A method for applying adhesive to cotton sheets used in the preparation of cotton fiber-based simulated fiberboard.

Abstract

This application relates to the field of waste textile resource utilization technology, specifically to a method for applying adhesive to cotton sheets used in the preparation of cotton fiber-based simulated fiberboard. First, a modified starch adhesive is applied to the surface of the cotton sheet. After the modified starch adhesive dries and cures, it forms a sealing layer. Then, an adhesive is applied to the surface of the cotton sheet. The sealing layer formed after the modified starch adhesive cures reduces the amount of main adhesive required, thereby lowering production costs.

Description

Technical Field

[0001] This invention relates to the field of waste textile resource utilization technology, specifically to a sizing method for cotton sheets used in preparing cotton fiber-based simulated fiberboard. Background Technology

[0002] Globally, 90 million tons of textile waste are generated annually. In my country, the recycling rate of waste clothing is less than 20%. The National Development and Reform Commission's "Implementation Opinions on Accelerating the Recycling of Waste Textiles" clearly requires that the recycling rate of waste textiles reach 25% by 2025 and 30% by 2030. At the same time, my country's dependence on imported timber exceeds 50%, and the supply of raw materials for traditional wood-based panels is tight. Therefore, utilizing waste clothing to obtain cotton fibers and further processing them into fiberboard is a technological route that can improve the recycling rate of waste textiles, alleviate timber resource shortages, and increase the added value of waste textiles.

[0003] Some existing technical solutions involve extracting cotton fibers from waste clothing, mixing the cotton fibers with adhesives, and finally preparing fiberboard by pressing.

[0004] The technical solution disclosed in Chinese invention patent CN107234703B, entitled "High-performance fiberboard based on the recycling of waste cotton textiles and its preparation method," involves: first, cutting waste cotton fabric into scraps, soaking them in water, mixing the scraps with water, sodium hydroxide, and hydrogen peroxide, and then continuously cooking the mixture; washing with water, grinding the mixture using a disc mill, drying it, and then pulverizing it a second time to obtain cotton fibers; uniformly mixing polyisocyanate and cotton fibers to obtain sizing cotton fibers; laying the sizing cotton fibers and pre-pressing them to obtain a pre-pressed board; then heating it to 100-200℃, hot-pressing it, and cooling it to obtain a high-performance fiberboard. This fiberboard possesses excellent physical and mechanical properties, low water absorption, and environmentally friendly characteristics, and achieves the secondary high-value utilization of waste cotton textiles. The preparation process requires no special equipment and can be achieved using existing processing equipment, making it simple, easy to implement, and suitable for industrial production.

[0005] To improve the waterproof performance of cotton fiber-based simulated fiberboard, the adhesives used are generally the polyisocyanate adhesives mentioned above, or polyisocyanate adhesives. Both are expensive, and compared to wood fiber, straw fiber, etc., cotton fiber absorbs a large amount of adhesive, resulting in a significant increase in the amount of adhesive applied. Therefore, the production cost of high-performance fiberboard in the existing technology is generally high, which is not conducive to industrialization. Summary of the Invention

[0006] This application provides a method for pressing cotton sheets to prepare cotton fiber-based simulated fiberboard, aiming to solve the problem of excessive glue application in existing technologies, thereby reducing the glue application amount and thus lowering production costs. The specific technical solution adopted in this application is as follows:

[0007] A method for applying adhesive to cotton sheets used in the preparation of cotton fiber-based simulated fiberboard involves first applying modified starch adhesive to the surface of the cotton sheet, which then dries and cures to form a sealing layer, and finally applying an adhesive to the surface of the cotton sheet.

[0008] Preferably, the modified starch adhesive is applied by spray coating.

[0009] Preferably, the amount of modified starch adhesive applied is 150~200 g / cm³. 3 .

[0010] Preferably, the cotton pad with the modified starch adhesive is dried and cured after passing through a hot tunnel at a temperature of 80~85°C to form the sealing layer, with a passage time of 2.0~2.5 min.

[0011] Preferably, the modified starch adhesive comprises 100 parts of oxidized starch, 3-4 parts of epichlorohydrin crosslinking agent, 4-5 parts of nano-montmorillonite, 15-16 parts of butyl acrylate grafted monomer, and 12-13 parts of polymethylene polyphenyl polyisocyanate.

[0012] Preferably, the modified starch adhesive has a solid content of 45-50%.

[0013] Preferably, the modified starch adhesive is prepared by the following steps:

[0014] Step 1: Add deionized water at a temperature of 25-30°C while stirring;

[0015] Step 2: Heat to 80~85℃, stir continuously and keep warm for 10~15 minutes;

[0016] Step 3: Add sodium bicarbonate, bringing the pH to 8.5-9.0;

[0017] Step 4: Continue stirring and add epichlorohydrin crosslinking agent;

[0018] Step 5: Continue stirring and cool to 60±2℃. Slowly pour in the ultrasonically treated nano-montmorillonite slurry within 5 minutes, for a duration of 18~20 minutes.

[0019] Step 6: Continue stirring and cool to 45±1℃, then add butyl acrylate grafted monomer for 110~120 min.

[0020] Step 7: Cool down to below 40℃ and discharge the material;

[0021] Add polymethylene polyphenyl polyisocyanate 10 minutes before use.

[0022] Preferably, in step one, the oxidized starch is added within 5 minutes.

[0023] Preferably, in step three, sodium bicarbonate is added within 2 minutes, and the amount added is 0.3% of the amount of oxidized starch added.

[0024] Preferably, the application rate of the adhesive is 300~400 g / cm³. 2 .

[0025] The sealing layer formed by the curing of modified starch adhesive can reduce the amount of main adhesive required, thereby reducing production costs. Attached Figure Description

[0026] The accompanying drawings, which form part of this application, are used to provide further explanation of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application.

[0027] Figure 1 This is a product photo of the cotton fiber-based simulated fiberboard provided in Embodiment 3 of this application. Detailed Implementation

[0028] The technical solutions in this application are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its application or use. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] Example 1: This example provides a method for applying adhesive to cotton sheets used to prepare cotton fiber-based simulated fiberboard. It is applicable to applying adhesive to one or two surfaces of cotton sheets prepared by existing technology, and then performing hot pressing after stacking multiple identical or different cotton sheets to obtain cotton fiber-based simulated fiberboard.

[0030] The cotton sheets in this embodiment are obtained using existing technology. Specifically, waste cotton fabric is selected and cut into 50cm x 50cm pieces. The fabric pieces, water, sodium hydroxide (NaOH, commonly known as caustic soda / lye / sodium hydroxide), and hydrogen peroxide (H2O2, commonly known as hydrogen peroxide) are mixed evenly and then boiled for 10 hours. Afterward, the fabric pieces are removed, washed with water, and pulped using a disc mill method. After drying, they are pulverized a second time to obtain cotton fibers. Then, the fibers are shaped and the moisture is released in a dust cage. After shaping, the continuous cotton fiber accumulation thickness is 25mm. Finally, the fibers leave the dust cage and enter a steel-cotton roller pressing line or other existing belt pre-pressing line. The linear pressure is 4.5kN / m, and the thickness is compressed to 4mm, resulting in a density of approximately 400g / cm³. 3 1. Cotton sheets with a moisture content of 10±2%. To facilitate the sizing process, cut the continuous cotton sheets to a suitable length, such as 4.8m.

[0031] In this embodiment, a modified starch adhesive is applied to one surface of the cotton pad. After the modified starch adhesive dries and cures, it forms a sealing layer. Then, an adhesive is applied to the surface of the cotton pad.

[0032] Specifically, the modified starch adhesive comprises 100 parts of oxidized starch, 3-4 parts of epichlorohydrin crosslinking agent, 4-5 parts of nano-montmorillonite, 15-16 parts of butyl acrylate grafted monomer, and 12-13 parts of polymethylene polyphenyl polyisocyanate (PAPI, also known as polymeric MDI). The modified starch adhesive is prepared by the following method (taking the modification of 1000g of oxidized starch as an example):

[0033] Step 1: Add 90g of deionized water to the reactor, which is about 10% of the final solid content. The temperature of the deionized water in the reactor is 25℃, and the speed of the stirrer in the reactor is 200rpm. Slowly add 1000g of oxidized starch (0.18% carboxyl group) over 5 minutes to avoid clumping and to form a low-viscosity suspension.

[0034] Step 2: Continue stirring and heat to 80±2℃, keep warm for 15 minutes to allow the starch to gelatinize completely and increase viscosity.

[0035] Step 3: Continue stirring and add 3g of sodium hydroxide (NaHCO3, buffer) within 2 minutes. The amount added is 0.3% of the amount of oxidized starch added, so as to maintain the pH value at 8.5~9.0.

[0036] Step 4: Continue stirring and add 40g of epichlorohydrin crosslinking agent, continue stirring for 15 minutes to complete the crosslinking.

[0037] Step 5: Continue stirring and cool to 60±2℃. Slowly pour in 45g of ultrasonically treated nano-montmorillonite (MMT) slurry within 5 minutes, followed by intercalation for 20 minutes.

[0038] Step 6: Continue stirring and cool to 45±1℃, add 155g of butyl acrylate grafting monomer, and then graft for 120min.

[0039] Step 7: Cool down to below 40℃ and discharge the material.

[0040] Add 125g of PAPI isocyanate 10 minutes before use to obtain a modified starch adhesive with a solid content of 45-50%, a viscosity of 5000±500 mPa·s (25°C), and a thixotropic index of 3.2-3.3. Apply the adhesive to cotton pads using a conventional coating machine, using a spray coating method at a density of 150g / cm³. 3 The amount of adhesive applied forms a modified starch adhesive layer on the surface of the cotton sheet.

[0041] The drying and curing step involves passing the cotton sheet through a thermal tunnel at a temperature of 80±2℃, preferably an infrared thermal tunnel, for 2.5 minutes. After curing, a sealing layer of approximately 0.1 mm is formed on the surface of the cotton sheet. This sealing layer is an adhesive layer that acts as a sealant, preventing excessive penetration of adhesives (such as polyisocyanate adhesives or epoxy resin adhesives), thereby reducing the amount of adhesive applied and manufacturing costs.

[0042] The cotton pads are then passed through a coating machine in the next process, which applies a polyisocyanate adhesive in a spray coating manner at a density of 300 g / cm³. 3 The amount of adhesive applied forms an adhesive layer on the surface of the cotton sheet. Then, three adhesive-coated cotton sheets are stacked together to obtain a laminated cotton sheet.

[0043] Finally, the three sets of laminated cotton sheets were hot-pressed with hot-pressing parameters of 85℃ / 2.5MPa / 4h, 95℃ / 3.5MPa / 4h and 105℃ / 2.5MPa / 4h respectively, with a thickness of 7mm. The obtained cotton fiber-based simulated fiberboards were marked as specimen 1-1, specimen 1-2 and specimen 1-3 respectively.

[0044] Example 2: The difference between this example and Example 1 is that the application rate of the modified starch adhesive is 200 g / cm³. 3 The application rate of the polyisocyanate adhesive is 400 g / cm³. 3 The obtained cotton fiber-based simulated fiberboards were labeled as specimen 2-1, specimen 2-2, and specimen 2-3, respectively.

[0045] Example 3: The difference between this example and Example 1 lies in the method of obtaining the cotton sheets. Specifically, the cotton sheets in this example include three processes: S1. sorting process, S2. cotton fiber acquisition process, and S3. cotton sheet preparation process, which involves pressing cotton fibers into cotton sheets.

[0046] S1. Sorting process

[0047] The main purpose of this process is to classify waste clothing into the following categories: C1. Knitted clothing, such as T-shirts and cardigans; C2. Thick woven fabrics, such as jeans and canvas bags; C3. Fluffy wadding, such as cotton clothing and quilts. Classification can be done manually or using any existing automated sorting device with a vision sorting system. An additional step is to separate the wrapper from the core of C3. Fluffy wadding. The core enters the next process as C3. Fluffy wadding, while the wrapper is sorted and classified as either C1. Knitted clothing or C2. Thick woven fabric. Of course, this process also requires manual or automated removal of obvious buttons, accessories, or decorations.

[0048] S2. Cotton fiber acquisition process

[0049] The main purpose of this process is to loosen different types of waste clothing according to their material and thickness.

[0050] For knitted garments, the fabric is first cut to obtain pieces approximately 50×50mm in size, then subjected to low-temperature freezing and embrittlement treatment, and finally shredded and opened to obtain the first cotton fibers. Specifically, the knitted garment is treated at a temperature of -20~-15℃ for 10~12 minutes. Then, a hook-tooth shredder is used to coarsely open the fibers at a speed of 400rpm. Next, atomized water at 60℃ is sprayed about 0.3m above the coarsely opened cotton fibers at an 80° angle. The coarsely opened cotton fibers pass through the spray area for 1.0~1.5s, and the moisture content of the coarsely opened fibers after passing through is approximately 10~11%. Adding 0.1~0.2% antistatic agent to the atomized water reduces the surface resistance of the coarsely opened cotton fibers to <10 Ω·cm. 9 Ω. Finally, a high-speed needle roller opener is used to fine open the coarsely opened cotton fibers at a linear speed of 25~30m / s to obtain first cotton fibers with a fiber length in the range of 15~25mm, with a fiber yield of approximately 82%. A cotton box outlet equipped with a belt weighing is installed after the high-speed needle roller opener for quantitative measurement.

[0051] For thick woven fabrics, metal is first removed using a strong magnetic field, followed by shredding, and finally wet opening to obtain the second cotton fiber. Specifically, a high-strength magnetic conveyor line using existing technology is used to remove any missed metal buttons, accessories, or small decorative items. Then, a twin-shaft shredder with preferably H13 blades (2mm blade spacing) is used for coarse opening. Next, atomized water at 60°C is sprayed approximately 0.3m above the coarsely opened cotton fiber at an 80° angle, with the fiber passing through the spray area for 3-4 seconds. The moisture content of the coarsely opened fiber is approximately 18-20%. 0.1-0.2% antistatic agent is added to the atomized water. Finally, a high-speed needle roller opener is used at a linear velocity of 25-30m / s to finely open the coarsely opened cotton fiber, obtaining the second cotton fiber with a fiber length in the range of 10-20mm, with a fiber yield of approximately 78%. A cotton box outlet equipped with a belt weighing system is installed after the high-speed needle roller opener to facilitate quantitative measurement.

[0052] For the fluffy wadding, it is first compressed and compacted, then disassembled and opened to obtain the third cotton fiber. Specifically, atomized water at 60°C with 0.1-0.2% antistatic agent is sprayed about 0.3m above the fluffy wadding at an 80° angle. The wadding passes through the spray area for 2.0-2.5 seconds, and the moisture content of the fabric strip after passing through is about 10%. 0.1-0.2% antistatic agent is added to the atomized water. Subsequently, the fluffy wadding is fed into a hydraulic tank and held at a pressure of 1.0-1.1MPa for 10-15 seconds, aiming to achieve a compression ratio of (5-6):1. Finally, a toothed roller disassembly machine is used for coarse opening, followed by a high-speed needle roller opener at a linear speed of 25-30m / s to finely open the coarsely opened cotton fibers, obtaining the third cotton fiber with a fiber length in the range of 20-30mm, with a fiber yield of about 85%. A cotton box outlet equipped with a belt weighing system is installed after the high-speed needle roller opener to facilitate quantitative measurement.

[0053] S3. Cotton Sheet Preparation Process

[0054] The first cotton fiber is conveyed, dispersed, and diffused using an air duct with an air pressure of 0.35~0.45MPa and an air velocity of 20~30m / s. Subsequently, it is shaped and moisture is released within a dust cage, resulting in a continuous fiber buildup thickness of 20~30mm. Afterward, it leaves the dust cage and enters a steel-cotton roller pressing line or other existing belt pre-pressing line, with a linear pressure of 5kN / m, compressing the thickness to 2~4mm, achieving a density of 400~450g / cm³. 3 The first cotton sheet has a moisture content of 10±2%. Finally, the continuous first cotton sheet is rolled up for storage or transfer, or it can go directly to the S4 pressing process without being rolled up, but the first cotton sheet should be cut to a suitable length before pressing.

[0055] The first and second cotton fibers are conveyed, dispersed, and mixed using an air duct. The air pressure within the duct is 0.35–0.45 MPa, and the air velocity is 20–30 m / s. The mixed cotton fibers are then diffused using the velocity difference. Next, the fibers are shaped and moisture is released within a dust cage, resulting in a continuous fiber buildup thickness of 20–30 mm. Afterward, the fibers leave the dust cage and enter a steel-cotton roller pressing line or other existing belt pre-pressing line, where the linear pressure is 4.5 kN / m, compressing the thickness to 3–5 mm and achieving a density of 300–350 g / cm³. 3 The second cotton sheet has a moisture content of 10±2%. Finally, the continuous second cotton sheet is rolled up for storage or transfer, or it can be directly sent to the S4 pressing process without being rolled up. However, the second cotton sheet should be cut to a suitable length before pressing.

[0056] The third cotton fiber is conveyed, dispersed, and diffused using an air duct with an air pressure of 0.35~0.45MPa and an air velocity of 20~30m / s. Subsequently, it is shaped and moisture is released within a dust cage, resulting in a continuous fiber buildup thickness of 20~30mm. Afterward, it leaves the dust cage and enters a steel-cotton roller pressing line or other existing belt pre-pressing line, with a linear pressure of 5kN / m, compressing the thickness to 2~3mm, achieving a density of 400~450g / cm³. 3 The third cotton sheet has a moisture content of 10±2%. Finally, the continuous third cotton sheet is rolled up for storage or transfer, or it can be directly sent to the S4 pressing process without being rolled up. However, the third cotton sheet should be cut to a suitable length before pressing.

[0057] The first to third cotton pads are passed through an existing adhesive coating machine, thereby applying the adhesive by spray coating at a rate of 150 g / cm³. 3 The amount of adhesive applied forms a modified starch adhesive layer on the surface of the cotton sheet.

[0058] The drying and curing step involves passing the cotton sheet through a thermal tunnel at a temperature of 80±2℃, preferably an infrared thermal tunnel, for 2.5 minutes. After curing, a sealing layer of approximately 0.1 mm is formed on the surface of the cotton sheet.

[0059] The first to third cotton sheets are then passed through a coating machine in the next process. This machine is used to apply polyisocyanate adhesive, using a spray coating method at 300 g / cm³. 3 The amount of adhesive applied forms an adhesive layer on the surface of the cotton sheet. Subsequently, the first to third cotton sheets after adhesive application are stacked in a top-to-bottom order to obtain a stacked cotton sheet.

[0060] Finally, the layered cotton sheets were hot-pressed at 105℃ / 2.5MPa / 4h with a thickness of 7mm. The resulting cotton fiber-based simulated fiberboards were labeled as specimens 3 (reference). Figure 1 (As shown).

[0061] The cotton fiber-based simulated fiberboards prepared in Examples 1 to 3 have relatively high waterproof performance, flame retardant performance, dimensional stability and mechanical strength. For specific product performance, please refer to Table 1.

[0062] Comparative Example 1: The difference between this comparative example and Example 1 is that the polyisocyanate adhesive was directly coated onto the surface of the cotton pad using a spray coating method. To achieve the requirement of no adhesive penetration or leakage on the surface, the actual adhesive application rate was 835 g / cm³. 2 The hot-pressing parameters were 85℃ / 2.5MPa / 4h, and the thickness was 7mm. The resulting cotton fiber-based simulated fiberboard was marked as Control 1.

[0063] Comparative Example 2: The difference between this comparative example and Example 1 is that the obtained cotton fibers were directly mixed with the polyisocyanate adhesive to obtain sizing cotton fibers. When the requirement of no missing adhesive was met, the actual sizing amount was 842 g / cm³. 2 After the sizing of the cotton fibers was laid out, it was pre-pressed to obtain a pre-pressed board. Then, the temperature was raised to 105℃, the pressure was 2.5MPa, the holding time was 4h, the thickness was 7mm, and it was cooled after hot pressing. The resulting cotton fiber-based simulated fiberboard was marked as Control 2.

[0064] Table 1

[0065]

[0066] As can be seen from Table 1, the cotton fiber-based fiberboard provided in this application embodiment has product performance similar to that of the prior art, but the amount of adhesive, especially the main adhesive, is significantly reduced, and the production cost of cotton fiber-based fiberboard of the same thickness can be reduced by 8 to 10 yuan / ㎡.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sizing method for preparing a cotton sheet of a cotton fiber-based simulated fiberboard, characterized by, First, a modified starch adhesive is applied to the surface of the cotton pad. After the modified starch adhesive dries and cures, it forms a sealing layer. Then, an adhesive is applied to the surface of the cotton pad.

2. The sizing method for preparing a cotton sheet of a cotton fiber-based simulated fiberboard according to claim 1, characterized in that, The modified starch adhesive is applied by spray coating.

3. The sizing method for preparing cotton sheets for cotton fiber-based simulated fiberboard according to claim 2, characterized in that, The modified starch glue is applied in an amount of 150 to 200 g / cm 3 .

4. The sizing method for preparing cotton sheets for cotton fiber-based simulated fiberboard according to claim 1, characterized in that, The cotton pad with the modified starch adhesive applied is dried and cured after passing through a hot tunnel at a temperature of 80~85℃ to form the sealing layer, with a passage time of 2.0~2.5min.

5. The sizing method for preparing cotton sheets for cotton fiber-based simulated fiberboard according to claim 1, characterized in that, The modified starch adhesive comprises 100 parts of oxidized starch, 3-4 parts of epichlorohydrin crosslinking agent, 4-5 parts of nano-montmorillonite, 15-16 parts of butyl acrylate graft monomer, and 12-13 parts of polymethylene polyphenyl polyisocyanate.

6. The sizing method for preparing cotton sheets for cotton fiber-based simulated fiberboard according to claim 5, characterized in that, The modified starch adhesive has a solid content of 45-50%.

7. The sizing method for preparing cotton sheets for cotton fiber-based simulated fiberboard according to claim 1, characterized in that, The modified starch adhesive is prepared by the following steps: Step 1: Add deionized water at a temperature of 25-30°C while stirring; Step 2: Heat to 80~85℃, stir continuously and keep warm for 10~15 minutes; Step 3: Add sodium bicarbonate, bringing the pH to 8.5-9.0; Step 4: Continue stirring and add epichlorohydrin crosslinking agent; Step 5: Continue stirring and cool to 60±2℃. Slowly pour in the ultrasonically treated nano-montmorillonite slurry within 5 minutes, for a duration of 18~20 minutes. Step 6: Continue stirring and cool to 45±1℃, then add butyl acrylate grafted monomer for 110~120 min. Step 7: Cool down to below 40℃ and discharge the material; Add polymethylene polyphenyl polyisocyanate 10 minutes before use.

8. The sizing method for preparing cotton sheets for cotton fiber-based simulated fiberboard according to claim 7, characterized in that, In step one, the oxidized starch is added within 5 minutes.

9. The sizing method for preparing cotton sheets for cotton fiber-based simulated fiberboard according to claim 7, characterized in that, In step three, sodium bicarbonate is added within 2 minutes, and the amount added is 0.3% of the amount of oxidized starch added.

10. The sizing method for preparing cotton sheets for cotton fiber-based simulated fiberboard according to claim 1, characterized in that, The adhesive is applied at a rate of 300 to 400 g / cm 2 .

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