Rock wool reinforced phosphogypsum fireproof door core plate and preparation method thereof

Abstract

The present application relates to a rock wool reinforced phosphogypsum fireproof door core plate and a preparation method thereof, and belongs to the technical field of fireproof building materials and phosphogypsum resource utilization. The fireproof door core plate takes phosphogypsum as the main body, constructs an interface functional layer through the grafting reaction of chitosan and quaternary ammonium salt, and is further subjected to hydrophobization treatment, to obtain modified phosphogypsum particles with compact structure through spray granulation. A reactive organic small molecule 2-hydroxyethyl methacrylate, which is not applied in this field, is introduced, so that a micro-crosslinking network is formed in the system, thereby enhancing the wet stability and crack resistance of the material. Rock wool fibers are further combined to construct a three-dimensional reinforcing skeleton, and a silicon-aluminum inorganic gel agent, a redispersible latex powder, a flame retardant and a water repellent are added, to realize a multi-scale synergistic reinforcing structure of inorganic-organic-fiber. The fireproof door core plate prepared by the present application significantly improves the moisture absorption, cracking and performance attenuation of the traditional phosphogypsum plate, and is suitable for the manufacture of high-stability fireproof door core plates.

Description

Technical Field

[0001] This invention relates to the field of inorganic composite materials and fireproof building materials, specifically to a rock wool-reinforced phosphogypsum fireproof door core board and its preparation method. Background Technology

[0002] Phosphogypsum is a major industrial byproduct of wet-process phosphoric acid production. It boasts advantages such as high yield and stable supply, leading to its widespread application in building materials. Phosphogypsum boards, due to their non-combustibility and certain mechanical properties, are used in the production of building partitions and door core panels. However, existing phosphogypsum materials still suffer from problems such as high water absorption, low wet strength, easy pulverization, and poor dimensional stability. In humid environments or under long-term service conditions, they are prone to warping and chipping, making it difficult to meet the comprehensive requirements of fire-resistant door core panels for fire resistance, mechanical properties, and stability.

[0003] To improve the properties of phosphogypsum, existing technologies have enhanced its structural density and toughness by adding cement, lime, cellulose, latex powder, etc. However, these methods are often limited by insufficient interfacial bonding, increased costs due to large addition amounts, and poor system stability. Furthermore, traditional phosphogypsum modification often employs single organic or inorganic methods, making it difficult to simultaneously address the combined performance requirements of water absorption suppression, improved mechanical properties, and enhanced structural stability.

[0004] On the other hand, fireproof door core panels typically use inorganic materials such as rock wool, perlite, and calcium silicate boards. However, these materials suffer from high density, difficulty in molding, or insufficient mechanical strength, and have poor compatibility with the phosphogypsum system, failing to form an ideal synergistic reinforcing structure. Furthermore, no technical approach has been reported in the existing literature to introduce simple but reactive small organic molecules into the phosphogypsum system to construct a micro-crosslinked network to improve its toughness, heat resistance, and wet stability.

[0005] In summary, existing phosphogypsum-based door core boards cannot simultaneously meet the requirements of high fire resistance, low water absorption, high dimensional stability, and high mechanical properties. There is an urgent need for a rock wool-reinforced phosphogypsum fireproof door core board that can achieve synergistic performance improvement through innovative modification methods and structural design. Summary of the Invention

[0006] To overcome the problems of high water absorption, insufficient wet strength, poor interfacial compatibility, and difficulty in meeting the comprehensive performance requirements of fireproof door core panels in the aforementioned background technology, the present invention aims to provide a rock wool-reinforced phosphogypsum fireproof door core panel and its preparation method. This method modifies phosphogypsum through chitosan-quaternary ammonium salt grafting and further hydrophobicates it, forming a stable bifunctional structural layer on its surface. Simultaneously, spray granulation is used to improve particle density and uniformity. Furthermore, the system incorporates 2-hydroxyethyl methacrylate, a simple organic small molecule not previously used in this field, to form a reactive micro-crosslinked network during curing, significantly improving the material's wet structural stability and crack resistance. Rock wool fibers are then used to establish a three-dimensional reinforcing skeleton, which works synergistically with inorganic gelling agents, flame retardants, and latex powder to achieve strengthening, toughening, and improved fire resistance of the phosphogypsum system. The beneficial effects of this invention are: significantly improving the fire resistance, mechanical properties, and dimensional stability of the fireproof door core panel through multi-scale synergistic structural design.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A rock wool-reinforced phosphogypsum fireproof door core board, comprising the following raw materials in parts by weight: 60-85 parts modified phosphogypsum granules; 5-15 parts 2-hydroxyethyl methacrylate; 5-20 parts rock wool fiber; 2-10 parts silica-alumina inorganic gelling agent; 1-6 parts redispersible latex powder; 3-10 parts inorganic flame retardant; 0.5-3 parts water repellent; and 0.5-3 parts reinforcing fiber. The modified phosphogypsum granules are highly stable structured granules obtained by chitosan-quaternary ammonium salt grafting modification, hydrophobic reaction, and spray granulation of phosphogypsum. The silica-alumina inorganic gelling agent is a mixture of silica sol and sodium aluminate at a mass ratio of 2:1.

[0009] Optionally, the modified phosphogypsum granules contain the following raw materials in parts by weight: 80-95 parts phosphogypsum; 1-5 parts chitosan; 1-5 parts quaternary ammonium salt modifier; 0.5-3 parts hydrophobic agent; 0.5-2 parts dispersant; and 0.5-2 parts stabilizer.

[0010] Optionally, the quaternary ammonium salt modifier is dodecyltrimethylammonium chloride; the hydrophobic agent is methyltriethoxysilane; the dispersant is sodium polycarboxylate dispersant; and the stabilizer is polyvinyl alcohol.

[0011] Optionally, the preparation method of modified phosphogypsum particles includes the following steps:

[0012] (1) Phosphogypsum was mixed with chitosan and dodecyltrimethylammonium chloride and grafted under stirring conditions to obtain a phosphogypsum intermediate with a quaternary ammonium salt functional layer on the surface.

[0013] (2) Add methyltriethoxysilane, sodium polycarboxylate dispersant and polyvinyl alcohol to the phosphogypsum intermediate, continue to disperse and mix, and then perform spray granulation treatment to obtain the modified phosphogypsum particles.

[0014] Optionally, the reaction conditions in step (1) are to stir at 40-60°C for 30-90 minutes to allow phosphogypsum to fully undergo a grafting complexation reaction with chitosan and dodecyltrimethylammonium chloride.

[0015] Optionally, the reaction conditions in step (2) are to mix at 50-80°C for 20-60 minutes and then perform spray granulation at a spray temperature of 120-150°C to obtain dense modified phosphogypsum particles.

[0016] Optionally, the silica-alumina inorganic gelling agent is a mixture of silica sol and sodium aluminate in a mass ratio of 2:1; the inorganic flame retardant is a mixture of aluminum hydroxide and magnesium hydroxide in a mass ratio of 3:2; and the water repellent is a mixture of methyl silicone oil and organosilicon resin in a mass ratio of 1:1.

[0017] Optionally, a method for preparing a rock wool-reinforced phosphogypsum fireproof door core board includes the following steps:

[0018] S1, Modified phosphogypsum granules, 2-hydroxyethyl methacrylate, rock wool fiber, silica-alumina inorganic gelling agent, redispersible latex powder, inorganic flame retardant, water repellent and reinforcing fiber are added to the mixer in sequence and dispersed and mixed at high speed until a uniform mixture is formed;

[0019] S2, the uniformly mixed material is conveyed to the molding mold for pressing, and then subjected to heat curing treatment to obtain the rock wool reinforced phosphogypsum fireproof door core board.

[0020] Optionally, the reaction conditions for step S1 are to mix at a high speed of 800-1500 rpm for 5-15 minutes to ensure that all components are fully mixed and homogeneous.

[0021] Optionally, the reaction conditions for step S2 are as follows: pressing at a molding pressure of 5–15 MPa and curing at 120–160°C for 1–3 hours.

[0022] The beneficial effects of this invention are:

[0023] This invention modifies phosphogypsum particles by constructing a structured modification of a chitosan-quaternary ammonium salt grafted layer and a hydrophobic layer, transforming the hygroscopic and unstable sheet-like structure into functional particles with a dense surface and high interfacial activity. This fundamentally improves its compatibility and structural retention in humid environments. Simultaneously, it introduces 2-hydroxyethyl methacrylate into the phosphogypsum core board system for the first time, enabling the formation of a micro-crosslinked network during curing. This effectively compensates for the insufficient toughness of traditional inorganic systems, allowing the material to maintain a continuous stress transmission structure under heated and humid conditions. Furthermore, through a three-dimensional synergistic structural design of "modified phosphogypsum – reactive small molecules – rock wool fiber," the interfacial bonding strength is significantly improved, the material's moisture swelling deformation is significantly reduced, and its overall stability is superior to existing technologies. Attached Figure Description

[0024] The invention will now be further described with reference to the accompanying drawings.

[0025] Figure 1 The infrared spectra of unmodified phosphogypsum and modified phosphogypsum particles are compared.

[0026] Figure 2 Comparison chart of flexural strength and water absorption test results for samples with different ratios;

[0027] Figure 3 A comparison chart of the fire resistance test results for samples with different proportions;

[0028] Figure 4 This is a comparison chart of the test results for the swelling rate and dimensional stability of samples with different formulation ratios. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments. However, the present invention is not limited to the following embodiments. Equivalent adjustments made without departing from the spirit and essence of the present invention should also be considered to fall within the protection scope of the present invention.

[0030] Example 1:

[0031] The purpose of this embodiment is to verify the feasibility of achieving basic mechanical properties, molding effects, and refractory properties of the system under conditions of low material input by using the lower limit values ​​of each component, and to provide a reference for the lowest cost application of materials.

[0032] S1, Preparation of modified phosphogypsum particles

[0033] 80 parts of phosphogypsum were added to a mixing tank, followed by 1 part of chitosan and 1 part of dodecyltrimethylammonium chloride. The mixture was stirred at 40°C for 30 minutes to form a preliminary grafted layer on the surface of the phosphogypsum, yielding a phosphogypsum intermediate. Subsequently, 0.5 parts of methyltriethoxysilane, 0.5 parts of sodium polycarboxylate dispersant, and 0.5 parts of polyvinyl alcohol were added, and the mixture was stirred at 50°C for 20 minutes. Afterward, spray granulation was performed at a spray temperature of 120°C to obtain modified phosphogypsum granules.

[0034] S2, Mixing to prepare a uniform material

[0035] 60 parts of the modified phosphogypsum granules obtained from S1, 5 parts of 2-hydroxyethyl methacrylate, 5 parts of rock wool fiber, 2 parts of silica-alumina inorganic gelling agent, 1 part of redispersible latex powder, 3 parts of inorganic flame retardant, 0.5 parts of water repellent agent, and 0.5 parts of reinforcing fiber were added to a mixer in sequence and mixed at 800 rpm for 5 minutes to form a uniform mixture.

[0036] S3, Compression and Curing Molding

[0037] The mixture of S2 was fed into a mold and pressed into shape at 5MPa. Then it was placed in an oven at 120℃ for 1 hour to obtain rock wool reinforced phosphogypsum fireproof door core board.

[0038] Example 2:

[0039] The purpose of this embodiment is to obtain a fireproof door core board with comprehensive balance of mechanical properties, fire resistance and dimensional stability by using an intermediate value group allocation ratio, so as to verify the performance of the system of the present invention in the optimal performance range.

[0040] S1, Preparation of modified phosphogypsum particles

[0041] 90 parts of phosphogypsum were added to a mixing tank, along with 3 parts of chitosan and 3 parts of dodecyltrimethylammonium chloride. The mixture was stirred at 50°C for 60 minutes to carry out a grafting reaction, yielding a phosphogypsum intermediate. Then, 1.5 parts of methyltriethoxysilane, 1 part of sodium polycarboxylate dispersant, and 1 part of polyvinyl alcohol were added, and mixing continued at 60°C for 40 minutes. The spray granulation temperature was set to 135°C to obtain modified phosphogypsum granules. Figure 1The infrared spectra of phosphogypsum before and after modification show that both curves remain in the main sulfate characteristic absorption regions of 1130, 1020, and 875 cm⁻¹, indicating that the main crystal structure of phosphogypsum has not been destroyed. The modified sample shows obvious negative peaks of C–H stretching vibration at 2920 and 2850 cm⁻¹, proving the successful grafting of dodecyl quaternary ammonium salt. The addition of N–H bending vibration and quaternary ammonium salt characteristic peaks at 1580 and 1470 cm⁻¹ further indicates the formation of the chitosan-quaternary ammonium salt composite layer. The modified sample shows strong Si–O–C, Si–O–Si, and Si–O oscillation peaks in the 1235, 1070, and 520 cm⁻¹ range, indicating that the hydrophobic silane has undergone hydrolysis condensation and solidified on the surface. Simultaneously, the O–H / N–H peaks near 3400 cm⁻¹ are also observed. The enhanced absorption reflects a significant increase in the hydroxyl and amino groups introduced by chitosan. Overall, the new peaks are clear and have strong peak shapes, which fully demonstrates that the multiple modified structures of this invention have been successfully constructed and have significantly changed the surface chemical environment of phosphogypsum.

[0042] S2, Mixing to prepare a uniform material

[0043] 72.5 parts of modified phosphogypsum granules, 10 parts of 2-hydroxyethyl methacrylate, 12.5 parts of rock wool fiber, 6 parts of silica-alumina inorganic gelling agent, 3.5 parts of redispersible latex powder, 6.5 parts of inorganic flame retardant, 1.5 parts of water repellent agent, and 1.5 parts of reinforcing fiber were added to a mixer and mixed at 1100 rpm for 10 minutes to obtain a uniform material.

[0044] S3, Compression and Curing Molding

[0045] The mixture is placed in a mold and pressed into shape at 10 MPa. Then it is placed in an oven at 140°C for 2 hours to cure, resulting in a fireproof door core board with balanced performance.

[0046] Example 3:

[0047] The purpose of this embodiment is to further improve the strength, fire resistance time and dimensional stability of the material by adopting the upper limit ratio of components, so as to verify the applicability of the system of the present invention in high-performance demand scenarios.

[0048] S1, Preparation of modified phosphogypsum particles

[0049] Add 95 parts of phosphogypsum to a mixing tank, along with 5 parts of chitosan and 5 parts of dodecyltrimethylammonium chloride. Stir at 60°C for 90 minutes to form a dense grafted layer on the surface. Add 3 parts of methyltriethoxysilane, 2 parts of sodium polycarboxylate dispersant, and 2 parts of polyvinyl alcohol. Continue mixing at 80°C for 60 minutes, then spray granulate at 150°C to obtain the modified phosphogypsum material with the densest particle structure.

[0050] S2, Mixing to prepare a uniform material

[0051] 85 parts of modified phosphogypsum granules, 15 parts of 2-hydroxyethyl methacrylate, 20 parts of rock wool fiber, 10 parts of silica-alumina inorganic gelling agent, 6 parts of redispersible latex powder, 10 parts of inorganic flame retardant, 3 parts of water repellent agent, and 3 parts of reinforcing fiber were added into a mixer and mixed at 1500 rpm for 15 minutes to form a high-density uniform material.

[0052] S3, Compression and Curing Molding

[0053] The mixture is added to a mold, pressed at 15 MPa, and cured at 160°C for 3 hours to obtain a high-performance rock wool-reinforced phosphogypsum fireproof door core board.

[0054] Comparative Example 1:

[0055] The purpose of this comparative example is to verify the contribution of the surface graft layer to the interparticle bonding force and structural stability by removing the chitosan-quaternary ammonium salt grafted structure and retaining only the hydrophobic modification.

[0056] S1, Preparation of modified phosphogypsum particles

[0057] 90 parts of phosphogypsum were added to a mixing tank. Without adding chitosan and dodecyltrimethylammonium chloride, 1.5 parts of methyltriethoxysilane, 1 part of sodium polycarboxylate dispersant and 1 part of polyvinyl alcohol were added directly. After stirring at 60°C for 40 minutes, spray granulation was carried out at a spray temperature of 135°C to obtain phosphogypsum particles with only hydrophobic modification.

[0058] S2, Mixing to prepare a uniform material

[0059] 72.5 parts of modified phosphogypsum granules obtained from S1, 10 parts of 2-hydroxyethyl methacrylate, 12.5 parts of rock wool fiber, 6 parts of silica-alumina inorganic gelling agent, 3.5 parts of redispersible latex powder, 6.5 parts of inorganic flame retardant, 1.5 parts of water repellent agent, and 1.5 parts of reinforcing fiber were added to a mixer and mixed at 1100 rpm for 10 minutes to obtain a uniform material.

[0060] S3, Compression and Curing Molding

[0061] The uniform material was placed into a mold, pressed at 10 MPa, and cured at 140°C for 2 hours to obtain the fireproof door core board of Comparative Example 1.

[0062] Comparative Example 2:

[0063] The purpose of this comparative example is to verify the effect of the hydrophobic layer on water absorption, swelling rate and medium- to long-term durability by eliminating the hydrophobication reaction and retaining only the chitosan-quaternary ammonium salt grafted structure.

[0064] S1, Preparation of modified phosphogypsum particles

[0065] 90 parts of phosphogypsum were added to a mixing tank, along with 3 parts of chitosan and 3 parts of dodecyltrimethylammonium chloride. The mixture was stirred at 50°C for 60 minutes to obtain a phosphogypsum intermediate. Without adding methyltriethoxysilane, only 1 part of sodium polycarboxylate dispersant and 1 part of polyvinyl alcohol were added. After mixing at 50°C for 20 minutes, the mixture was spray-granulated at a spray temperature of 135°C to obtain graft-modified phosphogypsum granules.

[0066] S2, Mixing to prepare a uniform material

[0067] 72.5 parts of modified phosphogypsum granules, 10 parts of 2-hydroxyethyl methacrylate, 12.5 parts of rock wool fiber, 6 parts of silica-alumina inorganic gelling agent, 3.5 parts of redispersible latex powder, 6.5 parts of inorganic flame retardant, 1.5 parts of water repellent agent, and 1.5 parts of reinforcing fiber were added to a mixer and mixed at 1100 rpm for 10 minutes to obtain a uniform material.

[0068] S3, Compression and Curing Molding

[0069] The mixture was placed in a mold and pressed at 10 MPa, then cured at 140°C for 2 hours to obtain the fireproof door core board of Comparative Example 2.

[0070] Comparative Example 3:

[0071] The purpose of this comparative example is to verify the contribution of the micro-crosslinked network formed by reactive small organic molecules to crack resistance, overall toughness, and wet stability by removing 2-hydroxyethyl methacrylate.

[0072] S1, Preparation of modified phosphogypsum particles

[0073] Completely consistent with Example 2:

[0074] 90 parts of phosphogypsum, 3 parts of chitosan, and 3 parts of dodecyltrimethylammonium chloride were grafted by stirring at 50°C for 60 minutes; 1.5 parts of methyltriethoxysilane, 1 part of sodium polycarboxylate dispersant, and 1 part of polyvinyl alcohol were added and mixed at 60°C for 40 minutes; the mixture was then spray-granulated at 135°C to obtain modified phosphogypsum granules.

[0075] S2, Mixing to prepare a uniform material

[0076] 72.5 parts of modified phosphogypsum granules, 12.5 parts of rock wool fiber, 6 parts of silica-alumina inorganic gelling agent, 3.5 parts of redispersible latex powder, 6.5 parts of inorganic flame retardant, 1.5 parts of water repellent agent, and 1.5 parts of reinforcing fiber were added to a mixer and mixed at 1100 rpm for 10 minutes; 2-hydroxyethyl methacrylate was not added in this comparative example.

[0077] S3, Compression and Curing Molding

[0078] The mixture was placed into a mold, pressed at 10 MPa, and cured at 140°C for 2 hours to obtain the fireproof door core board of Comparative Example 3.

[0079] Performance testing:

[0080] 1. Flexural strength test method

[0081] The prepared fireproof door core board was cut into rectangular specimens of uniform specifications and placed in a dry environment for 24 hours before the test to eliminate the influence of environmental factors. The specimens were then placed in the center of a three-point bending test apparatus. The support spacing and loading speed were set according to national or industry standards. Pressure was applied to the specimens at a constant speed through the loading head. The maximum load at which the specimen fractured or failed was recorded, and the flexural strength was calculated based on the specimen dimensions. Throughout the process, it was necessary to ensure smooth loading and consistent force direction on the specimens to obtain comparable data.

[0082] 2. Water Absorption Rate Test Method

[0083] Each group of samples was dried in an oven until its mass became constant, and its dried mass was recorded. The samples were then completely immersed in room temperature water for the predetermined soaking time. After soaking, the samples were removed, and the surface water was gently wiped away with absorbent paper. The wet mass was then measured again. During the test, it was essential to ensure consistent soaking depth, uniform soaking time, and a constant water temperature to guarantee the comparability of the test results. The water absorption rate was calculated by converting the difference in mass before and after drying to the dry mass.

[0084] 3. Fire resistance test methods

[0085] Install the fireproof door core panel into the specimen frame of the fire resistance testing furnace according to standard dimensions, with the fire-exposed surface facing inwards. Continuously heat the specimen according to the prescribed temperature rise curve, and record the temperature change of the unexposed surface, the surface condition of the specimen, and structural integrity at regular intervals. During the test, observe whether the specimen cracks, detaches, deforms, or penetrates. Determine the material's fire resistance rating based on the time it takes for the specimen to maintain structural integrity and meet the temperature rise standard. During the test, ensure consistent sealing and standardized thermocouple arrangement.

[0086] 4. Test methods for moisture expansion rate and dimensional stability

[0087] Each set of specimens was cut to the specified dimensions, and the initial length, width, and thickness were recorded. The specimens were then placed in a constant temperature and humidity chamber for a specified period under specific relative humidity and temperature conditions. After the curing period, the specimens were removed, and their length, width, and thickness changes were measured again. During the testing process, the temperature and humidity of the chamber must be kept stable, the measuring instruments should be uniformly calibrated, and the specimens should be protected from additional mechanical stress before and after testing to ensure the accuracy of the dimensional change data.

[0088] Table 1 Performance Test Results

[0089] Example 1 7.8 9.5 86 0.62 Example 2 9.4 7.2 98 0.41 Example 3 8.6 8.1 92 0.55 Comparative Example 1 6.1 12.8 74 0.95 Comparative Example 2 5.7 15.4 69 1.12 Comparative Example 3 6.5 11.7 78 0.88

[0090] As shown in Table 1, the embodiments and comparative examples exhibit significant differences in flexural strength, water absorption, fire resistance limit, and moisture expansion rate, indicating that the material structure design has a decisive influence on performance. Example 2 showed the best performance in all four indicators, demonstrating the synergistic effect of "graft modification + hydrophobic modification + organic small molecule micro-crosslinking" that enables the material to achieve higher interfacial bonding strength and structural stability.

[0091] In terms of flexural strength, Figure 2 Example 2 achieved a crack strength of 9.4 MPa, significantly higher than Examples 1 and 3, and also far exceeding the comparative examples. Comparative Examples 1 and 2 lacked grafted or hydrophobic layers, respectively, resulting in weaker interfacial bonding and decreased flexural strength; Comparative Example 3 lacked cross-linking support from small organic molecules, leading to insufficient overall toughness. These results demonstrate that the synergistic effect of the triple structure significantly improves the crack resistance of inorganic systems.

[0092] Regarding water absorption rate, Figure 2 The water absorption rate of Example 2 was only 7.2%, the lowest among all groups, indicating that dual surface modification and micro-crosslinking can effectively inhibit water penetration and capillary adsorption. Comparative Example 2, lacking hydrophobic modification, had a water absorption rate as high as 15.4%, exhibiting typical characteristics of enhanced capillary penetration. Although Comparative Examples 1 and 3 had some modified structures, their overall water absorption control ability was significantly weaker than that of the Example groups.

[0093] In terms of fire resistance, Figure 3 The fire resistance limit of Example 2 was 98 minutes, which was higher than that of the other groups. This is because the triple structure system improved the internal stress dispersion ability, allowing the material to maintain a high degree of integrity under sustained high temperature; while the comparative examples were more prone to cracking, delamination or pulverization under heat due to insufficient structural modification.

[0094] In the wet expansion rate test, Figure 4 Example 2 exhibited the lowest swelling rate, at only 0.41%, indicating the best dimensional stability. The swelling rates of the comparative examples were generally higher. Comparative Example 2 showed significant swelling due to its large water absorption, while Comparative Examples 1 and 3 showed higher dimensional changes due to insufficient interfacial bonding or the absence of cross-linked structures.

[0095] In summary, by constructing a chitosan-quaternary ammonium salt grafted layer, a hydrophobic layer, and a micro-crosslinked network formed by reactive organic small molecules, Example 2 of the present invention achieves significant improvements in mechanical properties, water absorption inhibition, fire resistance stability, and dimensional stability, verifying the effectiveness and necessity of the multi-modification synergistic structure in improving the comprehensive performance of phosphogypsum door core boards.

Claims

1. A rock wool-reinforced phosphogypsum fireproof door core board, characterized in that, The fireproof door core panel comprises the following raw materials in parts by weight: 60-85 parts modified phosphogypsum granules; 5-15 parts 2-hydroxyethyl methacrylate; 5-20 parts rock wool fiber; 2-10 parts silica-alumina inorganic gelling agent; 1-6 parts redispersible latex powder; 3-10 parts inorganic flame retardant; 0.5-3 parts water repellent; and 0.5-3 parts reinforcing fiber. The modified phosphogypsum granules are highly stable structured granules obtained by phosphogypsum through chitosan-quaternary ammonium salt grafting modification, hydrophobic reaction, and spray granulation. The silica-alumina inorganic gelling agent is a mixture of silica sol and sodium aluminate at a mass ratio of 2:

1.

2. The rock wool-reinforced phosphogypsum fireproof door core board according to claim 1, characterized in that, The modified phosphogypsum granules contain the following raw materials in parts by weight: 80-95 parts phosphogypsum; 1-5 parts chitosan; 1-5 parts quaternary ammonium salt modifier; 0.5-3 parts hydrophobic agent; 0.5-2 parts dispersant; and 0.5-2 parts stabilizer.

3. The rock wool-reinforced phosphogypsum fireproof door core board according to claim 2, characterized in that, The quaternary ammonium salt modifier is dodecyltrimethylammonium chloride; the hydrophobic agent is methyltriethoxysilane; the dispersant is sodium polycarboxylate dispersant; and the stabilizer is polyvinyl alcohol.

4. A rock wool-reinforced phosphogypsum fireproof door core board according to any one of claims 1 to 3, characterized in that, The preparation method of the modified phosphogypsum particles includes the following steps: (1) Phosphogypsum was mixed with chitosan and dodecyltrimethylammonium chloride and grafted under stirring conditions to obtain a phosphogypsum intermediate with a quaternary ammonium salt functional layer on the surface. (2) Add methyltriethoxysilane, sodium polycarboxylate dispersant and polyvinyl alcohol to the phosphogypsum intermediate, continue to disperse and mix, and then perform spray granulation treatment to obtain the modified phosphogypsum particles.

5. The rock wool-reinforced phosphogypsum fireproof door core board according to claim 4, characterized in that, The reaction conditions for step (1) are to stir at 40-60°C for 30-90 minutes to allow phosphogypsum to fully undergo a grafting complexation reaction with chitosan and dodecyltrimethylammonium chloride.

6. The rock wool-reinforced phosphogypsum fireproof door core board according to claim 4, characterized in that, The reaction conditions for step (2) are: mixing at 50-80°C for 20-60 minutes followed by spray granulation, with a spray temperature of 120-150°C.

7. The rock wool-reinforced phosphogypsum fireproof door core board according to claim 1, characterized in that, The silica-aluminum inorganic gelling agent is composed of silica sol and sodium aluminate in a mass ratio of 2:1; the inorganic flame retardant is composed of aluminum hydroxide and magnesium hydroxide in a mass ratio of 3:2; and the water repellent is composed of methyl silicone oil and organosilicon resin in a mass ratio of 1:

1.

8. A method for preparing a rock wool reinforced phosphogypsum fireproof door core board, wherein the rock wool reinforced phosphogypsum fireproof door core board is as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1, Modified phosphogypsum granules, 2-hydroxyethyl methacrylate, rock wool fiber, silica-alumina inorganic gelling agent, redispersible latex powder, inorganic flame retardant, water repellent and reinforcing fiber are added to the mixer in sequence and dispersed and mixed at high speed until a uniform mixture is formed; S2, the uniformly mixed material is conveyed to the molding mold for pressing, and then subjected to heat curing treatment to obtain the rock wool reinforced phosphogypsum fireproof door core board.

9. The method for preparing a rock wool-reinforced phosphogypsum fireproof door core board according to claim 8, characterized in that, The reaction conditions for step S1 are mixing at a high-speed mixing speed of 800-1500 rpm for 5-15 minutes.

10. The method for preparing a rock wool-reinforced phosphogypsum fireproof door core board according to claim 8, characterized in that, The reaction conditions for step S2 are as follows: pressing at a molding pressure of 5-15 MPa and curing at 120-160°C for 1-3 hours.

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