Anti-crack easy-to-demould non-adhesion fiber cement board and preparation method thereof

Abstract

The invention provides an anti-crack easy-to-demould non-adhesion fiber cement board, which is prepared from the following raw materials: a calcium material, a siliceous material, bentonite, mica powder, wollastonite, microfibrillated fiber, HPMC and paper pulp, the calcium material is cement, the siliceous material comprises quartz sand, quartz powder and silica fume, and the mass ratio of the calcium material to the siliceous material is 0.9-1.0. In addition, the invention also provides a preparation method of the anti-crack easy-to-demould non-adhesion fiber cement board. The anti-cracking easy-to-demould non-adhesion fiber cement board is low in curing temperature, short in curing time, energy-saving, green and environment-friendly, relatively low in comprehensive cost, relatively high in density, non-sticky in demould, non-adhesion and crack-free after being discharged from a kettle, good in stability and excellent in performance in a freezing and thawing cycle weather resistance experiment, solves the difficult problems of board sticking, adhesion and the like of a production line, and has a good application prospect. The productivity of a production line is brought into full play, the product percent of pass of the production line is improved, and the manufactured plates can meet the use requirements of external wall panels in extreme climate areas.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a crack-resistant, easy-to-demold, non-adhesive fiber cement board and its preparation method. Background Technology

[0002] Fiber cement board is a type of board made by using cement as a binder and organic synthetic fibers, inorganic mineral fibers, or cellulose fibers as reinforcing materials, through molding, pressure (or non-pressure), and autoclaving (or non-autoclaving). Fiber cement board features high strength, weather resistance, moisture and water resistance, flame retardancy, corrosion and antibacterial properties, good machinability (sawing, drilling, nailing, planing, drilling, grooving, etc.), ease of decoration, and good sound and heat insulation properties. It can be widely used in non-load-bearing interior and exterior wall panels, ceilings, and mobile homes. Furthermore, this type of board uses inorganic materials such as cement and quartz sand, resulting in no free formaldehyde release during use, making it energy-saving and environmentally friendly.

[0003] Currently, fiber cement exterior wall panels are typically formed using the slurry casting method, sheet forming method, or extrusion method. In China, the first two methods are mainly used, followed by autoclaving / non-autoclaving. The production process of fiber cement boards often encounters several challenging problems that affect the actual production line capacity, such as: 1. Adhesion after pressure pre-curing leads to low demolding efficiency of the demolding machine, requiring manual intervention and significantly increasing the workload of workers; 2. Adhesion between boards after autoclaving results in low efficiency of the stacking machine. Multiple adhered boards are prone to falling off during stacking, causing board damage, wasting resources, and requiring manual cleaning, severely impacting stacking efficiency. Even if adhesion is detected in time, manual intervention is still required, greatly increasing the workload of workers; 3. The high moisture content of the boards after autoclaving, despite some manufacturers equipping them with post-autoclave insulation sheds, still easily leads to shrinkage and cracking, especially in autumn and winter when temperature differences are large, wasting resources and generating difficult-to-manage solid waste. Therefore, there is an urgent need to find a way to solve the thorny problems of plate sticking and adhesion on the production line, to fully utilize the production line capacity, improve the product qualification rate, and produce panels that can fully meet the needs of exterior wall panels in extreme climate zones. Summary of the Invention

[0004] The purpose of this invention is to provide a crack-resistant, easy-to-demold, and non-adhesive fiber cement board, which can at least solve some of the defects existing in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A crack-resistant, easy-to-demold, non-adhesive fiber cement board comprises the following raw materials: calcareous material, siliceous material, bentonite, mica powder, wollastonite, microfiber, HPMC, and pulp. The calcareous material is cement, and the siliceous material includes quartz sand, quartz powder, and microsilica powder. The mass ratio of the calcareous material to the siliceous material is 0.9 to 1.0.

[0007] Furthermore, the aforementioned crack-resistant, easily demolded, and non-adhesive fiber cement board comprises the following raw materials by weight: 45-50 parts cement, 31-50 parts quartz sand, 3-7 parts quartz powder, 3-7 parts microsilica powder, 0.5-1.5 parts bentonite, 1-5 parts mica powder, 2-4 parts wollastonite, 0.2-0.5 parts microfiber, 0.3-0.8 parts HPMC, and 6-8 parts pulp.

[0008] Furthermore, the SiO2 content in the quartz sand is >90wt%, and the residue on a 180-mesh sieve is less than 1wt%; the SiO2 content in the quartz powder is >95wt%, and the residue on an 800-mesh sieve is less than 0.5wt%; the SiO2 content in the microsilica powder is >85wt%, and the specific surface area of ​​the microsilica powder is 15000–35000 m². 2 / kg.

[0009] Furthermore, the bentonite contains SiO2 content >70wt% and Al2O3 content >10wt%.

[0010] Furthermore, the SiO2 content in the mica powder is ≤60wt%, and the residue on a 400-mesh sieve is less than 1wt%.

[0011] Furthermore, the SiO2 content in the wollastonite is ≥45wt%, and the residue of the wollastonite on a 200-mesh sieve is less than 0.5wt%.

[0012] Furthermore, the microfibrillated fibers contain 5-8 wt% lignin, 9-12 wt% hemicellulose, and 80-86 wt% cellulose; the microfibrillated fibers have a diameter of 1-100 nm and a length of less than 20 μm.

[0013] Furthermore, the solid content of the pulp is 3.0 wt%.

[0014] In addition, the present invention also provides a method for preparing the above-mentioned crack-resistant, easy-to-demold, non-adhesive fiber cement board, comprising the following steps:

[0015] S1. Weigh the cement, quartz sand, quartz powder, microsilica powder, bentonite, mica powder, wollastonite, and HPMC according to the designed dosage and put them into a mixer to mix evenly. Then mix the mixed powder with microfibrillated fiber, pulp, and water evenly to obtain a slurry with a concentration of 13-17%.

[0016] S2. The obtained slurry is evenly spread onto the felt through the headbox and filtered to form a wet blank.

[0017] S3. The prepared wet blank is subjected to moisture curing and autoclaving to obtain the initial product;

[0018] S4. The obtained initial product is dried to reduce its moisture content to less than 10 wt%, thus obtaining crack-resistant, easy-to-demold, and non-adhesive fiber cement board.

[0019] Furthermore, in S3, the process conditions for moisture curing are: moisture curing temperature 45-60℃, humidity not less than 90%, and moisture curing time 4-6h; the process conditions for autoclaving are: constant pressure curing at 160-190℃ saturated vapor pressure for 6-10h.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) The crack-resistant, easy-to-demold, non-adhesive fiber cement board provided by this invention has a density of 1.50–1.53 g / cm³. 3 Impact resistance ranges from 2.55 to 3.22 kJ / m. 2 The saturated flexural strength is 15.77–17.41 MPa, the shrinkage and swelling rate is 0.10% or less, and the flexural strength ratio is 90.55–92.67% after 100 freeze-thaw cycles in a -20℃ environment. It does not stick to the autoclave after demolding and does not clump together. There is no cracking after it leaves the autoclave. Compared with most fiber cement boards on the market, it has higher flexural strength, impact strength, lower swelling rate and excellent weather resistance. The production line operates smoothly and the product qualification rate and capacity compliance rate are extremely high.

[0022] (2) The crack-resistant, easy-to-demold, non-adhesive fiber cement board provided by this invention uses low-cost raw materials, has a high cost-performance ratio, and is green and environmentally friendly, making it more competitive in the market among similar fiber cement board products. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0024] This invention provides a crack-resistant, easy-to-demold, non-adhesive fiber cement board, comprising the following raw materials: calcareous material, siliceous material, bentonite, mica powder, wollastonite, microfiber, HPMC, and pulp. The calcareous material is cement, and the siliceous material includes quartz sand, quartz powder, and microsilica powder. The mass ratio of the calcareous material to the siliceous material is 0.9 to 1.0.

[0025] The cement mentioned can be ordinary Portland cement.

[0026] In this invention, the design principles for selecting the main raw materials for preparing crack-resistant, easily demolded, and non-adhesive fiber cement boards are as follows:

[0027] Calcareous and siliceous materials participate in the reaction at a fixed ratio of 0.9 to 1.0. The reaction products are mainly tobermorite, hydrated garnet, and hydrated calcium silicate. Through the synergistic effect of various materials with different particle sizes, a densely packed particle size distribution is formed. At the same time, the calcium-silica ratio of the raw materials is adjusted within a specific range. Microsilica and quartz powder have high activity and can react more with calcium hydroxide generated by cement hydration under autoclaving conditions to form tobermorite crystals. The unreacted microsilica, quartz powder, and quartz sand can also play a good filling role, forming a dense matrix structure together with the hydration products, thereby greatly improving the strength of the product.

[0028] HPMC has the following functions: 1. It provides a continuous water supply for cement hydration by significantly slowing down the excessive water loss of the slab surface; 2. It has a thickening and suspending effect, increasing the viscosity of the cement paste, preventing the sedimentation and stratification of solid particles (such as cement and quartz sand), and ensuring the uniformity and stability of the paste composition; 3. It has a synergistic reinforcing effect with fibers (including microfibrillated fibers, fibers in pulp, and fibrous wollastonite), improving the adhesion between fibers and the cement matrix, and indirectly enhancing the mechanical properties of the slab; 4. It inhibits crack formation and effectively reduces the generation of plastic shrinkage cracks.

[0029] Bentonite acts as a bridging adsorption between products and raw materials, connecting reaction products, unreacted parts, and filler materials such as quartz sand, quartz powder, and pulp fibers into a complete whole, further enhancing the structural density. Bentonite can also act as an admixture to regulate the slurry and as an adsorbent to enhance bridging adsorption. However, excessive water retention can also delay cement hydration, resulting in slow early strength improvement.

[0030] The blending of long, medium, and short fibers from pulp, wollastonite, and microfibrillated fibers results in fiber cement boards exhibiting outstanding crack resistance, frost resistance, and volume stability. Wollastonite, with its fibrous morphology, can partially replace microfibers to reinforce the cementitious material, while also reducing the product's shrinkage and swelling rates, thus improving its resistance to microcracks caused by water loss or stress. Pulp, being an inorganic fiber, acts as a reinforcing fiber in the product, effectively reducing macroscopic cracking. However, it is prone to degradation in high-temperature, high-pressure, and high-alkalinity environments, affecting the overall performance of the fiber and the product. Microfibrillated fibers can act as flocculants to adsorb powder, reducing material loss and improving the overall performance of the product. They can also work with microsilica to protect plant fibers, extending their lifespan, ultimately reducing the adverse effects of steam curing on the fibers, improving the physical and mechanical properties of the cured board, and solving problems such as board adhesion and post-coating cracking.

[0031] In some embodiments, the crack-resistant, easily demolded, and non-adhesive fiber cement board of the present invention comprises the following raw materials by weight: 45-50 parts cement, 31-50 parts quartz sand, 3-7 parts quartz powder, 3-7 parts microsilica powder, 0.5-1.5 parts bentonite, 1-5 parts mica powder, 2-4 parts wollastonite, 0.2-0.5 parts microfibrillated fiber, 0.3-0.8 parts HPMC, and 6-8 parts pulp. Preferably, 2 parts wollastonite, 0.3 parts microfibrillated fiber, and 7 parts pulp are used.

[0032] Optimized, the quartz sand contains >90wt% SiO2, and the residue on an 180-mesh sieve is less than 1wt%; the quartz powder contains >95wt% SiO2, and the residue on an 800-mesh sieve is less than 0.5wt%; the silica powder contains >85wt% SiO2, and the specific surface area of ​​the silica powder is 15000–35000 m². 2 / kg. For siliceous materials (i.e., quartz sand, quartz powder, and microsilica), different particle sizes are designed. Through the synergistic effect of various siliceous materials with different particle sizes, a closely packed particle size distribution is formed, thereby further improving the strength of the product.

[0033] The optimized bentonite contains SiO2 content >70wt% and Al2O3 content >10wt%; the mica powder contains SiO2 content ≤60wt% and has a 400-mesh sieve residue of less than 1wt%; the wollastonite contains SiO2 content ≥45wt% and has a 200-mesh sieve residue of less than 0.5wt%.

[0034] The optimized microfiber contains 5-8 wt% lignin, 9-12 wt% hemicellulose, and 80-86 wt% cellulose. Cellulose, with its high crystallinity, serves as the core source of fiber strength. After microfiberization, it forms an ultrafine fiber network, enhancing physical entanglement with the cement matrix and improving the flexural strength and fracture toughness of the fiber cement board. Furthermore, microfiberization reduces fiber agglomeration, ensuring uniform distribution in the cement paste and preventing cracking caused by localized stress concentration. Hemicellulose contains a large number of hydroxyl groups (-OH), which can react with cement hydration products (such as CSH). The fiber (gel) forms hydrogen bonds, enhancing the interfacial bonding between the fiber and the cement matrix, reducing the risk of delamination. Furthermore, the strong hydrophilicity of hemicellulose slows down water evaporation during cement hydration, improving the internal density of the fiber cement board. Lignin acts as a natural binder, filling the tiny pores between the fiber and cement, enhancing the overall flexibility of the fiber cement board. Simultaneously, the aromatic structure of lignin possesses antibacterial and insect-resistant properties, delaying fiber degradation in the alkaline environment of cement and extending the service life of the fiber cement board. By employing microfibrillated fibers with specific composite components, cellulose ensures strength, hemicellulose optimizes interfacial bonding, and lignin balances corrosion resistance and toughness, avoiding performance limitations caused by single components. Preferably, the microfibrillated fibers are designed with a diameter of 1–100 nm and a length of less than 20 μm.

[0035] The optimized pulp has a solid content of 3.0 wt%.

[0036] The specific preparation process of the crack-resistant, easy-to-demold, and non-adhesive fiber cement board in this embodiment is as follows:

[0037] S1. Weigh the cement, quartz sand, quartz powder, silica fume, bentonite, mica powder, wollastonite, and HPMC according to the designed dosage and put them into a mixer to mix evenly. Then mix the mixed powder with microfibrillated fiber, pulp, and water evenly to obtain a slurry with a concentration of 13-17%.

[0038] S2. The obtained slurry is evenly spread onto the felt through the headbox and filtered to form a wet blank.

[0039] S3. The prepared wet blank is subjected to moisture curing and autoclaving to obtain the initial product.

[0040] Specifically, the wet billets are stacked, pressurized and kept under pressure, and then placed in a pre-curing chamber. They are then cured in a humid environment with a temperature of 45-60℃ and a humidity of not less than 90% for 4-6 hours to obtain the billet. The billet is then placed in an autoclave and cured under constant pressure at 160-190℃ and saturated steam pressure for 6-10 hours.

[0041] Preferably, the moisture curing process conditions are: moisture curing temperature 45℃, humidity not less than 90%, and moisture curing time 4 hours; the autoclaving process conditions are: constant pressure curing at 160℃ saturated vapor pressure for 6 hours. Due to the formulation design of the fiber cement board in this invention, fiber cement boards with higher flexural strength, impact strength, lower moisture expansion rate, and excellent weather resistance can be produced even under lower curing conditions (i.e., moisture curing temperature only 45℃, moisture curing time only 4 hours, autoclaving steam pressure only 160℃ saturated vapor pressure, and constant pressure curing only 6 hours).

[0042] S4. The obtained initial product is dried to reduce its moisture content to less than 10 wt%, thus obtaining crack-resistant, easy-to-demold, and non-adhesive fiber cement board.

[0043] The performance and effects of the crack-resistant, easy-to-demold, non-adhesive fiber cement board of the present invention are illustrated below through specific embodiments.

[0044] Example 1:

[0045] This embodiment provides a crack-resistant, easy-to-demold, non-adhesive fiber cement board, comprising the following components by weight: 45 parts cement, 31 parts quartz sand, 7 parts quartz powder, 7 parts silica fume, 0.5 parts bentonite, 1 part mica powder, 2 parts wollastonite, 0.2 parts microfibrillated fiber, 0.3 parts HPMC, and 8 parts pulp.

[0046] The cement used is ordinary Portland cement; the SiO2 content in the quartz sand is >90wt%, and the residue on a 180-mesh sieve is less than 1wt%; the SiO2 content in the quartz powder is >95wt%, and the residue on an 800-mesh sieve is less than 0.5wt%; the SiO2 content in the microsilica powder is >85wt%, and the specific surface area of ​​the microsilica powder is between 15,000 and 35,000 m². 2 / kg; the SiO2 content in bentonite is >70wt%, and the Al2O3 content is >10wt%; the SiO2 content in mica powder is ≤60wt%, and the residue on a 400-mesh sieve of mica powder is less than 1wt%; the SiO2 content in wollastonite is ≥45wt%, and the residue on a 200-mesh sieve of wollastonite is less than 0.5wt%; the solid content of the pulp is 3.0wt%; the microfibrillated fibers contain 6wt% lignin, 10wt% hemicellulose and 84wt% cellulose, and the diameter of the microfibrillated fibers is 1-100nm and the length is less than 20um.

[0047] The specific preparation process of this crack-resistant, easy-to-demold, and non-adhesive fiber cement board is as follows:

[0048] 1) Weigh the cement, quartz sand, quartz powder, microsilica powder, bentonite, mica powder, wollastonite, and HPMC according to the designed dosage and put them into the mixer to mix evenly. Then mix the mixed powder, microfibrillated fiber, pulp, and water together to obtain a slurry with a concentration of 13%.

[0049] 2) The slurry obtained in step 1) is evenly spread onto the felt through a headbox and then filtered to form a wet blank;

[0050] 3) Stack, press and hold the wet blanks obtained in step 2), and then place them in a pre-curing box. Cur them in a humid environment with a temperature of 45℃ and a humidity of not less than 90% for 4 hours to obtain the blanks.

[0051] 4) Place the green body obtained in step 3) in an autoclave and cure it under constant pressure for 6 hours at 160℃ saturated steam pressure to obtain crack-resistant and easy-to-demold fiber cement board products.

[0052] 5) The crack-resistant and easy-to-demold fiber cement board product obtained in step 4) is dried to reduce its moisture content to less than 10 wt%, thus obtaining the crack-resistant and easy-to-demold fiber cement board.

[0053] Example 2:

[0054] This embodiment provides a crack-resistant, easy-to-demold, non-adhesive fiber cement board, comprising the following components by weight: 50 parts cement, 36 parts quartz sand, 7 parts quartz powder, 7 parts silica fume, 1.5 parts bentonite, 5 parts mica powder, 4 parts wollastonite, 0.5 parts microfibrillated fiber, 0.8 parts HPMC, and 6 parts pulp.

[0055] The cement used is ordinary Portland cement; the SiO2 content in the quartz sand is >90wt%, and the residue on a 180-mesh sieve is less than 1wt%; the SiO2 content in the quartz powder is >95wt%, and the residue on an 800-mesh sieve is less than 0.5wt%; the SiO2 content in the microsilica powder is >85wt%, and the specific surface area of ​​the microsilica powder is between 15,000 and 35,000 m². 2 / kg; the SiO2 content in bentonite is >70wt%, and the Al2O3 content is >10wt%; the SiO2 content in mica powder is ≤60wt%, and the residue on a 400-mesh sieve of mica powder is less than 1wt%; the SiO2 content in wollastonite is ≥45wt%, and the residue on a 200-mesh sieve of wollastonite is less than 0.5wt%; the solid content of the pulp is 3.0wt%; the microfibrillated fibers contain 5wt% lignin, 9wt% hemicellulose and 86wt% cellulose, and the diameter of the microfibrillated fibers is 1-100nm and the length is less than 20um.

[0056] The specific preparation process of this crack-resistant, easy-to-demold, and non-adhesive fiber cement board is as follows:

[0057] 1) Weigh the cement, quartz sand, quartz powder, silica fume, bentonite, mica powder, wollastonite, and HPMC according to the designed dosage and put them into the mixer to mix evenly. Then mix the mixed powder, microfibrillated fiber, pulp, and water together to obtain a slurry with a concentration of 17%.

[0058] 2) The slurry obtained in step 1) is evenly spread onto the felt through a headbox and then filtered to form a wet blank;

[0059] 3) Stack, press and hold the wet blanks obtained in step 2), and then place them in a pre-curing box. Cur them in a humid environment with a temperature of 45℃ and a humidity of not less than 90% for 4 hours to obtain the blanks.

[0060] 4) Place the green body obtained in step 3) in an autoclave and cure it under constant pressure for 6 hours at 160℃ saturated steam pressure to obtain crack-resistant and easy-to-demold fiber cement board products.

[0061] 5) The crack-resistant and easy-to-demold fiber cement board product obtained in step 4) is dried to reduce its moisture content to less than 10 wt%, thus obtaining the crack-resistant and easy-to-demold fiber cement board.

[0062] Example 3:

[0063] This embodiment provides a crack-resistant, easy-to-demold, non-adhesive fiber cement board, comprising the following components by weight: 45 parts cement, 38 parts quartz sand, 5 parts quartz powder, 7 parts silica fume, 0.8 parts bentonite, 5 parts mica powder, 2 parts wollastonite, 0.3 parts microfibrillated fiber, 0.5 parts HPMC, and 7 parts pulp.

[0064] The cement used is ordinary Portland cement; the SiO2 content in the quartz sand is >90wt%, and the residue on a 180-mesh sieve is less than 1wt%; the SiO2 content in the quartz powder is >95wt%, and the residue on an 800-mesh sieve is less than 0.5wt%; the SiO2 content in the microsilica powder is >85wt%, and the specific surface area of ​​the microsilica powder is between 15,000 and 35,000 m². 2 / kg; the SiO2 content in bentonite is >70wt%, and the Al2O3 content is >10wt%; the SiO2 content in mica powder is ≤60wt%, and the residue on a 400-mesh sieve of mica powder is less than 1wt%; the SiO2 content in wollastonite is ≥45wt%, and the residue on a 200-mesh sieve of wollastonite is less than 0.5wt%; the solid content of the pulp is 3.0wt%; the microfibrillated fibers contain 8wt% lignin, 12wt% hemicellulose and 80wt% cellulose, and the diameter of the microfibrillated fibers is 1-100nm and the length is less than 20um.

[0065] The specific preparation process of this crack-resistant, easy-to-demold, and non-adhesive fiber cement board is as follows:

[0066] 1) Weigh the cement, quartz sand, quartz powder, microsilica powder, bentonite, mica powder, wollastonite, and HPMC according to the designed dosage and put them into the mixer to mix evenly. Then mix the mixed powder, microfibrillated fiber, pulp, and water together evenly to obtain a slurry with a concentration of 15%.

[0067] 2) The slurry obtained in step 1) is evenly spread onto the felt through a headbox and then filtered to form a wet blank;

[0068] 3) Stack, press and hold the wet blanks obtained in step 2), and then place them in a pre-curing box. Cur them in a humid environment with a temperature of 45℃ and a humidity of not less than 90% for 4 hours to obtain the blanks.

[0069] 4) Place the green body obtained in step 3) in an autoclave and cure it under constant pressure for 6 hours at 160℃ saturated steam pressure to obtain crack-resistant and easy-to-demold fiber cement board products.

[0070] 5) The crack-resistant and easy-to-demold fiber cement board product obtained in step 4) is dried to reduce its moisture content to less than 10 wt%, thus obtaining the crack-resistant and easy-to-demold fiber cement board.

[0071] Example 4:

[0072] This embodiment provides a crack-resistant, easy-to-demold, non-adhesive fiber cement board, comprising the following components by weight: 50 parts cement, 50 parts quartz sand, 3 parts quartz powder, 3 parts silica fume, 0.5 parts bentonite, 3 parts mica powder, 2 parts wollastonite, 0.3 parts microfibrillated fiber, 0.3 parts HPMC, and 7 parts pulp.

[0073] The cement used is ordinary Portland cement; the SiO2 content in the quartz sand is >90wt%, and the residue on a 180-mesh sieve is less than 1wt%; the SiO2 content in the quartz powder is >95wt%, and the residue on an 800-mesh sieve is less than 0.5wt%; the SiO2 content in the microsilica powder is >85wt%, and the specific surface area of ​​the microsilica powder is between 15,000 and 35,000 m². 2 / kg; the SiO2 content in bentonite is >70wt%, and the Al2O3 content is >10wt%; the SiO2 content in mica powder is ≤60wt%, and the residue on a 400-mesh sieve of mica powder is less than 1wt%; the SiO2 content in wollastonite is ≥45wt%, and the residue on a 200-mesh sieve of wollastonite is less than 0.5wt%; the solid content of the pulp is 3.0wt%; the microfibrillated fibers contain 7wt% lignin, 10wt% hemicellulose and 83wt% cellulose, and the diameter of the microfibrillated fibers is 1-100nm and the length is less than 20um.

[0074] The specific preparation process of this crack-resistant, easy-to-demold, and non-adhesive fiber cement board is as follows:

[0075] 1) Weigh the cement, quartz sand, quartz powder, microsilica powder, bentonite, mica powder, wollastonite, and HPMC according to the designed dosage and put them into the mixer to mix evenly. Then mix the mixed powder, microfibrillated fiber, pulp, and water together to obtain a slurry with a concentration of 14%.

[0076] 2) The slurry obtained in step 1) is evenly spread onto the felt through a headbox and then filtered to form a wet blank;

[0077] 3) Stack, press and hold the wet blanks obtained in step 2), and then place them in a pre-curing box. Cur them in a humid environment with a temperature of 45℃ and a humidity of not less than 90% for 4 hours to obtain the blanks.

[0078] 4) Place the green body obtained in step 3) in an autoclave and cure it under constant pressure for 6 hours at 160℃ saturated steam pressure to obtain crack-resistant and easy-to-demold fiber cement board products.

[0079] 5) The crack-resistant and easy-to-demold fiber cement board product obtained in step 4) is dried to reduce its moisture content to less than 10 wt%, thus obtaining the crack-resistant and easy-to-demold fiber cement board.

[0080] Comparative example:

[0081] This comparative example uses the same slurry process as the above-mentioned embodiments to prepare fiber cement boards, so as to ensure that the comparative example and the embodiments are consistent in molding process. Ordinary fiber cement boards generally only include cement, quartz sand, wollastonite and fiber, and the fiber in the steam curing system is mostly pulp fiber. Therefore, the fiber cement board of this comparative example includes the following components by weight: 50 parts cement, 56 parts quartz sand, 7 parts pulp and 2 parts wollastonite.

[0082] The physical and mechanical properties of the fiber cement boards prepared in Examples 1 to 4 and the comparative examples were tested, and the results are shown in Table 1.

[0083] Table 1:

[0084]

[0085] As shown in Table 1, among the fiber cement boards prepared using the same slurry molding process, the fiber cement board produced by this invention exhibits higher flexural strength, lower porosity, higher impact strength, and lower moisture expansion rate. Furthermore, its weather resistance test demonstrates that the fiber cement board of this invention maintains its integrity after 200 freeze-thaw cycles, and its flexural strength ratio after 100 freeze-thaw cycles is 90.55%–92.67%. These physical and mechanical properties significantly exceed the requirements for fiber cement boards in JC / T412.1-2018. Moreover, the optimized formula design gives the fiber cement board easy demolding, crack resistance, and non-adhesion characteristics. In contrast, the fiber cement board in the comparative example uses a common fiber cement board formula with a single raw material composition and fewer reaction products. Therefore, the board exhibits lower flexural strength, higher porosity, lower impact strength, and higher moisture expansion rate. Combined with the weather resistance test data, this board cannot meet the requirements for exterior wall panels under extreme climates, and it is prone to adhesion and exhibits numerous cracks.

[0086] Example 5:

[0087] This embodiment investigated the difference in effects of varying ratios of calcareous to siliceous materials in fiber cement boards. Three experimental groups (A, B, and C) were designed for comparison. Group A used the raw material composition formula of the fiber cement exterior wall panel in Example 4 above, specifically: 50 parts cement, 50 parts quartz sand, 3 parts quartz powder, 3 parts silica fume, 0.5 parts bentonite, 3 parts mica powder, 2 parts wollastonite, 0.3 parts microfibrillated fiber, 0.3 parts HPMC, and 7 parts pulp. Group B used a calcareous to silica fume ratio of 0.8, specifically: 50 parts cement, 56.5 parts quartz sand, 3 parts quartz powder, 3 parts silica fume, 0.5 parts bentonite, 3 parts mica powder, 2 parts wollastonite, 0.3 parts microfibrillated fiber, and HPMC. 0.3 parts cement, 7 parts pulp; Group C uses calcareous materials:siliceous materials = 1.1, that is, the formula of Group B is as follows: 50 parts cement, 39.5 parts quartz sand, 3 parts quartz powder, 3 parts microsilica powder, 0.5 parts bentonite, 3 parts mica powder, 2 parts wollastonite, 0.3 parts microfiber, 0.3 parts HPMC, 7 parts pulp; In this embodiment, the preparation process of fiber cement boards of Group A, Group B and Group C is the same as that of Example 4 above.

[0088] The physical and mechanical properties of the fiber cement boards prepared by groups A, B and C in this embodiment were tested, and the results are shown in Table 2.

[0089] Table 2:

[0090]

[0091] As shown in Table 2, among the boards prepared using the same slurry forming process, the fiber cement board produced by this invention exhibits higher flexural strength, lower porosity, higher impact strength, and lower moisture expansion rate. Furthermore, its weather resistance test demonstrates that the fiber cement board of this invention maintains its integrity after 200 freeze-thaw cycles, and its flexural strength ratio after 100 freeze-thaw cycles is 92.67%. All physical and mechanical properties significantly exceed the requirements for fiber cement flat sheets in JC / T412.1-2018. In contrast, the fiber cement board formulations in groups B and C, with calcareous and siliceous material ratios of 0.8 and 1.1 respectively, produce significantly different product contents compared to the formulation in group A. Consequently, their performance differs from that of the fiber cement board produced by group A. The boards produced by groups B and C have lower flexural strength, higher porosity, higher moisture expansion rate, and inferior weather resistance compared to this invention.

[0092] Example 6:

[0093] This embodiment investigated the differences in effects of HPMC and silica fume, and bentonite and silica fume, on fiber cement boards. Three experimental groups (A, B, and C) were designed for comparison. Group A used the raw material composition formula of the fiber cement exterior wall panel in Example 4 above, i.e., the Group A formula is as follows: 50 parts cement, 50 parts quartz sand, 3 parts quartz powder, 3 parts silica fume, 0.5 parts bentonite, 3 parts mica powder, 2 parts wollastonite, 0.3 parts microfiber, 0.3 parts HPMC, and 7 parts pulp. Group B lacked HPMC and silica fume; the remaining components were the same as Group A. The formulations of Group A, B, and C are identical: 50 parts cement, 50 parts quartz sand, 3 parts quartz powder, 3 parts silica fume, 0.5 parts bentonite, 3 parts mica powder, 2 parts wollastonite, 0.3 parts microfiber, and 7 parts pulp. Group C lacks bentonite and silica fume, but the remaining components are identical to Group A: 50 parts cement, 53 parts quartz sand, 3 parts quartz powder, 3 parts mica powder, 2 parts wollastonite, 0.3 parts microfiber, 0.3 parts HPMC, and 7 parts pulp. The preparation process of the fiber cement boards for Groups A, B, and C in this embodiment is consistent, and is the same as in Example 4 above.

[0094] The physical and mechanical properties of the fiber cement boards prepared by groups A, B and C in this embodiment were tested, and the results are shown in Table 3.

[0095] Table 3:

[0096]

[0097] As shown in Table 3, among the boards prepared using the same slurry molding process, the fiber cement board prepared by this invention has high flexural strength, low porosity, high impact strength, and low moisture expansion rate. Furthermore, its weather resistance test shows that the fiber cement board of this invention maintains its integrity after 200 freeze-thaw cycles, and its flexural strength ratio after 100 freeze-thaw cycles is 92.67%. Its physical and mechanical properties are significantly higher than the requirements for fiber cement flat sheets in JC / T412.1-2018. Moreover, the optimized formula design gives the fiber cement board the characteristics of easy demolding, crack resistance, and non-adhesion. Group B, lacking HPMC and microsilica, experienced exacerbated plastic shrinkage cracking and lower early strength even with bentonite alone, leading to plate sticking and post-reactor cracking. Group C, also lacking bentonite and microsilica, had reduced overall plate density and higher alkalinity, resulting in more severe fiber degradation after reactor fermentation. Therefore, the plates obtained from Groups B and C had lower flexural strength, higher porosity, higher moisture swelling rate, and inferior weather resistance compared to this invention.

[0098] Example 7:

[0099] This embodiment investigated the effects of microfibers and silica fume on the performance of fiber cement boards. Four experimental groups (A, B, C, and D) were designed for comparison. Group A used the raw material composition formula of the fiber cement board in Example 4 above, specifically: 50 parts cement, 50 parts quartz sand, 3 parts quartz powder, 3 parts silica fume, 0.5 parts bentonite, 3 parts mica powder, 2 parts wollastonite, 0.3 parts microfibers, 0.3 parts HPMC, and 7 parts pulp. Group B lacked microfibers, but the remaining components were the same as Group A, specifically: 50 parts cement, 50 parts quartz sand, 3 parts quartz powder, 3 parts silica fume, 0.5 parts bentonite, 3 parts mica powder, 2 parts wollastonite, and 7 parts HPMC. Group A contains 0.3 parts cement, 7 parts pulp; Group C lacks silica fume, but the remaining components are the same as Group A, i.e., the formula of Group C is as follows: 50 parts cement, 50 parts quartz sand, 3 parts quartz powder, 0.5 parts bentonite, 3 parts mica powder, 2 parts wollastonite, 0.3 parts microfiber, 0.3 parts HPMC, and 7 parts pulp; Group D lacks microfiber and silica fume, i.e., the formula of Group D is as follows: 50 parts cement, 50 parts quartz sand, 3 parts quartz powder, 0.5 parts bentonite, 3 parts mica powder, 2 parts wollastonite, 0.3 parts HPMC, and 7 parts pulp; In this embodiment, the preparation process of fiber cement boards of Groups A, B, C, and D is the same as in Example 4 above.

[0100] The physical and mechanical properties of the fiber cement boards prepared by groups A, B, C and D in this embodiment were tested, and the results are shown in Table 4.

[0101] Table 4:

[0102]

[0103] As shown in Table 4, among the boards prepared using the same slurry molding process, the fiber cement board prepared by this invention has high flexural strength, low porosity, high impact strength, and low moisture expansion rate. Furthermore, its weather resistance test shows that the fiber cement board of this invention maintains its integrity after 200 freeze-thaw cycles, and its flexural strength ratio after 100 freeze-thaw cycles is 92.67%. Its physical and mechanical properties are significantly higher than the requirements for fiber cement flat sheets in JC / T412.1-2018. Moreover, the optimized formula design gives the fiber cement board easy demolding, crack resistance, and non-adhesion characteristics. Group B, lacking microfibrillated fibers, exhibits poor crack resistance and less fiber protection than Group A. Groups C and D, even with bentonite present, show low early strength, leading to board adhesion. Group D, lacking microfibrillated fibers and silica fume, suffers from reduced overall board density, higher system alkalinity, decreased fiber adhesion, and severe fiber damage after autoclaving. Consequently, the boards produced by Groups B, C, and D have lower flexural strength, higher porosity, higher moisture swelling rate, and inferior weather resistance compared to this invention, exhibiting at least one of the following phenomena: board adhesion, sticking, or cracking.

[0104] In summary, this crack-resistant, easy-to-demold, non-adhesive fiber cement board features low curing temperature, short curing time, energy saving, environmental friendliness, low overall cost, high density, and non-stick properties upon demolding. After removal from the autoclave, it exhibits no adhesion, no cracks, and excellent stability. It also demonstrates outstanding performance in freeze-thaw cycle weathering tests, solving the thorny problems of board sticking and adhesion on the production line. This fully utilizes the production line's capacity, improves the product qualification rate, and ensures that the produced boards can fully meet the needs of exterior wall panels in extreme climate zones.

[0105] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A crack-resistant, easy-to-demold, non-adhesive fiber cement board, characterized in that, The preparation materials include the following: calcareous materials, siliceous materials, bentonite, mica powder, wollastonite, microfibrillated fibers, HPMC and pulp, wherein the calcareous materials are cement, and the siliceous materials include quartz sand, quartz powder and microsilica powder, and the mass ratio of the calcareous materials to the siliceous materials is 0.9 to 1.

0.

2. The crack-resistant, easy-to-demold, non-adhesive fiber cement board as described in claim 1, characterized in that, The raw materials include, by weight, the following: 45-50 parts cement, 31-50 parts quartz sand, 3-7 parts quartz powder, 3-7 parts microsilica, 0.5-1.5 parts bentonite, 1-5 parts mica powder, 2-4 parts wollastonite, 0.2-0.5 parts microfibrillated fiber, 0.3-0.8 parts HPMC, and 6-8 parts pulp.

3. The crack-resistant, easy-to-demold, non-adhesive fiber cement board as described in claim 1 or 2, characterized in that, The quartz sand contains >90 wt% SiO2, and the residue on an 180-mesh sieve is less than 1 wt%; the quartz powder contains >95 wt% SiO2, and the residue on an 800-mesh sieve is less than 0.5 wt%; the silica powder contains >85 wt% SiO2, and the specific surface area of ​​the silica powder is 15,000–35,000 m². 2 / kg.

4. The crack-resistant, easy-to-demold, non-adhesive fiber cement board as described in claim 1 or 2, characterized in that, The bentonite contains SiO2 content >70wt% and Al2O3 content >10wt%.

5. The crack-resistant, easily demolded, non-adhesive fiber cement board as described in claim 1 or 2, characterized in that, The mica powder contains ≤60wt% SiO2 and has a residue of less than 1wt% on a 400-mesh sieve.

6. The crack-resistant, easily demolded, non-adhesive fiber cement board as described in claim 1 or 2, characterized in that, The SiO2 content in the wollastonite is ≥45wt%, and the residue of the wollastonite on a 200-mesh sieve is less than 0.5wt%.

7. The crack-resistant, easily demolded, non-adhesive fiber cement board as described in claim 1 or 2, characterized in that, The microfibrillated fibers contain 5-8 wt% lignin, 9-12 wt% hemicellulose, and 80-86 wt% cellulose; the microfibrillated fibers have a diameter of 1-100 nm and a length of less than 20 μm.

8. The crack-resistant, easily demolded, non-adhesive fiber cement board as described in claim 1 or 2, characterized in that, The pulp has a solid content of 3.0 wt%.

9. The method for preparing the crack-resistant, easily demolded, non-adhesive fiber cement board according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Weigh the cement, quartz sand, quartz powder, microsilica powder, bentonite, mica powder, wollastonite, and HPMC according to the designed dosage and put them into a mixer to mix evenly. Then mix the mixed powder with microfibrillated fiber, pulp, and water evenly to obtain a slurry with a concentration of 13-17%. S2. The obtained slurry is evenly spread onto the felt through the headbox and filtered to form a wet blank. S3. The prepared wet blank is subjected to moisture curing and autoclaving to obtain the initial product; S4. The obtained initial product is dried to reduce its moisture content to less than 10 wt%, thus obtaining crack-resistant, easy-to-demold, and non-adhesive fiber cement board.

10. The method for preparing crack-resistant, easily demolded, non-adhesive fiber cement board as described in claim 9, characterized in that, In S3, the process conditions for moisture curing are: moisture curing temperature 45-60℃, humidity not less than 90%, and moisture curing time 4-6h; the process conditions for autoclaving are: constant pressure curing at 160-190℃ saturated vapor pressure for 6-10h.

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