Mildew-proof antibacterial ultrathin density board and preparation method thereof

Abstract

The invention relates to the technical field of artificial boards, in particular to a mildew-proof antibacterial ultrathin density board and a preparation method thereof, and the density board is composed of wood fibers, modified attapulgite clay fine powder, melamine urea resin, a silane coupling agent and a mildew-proof antibacterial agent. The preparation method comprises the following steps: carrying out acid treatment and stearic acid modification on the attapulgite clay; the melamine urea-formaldehyde resin is synthesized through a specific process; wood fibers are subjected to alkali treatment and then mixed with modified attapulgite clay fine powder and the like, melamine urea-formaldehyde resin, high-calcium fly ash fine powder, a silane coupling agent and an anti-mildew antibacterial agent are added, and hot press molding is performed after uniform stirring. The density board has relatively high surface bonding strength, static bending intensity and elastic modulus, is remarkable in antibacterial and mildew-proof effects, reduces the content of free formaldehyde in the melamine urea-formaldehyde resin, is excellent in environmental protection performance, reasonable in process, easy for large-scale production and suitable for a humid environment, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of wood-based panels, and particularly to a mildew-proof and antibacterial ultra-thin density board and a preparation method thereof. Background Art

[0002] The mainstream wood-based panels on the market are divided into two categories: solid wood panels and wood-based panels. Among them, solid wood panels can be further divided into hard solid wood panels and soft solid wood panels. Hard solid wood panels are mainly made of some precious wood species. Their boards are firm, durable, and have natural textures, making them an excellent choice for luxury furniture and decoration. However, such boards have disadvantages such as being relatively expensive, having a high processing technology, and stable raw material dimensions. Soft solid wood panels are fast-growing woods. Their boards have a low density and are relatively soft, making it difficult to be used in furniture and interior decorations. It can be seen that solid wood panels are not widely used on the market. Density board is a kind of wood-based panel, mainly made by pressing wood fibers with adhesives. Due to its good physical properties and processing performance, it has been widely used in the fields of furniture manufacturing, architectural decoration, etc.

[0003] The performance of density board is mainly determined by adhesives and their additives. Currently, the adhesives used in the production of density board are urea-formaldehyde resin, melamine-urea-formaldehyde resin, and phenolic resin. The melamine-urea-formaldehyde resin used in the traditional production process of density board has the problem of free formaldehyde release, which poses a potential hazard to the environment and human health. In addition, traditional density boards are prone to mildew and bacteria growth in a humid environment, resulting in a decline in board performance and a shortened service life. At the same time, it may also have an adverse impact on the indoor environment and human health. Therefore, it is of great practical significance to develop an ultra-thin density board with mildew-proof and antibacterial properties and environmental protection.

[0004] In order to overcome these disadvantages of the prior art, the present invention proposes a mildew-proof and antibacterial ultra-thin density board and a preparation method thereof. Through specific raw material ratios and process treatments, not only the antibacterial and mildew-proof properties of the density board are significantly improved, but also the content of free formaldehyde in melamine-urea-formaldehyde resin is effectively reduced. At the same time, it has high physical properties and has broad application prospects. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to propose a mildew-proof and antibacterial ultra-thin density board and a preparation method thereof to solve the problems in the prior art that traditional density boards are prone to mildew and bacteria growth in a humid environment, resulting in a decline in board performance, a shortened service life, and the release of free formaldehyde.

[0006] Based on the above purpose, the present invention provides a mildew-proof and antibacterial ultra-thin density board.

[0007] A mildew-proof and antibacterial ultra-thin density board, comprising the following preparation steps:

[0008] S1: Crush and finely grind attapulgite clay, sieve it through a 200-mesh sieve, put the sieved attapulgite clay powder into an acid solution for acid treatment, stir for 3 - 5 h, filter to remove the acid solution, and filter and wash to obtain acid-treated attapulgite clay powder;

[0009] S2: Prepare the acid-treated attapulgite clay powder into a slurry by adding water. The mass fraction of the slurry is 5%, the inlet temperature is 200 - 220 °C, the outlet temperature is 90 - 110 °C, the air flow pressure is 0.2 - 0.4 MPa, the feeding speed is 3 - 5 mL / min. Spray-dry the slurry, place it in an oven at 250 °C and bake for 2 - 3 h, and cool to obtain attapulgite clay fine powder

[0010] S3: Add the attapulgite clay fine powder to a high-speed mixer, add stearic acid, and stir at a speed of 1500 - 2000 rpm for 30 - 40 min to obtain modified attapulgite clay fine powder;

[0011] S4: Heat formaldehyde to 45 °C, adjust the pH to 7.5 - 8.5, add urea a and melamine a, heat to 85 °C, adjust the pH to 5.0 - 5.5, stir and react for 30 - 40 min, add urea b and melamine b, cool to 80 °C, adjust the pH to 6 - 7, stir and react for 20 - 30 min, add nano-titanium dioxide, maintain the temperature at 60 °C - 65 °C, stir for 10 - 15 min, add urea c and lignin, heat to 70 °C, adjust the pH to 7.0 - 8.0, stir and react for 10 - 20 min, add polyphenylmethane diisocyanate and curing agent, stir evenly to obtain melamine urea formaldehyde resin;

[0012] S5: Put wood fibers into an alkali solution for alkali treatment, soak for 2 - 3 h, add the alkali-treated wood fibers to CaCl 2 solution, stir for 1 - 2 h, add NaOH solution and modified attapulgite clay fine powder, stir at 40 °C - 50 °C for 1 - 2 h, filter, wash, and dry to obtain a modified wood fiber composite material, and control the water content of the modified wood fiber composite material at 12% - 15%;

[0013] S6: Add melamine urea formaldehyde resin, silane coupling agent, and mildew and antibacterial agent to a mixer, premix at 75 °C - 80 °C for 3 - 4 min, the stirring speed is 40 - 45 rpm, keep the stirring speed unchanged, add high-calcium fly ash fine powder and modified wood fiber composite material, heat to 105 °C - 110 °C, mix for 8 - 10 min to obtain a uniformly mixed composite material for mildew and antibacterial ultra-thin density board. Lay the composite material for mildew and antibacterial ultra-thin density board on a forming board blank, and hot-press to form a formed board blank. Trim the board to obtain a mildew and antibacterial ultra-thin density board with a thickness of 1.2 mm.

[0014] Preferably, the composition comprises 75-87 parts of wood fiber, 4-5 parts of modified attapulgite clay fine powder, 10-15 parts of melamine urea formaldehyde resin, 1-2 parts of high calcium fly ash fine powder, 0.3-0.5 part of silane coupling agent, and 0.2-0.3 part of mildew and antibacterial agent.

[0015] Preferably, the high calcium fly ash fine powder is the high calcium fly ash fine powder passing through a 325-mesh sieve.

[0016] Preferably, the mildew and antibacterial agent is composed of cetyltrimethylammonium bromide and N,N-dimethyldidecylammonium chloride, and the mass ratio of cetyltrimethylammonium bromide to N,N-dimethyldidecylammonium chloride is 1:3-5.

[0017] Preferably, the silane coupling agent is 3-ureidopropyltriethoxysilane.

[0018] Preferably, the mass ratio of attapulgite clay to stearic acid is 100:3-5.

[0019] Preferably, the mass ratio of formaldehyde, urea a, urea b, urea c, melamine a, melamine b, nano-titanium dioxide, lignin, diphenylmethane diisocyanate, and curing agent is 100:28-30:12-15:7-10:3-6:1.5-3:0.5-2.0:3-5:6.0-10.5:0.4-0.6.

[0020] Preferably, the curing agent is NH 4 Cl.

[0021] Preferably, the acid solution is 0.6-0.8 mol / L HCl solution.

[0022] Preferably, the alkali solution is 0.8-1.0 mol / L NaOH solution.

[0023] Preferably, the CaCl 2 solution is 0.2 mol / L CaCl 2 solution.

[0024] Preferably, the NaOH solution is 0.2 mol / L NaOH solution.

[0025] Preferably, the dosage ratio of wood fiber, CaCl 2 solution, and NaOH solution is 1 g:14-18 mL:14-18 mL.

[0026] Preferably, the hot pressing pressure for hot pressing forming is 12 MPa, the hot pressing temperature is 160°C - 200°C, and the hot pressing time is 4-6 min.

[0027] Advantages of the present invention:

[0028] 1. Through specific raw material ratios and process treatments, the prepared mildew-proof and antibacterial ultra-thin density board of the present invention has high surface bonding strength, static bending strength and elastic modulus, and can better meet the load-bearing and structural stability requirements in actual use.

[0029] 2. The present invention adopts a specific combination of mildew-proof and antibacterial agents, effectively improving the antibacterial and mildew-proof performance of the density board, enabling it to maintain good hygiene conditions even in environments prone to mildew and bacteria growth such as humid environments, and extending its service life.

[0030] 3. By adding specific additives during the preparation process of melamine urea formaldehyde resin, the present invention reduces the content of free formaldehyde, while increasing the solid content, viscosity, density and heat resistance of the resin, making it more suitable for the production of density boards and reducing the potential harm to the environment and human health.

[0031] 4. The entire preparation process of the present invention is reasonable in process, simple to operate, easy to control and scale up production, can effectively reduce production costs, improve production efficiency, and has good industrial application prospects. Specific Embodiments

[0032] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with specific embodiments.

[0033] Example 1:

[0034] A mildew-proof and antibacterial ultra-thin density board, comprising the following preparation steps:

[0035] S1: Crush 50 g of attapulgite clay, finely grind it, sieve it through a 200-mesh sieve, put the sieved attapulgite clay powder into a 0.7 mol / L HCl solution for acid treatment, stir for 4 h, filter to remove the acid solution, and filter and wash to obtain the acid-treated attapulgite clay powder;

[0036] S2: Prepare the acid-treated attapulgite clay powder into a slurry with a mass fraction of 5%, with an inlet temperature of 210 °C, an outlet temperature of 100 °C, an air flow pressure of 0.3 MPa, and a feeding speed of 4 mL / min. Spray-dry the slurry, place it in an oven at 250 °C for 2.5 h, and cool to obtain attapulgite clay fine powder;

[0037] S3: Mix 2 g of attapulgite clay fine powder with stearic acid, add it to a high-speed mixer, stir at a speed of 1800 rpm for 35 min to obtain modified attapulgite clay fine powder;

[0038] S4: Heat 100 g of formaldehyde to 45 °C, adjust the pH to 8, add 30 g of urea a and 5 g of melamine a, heat to 85 °C, adjust the pH to 5.2, stir and react for 35 min, add 14 g of urea b and 2.5 g of melamine b, cool to 80 °C, adjust the pH to 6.5, stir and react for 25 min, add 1.2 g of nano-titanium dioxide, maintain the temperature at 62.5 °C, stir for 12.5 min, add 8 g of urea c and 4 g of lignin, heat to 70 °C, adjust the pH to 7.5, stir and react for 15 min, add 7.5 g of polydiphenylmethane diisocyanate and 0.5 g of curing agent NH 4 Cl, stir evenly to obtain melamine urea formaldehyde resin;

[0039] S5: Put 810 g of wood fiber into 0.90 mol / L NaOH solution for alkali treatment, soak for 2.5 h, add the alkali-treated wood fiber to 13000 mL of 0.2 mol / L CaCl 2 solution, stir for 1.5 h, add 13000 mL of 0.2 mol / L NaOH solution, add 43 g of modified attapulgite clay fine powder, stir at 45 °C for 1.5 h, filter, wash and dry to obtain modified wood fiber composite material, and control the water content of the modified wood fiber composite material at 14%;

[0040] S6 Add 125 g of melamine urea formaldehyde resin, 4 g of 3-ureidopropyltriethoxysilane, 0.5 g of cetyltrimethylammonium bromide, and 2 g of N,N-dimethyldidecylammonium chloride to the internal mixer, premix at 77 °C for 4 min, the stirring speed is 40 rpm, keep the stirring speed unchanged, add 15 g of high-calcium fly ash fine powder and 800 g of modified wood fiber composite material, heat to 105 °C, mix for 8 min to obtain a uniformly mixed composite material for anti-mildew and antibacterial ultra-thin density board. Lay the composite material for anti-mildew and antibacterial ultra-thin density board on the forming board blank, and hot press it. The hot press pressure is 12 MPa, the hot press temperature is 180 °C, and the hot press time is 5 min to obtain the formed board blank. Trim the board to obtain an anti-mildew and antibacterial ultra-thin density board with a thickness of 1.2 mm.

[0041] Example 2:

[0042] An anti-mildew and antibacterial ultra-thin density board, comprising the following preparation steps:

[0043] S1: Crush and finely grind 45 g of attapulgite clay, pass through a 200-mesh sieve, put the sieved attapulgite clay powder into 0.6 mol / L HCl solution for acid treatment, stir for 3 h, filter to remove the acid solution, and filter and wash to obtain acid-treated attapulgite clay powder;

[0044] S2: Prepare the acid-treated attapulgite clay powder into a slurry with a mass fraction of 5% by adding water. The inlet temperature is 200 °C, the outlet temperature is 90 °C, the gas flow pressure is 0.2 MPa, and the feeding rate is 3 mL / min. Spray-dry the slurry, place it in an oven at 250 °C for 2 h, and cool to obtain attapulgite clay fine powder;

[0045] S3: Mix 1.5 g of stearic acid with the attapulgite clay fine powder, add it to a high-speed mixer, stir at a speed of 1500 rpm for 30 min to obtain modified attapulgite clay fine powder;

[0046] S4: Add 100 g of formaldehyde to a three-necked flask, heat up to 45 °C, adjust the pH to 7.5, add 28 g of urea a and 3 g of melamine a, heat up to 85 °C, adjust the pH to 5, stir and react for 30 min, add 12 g of urea b and 1.5 g of melamine b, cool down to 80 °C, adjust the pH to 6, stir and react for 20 min, add 0.5 g of nano-titanium dioxide, maintain the temperature at 60 °C, stir for 10 min, add 7 g of urea c and 3 g of lignin, heat up to 70 °C, adjust the pH to 7, stir and react for 10 min, add 6 g of polydiphenylmethane diisocyanate and 0.4 g of curing agent NH 4 Cl, stir evenly to obtain melamine-urea formaldehyde resin.

[0047] S5: Put 750 g of wood fiber into 0.8 mol / L NaOH solution for alkali treatment, soak for 2 h, add the alkali-treated wood fiber to 10500 mL of 0.2 mol / L CaCl 2 solution, stir for 1 h, add 10500 mL of 0.2 mol / L NaOH solution, add 40 g of modified attapulgite clay fine powder, stir at 40 °C for 1 h, filter, wash and dry to obtain modified wood fiber composite material, and control the water content of the modified wood fiber composite material at 12%;

[0048] S6: Add 100 g of melamine-urea formaldehyde resin, 3 g of 3-ureidopropyltriethoxysilane, 0.4 g of cetyltrimethylammonium bromide, and 1.6 g of N,N-dimethyldidecylammonium chloride to a mixer, premix at 75 °C for 4 min, stir at a speed of 45 rpm, keep the stirring speed unchanged, add 10 g of high-calcium fly ash fine powder and 750 g of modified wood fiber composite material, heat up to 110 °C, mix for 8 min to obtain a uniformly mixed composite material for anti-mildew and antibacterial ultra-thin density board. Lay the composite material for anti-mildew and antibacterial ultra-thin density board on a forming board embryo, and hot-press it. The hot-pressing pressure is 12 MPa, the hot-pressing temperature is 160 °C, and the hot-pressing time is 4 min to obtain a formed board embryo. Trim the board to obtain an anti-mildew and antibacterial ultra-thin density board with a thickness of 1.2 mm.

[0049] Example 3:

[0050] A mildew-proof and antibacterial ultra-thin density board, comprising the following preparation steps:

[0051] S1: Crush and finely grind 56 g of attapulgite clay, pass it through a 200-mesh sieve, put the sieved attapulgite clay powder into a 0.8 mol / L HCl solution for acid treatment, stir for 5 h, filter to remove the acid solution, and filter and wash until the pH value of the filtrate is 7.5 to obtain acid-treated attapulgite clay powder;

[0052] S2: Prepare the treated attapulgite clay powder into a slurry with a mass fraction of 5%, with an inlet temperature of 220 °C, an outlet temperature of 110 °C, an air flow pressure of 0.4 MPa, and a feeding speed of 5 mL / min. Spray-dry the slurry, place it in an oven at 250 °C for 3 h, and cool to obtain attapulgite clay fine powder;

[0053] S3: Mix the attapulgite clay fine powder and 3.3 g of stearic acid, add them to a high-speed mixer, stir at a speed of 2000 rpm for 40 min to obtain modified attapulgite clay fine powder;

[0054] S4: Add 100 g of formaldehyde to a three-necked flask, heat up to 45 °C, adjust the pH to 8.5, add 30 g of urea a and 6 g of melamine a, heat up to 85 °C, adjust the pH to 5.5, stir and react for 40 min, add 15 g of urea b and 3 g of melamine b, cool down to 80 °C, adjust the pH to 7, stir and react for 30 min, add 2 g of nano-titanium dioxide, maintain the temperature at 65 °C, stir for 15 min, add 10 g of urea c and 5 g of lignin, heat up to 70 °C, adjust the pH to 8, stir and react for 20 min, add 10.5 g of polydiphenylmethane diisocyanate and 0.6 g of curing agent NH 4 Cl to stir evenly to obtain melamine urea formaldehyde resin;

[0055] S5: Put 870 g of wood fiber into a 1.0 mol / L NaOH solution for alkali treatment, soak for 3 h, add the alkali-treated wood fiber to 13900 mL of 0.2 mol / L CaCl 2 solution, stir for 2 h, add 13900 mL of 0.2 mol / L NaOH solution, add 50 g of modified attapulgite clay fine powder, stir at 50 °C for 2 h, filter, wash, and dry to obtain a modified wood fiber composite material, and control the water content of the modified wood fiber composite material at 15%;

[0056] S6: Add 150 g of melamine urea formaldehyde resin, 5 g of 3-ureidopropyltriethoxysilane, 0.6 g of cetyltrimethylammonium bromide, and 2.4 g of N,N-dimethyldidecylammonium chloride into a mixer. Premix at 80 °C for 3 min with a stirring speed of 40 rpm. Keep the stirring speed unchanged, add 20 g of high-calcium fly ash fine powder and 870 g of modified wood fiber composite, heat up to 105 °C, and mix for 10 min to obtain a uniformly mixed composite material for a mildew and antibacterial ultra-thin density board. Lay the composite material for the mildew and antibacterial ultra-thin density board on a forming board blank, and perform hot pressing. The hot pressing pressure is 12 MPa, the hot pressing temperature is 200 °C, and the hot pressing time is 6 min to obtain a formed board blank. Trim the board to obtain a mildew and antibacterial ultra-thin density board with a thickness of 1.2 mm.

[0057] Comparative Example 1:

[0058] Compared with Example 1, stearic acid was not added in the preparation process of S1 in this comparative example, and the remaining steps and parameters were the same. This comparative example will not be repeated here. Finally, a mildew and antibacterial ultra-thin density board was obtained.

[0059] Comparative Example 2:

[0060] Compared with Example 1, nano-titanium dioxide was not added in the preparation process of S1 in this comparative example, and the remaining steps and parameters were the same. This comparative example will not be repeated here. Finally, a mildew and antibacterial ultra-thin density board was obtained.

[0061] Comparative Example 3:

[0062] Compared with Example 1, lignin was not added in the preparation process of S1 in this comparative example, and the remaining steps and parameters were the same. This comparative example will not be repeated here. Finally, a mildew and antibacterial ultra-thin density board was obtained.

[0063] Comparative Example 4:

[0064] Compared with Example 1, only "5 g of melamine a, 2.5 g of melamine b" was replaced with "5 g of urea a, 2.5 g of urea b" in this comparative example, and the remaining steps and parameters were the same. This comparative example will not be repeated here. Finally, a mildew and antibacterial ultra-thin density board was obtained.

[0065] Comparative Example 5:

[0066] Compared with Example 1, only "13000 mL of 0.2 mol / L NaOH solution" was replaced with "13000 mL of deionized water" in this comparative example, and the remaining steps and parameters were the same. This comparative example will not be repeated here. Finally, a mildew and antibacterial ultra-thin density board was obtained.

[0067] Comparative Example 6:

[0068] This comparative example is the same as Example 1 except that "5 g of cetyltrimethylammonium bromide" is replaced with "5 g of N,N-dimethyldidecylammonium chloride". The remaining steps and parameters are the same, so this comparative example will not be repeated here. Finally, a mildew-proof and antibacterial ultra-thin density board is obtained.

[0069] Comparative Example 7:

[0070] This comparative example is the same as Example 1 except that diphenylmethane diisocyanate is not added during the preparation process of S4. The remaining steps and parameters are the same, so this comparative example will not be repeated here. Finally, a mildew-proof and antibacterial ultra-thin density board is obtained.

[0071] Comparative Example 8:

[0072] This comparative example is the same as Example 1 except that fine high-calcium fly ash powder is not added during the preparation process of S6. The remaining steps and parameters are the same, so this comparative example will not be repeated here. Finally, a mildew-proof and antibacterial ultra-thin density board is obtained.

[0073] Performance test:

[0074] Referring to Q / SLMY-01-2016 "Ultra-thin High-density Fiberboard", the mildew-proof and antibacterial ultra-thin density boards prepared in Examples 1-3 and Comparative Examples 1-4 were tested. The antibacterial and mildew-proof effects of the density boards were determined according to the method described in JC / T2039-2010 "Antibacterial and Mildew-proof Wood Decorative Boards". Staphylococcus aureus AS1.89 and Aspergillus niger AS3.3928 were selected as the test strains, and the initial concentration of the mixed bacterial solution of Staphylococcus aureus and Aspergillus niger was 5.0×10 5 cfu / mL, and the antibacterial rate (%) was measured. The detailed results are shown in Table 1.

[0075] Table 1

[0076]

[0077]

[0078] The performance of the melamine urea formaldehyde resins prepared in Examples 1-3, Comparative Examples 2-4 and Comparative Example 7 was tested:

[0079] The solid content was determined with reference to GB / T14074—2017 "Test Methods for Adhesives and Resins for Wood Industry";

[0080] Viscosity: Measured with a No. 4 cup and expressed in seconds;

[0081] Density: Determined with reference to GB / T14074—2017;

[0082] Free formaldehyde content: The free formaldehyde content of the adhesive was determined by the hydrochloric acid titration method. The specific operation is as follows: Add about 1 g of the adhesive to a 250 mL conical flask, add 5 mL of anhydrous ethanol, and mix well in an ice-water bath. 25 mL of Na 2 SO 3 solution (mass fraction 15%) and 25 mL of hydrochloric acid solution (0.1 mol / L) were added. After mixing well in the ice-water bath, 7 drops of thymolphthalein indicator were added, and then titrated with 0.1 mol / L sodium hydroxide standard solution until it turned blue, and the consumed volume was recorded. The blank test was the same as the above steps except that no adhesive was added. The determination was carried out in parallel twice, and the arithmetic mean of the two determination results was taken. The calculation formula for the free formaldehyde content is as follows:

[0083] In the formula: F - free formaldehyde content, expressed as a percentage (%);

[0084] V 0 - volume of sodium hydroxide standard solution consumed in the blank, mL;

[0085] V 1 - volume of sodium hydroxide standard solution consumed by the sample, mL;

[0086] C - concentration of sodium hydroxide standard solution, mol / L;

[0087] m 1 - mass of the sample, g. The detailed results are shown in Table 2.

[0088] Table 2

[0089]

[0090] Data analysis:

[0091] As can be seen from Table 1, the anti-mold and antibacterial ultra-thin density board prepared by the present invention has a high density, surface bonding strength, static bending strength, elastic modulus, and antibacterial rate. The present invention uses wood fiber as the main base material of the density board to provide mechanical strength and structural support. The wood fiber is treated with alkali, which can remove part of the lignin and hemicellulose, improve the flexibility and reactivity of the fiber, and at the same time increase the number of hydroxyl groups on the fiber surface, providing more active sites for the subsequent cross-linking reaction.

[0092] Attapulgite clay fine powder has a unique needle-like or fibrous structure, which can fill the gaps between wood fibers, increasing the contact area and bonding force between fibers. Attapulgite clay fine powder has a large specific surface area and porous structure, which can absorb part of the moisture in the adhesive, thereby increasing the solid content of the adhesive, increasing the viscosity of the adhesive, and enabling it to adhere and penetrate better between fibers. At the same time, attapulgite clay can adsorb and fix the antibacterial agent, making it evenly distributed in the density board. This synergistic effect can improve the utilization efficiency of the antibacterial agent and enhance the antibacterial performance of the density board. The mildew and antibacterial agent is composed of cetyltrimethylammonium bromide and N,N-dimethyldidecylammonium chloride. Both cetyltrimethylammonium bromide and N,N-dimethyldidecylammonium chloride are cationic surfactants, and their cationic groups can adsorb on the cell walls of bacteria and molds, destroying the integrity of the cell walls and causing the leakage of cell contents, thereby inhibiting the growth of microorganisms. In addition, attapulgite clay and nano-titanium dioxide have a synergistic effect. Nano-titanium dioxide can generate hydroxyl radicals and reactive oxygen species under light conditions, destroying the cell walls of bacteria and molds, thereby enhancing the antibacterial and mildew-proof effect of the density board. The porous structure of attapulgite clay provides more adsorption sites for nano-titanium dioxide, making it evenly distributed in the board and improving the utilization efficiency of the antibacterial agent.

[0093] In the process of preparing the composite material for the mildew and antibacterial ultra-thin density board, the modified attapulgite clay fine powder is surface-modified by acid treatment and stearic acid. The surface properties of the attapulgite clay fine powder are improved to prevent the aggregation of the attapulgite clay fine powder. In addition, the stearic acid in the modified attapulgite clay fine powder reacts with CaCl 2 solution and NaOH in S3 to form calcium stearate, which further prevents the aggregation of the modified attapulgite clay fine powder during the preparation process and can also act as a dispersant, helping the attapulgite clay fine powder, wood fibers, and melamine urea formaldehyde resin to be mixed more evenly. On this basis, 3-ureidopropyltriethoxysilane is added, which undergoes a condensation reaction with the hydroxyl groups on the surface of attapulgite clay and wood fibers, reducing the surface polarity of the clay and wood fibers, thereby enhancing their compatibility with the resin. At the same time, the ureido group of 3-ureidopropyltriethoxysilane undergoes a condensation reaction with the hydroxymethyl group in the resin to form stable covalent bonds, forming a three-dimensional cross-linked network. High-calcium fly ash contains a large amount of aluminosilicate and calcium oxide, which will react with water to form calcium hydroxide during the hydration process, and further react with aluminosilicate to form calcium silicate hydrate, which can fill the pores inside the composite material, increasing the density of the composite material, thereby improving the overall performance of the composite material.

[0094] As can be seen from Table 2, the properties of melamine urea formaldehyde resin are improved by adding melamine, nano-titanium dioxide, polyphenylmethane diisocyanate and lignin, reducing the content of free formaldehyde and increasing the solid content, viscosity, density and heat resistance. Among them, the amino group of melamine can react with formaldehyde to form hydroxymethyl derivatives, and these derivatives further react with urea to form a stable network structure, thus reducing the release of free formaldehyde; nano-titanium dioxide significantly reduces the release of free formaldehyde in melamine urea formaldehyde resin by adsorbing and fixing free formaldehyde. Polyphenylmethane diisocyanate, whose isocyanate group can crosslink with the hydroxyl groups in the resin, significantly increases the solid content, viscosity and density of the resin; lignin has a porous structure and abundant functional groups, which can adsorb formaldehyde, thus reducing the content of free formaldehyde. Secondly, the addition of lignin can increase the solid content and viscosity of the resin, making it better adhere to and penetrate between wood fibers, thereby improving the overall performance of the material.

[0095] Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is exemplary only and is not intended to imply that the scope of the invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, which are not provided in detail for the sake of brevity.

[0096] The present invention aims to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A mildew-proof and antibacterial ultra-thin density board, characterized in that: The invention is prepared from the following components by weight: 75-87 parts of wood fiber, 4-5 parts of modified attapulgite clay powder, 10-15 parts of melamine urea-formaldehyde resin, 1-2 parts of high-calcium fly ash powder, 0.3-0.5 parts of silane coupling agent and 0.2-0.3 parts of mildew and antibacterial agent.

2. The mildew-proof and antibacterial ultra-thin density board according to claim 1, characterized in that: The preparation method of the modified attapulgite clay fine powder comprises the following steps: crushing, finely grinding and sieving the attapulgite clay, then subjecting the attapulgite clay to acid treatment, filtering and adding water to prepare a slurry, spray drying and high-temperature drying the slurry to obtain the attapulgite clay fine powder, adding stearic acid after cooling, and stirring at high speed to obtain the modified attapulgite clay fine powder.

3. The mildew-proof and antibacterial ultra-thin density board according to claim 1, characterized in that: The mildew and antibacterial agent is composed of hexadecyltrimethylammonium bromide and N,N-dimethyldidecylammonium chloride, and the mass ratio of hexadecyltrimethylammonium bromide to N,N-dimethyldidecylammonium chloride is 1:3-5.

4. The mildew-proof and antibacterial ultra-thin density board according to claim 2, characterized in that: The mass ratio of the attapulgite clay to stearic acid is 100:3-5.

5. The mildew-proof and antibacterial ultra-thin density board according to claim 1, characterized in that: The preparation method of the melamine urea-formaldehyde resin comprises the following steps: first, adding formaldehyde, urea a and melamine a to react; second, adding urea b and melamine b to continue the reaction; finally, adding nano titanium dioxide, urea c and lignin to complete the reaction, adding polydiphenylmethane diisocyanate and a curing agent, and stirring evenly to obtain the melamine urea-formaldehyde resin.

6. The mildew-proof and antibacterial ultra-thin density board according to claim 5, characterized in that: The mass ratio of the formaldehyde, urea a, urea b, urea c, melamine a, melamine b, nano titanium dioxide, lignin, polydiphenylmethane diisocyanate and curing agent is 100:28-30:12-15:7-10:3-6:1.5-3:0.5-2.0:3-5:6.0-10.5:0.4-0.

6.

7. The mildew-proof and antibacterial ultra-thin density board according to claim 5, characterized in that: The urea a, urea b, and urea c all refer to the same urea substance; the melamine a and melamine b all refer to the same melamine substance.

8. A method for preparing the mildew-proof and antibacterial ultra-thin density board according to any one of claims 1 to 7, characterized in that: The method comprises the following preparation steps: Step S1: After the wood fiber is subjected to alkali treatment, a CaCl2 solution is added, and then a NaOH solution and modified attapulgite clay fine powder are added to obtain a modified wood fiber composite material; Step S2: Evenly mix melamine urea-formaldehyde resin, high calcium fly ash powder, silane coupling agent, mildew and antibacterial agent, and modified wood fiber composite material, lay out the formed board blank, hot press and trim the edges to obtain mildew and antibacterial ultra-thin density board.

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