A method for optimizing thermal stability in the production of gypsum-based fire-retardant boards

Abstract

The application discloses a kind of gypsum-based fire-retardant board preparation process heat stability optimization method, comprising the following steps: step one: preparation heat stable type modified gypsum powder, step two: preparation interface compatible type compound flame retardant, step three: preparation homogeneous dispersion type gelling slurry, step four: using gradient compaction layering forming process preparation blank, step five: implementation crystal type control type curing process, step six: after low temperature heat baking later modification treatment;The inorganic-organic composite wet modification that the gypsum matrix is carried out in the application can optimize the growth structure of gypsum crystal, make crystal arrangement more dense, effectively slow down the dehydration rate and crystal form conversion speed of gypsum matrix at high temperature, fundamentally improve the thermal stability of matrix itself.

Description

Technical Field

[0001] This invention relates to the field of gypsum-based flame-retardant board preparation technology, specifically a method for optimizing thermal stability during the preparation of gypsum-based flame-retardant boards. Background Technology

[0002] Gypsum-based fire-retardant boards are widely used in fire-resistant engineering projects such as interior decoration and partition walls due to their lightweight, fire resistance, and sound insulation properties. As the matrix of these boards, the thermophysical properties of the gypsum-based material play a decisive role in the overall thermal stability of the board. Current manufacturing processes for gypsum-based fire-retardant boards often achieve fire retardancy simply by adding inorganic flame retardants without specifically modifying the gypsum matrix for thermal stability. This results in a loose gypsum crystal structure, which is prone to rapid dehydration and crystal transformation at high temperatures, leading to cracking, warping, and even structural collapse of the boards. Furthermore, the added flame retardants have poor compatibility with the gypsum matrix, resulting in weak interfacial bonding. At high temperatures, the flame retardants easily migrate and leak out, causing the fire retardant and thermal stability effects of the boards to rapidly decrease with increasing temperature.

[0003] Furthermore, existing manufacturing processes lack thermal stability-oriented design in the molding and curing stages. During molding, uneven pores easily form inside the board, and thermal expansion of these pores at high temperatures can generate internal stress, further exacerbating board damage. Inadequate temperature and rate control during curing can lead to excessive or insufficient growth of gypsum crystals, reducing the matrix's temperature resistance. Currently, the industry lacks a comprehensive thermal stability optimization scheme for gypsum-based flame-retardant boards, encompassing gypsum matrix modification, flame-retardant system control, interface optimization, and coordinated molding and curing processes. Existing boards exhibit poor structural integrity and mechanical property retention under sustained medium- and high-temperature conditions, failing to meet the fire protection requirements of high-grade buildings. Summary of the Invention

[0004] The purpose of this invention is to provide a method for optimizing the thermal stability during the preparation of gypsum-based flame-retardant boards, so as to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for optimizing the thermal stability during the preparation of gypsum-based flame-retardant boards, comprising the following steps: Step 1: Prepare heat-stable modified gypsum powder. Calcine and grind desulfurized gypsum to obtain calcined gypsum powder. Add an inorganic-organic composite modifier to the calcined gypsum powder for wet modification reaction. After the reaction is completed, dry and grind twice to obtain heat-stable modified gypsum powder. Step 2: Prepare an interface-compatible compound flame retardant. Aluminum hydroxide, magnesium hydroxide, and zinc borate are compounded in a certain proportion to obtain an inorganic compound flame retardant. The inorganic compound flame retardant is then surface-modified using a titanate coupling agent and dried to obtain an interface-compatible compound flame retardant. Step 3: Prepare homogeneous dispersion gelling paste by premixing modified gypsum powder, interfacial compatible compound flame retardant, and composite reinforcing fiber dry material, adding water and interfacial modifier, and then mixing them using a stepwise gradient stirring process to obtain homogeneous dispersion gelling paste. Step 4: Prepare the slab blank using a gradient compaction layer molding process. The cementitious slurry is spread in layers according to the volume ratio of the bottom layer, middle layer and surface layer. Each layer is compacted in sequence with an increasing compaction pressure gradient. After each layer is compacted, the pressure is maintained to obtain the gypsum-based flame-retardant board blank. Step 5: Implement crystal form control curing process. First, the slab is cured at room temperature and then cured at low temperature with steam. After the low temperature steam curing, the temperature is reduced to room temperature at a controlled rate. After demolding, it is cured naturally to obtain the initial gypsum-based flame retardant board. Step Six: Perform low-temperature hot drying post-modification treatment. The initial gypsum-based flame retardant board is subjected to constant low-temperature hot drying treatment to gradually remove the internal free water. After the hot drying is completed, it is naturally cooled to room temperature to obtain a gypsum-based flame retardant board with optimized thermal stability.

[0006] Furthermore, in step one, the calcination temperature of the desulfurized gypsum pretreatment is 160-170℃, the calcination time is 2.5-3h, and the particle size of the calcined gypsum powder after grinding is 80-100 mesh; the inorganic-organic composite modifier is composed of metakaolin, water glass, and γ-aminopropyltriethoxysilane, and the amount of metakaolin added is 3-5%, the amount of water glass added is 1-2%, and the amount of γ-aminopropyltriethoxysilane added is 0.8-1.2% based on the mass of the calcined gypsum powder.

[0007] Furthermore, in step one, the solid-liquid ratio of the wet modification reaction is 1:2 (mass ratio of calcined gypsum powder to deionized water), the modification reaction temperature is 60-65℃, the stirring rate is 300-400 r / min, and the reaction time is 1.5-2 h; the drying temperature is 80-90℃, and the material is dried until the moisture content is ≤1%. After secondary grinding, the particle size of the modified gypsum powder is 100-120 mesh.

[0008] Furthermore, in step two, the mass ratio of aluminum hydroxide, magnesium hydroxide, and zinc borate is 5:3:2, the total amount of the interface-compatible compound flame retardant added is 20-25% of the mass of the modified gypsum powder, the amount of titanate coupling agent added is 0.5-0.8% of the total mass of the inorganic compound flame retardant, the surface modification treatment temperature is 50-55℃, and the stirring treatment time is 40-60min.

[0009] Furthermore, in step three, the composite reinforcing fiber is composed of glass fiber and basalt fiber. Based on the mass of the modified gypsum powder, the amount of glass fiber added is 1-2%, and the amount of basalt fiber added is 0.5-1%. The interface modifier is composed of polycarboxylate superplasticizer and hydroxypropyl methylcellulose. The amount of polycarboxylate superplasticizer added is 0.2-0.3% of the mass of the modified gypsum powder, the amount of hydroxypropyl methylcellulose added is 0.1-0.2% of the mass of the modified gypsum powder, and the amount of water added is 60-70% of the mass of the modified gypsum powder.

[0010] Furthermore, in step three, the stepwise gradient mixing process is as follows: first, mix at a low speed of 200-300 r / min for 3-5 min, then mix at a high speed of 800-1000 r / min for 1-2 min; the mixing time for dry material premixing is 5-8 min.

[0011] Furthermore, in step four, the volume ratio of the cementitious slurry in the bottom layer, middle layer, and surface layer is 3:4:3; the gradient compaction pressure is 0.8-1.0 MPa for the bottom layer, 1.2-1.5 MPa for the middle layer, and 1.8-2.0 MPa for the surface layer, with each layer compacted for 30-40 seconds and held for 2-3 minutes.

[0012] Furthermore, in step five, the time for static curing at room temperature is 24-36 hours; the temperature for low-temperature steam curing is 50-60℃, and the curing time is 48-60 hours; the rate of controlled cooling is 2-3℃ / h, and the time for natural curing is 7-10 days.

[0013] Furthermore, in step six, the temperature of the low-temperature heat treatment is 100-110℃, the heat treatment time is 6-8 hours, and the natural cooling is to place it in a room temperature environment to cool down naturally for no less than 4 hours.

[0014] Compared with the prior art, the beneficial effects of the present invention are: The inorganic-organic composite wet modification of gypsum matrix in this invention can optimize the growth structure of gypsum crystals, make the crystal arrangement more compact, effectively slow down the dehydration rate and crystal transformation speed of gypsum matrix at high temperature, and fundamentally improve the thermal stability of the matrix itself.

[0015] The surface modification of the compound flame retardant with titanate coupling agent significantly improves the interfacial bonding force and compatibility between the flame retardant and the gypsum matrix, avoids the migration and loss of the flame retardant under high temperature environment, and ensures the continuity of the flame retardant effect at high temperature. At the same time, the compound design of the flame retardant achieves synergistic flame retardant effect and complements the thermally stable matrix.

[0016] The stepwise gradient mixing process and the addition of interface modifiers solve the problems of agglomeration and uneven dispersion of various components in the cementitious slurry, enabling the flame retardant, reinforcing fibers and gypsum matrix to be evenly combined, reducing the generation of micropores inside the board, and reducing the internal stress caused by thermal expansion of pores at high temperatures and the probability of board breakage.

[0017] The gradient compaction layer forming process makes the structure of each layer of the board dense and the internal stress distribution uniform. It avoids the defects of excessively dense surface and loose interior caused by single compaction pressure, improves the overall structural integrity of the board, and makes it less prone to cracking and warping at high temperatures.

[0018] The crystal-type controlled curing process, through a combination of room temperature static curing, low temperature steam curing, and controlled-speed cooling, can regulate the growth state of gypsum crystals, avoid excessive or insufficient crystal growth, improve the bonding strength between crystals, and at the same time, controlled-speed cooling effectively prevents internal stress caused by sudden temperature changes, further optimizing the structural stability of the board. Attached Figure Description

[0019] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Please see Figure 1 This invention provides a method for optimizing the thermal stability during the preparation of gypsum-based flame-retardant boards, comprising the following steps: Step 1: Prepare heat-stable modified gypsum powder. Calcine and grind desulfurized gypsum to obtain calcined gypsum powder. Add an inorganic-organic composite modifier to the calcined gypsum powder for wet modification reaction. After the reaction is completed, dry and grind twice to obtain heat-stable modified gypsum powder. Step 2: Prepare an interface-compatible compound flame retardant. Aluminum hydroxide, magnesium hydroxide, and zinc borate are compounded in a certain proportion to obtain an inorganic compound flame retardant. The inorganic compound flame retardant is then surface-modified using a titanate coupling agent and dried to obtain an interface-compatible compound flame retardant. Step 3: Prepare homogeneous dispersion gelling paste by premixing modified gypsum powder, interfacial compatible compound flame retardant, and composite reinforcing fiber dry material, adding water and interfacial modifier, and then mixing them using a stepwise gradient stirring process to obtain homogeneous dispersion gelling paste. Step 4: Prepare the slab blank using a gradient compaction layer molding process. The cementitious slurry is spread in layers according to the volume ratio of the bottom layer, middle layer and surface layer. Each layer is compacted in sequence with an increasing compaction pressure gradient. After each layer is compacted, the pressure is maintained to obtain the gypsum-based flame-retardant board blank. Step 5: Implement crystal form control curing process. First, the slab is cured at room temperature and then cured at low temperature with steam. After the low temperature steam curing, the temperature is reduced to room temperature at a controlled rate. After demolding, it is cured naturally to obtain the initial gypsum-based flame retardant board. Step Six: Perform low-temperature hot drying post-modification treatment. The initial gypsum-based flame retardant board is subjected to constant low-temperature hot drying treatment to gradually remove the internal free water. After the hot drying is completed, it is naturally cooled to room temperature to obtain a gypsum-based flame retardant board with optimized thermal stability.

[0022] In step one, the calcination temperature of the desulfurized gypsum pretreatment is 160-170℃, the calcination time is 2.5-3h, and the particle size of the calcined gypsum powder after grinding is 80-100 mesh; the inorganic-organic composite modifier is composed of metakaolin, water glass, and γ-aminopropyltriethoxysilane. Based on the mass of the calcined gypsum powder, the amount of metakaolin added is 3-5%, the amount of water glass added is 1-2%, and the amount of γ-aminopropyltriethoxysilane added is 0.8-1.2%.

[0023] In step one, the solid-liquid ratio of the wet modification reaction is 1:2 (mass ratio of calcined gypsum powder to deionized water), the modification reaction temperature is 60-65℃, the stirring rate is 300-400 r / min, and the reaction time is 1.5-2 h; the drying temperature is 80-90℃, and the material is dried until the moisture content is ≤1%. After secondary grinding, the particle size of the modified gypsum powder is 100-120 mesh.

[0024] In step two, the mass ratio of aluminum hydroxide, magnesium hydroxide, and zinc borate is 5:3:2, the total amount of the interface-compatible compound flame retardant added is 20-25% of the mass of the modified gypsum powder, the amount of titanate coupling agent added is 0.5-0.8% of the total mass of the inorganic compound flame retardant, the surface modification treatment temperature is 50-55℃, and the stirring treatment time is 40-60min.

[0025] In step three, the composite reinforcing fiber is composed of glass fiber and basalt fiber. Based on the mass of modified gypsum powder, the amount of glass fiber added is 1-2%, and the amount of basalt fiber added is 0.5-1%. The interface modifier is composed of polycarboxylate superplasticizer and hydroxypropyl methylcellulose. The amount of polycarboxylate superplasticizer added is 0.2-0.3% of the mass of modified gypsum powder, the amount of hydroxypropyl methylcellulose added is 0.1-0.2% of the mass of modified gypsum powder, and the amount of water added is 60-70% of the mass of modified gypsum powder.

[0026] In step three, the stepwise gradient mixing process is as follows: first, mix at a low speed of 200-300 r / min for 3-5 min, and then mix at a high speed of 800-1000 r / min for 1-2 min; the mixing time for dry material premixing is 5-8 min.

[0027] In step four, the volume ratio of the cementitious slurry in the bottom layer, middle layer, and surface layer is 3:4:3; the pressure of gradient compaction is 0.8-1.0 MPa for the bottom layer, 1.2-1.5 MPa for the middle layer, and 1.8-2.0 MPa for the surface layer, with each layer compacted for 30-40 seconds and held for 2-3 minutes.

[0028] In step five, the time for static curing at room temperature is 24-36 hours; the temperature for low-temperature steam curing is 50-60℃, and the curing time is 48-60 hours; the rate of controlled cooling is 2-3℃ / h, and the time for natural curing is 7-10 days.

[0029] In step six, the temperature for low-temperature hot drying is 100-110℃, the drying time is 6-8 hours, and the natural cooling is to place it in a room temperature environment to cool down naturally for no less than 4 hours.

[0030] Example: This embodiment uses desulfurized gypsum for building as raw material to prepare gypsum-based flame-retardant boards with specifications of 1200mm×600mm×12mm. The thermal stability is optimized according to the following steps: Step 1: Preparation of heat-stable modified gypsum powder Desulfurized gypsum was pretreated in a calcining furnace and calcined at 165℃ for 2.8 hours. After calcination, it was ground to a particle size of 90 mesh to obtain calcined gypsum powder. Based on the mass of the calcined gypsum powder, 4% metakaolin, 1.5% water glass, and 1.0% γ-aminopropyltriethoxysilane were weighed to form an inorganic-organic composite modifier. The calcined gypsum powder and the modifier were added to deionized water to prepare a slurry with a solid-liquid ratio of 1:2. The slurry was stirred at 62℃ and 350 r / min for 1.8 hours to complete the wet modification reaction. The modified slurry was placed in a drying device and dried at 85℃ until the moisture content was ≤1%. It was then ground a second time to 110 mesh to obtain heat-stable modified gypsum powder.

[0031] Step 2: Preparation of interfacially compatible compound flame retardant Aluminum hydroxide, magnesium hydroxide, and zinc borate were weighed in a mass ratio of 5:3:2 and mixed evenly to obtain an inorganic compound flame retardant, the total mass of which was 22% of the mass of the modified gypsum powder. 0.6% of a titanate coupling agent was added to the inorganic compound flame retardant, and the mixture was stirred at 52°C for 50 minutes to complete surface modification. After drying, an interface-compatible compound flame retardant was obtained.

[0032] Step 3: Preparation of homogeneous dispersion gel slurry Based on 100 parts by weight of modified gypsum powder, weigh 1.5 parts glass fiber and 0.8 parts basalt fiber to form a composite reinforcing fiber. Add this fiber, along with the modified gypsum powder and an interfacially compatible compound flame retardant, to a mixer for dry premixing for 7 minutes. Then add 65 parts water, 0.25 parts polycarboxylate superplasticizer, and 0.15 parts hydroxypropyl methylcellulose. First, stir at a low speed of 250 r / min for 4 minutes, then stir at a high speed of 900 r / min for 1.5 minutes to obtain a homogeneous dispersion gel with uniformly dispersed components.

[0033] Step 4: Gradient compaction and layered molding to prepare slabs The gelling slurry was laid into the molding mold in a volume ratio of 3:4:3 for the bottom layer, middle layer, and top layer. A gradient compaction method was used: the bottom layer was compacted at 0.9 MPa for 35 seconds and held at 2.5 minutes; the middle layer was compacted at 1.3 MPa for 35 seconds and held at 2.5 minutes; and the top layer was compacted at 1.9 MPa for 35 seconds and held at 2.5 minutes. After completion, a gypsum-based flame-retardant board blank was obtained.

[0034] Step 5: Crystal Form Regulation Maintenance Process The slab was placed in a room temperature environment for static curing for 30 hours, and then transferred to a steam curing equipment for low-temperature steam curing at 55℃ for 54 hours. After steam curing, it was cooled to room temperature at a rate of 2.5℃ / h. After demolding, the slab was placed in a ventilated and cool environment for natural curing for 8 days to obtain the initial gypsum-based flame-retardant board.

[0035] Step Six: Low-Temperature Hot Drying Post-Treatment Modification The pre-prepared gypsum-based flame-retardant board was placed in a heat-drying equipment and subjected to constant-temperature low-temperature heat-drying treatment at 105℃ for 7 hours to gradually remove free water from the board and promote the formation of a stable bonding structure between the flame retardant and the gypsum matrix. After heat-drying, the board was placed in a room temperature environment to cool naturally for 5 hours. After cooling to room temperature, a gypsum-based flame-retardant board with optimized thermal stability was obtained.

[0036] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for optimizing thermal stability during the preparation of gypsum-based flame-retardant boards, characterized in that: Includes the following steps: Step 1: Prepare heat-stable modified gypsum powder. Calcine and grind desulfurized gypsum to obtain calcined gypsum powder. Add an inorganic-organic composite modifier to the calcined gypsum powder for wet modification reaction. After the reaction is completed, dry and grind twice to obtain heat-stable modified gypsum powder. Step 2: Prepare an interface-compatible compound flame retardant. Aluminum hydroxide, magnesium hydroxide, and zinc borate are compounded in a certain proportion to obtain an inorganic compound flame retardant. The inorganic compound flame retardant is then surface-modified using a titanate coupling agent and dried to obtain an interface-compatible compound flame retardant. Step 3: Prepare homogeneous dispersion gelling paste by premixing modified gypsum powder, interfacial compatible compound flame retardant, and composite reinforcing fiber dry material, adding water and interfacial modifier, and then mixing them using a stepwise gradient stirring process to obtain homogeneous dispersion gelling paste. Step 4: Prepare the slab blank using a gradient compaction layer molding process. The cementitious slurry is spread in layers according to the volume ratio of the bottom layer, middle layer and surface layer. Each layer is compacted in sequence with an increasing compaction pressure gradient. After each layer is compacted, the pressure is maintained to obtain the gypsum-based flame-retardant board blank. Step 5: Implement crystal form control curing process. First, the slab is cured at room temperature and then cured at low temperature with steam. After the low temperature steam curing, the temperature is reduced to room temperature at a controlled rate. After demolding, it is cured naturally to obtain the initial gypsum-based flame retardant board. Step Six: Perform low-temperature hot drying post-modification treatment. The initial gypsum-based flame retardant board is subjected to constant low-temperature hot drying treatment to gradually remove the internal free water. After the hot drying is completed, it is naturally cooled to room temperature to obtain a gypsum-based flame retardant board with optimized thermal stability.

2. The method for optimizing thermal stability during the preparation of gypsum-based flame-retardant boards according to claim 1, characterized in that: In step one, the calcination temperature of the desulfurized gypsum pretreatment is 160-170℃, the calcination time is 2.5-3h, and the particle size of the calcined gypsum powder after grinding is 80-100 mesh; the inorganic-organic composite modifier is composed of metakaolin, water glass, and γ-aminopropyltriethoxysilane. Based on the mass of the calcined gypsum powder, the amount of metakaolin added is 3-5%, the amount of water glass added is 1-2%, and the amount of γ-aminopropyltriethoxysilane added is 0.8-1.2%.

3. The method for optimizing thermal stability during the preparation of gypsum-based flame-retardant boards according to claim 1, characterized in that: In step one, the solid-liquid ratio of the wet modification reaction is 1:2 (mass ratio of calcined gypsum powder to deionized water), the modification reaction temperature is 60-65℃, the stirring rate is 300-400 r / min, and the reaction time is 1.5-2 h; the drying temperature is 80-90℃, and the material is dried until the moisture content is ≤1%. After secondary grinding, the particle size of the modified gypsum powder is 100-120 mesh.

4. The method for optimizing thermal stability during the preparation of gypsum-based flame-retardant boards according to claim 1, characterized in that: In step two, the mass ratio of aluminum hydroxide, magnesium hydroxide, and zinc borate is 5:3:2, the total amount of the interface-compatible compound flame retardant added is 20-25% of the mass of the modified gypsum powder, the amount of titanate coupling agent added is 0.5-0.8% of the total mass of the inorganic compound flame retardant, the surface modification treatment temperature is 50-55℃, and the stirring treatment time is 40-60min.

5. The method for optimizing thermal stability during the preparation of gypsum-based flame-retardant board according to claim 1, characterized in that: In step three, the composite reinforcing fiber is composed of glass fiber and basalt fiber. Based on the mass of modified gypsum powder, the amount of glass fiber added is 1-2%, and the amount of basalt fiber added is 0.5-1%. The interface modifier is composed of polycarboxylate superplasticizer and hydroxypropyl methylcellulose. The amount of polycarboxylate superplasticizer added is 0.2-0.3% of the mass of modified gypsum powder, the amount of hydroxypropyl methylcellulose added is 0.1-0.2% of the mass of modified gypsum powder, and the amount of water added is 60-70% of the mass of modified gypsum powder.

6. The method for optimizing thermal stability during the preparation of gypsum-based flame-retardant board according to claim 1, characterized in that: In step three, the stepwise gradient mixing process is as follows: first, mix at a low speed of 200-300 r / min for 3-5 min, then mix at a high speed of 800-1000 r / min for 1-2 min; the mixing time for dry material premixing is 5-8 min.

7. The method for optimizing thermal stability during the preparation of gypsum-based flame-retardant board according to claim 1, characterized in that: In step four, the volume ratio of the cementitious slurry in the bottom layer, middle layer, and surface layer is 3:4:3; the gradient compaction pressure is 0.8-1.0 MPa for the bottom layer, 1.2-1.5 MPa for the middle layer, and 1.8-2.0 MPa for the surface layer, with each layer compacted for 30-40 seconds and held for 2-3 minutes.

8. The method for optimizing thermal stability during the preparation of gypsum-based flame-retardant board according to claim 1, characterized in that: In step five, the time for static curing at room temperature is 24-36 hours; the temperature for low-temperature steam curing is 50-60℃, and the curing time is 48-60 hours; the rate of controlled cooling is 2-3℃ / h, and the time for natural curing is 7-10 days.

9. The method for optimizing thermal stability during the preparation of gypsum-based flame-retardant board according to claim 1, characterized in that: In step six, the temperature of the low-temperature heat treatment is 100-110℃, the heat treatment time is 6-8 hours, and the natural cooling is to place it in a room temperature environment to cool down naturally for no less than 4 hours.

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