Efficient, energy-saving and environment-friendly fabric dissolving method

Abstract

The invention discloses an efficient, energy-saving and environment-friendly fabric dissolving method, and belongs to the technical field of textile recycling treatment. The method comprises the following steps: uniformly mixing choline chloride and oxalic acid in proportion, stirring at a certain temperature, and melting to obtain DES; the method comprises the following steps: drying a fabric, cutting the fabric into small blocks of 1 cm * 1 cm, and crushing the small blocks for multiple times by a high-speed crusher to obtain short fibers with the length of not more than 3 mm; placing the crushed fabric in a mixed solvent of ionic liquid and DES, dissolving at a certain temperature, centrifuging, washing with water, and drying to obtain fiber powder; the ionic liquid and DES composite solvent is used for dissolving the cotton fibers, the dissolving temperature is low, the dosage of the ionic liquid is small, and the dissolving time is short. Efficient and environment-friendly dissolution treatment of cotton fibers is realized, and a new method is provided for dissolution of cotton fabrics.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of textile recycling, and particularly relates to a high-efficiency, energy-saving and environmentally-friendly fabric dissolving method, which is especially suitable for the dissolution and regeneration of waste colored cotton fabric. BACKGROUND

[0002] In the production and use of textiles, a large amount of printing and dyeing defects, waste fibers and waste fabrics are generated, among which the proportion of waste cotton textiles is the highest. At present, the treatment of waste textiles is still mainly based on traditional chemical incineration or physical landfill, which not only pollutes the environment, but also wastes resources. Recycling and utilizing waste textiles can not only reduce environmental pollution, but also supplement textile raw materials, which has significant environmental and economic benefits.

[0003] After cotton textiles are dyed, a large number of dye molecules are fixed on the fibers, which makes the recycling and reuse of the textiles face a key bottleneck: traditional physical recycling (such as opening, spinning again) has low product value due to the damage to fiber length and strength and color mixing; and chemical recycling (i.e. dissolution-regeneration route) must first face the problem of dye removal. At present, the treatment of printed and dyed cotton textiles usually needs to be subjected to a decolorization treatment with strong chemical reagents (such as strong alkali, strong oxidizing / reducing agents). This pretreatment step not only has a complex process, high energy consumption and easy secondary pollution, but more importantly, the severe chemical environment will inevitably cause hydrolysis or oxidative degradation of the cellulose molecular chain, resulting in a decrease in the degree of polymerization of the regenerated cellulose and a broadening of the molecular weight distribution, which eventually seriously damages the mechanical properties and application value of the regenerated cellulose. In other words, in the prior art, there is an irreconcilable contradiction between “decolorization” and “protection of the inherent properties of the fiber”.

[0004] In order to bypass the limitations of traditional aqueous systems, researchers have developed a variety of non-aqueous solvent systems for directly dissolving cellulose, such as ionic liquids, N-methylmorpholine-N-oxide (NMMO) and certain inorganic salt molten hydrates. These solvents exhibit good solubility for pure cotton cellulose. However, when treating waste printed and dyed cotton textiles, their effectiveness is often greatly reduced. Dye molecules are usually tightly bound to cellulose through hydrogen bonds, van der Waals forces or even covalent bonds, forming a more stable composite system. Most existing single solvent systems cannot effectively destroy the combination between “dye-cellulose” and the dense crystalline region of cellulose (especially the cellulose type I crystalline structure), resulting in low and incomplete dissolution efficiency of printed and dyed cotton. Even if partial dissolution is achieved, the resulting solution has poor uniformity, and the regenerated cellulose material often contains a large amount of dye aggregates or cellulose microcrystals that are not completely dissociated, which has a large particle size, a wide distribution, a non-thoroughly destroyed crystalline structure, and seriously affects the subsequent processing performance and product quality.

[0005] The waste and old textile can be prepared into cellulose powder after recycling and applied in the field of pigment printing. In the application field of pigment printing, the particle size and dispersibility of the regenerated cellulose material have clear and strict requirements. The ideal pigment printing paste requires cellulose particles to have nanoscale size (usually 100-450 nm), uniform distribution and stable structure, so as to ensure that the fabric surface after printing is smooth, the color is uniform, the hand feeling is soft and good fastness is obtained. However, the existing dissolution technology is difficult to realize efficient and mild dissolution of the printing and dyeing cotton textile, and it is more difficult to directly obtain the nanocellulose powder with controllable particle size and complete structure which meets the application requirements of pigment printing. Therefore, developing a dissolution method which can efficiently and completely dissolve the printing and dyeing cotton textile and directly obtain superfine cellulose powder suitable for pigment printing application has become a technical problem to be solved in this field. SUMMARY

[0006] In view of the above technical problems, the purpose of the present application is to provide a dissolution method of printing and dyeing cotton textile, so as to solve the problems of existing methods, such as complex process, high energy consumption, high cost, poor dissolution effect of single solvent, and large particle size and wide distribution of recycled cellulose powder.

[0007] In order to achieve the above purpose, the present application first provides a fabric dissolution method with simple process, high dissolution efficiency and good environmental protection. The method uses an ionic liquid and a deep eutectic solvent (DES) composite system to realize efficient dissolution of the fabric.

[0008] A high-efficiency, energy-saving and environmentally friendly fabric dissolution method comprises the following steps: (1) DES preparation: mix a hydrogen bond acceptor and a hydrogen bond donor, stir uniformly, and obtain a DES solution; (2) crushing treatment: dry the fabric, cut it into small pieces, and pass through a high-speed pulverizer for multiple crushing to obtain short fibers with a length of not more than 3 mm; (3) preparation of treatment solvent: mix the imidazole ionic liquid and the DES solution obtained in step (1) at 80℃ for 5-10 min, mix uniformly, and obtain a composite solvent; (4) fabric dissolution: place the crushed fabric in step (2) in the composite solvent in step (3), dissolve, centrifuge, wash with water, dry, and obtain a fiber powder.

[0009] In an embodiment of the present application, the hydrogen bond acceptor in step (1) includes at least one of choline chloride, choline bromide, choline acetate and other quaternary ammonium salts, and the hydrogen bond donor is oxalic acid.

[0010] In an embodiment of the present application, the molar ratio of the hydrogen bond acceptor and the hydrogen bond donor in step (1) is 1:2, the mixing temperature is 80℃, and the stirring time is 4h.

[0011] In an embodiment of the present application, the fabric in step (2) comprises cotton fabric, hemp fabric, wool fabric, synthetic fiber fabric.

[0012] In an embodiment of the present application, the fabric in step (2) is preferably printed and dyed fabric.

[0013] In an embodiment of the present application, the imidazole ionic liquid in step (3) comprises one or more of 1-butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, 1-allyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium acetate.

[0014] In an embodiment of the present application, the mass ratio of the imidazole ionic liquid to the DES solution in step (3) is 1:9 to 5:5, further preferably 1:9 to 3:7, and more preferably 1:9 to 2:8.

[0015] In an embodiment of the present application, the mass ratio of the crushed fabric to the composite solvent in step (4) is 1% to 4%.

[0016] In an embodiment of the present application, the dissolution temperature in step (4) is 65 to 85°C, further preferably 75 to 85°C, and the dissolution time is 30 to 90 min, further preferably 50 to 60 min.

[0017] In an embodiment of the present application, the drying in step (4) is drying at 50°C for 24 h.

[0018] The present application also provides a cellulose powder obtained by the above method.

[0019] The present application also provides the use of the above cellulose powder in pigment printing.

[0020] Advantages: 1. The present application selects imidazole ionic liquid and DES to form a composite solvent system, which can directly dissolve fabric, especially printed and dyed fabric, and the fabric dissolution effect is good. The printed and dyed fabric does not need to be pretreated by bleaching, which greatly saves the process flow. After dissolution and drying, cellulose I type powder with small particle size and narrow distribution can be prepared, and the recycling rate of waste fabric is improved.

[0021] 2. The present application selects the DES system of oxalic acid and choline chloride and imidazole ionic liquid for compounding. This system optimizes the physicochemical properties of the solvent, reduces the viscosity of the system, is convenient to operate, and can significantly improve the dissolution effect of the fabric at a specific ratio.

[0022] 3、The process flow of the application is simple, and can be operated continuously, and is suitable for the treatment of large quantities of printing and dyeing defective products and colored waste fabrics; in addition, the application has mild dissolution conditions, short time, low temperature and small energy consumption; no harmful substances are produced, and it is environmentally friendly.

[0023] 4、The method of the application has good dissolution effect on cotton fabrics and printed and dyed cotton fabrics, and the cellulose powder obtained after dissolution presents a typical cellulose I type structure, and the average particle size of the cellulose powder is below 430 nm, and the particle size distribution is relatively uniform, and can be better applied to coating printing. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The particle size distribution diagram of the cellulose powder after the fabric in Example 1 of the application is dissolved; Figure 2 The XRD diagram of the cellulose powder after the fabric in Example 1 of the application is dissolved; Figure 3 The particle size distribution diagram of the cellulose powder after the fabric in Example 2 of the application is dissolved; Figure 4 The XRD diagram of the cellulose powder after the fabric in Example 2 of the application is dissolved; Figure 5 The particle size distribution diagram of the cellulose powder after the fabric in Comparative Example 1 of the application is dissolved; Figure 6 The XRD diagram of the cellulose powder after the fabric in Comparative Example 1 of the application is dissolved; Figure 7 The particle size distribution diagram of the cellulose powder after the fabric in Comparative Example 3 of the application is dissolved; Figure 8 The XRD diagram of the cellulose powder after the fabric in Comparative Example 3 of the application is dissolved.

[0025] Figure 9 The particle size distribution diagram of the cellulose powder after the fabric in Comparative Example 4 of the application is dissolved; Figure 10 The XRD diagram of the cellulose powder after the fabric in Comparative Example 4 of the application is dissolved; DETAILED DESCRIPTION The application will be further described below in conjunction with specific examples, but the protection scope of the application is not limited thereto.

[0026] Example 1 The object treated in this example is bleached pure cotton fabric, and the steps are as follows: The 1-butyl-3-methylimidazolium chloride salt was mixed with the DES prepared by mixing choline chloride and oxalic acid at a molar ratio of 1:2 at 80°C under stirring for 4h, and then mixed at a mass ratio of 1:9 to prepare 19.6g of a composite solvent. After uniform mixing, 0.4g of a pure cotton fabric was weighed and put into the solvent, and then dissolved in a constant temperature heating jacket at 80°C for 60min. After taking out, deionized water was added and centrifuged, and the step was repeated three times to remove the solvent. After drying at 50°C for 24h, a fiber powder was obtained.

[0027] Figure 1 and Figure 2 The indexes of the pure cotton fabric after dissolution were determined. Figure 1 and Figure 2 It can be seen that the obtained cellulose powder has a particle size of about 310nm, the XRD spectrum shows that it is a typical cellulose I crystal structure, and the crystallinity is 80%. The crystallinity of the original cloth is about 85%, indicating that the dissolution effect on the amorphous region is good.

[0028] Example 2 The treatment object of this example is an active blue KN-R dyed cotton fabric, and the steps are the same as those in Example 1.

[0029] Figure 3 and Figure 4 The indexes of the active blue KN-R dyed cotton fabric after dissolution were determined. Figure 3 and Figure 4 It can be seen that the obtained cellulose powder has a particle size of about 430nm, the XRD spectrum shows that it is a cellulose I crystal structure, and the crystallinity is about 65%. The crystallinity of the original cloth is about 75%, and the crystallinity decreases significantly, indicating that the dissolution effect on the amorphous region is good.

[0030] Comparative Example 1 The treatment object of this example is an active blue KN-R dyed cotton fabric, and the steps are the same as those in Example 1.

[0031] The parameters of the cotton fiber powder dissolved by only DES were compared with those of Example 2, and the results are shown in Figure 5 and Figure 6 .

[0032] It can be seen from Figure 5 and Figure 6 that the particle size of the fiber powder obtained in Comparative Example 1 is about 537nm, which is larger than that of the cellulose powder obtained in the present application, and the crystallinity of the fiber powder is about 72%, which only decreases by 3%, indicating that the dissolution effect of the dyed cotton fabric using only DES as the solvent is poor.

[0033] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that only an ionic liquid is used to dissolve the fabric.

[0034] The cotton fabric only treated by the ionic liquid solution process is difficult to regenerate cellulose powder due to a large viscosity.

[0035] Comparative Example 3 The treatment object of the present comparative example is the cotton fabric dyed with reactive blue KN-R, the solvent is a composite system of ionic liquid and DES with a mass ratio of 2:8, and the treatment conditions are the same as those in Example 1.

[0036] The powder index of the fiber obtained in the present comparative example is compared with that in Example 1, and the results are shown in Figure 7 and Figure 8 .

[0037] As can be seen from Figure 7 and Figure 8 , the particle size of the cellulose powder obtained in Comparative Example 2 is about 709 nm, which is larger than that of the cellulose powder obtained in the present application, and the crystallinity of the fiber powder is about 70%, which is not significantly decreased, indicating that ionic liquid and DES can only obtain a better dissolution effect at a specific composite ratio.

[0038] Comparative Example 4 The difference between Comparative Example 4 and Example 2 is that the molar ratio of the hydrogen bond acceptor and the hydrogen bond donor in DES is 1:1.

[0039] As can be seen from Figure 9 and Figure 10 , the particle size of the cellulose powder obtained in Comparative Example 4 is about 1050 nm, which is larger than that of the cellulose powder obtained in the present application, the XRD pattern shows that it is still a cellulose I crystal structure, and the crystallinity is about 72%, and the crystallinity of the original cloth is about 75%, indicating that the composition ratio of DES plays an important role in the dissolution of cellulose.

[0040] Comparative Example 5 The difference between Comparative Example 5 and Example 2 is that the type of DES is different, the hydrogen bond acceptor is choline chloride, the hydrogen bond donor is acetic acid, and the molar ratio of the two is 1:2.

[0041] The composite solvent of the comparative example is difficult to dissolve the cotton fabric, indicating that the type of DES plays a decisive role in the dissolution of cellulose.

[0042] In summary, the ionic liquid and DES are used for dissolving the cotton fabric in the present application, which has the advantages of high dissolution efficiency, simple process, environmental protection and energy saving, and is suitable for the resource recycling of various waste fabrics.

[0043] The examples provided above are not intended to limit the scope covered by the present application, and the described steps are not intended to limit the execution order. Those skilled in the art can make obvious improvements to the present application in combination with existing common knowledge, which also falls within the protection scope defined by the claims of the present application.

Claims

1. A highly efficient, energy-saving, and environmentally friendly method for dissolving fabrics, characterized in that, Includes the following steps: (1) DES preparation: Mix the hydrogen bond acceptor and the hydrogen bond donor, stir evenly to obtain a DES solution, wherein the hydrogen bond acceptor includes at least one of choline chloride, choline bromide, and acetylcholine, and the hydrogen bond donor is oxalic acid; (2) Crushing treatment: After the fabric is dried, it is cut into small pieces and crushed multiple times by a high-speed crusher to obtain short fibers with a length not exceeding 3mm; (3) Preparation of processing solvent: The imidazole ionic liquid and the DES solution obtained in step (1) are stirred at 80°C for 5-10 min and mixed evenly to obtain a composite solvent; (4) Fabric dissolution: The pulverized fabric in step (2) is placed in the composite solvent in step (3), dissolved, centrifuged, washed with water, and dried to obtain fiber powder.

2. The fabric dissolving method according to claim 1, characterized in that, The molar ratio of hydrogen bond acceptor to hydrogen bond donor in step (1) is 1:2, the mixing temperature is 80℃, and the stirring time is 4h.

3. The fabric dissolving method according to claim 1, characterized in that, The fabric mentioned in step (2) includes any one of cotton fabric, linen fabric, wool fabric, synthetic fiber fabric, and printed and dyed fabric.

4. The fabric dissolving method according to claim 1, characterized in that, The imidazole ionic liquids mentioned in step (3) include one or more of 1-butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, 1-allyl-3-methylimidazolium chloride, and 1-butyl-3-methylimidazolium acetate.

5. The fabric dissolving method according to claim 1, characterized in that, The mass ratio of the imidazole ionic liquid to the DES solution in step (3) is 1:9 to 5:

5.

6. The fabric dissolving method according to claim 1, characterized in that, The mass ratio of the pulverized fabric to the composite solvent in step (4) is 1-4%.

7. The fabric dissolving method according to claim 1, characterized in that, The dissolution temperature in step (4) is 65~85℃ and the dissolution time is 30~90min.

8. The fabric dissolving method according to claim 1, characterized in that, The drying mentioned in step (4) refers to drying at 50°C for 24 hours.

9. Cellulose powder obtained by dissolving according to any one of claims 1 to 8.

10. The use of the cellulose powder of claim 9 in coating printing.

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