A formaldehyde-free mold-proof gypsum board with a composite waterproof system and a preparation method thereof

Abstract

The present application relates to the field of gypsum board preparation, and discloses a formaldehyde-free mildew-proof gypsum board with a composite waterproof system and a preparation method thereof.The composition of the gypsum board core comprises, by mass fraction, 100 parts of building gypsum powder, 0.02-0.6 parts of waterproof agent, 0.1-0.3 parts of glass fiber, 0.01-0.23 parts of formaldehyde-free agent, 0.01-0.15 parts of antibacterial mildew-proof agent, 0.2-0.4 parts of modified starch, 0.13-0.15 parts of adjusting agent, 0.02-0.06 parts of foaming agent, 0.2-0.3 parts of water reducing agent, 0.2-0.6 parts of coagulant, and 65-75 parts of water.The waterproof agent is composed of PO425 cement and hydrogen-containing silicone oil, the cement fills the air holes in the network structure of the gypsum slurry body, and the hydrogen-containing silicone oil forms a waterproof film on the surface of the gypsum core substrate, and the two together form an inorganic-organic composite waterproof structure.The gypsum board core provided by the present application has an inorganic-organic composite waterproof structure, which not only provides sufficient waterproof performance, but also encloses the formaldehyde-free agent and the antibacterial mildew-proof agent inside the core, thereby inhibiting the migration and loss of functional additives.

Description

Technical Field

[0001] This invention relates to the field of gypsum board preparation technology, specifically to a formaldehyde-free and mildew-resistant gypsum board with a composite waterproof system and its preparation method. Background Technology

[0002] With increasing emphasis on environmental protection and health, the demand for functional gypsum boards is growing. These boards are required to regulate indoor humidity, remove formaldehyde, prevent mold, and resist moisture. Formaldehyde can be released from various building materials and furniture, making it one of the major pollutants in home renovations in my country.

[0003] A formaldehyde-removing gypsum board and its preparation method (publication number CN109956728A) are disclosed, comprising a mixture of formaldehyde adsorption material prepared by a specific method, polypeptides, high molecular weight amines, gum arabic powder, and phosphates. This formaldehyde-removing gypsum board can rapidly capture and decompose indoor formaldehyde, thereby effectively reducing indoor formaldehyde concentration.

[0004] However, during long-term use, due to the loose and porous nature of gypsum board, it often has hygroscopic properties. Formaldehyde adsorbent materials, phosphates, and other materials are easily released due to moisture absorption or surface condensation, leading to rapid functional degradation. At the same time, some formaldehyde removers are prone to desorption after being saturated, causing secondary release and secondary pollution. Summary of the Invention

[0005] The purpose of this invention is to provide a formaldehyde-free and mildew-proof gypsum board with a composite waterproof system and its preparation method, so as to solve the technical problems in the prior art where gypsum board is prone to moisture absorption, leading to the precipitation of additives and the easy desorption of aldehydes after saturation.

[0006] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution:

[0007] A formaldehyde-removing and mildew-resistant gypsum board with a composite waterproof system, by weight, comprises the following core formulation: 100 parts building gypsum powder, 0.02-0.6 parts waterproofing agent, 0.1-0.3 parts glass fiber, 0.01-0.23 parts formaldehyde-removing agent, 0.01-0.15 parts antibacterial and mildew-resistant agent, 0.2-0.4 parts modified starch, 0.13-0.15 parts modifier, 0.02-0.06 parts foaming agent, 0.2-0.3 parts water-reducing agent, 0.2-0.6 parts accelerator, and 65-75 parts water.

[0008] The waterproofing agent includes cement and hydrogen-containing silicone oil;

[0009] The cement content is 0.01-0.3 parts; the hydrogen-containing silicone oil content is 0.01-0.3 parts;

[0010] The cement is used to fill the gypsum slurry network structure to block the pores in the gypsum and reduce the water absorption of the gypsum board. At the same time, the hydrogen-containing silicone oil forms a waterproof film on the surface of the gypsum core substrate. The waterproof film and the blocked pores together form an inorganic-organic composite waterproof structure.

[0011] The inorganic-organic composite waterproof structure encapsulates the antibacterial and mildew-proof agents and the formaldehyde-removing agent within the gypsum board, thereby reducing the migration rate of the antibacterial and mildew-proof agents and the formaldehyde-removing agent, and ensuring the efficient triggering of the formaldehyde-removing reaction and the antibacterial reaction.

[0012] Furthermore, the antibacterial and antifungal agent is obtained by combining an antifungal agent and a bactericide.

[0013] Furthermore, the ratio of the antifungal agent to the bactericide is 1:2 by mass.

[0014] Furthermore, the formaldehyde purifier comprises amino acids and hyperbranched polyamides, wherein the amino acids and hyperbranched polyamides are used to react with formaldehyde to degrade formaldehyde and generate non-toxic and stable products.

[0015] Furthermore, the ratio of the amino acid to the hyperbranched polyamide is 5:1 by mass.

[0016] Furthermore, the modifier is a compound of boric acid and tartaric acid;

[0017] The ratio of boric acid to tartaric acid by mass is 3:1.

[0018] Furthermore, the water-reducing agent is a naphthalene-based low-sodium water-reducing agent;

[0019] The foaming agent is sodium dodecyl sulfate;

[0020] The cement is PO425 cement.

[0021] Furthermore, the pH of the water is 7-8.

[0022] To address the aforementioned technical problems, the present invention further provides the following technical solution:

[0023] A method for preparing formaldehyde-free and mildew-resistant gypsum board with a composite waterproof system includes the following steps:

[0024] S100. Modified starch and accelerator are ground in a ball mill and then mixed evenly with building gypsum powder, glass fiber and cement through a mixing awl before entering the mixer.

[0025] S200: Formaldehyde remover, hydrogen-containing silicone oil, antibacterial and mildew-preventing agent, modifier, water-reducing agent, and water are thoroughly mixed and then fed into the mixer through a wet material system to produce gypsum slurry.

[0026] S300: The foaming agent is generated into uniform foam through the emulsification system and injected into the discharge cylinder of the mixer. It is then fully mixed with the gypsum slurry, sprayed onto the facing paper, shaped, and dried to obtain the finished gypsum board.

[0027] Furthermore, the drying process includes sequentially performing drying at four temperatures: 125℃-130℃, 120℃-125℃, 112℃-117℃, and 92℃-100℃, with a drying time of 60-70 minutes.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] This invention constructs an inorganic-organic composite waterproof structure by filling the pores of the gypsum skeleton with inorganic cement and simultaneously forming a film on the surface with organic hydrogen-containing silicone oil. This not only effectively reduces the water absorption rate and surface water absorption of the gypsum board, improving its moisture resistance, but also stably seals antibacterial and mildew-proof agents and formaldehyde-removing agents within the core layer of the gypsum board. This effectively inhibits the migration and precipitation of functional additives with moisture, reduces the migration rate of antibacterial and mildew-proof agents and formaldehyde-removing agents, and significantly improves the long-lasting antibacterial and mildew-proof performance and the durability of formaldehyde removal. Attached Figure Description

[0030] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the preparation method provided in the embodiments of this application.

[0032] Figure 2 The image shown is a low-magnification scanning electron microscope image of Example 1 of this application, ×100, scale bar 500μm.

[0033] Figure 3 The image shows the crystal arrangement morphology of medium magnification crystals provided in Example 1 of this application, ×2000, scale bar 20.0 μm.

[0034] Figure 4 This is a high-magnification crystal morphology image provided in Example 1 of this application, ×5000, scale bar 10.0 μm.

[0035] Figure 5 This is a fine structural morphology image of the ultra-high magnification crystal surface provided in Example 1 of this application, ×10000, scale bar 5.00μm. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] The present invention provides a formaldehyde-free and mildew-proof gypsum board with a composite waterproof system, comprising an upper protective paper, a lower protective paper, and a core sandwiched between the upper and lower protective papers.

[0038] The core of the board is formed by mixing, molding, and drying architectural gypsum powder, waterproofing agent, glass fiber, formaldehyde remover, antibacterial and mildew-proof agent, modified starch, modifier, foaming agent, water-reducing agent, accelerator and water.

[0039] The waterproofing agent includes cement and hydrogen-containing silicone oil. The cement is preferably PO425 cement, with a content of 0.01-0.3 parts; the content of hydrogen-containing silicone oil is 0.01-0.3 parts.

[0040] In the microstructure of the gypsum core layer 3, cement filler particles fill the gypsum slurry network structure, blocking the pores in the gypsum to reduce the water absorption of the gypsum board; at the same time, hydrogen-containing silicone oil forms a hydrogen-containing silicone oil waterproof film on the surface of the gypsum core layer, and this waterproof film together with the blocked pores forms an inorganic-organic composite waterproof structure.

[0041] Hydrogen-containing silicone oil, under the action of a metal catalyst, can cross-link at appropriate temperatures, forming a waterproof film on the surface of the gypsum core substrate. Cement (especially PO425 cement), a cementing material, possesses excellent bonding properties and chemical stability. It can fill the network structure of the gypsum slurry, blocking the pores in the gypsum and thus preventing it from being affected by impurities, thereby providing a waterproof effect. The combination of these two substances applied to gypsum board can significantly improve its moisture and water resistance.

[0042] This invention constructs an inorganic-organic composite waterproof structure through the synergistic construction of inorganic cement filling the pores of the gypsum skeleton and organic hydrogen-containing silicone oil forming a film on the surface. This stabilizes and seals antibacterial and antifungal agents and formaldehyde removers within the core layer of the gypsum board. Cement, acting as a cementing material, fills the gypsum slurry network structure to block pores, while the hydrogen-containing silicone oil forms a waterproof film on the surface of the gypsum core substrate, effectively reducing the water absorption rate and surface water absorption of the gypsum board and improving its moisture resistance.

[0043] The inorganic-organic composite waterproof structure encapsulates the formaldehyde removal agent particles and antibacterial and mildew-proof agent particles within the gypsum board, effectively inhibiting the migration and precipitation of functional additives to the surface with moisture. This reduces the migration rate of the formaldehyde removal agent and antibacterial and mildew-proof agent, ensuring the efficient triggering of the formaldehyde removal and antibacterial reactions, and significantly improving the long-lasting antibacterial and mildew-proof performance and the durability of formaldehyde removal.

[0044] On the other hand, the waterproof structure reduces the equilibrium moisture content of the gypsum board from the source, making the board less prone to moisture absorption. The organic components inside the substrate are less prone to hydrolysis, and the dry environment itself inhibits the growth of hygrophilous molds, which greatly reduces the workload of antibacterial and antifungal agents and formaldehyde removers. Even with a small amount added, a good level of protection can be achieved.

[0045] In addition, the use of naphthalene-based low-sodium water-reducing agent effectively controls the chloride ion content, avoiding the adverse effects of chloride ions on the performance of gypsum board; the use of PO425 cement has excellent bonding performance and chemical stability, and is not affected by gypsum impurities, further ensuring the stability and durability of the waterproofing effect.

[0046] The formaldehyde remover consists of amino acids and hyperbranched polyamides, with a mass ratio of amino acids to hyperbranched polyamides of 5:1. Both amino acids and hyperbranched polyamides readily react with formaldehyde, degrading it, and the resulting products are non-toxic and stable.

[0047] Amino acids and hyperbranched polyamides are easily affected by water and gas, leading to their failure. Therefore, multiple waterproofing systems are particularly important.

[0048] Antibacterial and antifungal agents are obtained by compounding antifungal agents and bactericides, with a mass ratio of antifungal agent to bactericide of 1:2.

[0049] The mildew inhibitor used is FUNGIPOL®351 (Funbao Chemical).

[0050] The bactericide is a synergistic compound of OIT (for mold control), carbendazim (for long-lasting mold prevention), and diuron (for algae control). The total effective content of the three bactericides, by mass fraction, is 10%–12%, with the remainder being water.

[0051] The modifier is a mixture of boric acid and tartaric acid, with a mass ratio of boric acid to tartaric acid of 3:1.

[0052] The water-reducing agent is a naphthalene-based low-sodium water-reducing agent, with its core component being naphthalene sulfonate formaldehyde condensate. It is an anionic, non-air-entraining, high-efficiency water-reducing agent, typically appearing as a brownish-yellow powder or a brownish-brown viscous liquid. Naphthalene-based water-reducing agents have good compatibility with gypsum systems. The use of naphthalene-based low-sodium water-reducing agents effectively controls chloride ion content, thereby reducing the water absorption rate of the boards.

[0053] The foaming agent is sodium dodecyl sulfate. The pH of the water is 7-8.

[0054] Furthermore, such as Figure 1 As shown, the present invention provides a method for preparing a formaldehyde-free and mildew-resistant gypsum board with a composite waterproof system, comprising the following steps:

[0055] S100. Modified starch and accelerator are ground in a ball mill, then mixed evenly with building gypsum powder, glass fiber and cement through a mixing awl before entering the mixer.

[0056] S200: Formaldehyde remover, hydrogen-containing silicone oil, antibacterial and mildew-preventing agent, modifier, water-reducing agent, and water are thoroughly mixed and then fed into the mixer through a wet material system to produce gypsum slurry.

[0057] S300. The foaming agent is generated into uniform foam by the emulsification system and injected into the discharge cylinder of the mixer. It is fully mixed with the gypsum slurry, sprayed onto the facing paper, extruded by the forming table, solidified by the coagulation belt, cut, and then entered into the dryer for drying. The dried board is then assembled, sawed, sealed, and packaged to obtain the finished gypsum board.

[0058] The drying process is carried out sequentially at four temperatures: 125℃-130℃, 120℃-125℃, 112℃-117℃, and 92℃-100℃, with a total drying time of 60-70 minutes.

[0059] The following examples further illustrate this:

[0060] Example 1:

[0061] Raw material ratio:

[0062] 1000g building gypsum powder, 3g PO425 cement, 2g glass fiber, 2.3g formaldehyde remover, 3g hydrogen-containing silicone oil, 0.8g antibacterial and mildew-proof agent, 4g modified starch, 1.3g adjuster, 0.2g foaming agent, 3g naphthalene-based low-sodium water-reducing agent, 5g coagulant, 700g water (pH adjusted to 7-8).

[0063] The formaldehyde remover is composed of amino acids and hyperbranched polyamide in a mass ratio of 5:1; the antibacterial and antifungal agent is composed of antifungal agent and bactericide in a mass ratio of 1:2; the modifier is composed of boric acid and tartaric acid in a mass ratio of 3:1; and the foaming agent is sodium dodecyl sulfate.

[0064] Preparation steps:

[0065] (1) Dry powder pretreatment: Weigh 4g of modified starch and 5g of accelerator, and place them together in a planetary ball mill. Grind them at 300r / min for 15min to ensure thorough mixing and refinement. After grinding, add the mixed powder, 1000g of building gypsum powder, 2g of glass fiber, and 3g of PO425 cement to a horizontal mixing cutter. Stir and mix at 120r / min for 8min to ensure uniform dispersion of the dry powder components and obtain a dry mixture for later use.

[0066] (2) Preparation of wet materials: Take another beaker and weigh 700g of water. Adjust the pH to 7-8 with dilute NaOH solution or dilute H2SO4 solution. Add 2.3g of aldehyde remover, 3g of hydrogen-containing silicone oil, 0.8g of antibacterial and antifungal agent, 1.3g of adjuster, and 3g of naphthalene-based low-sodium water-reducing agent to the water in sequence. Place the beaker on a magnetic stirrer and stir at 500r / min for 10min until all components are completely dissolved or evenly dispersed to form a homogeneous wet material mixture.

[0067] (3) Slurry mixing: Transfer the dry mixture obtained in step (1) to a laboratory high-speed mixer, start stirring (speed about 600 r / min), and slowly pour the wet mixture obtained in step (2) into the mixer within 30s while stirring, and continue stirring for 60s to make the dry powder and wet material fully contact each other and form a fluid gypsum slurry.

[0068] (4) Foaming: Weigh 0.2g of sodium dodecyl sulfate and place it in the foaming agent emulsification system. Add a small amount of water (about 5g) and emulsify by high-speed shearing (3000r / min, 3min) to generate uniform and fine foam. Inject the foam into the discharge cylinder of the mixer through the pipeline. Mix it with the above gypsum slurry by spiral stirring for about 20s during the discharge process to make the foam evenly distributed in the slurry.

[0069] (5) Molding: The well-mixed foamed slurry is evenly sprayed onto the lower protective paper through the outlet. The thickness of the slurry is controlled to be about 6mm. Then the upper protective paper is covered and the slurry is squeezed and shaped by the forming table, so that the slurry is evenly spread between the upper and lower protective papers and the wet thickness of the board is controlled to be about 12mm.

[0070] (6) Solidification and cutting: After the gypsum board strip is formed, it is left to solidify on the solidification belt for about 5 minutes. After the board hardens to a certain strength, it is cut according to the set size (1200mm×2400mm is selected in this embodiment).

[0071] (7) Drying: The cut boards are placed in a forced-air drying oven for segmented drying. The drying regime is as follows: first stage: 125℃-130℃ for 15 min; second stage: 120℃-125℃ for 15 min; third stage: 112℃-117℃ for 20 min; fourth stage: 92℃-100℃ for 15 min, with a total drying time of approximately 65 min. During the drying process, care should be taken to maintain a smooth transition between each temperature segment to avoid sudden temperature changes that could cause the boards to crack.

[0072] (8) Post-processing: After drying, the boards are taken out and naturally cooled to room temperature. They are then assembled, sawed (trimmed to standard size), sealed (applied with sealing agent), and packaged to obtain the finished formaldehyde-free, mildew-proof and moisture-resistant gypsum board.

[0073] The above dosages are based on the formulation of Example 1 (calculated as 100 parts of building gypsum powder corresponds to 1000g). All components are accurately weighed. The equipment parameters and time involved in the operation steps can be adjusted according to the actual laboratory conditions. If further simulation of a pilot production line is required, the dosage of each raw material can be scaled up by multiples (such as 10 times or 100 times), and the mixing equipment volume and stirring parameters can be adjusted accordingly.

[0074] The scanning electron microscope image of Example 1 is as follows: Figures 2 to 5 As shown.

[0075] like Figure 2 As shown, under 100x scanning electron microscopy, the core of this water-resistant gypsum board exhibits a typical porous skeletal structure of foamed gypsum. Numerous spherical foamed pores are distributed within the core, with pore diameters mostly in the hundreds of micrometers range. Most pores are independent closed-cell structures, while some exhibit slight wall cracking and partial connectivity. The spherical pores are connected by a hydrated gypsum solid matrix, forming a continuous supporting framework. Numerous tiny capillary pores are diffusely distributed within the gypsum matrix. It is evident that the closed-cell foam structure effectively reduces the bulk density of the board, giving it lightweight and sound-insulating properties. The density of the matrix and the proportion of open pores directly affect the overall water absorption and permeation rate of the board.

[0076] like Figure 3 As shown, the solid matrix region of gypsum was magnified to 2000x for observation. The main hydration products of the core were elongated, plate-like, and needle-like dihydrate gypsum crystals. The crystals were randomly interlocked and interwoven, forming a three-dimensional rigid network framework that provided the gypsum board with compressive and flexural strength. Flocculent and clustered modified substances were visible on the crystal surface and between the crystal gaps, which could be water-resistant modified components added to the formulation.

[0077] like Figure 4As shown, magnified 5000 times, the dihydrate gypsum crystals are regular in shape, with flat end faces and good crystal development; the crystals are stacked and intertwined to form a stable spatial structure. The water-resistant modifier, in the form of a thin film and fine particles, coats the surface of the gypsum crystals and fills some of the intercrystalline pores, effectively preventing water molecules from directly contacting the gypsum crystals and blocking some capillary water transport channels, thus achieving hydrophobic modification of the gypsum matrix.

[0078] like Figure 5 As shown, the 10,000x high-resolution morphology reveals that the surface of the gypsum dihydrate crystals is smooth and flat. A continuous but slightly undulating hydrophobic coating is attached to the outer wall of the crystals, along with a small amount of agglomerated modified filler particles. The coating has good overall coverage, with only minor breaks and exposed areas in localized locations, corresponding to microscopic defects in the slab that indicate slight water absorption. The overall coating system is intact, and the water-resistant modified components exert an ideal interfacial hydrophobic effect.

[0079] Examples 2-3 and Comparative Examples 1-4 are further provided below. The preparation steps are the same as those in Example 1, but the components are slightly different. The differences are shown in Table 1:

[0080] Table 1

[0081]

[0082] Performance testing: The gypsum boards prepared in Examples 1-7 were tested according to GB / T9775-2008 Gypsum Board Test Method, JC / T2039-2010 Antibacterial and Mildew-resistant Wood Decorative Board Standard, and JCT-1074-2008 Indoor Air Purification Functional Coating Material Purification Performance Standard. The specific test data are shown in Table 2 below.

[0083] Table 2

[0084]

[0085] Data Analysis:

[0086] 1. Water absorption performance analysis

[0087] Comparing Example 1 (0.3 parts cement + 0.3 parts hydrogen-containing silicone oil) with Comparative Example 1 (0.3 parts hydrogen-containing silicone oil, 0 parts cement), the water absorption rate of Example 1 was 5.4%, while that of Comparative Example 1 was 12.5%. The surface water absorption of Example 1 was 145 g / m², while that of Comparative Example 1 was 196 g / m². This indicates that, with the same amount of hydrogen-containing silicone oil, adding cement can reduce the water absorption rate by approximately 7.1 percentage points and the surface water absorption by approximately 51 g / m².

[0088] Comparing Example 1 (0.3 parts cement + 0.3 parts hydrogen-containing silicone oil) and Comparative Example 4 (0.3 parts cement, 0 parts hydrogen-containing silicone oil), the water absorption rate of Example 1 was 5.4%, while that of Comparative Example 4 was 18.1%. The surface water absorption of Example 1 was 145 g / m², while that of Comparative Example 4 was 265 g / m². With the same amount of cement, adding hydrogen-containing silicone oil can reduce the water absorption rate by approximately 12.7 percentage points and the surface water absorption by approximately 120 g / m².

[0089] As can be seen from the above two comparisons, the waterproofing effect is limited when cement (Comparative Example 4, water absorption rate 18.1%) or hydrogen-containing silicone oil (Comparative Example 1, water absorption rate 12.5%) is used alone; however, when the two are used together (Example 1, water absorption rate 5.4%), the effect is not simply additive, and the water absorption rate is significantly reduced.

[0090] 2. Formaldehyde Removal Performance Analysis

[0091] Comparing Example 1 (cement + hydrogen-containing silicone oil, 0.23 parts formaldehyde remover) and Comparative Example 2 (cement + hydrogen-containing silicone oil, 0 parts formaldehyde remover), the formaldehyde purification rate of Example 1 was 97.5%, while that of Comparative Example 2 was 42.1%. The 42.1% purification rate in Comparative Example 2 stemmed from the physical adsorption of formaldehyde by the porous structure of the gypsum board itself; however, once saturated, adsorption easily desorbs, causing secondary release. Example 1, through the sealing effect of the inorganic-organic composite waterproof structure, anchored the formaldehyde remover (amino acids and hyperbranched polyamide) within the board core, preventing it from migrating and being lost with moisture, thus ensuring the continuous chemical reaction between the formaldehyde remover and formaldehyde.

[0092] Comparing the formaldehyde purification rate (97.5%) and purification effect durability (97.4%) of Example 1, the two are almost equal, indicating that the formaldehyde purification effect does not significantly decrease during long-term use. However, Comparative Example 4 (without hydrogen-containing silicone oil and without a surface waterproof membrane) has a purification rate of 94.6% and a durability of 94.9%. Although the initial purification rate is close to that of Example 1, considering its high water absorption rate of 18.1%, it is prone to loss of the formaldehyde purifying agent due to moisture migration to the surface in high-humidity environments, resulting in a significant decrease in durability during actual long-term use. The waterproof structure reduces the equilibrium moisture content of the board, preventing the hydrolysis, oxidation, and physical loss of the formaldehyde purifying agent under the action of moisture, ensuring the continuous and efficient formaldehyde purification reaction.

[0093] The purification rate of Example 1 (0.23 parts of formaldehyde remover) was 97.5%, and the purification rate of Example 2 (0.1 parts of formaldehyde remover) was 72.1%. It is evident that the formaldehyde purification rate increases with the increase in the amount of formaldehyde remover used, indicating a positive correlation between the amount of formaldehyde remover used and the purification efficiency under the protection of the composite waterproof structure. Even with a lower amount of formaldehyde remover (Example 2, 0.1 parts), the purification rate still reached 72.1%, far exceeding the 42.1% of Comparative Example 2 (without formaldehyde remover), demonstrating that the waterproof system can effectively utilize the function of the formaldehyde remover.

[0094] 3. Analysis of antibacterial and antifungal properties

[0095] Example 1 (containing 0.08 parts of anti-mold agent) had an anti-mold rating of 0, while Comparative Example 3 (without anti-mold agent) had an anti-mold rating of 3. According to the JC / T2039-2010 standard, anti-mold rating 0 is the highest level (no mold growth observed), while level 3 indicates significant mold growth. This comparison shows that simply relying on waterproofing agents to reduce water absorption (Comparative Example 3 had a water absorption rate of 5.8%, which is already at a low level) is insufficient to completely inhibit mold growth; an appropriate amount of antibacterial and anti-mold agent must be added to achieve a high level of anti-mold protection. This is because mold growth requires not only moisture but also organic matter as a nutrient source; while waterproofing agents can reduce environmental humidity, they cannot eliminate the risk of mold growth from organic components in gypsum board (such as modified starch and organic components in formaldehyde removers).

[0096] The inorganic-organic composite waterproof structure seals the antibacterial and antifungal agents within the core of the board. This reduces the risk of loss due to moisture migration, allowing the agents to maintain their inhibitory effect on mold spores within the board for an extended period. Furthermore, the waterproof structure itself lowers the equilibrium moisture content of the board, physically inhibiting the survival of hygrophilous microorganisms. This combination of physical waterproofing and chemical antifungal treatment achieves a dual protection mechanism: "waterproofing to inhibit mold, and preventing mold to kill mold."

[0097] Example 1 (0.08 parts of antifungal agent) had an antifungal level of 0, while Example 3 (0.04 parts of antifungal agent) had an antifungal level of 2. It is evident that halving the amount of antifungal agent resulted in a decrease in the antifungal level from 0 to 2, indicating that the amount of antifungal agent significantly affects the antifungal effect.

[0098] 4. Mechanical property analysis

[0099] The longitudinal flexural strength of Example 1 was 482 N, compared to 451 N for Comparative Example 1 (without cement) and 470 N for Comparative Example 4 (without hydrogen-containing silicone oil). Example 1 showed higher strength than both. This is attributed to the fact that the hydration products of PO425 cement (such as CSH gel) fill the pores between gypsum crystals, not only preventing water penetration but also enhancing the bonding strength between the gypsum crystals, thus improving the structural density and overall strength of the core. Meanwhile, the waterproof membrane formed by the hydrogen-containing silicone oil provides surface protection without weakening the matrix strength. Therefore, Example 1 achieved a simultaneous improvement in both waterproof and mechanical properties. The flexural strength of all examples significantly exceeded the requirement of ≥400 N for the corresponding thickness of the board in GB / T9775-2008.

[0100] Based on the above, we can conclude that:

[0101] PO425 cement and hydrogen-containing silicone oil have a clear synergistic effect in gypsum board waterproofing. Their waterproofing effects are complementary, and the effect is optimal when they coexist (water absorption rate reaches 5.4%).

[0102] The inorganic-organic composite waterproof structure has an "in-situ sealing" effect on formaldehyde removers and antibacterial and antifungal agents, effectively inhibiting the migration and loss of functional additives to the surface with water vapor.

[0103] The waterproofing system and the anti-mold system complement each other. The waterproofing agent reduces humidity at a physical level, while the antibacterial and anti-mold agent inhibits mold growth at a chemical level. Together, they ensure the long-term anti-mold performance of the boards in humid environments.

[0104] At the same time, PO425 cement also achieved an improvement in mechanical strength.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. All such modifications or substitutions should be covered within the protection scope of this application, and should not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application. Therefore, the protection scope of this application should be determined by the protection scope of the claims.

Claims

1. A formaldehyde-free and mildew-resistant gypsum board with a composite waterproof system, characterized in that, By weight, its core formulation includes 100 parts building gypsum powder, 0.02-0.6 parts waterproofing agent, 0.1-0.3 parts glass fiber, 0.01-0.23 parts formaldehyde remover, 0.01-0.15 parts antibacterial and mildew-proofing agent, 0.2-0.4 parts modified starch, 0.13-0.15 parts modifier, 0.02-0.06 parts foaming agent, 0.2-0.3 parts water-reducing agent, 0.2-0.6 parts accelerator, and 65-75 parts water. The waterproofing agent includes cement and hydrogen-containing silicone oil; The cement content is 0.01-0.3 parts; the hydrogen-containing silicone oil content is 0.01-0.3 parts; The cement is used to fill the gypsum slurry network structure to block the pores in the gypsum and reduce the water absorption of the gypsum board. At the same time, the hydrogen-containing silicone oil forms a waterproof film on the surface of the gypsum core substrate. The waterproof film and the blocked pores together form an inorganic-organic composite waterproof structure. The inorganic-organic composite waterproof structure encapsulates the antibacterial and mildew-proof agents and the formaldehyde-removing agent within the gypsum board, thereby reducing the migration rate of the antibacterial and mildew-proof agents and the formaldehyde-removing agent, and ensuring the efficient triggering of the formaldehyde-removing reaction and the antibacterial reaction.

2. The formaldehyde-free and mildew-resistant gypsum board with a composite waterproof system according to claim 1, characterized in that, The antibacterial and antifungal agent is obtained by combining an antifungal agent and a bactericide.

3. The formaldehyde-free and mildew-resistant gypsum board with a composite waterproof system according to claim 2, characterized in that, The ratio of the antifungal agent to the bactericide is 1:2 by mass.

4. A formaldehyde-free and mildew-resistant gypsum board with a composite waterproof system according to claim 1, characterized in that, The formaldehyde purifier comprises amino acids and hyperbranched polyamides, wherein the amino acids and hyperbranched polyamides are used to react with formaldehyde to degrade formaldehyde and generate non-toxic and stable products.

5. A formaldehyde-free and mildew-resistant gypsum board with a composite waterproof system according to claim 4, characterized in that, The ratio of the amino acid to the hyperbranched polyamide is 5:1 by mass.

6. A formaldehyde-free and mildew-resistant gypsum board with a composite waterproof system according to claim 1, characterized in that, The modifier is a compound of boric acid and tartaric acid; The ratio of boric acid to tartaric acid by mass is 3:

1.

7. A formaldehyde-free and mildew-resistant gypsum board with a composite waterproof system according to claim 1, characterized in that, The water-reducing agent is a naphthalene-based low-sodium water-reducing agent; The foaming agent is sodium dodecyl sulfate; The cement is PO425 cement.

8. A formaldehyde-free and mildew-resistant gypsum board with a composite waterproof system according to claim 1, characterized in that, The pH of the water is 7-8.

9. A method for preparing a formaldehyde-free and mildew-resistant gypsum board with a composite waterproof system as described in any one of claims 1-8, characterized in that, Includes the following steps: S100. Modified starch and accelerator are ground in a ball mill and then mixed evenly with building gypsum powder, glass fiber and cement through a mixing awl before entering the mixer. S200: Formaldehyde remover, hydrogen-containing silicone oil, antibacterial and mildew-preventing agent, modifier, water-reducing agent, and water are thoroughly mixed and then fed into the mixer through a wet material system to produce gypsum slurry. S300: The foaming agent is generated into uniform foam through the emulsification system and injected into the discharge cylinder of the mixer. It is then fully mixed with the gypsum slurry, sprayed onto the facing paper, shaped, and dried to obtain the finished gypsum board.

10. A method for preparing a formaldehyde-free and mildew-resistant gypsum board with a composite waterproof system as described in claim 9, characterized in that, The drying process is carried out sequentially at four temperatures: 125℃-130℃, 120℃-125℃, 112℃-117℃, and 92℃-100℃, with a drying time of 60-70 minutes.

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