Cotton cellulose and preparation method thereof

Abstract

The invention provides cotton cellulose and a preparation method thereof. The preparation method of the cotton cellulose comprises the following steps: firstly, treating a waste cotton fabric through mechanical crushing, so that fiber crystal faces are stripped or slip, cotton fibers are broken into short fibers, and cotton short fibers are obtained; the method comprises the following steps: treating cotton short fibers by DES under a mild condition, so that the fibers are swelled and intermolecular or intramolecular hydrogen bond networks of the fibers are changed to different degrees, and cotton fiber products with different polymerization degrees are obtained; through two-step treatment, the integrity of an original cotton structure is reserved, and meanwhile, a cellulose product with specific crystallinity and polymerization degree is obtained; by adjusting the structure and composition of DES, cellulose with different crystallinity degrees and polymerization degrees can be controllably prepared, the recycling efficiency of the waste cotton fabric is effectively improved, and good economic benefits and popularization and application values are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of textile resource regeneration, and in particular relates to cotton cellulose and a preparation method thereof. Background Art

[0002] With the development of the economy and the improvement of people's living standards, the iteration speed of textiles has significantly accelerated, while the use cycle has been drastically shortened, resulting in a rapid increase in the number of waste textiles and a large amount of waste cotton fabrics. Waste cotton textiles are mainly composed of high-purity cellulose. Cellulose is a macromolecular polysaccharide composed of D-glucose with β-1,4 glycosidic bonds. There are a large number of polar group hydroxyl groups in the molecule, and a large number of hydrogen bonds will be formed between them. Hydrogen bonds are a relatively strong valence bond. Intramolecular hydrogen bonds provide molecular chain rigidity. On the other hand, intermolecular hydrogen bonds enable linear polymer molecules to assemble into a sheet structure, allowing cellulose molecules to stack in the vertical direction to form a stable network structure. Due to the differences in the number of glucose residues, glycosidic bond connections and arrangement of the cellulose macromolecular chain, cellulose from different sources has obvious differences in properties such as degree of polymerization, solubility, and viscosity, which greatly affects the dissolution, regeneration and high-value application of cellulose, and also limits the application of waste cotton textiles to a certain extent.

[0003] Based on the defects in the current recycling of waste cotton textiles, it is necessary to improve this. Summary of the invention

[0004] In view of this, the present invention proposes a cotton cellulose and a preparation method thereof. The present invention can control the preparation of a cellulose product with an adjustable degree of polymerization by structurally designing a low 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] After the waste cotton fabric is shredded, cotton staple fibers are obtained;

[0008] The hydrogen bond acceptor and the hydrogen bond donor are heated and dissolved to obtain a deep eutectic solvent;

[0009] The cotton staple fibers and the low eutectic solvent are mixed and subjected to a hydrothermal reaction, and 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 a mixture of any one of glycerol, ethylene glycol, glycine, alanine, L-cysteine, arginine and water;

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

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

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

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

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

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

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

[0018] Alternatively, the hydrogen bond acceptor is coumarin, and the hydrogen bond donor comprises a mixture of cyclohexanol and water.

[0019] Preferably, when the hydrogen bond acceptor is citric acid and the hydrogen bond donor comprises a mixture of any one of glycerol, ethylene glycol, glycine, alanine, L-cysteine, arginine and water, the molar ratio of the 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 a mixture of any one of glycerol, ethylene glycol, octanol and water, the molar ratio of the 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 a mixture of 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 a mixture of any one of urea, glycerol, lactic acid, malonic acid, citric acid, glucose and water, the molar ratio of the 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 the cotton staple fibers and the low eutectic solvent and then subjecting them to a hydrothermal reaction, the hydrothermal reaction temperature is 30 to 90° C. and the reaction time is 1 to 12 hours.

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

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

[0031] adding a mixed solvent of ethanol and water to the reaction solution, stirring, separating the solid and the liquid, collecting the solid phase, washing, and drying 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] The volume ratio of ethanol to water in the mixed solvent of ethanol and water is (7-9):(1-3).

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

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

[0036] Preferably, the waste cotton fabric is placed in a shearing shredder and shredded at 1500-2000 r / min to obtain cotton staple fibers;

[0037] The cotton staple fibers have a diameter of 10 to 20 μm and a length of 100 to 250 μm;

[0038] The waste cotton fabric includes at least one of denim, plain cloth, corduroy and varnish.

[0039] In a second aspect, the present invention further provides cotton cellulose, which is prepared by the preparation method.

[0040] The cotton cellulose and the preparation method thereof of the present invention have the following beneficial effects compared with the prior art:

[0041] The method for preparing cotton cellulose of the present invention comprises the following steps: firstly, waste cotton fabrics are treated by mechanical crushing to make peeling or slippage occur between fiber crystal planes, and the cotton fibers are broken into short fibers to obtain cotton short fibers; the cotton short fibers are treated by DES under mild conditions to make the fibers swell and make the hydrogen bond networks between or within the molecules of the fibers change to different degrees, so as to obtain cotton fiber products with different polymerization degrees; through the two-step treatment of the present invention, cellulose products with specific crystallinity and polymerization degree are obtained while retaining the integrity of the original cotton structure; cellulose with different crystallinity and polymerization degree can be prepared in a controlled manner by adjusting the structure and composition of DES, thereby effectively improving the recycling efficiency of waste cotton fabrics, and having good economic benefits and promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 The scanning electron microscope images of the waste cotton fabric, the cotton staple fibers after mechanical crushing and the cotton fibers after DES treatment in Example 1 of the present invention are shown;

[0044] Figure 2 The XRD diagrams of the waste cotton fabric, the cotton staple fibers after mechanical crushing and the cotton fibers after DES treatment in Example 1 of the present invention are shown;

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

[0046] Figure 4Powder X-ray diffraction patterns of cotton fibers treated with different DES. DETAILED DESCRIPTION

[0047] In order to make the purpose, 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 combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] In order to better understand the present invention but not to limit the scope of the present invention, all the numbers used in this application to express the amount, percentage, and other numerical values ​​should be understood as modified by the word "about" in all cases. Therefore, unless otherwise specified, the numerical parameters listed in the specification and the appended claims are approximate values, which may be changed according to the different ideal properties attempted to be obtained. Each numerical parameter should at least be regarded as obtained based on the reported significant figures and by 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 the embodiments. In addition, in the description of the present application, the term "including" means "including but not limited to". Various embodiments of the present invention may be in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within the 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., as well as single numbers within the numbered range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated in this article, it is meant to include any cited numbers (fractions or integers) within the indicated range.

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

[0051] S1, chopping waste cotton fabrics into pieces to obtain cotton staple fibers;

[0052] S2, heating and dissolving the hydrogen bond acceptor and the hydrogen bond donor to obtain a low eutectic solvent;

[0053] S3, mixing the cotton staple fibers and the low eutectic solvent, performing a hydrothermal reaction, separating the solid phase, and drying to obtain cotton cellulose.

[0054] The low eutectic solvent (DES) of the present invention is a liquid eutectic mixture composed of a hydrogen bond donor and a hydrogen bond acceptor. They are combined with each other through hydrogen bonding, and have the characteristics of designable structure and adjustable properties. The low eutectic solvent can effectively destroy the hydrogen bond network between or within cellulose molecules by destroying the initial hydrogen bonds and forming new hydrogen bonds, and is an effective way to change the intrinsic structure and physicochemical properties of cellulose hydrogen bonds. DES composed of different hydrogen bond donors and hydrogen bond acceptors have different physical and chemical properties such as acidity and alkalinity, hydrophilicity and hydrophobicity, and polarity. During the DES treatment process, the rearrangement of hydrogen bonds at different positions and different time sequences of cellulose will cause the structure of cellulose to change, which makes it possible to produce cellulose of a specific molecular weight. Based on the green and environmentally friendly advantages of DES, by designing and regulating the solvent, using molecular scissors to cut off the combination of hydrogen bonds, and combining with hydrogen bond donors as an acceptor to form new hydrogen bonds with higher bond energy and more stable structure, it can effectively destroy the original hydrogen bonds between hydroxyl groups, regulate the hydrogen bond content and strength of DES, and obtain cellulose products with different crystallinity and polymerization degree.

[0055] The method for preparing cotton cellulose of the present invention comprises the following steps: firstly, waste cotton fabrics are treated by mechanical crushing to make peeling or slippage occur between fiber crystal planes, and the cotton fibers are broken into short fibers to obtain cotton short fibers; the cotton short fibers are treated by DES under mild conditions to make the fibers swell and make the hydrogen bond networks between or within the molecules of the fibers change to different degrees, so as to obtain cotton fiber products with different polymerization degrees; through the two-step treatment of the present invention, cellulose products with specific crystallinity and polymerization degree are obtained while retaining the integrity of the original cotton structure; cellulose with different crystallinity and polymerization degree can be prepared in a controlled manner by adjusting the structure and composition of DES, thereby effectively improving the recycling efficiency of waste cotton fabrics, and having good economic benefits and promotion and application value.

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

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

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

[0059] In some embodiments, the hydrogen bond acceptor is betaine (ie, N,N,N-trimethylglycine), and the hydrogen bond donor includes a mixture of 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 comprises a mixture of glycerol and water;

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

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

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

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

[0065] In some embodiments, when the hydrogen bond acceptor is citric acid and the hydrogen bond donor includes a mixture of 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 a mixture of 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 a mixture of 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 a mixture of 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), having a molecular formula of C9H 16 N2), 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 O), 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 coumarin, cyclohexanol and water is (1-2):(1-2):(1-4).

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

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

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

[0077] adding a mixed solvent of ethanol and water to the reaction solution, stirring, separating the solid and the liquid, collecting the solid phase, washing, and drying 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] The volume ratio of ethanol to water in the mixed solvent of ethanol and water is (7-9):(1-3).

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

[0081] The washing is specifically as follows: the solid phase is first washed with an ethanol-water mixture and then washed with water until it becomes neutral, wherein 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, fabrics, etc., regardless of color and fiber fineness. Cotton yarns include some mixed fallen yarns and severely damaged cotton yarns from factories.

[0083] In some embodiments, the waste cotton fabrics include denim, plain cloth, corduroy, and velvet.

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

[0085] The diameter of cotton staple fibers is 10 to 20 μm and the length is 100 to 250 μm.

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

[0087] The following further illustrates the preparation method of cotton cellulose of the present application with specific examples. This section further illustrates the content of the present invention in conjunction with specific examples, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means adopted in the examples 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 fabric is a natural cotton fabric from Wuhan Textile Group Co., Ltd., specifically a 30×30 yarn count 68×68 cotton fabric.

[0089] Example 1

[0090] The present invention provides a method for preparing cotton cellulose, comprising the following steps:

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

[0092] S2. Mixing a hydrogen bond acceptor and a hydrogen bond donor and heating them to dissolve at 70° C. to obtain a low eutectic solvent; wherein the hydrogen bond acceptor is citric acid, the hydrogen bond donor is a mixture of glycerol and water, and the molar ratio of citric acid, glycerol and water is 1:2:4;

[0093] S3, mixing the cotton staple fiber and the low eutectic solvent and subjecting them to a hydrothermal reaction at 60° C. for 1 hour, and obtaining a reaction solution after the hydrothermal reaction is completed;

[0094] adding a mixed solvent of ethanol and water to the reaction solution, stirring, separating the solid and the liquid, collecting the solid phase, washing, and drying to obtain cotton cellulose;

[0095] Wherein, the volume ratio of the mixed solvent of ethanol and water to the reaction solution is 2:1;

[0096] The volume ratio of ethanol to water in the mixed solvent of ethanol and water is 9:1;

[0097] The mass ratio of cotton staple fiber to low 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 it becomes neutral, wherein 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 processes are the same as those in Example 1.

[0101] Example 3

[0102] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0103] Example 4

[0104] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 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 processes are the same as those in Example 1.

[0107] Example 6

[0108] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0109] Example 7

[0110] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 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 processes are the same as those 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 processes are the same as those in Example 1.

[0115] Example 10

[0116] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0117] Embodiment 11

[0118] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0119] Example 12

[0120] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0121] Embodiment 13

[0122] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0123] Embodiment 14

[0124] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0125] Embodiment 15

[0126] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0127] Example 16

[0128] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0129] Embodiment 17

[0130] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0131] Embodiment 18

[0132] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0133] Embodiment 19

[0134] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0135] Embodiment 20

[0136] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0137] Embodiment 21

[0138] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0139] Embodiment 22

[0140] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0141] Embodiment 23

[0142] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0143] Embodiment 24

[0144] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0145] Embodiment 25

[0146] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 1.

[0147] Embodiment 26

[0148] The method for preparing cotton cellulose provided in this embodiment is the same as that in Embodiment 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 processes are the same as those in Embodiment 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-octadecanethiol, and the molar ratio of coumarin to n-octadecanethiol is 1:2; the rest of the processes are the same as those 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 processes are the same as those in Example 1.

[0153] Comparative Example 3

[0154] The method for preparing cotton cellulose provided in this comparative example is the same as that in Example 1, except that water is used to replace the low eutectic solvent in Example 1; the rest of the processes are the same as those in Example 1.

[0155] Embodiment 27

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

[0157] Embodiment 28

[0158] The method for preparing cotton cellulose provided in the embodiment of the present application is the same as that in Example 1, except that the hydrothermal reaction temperature is 60° C. and the reaction time is 2 h, and the rest of the processes are the same as those in Example 1.

[0159] Embodiment 29

[0160] The method for preparing cotton cellulose provided in the embodiment of the present application is the same as that in Example 1, except that the hydrothermal reaction temperature is 60° C. and the reaction time is 4 h, and the rest of the processes are the same as those in Example 1.

[0161] Embodiment 30

[0162] The method for preparing cotton cellulose provided in the embodiment of the present application is the same as that in Example 1, except that the hydrothermal reaction temperature is 60° C. and the reaction time is 8 h, and the rest of the processes are the same as those in Example 1.

[0163] Embodiment 31

[0164] The method for preparing cotton cellulose provided in the embodiment of the present application is the same as that in Example 1, except that the hydrothermal reaction temperature is 60° C. and the reaction time is 12 h, and the rest of the processes are the same as those in Example 1.

[0165] Embodiment 32

[0166] The method for preparing cotton cellulose provided in the embodiment of the present application is the same as that in Example 1, except that the hydrothermal reaction temperature is 20° C. and the reaction time is 1 h, and the rest of the processes are the same as those in Example 1.

[0167] Embodiment 33

[0168] The method for preparing cotton cellulose provided in the embodiment of the present application is the same as that in Example 1, except that the hydrothermal reaction temperature is 30° C. and the reaction time is 1 h, and the rest of the processes are the same as those in Example 1.

[0169] Embodiment 34

[0170] The method for preparing cotton cellulose provided in the embodiment of the present application is the same as that in Example 1, except that the hydrothermal reaction temperature is 40° C. and the reaction time is 1 h, and the rest of the processes are the same as those in Example 1.

[0171] Embodiment 35

[0172] The method for preparing cotton cellulose provided in the embodiment of the present application is the same as that in Example 1, except that the hydrothermal reaction temperature is 50° C. and the reaction time is 1 h, and the rest of the processes are the same as those in Example 1.

[0173] Embodiment 36

[0174] The method for preparing cotton cellulose provided in the embodiment of the present application is the same as that in Example 1, except that the hydrothermal reaction temperature is 80° C. and the reaction time is 1 h, and the rest of the processes are the same as those in Example 1.

[0175] Embodiment 37

[0176] The method for preparing cotton cellulose provided in the embodiment of the present application is the same as that in Example 1, except that the hydrothermal reaction temperature is 100° C. and the reaction time is 1 h, and the rest of the processes are the same as those in Example 1.

[0177] Performance Testing

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

[0179] Among them, the degree of polymerization is determined as follows:

[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 of pulp”.

[0181]

[0182] DP 0.905 =0.75[η];

[0183] Wherein: ηr is the relative viscosity (mL / g); η0 is the viscosity of copper ethylenediamine (CED) (mL / g); η is the characteristic 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 0.002g / mL; DP is the average degree of polymerization of the sample.

[0184] Crystallinity determination:

[0185] The spectrum was obtained by X-ray diffraction (XRD), and the XRD spectrum was analyzed by MDI Jade6.0. The crystallinity index (CrI) can be calculated by comparing the minimum intensity before the maximum diffraction peak with the height of the main diffraction peak. For cellulose, it is 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 of cotton cellulose in Examples 1 to 26 and Comparative Examples 1 to 3

[0187]

[0188]

[0189] As can be seen from Table 1, the crystallinity of the raw cotton (i.e., comparative example 3) is 71.1%, and the degree of polymerization is 3512. The degree of damage of acidic DES to cotton cellulose is greater than that of neutral DES. When choline chloride and betaine are used as HBA, the crystallinity and degree of polymerization of cotton fiber decrease more than when HBD is an organic acid than when HBD is a polyol. The more carboxyl groups or hydroxyl groups there are in HBD, the more obvious the decrease in crystallinity and degree of polymerization of cotton fiber. The stronger the acidity of DES, the more serious the damage to the hydrogen bonds of the cellulose molecular chain. When HBD is the same, betaine is better than choline chloride in treating cotton fiber. Metal ion DES is more serious in damaging cotton fiber. Hydrophilic DES has different degrees of damage to the crystallinity and degree of polymerization of cotton fiber. For example, after the hydrophilic coumarin-cyclohexanol treatment, the crystallinity of cotton fiber decreases by 18% and the degree of polymerization decreases by about one thousand, while the crystallinity and degree of polymerization of cotton after the hydrophobic coumarin-n-octadecyl mercaptan DES and coumarin-octanol DES treatment do not change significantly. 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, in Example 1 and Examples 27 to 37, the hydrothermal reaction temperature and time were optimized to obtain cotton cellulose with different crystallinity and polymerization degree. The results are shown in Table 2.

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

[0192]

[0193] As can be seen from Table 2, with the increase of temperature and the extension of treatment time, the polymerization degree and crystallinity of cotton fiber gradually decrease. This is because the increase of temperature or the extension of reaction time accelerates the movement rate of solvent molecules, strengthens the hydrogen bond interaction between cellulose and solvent, and destroys the hydrogen bond network within and between cellulose molecules to a greater extent. By optimizing the solvent type and process conditions, cotton cellulose products with specific polymerization degree and crystallinity can be prepared.

[0194] Figures 1-2 They are scanning electron microscope images and FI-IR images of the waste cotton fabric in Example 1 of the present invention, the cotton staple fibers after mechanical crushing, and the cotton fibers after DES treatment.

[0195] Figures 1-2 Cotton means waste cotton fabric, Cut-Cotton means cotton staple fiber after step S1 of Example 1, and DES-Cotton means cotton cellulose finally obtained after DES treatment with citric acid-glycerol-water in step S3 of Example 1.

[0196] from Figures 1-2 It can be seen that the size of the cotton staple fibers after cutting becomes significantly shorter, and there is a small amount of agglomeration during the cutting process. After DES treatment, the fiber curl is expanded, and the fiber surface is damaged to a certain extent. Infrared shows that the chemical structure of the fiber is not damaged. The main characteristic peaks of cotton cellulose after DES treatment do not change and remain 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 treatment with different DES.

[0199] Figures 3-4 Medium cotton represents waste cotton fabric that has not been treated in any way, citric acid-glycerol represents the cotton cellulose prepared in Example 1, caffeic acid-glycerol represents the cotton cellulose prepared in Example 7, choline chloride-glycerol represents the cotton cellulose prepared in Example 11, betaine-glycerol represents the cotton cellulose prepared in Example 17, and potassium carbonate-glycerol represents the cotton cellulose prepared in Example 23.

[0200] from Figures 3-4 It can be seen that the cotton cellulose samples all show several typical cellulose characteristic peaks, namely 3317cm -1 (-OH), 2920cm -1 (CH) and 1051cm-1 (CO). The results showed that the DES treatment process occurred under relatively mild conditions, retaining the most characteristic functional groups of raw 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 raw cotton fibers and DES-treated samples. The CrI values ​​calculated from the diffraction patterns showed that all DES treatments destroyed the crystalline regions of cellulose to some extent, promoted hydrogen bonds or chemical interactions between solvent molecules and cellulose, and resulted 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 in the protection scope of the present invention.

Claims

1. A method for preparing cotton cellulose, characterized in that: The following steps are involved: After the waste cotton fabric is shredded, cotton staple fibers are obtained; The hydrogen bond acceptor and the hydrogen bond donor are heated and dissolved to obtain a deep eutectic solvent; The cotton staple fibers and the low eutectic solvent are mixed and subjected to a hydrothermal reaction, and the solid phase is separated and dried to obtain cotton cellulose.

2. The method for preparing cotton cellulose according to claim 1, characterized in that: The hydrogen bond acceptor is citric acid, and the hydrogen bond donor includes a mixture of any one of glycerol, ethylene glycol, glycine, alanine, L-cysteine, arginine and water; Or, the hydrogen bond acceptor is caffeic acid, and the hydrogen bond donor includes a mixture of any one of glycerol, ethylene glycol, octanol and water; Or, the hydrogen bond acceptor is choline chloride, and the hydrogen bond donor includes a mixture of any one of urea, glycerol, lactic acid, malonic acid, malic acid, citric acid and water; Or, the hydrogen bond acceptor is betaine, and the hydrogen bond donor includes a mixture of any one of urea, glycerol, lactic acid, malonic acid, citric acid, glucose and water; Or, the hydrogen bond acceptor is zinc chloride, and the hydrogen bond donor comprises a mixture of glycerol and water; Or, the hydrogen bond acceptor is potassium carbonate, and the hydrogen bond donor includes a mixture of glycerol and water; Or, the hydrogen bond acceptor is DBU, and the hydrogen bond donor comprises a mixture of glycerol and water; Or, the hydrogen bond acceptor is DBN, and the hydrogen bond donor comprises a mixture of glycerol and water; Alternatively, the hydrogen bond acceptor is coumarin, and the hydrogen bond donor comprises a mixture of cyclohexanol and water.

3. The method for preparing cotton cellulose according to claim 2, characterized in that: When the hydrogen bond acceptor is citric acid and the hydrogen bond donor includes a mixture of any one of glycerol, ethylene glycol, glycine, alanine, L-cysteine, arginine and water, the molar ratio of the citric acid to any one of glycerol, ethylene glycol, glycine, alanine, L-cysteine, arginine and water is (1-2):(1-2):(1-4); When the hydrogen bond acceptor is caffeic acid and the hydrogen bond donor includes a mixture of any one of glycerol, ethylene glycol, octanol and water, the molar ratio of the caffeic acid to any one of glycerol, ethylene glycol, octanol and water is (1-2):(1-2):(1-4); When the hydrogen bond acceptor is choline chloride and the hydrogen bond donor includes a mixture of 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); When the hydrogen bond acceptor is betaine and the hydrogen bond donor includes a mixture of any one of urea, glycerol, lactic acid, malonic acid, citric acid, glucose and water, the molar ratio of the betaine to any one of urea, glycerol, lactic acid, malonic acid, citric acid, glucose and water is (1-2):(1-2):(1-4); 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); 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); 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); 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); 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).

4. The method for preparing cotton cellulose according to claim 1, characterized in that: In the step of mixing the cotton staple fibers and the low eutectic solvent and then subjecting them to a hydrothermal reaction, the hydrothermal reaction temperature is 30 to 90° C. and the reaction time is 1 to 12 hours.

5. The method for preparing cotton cellulose according to claim 1, characterized in that: In the step of mixing the cotton staple fibers and the low eutectic solvent and then subjecting them to a hydrothermal reaction, the mass ratio of the cotton staple fibers to the low eutectic solvent is 1:(5-30).

6. The method for preparing cotton cellulose according to claim 1, characterized in that: The cotton staple fibers and the low eutectic solvent are mixed and subjected to a hydrothermal reaction, and a reaction solution is obtained after the hydrothermal reaction is completed; adding a mixed solvent of ethanol and water to the reaction solution, stirring, separating the solid and the liquid, collecting the solid phase, washing, and drying to obtain cotton cellulose; The volume ratio of the mixed solvent of ethanol and water to the reaction solution is (0.5-3):1; The volume ratio of ethanol to water in the mixed solvent of ethanol and water is (7-9):(1-3).

7. The method for preparing cotton cellulose according to claim 6, characterized in that: Adding a mixed solvent of ethanol and water to the reaction solution, stirring, separating the solid and the liquid, collecting the solid phase and the liquid phase, rotary evaporating the liquid phase, and drying to obtain a low eutectic solvent; The washing is specifically as follows: the solid phase is first washed with an ethanol-water mixture and then washed with water until it becomes neutral, wherein the volume ratio of ethanol to water in the ethanol-water mixture is (7-9):(1-3).

8. The method for preparing cotton cellulose according to claim 1, characterized in that: The waste cotton fabric is placed in a shearing shredder and shredded at 1500-2000 r / min to obtain cotton staple fibers; The cotton staple fibers have a diameter of 10 to 20 μm and a length of 100 to 250 μm; The waste cotton fabric includes at least one of denim, plain cloth, corduroy and varnish.

9. A cotton cellulose, characterized in that The preparation is obtained by the preparation method according to any one of claims 1 to 8.

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