Cotton cellulose and a method for preparing the same

Abstract

The application provides a cotton cellulose and a preparation method thereof. The preparation method of the cotton cellulose of the application first processes waste cotton fabric through mechanical pulverization to cause peeling or slipping between fiber crystal surfaces, and breaks the cotton fibers into short fibers to obtain cotton short fibers; and then processes the cotton short fibers through DES under mild conditions to make the cotton short fibers swell and change the intermolecular or intramolecular hydrogen bond network of the fibers to different degrees to obtain cotton fiber products with different polymerization degrees; through the two-step processing of the application, the cellulose products with specific crystallinity and polymerization degree are obtained while the integrity of the original cotton structure is retained; and by adjusting the structure and composition of the DES, the cellulose with different crystallinity and polymerization degree can be prepared, the recycling efficiency of the waste cotton fabric is effectively improved, and the application has good economic benefits and application value.

Description

Technical Field

[0001] This invention belongs to the field of textile resource recycling technology, and particularly relates to cotton cellulose and its preparation method. Background Technology

[0002] With economic development and improved living standards, the pace of textile iteration has accelerated significantly, while the lifespan of textiles has shortened dramatically. This has led to a surge in the quantity of waste textiles, resulting in a large amount of waste cotton fabrics. Waste cotton textiles are mainly composed of high-purity cellulose. Cellulose is a large polysaccharide composed of D-glucose linked by β-1,4 glycosidic bonds. It contains numerous polar hydroxyl groups, which form a large number of hydrogen bonds. Hydrogen bonds are relatively strong valence bonds. Intramolecular hydrogen bonds provide rigidity to the molecular chain, while intermolecular hydrogen bonds enable linear polymer molecules to assemble into sheet-like structures, allowing cellulose molecules to stack vertically and form a stable network structure. Due to variations in the number of glucose residues, glycosidic bond connections, and arrangement of the cellulose macromolecular chains, cellulose from different sources exhibits significant differences in properties such as degree of polymerization, solubility, and viscosity. This greatly affects the dissolution, regeneration, and high-value application of cellulose, and to some extent limits the application of waste cotton textiles.

[0003] Given the current shortcomings in the recycling of waste cotton textiles, it is necessary to improve it. Summary of the Invention

[0004] In view of this, the present invention proposes a cotton cellulose and its preparation method. The present invention can controllably prepare cellulose products with adjustable degree of polymerization by structural design of the eutectic solvent.

[0005] The present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing cotton cellulose, comprising the following steps:

[0007] Waste cotton fabrics are shredded to obtain short cotton fibers;

[0008] The hydrogen bond acceptor and hydrogen bond donor are dissolved by heating to obtain a eutectic solvent;

[0009] Cotton staple fibers and a eutectic solvent are mixed and subjected to a hydrothermal reaction. The solid phase is separated and dried to obtain cotton cellulose.

[0010] Preferably, the hydrogen bond acceptor is citric acid, and the hydrogen bond donor includes any one of glycerol, ethylene glycol, glycine, alanine, L-cysteine, arginine, and water.

[0011] Alternatively, the hydrogen bond acceptor is caffeic acid, and the hydrogen bond donor includes any one of glycerol, ethylene glycol, octanol, and water;

[0012] Alternatively, the hydrogen bond acceptor is choline chloride, and the hydrogen bond donor includes any one of urea, glycerol, lactic acid, malonic acid, malic acid, citric acid, and a mixture of water;

[0013] Alternatively, the hydrogen bond acceptor is betaine, and the hydrogen bond donor includes any one of urea, glycerol, lactic acid, malonic acid, citric acid, glucose, and water;

[0014] Alternatively, the hydrogen bond acceptor is zinc chloride, and the hydrogen bond donor comprises a mixture of glycerol and water;

[0015] Alternatively, the hydrogen bond acceptor is potassium carbonate, and the hydrogen bond donor comprises a mixture of glycerol and water;

[0016] Alternatively, the hydrogen bond acceptor is DBU, and the hydrogen bond donor comprises a mixture of glycerol and water;

[0017] Alternatively, the hydrogen bond acceptor is DBN, and the hydrogen bond donor comprises a mixture of glycerol and water;

[0018] Alternatively, the hydrogen bond acceptor may be coumarin, and the hydrogen bond donor may comprise a mixture of cyclohexanol and water.

[0019] Preferably, when the hydrogen bond acceptor is citric acid and the hydrogen bond donor includes any one of glycerol, ethylene glycol, glycine, alanine, L-cysteine, arginine and water, the molar ratio of citric acid to any one of glycerol, ethylene glycol, glycine, alanine, L-cysteine, arginine and water is (1-2):(1-2):(1-4).

[0020] When the hydrogen bond acceptor is caffeic acid and the hydrogen bond donor includes any one of glycerol, ethylene glycol, octanol and water, the molar ratio of caffeic acid to any one of glycerol, ethylene glycol, octanol and water is (1-2):(1-2):(1-4).

[0021] When the hydrogen bond acceptor is choline chloride, and the hydrogen bond donor includes any one of urea, glycerol, lactic acid, malonic acid, malic acid, citric acid and water, the molar ratio of choline chloride to any one of urea, glycerol, lactic acid, malonic acid, malic acid, citric acid and water is (1-2):(1-2):(1-4).

[0022] When the hydrogen bond acceptor is betaine, and the hydrogen bond donor includes any one of urea, glycerol, lactic acid, malonic acid, citric acid, glucose and water, the molar ratio of betaine to any one of urea, glycerol, lactic acid, malonic acid, citric acid, glucose and water is (1-2):(1-2):(1-4).

[0023] When the hydrogen bond acceptor is zinc chloride and the hydrogen bond donor comprises a mixture of glycerol and water, the molar ratio of zinc chloride, glycerol and water is (1-2):(1-2):(1-4);

[0024] When the hydrogen bond acceptor is potassium carbonate and the hydrogen bond donor comprises a mixture of glycerol and water, the molar ratio of potassium carbonate, glycerol and water is (1-2):(1-2):(1-4);

[0025] When the hydrogen bond acceptor is DBU and the hydrogen bond donor comprises a mixture of glycerol and water, the molar ratio of DBU, glycerol and water is (1-2):(1-2):(1-4);

[0026] When the hydrogen bond acceptor is DBN and the hydrogen bond donor comprises a mixture of glycerol and water, the molar ratio of DBN, glycerol and water is (1-2):(1-2):(1-4);

[0027] When the hydrogen bond acceptor is coumarin and the hydrogen bond donor comprises a mixture of cyclohexanol and water, the molar ratio of coumarin, cyclohexanol and water is (1-2):(1-2):(1-4).

[0028] Preferably, in the step of mixing cotton staple fibers and eutectic solvent and then carrying out a hydrothermal reaction, the hydrothermal reaction temperature is 30–90°C and the time is 1–12 h.

[0029] Preferably, in the step of mixing cotton staple fiber and eutectic solvent and then carrying out a hydrothermal reaction, the mass ratio of cotton staple fiber to eutectic solvent is 1:(5-30).

[0030] Preferably, cotton staple fibers and a eutectic solvent are mixed and then subjected to a hydrothermal reaction. After the hydrothermal reaction is completed, a reaction solution is obtained.

[0031] Add a mixed solvent of ethanol and water to the reaction solution, stir, separate the solid and liquid phases, collect the solid phase, wash and dry it to obtain cotton cellulose;

[0032] The volume ratio of the mixed solvent of ethanol and water to the reaction solution is (0.5–3):1;

[0033] In a mixed solvent of ethanol and water, the volume ratio of ethanol to water is (7-9):(1-3).

[0034] Preferably, a mixed solvent of ethanol and water is added to the reaction solution, stirred, and the solid and liquid phases are separated. The solid phase and liquid phase are collected, and the liquid phase is rotary evaporated and dried to obtain a eutectic solvent.

[0035] The washing process involves first washing the solid phase with an ethanol-water mixture, and then washing it with water until it is neutral. The volume ratio of ethanol to water in the ethanol-water mixture is (7-9):(1-3).

[0036] Preferably, waste cotton fabrics are placed in a shear shredder and shredded at 1500-2000 r / min to obtain cotton staple fibers;

[0037] The cotton staple fiber has a diameter of 10–20 μm and a length of 100–250 μm;

[0038] The waste cotton fabrics include at least one of denim, plain weave, corduroy, and varnish.

[0039] Secondly, the present invention also provides cotton cellulose, which is prepared by the preparation method described above.

[0040] The cotton cellulose and its preparation method of the present invention have the following advantages over the prior art:

[0041] The method for preparing cotton cellulose of the present invention first involves mechanically pulverizing waste cotton fabrics to cause peeling or slippage between fiber crystal faces, breaking the cotton fibers into short fibers, thus obtaining cotton short fibers. Then, the cotton short fibers are treated with DES under mild conditions to swell the fibers and cause varying degrees of change in the intermolecular or intramolecular hydrogen bond network, resulting in cotton fiber products with different degrees of polymerization. Through this two-step process, cellulose products with specific crystallinity and polymerization degrees are obtained while preserving the integrity of the original cotton structure. By adjusting the structure and composition of DES, cellulose with different crystallinity and polymerization degrees can be controlled, effectively improving the recycling efficiency of waste cotton fabrics and demonstrating good economic benefits and application value. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 The images are scanning electron microscope images of waste cotton fabric, short cotton fibers after mechanical pulverization, and cotton fibers after DES treatment in Example 1 of the present invention.

[0044] Figure 2 The XRD patterns are of waste cotton fabric, short cotton fibers after mechanical pulverization, and cotton fibers after DES treatment in Example 1 of this invention.

[0045] Figure 3 Fourier transform infrared spectra of cotton fibers after different DES treatments;

[0046] Figure 4Powder X-ray diffraction patterns of cotton fibers after different DES treatments. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0048] To better understand the invention and not to limit its scope, all figures indicating amounts, percentages, and other numerical values ​​used in this application should, in all cases, be understood to be modified by the word "approximately." Therefore, unless specifically stated otherwise, the numerical parameters listed in the specification and appended claims are approximate values ​​and may vary depending on the desired properties being sought. Each numerical parameter should at least be considered as obtained based on reported significant figures and through conventional rounding methods.

[0049] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single digits within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0050] This invention provides a method for preparing cotton cellulose, comprising the following steps:

[0051] S1. After cutting up waste cotton fabrics, cotton staple fibers are obtained;

[0052] S2. Dissolve the hydrogen bond acceptor and hydrogen bond donor by heating to obtain a eutectic solvent;

[0053] S3. After mixing cotton staple fiber and eutectic solvent, a hydrothermal reaction is carried out to separate the solid phase, which is then dried to obtain cotton cellulose.

[0054] The eutectic solvent (DES) of this invention is a liquid eutectic mixture composed of hydrogen bond donors and hydrogen bond acceptors. These are bonded together by hydrogen bonds, exhibiting a designable structure and adjustable properties. By disrupting initial hydrogen bonds and forming new ones, the eutectic solvent effectively breaks the hydrogen bond network between or within cellulose molecules, providing an effective way to alter the intrinsic hydrogen bond structure and physicochemical properties of cellulose. DES composed of different hydrogen bond donors and acceptors possess different acidity, alkalinity, hydrophilicity, polarity, and other physicochemical properties. During DES treatment, the rearrangement of hydrogen bonds at different positions and in different time sequences leads to structural changes in cellulose, making the production of cellulose with specific molecular weights possible. Leveraging the environmentally friendly advantages of DES, by designing and controlling the solvent, molecular scissors are used to cleave hydrogen bonds, and the solvent acts as an acceptor to bind with hydrogen bond donors, forming new hydrogen bonds with higher bond energy and more stable structures. This effectively disrupts the original hydrogen bonds between hydroxyl groups, allowing for the control of the hydrogen bond content and strength in DES, resulting in cellulose products with different degrees of crystallinity and polymerization.

[0055] The method for preparing cotton cellulose of the present invention first involves mechanically pulverizing waste cotton fabrics to cause peeling or slippage between fiber crystal faces, breaking the cotton fibers into short fibers, thus obtaining cotton short fibers. Then, the cotton short fibers are treated with DES under mild conditions to swell the fibers and cause varying degrees of change in the intermolecular or intramolecular hydrogen bond network, resulting in cotton fiber products with different degrees of polymerization. Through this two-step process, cellulose products with specific crystallinity and polymerization degrees are obtained while preserving the integrity of the original cotton structure. By adjusting the structure and composition of DES, cellulose with different crystallinity and polymerization degrees can be controlled, effectively improving the recycling efficiency of waste cotton fabrics and demonstrating good economic benefits and application value.

[0056] In some embodiments, the hydrogen bond acceptor is citric acid, and the hydrogen bond donor includes any one of glycerol (i.e., glycerol), ethylene glycol, glycine, alanine, L-cysteine, arginine, and water.

[0057] In some embodiments, the hydrogen bond acceptor is caffeic acid (i.e., 3,4-dihydroxycinnamic acid), and the hydrogen bond donor includes any one of glycerol, ethylene glycol, octanol, and a mixture of water.

[0058] In some embodiments, the hydrogen bond acceptor is choline chloride (i.e., 2-hydroxyethyltrimethylammonium chloride), and the hydrogen bond donor includes any one of urea, glycerol, lactic acid, malonic acid, malic acid, citric acid, and a mixture of water.

[0059] In some embodiments, the hydrogen bond acceptor is betaine (i.e., N,N,N-trimethylglycine), and the hydrogen bond donor includes any one of urea, glycerol, lactic acid, malonic acid, citric acid, glucose, and water.

[0060] In some embodiments, the hydrogen bond acceptor is zinc chloride, and the hydrogen bond donor includes a mixture of glycerol and water;

[0061] In some embodiments, the hydrogen bond acceptor is potassium carbonate, and the hydrogen bond donor includes a mixture of glycerol and water;

[0062] In some embodiments, the hydrogen bond acceptor is DBU, and the hydrogen bond donor includes a mixture of glycerol and water;

[0063] In some embodiments, the hydrogen bond acceptor is DBN, and the hydrogen bond donor includes a mixture of glycerol and water;

[0064] In some embodiments, the hydrogen bond acceptor is coumarin, and the hydrogen bond donor includes a mixture of cyclohexanol and water.

[0065] In some embodiments, when the hydrogen bond acceptor is citric acid and the hydrogen bond donor includes any one of glycerol, ethylene glycol, glycine, alanine, L-cysteine, arginine and water, the molar ratio of citric acid to any one of glycerol, ethylene glycol, glycine, alanine, L-cysteine, arginine and water is (1-2):(1-2):(1-4).

[0066] In some embodiments, when the hydrogen bond acceptor is caffeic acid and the hydrogen bond donor includes any one of glycerol, ethylene glycol, octanol and water, the molar ratio of caffeic acid to any one of glycerol, ethylene glycol, octanol and water is (1-2):(1-2):(1-4).

[0067] In some embodiments, when the hydrogen bond acceptor is choline chloride and the hydrogen bond donor includes any one of urea, glycerol, lactic acid, malonic acid, malic acid, citric acid and water, the molar ratio of choline chloride to any one of urea, glycerol, lactic acid, malonic acid, malic acid, citric acid and water is (1-2):(1-2):(1-4).

[0068] In some embodiments, when the hydrogen bond acceptor is betaine and the hydrogen bond donor includes any one of urea, glycerol, lactic acid, malonic acid, citric acid, glucose and water, the molar ratio of betaine to any one of urea, glycerol, lactic acid, malonic acid, citric acid, glucose and water is (1-2):(1-2):(1-4).

[0069] In some embodiments, when the hydrogen bond acceptor is zinc chloride and the hydrogen bond donor comprises a mixture of glycerol and water, the molar ratio of zinc chloride, glycerol and water is (1-2):(1-2):(1-4).

[0070] In some embodiments, when the hydrogen bond acceptor is potassium carbonate and the hydrogen bond donor comprises a mixture of glycerol and water, the molar ratio of potassium carbonate, glycerol and water is (1-2):(1-2):(1-4).

[0071] In some embodiments, when the hydrogen bond acceptor is DBU (i.e., 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), with the molecular formula C9H... 16 When the hydrogen bond donor includes a mixture of glycerol and water, the molar ratio of DBU, glycerol and water is (1-2):(1-2):(1-4).

[0072] In some embodiments, when the hydrogen bond acceptor is DBN (i.e., 1,5-diazabicyclo[4.3.0]-5-nonene (DBN), molecular formula C 15 H 14 When the hydrogen bond donor includes a mixture of glycerol and water, the molar ratio of DBN, glycerol and water is (1-2):(1-2):(1-4).

[0073] In some embodiments, when the hydrogen bond acceptor is coumarin and the hydrogen bond donor comprises a mixture of cyclohexanol and water, the molar ratio of the coumarin, cyclohexanol and water is (1-2):(1-2):(1-4).

[0074] In some embodiments, in the step of mixing cotton staple fibers and eutectic solvent and then carrying out a hydrothermal reaction, the hydrothermal reaction temperature is 30–90°C and the time is 1–12 h.

[0075] In some embodiments, in the step of mixing cotton staple fiber and eutectic solvent and then carrying out a hydrothermal reaction, the mass ratio of cotton staple fiber to eutectic solvent is 1:(5-30).

[0076] In some embodiments, cotton staple fibers and a eutectic solvent are mixed and then subjected to a hydrothermal reaction. After the hydrothermal reaction is completed, a reaction solution is obtained.

[0077] Add a mixed solvent of ethanol and water to the reaction solution, stir, separate the solid and liquid phases, collect the solid phase, wash and dry it to obtain cotton cellulose;

[0078] The volume ratio of the mixed solvent of ethanol and water to the reaction solution is (0.5–3):1;

[0079] In a mixed solvent of ethanol and water, the volume ratio of ethanol to water is (7-9):(1-3).

[0080] In some embodiments, a mixed solvent of ethanol and water is added to the reaction solution, stirred, and the solid and liquid phases are separated. The solid phase and the liquid phase are collected, and the liquid phase is rotary evaporated and dried to obtain a eutectic solvent.

[0081] The washing process involves first washing the solid phase with an ethanol-water mixture, and then washing it with water until it is neutral. The volume ratio of ethanol to water in the ethanol-water mixture is (7-9):(1-3).

[0082] In some embodiments, waste cotton fabrics include fibers, yarns, and fabrics, without limitation on color and fiber fineness, and cotton yarns include some mixed off-the-shelf and severely damaged cotton yarns from the factory.

[0083] In some embodiments, waste cotton fabrics include denim, plain weave, corduroy, and varnish, etc.

[0084] In some embodiments, waste cotton fabrics are placed in a shear shredder and shredded at 1500-2000 r / min to obtain cotton staple fibers;

[0085] Cotton staple fibers have a diameter of 10–20 μm and a length of 100–250 μm.

[0086] Based on the same inventive concept, the present invention also provides cotton cellulose, which is prepared by the above-described preparation method.

[0087] The following specific embodiments further illustrate the preparation method of cotton cellulose according to this application. This section further illustrates the content of the present invention in conjunction with specific embodiments, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0088] In the following examples and comparative examples, the waste cotton fabrics are undyed cotton fabrics from Wuhan Textile Group Co., Ltd., specifically 30×30 cotton fabrics with a yarn count of 68×68.

[0089] Example 1

[0090] This application provides a method for preparing cotton cellulose, comprising the following steps:

[0091] S1. Place the waste cotton fabric in a shear shredder and shred it at 1500 r / min to obtain cotton staple fiber; the average diameter of the cotton staple fiber is 20 μm and the average length is 150 μm.

[0092] S2. The hydrogen bond acceptor and hydrogen bond donor are mixed and heated to 70°C to dissolve, resulting in a eutectic solvent; wherein the hydrogen bond acceptor is citric acid, and the hydrogen bond donor is a mixture of glycerol and water, with a molar ratio of citric acid, glycerol and water of 1:2:4.

[0093] S3. After mixing cotton staple fiber and eutectic solvent, the mixture is hydrothermally reacted at 60°C for 1 hour. After the hydrothermal reaction is completed, the reaction solution is obtained.

[0094] Add a mixed solvent of ethanol and water to the reaction solution, stir, separate the solid and liquid phases, collect the solid phase, wash and dry it to obtain cotton cellulose;

[0095] The volume ratio of the mixed solvent of ethanol and water to the reaction solution is 2:1.

[0096] In a mixed solvent of ethanol and water, the volume ratio of ethanol to water is 9:1.

[0097] The mass ratio of cotton staple fiber to eutectic solvent is 1:20;

[0098] The washing process is as follows: the solid phase is first washed twice with an ethanol-water mixture, and then washed with true distilled water until neutral. The volume ratio of ethanol to water in the ethanol-water mixture is 9:1.

[0099] Example 2

[0100] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is citric acid, the hydrogen bond donor is a mixture of ethylene glycol and water, and the molar ratio of citric acid, ethylene glycol and water is 1:2:4; the rest of the process is the same as in Example 1.

[0101] Example 3

[0102] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is citric acid, the hydrogen bond donor is a mixture of glycine and water, and the molar ratio of citric acid, glycine and water is 1:1:4; the rest of the process is the same as in Example 1.

[0103] Example 4

[0104] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is citric acid, the hydrogen bond donor is a mixture of alanine and water, and the molar ratio of citric acid, alanine and water is 1:1:4; the rest of the process is the same as in Example 1.

[0105] Example 5

[0106] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is citric acid, the hydrogen bond donor is a mixture of L-cysteine ​​and water, and the molar ratio of citric acid, L-cysteine ​​and water is 1:1:4; the rest of the process is the same as in Example 1.

[0107] Example 6

[0108] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is citric acid, the hydrogen bond donor is a mixture of arginine and water, and the molar ratio of citric acid, arginine and water is 1:1:4; the rest of the process is the same as in Example 1.

[0109] Example 7

[0110] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is caffeic acid, the hydrogen bond donor is a mixture of glycerol and water, and the molar ratio of caffeic acid, glycerol and water is 1:2:1; the rest of the process is the same as in Example 1.

[0111] Example 8

[0112] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is caffeic acid, the hydrogen bond donor is a mixture of ethylene glycol and water, and the molar ratio of caffeic acid, ethylene glycol and water is 1:2:1; the rest of the process is the same as in Example 1.

[0113] Example 9

[0114] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is caffeic acid, the hydrogen bond donor is a mixture of octanol and water, and the molar ratio of caffeic acid, octanol and water is 1:2:1; the rest of the process is the same as in Example 1.

[0115] Example 10

[0116] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is choline chloride, the hydrogen bond donor is a mixture of urea and water, and the molar ratio of choline chloride, urea and water is 1:2:1; the rest of the process is the same as in Example 1.

[0117] Example 11

[0118] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is choline chloride, the hydrogen bond donor is a mixture of glycerol and water, and the molar ratio of choline chloride, glycerol and water is 1:2:1; the rest of the process is the same as in Example 1.

[0119] Example 12

[0120] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is choline chloride, the hydrogen bond donor is a mixture of lactic acid and water, and the molar ratio of choline chloride, lactic acid and water is 1:2:1; the rest of the process is the same as in Example 1.

[0121] Example 13

[0122] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is choline chloride, the hydrogen bond donor is a mixture of malonic acid and water, and the molar ratio of choline chloride, malonic acid and water is 1:2:1; the rest of the process is the same as in Example 1.

[0123] Example 14

[0124] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is choline chloride, the hydrogen bond donor is a mixture of malic acid and water, and the molar ratio of choline chloride, malic acid and water is 1:2:1; the rest of the process is the same as in Example 1.

[0125] Example 15

[0126] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is choline chloride, the hydrogen bond donor is a mixture of citric acid and water, and the molar ratio of choline chloride, citric acid and water is 1:2:1; the rest of the process is the same as in Example 1.

[0127] Example 16

[0128] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is betaine, the hydrogen bond donor is a mixture of urea and water, and the molar ratio of betaine, urea and water is 1:2:1; the rest of the process is the same as in Example 1.

[0129] Example 17

[0130] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is betaine, the hydrogen bond donor is a mixture of glycerol and water, and the molar ratio of betaine, glycerol and water is 1:2:1; the rest of the process is the same as in Example 1.

[0131] Example 18

[0132] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is betaine, the hydrogen bond donor is a mixture of lactic acid and water, and the molar ratio of betaine, lactic acid and water is 1:2:1; the rest of the process is the same as in Example 1.

[0133] Example 19

[0134] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is betaine, the hydrogen bond donor is a mixture of malonic acid and water, and the molar ratio of betaine, malonic acid and water is 1:2:1; the rest of the process is the same as in Example 1.

[0135] Example 20

[0136] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is betaine, the hydrogen bond donor is a mixture of citric acid and water, and the molar ratio of betaine, citric acid and water is 1:2:1; the rest of the process is the same as in Example 1.

[0137] Example 21

[0138] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is betaine, the hydrogen bond donor is a mixture of glucose and water, and the molar ratio of betaine, glucose and water is 1:2:1; the rest of the process is the same as in Example 1.

[0139] Example 22

[0140] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is zinc chloride, the hydrogen bond donor is a mixture of glycerol and water, and the molar ratio of zinc chloride, glycerol and water is 1:2:1; the rest of the process is the same as in Example 1.

[0141] Example 23

[0142] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is potassium carbonate, the hydrogen bond donor is a mixture of glycerol and water, and the molar ratio of potassium carbonate, glycerol and water is 1:2:1; the rest of the process is the same as in Example 1.

[0143] Example 24

[0144] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is DBU, the hydrogen bond donor is a mixture of glycerol and water, and the molar ratio of DBU, glycerol and water is 1:2:1; the rest of the process is the same as in Example 1.

[0145] Example 25

[0146] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is DBN, the hydrogen bond donor is a mixture of glycerol and water, and the molar ratio of DBN, glycerol and water is 1:2:1; the rest of the process is the same as in Example 1.

[0147] Example 26

[0148] The method for preparing cotton cellulose provided in this embodiment is the same as that in Example 1, except that the hydrogen bond acceptor is coumarin, the hydrogen bond donor is a mixture of cyclohexanol and water, and the molar ratio of coumarin, cyclohexanol and water is 1:2:1; the rest of the process is the same as in Example 1.

[0149] Comparative Example 1

[0150] The preparation method of cotton cellulose provided in this comparative example is the same as that in Example 1, except that the hydrogen bond acceptor is coumarin, the hydrogen bond donor is n-octadecyl mercaptan, and the molar ratio of coumarin to n-octadecyl mercaptan is 1:2; the rest of the process is the same as in Example 1.

[0151] Comparative Example 2

[0152] The preparation method of cotton cellulose provided in this comparative example is the same as that in Example 1, except that the hydrogen bond acceptor is coumarin, the hydrogen bond donor is octanol, and the molar ratio of coumarin to octanol is 1:2; the rest of the process is the same as in Example 1.

[0153] Comparative Example 3

[0154] The preparation method of cotton cellulose provided in this comparative example is the same as that in Example 1, except that water is used to replace the eutectic solvent in Example 1; the rest of the process is the same as that in Example 1.

[0155] Example 27

[0156] The method for preparing cotton cellulose provided in this application embodiment is the same as that in Example 1, except that the hydrothermal reaction temperature is 60°C and the time is 0.5h, while the rest of the process is the same as in Example 1.

[0157] Example 28

[0158] The method for preparing cotton cellulose provided in this application embodiment is the same as that in Example 1, except that the hydrothermal reaction temperature is 60°C and the time is 2 hours, while the rest of the process is the same as in Example 1.

[0159] Example 29

[0160] The method for preparing cotton cellulose provided in this application embodiment is the same as that in Example 1, except that the hydrothermal reaction temperature is 60°C and the time is 4 hours, while the rest of the process is the same as in Example 1.

[0161] Example 30

[0162] The method for preparing cotton cellulose provided in this application embodiment is the same as that in Example 1, except that the hydrothermal reaction temperature is 60°C and the time is 8 hours, while the rest of the process is the same as in Example 1.

[0163] Example 31

[0164] The method for preparing cotton cellulose provided in this application embodiment is the same as that in Example 1, except that the hydrothermal reaction temperature is 60°C and the time is 12 hours, while the rest of the process is the same as in Example 1.

[0165] Example 32

[0166] The method for preparing cotton cellulose provided in this application embodiment is the same as that in Example 1, except that the hydrothermal reaction temperature is 20°C and the time is 1 hour, while the rest of the process is the same as in Example 1.

[0167] Example 33

[0168] The method for preparing cotton cellulose provided in this application embodiment is the same as that in Example 1, except that the hydrothermal reaction temperature is 30°C and the time is 1 hour, while the rest of the process is the same as in Example 1.

[0169] Example 34

[0170] The method for preparing cotton cellulose provided in this application embodiment is the same as that in Example 1, except that the hydrothermal reaction temperature is 40°C and the time is 1 hour, while the rest of the process is the same as in Example 1.

[0171] Example 35

[0172] The method for preparing cotton cellulose provided in this application embodiment is the same as that in Example 1, except that the hydrothermal reaction temperature is 50°C and the time is 1 hour, while the rest of the process is the same as in Example 1.

[0173] Example 36

[0174] The method for preparing cotton cellulose provided in this application embodiment is the same as that in Example 1, except that the hydrothermal reaction temperature is 80°C and the time is 1 hour, while the rest of the process is the same as in Example 1.

[0175] Example 37

[0176] The method for preparing cotton cellulose provided in this application embodiment is the same as that in Example 1, except that the hydrothermal reaction temperature is 100°C and the time is 1 hour, while the rest of the process is the same as in Example 1.

[0177] Performance testing

[0178] The crystallinity and degree of polymerization of the cotton cellulose components prepared in the above embodiments and comparative examples were measured, and the corresponding measurement results are shown in Table 1.

[0179] Among them, the degree of polymerization determination:

[0180] The average degree of polymerization of cotton cellulose was determined using a JWC-32C Ubbelohde viscometer in accordance with GB / T1548-2016 "Determination of intrinsic viscosity in copper ethylenediamine (CED) solution for pulp".

[0181]

[0182] DP 0.905 =0.75[η];

[0183] In the formula: ηr is the relative viscosity (mL / g); η0 is the viscosity of copper ethylenediamine (CED) (mL / g); η is the intrinsic viscosity of the sample in the copper ethylenediamine solution (mL / g); K' is an empirical constant, for the cellulose-copper ethylenediamine system, K' = 0.056; ρ is the concentration of the sample in the solvent (g / mL), specifically 0.002 g / mL; DP is the average degree of polymerization of the sample.

[0184] Crystallinity determination:

[0185] X-ray diffraction (XRD) was used to obtain spectra, which were then analyzed using MDI Jade 6.0. The crystallinity index (CrI) was calculated by comparing the minimum intensity before the maximum diffraction peak with the height of the main diffraction peak. For cellulose, it was obtained by comparing the background intensity at 2θ = 18° with the peak height at 2θ = 22.8°.

[0186] Table 1 - Results of crystallinity and degree of polymerization determination of cotton cellulose in Examples 1-26 and Comparative Examples 1-3

[0187]

[0188]

[0189] Table 1 shows that the crystallinity of the raw cotton (i.e., Comparative Example 3) was 71.1%, and the degree of polymerization was 3512. Acidic DES caused greater damage to cotton cellulose than neutral DES. When choline chloride and betaine were used as HBA, the decrease in crystallinity and degree of polymerization of cotton fibers was greater when HBD was an organic acid than when HBD was a polyol. The more carboxyl or hydroxyl groups in HBD, the more significant the decrease in crystallinity and degree of polymerization of cotton fibers. The stronger the acidity of DES, the more severe the damage to the hydrogen bonds of the cellulose molecular chain. When the HBD was the same, betaine was more effective than choline chloride in treating cotton fibers. Metal ion-type DES caused more severe damage to cotton fibers. Hydrophilic DES caused varying degrees of damage to the crystallinity and degree of polymerization of cotton fibers. For example, after treatment with hydrophilic coumarin-cyclohexanol, the crystallinity of cotton fibers decreased by 18%, and the degree of polymerization decreased by about 1000, while the crystallinity and degree of polymerization of cotton fibers did not change significantly after treatment with hydrophobic coumarin-n-octadecyl mercaptan DES and coumarin-octyl alcohol DES. By adjusting the structure and properties of DES, cotton fiber products with a degree of polymerization ranging from 200 to 3500 can be obtained.

[0190] Furthermore, the hydrothermal reaction temperature and time were optimized in Examples 1 and 27-37 to obtain cotton cellulose with different crystallinity and degree of polymerization, and the results are shown in Table 2.

[0191] Table 2 - Results of crystallinity and degree of polymerization determination of cotton cellulose in Examples 1, 27-37

[0192]

[0193] As shown in Table 2, the degree of polymerization and crystallinity of cotton fibers gradually decreased with increasing temperature and processing time. This is because increasing the temperature or extending the reaction time accelerates the movement rate of solvent molecules, strengthens the hydrogen bond interaction between cellulose and the solvent, and further disrupts the intramolecular and intermolecular hydrogen bond network of cellulose. By optimizing the solvent type and process conditions, cotton cellulose products with specific degrees of polymerization and crystallinity can be prepared.

[0194] Figures 1-2 The images shown are scanning electron microscope (SEM) images and FI-IR images of waste cotton fabric, short cotton fibers after mechanical pulverization, and cotton fibers after DES treatment, respectively, in Example 1 of this invention.

[0195] Figures 1-2 In this context, "Cotton" refers to waste cotton fabric, "Cut-Cotton" refers to short cotton fibers after step S1 of Example 1, and "DES-Cotton" refers to cotton cellulose obtained after the final treatment with citric acid-glycerol-water DES in step S3 of Example 1.

[0196] from Figures 1-2 As can be seen, the cut cotton staple fibers are significantly shorter, and there is a small amount of agglomeration during the cutting process. After DES treatment, the fiber crimp is unwound, and the fiber surface is damaged to some extent. Infrared spectroscopy shows that the chemical structure of the fiber is not damaged, and the main characteristic peaks of cotton cellulose do not change after DES treatment, remaining consistent with the original cotton.

[0197] Figure 3 Fourier transform infrared spectra of cotton cellulose after different DES treatments.

[0198] Figure 4 Powder X-ray diffraction patterns of cotton cellulose after different DES treatments.

[0199] Figures 3-4 "Zhongmian" refers to untreated waste cotton fabrics, "citric acid-glycerol" refers to cotton cellulose prepared in Example 1, "caffeic acid-glycerol" refers to cotton cellulose prepared in Example 7, "choline chloride-glycerol" refers to cotton cellulose prepared in Example 11, "betaine-glycerol" refers to cotton cellulose prepared in Example 17, and "potassium carbonate-glycerol" refers to cotton cellulose prepared in Example 23.

[0200] from Figures 3-4 As can be seen, the cotton cellulose samples all exhibited several typical cellulose characteristic peaks, namely 3317 cm⁻¹. -1 (-OH), 2920cm -1 (CH) and 1051cm-1 (CO). The results indicate that the DES treatment occurred under relatively mild conditions, preserving the most characteristic functional groups of the virgin cotton fibers. Three characteristic diffraction peaks of cellulose were observed at 14.9°, 16.5°, and 22.9°, confirming the presence of type I cellulose in both the virgin cotton fibers and the DES-treated samples. Calculations of the CrI values ​​based on the diffraction patterns show that all DES treatments disrupted the crystalline regions of cellulose to some extent, promoting hydrogen bonding or chemical interactions between solvent molecules and cellulose, resulting in an overall decrease in the crystallinity index (CrI) value.

[0201] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing cotton cellulose, characterized in that, Includes the following steps: Waste cotton fabrics are shredded to obtain short cotton fibers; The hydrogen bond acceptor and hydrogen bond donor are dissolved by heating to obtain a eutectic solvent; Cotton staple fiber and eutectic solvent were mixed and subjected to a hydrothermal reaction. The solid phase was separated and dried to obtain cotton cellulose. The hydrogen bond acceptor is citric acid, and the hydrogen bond donor includes a mixture of glycerol, ethylene glycol, and water; the molar ratio of citric acid to glycerol, ethylene glycol, and water is 1:2:

4. Alternatively, the hydrogen bond acceptor is caffeic acid, and the hydrogen bond donor includes any one of glycerol, ethylene glycol, octanol, and water; the molar ratio of caffeic acid to any one of glycerol, ethylene glycol, octanol, and water is 1:2:

1. Alternatively, the hydrogen bond acceptor is choline chloride, and the hydrogen bond donor is a mixture of citric acid and water; when the molar ratio of choline chloride, citric acid, and water is 1:2:

1. Alternatively, the hydrogen bond acceptor is betaine, and the hydrogen bond donor is a mixture of citric acid and water; the molar ratio of betaine, citric acid, and water is 1:2:

1. Alternatively, the hydrogen bond acceptor is zinc chloride, and the hydrogen bond donor comprises a mixture of glycerol and water; the molar ratio of zinc chloride, glycerol, and water is 1:2:

1. Alternatively, when the hydrogen bond acceptor is potassium carbonate and the hydrogen bond donor comprises a mixture of glycerol and water, the molar ratio of potassium carbonate, glycerol and water is 1:2:

1. Alternatively, when the hydrogen bond acceptor is DBU and the hydrogen bond donor comprises a mixture of glycerol and water, the molar ratio of DBU, glycerol and water is 1:2:

1. Alternatively, when the hydrogen bond acceptor is DBN and the hydrogen bond donor comprises a mixture of glycerol and water, the molar ratio of DBN, glycerol and water is 1:2:1; Alternatively, when the hydrogen bond acceptor is coumarin and the hydrogen bond donor comprises a mixture of cyclohexanol and water, the molar ratio of coumarin, cyclohexanol and water is 1:2:1; in the step of mixing cotton staple fiber and eutectic solvent and then carrying out a hydrothermal reaction, the hydrothermal reaction temperature is 60°C and the time is 1 hour. In the step of mixing cotton staple fiber and eutectic solvent and carrying out hydrothermal reaction, the mass ratio of cotton staple fiber to eutectic solvent is 1:

20. Waste cotton fabrics are placed in a shear shredder and shredded at 1500-2000 r / min to obtain cotton staple fibers; The cotton staple fiber has a diameter of 10–20 μm and a length of 100–250 μm.

2. The method for preparing cotton cellulose as described in claim 1, characterized in that, Cotton staple fibers and a eutectic solvent are mixed and subjected to a hydrothermal reaction. After the hydrothermal reaction is completed, a reaction solution is obtained. Add a mixed solvent of ethanol and water to the reaction solution, stir, separate the solid and liquid phases, collect the solid phase, wash and dry it to obtain cotton cellulose; The volume ratio of the mixed solvent of ethanol and water to the reaction solution is (0.5–3):1; In a mixed solvent of ethanol and water, the volume ratio of ethanol to water is (7-9):(1-3).

3. The method for preparing cotton cellulose as described in claim 2, characterized in that, Add a mixed solvent of ethanol and water to the reaction solution, stir, separate the solid and liquid phases, collect the solid and liquid phases, rotary evaporate the liquid phase, dry it, and obtain a eutectic solvent. The washing process involves first washing the solid phase with an ethanol-water mixture, and then washing it with water until it is neutral. The volume ratio of ethanol to water in the ethanol-water mixture is (7-9):(1-3).

4. The method for preparing cotton cellulose as described in claim 1, characterized in that, The waste cotton fabrics include at least one of denim, plain weave, corduroy, and varnish.

5. A type of cotton cellulose, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 4.

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