Fiber cement board doped with defatted short cotton linter fiber and preparation method thereof

Abstract

The present invention belongs to the technical field of fiber cement boards, and specifically relates to a fiber cement board doped with defatted short cotton linter fibers and a preparation method thereof. Cotton linter solid waste is used as one of the raw materials of the fiber cement board, thereby achieving effective utilization of the cotton linter solid waste, reducing dependence on wood fiber, and reducing production costs. At the same time, during the production process of the fiber cement board, the clean water produced by the fiber reinforced cement board production is used to achieve degreasing treatment of the cotton linter solid waste, avoiding the use of a large amount of strong alkaline chemical agents, thereby improving resource utilization and reducing the impact on the environment. The obtained fiber cement board has good flexural strength.

Description

Technical Field

[0001] The invention belongs to the technical field of fiber cement boards, and particularly relates to a fiber cement board doped with defatted short cotton linter fibers and a preparation method thereof. Background Art

[0002] Cotton lint waste generated during industrial production typically contains over 40% dust and other impurities. This waste is not effectively utilized, not only taking up significant space but also potentially causing secondary environmental pollution during processing, such as the use of large amounts of strong alkaline chemicals, which wastes valuable resources. Furthermore, the traditional production of fiber cement board relies heavily on wood fiber, which not only increases production costs but also negatively impacts the environment. This is especially true given that wood fiber is primarily imported, making the supply chain vulnerable to import and export cycles, hindering the development of the domestic industry. Summary of the Invention

[0003] In order to solve the problems raised by the background technology, the present invention utilizes cotton linter solid waste, reduces dependence on imported wood fiber, and reduces production costs. At the same time, in the production process of fiber cement board, it realizes the degreasing treatment of cotton linter solid waste, improves resource utilization, and reduces the impact on the environment. A fiber cement board doped with defatted short cotton linter fiber and a preparation method thereof are provided.

[0004] The technical solutions of the present invention are as follows:

[0005] The present invention provides a fiber cement board doped with defatted short cotton linter fibers. The fiber raw materials in the fiber cement board include defatted short cotton linter fibers and wood pulp fibers. The defatted short cotton linter fibers account for 1%-4% and the wood pulp fibers account for 1%-5% based on the total weight of the fiber cement board. The defatted short cotton linter fibers are prepared by soaking cotton linter solid waste in clean water during the production of fiber reinforced cement boards.

[0006] The degreased short cotton linter fiber is prepared by the following steps:

[0007] (1) Wet crushing: Add clean water from fiber reinforced cement board production and cotton lint fibers after dust removal from cotton lint solid waste screening into the crushing equipment for crushing and cutting;

[0008] (2) Soaking and degreasing: The crushed cotton lint fibers are soaked in clean water to obtain defatted short cotton lint fibers.

[0009] The present invention also provides a method for preparing a fiber cement board doped with defatted short cotton linter fibers, wherein the fiber cement board is prepared by the following steps:

[0010] (1) Wet crushing: Add clean water from fiber reinforced cement board production and cotton lint fibers after dust removal from cotton lint solid waste screening into the crushing equipment for crushing and cutting;

[0011] (2) Soaking and degreasing: The crushed cotton lint fibers are soaked in clean water to obtain defatted short cotton lint fibers;

[0012] (3) Raw material pulping: mixing defatted short cotton linter fibers, wood pulp fibers, siliceous materials, calcareous materials, polyvinyl alcohol fibers, and auxiliary fillers to obtain a slurry;

[0013] (4) Molding: The slurry is dehydrated by the vacuum system as it moves forward through the continuously running felt of the slurry flow equipment, and is wound into a blank on the forming cylinder. When the blank reaches the preset thickness, it is pulled off;

[0014] (5) Stacking and pressing: Stack the torn blanks into slabs and press them for dehydration;

[0015] (6) Demolding and curing: The pressurized slab undergoes first curing, demoulding, second curing, and drying in sequence to obtain a fiber cement board.

[0016] In the step (2), the pH value of the clean water used for soaking the fiber reinforced cement board production is not less than 11.

[0017] In the step (2), the beating degree of the defatted short cotton linter fiber is greater than 13 and the wet weight is not less than 6.

[0018] In the step (4), the solid content of the slurry is 14%-16%.

[0019] In the step (5), the pressure for dehydration is 15-75 MPa and the time is 3-10 min.

[0020] In the step (6), the first curing is static curing or heating pre-curing, and the second curing is autoclaving curing or moisturizing curing.

[0021] The temperature of the heating pre-curing is 41-45° C. and the time is 12-14 hours; the temperature of the autoclaving curing is 180-185° C. and the time is 8-8.5 hours.

[0022] In the step (6), the drying temperature is 90-95° C. and the drying time is 2-3 hours.

[0023] Beneficial effects

[0024] The present invention uses cotton lint solid waste as one of the raw materials for fiber cement board, thereby achieving effective utilization of cotton lint solid waste, reducing dependence on wood fiber, and reducing production costs. At the same time, during the production process of fiber cement board, the clean water produced by fiber reinforced cement board production is used to degrease the cotton lint solid waste, avoiding the use of a large amount of strong alkaline chemicals, thereby improving resource utilization and reducing the impact on the environment. The obtained fiber cement board has good flexural strength. DETAILED DESCRIPTION

[0025] The following examples are intended to illustrate the present invention rather than to further limit the present invention.

[0026] The present invention provides a fiber cement board doped with defatted short cotton linter fibers. The fiber raw materials in the fiber cement board include defatted short cotton linter fibers and wood pulp fibers. The defatted short cotton linter fibers account for 1%-4% and the wood pulp fibers account for 1%-5% based on the total weight of the fiber cement board. The defatted short cotton linter fibers are prepared by soaking cotton linter solid waste in clean water during the production of fiber reinforced cement boards.

[0027] Compared with the prior art, which often uses wood pulp fiber as one of the important raw materials for the production of fiber cement boards, the present invention uses cotton linter solid waste as one of the raw materials for fiber cement boards, reducing dependence on wood fiber.

[0028] In addition, the raw materials of fiber cement board also include 48%-78% siliceous materials, 11%-41% calcareous materials, 0-3% polyvinyl alcohol fibers, and 1%-3% auxiliary fillers.

[0029] In addition, the defatted short cotton linter fiber is prepared by the following steps:

[0030] (1) Wet crushing: Add clean water from fiber reinforced cement board production and cotton lint fibers after dust removal from cotton lint solid waste screening into the crushing equipment for crushing and cutting;

[0031] (2) Soaking and degreasing: The crushed cotton lint fibers are soaked in clean water to obtain defatted short cotton lint fibers.

[0032] The production water is a solution with calcium hydroxide as the main component and a pH value of usually above 12 used in the production process of fiber cement boards. It is recycled water that can be used for production after being precipitated in a water storage tank to remove large particles of impurities.

[0033] The present invention also provides a method for preparing the fiber cement board doped with defatted short cotton linter fibers, wherein the fiber cement board is prepared by the following steps:

[0034] (1) Wet crushing: Add clean water from fiber reinforced cement board production and cotton lint fibers after dust removal from cotton lint solid waste screening into the crushing equipment for crushing and cutting. The crushing can be done to a specified length according to actual needs.

[0035] (2) Soaking and degreasing: The crushed cotton lint fibers are soaked in clean water to obtain defatted short cotton lint fibers.

[0036] The pH of the fresh water used for soaking the fiber-reinforced cement board production should preferably be no less than 11. The pH can be maintained by filtering and re-adding the fresh water currently used for soaking, or by automatically replenishing the fresh water based on pH monitoring. The total soaking time should be determined based on the mass of the crushed lint fibers, until the lint fibers no longer float within 40 minutes. During soaking, periodic stirring can be used to accelerate the crushing process. The fresh water can also be heated to shorten the degreasing time.

[0037] The present invention utilizes the clear water produced by the fiber reinforced cement board production process to achieve degreasing treatment of cotton lint solid waste during the fiber cement board production process, thereby avoiding the use of a large amount of strong alkaline chemical agents, thereby improving resource utilization and reducing impact on the environment.

[0038] Considering that there are still some cotton lint fibers that are not fully degreased after wet crushing and soaking degreasing, it is necessary to carry out wet crushing and soaking degreasing again to speed up the degreasing efficiency for the production of fiber cement boards. Preferably, the beating degree of the defatted short cotton lint fibers is greater than 13 and the wet weight is not less than 6.

[0039] Afterwards, the defatted short linter fibers are pumped into a slurry storage tank for later use. Preferably, since the short linter fibers and the wood pulp fibers to be mixed with them are both lightweight materials, they can be premixed prior to pulping. This premixing can be achieved by combining high-pressure air delivery with cyclonic stirring. Under high-pressure air delivery, the wood pulp fibers are fed into the cyclonic stirring short linter fiber slurry, where they are stirred and then sent together to the homogenizer.

[0040] (3) Raw material pulping: defatted short cotton linter fibers, wood pulp fibers, siliceous materials, calcareous materials, polyvinyl alcohol fibers, and auxiliary fillers are homogenized and mixed to obtain a slurry.

[0041] (4) Molding: The slurry moves forward through the continuously running felt of the slurry flow equipment, is dehydrated by the vacuum system, and is wound into a blank on the molding cylinder. When the thickness of the blank reaches the preset thickness, it is torn off.

[0042] When slurry is discharged, for example, the slurry is placed or pumped into a slurry storage tank, and then placed into a headbox for production by gravity or pumping.

[0043] In addition, if the process requires, vibrating screens and refining equipment can be added to reprocess and select the slurry before use.

[0044] Preferably, the solid content of the slurry is 14%-16%.

[0045] (5) Stacking and pressing: Stack the torn blanks into slabs and press them for dehydration;

[0046] When stacking, the blanks torn off from the forming cylinder are trimmed and neatly stacked one plate and one mold at a time on a pad or a trolley. The edge materials and unqualified scrap blanks are recycled.

[0047] The stacked slabs are fed into a press for dehydration according to process requirements to remove a certain amount of water. Preferably, the pressure of the dehydration press is 15-75 MPa and the time is 3-10 minutes.

[0048] (6) Demolding and curing: The pressurized slab undergoes first curing, demoulding, second curing, and drying in sequence to obtain a fiber cement board.

[0049] Preferably, the first curing is static curing or heating pre-curing.

[0050] The slab is sent to a rest curing area or a pre-curing kiln for rest curing or heating pre-curing, wherein the temperature of the heating pre-curing is 41-45°C and the time is 12-14 hours.

[0051] After static or pre-curing, the slabs are separated from the steel formwork, which is then evenly brushed with an environmentally friendly release agent and returned to the stacking area for recycling. The slabs are then stacked onto carts according to process requirements for secondary curing. Preferably, this secondary curing involves autoclaving or moisturizing, such as in an autoclave or a moisturizing area, depending on the product process.

[0052] Preferably, the autoclave curing is performed at 180-185° C. for 8-8.5 hours.

[0053] Then, the steamed boards are dried to remove a certain amount of moisture, and then thickness is measured and classified and stacked. Preferably, the drying temperature is 90-95°C and the drying time is 2-3 hours.

[0054] Finally, according to production requirements, the fiber cement board will be cut at the edges and corners, or the surface will be polished and sanded.

[0055] The present invention utilizes cotton linter solid waste as one of the raw materials for fiber cement board, thereby reducing dependence on wood fiber and reducing production costs. At the same time, during the production process of the fiber cement board, the clean water produced by the fiber reinforced cement board is used to degrease the cotton linter solid waste, thereby avoiding the use of a large amount of strong alkaline chemicals, thereby improving resource utilization and reducing the impact on the environment. The obtained fiber cement board has good flexural strength.

[0056] Example 1

[0057] (1) Wet crushing: Add clean water from fiber reinforced cement board production and cotton lint fibers after dust removal from cotton lint solid waste screening into the crusher for crushing and cutting.

[0058] (2) Soaking and degreasing: The crushed cotton lint fibers are soaked in clean water for fiber reinforced cement board production, stirred regularly during soaking, and the pH value is maintained at 12 until the cotton lint fibers no longer float within 40 minutes to obtain defatted short cotton lint fibers, which are then put into a slurry storage tank for use.

[0059] (3) Raw material pulping: 3% of defatted short cotton linter fiber, 5% of wood pulp fiber, 48% of quartz sand, 41% of cement and 3% of auxiliary filler are homogenized and mixed in a homogenizer for 15 minutes to obtain a slurry.

[0060] (4) Molding: The slurry is pumped to the slurry storage tank, diluted to a concentration of 16%, and then pumped into the slurry box for production. During the continuous operation of the slurry equipment, the felt moves forward (the operating speed is 85m / min), dehydrated by the vacuum system, and wound on the molding cylinder into a blank. When the blank reaches a thickness of 9.5mm, it is torn off.

[0061] (5) Stacking and pressurizing: After the torn blanks are trimmed, they are neatly stacked one plate and one mold on a pad or a trolley. The stacking height does not exceed 1.1m. They are stacked into slabs and pressed for dehydration. The pressure is set to 15MPa and the pressurizing time is 3min.

[0062] (6) Demolding and maintenance:

[0063] (61) The pressurized slab is sent to the pre-curing kiln for heating and pre-curing. The temperature is controlled at 41°C and the pre-curing time is 12 hours.

[0064] (62) The pre-cured slab is separated from the steel formwork, and the formwork is evenly brushed with an environmentally friendly release agent and then returned to the stacking area for recycling; the slab is stacked on a trolley according to the process requirements and sent to the autoclave for autoclave curing; the temperature is 180°C, the holding time is 8.5 hours, and the temperature is increased for 2 hours and cooled for 4 hours to complete the steam curing of the slab.

[0065] (63) The steamed boards are dried at 90°C for 2.5 hours to ensure that the moisture content is less than 8.5%. After drying, the thickness is tested and the boards are classified and stacked.

[0066] (64) Cut the edges and corners, sand the thickness to 8mm, and sand the surface to 120 grit to ensure that the surface is flat and flawless.

[0067] Example 2

[0068] (1) Wet crushing: Add clean water from fiber reinforced cement board production and cotton lint fibers after dust removal from cotton lint solid waste screening into the crusher for crushing and cutting.

[0069] (2) Soaking and degreasing: The crushed cotton lint fibers are soaked in clean water for fiber reinforced cement board production, stirred regularly during soaking, and the pH value is maintained at 12 until the cotton lint fibers no longer float within 40 minutes to obtain defatted short cotton lint fibers, which are then put into a slurry storage tank for use.

[0070] (3) Raw material pulping: 4% of defatted short cotton linter fiber, 4% of wood pulp fiber, 48% of quartz sand, 41% of cement, and 3% of additive filler are homogenized and mixed in a homogenizer for 15 minutes to obtain a slurry.

[0071] (4) Molding: The slurry is pumped to the slurry storage tank, diluted to a concentration of 16%, and then pumped into the slurry box for production. During the continuous operation of the slurry equipment, the felt moves forward (the operating speed is 85m / min), dehydrated by the vacuum system, and wound on the molding cylinder into a blank. When the blank reaches a thickness of 9.5mm, it is torn off.

[0072] (5) Stacking and pressurizing: After the torn blanks are trimmed, they are neatly stacked one plate and one mold on a pad or a trolley. The stacking height does not exceed 1.1m. They are stacked into slabs and pressed for dehydration. The pressure is set to 15MPa and the pressurizing time is 3min.

[0073] (6) Demolding and maintenance:

[0074] (61) The pressurized slab is sent to the pre-curing kiln for heating and pre-curing. The temperature is controlled at 41°C and the pre-curing time is 12 hours.

[0075] (62) The pre-cured slab is separated from the steel formwork, and the formwork is evenly brushed with an environmentally friendly release agent and then returned to the stacking area for recycling; the slab is stacked on a trolley according to the process requirements and sent to the autoclave for autoclave curing; the temperature is 180°C, the holding time is 8.5 hours, and the temperature is increased for 2 hours and cooled for 4 hours to complete the steam curing of the slab.

[0076] (63) The steamed boards are dried at 90°C for 2.5 hours to ensure that the moisture content is less than 8.5%. After drying, the thickness is tested and the boards are classified and stacked.

[0077] (64) Cut the edges and corners, sand the thickness to 8mm, and sand the surface to 120 grit to ensure that the surface is flat and flawless.

[0078] Example 3

[0079] (1) Wet crushing: Add clean water from fiber reinforced cement board production and cotton lint fibers after dust removal from cotton lint solid waste screening into the crusher for crushing and cutting.

[0080] (2) Soaking and degreasing: The crushed cotton lint fibers are soaked in clean water for fiber reinforced cement board production, stirred regularly during soaking, and the pH value is maintained at 12 until the cotton lint fibers no longer float within 40 minutes to obtain defatted short cotton lint fibers, which are then put into a slurry storage tank for use.

[0081] (3) Raw material pulping: 1% defatted short cotton linter fiber, 2% wood pulp fiber, 78% quartz sand, 11% cement, 3% polyvinyl alcohol fiber, and 5% additive filler are homogenized and mixed in a homogenizer for 15 minutes to obtain a slurry.

[0082] (4) Molding: The slurry is pumped to the slurry storage tank, diluted to a concentration of 16%, and then pumped into the slurry box for production. During the continuous operation of the slurry flow equipment, the felt moves forward (the operating speed is 85m / min), dehydrated by the vacuum system, and wound into a blank on the molding cylinder. When the blank reaches a thickness of 9.8mm, it is pulled off.

[0083] (5) Stacking and pressurizing: After the torn blanks are trimmed, they are neatly stacked one plate and one mold on a pad or a trolley. The stacking height does not exceed 1.1m. They are stacked into slabs and pressed for dehydration. The pressure is set to 75MPa and the pressurizing time is 10min.

[0084] (6) Demolding and maintenance:

[0085] (61) The pressurized slab is sent to the pre-curing kiln for heating and pre-curing. The temperature is controlled at 41°C and the pre-curing time is 12 hours.

[0086] (62) The pre-cured slab is separated from the steel formwork, and the formwork is evenly brushed with an environmentally friendly release agent and then returned to the stacking area for recycling; the slab is stacked on a trolley according to the process requirements and sent to the moisturizing curing area for moisturizing curing for 28 days.

[0087] (63) After curing, the edges and corners of the board are cut, the thickness is sanded to 8mm, and the surface is sanded to 120 mesh to ensure that the surface is flat and flawless.

[0088] Example 4

[0089] (1) Wet crushing: Add clean water from fiber reinforced cement board production and cotton lint fibers after dust removal from cotton lint solid waste screening into the crusher for crushing and cutting.

[0090] (2) Soaking and degreasing: The crushed cotton lint fibers are soaked in clean water for fiber reinforced cement board production, stirred regularly during soaking, and the pH value is maintained at 12 until the cotton lint fibers no longer float within 40 minutes to obtain defatted short cotton lint fibers, which are then put into a slurry storage tank for use.

[0091] (3) Raw material pulping: 2% defatted short cotton linter fiber, 1% wood pulp fiber, 78% quartz sand, 11% cement, 3% polyvinyl alcohol fiber, and 5% additive filler are homogenized and mixed in a homogenizer for 15 minutes to obtain a slurry.

[0092] (4) Molding: The slurry is pumped to the slurry storage tank, diluted to a concentration of 16%, and then pumped into the slurry box for production. During the continuous operation of the slurry flow equipment, the felt moves forward (the operating speed is 85m / min), dehydrated by the vacuum system, and wound into a blank on the molding cylinder. When the blank reaches a thickness of 9.8mm, it is pulled off.

[0093] (5) Stacking and pressurizing: After the torn blanks are trimmed, they are neatly stacked one plate and one mold on a pad or a trolley. The stacking height does not exceed 1.1m. They are stacked into slabs and pressed for dehydration. The pressure is set to 75MPa and the pressurizing time is 10min.

[0094] (6) Demolding and maintenance:

[0095] (61) The pressurized slab is sent to the pre-curing kiln for heating and pre-curing. The temperature is controlled at 41°C and the pre-curing time is 12 hours.

[0096] (62) The pre-cured slab is separated from the steel formwork, and the formwork is evenly brushed with an environmentally friendly release agent and then returned to the stacking area for recycling; the slab is stacked on a trolley according to the process requirements and sent to the moisturizing curing area for moisturizing curing for 28 days.

[0097] (63) After curing, the edges and corners of the board are cut, the thickness is sanded to 8mm, and the surface is sanded to 120 mesh to ensure that the surface is flat and flawless.

[0098] In the above embodiments, the defatted short cotton linter fibers all achieved a beating degree of 15 and a wet weight of 8.

[0099] Experimental results

[0100] The fiber cement boards prepared in Examples 1-4 were tested for density and flexural strength according to the test method in GBT7019-2014. The test results are shown in Table 1.

[0101] Table 1 Test results

[0102]

[0103] As can be seen from Table 1, the fiber cement boards prepared by the present application in Examples 1-4 maintain a flexural strength comparable to that of traditional products, meeting the high standards of the construction industry.

Claims

1. A method for preparing a fiber cement board doped with defatted short cotton linter fibers, characterized in that: The fiber cement board raw materials include siliceous material, calcareous material, polyvinyl alcohol fiber, auxiliary filler, defatted short cotton linter fiber and wood pulp fiber, wherein, based on the total weight of the fiber cement board, the defatted short cotton linter fiber comprises 1%-4%, wood pulp fiber 1%-5%, siliceous material 48%-78%, calcareous material 11%-41%, polyvinyl alcohol fiber 0-3%, and auxiliary filler 1%-3%; the defatted short cotton linter fiber is prepared by soaking cotton linter solid waste in clean water during the production of fiber reinforced cement board; The fiber cement board is prepared by the following steps: (1) Wet crushing: Add clean water from fiber reinforced cement board production and cotton lint fibers after dust removal from cotton lint solid waste screening into the crushing equipment for crushing and cutting; (2) Soaking and degreasing: The crushed cotton lint fibers are soaked in clean water to obtain defatted short cotton lint fibers; The pH value of the fiber-reinforced cement board production water used for soaking is not less than 11. The pH is maintained by filtering the current fiber-reinforced cement board production water and then adding it back, and / or automatically replenishing new fiber-reinforced cement board production water based on pH monitoring. The total soaking time is determined based on the mass of the crushed cotton lint fibers, until the cotton lint fibers no longer float within 40 minutes. During soaking, regular stirring is used to accelerate the crushing process, and the fiber-reinforced cement board production water is heated to shorten the degreasing time. (3) Raw material pulping: defatted short cotton linter fibers, wood pulp fibers, siliceous materials, calcium materials, polyvinyl alcohol fibers, and additive fillers are homogenized and mixed to obtain a slurry; (4) Molding: The slurry moves forward through the continuously running felt of the slurry flow equipment, is dehydrated by the vacuum system, and is wound into a blank on the forming cylinder. When the blank reaches the preset thickness, it is torn off; (5) Stacking and pressing: Stack the torn blanks into slabs and press them for dehydration; (6) Demolding and curing: The pressurized slab undergoes first curing, demolding, second curing, and drying in sequence to obtain a fiber cement board.

2. The method for preparing fiber cement board doped with defatted short cotton linter fibers according to claim 1, characterized in that: In the step (2), the beating degree of the defatted short cotton linter fiber is greater than 13 and the wet weight is not less than 6.

3. The method for preparing fiber cement board doped with defatted short cotton linter fibers according to claim 1, characterized in that: In the step (4), the solid content of the slurry is 14%-16%.

4. The method for preparing fiber cement board doped with defatted short cotton linter fibers according to claim 1, characterized in that: In the step (5), the pressure of the pressing dehydration is 15-75 MPa and the time is 3-10 min.

5. The method for preparing fiber cement board doped with defatted short cotton linter fibers according to claim 1, characterized in that: In the step (6), the first curing is static curing or heating pre-curing, and the second curing is autoclaving curing or moisturizing curing.

6. The method for preparing fiber cement board doped with defatted short cotton linter fibers according to claim 5, characterized in that: The temperature of the heating pre-curing is 41-45° C. and the time is 12-14 hours; the temperature of the autoclaving curing is 180-185° C. and the time is 8-8.5 hours.

7. The method for preparing fiber cement board doped with defatted short cotton linter fibers according to claim 1, characterized in that: In the step (6), the drying temperature is 90-95°C and the drying time is 2-3 hours.

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