment of the present invention, the number average molecular weight of the hydrosol precursor is 2.0×10 4 ~6.5×10 4 g / mol.

[0014] As a specific embodiment of the present invention, the number average molecular weight of the gelatin is 2.4×10 4 ~3.6×10 4 g / mol; the number average molecular weight of the hyaluronic acid is 4.5×10 4 ~6.5×10 4 g / mol.

[0015] As a specific embodiment of the present invention, the oxidant is selected from at least one of hydrogen peroxide, sodium hypochlorite and perchloric acid.

[0016] As a specific embodiment of the present invention, the amount of the oxidant is 1.0-2.5% of the mass of the hydrosol precursor.

[0017] As a specific embodiment of the present invention, the cross-linking agent is selected from at least one of cationic polyacrylamide, carboxylated polyacrylamide and hydroxy polyacrylamide.

[0018] As a specific embodiment of the present invention, the amount of the cross-linking agent is 0.1-0.3% of the mass of the hydrosol precursor.

[0019] As a specific embodiment of the present invention, the number average molecular weight of the cross-linking agent is 2.5×10 6 ~3.5×10 6 g / mol.

[0020] As a specific embodiment of the present invention, the number average molecular weight of the cationic polyacrylamide is 3×10 6 ~3.4×10 6 g / mol.

[0021] As a specific embodiment of the present invention, the preparation method of the carbon dot modified hydrosol comprises the following steps:

[0022] S1, adding a crosslinking agent and an oxidant to the hydrosol precursor aqueous solution, and mixing at a first temperature to obtain a mixed solution;

[0023] S2. placing the mixed solution in a closed reactor for hydrothermal reaction to obtain a carbon dot-modified hydrosol solution.

[0024] As a specific embodiment of the present invention, the first temperature is 40-60°C.

[0025] As a specific embodiment of the present invention, the preparation method of the modified hydrosol comprises the following steps:

[0026] S10, stirring an aqueous solution of a hydrosol precursor having a mass fraction of 1-5 wt % and cationic polyacrylamide in a constant temperature water bath at 40-60° C. to obtain a mixed solution;

[0027] S20, adding a 30-45wt% hydrogen peroxide solution into the mixed solution obtained in step S10, and continuing stirring;

[0028] S30, placing the mixed solution obtained in step S20 in a closed reactor for hydrothermal reaction to obtain a solution of carbon dot-modified hydrosol.

[0029] As a specific implementation of the present invention, in step S10, the stirring rate is 300-350 r / min, and the time is 20-40 min.

[0030] As a specific implementation of the present invention, in step S20, the stirring rate is 300-350 r / min, and the time is 5-20 min.

[0031] To this end, in a second aspect, the present invention provides a method for preparing the above-mentioned enhanced magnesium gelling material, comprising the following steps: a first mixing of carbon dot-modified hydrosol, magnesium sulfate, magnesium chloride, and magnesium oxide, and then a second mixing by adding boric acid; preferably, the temperatures of the first mixing and the second mixing are independently 20 to 40°C.

[0032] To this end, in a third aspect, the present invention provides a plywood, wherein the board is glued together using the above-mentioned enhanced magnesium cementitious material or the enhanced magnesium cementitious material obtained by the above-mentioned preparation method; preferably, the board is preferably a wooden board.

[0033] To this end, in a fourth aspect, the present invention provides a method for preparing a plywood, comprising the following steps:

[0034] (1) Veneer preparation: making wood into veneer;

[0035] (2) sizing of the veneer: uniformly coating the above-mentioned enhanced magnesium cementitious material or the enhanced magnesium cementitious material prepared by the above-mentioned preparation method on both sides of the veneer prepared in step (1);

[0036] (3) Assembling and cold pressing: assembling and cold pressing the veneer sheets after gluing in step (2);

[0037] (4) Board maintenance.

[0038] As a specific embodiment of the present invention, step (1) further includes: drying the veneer to a moisture content of 5 to 10 wt%.

[0039] As a specific embodiment of the present invention, in step (2), the glue application amount on one side of the veneer is 200 to 300 g / m 2 .

[0040] As a specific embodiment of the present invention, in step (3), the conditions for assembling the blanks include: following the principles of odd number of layers, symmetry and interlayer texture arrangement.

[0041] As a specific embodiment of the present invention, the cold pressing conditions include: temperature of 10-35° C., pressure of 1.0-1.5 MPa, and time of 24-72 h.

[0042] As a specific embodiment of the present invention, the curing conditions of the plate include: curing at 20-70° C. for 2-7 days.

[0043] Beneficial effects:

[0044] Aiming at the problems that the existing magnesium sulfate inorganic gelling materials have low mechanical strength, the magnesium oxychloride inorganic gelling materials have poor water resistance, and the inorganic glue and wood have weak interface bonding, the present invention uses carbon point modified hydrosol to compound magnesium oxychloride and magnesium sulfate inorganic glue, the carbon point modified hydrosol used has excellent permeability and bonding strength, the magnesium oxychloride inorganic glue enhances the mechanical strength of the gelling material, and the magnesium sulfate inorganic glue enhances the water resistance of the gelling material, and the obtained gelling material has the advantages of high mechanical and bonding strength, good water resistance, and good flame retardant effect under the combination of the three.

[0045] The enhanced magnesium cementitious material provided by the present invention improves the mechanical strength of the cementitious material by blending magnesium oxychloride and magnesium sulfate. When the inorganic cementitious components of the carbon dot-modified hydrosol, magnesium chloride, magnesium oxide and magnesium sulfate, are mixed, the carbon dot-modified hydrosol is evenly distributed in the inorganic cementitious system and coated on the surface of the veneer. Due to the high-temperature hydrothermal treatment, the molecular state of the original system is broken, so that the original linear system as the main body is transformed into a modified system with nanoparticles and broken small molecular segments as the main body. The modified system can also form a better combination with the wood, and the micropores on the surface of the veneer are used to easily form a stronger anchoring effect, thereby enhancing the permeability, bonding strength and moisture resistance of the cementitious material.

[0046] The enhanced magnesium cementitious material provided by the present invention has the advantages of high mechanical and bonding strength, and a simple preparation process. No formaldehyde is released during production and use, and it also has the advantages of health and environmental protection. As a wood cementitious material, it also gives plywood flame retardant properties and moisture resistance.

[0047] The enhanced magnesium cementitious material provided by the present invention can be applied in the form of plates at room temperature without the need for hot pressing, thereby saving energy and being environmentally friendly.

[0048] The plywood provided by the present invention has excellent physical and mechanical properties, flame retardant properties, moisture resistance, and no volatile formaldehydes, which can avoid harm to the environment, further improving the added value and application scope of the plywood, and having good promotion prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a schematic diagram of the internal structure of the plywood prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0050] The technical scheme of the present invention is further described below by specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0051] The number average molecular weight of gelatin in the embodiment is 3.0×10 4 The number average molecular weight of cationic polyacrylamide is 3.2×10 6 g / mol, and the number average molecular weight of hyaluronic acid is 5.4×10 4 .

[0052] Example 1

[0053] The preparation of the enhanced magnesium cementitious material is carried out according to the following steps:

[0054] (1) Weigh 100 g of a gelatin aqueous solution (concentration: 2 wt%) and 0.002 g of cationic polyacrylamide, and stir them at a speed of 320 r / min for 30 min in a 50° C. constant temperature water bath to fully dissolve and mix the above components to obtain a mixed solution;

[0055] (2) adding 0.15 g of a 37 wt % aqueous hydrogen peroxide solution to the mixed solution obtained in step (1), and stirring at a speed of 320 r / min for 10 min;

[0056] (3) placing the mixed solution obtained in step (2) in a sealed reaction vessel (250 mL) and subjecting it to a hydrothermal reaction at a temperature of 120° C. for 2 h, so that the hydrosol precursor, the oxidant, and the cross-linking agent undergo depolymerization and self-assembly reaction under high temperature hydrothermal conditions. After the reaction is completed, the temperature is cooled to room temperature to obtain a light yellow solution;

[0057] (4) 100 g of the carbon dot-modified aqueous sol solution (2 wt%) obtained in step (3) was stirred with 10 g of magnesium sulfate, 30 g of magnesium chloride, and 100 g of magnesium oxide at a speed of 320 r / min for 30 min, and then 1.0 mg of boric acid was added under stirring to obtain the enhanced magnesium gelling material.

[0058] Example 2

[0059] The preparation of the enhanced magnesium cementitious material is carried out according to the following steps:

[0060] (1) Weigh 100 g of a hyaluronic acid aqueous solution (concentration: 2 wt%) and 0.002 g of cationic polyacrylamide, and stir them at a speed of 320 r / min for 30 min in a 50° C. constant temperature water bath to fully dissolve and mix the above components to obtain a mixed solution;

[0061] (2) adding 0.15 g of a 37 wt % aqueous hydrogen peroxide solution to the mixed solution obtained in step (1), and stirring at a speed of 320 r / min for 10 min;

[0062] (3) placing the mixed solution obtained in step (2) in a sealed reaction vessel (250 mL) and subjecting it to a hydrothermal reaction at a temperature of 120° C. for 2 h, so that the hydrosol precursor, the oxidant, and the cross-linking agent undergo depolymerization and self-assembly reaction under high temperature hydrothermal conditions. After the reaction is completed, the temperature is cooled to room temperature to obtain a light yellow solution;

[0063] (4) 100 g of the carbon dot-modified aqueous sol solution (2 wt%) obtained in step (3) was stirred with 10 g of magnesium sulfate, 30 g of magnesium chloride, and 100 g of magnesium oxide at a speed of 320 r / min for 30 min, and then 1.0 mg of boric acid was added under stirring to obtain the enhanced magnesium gelling material.

[0064] Example 3

[0065] The preparation of the enhanced magnesium cementitious material is carried out according to the following steps:

[0066] (1) Weigh 100 g of sodium alginate aqueous solution (concentration: 2 wt%) and 0.002 g of cationic polyacrylamide, and stir at 320 r / min for 30 min in a 50° C. constant temperature water bath to fully dissolve and mix the above components to obtain a mixed solution;

[0067] (2) adding 0.15 g of a 37 wt % aqueous hydrogen peroxide solution to the mixed solution obtained in step (1), and stirring at a speed of 320 r / min for 10 min;

[0068] (3) placing the mixed solution obtained in step (2) in a sealed reaction vessel (250 mL) and subjecting it to a hydrothermal reaction at a temperature of 120° C. for 2 h, so that the hydrosol precursor, the oxidant, and the cross-linking agent undergo depolymerization and self-assembly reaction under high temperature hydrothermal conditions. After the reaction is completed, the temperature is cooled to room temperature to obtain a light yellow solution;

[0069] (4) 100 g of the carbon dot-modified aqueous sol solution (concentration of 2 wt%) obtained in step (3) was stirred with 10 g of magnesium sulfate, 30 g of magnesium chloride, and 100 g of magnesium oxide at a speed of 320 r / min for 30 min, and then 1.0 mg of boric acid was added under stirring to obtain the enhanced magnesium gelling material.

[0070] Example 4

[0071] The preparation of the enhanced magnesium cementitious material is carried out according to the following steps:

[0072] (1) Weigh 100 g of a gelatin aqueous solution (concentration: 2 wt%) and 0.004 g of cationic polyacrylamide, and stir them at a speed of 320 r / min for 30 min in a 50° C. constant temperature water bath to fully dissolve and mix the above components to obtain a mixed solution;

[0073] (2) adding 0.15 g of a 37 wt % aqueous perchloric acid solution to the mixed solution obtained in step (1), and stirring at a speed of 320 r / min for 10 min;

[0074] (3) placing the mixed solution obtained in step (2) in a sealed reaction vessel (250 mL) and subjecting it to a hydrothermal reaction at a temperature of 120° C. for 2 h, so that the hydrosol precursor, the oxidant, and the cross-linking agent undergo depolymerization and self-assembly reaction under high temperature hydrothermal conditions. After the reaction is completed, the temperature is cooled to room temperature to obtain a light yellow solution;

[0075] (4) 100 g of the carbon dot-modified aqueous sol solution (concentration of 2 wt%) obtained in step (3) was stirred with 10 g of magnesium sulfate, 35 g of magnesium chloride, and 105 g of magnesium oxide at a speed of 320 r / min for 30 min, and then 2.0 mg of boric acid was added under stirring to obtain the enhanced magnesium gel material.

[0076] Comparative Example 1

[0077] The difference from Example 1 is that the temperature of the hydrothermal reaction in step (3) is 160°C.

[0078] Comparative Example 2

[0079] The difference from Example 1 is that the temperature of the hydrothermal reaction in step (3) is 180°C.

[0080] Comparative Example 3

[0081] The difference from Example 1 is that only cationic polyacrylamide is added to the hydrosol modification without adding hydrogen peroxide. The following steps are performed:

[0082] (1) Weigh 100 g of a gelatin aqueous solution (concentration: 2 wt%) and 0.002 g of cationic polyacrylamide, and stir them at a speed of 320 r / min for 30 min in a 50° C. constant temperature water bath to fully dissolve and mix the above components to obtain a mixed solution;

[0083] (2) placing the mixed solution obtained in step (1) in a sealed reaction vessel (250 mL) and subjecting it to a hydrothermal reaction at 120° C. for 2 h, so that the hydrosol precursor and the cross-linking agent undergo depolymerization and self-assembly reaction under high temperature hydrothermal conditions. After the reaction is completed, the temperature is cooled to room temperature to obtain a light yellow solution;

[0084] (3) 100 g of the mixed solution (2 wt%) obtained in step (2) was stirred with 10 g of magnesium sulfate, 30 g of magnesium chloride, and 100 g of magnesium oxide at a speed of 320 r / min for 30 min, and then 1.0 mg of boric acid was added under stirring to obtain a gelling material.

[0085] Comparative Example 4

[0086] The difference from Example 1 is that only hydrogen peroxide is added to the hydrosol modification without adding cationic polyacrylamide. The following steps are performed:

[0087] (1) Weigh 100 g of a gelatin aqueous solution (concentration: 2 wt%) and stir at 320 r / min for 30 min in a 50° C. constant temperature water bath to fully dissolve the above components;

[0088] (2) adding 0.15 g of a 37 wt % aqueous hydrogen peroxide solution to the solution in step (1), and stirring at a speed of 320 r / min for 10 min;

[0089] (3) placing the mixed solution obtained in step (2) in a sealed reaction vessel (250 mL) and subjecting it to a hydrothermal reaction at a temperature of 120° C. for 2 h, so that the hydrosol precursor, the oxidant, and the cross-linking agent undergo depolymerization and self-assembly reaction under high temperature hydrothermal conditions. After the reaction is completed, the temperature is cooled to room temperature to obtain a light yellow solution;

[0090] (4) 100 g of the carbon dot-modified aqueous sol solution (2 wt%) obtained in step (3) was stirred with 10 g of magnesium sulfate, 30 g of magnesium chloride, and 100 g of magnesium oxide at a speed of 320 r / min for 30 min, and then 1.0 mg of boric acid was added under stirring to obtain the enhanced magnesium gelling material.

[0091] Comparative Example 5

[0092] The difference from Example 1 is that the mass of magnesium oxide is changed from 100 g to 90 g.

[0093] Comparative Example 6

[0094] The difference from Example 1 is that the mass of boric acid is changed from 1 mg to 0.5 mg.

[0095] Application Example 1

[0096] The preparation of plywood is carried out according to the following steps:

[0097] (1) using a rotary cutter to peel the eucalyptus wood into veneers with a thickness of 2.0 mm ± 0.2 mm, drying to a moisture content of 8 wt %, and cutting to a size of 1200 mm × 600 mm;

[0098] (2) Gluing of veneers: The cementitious materials prepared in Examples 1-4 and Comparative Examples 1-6 were respectively selected and mixed, and the mixed cementitious materials were evenly coated on both sides of the core layer veneer. Only the inner layers of the two outermost veneers were coated with glue, and the glue application amount on one side of the veneer was 250 g / m 2 ;

[0099] (3) assembling the veneer obtained in step (2) according to the principle of odd number of layers, symmetry and interlayer texture arrangement, and then cold pressing at room temperature (25° C.) and 1.2 MPa pressure for 48 hours, wherein the cold pressing pressure is 1.2 MPa;

[0100] (4) Board curing: The plywood after pressure relief was cured at 70° C. for 2 days and then cured at room temperature for 5 days. The boards were denoted as P1-4 (corresponding to Examples 1-4, respectively) and DP1-6 (corresponding to Examples 1-6, respectively).

[0101] The mechanical strength, moisture resistance and flame retardancy of the panels P1-4 and DP1-6 were tested respectively. The test methods and test results are as follows:

[0102] (1) Static bending strength test: Refer to GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and veneer wood-based panels" to test the static bending strength of the board, where the span is 20 times the board thickness.

[0103] (2) Moisture resistance test: Refer to GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and veneer wood-based panels" to test the 24h water absorption thickness expansion rate and Class II immersion peeling performance of the board. The 24h absorption thickness expansion rate (TS-24h) is to immerse a 50mm×50mm board in water at room temperature and test the expansion degree of the board after 24 hours. The smaller the TS-24h, the smaller the water absorption expansion of the board and the better the moisture resistance. The Class II immersion peeling test is to immerse a 75mm×75mm sample in 65℃ water for 3 hours, and then heat treat it in a 65℃ oven for 3 hours. Observe whether the glue layers of the plywood are debonded or cracked, and record the crack length of one side of the glue layer. In this test, samples with a single-side crack exceeding 25mm are recorded as unqualified.

[0104] (3) Flame retardant performance test: Refer to GB / T 2406.2-2009 "Determination of Combustion Behavior of Plastics by Oxygen Index Method" to test the oxygen index of the board. The higher the oxygen index, the better the flame retardant performance. According to production practice, the oxygen index (LOI) of plywood exceeds 35% (≥35%), indicating that the flame retardant effect is good. The oxygen index is lower than 35% and higher than 30% (30% ≤ LOI <35%), indicating that there is a certain flame retardant effect, but the flame retardant effect is weak. The oxygen index is lower than 30% (<30%) and is recorded as combustible material.

[0105] Table 1 Test results of each group of plywood

[0106]

[0107]

[0108] As shown in Table 1, the test groups P1 to P4 all have good static bending strength, low water absorption thickness expansion rate, good immersion peeling performance, and excellent flame retardant oxygen index performance; the carbon point modified hydrosol has good water solubility, can self-crosslink to form a film after drying and can no longer be dissolved in water, and has excellent strength and water resistance. Without wishing to be limited by theory, it is believed that during the hydrothermal process, part of the carbon-containing substances in the hydrothermal system form carbon points, and part of the hydrosol is depolymerized. When the carbon point modified hydrosol is mixed with the inorganic gelling components magnesium chloride, magnesium oxide, and magnesium sulfate, the carbon point modified hydrosol is evenly distributed in the inorganic gelling system and coated on the surface of the veneer. Due to the high temperature hydrothermal breaking the molecular state of the original system, the original linear as the main body is transformed into a modified system with nanoparticles and broken small molecular segments as the main body, which can also form a good combination with the wood, and with the help of the micropores on the surface of the veneer, it is easy to form a more solid anchoring effect.

[0109] The plywood prepared by the control groups DP1 and DP2 has low strength, poor moisture resistance, and unsatisfactory flame retardant effect. Without wishing to be limited by theory, it is believed that due to the high temperature of the hydrothermal reaction, the hydrosol precursor is excessively degraded under the high-temperature hydrothermal action of oxidants, cross-linking agents, aqueous solutions, etc., and the formed carbon point-modified hydrosol cannot maintain good film-forming properties. After subsequent mixing with other components, it does not form an effective anchoring effect, and at the same time causes the cementitious material system to be unbalanced and the porosity to increase. The plywood prepared by the control group DP3 has low strength, poor moisture resistance, and unsatisfactory flame retardant effect. Without wishing to be limited by theory, it is believed that the failure to add an oxidant will weaken the fracture and reorganization behavior of cationic polyacrylamide in a high-temperature hydrothermal environment. The plywood prepared by the control group DP4 has low strength, poor moisture resistance, and unsatisfactory flame retardant effect. Without wishing to be limited by theory, it is believed that due to the failure to add a cross-linking agent, the organic components in the cementitious material have poor water resistance. During the high-temperature heat treatment process, due to the lack of a cross-linking component, the system does not form a good three-dimensional cross-linked structure, so the overall performance is poor. The plywood prepared by the control group DP5 has low strength, poor moisture resistance and unsatisfactory flame retardant effect. Without wishing to be limited by theory, it is believed that the reduction of the content of magnesium oxide in the cementitious material will significantly change the raw material ratio of the cementitious material when forming the inorganic reinforcing phase, resulting in poor reinforcing phase effect. The plywood prepared by the control group DP6 has low strength, poor moisture resistance and unsatisfactory flame retardant effect. Without wishing to be limited by theory, it is believed that due to the low content of boric acid in the cementitious material, the organic matter in the system does not form an effective three-dimensional network cross-linking structure, resulting in a decrease in the comprehensive performance of the cementitious material.

[0110] The above description of the embodiments is to facilitate the understanding and application of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the embodiments herein, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A reinforced magnesium cementitious material, characterized in that: By weight, the raw materials include: The carbon dot modified hydrosol is prepared by hydrothermal reaction of a hydrosol precursor in the presence of a crosslinking agent and an oxidant, and the conditions of the hydrothermal reaction include: a temperature of 120 to 150°C.

2. The cementitious material according to claim 1, characterized in that The conditions of the hydrothermal reaction also include: in a closed environment, for a time of 1 to 3 hours.

3. The cementitious material according to claim 1 or 2, characterized in that: The hydrosol precursor is selected from at least one of hyaluronic acid, gelatin, chitosan and sodium alginate; Preferably, the number average molecular weight of the hydrosol precursor is 2.0×10 4 ~6.5×10 4 g / mol; More preferably, the number average molecular weight of the gelatin is 2.4×10 4 ~3.6×10 4 g / mol; the number average molecular weight of the hyaluronic acid is 4.5×10 4 ~6.5×10 4 g / mol.

4. The cementitious material according to any one of claims 1 to 3, characterized in that: The oxidant is selected from at least one of hydrogen peroxide, sodium hypochlorite and perchloric acid; and / or, The amount of the oxidant used is 1.0-2.5% of the mass of the hydrosol precursor.

5. The cementitious material according to any one of claims 1 to 4, characterized in that: The cross-linking agent is selected from at least one of cationic polyacrylamide, carboxylated polyacrylamide and hydroxy polyacrylamide; and / or, the amount of the cross-linking agent is 0.1-0.3% of the mass of the hydrosol precursor; Preferably, the number average molecular weight of the cross-linking agent is 2.5×10 6 ~3.5×10 6 g / mol; More preferably, the number average molecular weight of the cationic polyacrylamide is 3×10 6 ~3.4×10 6 g / mol.

6. The cementitious material according to any one of claims 1 to 5, characterized in that: The preparation method of the carbon dot modified hydrosol comprises the following steps: S1, adding a crosslinking agent and an oxidant to the hydrosol precursor aqueous solution, and mixing at a first temperature to obtain a mixed solution; S2, placing the mixed solution in a closed reactor for hydrothermal reaction to obtain a carbon dot modified hydrosol solution; Preferably, the first temperature is 40-60°C.

7. A method for preparing the enhanced magnesium cementitious material according to any one of claims 1 to 6, characterized in that: The following steps are involved: The carbon dot modified hydrosol, magnesium sulfate, magnesium chloride and magnesium oxide are first mixed, and then boric acid is added for second mixing; preferably, the temperatures of the first mixing and the second mixing are independently 20-40°C.

8. A plywood, characterized in that: The board is glued using the reinforced magnesium cementitious material according to any one of claims 1 to 6 or the reinforced magnesium cementitious material prepared by the preparation method according to claim 7, and the board is preferably a wooden board.

9. A method for preparing plywood, characterized in that: The following steps are involved: (1) Veneer preparation: making wood into veneer; (2) Gluing of single board: uniformly coating the enhanced magnesium cementitious material according to any one of claims 1 to 6 or the enhanced magnesium cementitious material prepared by the preparation method according to claim 7 on both sides of the single board in step (1); (3) Assembling and cold pressing: assembling and cold pressing the veneer sheets after gluing in step (2); (4) Board maintenance.

10. The preparation method according to claim 9, characterized in that: Step (1) further comprises: drying the veneer to a moisture content of 5 to 10 wt %; and / or In step (2), the glue application amount on one side of the veneer is 200-300 g / m 2 ; and / or In step (3), the conditions for the assembly include: following the principles of odd number of layers, symmetry and interlayer texture arrangement; and / or, the conditions for the cold pressing include: temperature of 10 to 35° C., pressure of 1.0 to 1.5 MPa, and time of 24 to 72 h; In step (4), the curing conditions of the plate include: curing at 20 to 70° C. for 2 to 7 days.

Images