Cotton / polyester composite aerogel preparation method and application thereof
By preparing aerogels by combining kapok and polyester fibers, the problems of complex preparation and insufficient performance of cellulose aerogels were solved, achieving low-cost and efficient oil adsorption and separation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN POLYTECHNIC UNIVERSITY
- Filing Date
- 2024-03-06
- Publication Date
- 2026-07-28
AI Technical Summary
Existing cellulose aerogels have problems such as complex preparation, high cost, poor mechanical properties and difficulty in reusing in the field of oil adsorption. Kapok fiber adsorption materials have uneven structure and low oil absorption capacity.
A composite aerogel of kapok/polyester was prepared by combining natural hollow kapok fiber with double-melting-point core-sheath structure polyester fiber through mechanical grinding, silanization modification and freeze-drying. The mechanical and adsorption properties of the material were improved by combining physical entanglement and thermal bonding technology.
The prepared kapok/polyester composite aerogel has good adsorption and mechanical properties, low density, wide adsorption range, can be reused multiple times, and the preparation process is simple and low cost, making it suitable for oil adsorption and oil-water separation.
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Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing kapok / polyester composite aerogel and its application, belonging to the field of aerogel material technology. Background Technology
[0002] In recent years, water pollution caused by oil spills and oily wastewater from industrial production has easily caused catastrophic damage to related water bodies and their surrounding ecosystems, resulting in incalculable economic losses. Currently, various methods have been developed to remove oil from water, such as membrane separation, adsorption, biological methods, and chemical methods. Among these, the most economical, efficient, and environmentally friendly method is adsorption, which utilizes adsorbents for oil pollution treatment. Cellulose aerogels possess advantages such as high porosity, low density, and good adsorption performance, as well as good biocompatibility and biodegradability, making them widely popular in the field of oil adsorption. However, cellulose extraction methods remain relatively complex and energy-intensive, easily causing environmental pollution. Furthermore, due to the inherent defects of cellulose, cellulose aerogels typically exhibit poor mechanical properties and reusability, making them difficult to apply in practical oil pollution cleanup. Therefore, developing adsorbent materials with abundant and inexpensive raw material sources, simple preparation processes, excellent oil absorption and mechanical properties, and good reusability has become a research hotspot.
[0003] Kapok fiber has a unique hollow structure, natural hydrophobic and oleophilic properties, and good oil absorption performance. It is also abundant, inexpensive, and biodegradable, and is widely used in the development of oil adsorption materials. However, the kapok adsorption materials developed so far do not have a uniform and stable structure, have poor mechanical properties, and have low oil absorption capacity (about 20-40g / g), which still need to be improved. Summary of the Invention
[0004] The technical problem solved by this invention is: how to obtain a low-cost, simple-to-prepare, reusable fiber-based aerogel adsorbent material with good adsorption and mechanical properties. This invention uses natural hollow kapok fiber and double-melting-point core-sheath structure polyester fiber to prepare aerogels, thereby reducing preparation costs and simplifying the preparation process while obtaining an adsorbent material with high adsorption performance and excellent mechanical properties.
[0005] To address the aforementioned technical problems, this invention provides a method for preparing kapok / polyester composite aerogel. The method involves mechanically grinding cut kapok short fibers to obtain kapok fibers with numerous micro- and nano-scale filaments on their surface. The kapok fibers are then mixed with polyester short fibers possessing a core-sheath structure. Through physical entanglement, the kapok / polyester composite aerogel is prepared using silanization modification and freeze-drying. Finally, the composite aerogel is heated in an oven to obtain a composite aerogel with excellent mechanical properties.
[0006] Specifically, the present invention provides a method for preparing the above-mentioned kapok / polyester composite aerogel, comprising the following steps:
[0007] Step 1: Use NaOH solution to treat the surface of short kapok fibers to remove the wax on the surface of the kapok fibers, and then wash with deionized water until neutral to obtain microfibrillated kapok fibers; add deionized water to the microfibrillated kapok fibers, and then put them into a pulping machine for mechanical grinding to obtain a kapok fiber suspension with a large number of filaments on the surface.
[0008] Step 2: Place the polyester staple fiber with a core-sheath structure into the kapok fiber suspension obtained in Step 1 to prepare a uniformly mixed fiber composite suspension;
[0009] Step 3: Hydrophobic modification of the kapok / polyester staple fiber suspension: Adjust the pH of the fiber composite suspension obtained in step 2 to acidic, then add a silane coupling agent to it, and stir the reaction at room temperature to obtain a modified mixed fiber suspension.
[0010] Step 4: Preparation of Kapok / Polyester Composite Aerogel: The modified mixed fiber suspension obtained in Step 3 is placed in a mold and first frozen at low temperature, and then vacuum freeze-dried using a freeze dryer to obtain Kapok / Polyester composite aerogel; then the aerogel is placed in an oven and heated, and the temperature needs to be controlled so that the outer layer of the polyester fiber melts (the core layer does not change) and bonds with the Kapok fiber to achieve the structural strengthening and toughening effect.
[0011] Preferably, the surface treatment in step 1 specifically involves: placing short kapok fibers in a NaOH solution and stirring at 60–130°C for 1–2 hours to remove the waxy coating from the surface of the kapok fibers; the concentration of the NaOH solution is 1.0–20.0 wt%.
[0012] Preferably, the content (mass fraction) of microfibrillated kapok fibers in the kapok fiber suspension prepared in step 1 is 0.1-5.0 wt%, the diameter of the short kapok fibers is about 15-45 μm (hollowness is about 80-90%), and the length distribution is about 100-2000 μm.
[0013] Preferably, in step 2, the polyester with a core-sheath structure consists of a core layer and a sheath layer that surrounds it, and the sheath layer and the core layer have different melting points, with the sheath layer having a higher melting point than the core layer. The melting point of the sheath layer is 230-260℃, and the melting point of the core layer is 80-100℃. The length distribution of the polyester staple fiber ranges from 200 to 3000 μm, and the diameter is approximately 15-25 μm. The mass fraction of the polyester staple fiber in the fiber composite suspension is 0.1-5.0 wt%, preferably 0.1-2.0 wt%.
[0014] Preferably, the silane coupling agent in step 3 is vinyltrimethoxysilane, methyltrimethoxysilane, etc.; the pH adjustment is performed by adjusting the pH value to 3-5, preferably 4-5, using an acid such as hydrochloric acid or acetic acid; the mass fraction of the silane coupling agent in the fiber composite suspension is 0.1-8 wt%; the stirring reaction conditions are: stirring speed 600-800 rpm, time 3-5 h.
[0015] Preferably, the specific conditions for low-temperature freeze-drying in step 4 are: freezing at -20 to -25°C for 10-24 hours or freezing in liquid nitrogen at -196°C for 2-10 minutes; the conditions for vacuum freeze-drying are: temperature -60 to -70°C, time 24-48 hours. The heating conditions are: heating in an oven at 110-160°C for 10-30 minutes.
[0016] The present invention also provides a kapok / polyester composite aerogel prepared by the above preparation method; the density of the aerogel is 3.3-20.0 mg / cm³. 3 The adsorption rate is 56–190 g / g, and the contact angle is 150–165°.
[0017] This invention also provides the application of the above-mentioned kapok / polyester composite aerogel in oil or organic solvent adsorption and oil-water separation.
[0018] Preferably, the application includes selective adsorption of one or more of mineral oil, vegetable oil, vacuum pump oil, engine oil, soybean oil, and organic solvents.
[0019] More preferably, the organic solvent includes any one or more of dimethyl sulfoxide, toluene, N,N-dimethylformamide, chloroform, ethanol, isopropanol, and acetone.
[0020] Preferably, the applications include the reuse of aerogels and oil recovery.
[0021] Compared with the prior art, the present invention has the following beneficial effects:
[0022] 1. This invention prepares kapok fibers with a large number of micro- and nano-scale filaments on the fiber surface by microfibrillation treatment of abundant and inexpensive kapok fibers. The kapok fibers are then mixed with inexpensive and readily available polyester fibers with different melting points in the sheath and core layers to prepare composite aerogels. This can significantly improve the mechanical properties and reusability of the aerogels, while greatly reducing the preparation cost and simplifying the preparation process. It has the advantages of being environmentally friendly, non-toxic, inexpensive, and easy to process.
[0023] 2. The kapok / polyester composite aerogel prepared by this invention possesses excellent mechanical properties; it can be bent, folded, and repeatedly compressed without breaking its shape or collapsing its structure. The density of the aerogel is 3.3–20.0 mg / cm³. 3 It can adsorb various oils and organic solvents such as mineral oil, vacuum pump oil, engine oil, ethanol, chloroform and soybean oil, with an adsorption range of 56-190 g / g; the aerogel has good oil retention performance, with an oil retention rate of up to 94%; the contact angle reaches 150-165°, and it has superhydrophobicity;
[0024] 3. The kapok / polyester composite aerogel of the present invention can be reused by direct extrusion, and the number of cycles can reach more than 50 times. The aerogel of the present invention exhibits good hydrophobic and oleophilic properties, and can be used in the field of oil-water separation or as a filter material. At the same time, the adsorbed oil can also be recovered, making it an adsorbent material with good development prospects. Attached Figure Description
[0025] Figure 1 The aerogel prepared in Example 1 selectively adsorbs chloroform in a mixture of water and chloroform; wherein, (a) the aerogel is held in water with tweezers; (b) the aerogel selectively adsorbs chloroform without adsorbing water in a mixture of water and chloroform; and (c) the aerogel is removed after completely adsorbing chloroform in the water.
[0026] Figure 2 A device for intercepting floating oil on the water surface.
[0027] Figure 3 The aerogel prepared in Example 3 was repeatedly folded and twisted without changing its shape; wherein, (a) the aerogel can be cut into a heart shape and can return to its original shape after being folded; (b) the aerogel cut into a long strip can return to its original shape after being twisted. Detailed Implementation
[0028] To make the present invention more apparent and understandable, preferred embodiments are described in detail below.
[0029] All raw materials used in the following examples are commercially available products.
[0030] Example 1
[0031] This embodiment provides a method for preparing a kapok / polyester composite aerogel adsorbent material. Kapok cellulose obtained after mechanical grinding and core-sheath structured polyester fibers are mixed to form a uniform suspension. The pH of the solution is adjusted to acidic, and vinyltrimethoxysilane is added for hydrophobic modification. After freezing, the kapok / polyester composite aerogel is prepared by freeze-drying. The specific operation steps are as follows:
[0032] Step 1: Preparation of Kapok / Polyester Mixed Suspension:
[0033] Short kapok fibers with a diameter of approximately 15-45 μm, a length distribution range of approximately 300-1000 μm, and a hollowness of approximately 80-90% were placed in an 8 wt% NaOH solution and treated at 80℃ for 1 hour to remove wax and other impurities from the surface of the kapok fibers. The fibers were then washed with deionized water until neutralized, yielding microfibrillated kapok fibers. Deionized water was added to the microfibrillated kapok fibers, and the treated kapok fibers were then mechanically ground to obtain a uniform kapok fiber suspension. Then... Polyester short fibers with a core-sheath structure and a length distribution range of approximately 400-1000 μm (sheath melting point of 240℃, core melting point of 100℃, diameter of approximately 15-25 μm, length distribution range of approximately 200-1200 μm, purchased from Yangzhou Tianlun Fiber Co., Ltd.) were placed in a suspension and stirred until homogeneous. The suspension was then stirred with a magnetic stirrer at room temperature for 2 hours to prepare a fiber mixed suspension with a total mass fraction of 0.3 wt% (0.2 wt% kapok and 0.1 wt% polyester).
[0034] Step 2: Hydrophobic modification of the kapok / polyester mixed suspension:
[0035] Adjust the pH of the mixed suspension obtained in step one to 4-5 using hydrochloric acid, add 0.4 mL of methyltrimethoxysilane to the suspension using a pipette, and stir with a magnetic stirrer at 800 rpm for 3 hours.
[0036] Step 3: Preparation of Kapok / Polyester Composite Aerogel:
[0037] The modified suspension prepared in step two was placed in a mold and frozen at -25°C for 10 hours. Next, it was freeze-dried at -65°C for 48 hours using a vacuum freeze dryer to obtain a kapok / polyester composite aerogel. The aerogel was then heated in an oven at 120°C for 20 minutes.
[0038] The aerogel prepared in this embodiment (3cm×3cm×3cm) had a measured density of 5.3 mg / cm³. 3 With a contact angle of 155°, when placed in a mixed solution of water and vegetable oil (water to vegetable oil volume ratio 50:1), the aerogel rapidly and selectively adsorbs the oil from the mixed solution, leaving water behind, with an adsorption ratio of 102 g / g. Meanwhile, as... Figure 1 As shown, the prepared aerogel (3cm×3cm×3cm in size) was placed in a mixture of water and chloroform (volume ratio of water to chloroform 50:1). The aerogel could also selectively adsorb chloroform from the mixture of water and chloroform, with an adsorption rate of 150g / g.
[0039] The aerogel prepared in this embodiment can also be used to filter out the oil from the oil-water mixture using a continuous pump suction method. The operation method is as follows: place the aerogel (10cm×10cm×5cm in size) at the head of the tube connected to the suction pump and put it into a mixed solution of vegetable oil and water (volume ratio of vegetable oil to water 30:1). Turn on the pump to continuously suction the mixture. It was found that the aerogel can selectively filter out and recover the oil in the mixed solution.
[0040] Example 2
[0041] This embodiment provides a method for preparing a kapok / polyester composite aerogel adsorbent material. Kapok cellulose obtained after cutting and mechanical grinding is mixed with core-sheath structured polyester fibers to form a uniform suspension. The pH of the solution is adjusted to acidic, and vinyltrimethoxysilane is added for hydrophobic modification. After freezing, the kapok / polyester composite aerogel is prepared by freeze-drying. The specific operation steps are as follows:
[0042] Step 1: Preparation of Kapok / Polyester Mixed Suspension:
[0043] Short kapok fibers with a diameter of approximately 15-45 μm, a length distribution range of approximately 400-1100 μm, and a hollowness of approximately 80-90% were placed in a 10 wt% NaOH solution and treated at 110℃ for 1 hour to remove wax and other impurities from the surface of the kapok fibers. The fibers were then washed with deionized water until neutralized, yielding microfibrillated kapok fibers. Deionized water was added to the microfibrillated kapok fibers, and the treated kapok fibers underwent further microfibrillation treatment to obtain a uniform kapok fiber suspension. Then... Polyester short fibers with a core-sheath structure and a length distribution range of approximately 400-1000 μm (sheath melting point of 240℃, core melting point of 100℃, diameter of approximately 15-25 μm, length distribution range of approximately 200-1200 μm, purchased from Yangzhou Tianlun Fiber Co., Ltd.) were placed in a suspension and stirred until homogeneous. The suspension was then stirred with a magnetic stirrer at room temperature for 2 hours to prepare a mixed fiber suspension with a total mass fraction of 0.8 wt% (0.6 wt% kapok and 0.2 wt% polyester).
[0044] Step 2: Hydrophobic modification of the kapok / polyester mixed suspension:
[0045] The pH of the mixed suspension obtained in step one was adjusted to 4-5 using acetic acid. 0.4 mL of vinyltrimethoxysilane was added to the suspension using a pipette, and the mixture was stirred for 3 hours at 800 rpm using a magnetic stirrer.
[0046] Step 3: Preparation of Kapok / Polyester Composite Aerogel:
[0047] The modified suspension prepared in step two was placed in a mold and frozen at -196°C in liquid nitrogen for 5 minutes. Next, it was freeze-dried at -65°C for 48 hours using a vacuum freeze dryer to obtain a kapok / polyester composite aerogel. The aerogel was then placed in an oven and heated at 110°C for 30 minutes.
[0048] The density of the 10cm×10cm×4cm kapok / polyester composite aerogel prepared in this embodiment is 16.8mg / cm³. 3 With a contact angle of 165°, it was used to intercept filter media placed in a flowing water / oil mixture. A schematic diagram of the testing apparatus is shown below. Figure 2 As shown, when the aerogel was inserted into the middle of a water tank, a mixture of vegetable oil and water (volume ratio of vegetable oil to water 30:1) was poured into the tank from the left. It was found that the oil was successfully intercepted by the aerogel on the left side of the tank, leaving clear water on the right side. The kapok / polyester composite aerogel exhibited excellent oil interception and filtration performance.
[0049] Example 3
[0050] This embodiment provides a method for preparing a kapok / polyester composite aerogel adsorbent material. Mechanically processed kapok cellulose and core-sheath structured polyester fibers are mixed to form a uniform suspension. The pH of the solution is adjusted to acidic, and methyltrimethoxysilane is added for hydrophobic modification. After freezing, the microfibrillated kapok / polyester composite aerogel is prepared using a freeze-drying method. The specific operation steps are as follows:
[0051] Step 1: Preparation of the Kapok / Polyester Mixed Suspension:
[0052] Short kapok fibers with a diameter of approximately 15-45 μm, a length distribution range of approximately 200-1100 μm, and a hollowness of approximately 80-90% were placed in a 10 wt% NaOH solution and treated at 80°C for 1 hour to remove wax and other impurities from the surface of the kapok fibers. The fibers were then washed with deionized water until neutralized, yielding microfibrillated kapok fibers. Deionized water was added to the microfibrillated kapok fibers, and the treated kapok fibers were then mechanically processed to obtain a uniform kapok fiber suspension. Longer fibers were then... Polyester short fibers with a core-sheath structure (sheath melting point of 240℃, core melting point of 100℃, diameter of approximately 15-25μm, length distribution of approximately 200-1200μm, purchased from Yangzhou Tianlun Fiber Co., Ltd.) with a diameter distribution range of approximately 400-1000μm were placed in a suspension and stirred until homogeneous. The suspension was then stirred with a magnetic stirrer at room temperature for 2 hours to prepare a mixed fiber suspension with a total mass fraction of 0.4wt% (0.3wt% kapok and 0.1wt% polyester).
[0053] Step 2: Hydrophobic modification of the kapok / polyester mixed suspension:
[0054] Adjust the pH of the mixed suspension obtained in step one to 4-5 using hydrochloric acid, add 0.4 mL of methyltrimethoxysilane to the suspension using a pipette, and stir with a magnetic stirrer at 800 rpm for 3 hours.
[0055] Step 3: Preparation of Kapok / Polyester Composite Aerogel:
[0056] The modified suspension prepared in step two was placed in a mold and frozen at -196°C in liquid nitrogen for 5 minutes. Next, it was freeze-dried at -65°C for 48 hours using a vacuum freeze dryer to obtain a kapok / polyester composite aerogel. The aerogel was then heated in an oven at 150°C for 10 minutes.
[0057] The 6cm×6cm×2cm kapok / polyester composite aerogel prepared in this embodiment exhibits excellent mechanical properties. It can be bent, rotated, cut, and repeatedly compressed without changing its shape or collapsing its structure. Figure 3 As shown, the aerogel can be recycled by directly squeezing out the oil inside through external force. After squeezing, the aerogel can return to its original shape and be reused through oil absorption and squeezing. Tests showed that the oil recovery efficiency of this method is higher than 80%. At the same time, after 50 repeated squeezing and use, the oil absorption ratio of the aerogel decreases by about 20% and gradually stabilizes at about 70g / g, showing good reusability.
[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make several improvements and additions without departing from the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a kapok / polyester composite aerogel, characterized in that, Includes the following steps: Step 1: Treat the short kapok fibers with NaOH solution, then wash them with deionized water until neutral to obtain microfibrillated kapok fibers; Deionized water was added to the microfibrillated kapok fibers, and then the fibers were mechanically ground in a pulping machine to obtain a kapok fiber suspension. Step 2: Place the polyester staple fiber with a core-sheath structure into the kapok fiber suspension obtained in Step 1 to obtain a fiber composite suspension; Step 3: Adjust the pH of the fiber composite suspension obtained in Step 2 to acidic, then add silane coupling agent to it, stir and react at room temperature to obtain a modified mixed fiber suspension. Step 4: The modified mixed fiber suspension obtained in Step 3 is first frozen at low temperature, then freeze-dried under vacuum, and then heated in an oven to obtain kapok / polyester composite aerogel.
2. The preparation method according to claim 1, characterized in that, The treatment of short kapok fibers with NaOH solution in step 1 is as follows: the short kapok fibers are placed in NaOH solution and stirred at 60~130℃ for 1~2 h; the concentration of the NaOH solution is 1.0-20.0 wt%.
3. The preparation method according to claim 1, characterized in that, The mass fraction of microfibrillated kapok fibers in the kapok fiber suspension obtained in step 1 is 0.1~5.0 wt%; the diameter of the short kapok fibers is 15-45 μm, the hollowness is 80-90%, and the length distribution is 100-2000 μm.
4. The preparation method according to claim 1, characterized in that, The polyester staple fiber used in step 2 has a sheath melting point of 230-260℃ and a core melting point of 80-100℃; the polyester staple fiber has a length distribution of 200-3000 μm and a diameter of 15-25 μm; the polyester staple fiber has a mass fraction of 0.1-5.0 wt% in the fiber composite suspension.
5. The preparation method according to claim 1, characterized in that, The silane coupling agent in step 3 is vinyltrimethoxysilane or methyltrimethoxysilane; the pH value is adjusted to 3-5 by using an acid, namely hydrochloric acid or acetic acid; the mass fraction of the silane coupling agent in the fiber composite suspension is 0.1-8 wt%; the stirring reaction conditions are: stirring speed 600-800 rpm, time 3-5 h.
6. The preparation method according to claim 1, characterized in that, The specific conditions for low-temperature freeze forming in step 4 are: freezing at -20~-25℃ for 10-24 h or freezing at liquid nitrogen at -196℃ for 2-10 min; the conditions for vacuum freeze drying are: temperature -60~-70℃, time 24-48 h; the heating conditions are: heating at 110-160℃ for 10-30 min.
7. The kapok / polyester composite aerogel prepared by the preparation method according to any one of claims 1-6.
8. The application of the kapok / polyester composite aerogel according to claim 7 in oil or organic solvent adsorption or oil-water separation.
9. The application according to claim 8, characterized in that, The kapok / polyester composite aerogel adsorbs one or more of mineral oil, vegetable oil, vacuum pump oil, machine oil, soybean oil, and organic solvents.
10. The application according to claim 8, characterized in that, The organic solvent includes one or more of dimethyl sulfoxide, toluene, N,N-dimethylformamide, chloroform, ethanol, isopropanol, and acetone.