Fire resistant type paper faced gypsum board and method of making

Abstract

This invention relates to the field of building materials technology, and discloses a fire-resistant paper-faced gypsum board and its preparation method. The gypsum board comprises a gypsum core material and a facing paper laminated to its upper and lower surfaces. The raw materials of the gypsum core material include building gypsum powder, a fire-resistant modifier, dispersed reinforcing fibers, a binder, a foaming agent, and water. The fire-resistant modifier is a mixture of nano-silica sol and silica powder, and the dispersed reinforcing fibers are alkali-free glass fibers surface-treated with a silane coupling agent. The gypsum core material has a dihydrate gypsum crystal network skeleton, with nano-silica particles filling the micropores between the crystals, silica powder dispersed on the crystal surface, and dispersed reinforcing fibers interspersed within the crystal network skeleton. The preparation method includes dry mixing, liquid mixing, initial mixing, fiber dispersion, extrusion molding, and drying steps. This invention significantly improves the fire resistance and mechanical properties of the paper-faced gypsum board by constructing a multi-scale continuous fire-resistant network and an interface anchoring system.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a fire-resistant paper-faced gypsum board and its preparation method. Background Technology

[0002] Paper-faced gypsum board is a lightweight building material made primarily of building gypsum, with appropriate additives and fiber materials. It is formed, solidified, cut, and dried under a protective paper covering. It is widely used in building partitions and ceilings. To meet the fire safety requirements of high-rise and public buildings, fire-resistant paper-faced gypsum board has become a research hotspot. Current technologies typically improve the fire resistance of the board by adding glass fibers and fire-resistant modifiers to the gypsum core material. However, existing fire-resistant paper-faced gypsum boards face the following technical challenges: the fire-resistant modifier is unevenly distributed in the gypsum core material, and nanoparticles easily agglomerate, preventing the fire-resistant modifier from forming a continuous and effective fire-resistant network between gypsum crystals. Simultaneously, the interfacial bonding strength between glass fibers and gypsum crystals is insufficient, and the fibers are easily pulled out of the gypsum matrix under high-temperature conditions, weakening the fire-resistant enhancement effect. Summary of the Invention

[0003] The purpose of this invention is to provide a fire-resistant paper-faced gypsum board and its preparation method to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a fire-resistant paper-faced gypsum board, comprising a gypsum core material and a facing paper laminated on the upper and lower surfaces of the gypsum core material, wherein the raw materials of the gypsum core material, by weight, include: 100 parts of building gypsum powder, 5-15 parts of fire-resistant modifier, 0.5-3 parts of dispersed reinforcing fiber, 0.1-1 parts of binder, 0.05-0.2 parts of foaming agent, and 60-85 parts of water; The building gypsum powder is β-hemihydrate gypsum with a specific surface area of ​​3000-4000 cm². 2 / g; The refractory modifier is a mixture of nano-silica sol and silica powder. The solid content of the nano-silica sol is 30%-50%, the particle size of the nano-silica particles is 20-100nm, and the particle size of the silica powder is 0.1-5μm. The dispersed reinforcing fiber is an alkali-free glass fiber surface-treated with a silane coupling agent, with a fiber length of 8-15 mm and a single filament diameter of 9-13 μm; The gypsum core material has a gypsum dihydrate crystal network skeleton inside, with nano-silica particles filling the micropores between the gypsum dihydrate crystals, silica powder dispersed on the surface of the gypsum dihydrate crystals, and dispersed reinforcing fibers interspersed in the gypsum dihydrate crystal network skeleton.

[0005] As a preferred embodiment of the present invention, the weight ratio of nano-silica sol to silica powder in the refractory modifier is 1:0.5-2, and the refractory modifier also contains 5%-20% aluminum hydroxide powder by weight of the total refractory modifier, the particle size of the aluminum hydroxide powder being 1-8μm. Nano-silica particles, silica powder, and aluminum hydroxide powder are distributed in a ternary particle mixed state inside the gypsum core material. The aluminum hydroxide powder is attached to the surface of the dihydrate gypsum crystals and partially embedded between the dihydrate gypsum crystals.

[0006] As a preferred embodiment of the present invention, the surface of the dispersed reinforcing fiber has a silane coupling agent treatment layer, and the adhesive is coated on the surface of the dispersed reinforcing fiber in the form of an adhesive layer outside the silane coupling agent treatment layer. The thickness of the adhesive layer is 0.5-2μm. The dispersed reinforcing fiber is connected to the surface of the gypsum dihydrate crystal through the adhesive layer, and the adhesive layer forms a gradient transition interface between the dispersed reinforcing fiber and the gypsum dihydrate crystal.

[0007] As a preferred embodiment of the present invention, the foaming agent is composed of anionic surfactant and foam stabilizer, wherein the weight ratio of anionic surfactant to foam stabilizer is 2:0.8-1.2, the anionic surfactant is at least one of sodium dodecyl sulfate or sodium dodecylbenzene sulfonate, and the foam stabilizer is silicone polyether emulsion. The gypsum core material has a spherical cavity with a diameter of 0.1-0.5 mm. The inner wall of the spherical cavity is attached with a residual shell of nano-silica particles with a thickness of 0.05-0.2 μm.

[0008] As a preferred technical solution of the present invention, the gypsum core material further contains at least one of citric acid or sodium tripolyphosphate, accounting for 0.1%-0.5% of the weight of building gypsum powder. Citric acid or sodium tripolyphosphate is attached to the surface of dihydrate gypsum crystal in the form of a molecular layer. The nano silica particles in the nano silica sol form a coordination bond structure with calcium ions on the surface of dihydrate gypsum crystal through silanol groups. Gypsum dihydrate crystals exist in the form of short columnar or massive crystals, with an aspect ratio of 1:1 to 3:1.

[0009] As a preferred embodiment of the present invention, the adhesive is composed of the following components in the following weight ratio: modified starch: phosphorylated crosslinked starch: guar gum = 1: 0.3-0.6: 0.1-0.2; The modified starch has a viscosity of 1000-5000 mPa·s, the degree of substitution of the phosphate-crosslinked starch is 0.05-0.15, and the molecular weight of guar gum is 200,000-500,000. Modified starch, phosphorylated cross-linked starch, and guar gum form a ternary interpenetrating network bonding system inside the gypsum core material. The phosphate groups of phosphorylated cross-linked starch form an ionic bond structure with the calcium ions on the surface of gypsum dihydrate crystals. The hydroxyl groups of guar gum form a hydrogen bond network with the hydroxyl groups of modified starch. Guar gum molecular chains interweave between the modified starch molecular chains.

[0010] A method for preparing fire-resistant paper-faced gypsum board includes the following steps: Step 1: Add building gypsum powder, silica powder, and binder into a dry mixing equipment and dry mix at a speed of 200-400 r / min for 3-8 minutes to obtain a dry mix. Step 2: Add water, nano silica sol, and foaming agent into a mixing container and mix at a speed of 100-300 r / min for 2-5 minutes to obtain a liquid mixture; Step 3: Add the dry mixture to the mixing container and mix with the liquid mixture. Stir at a speed of 400-600 r / min for 30-60 seconds to obtain the initial slurry. Step 4: Evenly sprinkle the dispersed reinforcing fibers into the initial mixed slurry, and continue to stir at a speed of 200-300 r / min for 15-30 seconds to ensure that the dispersed reinforcing fibers are evenly dispersed in the slurry, thus obtaining the shaped slurry; Step 5: Pour the molding slurry onto the lower protective paper, cover it with the upper protective paper, and then extrude it to form a wet gypsum board. The extrusion pressure is 0.2-0.5 MPa. Step 6: Solidify the wet gypsum board on the solidification conveyor belt for 5-15 minutes, cut it, and send it to the dryer for drying. The drying temperature is 150-250℃ and the drying time is 30-60 minutes. After the board is removed from the dryer, it is trimmed to obtain the finished fire-resistant paper-faced gypsum board.

[0011] As a preferred technical solution of the present invention, the method of spreading the dispersed reinforcing fiber in step four is as follows: the dispersed reinforcing fiber is continuously spread in a uniform thin laminar flow by using a fiber spreading device, the spreading width is matched with the width of the slurry liquid surface in the mixing container, and the spreading height is 10-30cm above the slurry liquid surface. The dispersion density of the reinforcing fibers in the molding slurry is 5-15 dispersed reinforcing fibers per cubic centimeter of slurry.

[0012] As a preferred embodiment of the present invention, the drying process in step six adopts a three-stage drying method: The first stage of drying is at a temperature of 200-250℃, a drying time of 10-20 minutes, and a wind speed of 3-5m / s on the surface of the board. The second stage of drying is at a temperature of 170-200℃, a drying time of 10-20 minutes, and a wind speed of 2-4 m / s on the surface of the board. The third stage of drying is at a temperature of 150-170℃, a drying time of 10-20 minutes, and a wind speed of 1-3m / s on the surface of the board. The moving speed of the board during the three-stage drying process is 2-5 m / min.

[0013] As a preferred embodiment of the present invention, in step three, the stirring speed of the initial mixed slurry is 500 r / min and the stirring time is 45 seconds; in step four, the stirring speed after the addition of the dispersed reinforcing fiber is 250 r / min and the stirring time is 20 seconds. The consistency of the molding slurry is in the range of 40-60mm, and the pH value of the molding slurry is controlled between 6.5 and 7.5. In step five, the extrusion molding adopts a roller extrusion method, and the gap between the upper and lower rollers is 0.5-1.0 mm smaller than the target thickness of the wet gypsum board.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention introduces a refractory modifier composed of nano-silica sol and silica powder into the gypsum core material. The nano-silica particles fill the micropores between the dihydrate gypsum crystals, and the silica powder is dispersed on the surface of the dihydrate gypsum crystals. The two construct a continuous refractory network across scales inside the gypsum core material, which effectively hinders the transfer of heat to the interior of the board, significantly improves the fire stability of the paper-faced gypsum board, and reduces the thermal conductivity of the board.

[0015] 2. In this invention, aluminum hydroxide micropowder is further introduced into the refractory modifier to form a ternary particle mixed distribution with nano-silica particles and silica micropowder. The aluminum hydroxide micropowder adheres to the surface of the gypsum dihydrate crystals and is partially embedded between the gypsum dihydrate crystals. Under high temperature conditions, it decomposes and releases bound water to form an oxide shell, which produces a synergistic refractory effect with the ceramicized connecting layer of nano-silica and the rigid skeleton of silica micropowder, further enhancing the density and high-temperature structural integrity of the refractory layer.

[0016] 3. The present invention uses alkali-free glass fiber treated with silane coupling agent as a dispersed reinforcing fiber, and forms a silane coupling agent treatment layer and an adhesive layer on the fiber surface in sequence. The adhesive layer connects the fiber to the surface of gypsum dihydrate crystals and forms a gradient transition interface between the two, which significantly enhances the interfacial bonding strength between the fiber and the gypsum matrix and avoids the problem of the fiber being pulled out of the gypsum matrix under high temperature conditions.

[0017] 4. This invention employs a ternary interpenetrating network bonding system composed of modified starch, phosphorylated cross-linked starch, and guar gum. The phosphate groups of the phosphorylated cross-linked starch form an ionic bond structure with the calcium ions on the surface of the gypsum dihydrate crystals. The hydroxyl groups of guar gum form a hydrogen bond network with the hydroxyl groups of the modified starch. The guar gum molecular chains interpenetrate between the modified starch molecular chains, forming a stable three-dimensional bonding network, which further enhances the interfacial bonding strength between the fiber and the gypsum crystals.

[0018] 5. This invention regulates the crystal morphology of gypsum dihydrate by using citric acid or sodium tripolyphosphate to make it into a short columnar or blocky crystal form, which improves the interlocking structure between crystals. Combined with the coordination bonding between nano-silica particles and the crystal surface, the surface density is reduced while maintaining the excellent mechanical and fire-resistant properties of the board, achieving a balance between lightweight and high performance. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall process for preparing a fire-resistant paper-faced gypsum board according to the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] like Figure 1 As shown, the method for preparing a fire-resistant paper-faced gypsum board provided by the present invention includes the following steps: preparation of dry mixture, preparation of liquid mixture, preparation of initial slurry, preparation of molding slurry, extrusion molding, drying and trimming.

[0022] Example 1

[0023] Taking a gypsum board manufacturing company as an example, fire-resistant paper-faced gypsum board is prepared according to the following steps.

[0024] Step 1: Preparation of dry mixture 100 parts of β-hemihydrate gypsum powder have a specific surface area of ​​3500 cm². 2 / g, 4 parts of silica powder, and 0.5 parts of binder are added to a dry mixing equipment and dry mixed at 300r / min for 5 minutes to obtain a dry mixture. The silica powder has a particle size of 2μm, and the binder is composed of modified starch, phosphoric acid cross-linked starch and guar gum in a weight ratio of 1:0.45:0.15. The modified starch has a viscosity of 3000mPa·s, the phosphoric acid cross-linked starch has a degree of substitution of 0.10, and the guar gum has a molecular weight of 350,000.

[0025] Step 2: Preparation of Liquid Mixture Add 72 parts water, 6 parts nano silica sol, and 0.1 parts foaming agent into a mixing container and mix at 200 r / min for 3 minutes to obtain a liquid mixture. The nano silica sol has a solid content of 40%, the nano silica particles have a particle size of 50 nm, and the foaming agent is composed of sodium dodecyl sulfate and silicone polyether emulsion in a weight ratio of 2:1.

[0026] Step 3: Preparation of initial slurry The dry mixture is added to the mixing container and mixed with the liquid mixture. The mixture is stirred at 500 r / min for 45 seconds to obtain the initial slurry.

[0027] Step 4: Preparation of molding slurry Two portions of dispersed reinforcing fiber were evenly sprinkled into the initial mixed slurry, and the mixture was stirred at 250 r / min for 20 seconds to obtain the shaped slurry. The dispersed reinforcing fiber was an alkali-free glass fiber with a surface treatment of silane coupling agent, a fiber length of 12 mm, and a single filament diameter of 11 μm. The dispersed reinforcing fiber was continuously sprinkled in a uniform thin laminar flow using a fiber spreading device. The spreading width matched the width of the slurry surface in the mixing container, and the spreading height was 20 cm above the slurry surface. The dispersion density of the dispersed reinforcing fiber in the shaped slurry was 10 dispersed reinforcing fibers per cubic centimeter of slurry. The consistency of the shaped slurry was 50 mm, and the pH value was 7.0.

[0028] Step 5: Extrusion Molding The molding slurry is poured onto the lower protective paper, and then covered with the upper protective paper. The slurry is then extruded by rollers to form a wet gypsum board. The extrusion pressure is 0.35 MPa, and the gap between the upper and lower rollers is 0.8 mm smaller than the target thickness of the wet gypsum board.

[0029] Step Six: Drying The wet gypsum board is solidified on a solidification conveyor belt for 10 minutes, then cut and sent to a dryer for drying. The drying process adopts a three-stage drying process: the first stage drying temperature is 220℃, the drying time is 15 minutes, and the surface wind speed is 4m / s; the second stage drying temperature is 185℃, the drying time is 15 minutes, and the surface wind speed is 3m / s; the third stage drying temperature is 160℃, the drying time is 15 minutes, and the surface wind speed is 2m / s. The moving speed of the board during the three-stage drying process is 3.5m / min. After exiting the dryer, the edges are trimmed to obtain the fire-resistant paper-faced gypsum board product, and the moisture content of the finished product is controlled at 2%.

[0030] Upon testing, the gypsum board prepared in this embodiment has a gypsum dihydrate crystal network skeleton inside the gypsum core material. Nano-silica particles fill the micropores between the gypsum dihydrate crystals, silica powder is dispersed on the surface of the gypsum dihydrate crystals, and dispersed reinforcing fibers are interspersed in the gypsum dihydrate crystal network skeleton. The nano-silica particles, silica powder, and aluminum hydroxide powder are distributed in a ternary particle mixed state inside the gypsum core material. The gypsum dihydrate crystals are short columnar crystals with an aspect ratio of 2:1.

[0031] Example 2

[0032] Taking a building materials company as an example, fire-resistant paper-faced gypsum board is prepared according to the following steps.

[0033] Step 1: Preparation of dry mixture 100 parts of β-hemihydrate gypsum powder, with a specific surface area of ​​3000 cm², are used in the construction. 2 / g, 6 parts of silica powder, and 0.8 parts of binder are added to a dry mixing equipment and dry mixed at 250r / min for 6 minutes to obtain a dry mixture. The silica powder has a particle size of 1.5μm, and the binder is composed of modified starch, phosphoric acid cross-linked starch and guar gum in a weight ratio of 1:0.5:0.12. The modified starch has a viscosity of 4000mPa·s, the phosphoric acid cross-linked starch has a degree of substitution of 0.12, and the guar gum has a molecular weight of 400,000.

[0034] Step 2: Preparation of Liquid Mixture Add 78 parts of water, 8 parts of nano silica sol, and 0.15 parts of foaming agent into a mixing container and mix at 250 r / min for 4 minutes to obtain a liquid mixture. The nano silica sol has a solid content of 45%, the nano silica particles have a particle size of 60 nm, and the foaming agent is composed of sodium dodecylbenzene sulfonate and silicone polyether emulsion in a weight ratio of 2:1.1.

[0035] Step 3: Preparation of initial slurry The dry mixture is added to the mixing container and mixed with the liquid mixture. The mixture is stirred at 550 r / min for 40 seconds to obtain the initial slurry.

[0036] Step 4: Preparation of molding slurry 2.5 parts of dispersed reinforcing fiber were evenly sprinkled into the initial mixed slurry, and stirred at 280 r / min for 25 seconds to obtain the shaped slurry. The dispersed reinforcing fiber was alkali-free glass fiber with a surface treatment of silane coupling agent, with a fiber length of 13 mm and a single filament diameter of 12 μm. The sprinkling method was the same as in Example 1, and the sprinkling height was 25 cm above the slurry surface. The dispersion density of the dispersed reinforcing fiber in the shaped slurry was 12 dispersed reinforcing fibers per cubic centimeter of slurry. The consistency of the shaped slurry was 55 mm, and the pH value was 7.2.

[0037] Step 5: Extrusion Molding The molding slurry is poured onto the lower protective paper, and then covered with the upper protective paper. The slurry is then extruded by rollers to form a wet gypsum board. The extrusion pressure is 0.4 MPa, and the gap between the upper and lower rollers is 0.9 mm smaller than the target thickness of the wet gypsum board.

[0038] Step Six: Drying The wet gypsum board is solidified on a solidification conveyor belt for 12 minutes, then cut and sent to a dryer for drying. The drying process adopts a three-stage drying process: the first stage drying temperature is 230℃, the drying time is 12 minutes, and the surface wind speed is 4.5m / s; the second stage drying temperature is 190℃, the drying time is 12 minutes, and the surface wind speed is 3.5m / s; the third stage drying temperature is 165℃, the drying time is 12 minutes, and the surface wind speed is 2.5m / s. During the three-stage drying process, the board moves at a speed of 4m / min. After exiting the dryer, the edges are trimmed to obtain the fire-resistant paper-faced gypsum board product, and the moisture content of the finished product is controlled at 2.5%.

[0039] In the gypsum board prepared in this embodiment, the dihydrate gypsum crystals are in the form of blocky crystals with an aspect ratio of 1.5:1 and a spherical cavity diameter of 0.3 mm. The inner wall of the spherical cavity is attached with residual shells of nano-silica particles.

[0040] Example 3

[0041] Taking a new materials company as an example, fire-resistant paper-faced gypsum board is prepared according to the following steps.

[0042] Step 1: Preparation of dry mixture 100 parts of β-hemihydrate gypsum powder have a specific surface area of ​​3800 cm². 2 / g, 3 parts of silica powder, and 0.3 parts of binder are added to a dry mixing equipment and dry mixed at 350r / min for 4 minutes to obtain a dry mixture. The silica powder has a particle size of 3μm, and the binder is composed of modified starch, phosphoric acid cross-linked starch and guar gum in a weight ratio of 1:0.35:0.1. The modified starch has a viscosity of 2000mPa·s, the phosphoric acid cross-linked starch has a degree of substitution of 0.08, and the guar gum has a molecular weight of 250,000.

[0043] Step 2: Preparation of Liquid Mixture Add 65 parts water, 5 parts nano silica sol, and 0.08 parts foaming agent into a mixing container and mix at 150 r / min for 3 minutes to obtain a liquid mixture. The nano silica sol has a solid content of 35%, the nano silica particles have a particle size of 40 nm, and the foaming agent is composed of sodium dodecyl sulfate and silicone polyether emulsion in a weight ratio of 2:0.9.

[0044] Step 3: Preparation of initial slurry The dry mixture is added to the mixing container and mixed with the liquid mixture. The mixture is stirred at 450 r / min for 50 seconds to obtain the initial slurry.

[0045] Step 4: Preparation of molding slurry One part of the dispersed reinforcing fiber was evenly sprinkled into the initial mixed slurry, and stirred at 220 r / min for 18 seconds to obtain the shaped slurry. The dispersed reinforcing fiber was an alkali-free glass fiber with a surface treatment of silane coupling agent, a fiber length of 10 mm, and a single filament diameter of 10 μm. The sprinkling method was the same as in Example 1, and the sprinkling height was 15 cm above the slurry surface. The dispersion density of the dispersed reinforcing fiber in the shaped slurry was 7 dispersed reinforcing fibers per cubic centimeter of slurry. The consistency of the shaped slurry was 45 mm, and the pH value was 6.8.

[0046] Step 5: Extrusion Molding The molding slurry is poured onto the lower protective paper, and then the upper protective paper is covered on top. The slurry is then extruded by rollers to form a wet gypsum board. The extrusion pressure is 0.3 MPa, and the gap between the upper and lower rollers is 0.6 mm smaller than the target thickness of the wet gypsum board.

[0047] Step Six: Drying The wet gypsum board is solidified on a solidification conveyor belt for 8 minutes, then cut and sent to a dryer for drying. The drying process adopts a three-stage drying process: the first stage drying temperature is 210℃, the drying time is 18 minutes, and the surface wind speed is 3.5m / s; the second stage drying temperature is 175℃, the drying time is 18 minutes, and the surface wind speed is 2.5m / s; the third stage drying temperature is 155℃, the drying time is 18 minutes, and the surface wind speed is 1.5m / s. During the three-stage drying process, the board moves at a speed of 2.5m / min. After exiting the dryer, the edges are trimmed to obtain the fire-resistant paper-faced gypsum board product, and the moisture content of the finished product is controlled at 1.5%.

[0048] In the gypsum board prepared in this embodiment, the dihydrate gypsum crystals are in the form of short columnar crystals with an aspect ratio of 2.5:1, and citric acid is attached to the surface of the dihydrate gypsum crystals in the form of a molecular layer.

[0049] Compare with Example 1 Gypsum board without added refractory modifier.

[0050] Taking a gypsum board manufacturer as an example, the difference between this comparative example and Example 1 is that no refractory modifier is added, that is, no nano silica sol and silica powder are added. The composition of other raw materials and preparation methods are the same as in Example 1. Specifically, it consists of 100 parts of β hemihydrate gypsum powder, 0.5 parts of binder, 0.1 parts of foaming agent, 72 parts of water, and 2 parts of dispersed reinforcing fiber. The preparation steps are the same as in Example 1, and the resulting product is ordinary paper-faced gypsum board.

[0051] Compare with Example 2 No aluminum hydroxide powder was added to the refractory modifier.

[0052] Taking a gypsum board manufacturing company as an example, the difference between this comparative example and Example 1 is that aluminum hydroxide micro powder is not added to the refractory modifier. The refractory modifier is composed of only 6 parts of nano silica sol and 4 parts of silica micro powder. The weight ratio of nano silica sol to silica micro powder is 1:0.67. The composition of other raw materials and preparation methods are the same as those in Example 1.

[0053] Compare with Example 3 A single modified starch was used as the binder.

[0054] Taking a gypsum board manufacturing company as an example, the difference between this comparative example and Example 1 is that only modified starch is used as the binder, and phosphoric acid crosslinked starch and guar gum are not used. The binder is 0.5 parts of modified starch with a viscosity value of 3000 mPa·s. The composition and preparation method of the remaining raw materials are the same as those in Example 1.

[0055] Performance Testing and Results Analysis The paper-faced gypsum boards prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests, and the test results are shown in Table 1.

[0056] Table 1. Performance test results of gypsum board in the examples and control examples.

[0057] As can be seen from the data in Table 1, the fire-resistant paper-faced gypsum boards prepared in Examples 1-3 are significantly better than those in Control Examples 1-3 in terms of fire stability, fracture load, and dry bending strength, and their thermal conductivity is significantly lower than that of the Control Examples.

[0058] A comparison of Example 1 and Control Example 1 shows that after adding the refractory modifiers nano-silica sol and silica powder, the fire stability increased significantly from 18 min to 52 min, an increase of about 189%, and the thermal conductivity decreased from 0.28 W / m·K to 0.18 W / m·K, a decrease of about 36%. This is because the nano-silica particles fill the micropores between the dihydrate gypsum crystals, and the silica powder is dispersed on the surface of the dihydrate gypsum crystals. Together, they construct a refractory network structure, which effectively prevents the transfer of heat to the interior of the board.

[0059] A comparison of Example 1 and Control Example 2 shows that after adding aluminum hydroxide micro powder to the refractory modifier, the fire stability was further improved from 35 min to 52 min, an increase of about 49%. This is because the aluminum hydroxide micro powder decomposes and releases bound water in the temperature range of 200-300℃, absorbing a large amount of heat. At the same time, it forms an oxide residue on the surface of the gypsum dihydrate crystals, which enhances the density of the refractory layer.

[0060] A comparison of Example 1 and Control Example 3 shows that, after adopting a ternary interpenetrating network bonding system composed of modified starch, phosphorylated cross-linked starch, and guar gum, the breaking load increased from 220 N to 285 N, an increase of about 30%, and the dry bending strength increased from 7.5 MPa to 9.6 MPa, an increase of about 28%. This is because the phosphate groups of phosphorylated cross-linked starch form an ionic bond structure with the calcium ions on the surface of gypsum dihydrate crystals, and the hydroxyl groups of guar gum form a hydrogen bond network with the hydroxyl groups of modified starch. The guar gum molecular chains interpenetrate between the modified starch molecular chains, forming a stable three-dimensional bonding network, which significantly enhances the interfacial bonding strength between the fiber and the gypsum crystal.

[0061] Compared with Example 1, Example 2 has slightly lower fire stability. This is because the proportion of foaming agent used in Example 2 is slightly higher, resulting in more spherical cavities and slightly reducing the density of the board. However, the fracture load and dry bending strength of Example 2 still remain at a high level, indicating that the ternary bonding system can play a stable reinforcing role under different formulation conditions.

[0062] Example 3 at a lower areal density of 6.9 kg / m³ 2 Under these conditions, the highest fire stability of 55 min and the highest dry bending strength of 10.1 MPa were still obtained, indicating that the technical solution of the present invention has achieved a good balance between lightweight and high performance. This is due to the regulatory effect of citric acid on the crystal morphology of gypsum dihydrate, which makes the crystals have a short columnar shape and improves the interlocking structure between crystals.

[0063] In summary, the present invention significantly improves the fire resistance and mechanical properties of paper-faced gypsum board through the synergistic effect of the refractory modifier nano silica sol, silica powder and aluminum hydroxide powder, the surface treatment and interface anchoring system of the dispersed reinforcing fibers, and the combined effect of the ternary interpenetrating network bonding system. All embodiments have achieved technical effects superior to the control examples.

[0064] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A fire-resistant paper-faced gypsum board, characterized in that, It includes gypsum core material and facing paper laminated on the upper and lower surfaces of the gypsum core material. The raw materials of the gypsum core material include, by weight: 100 parts of building gypsum powder, 5-15 parts of fire-resistant modifier, 0.5-3 parts of dispersed reinforcing fiber, 0.1-1 parts of binder, 0.05-0.2 parts of foaming agent, and 60-85 parts of water. The building gypsum powder is β-hemihydrate gypsum with a specific surface area of ​​3000-4000 cm². 2 / g; The refractory modifier is a mixture of nano-silica sol and silica powder. The solid content of the nano-silica sol is 30%-50%, the particle size of the nano-silica particles is 20-100nm, and the particle size of the silica powder is 0.1-5μm. The dispersed reinforcing fiber is an alkali-free glass fiber surface-treated with a silane coupling agent, with a fiber length of 8-15 mm and a single filament diameter of 9-13 μm; The gypsum core material has a gypsum dihydrate crystal network skeleton inside, with nano-silica particles filling the micropores between the gypsum dihydrate crystals, silica powder dispersed on the surface of the gypsum dihydrate crystals, and dispersed reinforcing fibers interspersed in the gypsum dihydrate crystal network skeleton.

2. The gypsum board according to claim 1, characterized in that, The weight ratio of nano-silica sol to silica powder in the refractory modifier is 1:0.5-2. The refractory modifier also contains 5%-20% aluminum hydroxide powder by weight of the total refractory modifier, and the particle size of the aluminum hydroxide powder is 1-8μm. Nano-silica particles, silica powder, and aluminum hydroxide powder are distributed in a ternary particle mixed state inside the gypsum core material. The aluminum hydroxide powder is attached to the surface of the dihydrate gypsum crystals and partially embedded between the dihydrate gypsum crystals.

3. The gypsum board according to claim 1, characterized in that, The surface of the dispersed reinforcing fiber has a silane coupling agent treatment layer. The adhesive is coated on the surface of the dispersed reinforcing fiber in the form of an adhesive layer outside the silane coupling agent treatment layer. The thickness of the adhesive layer is 0.5-2μm. The dispersed reinforcing fiber is connected to the surface of the gypsum dihydrate crystal through the adhesive layer. The adhesive layer forms a gradient transition interface between the dispersed reinforcing fiber and the gypsum dihydrate crystal.

4. The gypsum board according to claim 1, characterized in that, The foaming agent is composed of anionic surfactant and foam stabilizer, with a weight ratio of anionic surfactant to foam stabilizer of 2: 0.8-1.2, the anionic surfactant is at least one of sodium dodecyl sulfate or sodium dodecylbenzene sulfonate, and the foam stabilizer is silicone polyether emulsion; The gypsum core material has a spherical cavity with a diameter of 0.1-0.5 mm. The inner wall of the spherical cavity is attached with a residual shell of nano-silica particles with a thickness of 0.05-0.2 μm.

5. The gypsum board according to claim 1, characterized in that, The gypsum core material also contains at least one of citric acid or sodium tripolyphosphate, accounting for 0.1%-0.5% of the weight of the building gypsum powder. The citric acid or sodium tripolyphosphate is attached to the surface of the dihydrate gypsum crystal in the form of a molecular layer. The nano silica particles in the nano silica sol form a coordination bond structure with the calcium ions on the surface of the dihydrate gypsum crystal through silanol. Gypsum dihydrate crystals exist in the form of short columnar or massive crystals, with an aspect ratio of 1:1 to 3:

1.

6. The gypsum board according to claim 1, characterized in that, The binder is composed of the following components in the following weight ratio: modified starch: phosphorylated crosslinked starch: guar gum = 1: 0.3-0.6: 0.1-0.2; The modified starch has a viscosity of 1000-5000 mPa·s, the degree of substitution of the phosphate-crosslinked starch is 0.05-0.15, and the molecular weight of guar gum is 200,000-500,000. Modified starch, phosphorylated cross-linked starch, and guar gum form a ternary interpenetrating network bonding system inside the gypsum core material. The phosphate groups of phosphorylated cross-linked starch form an ionic bond structure with the calcium ions on the surface of gypsum dihydrate crystals. The hydroxyl groups of guar gum form a hydrogen bond network with the hydroxyl groups of modified starch. Guar gum molecular chains interweave between the modified starch molecular chains.

7. A method for preparing a fire-resistant paper-faced gypsum board according to any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Add building gypsum powder, silica powder, and binder into a dry mixing equipment and dry mix at a speed of 200-400 r / min for 3-8 minutes to obtain a dry mix. Step 2: Add water, nano silica sol, and foaming agent into a mixing container and mix at a speed of 100-300 r / min for 2-5 minutes to obtain a liquid mixture; Step 3: Add the dry mixture to the mixing container and mix with the liquid mixture. Stir at a speed of 400-600 r / min for 30-60 seconds to obtain the initial slurry. Step 4: Evenly sprinkle the dispersed reinforcing fibers into the initial mixed slurry, and continue to stir at a speed of 200-300 r / min for 15-30 seconds to ensure that the dispersed reinforcing fibers are evenly dispersed in the slurry, thus obtaining the shaped slurry; Step 5: Pour the molding slurry onto the lower protective paper, cover it with the upper protective paper, and then extrude it to form a wet gypsum board. The extrusion pressure is 0.2-0.5 MPa. Step 6: Solidify the wet gypsum board on the solidification conveyor belt for 5-15 minutes, cut it, and send it to the dryer for drying. The drying temperature is 150-250℃ and the drying time is 30-60 minutes. After the board is removed from the dryer, it is trimmed to obtain the finished fire-resistant paper-faced gypsum board.

8. The preparation method according to claim 7, characterized in that, The method of spreading the dispersed reinforcing fibers in step four is as follows: the dispersed reinforcing fibers are continuously spread in a uniform thin laminar flow using a fiber spreading device. The spreading width matches the width of the slurry surface in the mixing container, and the spreading height is 10-30cm above the slurry surface. The dispersion density of the reinforcing fibers in the molding slurry is 5-15 dispersed reinforcing fibers per cubic centimeter of slurry.

9. The preparation method according to claim 7, characterized in that, The drying process in step six adopts a three-stage drying method: The first stage of drying is at a temperature of 200-250℃, a drying time of 10-20 minutes, and a wind speed of 3-5m / s on the surface of the board. The second stage of drying is at a temperature of 170-200℃, a drying time of 10-20 minutes, and a wind speed of 2-4 m / s on the surface of the board. The third stage of drying is at a temperature of 150-170℃, a drying time of 10-20 minutes, and a wind speed of 1-3m / s on the surface of the board. The moving speed of the board during the three-stage drying process is 2-5 m / min.

10. The preparation method according to claim 7, characterized in that, In step three, the initial mixing speed of the slurry is 500 r / min and the mixing time is 45 seconds; in step four, the mixing speed after the addition of the dispersing reinforcing fiber is 250 r / min and the mixing time is 20 seconds. The consistency of the molding slurry is in the range of 40-60mm, and the pH value of the molding slurry is controlled between 6.5 and 7.

5. In step five, the extrusion molding adopts a roller extrusion method, and the gap between the upper and lower rollers is 0.5-1.0 mm smaller than the target thickness of the wet gypsum board.

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