A fiber cement board using short cotton linter fibers as a substitute for wood pulp fibers and its preparation method

Abstract

This invention belongs to the field of fiber cement board technology, specifically relating to a fiber cement board in which short cotton fibers replace wood pulp fibers and its preparation method. The fiber cement board prepared by using short cotton fibers to replace wood pulp fibers not only significantly reduces production costs, reduces the consumption of forest resources and the impact on the environment, but also maintains flexural strength comparable to traditional products, meeting the high standards of the construction industry.

Description

Technical Field

[0001] This invention belongs to the field of fiber cement board technology, specifically relating to a fiber cement board in which short cotton fibers replace wood pulp fibers and its preparation method. Background Technology

[0002] In the construction industry, fiber-reinforced cement boards and fiber-reinforced calcium silicate boards are widely used building materials. Traditionally, the production formulas for these boards contain key components such as calcareous materials (cement, lime, carbide slurry, etc.), siliceous materials (quartz sand, silica fume, diatomaceous earth, fly ash, etc.), and fibers (wood pulp fibers, waste paper fibers, glass fibers, PVA fibers, etc.). Among these, high-quality wood pulp fibers suitable for fiber-reinforced cement board production are mostly derived from coniferous tree species and are widely used due to their excellent reinforcing properties.

[0003] However, high-quality wood pulp fiber often needs to be imported, and its price has risen significantly, leading to an unstable supply chain and a substantial impact on continuous production. Therefore, finding a lower-cost, less environmentally impactful alternative to wood fiber has become a top priority. Summary of the Invention

[0004] To address the problems raised in the background art, the present invention provides a fiber cement board in which short cotton fibers replace wood pulp fibers and a method for preparing the same.

[0005] The technical solution of the present invention is as follows:

[0006] This invention provides a fiber cement board in which short cotton fibers replace wood pulp fibers. The raw materials for preparing the fiber cement board include the following substances in weight percentage:

[0007] Siliceous materials 20%-80%, calcareous materials 10%-75%, short cotton fibers 1%-7%, wood pulp fibers 1%-9%, polyvinyl alcohol fibers 0-4%, additives and fillers 0-30%;

[0008] The fiber cement board prepared from the aforementioned raw materials has a density of 1.29-1.68 kg / m³. 3 Its flexural strength is 9.8-19.97 MPa.

[0009] Furthermore, the raw materials of the fiber cement board include the following substances in weight percentage:

[0010] Siliceous materials 48%-78%, calcareous materials 11%-41%, short cotton fibers 1%-4%, wood pulp fibers 1%-5%, polyvinyl alcohol fibers 0-3%, and additives and fillers 0-3%.

[0011] This invention also provides a method for preparing fiber cement board using short cotton linter fibers as a substitute for wood pulp fibers, comprising the following steps:

[0012] (1) Mix siliceous materials, calcareous materials, short cotton fibers, wood pulp fibers, polyvinyl alcohol fibers, and additives and fillers to obtain the first slurry;

[0013] (2) The first slurry is dehydrated and then subjected to molding treatment to obtain the first blank;

[0014] (3) After the first billet is stacked to the preset height, it is pressed and dehydrated to obtain the first slab;

[0015] (4) The first slab is pre-cured, demolded, cured and dried in sequence to obtain fiber cement board.

[0016] Furthermore, the ratio of short cotton linter fiber to wood pulp fiber is 0.65-1:1.

[0017] In step (1), the solid content concentration of the first slurry is 15%-16%.

[0018] In step (2), the thickness of the first blank is 9.4-9.6 mm.

[0019] In step (3), the water is dehydrated by pressing at a pressure of 15-75 MPa for 3-10 minutes.

[0020] In step (4), the pre-curing is carried out at a temperature of 40-45℃ for 10-14 hours.

[0021] In step (4), the curing is either steam curing or moist curing. The temperature for steam curing is 180-185℃ and the time is 8-8.5h; the time for moist curing is 27-28 days.

[0022] In step (4), the drying process is carried out at a temperature of 90-95℃ for 2-3 hours.

[0023] Beneficial effects

[0024] This invention uses short cotton fibers to replace part of the wood pulp fibers to prepare fiber cement boards, which not only significantly reduces production costs, reduces the consumption of forest resources and the impact on the environment, but also maintains flexural strength comparable to traditional products, meeting the high standards of the construction industry. Detailed Implementation

[0025] The following examples are intended to illustrate the present invention, and not to further limit the invention.

[0026] This invention provides a fiber cement board in which short cotton fibers replace wood pulp fibers. The raw materials for preparing the fiber cement board include the following substances in weight percentage:

[0027] Siliceous materials 20%-80%, calcareous materials 10%-75%, short cotton fibers 1%-7%, wood pulp fibers 1%-9%, polyvinyl alcohol fibers 0-4%, and additives and fillers 0-30%.

[0028] Wood pulp fiber costs approximately 5,000 yuan per ton, while cotton fiber costs approximately 2,500-3,000 yuan per ton. Cotton fiber is used instead of wood pulp fiber in fiber cement boards to reduce production costs.

[0029] The calcareous materials can be cement, lime, or calcium carbide sludge; the siliceous materials can be quartz sand, silica fume, diatomaceous earth, or fly ash. Short cotton fibers can be derived from cotton lint waste generated during industrial production. To ensure proper pulping, pretreatment can be performed, such as soaking and dispersing with production water. This production water is a solution used in the production of fiber cement boards, primarily composed of calcium hydroxide, with a pH value typically above 12. Additives and fillers include flocculants, defoamers, color pastes, and sanding powder.

[0030] To further ensure the performance of the fiber cement board, such as density and flexural strength, preferably, the raw materials of the fiber cement board include the following substances in weight percentage:

[0031] Siliceous materials 48%-78%, calcareous materials 11%-41%, short cotton fibers 1%-4%, wood pulp fibers 1%-5%, polyvinyl alcohol fibers 0-3%, and additives and fillers 0-3%.

[0032] Specifically, the fiber cement board is prepared through the following steps:

[0033] (1) Mix siliceous materials, calcareous materials, short cotton fibers, wood pulp fibers, polyvinyl alcohol fibers, and additives and fillers to obtain the first slurry.

[0034] For example, after the raw materials are measured according to the set formula ratio, they are mixed in a homogenizer to achieve a solid content concentration of 15%-16% in the first slurry to meet production requirements.

[0035] The first slurry is placed or pumped into the slurry storage tank, and then fed into the headbox by gravity or pumping for production.

[0036] According to actual needs, a vibrating screen and grinding equipment can be added to further process and refine the first slurry before use.

[0037] (2) The first slurry is dehydrated under vacuum and then molded to obtain the first blank.

[0038] Specifically, as the first slurry travels forward through the continuously running blanket of the slurry machine (for example, at a speed of 85 m / min), it is dehydrated by the vacuum system and wound into a blank on the forming cylinder. When the thickness of the blank reaches the set requirement, it is pulled off.

[0039] Preferably, in step (2), the thickness of the first blank is 9.4-9.6 mm.

[0040] (3) After the first billet is stacked to the preset height, it is pressed and dehydrated to obtain the first slab.

[0041] During the stacking process, after the first blank torn off the forming cylinder is trimmed, it is neatly stacked on the pad or trolley, one plate and one mold at a time. For example, the stacking height should not exceed 1.1m. The material edges and unqualified waste blanks are recycled.

[0042] The stacked slabs are sent to the press for pressing and dehydration according to the process requirements. Preferably, in step (3), the pressing and dehydration pressure is 15-75MPa and the continuous pressing time is 3-10min, and a certain amount of water is discharged.

[0043] (4) The first slab is pre-cured, demolded, cured and dried in sequence to obtain fiber cement board.

[0044] First, the first slab is sent into a pre-curing kiln for pre-curing. Preferably, the pre-curing temperature is 40-45℃ and the time is 10-14h.

[0045] Then, the pre-cured slabs are separated from the steel formwork. The formwork is then evenly brushed with an environmentally friendly release agent and returned to the stacking area for recycling. The slabs are then stacked on trolleys according to process requirements and sent to the curing stage.

[0046] The curing process includes either autoclaving or moisture-retaining curing. Autoclaving can be carried out in an autoclave at a temperature of 180-185℃ for 8-8.5 hours, with a heating time of 2 hours and a cooling time of 2 hours. Moisture-retaining curing can be carried out by covering the slab with a felt with a certain water-retaining capacity for 27-28 days.

[0047] Finally, the cured boards are dried. In step (4), the drying temperature is 90-95℃ and the time is 2-3 hours to ensure that the moisture content is less than 8.5%. After drying, the thickness is tested and the boards are sorted and stacked.

[0048] In addition, it also includes cutting and sanding the fiber cement board, mainly cutting the edges and corners, sanding the thickness to 8mm, and sanding the surface to 120 grit to ensure that the surface is flat and flawless.

[0049] In the production process of fiber cement board, the production water is used not only to treat the fiber cement board but also to treat short cotton fibers. To meet actual production needs, based on the configured pH meter, the tap water pipeline and the pH adjustment solution pipeline are equipped with proportional regulating valves to adjust the ratio and ensure a timely supply of production water.

[0050] The fiber cement board has a density of 1.29-1.68 kg / m³. 3 Its flexural strength is 9.8-19.97 MPa.

[0051] This invention uses short cotton fibers to replace wood pulp fibers to prepare fiber cement boards, which not only significantly reduces production costs and the consumption of forest resources and environmental impact, but also maintains flexural strength comparable to traditional products, meeting the high standards of the construction industry.

[0052] Example 1

[0053] (1) Mix 48% siliceous material, 41% calcareous material, 3% short cotton fiber, 5% wood pulp fiber, and 3% additives and fillers in a homogenizer for 15 minutes to obtain the first slurry.

[0054] (2) The first slurry is pumped to the slurry storage tank, diluted to a solid content concentration of 16%, pumped into the headbox, dehydrated by the vacuum system, and wound into a blank on the forming cylinder. When the thickness of the blank reaches the set requirement, it is pulled off to obtain the first blank. The thickness of the first blank is 9.5 mm.

[0055] (3) After the first billet is stacked to a height of no more than 1.1m, it is pressed and dehydrated to obtain the first slab. The pressing and dehydration is carried out at a pressure of 15MPa for a duration of 3min.

[0056] (4) The first slab is pre-cured (temperature 41℃, time 12h), demolded, autoclaved (temperature 180℃, time 8.5h, heating time 2h, cooling time 4h), and dried (temperature 90℃, time 2.5h) to obtain fiber cement board.

[0057] Example 2

[0058] (1) Mix 48% siliceous material, 41% calcareous material, 4% short cotton fiber, 4% wood pulp fiber, and 3% additives and fillers in a homogenizer for 15 minutes to obtain the first slurry.

[0059] (2) The first slurry is pumped to the slurry storage tank, diluted to a solid content concentration of 16%, pumped into the headbox, dehydrated by the vacuum system, and wound into a blank on the forming cylinder. When the thickness of the blank reaches the set requirement, it is pulled off to obtain the first blank. The thickness of the first blank is 9.5 mm.

[0060] (3) After the first billet is stacked to a height of no more than 1.1m, it is pressed and dehydrated to obtain the first slab. The pressing and dehydration is carried out at a pressure of 15MPa for a duration of 3min.

[0061] (4) The first slab is pre-cured (temperature 41℃, time 12h), demolded, autoclaved (temperature 180℃, time 8.5h, heating time 2h, cooling time 4h), and dried (temperature 90℃, time 2.5h) to obtain fiber cement board.

[0062] Example 3

[0063] (1) Mix 78% siliceous material, 11% calcareous material, 1% short cotton fiber, 2% wood pulp fiber, 3% polyvinyl alcohol fiber, and 5% additives and fillers in a homogenizer for 15 minutes to obtain the first slurry.

[0064] (2) The first slurry is pumped to the slurry storage tank, diluted to a solid content concentration of 16%, pumped into the headbox, dewatered by the vacuum system, and wound into a blank on the forming cylinder. When the thickness of the blank reaches the set requirement, it is pulled off to obtain the first blank. The thickness of the first blank is 9.8 mm.

[0065] (3) After the first billet is stacked to a height of no more than 1.1m, it is pressed and dehydrated to obtain the first slab. The pressing and dehydration is carried out at a pressure of 75MPa for a duration of 10min.

[0066] (4) The first slab is pre-cured (temperature 41℃, time 12h), demolded, and moisturized (28 days) to obtain fiber cement board.

[0067] Example 4

[0068] (1) Mix 78% siliceous material, 11% calcareous material, 2% short cotton fiber, 1% wood pulp fiber, 3% polyvinyl alcohol fiber, and 5% additives and fillers in a homogenizer for 15 minutes to obtain the first slurry.

[0069] (2) The first slurry is pumped to the slurry storage tank, diluted to a solid content concentration of 16%, pumped into the headbox, dewatered by the vacuum system, and wound into a blank on the forming cylinder. When the thickness of the blank reaches the set requirement, it is pulled off to obtain the first blank. The thickness of the first blank is 9.8 mm.

[0070] (3) After the first billet is stacked to a height of no more than 1.1m, it is pressed and dehydrated to obtain the first slab. The pressing and dehydration is carried out at a pressure of 75MPa for a duration of 10min.

[0071] (4) The first slab is pre-cured (temperature 41℃, time 12h), demolded, and moisturized (27 days) to obtain fiber cement board.

[0072] Comparative Example 1

[0073] Compared with Example 1, no short cotton fibers were added in step (1), and the amount of wood pulp fiber added was 8%. The remaining operations were the same as in Example 1, using the same raw materials and amounts as in Example 1.

[0074] Comparative Example 2

[0075] Compared with Example 3, no short cotton fibers were added in step (1), and the amount of wood pulp fiber added was 3%. The remaining operations were the same as in Example 3, using the same raw materials and amounts as in Example 3.

[0076] In the above embodiments and comparative examples, the siliceous material is quartz sand, and the calcareous material is cement. Furthermore, the short cotton fibers in the embodiments of this invention are all degreased before preparing the fiber cement board. The specific degreasing method is as follows: Cotton fibers with an oil content of 3%-4% (actually measured) are fed into a crusher, and first-stage fiber cement board production water is added. The amount of first-stage fiber cement board production water added is 2.5 times the weight of the cotton fibers to be treated. The crusher is crushed at 600 rpm for 15 minutes. The crushed cotton fibers are then placed in a circulating water tank and mixed at a ratio of 1:4.5 (weight of crushed cotton fibers to amount of first-stage fiber cement board production water). The pH of the first-stage fiber cement board production water is 11.5, and the temperature is 35℃. Stirring is performed every 30 minutes for 5 minutes each time. The pH value is checked after each stirring. If it is lower than 11.0, third-stage fiber cement board production water is added, and the pH of the third-stage fiber cement board production water is not lower than 12. When the total reaction time reaches 6 hours, the cotton lint fibers no longer show obvious signs of floating, and degreasing is complete. Since both short cotton lint fibers and wood pulp fibers are lightweight materials, the degreased short cotton lint fibers can be premixed with wood pulp fibers (all or at least part) before being injected into the homogenizer. Premixing can be achieved by a combination of high-pressure air delivery and swirling stirring. The wood pulp fibers are fed into the swirled short cotton lint slurry under high-pressure air delivery and then sent to the homogenizer together after stirring.

[0077] Experimental results

[0078] The fiber cement boards prepared in Examples 1-4, Comparative Example 1, and Comparative Example 2 were tested for density and flexural strength according to the test methods in GB / T 7019-2014. The test results are shown in Table 1.

[0079] Table 1 Test Results

[0080]

[0081] As shown in Table 1, compared with Comparative Example 1 and Comparative Example 2, the fiber cement boards prepared using this application in Examples 1-4 maintain flexural strength comparable to traditional products, meeting the high standards required by the construction industry.

Claims

1. A method for preparing fiber cement board using short cotton linter fibers as a substitute for wood pulp fibers, characterized in that, The raw materials for preparing the fiber cement board include the following substances in weight percentage: Siliceous materials 30%-80%, calcareous materials 10%-50%, short cotton fibers 1%-7%, wood pulp fibers 1%-9%, polyvinyl alcohol fibers 3-4%, additives and fillers 0-30%; The fiber cement board prepared from the aforementioned raw materials has a density of 1.29-1.68 kg / m³ and a flexural strength of 9.8-19.97 MPa. The fiber cement board is prepared through the following steps: (1) Mix siliceous materials, calcareous materials, short cotton fibers, wood pulp fibers, polyvinyl alcohol fibers, and additives and fillers to obtain the first slurry; (2) The first slurry is dehydrated and then subjected to molding treatment to obtain the first blank; (3) After the first billet is stacked to the preset height, it is pressed and dehydrated to obtain the first slab; (4) The first slab is pre-cured, demolded, cured and dried in sequence to obtain fiber cement board; The short cotton fibers undergo degreasing treatment before being used to prepare fiber cement boards. The specific degreasing method is as follows: Cotton fibers with an oil content of 3%-4% originating from industrial cotton lint solid waste are fed into a crusher. First-stage fiber cement board production water is added, with the amount added being 2.5 times the weight of the cotton fibers. The crushed cotton fibers are then placed in a circulating water tank and mixed at a ratio of 1:4.5 (weight of crushed cotton fibers to amount of first-stage fiber cement board production water). The pH of the first-stage fiber cement board production water is 11.5, and the temperature is 35℃. Stirring is performed every 30 minutes for 5 minutes each time. After each stirring, the pH value is checked. If it is lower than 11.0, third-stage fiber cement board production water is added, with the pH of the third-stage fiber cement board production water not lower than 12. When the total reaction time reaches 6 hours, the cotton fibers no longer show obvious signs of floating, and degreasing is complete. After degreasing, the short cotton linters are premixed with wood pulp fibers before being injected into the homogenizer. The premixing is carried out by a combination of high-pressure air delivery and swirling stirring. The wood pulp fibers are sent into the short cotton linter pulp that is being swirled and stirred under high-pressure gas, and then sent to the homogenizer together.

2. The method for preparing fiber cement board using short cotton linter fibers to replace wood pulp fibers according to claim 1, characterized in that, The ratio of short cotton linter fiber to wood pulp fiber is 0.65-1:

1.

3. The method for preparing fiber cement board using short cotton linter fibers to replace wood pulp fibers according to claim 1, characterized in that, In step (1), the solid content concentration of the first slurry is 15%-16%.

4. The method for preparing fiber cement board using short cotton linter fibers to replace wood pulp fibers according to claim 1, characterized in that, In step (2), the thickness of the first blank is 9.4-9.6 mm.

5. The method for preparing fiber cement board using short cotton linter fibers to replace wood pulp fibers according to claim 1, characterized in that, In step (3), the water is dehydrated by pressing at a pressure of 15-75 MPa for 3-10 minutes.

6. The method for preparing fiber cement board using short cotton linter fibers to replace wood pulp fibers according to claim 1, characterized in that, In step (4), the pre-curing is carried out at a temperature of 40-45℃ for 10-14 hours.

7. The method for preparing fiber cement board using short cotton linter fibers to replace wood pulp fibers according to claim 1, characterized in that, In step (4), the maintenance is moisturizing maintenance, and the moisturizing maintenance time is 27-28 days.

8. The method for preparing fiber cement board using short cotton linter fibers to replace wood pulp fibers according to claim 1, characterized in that, In step (4), the drying process is carried out at a temperature of 90-95℃ for 2-3 hours.

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