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

Abstract

The invention discloses an efficient, energy-saving and environment-friendly fabric stripping method, and belongs to the field of textile treatment. The method comprises the following steps: (1) thiourea dioxide reduction treatment: putting a fabric into a stripping solution containing thiourea dioxide and NaOH, dipping and stripping at a certain temperature, taking out after a certain time, and washing with water to obtain a reduced and stripped cotton fabric; and (2) sodium persulfate oxidation treatment: putting the fabric subjected to reduction treatment in the step (1) into a stripping solution containing Na2S2O8 and NaOH, carrying out second-step oxidation stripping at a certain temperature, taking out the fabric again after a certain time, washing with water, and drying to obtain the stripped fabric. The reducibility of thiourea dioxide and the oxidability of sodium persulfate are synergistically utilized in the stripping process, the stripping rate of the cotton fabric is increased, the stripping temperature is low, the dosage of the stripping agent is small, and the stripping time is short. The combination of high efficiency and environmental protection is realized, and a new method is provided for stripping the cotton fabric.

Description

Technical Field

[0001] The present invention belongs to the field of textile treatment, and particularly relates to an efficient, energy-saving and environmental-friendly fabric stripping method. Background Art

[0002] In the production, processing and use of textiles, a large number of printed and dyed defective products, waste fibers and waste fabrics are generated, among which waste cotton textiles account for the largest proportion. At present, the treatment of waste textiles still adopts traditional chemical incineration or physical landfill methods. This treatment method not only pollutes the atmospheric environment and land, but also causes great waste of textile resources. Recycling waste textiles can not only reduce the pollution to land and atmosphere caused by landfill or incineration, but also supplement the raw material supply of the textile industry secondly, which has important environmental and economic significance.

[0003] After cotton textiles go through the dyeing process, a large number of chemical dye molecules will be fixed on the cotton fibers. The existence of these chemical substances seriously affects the next-step processing of recycled textiles. Therefore, before recycling waste textiles, it is necessary to first perform a stripping treatment to strip off the dye molecules fixed on the fibers. For colored cotton textiles, generally the oxidation method or the reduction method is used for stripping. The oxidizing or reducing property of chemical reagents is used to destroy the chromophore groups in the dye molecular structure and the bonding between the dye and the fiber, so as to achieve the purpose of stripping. In actual production, common reducing agents for stripping include sodium hydrosulfite, sodium formaldehyde sulfoxylate, etc., and common oxidizing agents for stripping include sodium hypochlorite, hydrogen peroxide, etc. Sodium hydrosulfite is not easy to store, decomposes relatively fast under humid and hot conditions, has a low effective utilization rate, is easy to spontaneously combust, and has a fire hazard; when sodium formaldehyde sulfoxylate decomposes, it will generate harmful gases such as hydrogen sulfide, formaldehyde, sulfur dioxide, etc., which are highly harmful to the environment and human body. As a strong oxidizing agent, sodium hypochlorite has strong oxidizing property, but it may generate toxic and harmful substances such as chlorine gas and chloroform during the stripping process, which is highly harmful to the human body. Compared with sodium hypochlorite, hydrogen peroxide is non-toxic to the human body and almost pollution-free to the environment during use, but its stability is poor, and it is easily decomposed by factors such as heat, light and metal, resulting in a reduced effective utilization rate. At the same time, hydrogen peroxide usually requires a relatively high temperature during use, resulting in high energy consumption. In addition, it is often difficult to completely strip off the dye molecules fixed on the fibers by using the reduction method or the oxidation method alone. The color phase of some dye-dyed fabrics will change after stripping, showing a semi-stripping phenomenon. Therefore, seeking a new type of efficient, energy-saving and environmental-friendly fabric stripping method is of great significance for the recycling of waste cotton fabrics and environmental protection. Summary of the Invention

[0004] [Technical Problem]

[0005] There are several defects in the stripping operation of textiles: hazardous substances such as formaldehyde sodium bisulfite and sodium hypochlorite are generated during use; the reagents are not stable enough, and their utilization rate decreases significantly after a long storage time; the treatment process consumes a large amount of energy and takes a long time; the effect of dye removal is not thorough enough, and there is still a background color left, which is not conducive to subsequent reuse.

[0006] [Technical content]

[0007] The purpose of the present invention is to overcome the disadvantages of the existing traditional stripping process, such as complex process, long stripping time, high stripping temperature, and low environmental protection index of the stripping process, and provide a new type of high-efficiency and environmentally friendly stripping treatment method. As a substitute for sodium dithionite, thiourea dioxide has the characteristics of high reduction potential, pollution-free reaction products, convenient transportation and storage; sodium persulfate also has the advantages of low cost, good water solubility, and environmental friendliness. Based on the problems that occur in the above-mentioned stripping process, the present invention uses a thiourea dioxide-sodium persulfate synergistic system to strip reactive dye-stained cotton fabrics. The present invention is of great significance for improving the recycling value of waste cotton fabrics and expanding the research scope of cotton textiles in the field of stripping.

[0008] In order to achieve the above object, the technical solution provided by the present invention is as follows:

[0009] A fabric stripping method with high efficiency, energy conservation and environmental protection, comprising the following steps:

[0010] (1) Thiourea dioxide reduction treatment: Put the fabric into a stripping solution containing thiourea dioxide and NaOH, carry out impregnation stripping at a certain temperature, take it out after a certain time, wash it with water, and obtain a reduced-stripped cotton fabric;

[0011] (2) Sodium persulfate oxidation treatment: Put the fabric after the reduction treatment in step (1) into a stripping solution containing Na2S2O8 and NaOH, carry out the second oxidation stripping at a certain temperature, take it out again after a certain time, wash it with water and then dry it to obtain a stripped fabric.

[0012] Further, the fabric in step (1) includes cotton fabrics, wool fabrics, silk fabrics, and fabrics made of hydrophilic fibers.

[0013] Further, the composition of the stripping solution in step (1) is: the concentration of thiourea dioxide is 2-8 g / L, the concentration of sodium hydroxide is 4-8 g / L, and the concentration of Peregal O is 0.1-0.2 g / L.

[0014] Preferably, the composition of the stripping solution in step (1) is: the concentration of thiourea dioxide is 2-4 g / L, the concentration of sodium hydroxide is 4-8 g / L, and the concentration of Peregal O is 0.1-0.2 g / L.

[0015] Further, in step (1), the stripping temperature is 50 - 60°C, and the stripping time is 20 - 25 min.

[0016] Further, in step (2), the composition of the stripping solution is as follows: the concentration of sodium persulfate is 6 - 12 g / L, the concentration of sodium hydroxide is 4 - 8 g / L, and the concentration of Peregal O is 0.1 - 0.2 g / L.

[0017] Preferably, in step (2), the composition of the stripping solution is as follows: the concentration of sodium persulfate is 6 - 8 g / L, the concentration of sodium hydroxide is 4 - 8 g / L, and the concentration of Peregal O is 0.1 - 0.2 g / L.

[0018] Further, in step (2), the stripping temperature is 50 - 60°C, and the stripping time is 20 - 25 min.

[0019] A method for improving the whiteness of the fabric after stripping, comprising the following steps:

[0020] S1. Thiourea dioxide reduction treatment: Put the fabric into a stripping solution containing thiourea dioxide and NaOH, carry out impregnation stripping at a certain temperature, take it out after a certain time, wash with water, and obtain a reduced and stripped cotton fabric;

[0021] S2. Sodium persulfate oxidation treatment: Put the fabric after the reduction treatment in step S1 into a stripping solution containing Na2S2O8 and NaOH, carry out the second oxidation stripping at a certain temperature, take it out again after a certain time, wash with water and then dry, and obtain a stripped fabric.

[0022] In an embodiment of the present invention, the fabric in step S1 includes cotton fabric, wool fabric, silk fabric, and fabric made of hydrophilic fibers.

[0023] In an embodiment of the present invention, the composition of the stripping solution in step S1 is as follows: the concentration of thiourea dioxide is 2 - 8 g / L, the concentration of sodium hydroxide is 4 - 8 g / L, and the concentration of Peregal O is 0.1 - 0.2 g / L.

[0024] In an embodiment of the present invention, in step S1, the stripping temperature is 50 - 60°C, and the stripping time is 20 - 25 min.

[0025] In an embodiment of the present invention, the composition of the stripping solution in step S2 is as follows: the concentration of sodium persulfate is 6 - 12 g / L, the concentration of sodium hydroxide is 4 - 8 g / L, and the concentration of Peregal O is 0.1 - 0.2 g / L.

[0026] In an embodiment of the present invention, in step S2, the stripping temperature is 50 - 60°C, and the stripping time is 20 - 25 min.

[0027] The reaction principle of the present invention is as follows:

[0028] The present invention uses a synergistic system of thiourea dioxide reduction and sodium persulfate oxidation to strip the color of colored cotton fabrics. Thiourea dioxide can decompose into two substances, hyposulfurous acid and urea, under alkaline and heating conditions. Hyposulfurous acid is a highly reactive reducing agent that will continue to decompose to produce nascent reducing hydrogen, which can reduce and degrade the chromogenic groups of dyes.

[0029] Based on the first-step reduction treatment with thiourea dioxide, the present invention uses sodium persulfate for the second-step oxidation treatment. Sodium persulfate is an oxidizing agent that can decompose to produce sulfate radicals with strong oxidizing properties under high temperature and alkaline conditions. The sulfate radicals can react with hydroxides and water in the solution to produce hydroxyl radicals with the same strong oxidizing properties, which can decompose the chromogenic groups of dyes on the fabric, such as azo groups, oxidize amino groups, and methylate carboxyl groups to achieve the stripping of the fiber.

[0030] [Beneficial effects]

[0031] 1. After stripping the color of the dyed cotton fabric, the present invention has a high stripping rate and a high whiteness of the fabric after stripping.

[0032] 2. The present invention causes little damage to the fabric during the stripping process, has a high strength retention rate, and does not affect the service performance of the fabric after stripping.

[0033] 3. The process flow of the present invention is simple, can be operated continuously, and can strip the color of printing and dyeing defective products and colored waste cotton fabrics in large quantities and efficiently.

[0034] 4. The process conditions of the present invention are mild, the stripping time is short, the stripping temperature is low, and the energy consumption is small; and no harmful substances and irritating gases are generated during the stripping process, which is environmentally friendly. Specific embodiments

[0035] The following further describes the present invention in detail with specific embodiments.

[0036] Test methods for the indicators in the present invention:

[0037] (1) Stripping rate: Under the conditions of D 65 light source and a 10° field of view, stack the test fabric into 4 layers, use a Datacolor colorimeter to measure the K / S value of the fabric, take any five points to measure their K / S values, and calculate their arithmetic mean.

[0038] (2) Strong retention rate: According to GB / T 3923.1-2013 "Textiles - Tensile properties of fabrics - Part 1: Determination of maximum force and elongation at maximum force (strip method)", the fabric was cut into a specification of 5 cm × 30 cm, and a YG(B)026H-250 type electronic fabric strength tester was used to test the breaking strength of the cotton fabric before and after stripping. Each sample was measured 3 times, and the average value was calculated.

[0039] (3) Whiteness: According to the GB / T 17644-2008 standard, a WSD-3C intelligent digital whiteness meter was used to measure the whiteness of the samples. Each sample was measured 3 times, and the average value was calculated.

[0040] Example 1

[0041] The object to be treated in this example is the cotton fabric dyed with anthraquinone reactive dye Reactive Blue KN-R, and the following steps are used for stripping:

[0042] Step (1): Reduction treatment with thiourea dioxide;

[0043] Weigh 5 g of the dyed cotton fabric, prepare the stripping solution according to a bath ratio of 1:50. The concentration of thiourea dioxide in the stripping solution is 2 g / L, the concentration of sodium hydroxide is 6 g / L, and the concentration of Peregal O is 0.2 g / L. Put the cotton fabric into the stripping solution and carry out the stripping treatment in a constant temperature shaking water bath. Control the water bath temperature at 60 °C. After 20 min of treatment, take it out, wash it thoroughly with water, and then squeeze the fabric until it does not drip water.

[0044] Step (2): Oxidation treatment with sodium persulfate;

[0045] Put the cotton fabric after reduction treatment in step 1 into the sodium persulfate stripping solution. The concentration of sodium persulfate in the stripping solution is 6 g / L, the concentration of sodium hydroxide is 4 g / L, and the concentration of Peregal O is 0.2 g / L. Control the water bath temperature at 60 °C. After 20 min of treatment, take it out again, wash it thoroughly with water and dry it for subsequent testing.

[0046] Table 1 shows the performance indexes of the Reactive Blue KN-R dyed cotton fabric after stripping by the present invention.

[0047] Table 1

[0048]

[0049] As can be seen from Table 1, the present invention has a good stripping effect on anthraquinone reactive blue KN-R dyed cotton fabrics. After stripping with thiourea dioxide reduction, the stripping rate of the fabric is 84.13%, and the tensile retention rate of the fabric is 96.05%. After the second-step oxidation stripping, the stripping rate of the fabric increases by 12%, and the tensile retention rate of the fabric still remains above 90%. The whiteness value of the fabric also increases from 42.19 of the original fabric sample to 85.84. It can be seen that after the treatment of the present invention, the fabric has a high stripping rate, a high whiteness value obtained, and the service performance of the fabric is not affected, meeting the requirements for reusing after stripping.

[0050] Example 2

[0051] The cotton fabric used in this example is a phthalocyanine reactive dye reactive blue KN-G dyed cotton fabric, and the stripping is carried out by using the steps (1) and (2) in Example 1, with the parameters and operations remaining unchanged.

[0052] Table 2 shows the performance indexes of the reactive blue KN-G dyed cotton fabric after stripping.

[0053] Table 2

[0054]

[0055] As can be seen from Table 2, after stripping with thiourea dioxide reduction, the stripping rate of the fabric is 64.02%, and the tensile retention rate of the fabric is 94.15%. After the second-step oxidation stripping, the stripping rate of the fabric increases by nearly 20%, and the tensile retention rate of the fabric decreases slightly but still remains above 90%. The whiteness value of the fabric also increases from 55.65 of the original fabric sample to 78.66. The phthalocyanine reactive dye has a complex structure and strong stability. After the treatment of the present invention, its stripping rate still reaches 83%, and the tensile retention rate still remains above 90%, meeting the requirements for reusing after stripping.

[0056] Example 3

[0057] The dye used in this example is a bis-azo reactive dye reactive red M-3BE dyed cotton fabric, and the stripping is carried out by using the steps (1) and (2) in Example 1, with the parameters and operations remaining unchanged.

[0058] Table 3 shows the performance indexes of the reactive red M-3BE dyed cotton fabric after stripping.

[0059] Table 3

[0060]

[0061] Example 4 shows the test results of the stripping of the reactive red M-3BE dyed cotton fabric by the present invention. As can be seen from Table 4, after reduction stripping, the stripping rate of the fabric is 91.42%. After the second-step oxidation stripping, the stripping rate of the fabric increases to 98.75%, and the strength retention rate of the fabric still remains above 98%. The whiteness value of the fabric increases from 32.98 of the original fabric sample to 91.26. The whiteness of the fabric after stripping is relatively high, meeting the requirements for reuse.

[0062] Example 4

[0063] The dye used in this example is a monoazo reactive dye, reactive red X-3B dyed cotton fabric. The stripping is carried out using steps (1) and (2) in Example 1, with the parameters and operations remaining unchanged.

[0064] Table 4 shows the performance indicators of the reactive red X-3B dyed cotton fabric after stripping.

[0065] Table 4

[0066]

[0067] Table 5 shows the stripping test results of the reactive red X-3B dyed cotton fabric by the present invention. As can be seen from Table 5, after reduction stripping, the stripping rate of the fabric is 93.05%. After the second-step oxidation stripping, the stripping rate of the fabric increases to 98.63%, and the strength retention rate of the fabric still remains above 90%. The whiteness value of the fabric increases from 42.02 of the original fabric sample to 92.19. The whiteness of the fabric after stripping is relatively good. It can be seen that the present invention has excellent stripping effects on azo reactive dyes with relatively simple chromophore structures.

[0068] Comparative Example 1

[0069] Traditional stripping process: The object treated in this comparative example is an anthraquinone reactive dye, reactive blue KN-R dyed cotton fabric. The following steps are used for stripping:

[0070] Step (1): Reduction treatment with sodium hydrosulfite;

[0071] Weigh 5 g of the dyed cotton fabric, prepare the stripping solution according to a liquor ratio of 1:50. The concentration of sodium hydrosulfite in the stripping solution is 30 g / L, and the concentration of sodium hydroxide is 5 g / L. Put the cotton fabric into the stripping solution and carry out the stripping treatment in a constant-temperature shaking water bath. Control the water bath temperature at 90 °C. After 90 min of treatment, take it out, wash it thoroughly with water, and then squeeze the fabric until it stops dripping.

[0072] Step (2): Oxidation treatment with hydrogen peroxide;

[0073] Put the cotton fabric that has been restored in Step 1 into the hydrogen peroxide stripping solution. The concentration of hydrogen peroxide in the stripping solution is 75 ml / L, the concentration of sodium hydroxide is 15 g / L, and the concentration of EDTA is 10 g / L. Control the water bath temperature at 90 °C. After 90 minutes of treatment, take it out again, wash it thoroughly with water and dry it for subsequent testing.

[0074] The comparison of the effects of Example 1 and the traditional stripping process (sodium hydrosulfite combined with hydrogen peroxide) on the cotton fabric dyed with reactive blue KN-R is shown in Table 5.

[0075] Table 5

[0076]

[0077] It can be seen from Table 2 and Table 5 that the stripping rate obtained after stripping by the present invention is 96.05%, and the stripping rate obtained after stripping with sodium hydrosulfite combined with hydrogen peroxide is 97.80%. The strength retention rate obtained after stripping by the present invention is 93.25%, which is higher than 76.10% after treatment with sodium hydrosulfite combined with hydrogen peroxide. In addition, the treatment time of the present invention is 40 minutes and the treatment temperature is 60 °C, while the treatment time of stripping with sodium hydrosulfite combined with hydrogen peroxide is 180 minutes and the treatment temperature is 90 °C, indicating that the present invention has the advantages of high efficiency, time saving and low energy consumption. At the same time, the whiteness value of the present invention is significantly higher than that of the treatment with sodium hydrosulfite combined with hydrogen peroxide, indicating that the treatment of thiourea dioxide combined with sodium persulfate of the present invention is more suitable for stripping dyed waste textiles, and is more conducive to the re-dyeing and reuse of recycled fabrics.

[0078] Comparative Example 2

[0079] The object to be treated in this comparative example is the cotton fabric dyed with anthraquinone reactive dye reactive blue KN-R to reflect the synergistic effect of thiourea dioxide and sodium persulfate. Among them, only Step (1) is omitted, and only sodium persulfate is used for treatment. Combining with the data of Example 1, the results are shown in Table 6 below.

[0080] Table 6

[0081]

[0082] It can be seen from Table 6 that after stripping with thiourea dioxide alone, the stripping rate of the fabric is 84.13%, and the whiteness value is 65.61, which is only 55.5% higher than the original dyed fabric. After stripping with sodium persulfate alone, the obtained stripping rate is only 42.67%, and the obtained whiteness value is only 47.33, which is only 12% higher than the original dyed fabric. After stripping the sample by combining thiourea dioxide and sodium persulfate, the obtained stripping rate is increased to 96.05%, and the whiteness value is increased to 85.84, which is 103% higher than the whiteness value of the original fabric sample, achieving the effect that 1 + 1 is greater than 2, and reflecting the synergistic effect of thiourea dioxide and sodium persulfate on the improvement of the fabric whiteness.

[0083] Comparative Example 3

[0084] The object to be treated in this comparative example is the cotton fabric dyed with the anthraquinone reactive dye Reactive Blue KN-R. Among them, referring to the steps of Example 1, only the order of steps (1) and (2) is exchanged. The results are shown in Table 7 below.

[0085] Table 7

[0086]

[0087]

[0088] As can be seen from Table 7, the order of thiourea dioxide stripping and sodium persulfate stripping in the present invention is exchanged. First, sodium persulfate is used to oxidize and strip the sample, and then thiourea dioxide is used for reduction stripping. After being treated by this process, the final stripping rate of the fabric is only 79.45%, and the whiteness value is 63.49.

[0089] Comparative Example 4

[0090] Referring to the steps of Example 1, only the thiourea dioxide in step (1) is replaced with sodium hydrosulfite, and the results are shown in Table 8 below.

[0091] Table 8

[0092]

[0093] As can be seen from Table 8, replacing the thiourea dioxide stripping in the present invention with sodium hydrosulfite stripping, and on this basis, sodium persulfate is used for oxidation stripping. After being treated by this process, the stripping rate of the fabric is 91.45%, which is less than the stripping rate obtained after the treatment of the present invention. Compared with thiourea dioxide, sodium hydrosulfite has many disadvantages, such as being easily oxidized by air, decomposing quickly under humid and hot conditions, easily causing uneven stripping, and a large amount needs to be used during the stripping process to make up for the loss caused by decomposition. The thiourea dioxide used in the present invention is a reducing agent with a reduction potential higher than that of sodium hydrosulfite, and no irritating gas is generated during the use process. Thiourea dioxide decomposes slowly during use, the stripping is uniform, and the products after the reaction are sodium sulfate and urea, which cause little environmental pollution and are excellent substitutes for sodium hydrosulfite.

[0094] Comparative Example 5

[0095] Referring to the steps of Example 1, only the thiourea dioxide in step (1) is replaced with sodium bisulfite, and the results are shown in Table 9 below.

[0096] Table 9

[0097]

[0098] As can be seen from Table 9, replacing the use of thiourea dioxide for stripping in the present invention with the use of sodium bisulfite for stripping, and on this basis, further stripping with sodium sulfate. After such process treatment, the stripping rate of the fabric obtained is only 48.46%, the stripping effect is poor, and the strength retention rate is 92.37%.

[0099] Comparative Example 6

[0100] The steps of Example 1 were followed, wherein only the sodium persulfate in step (2) was replaced with hydrogen peroxide (40 g / L), and the results are shown in Table 10 below.

[0101] Table 10

[0102]

[0103] As can be seen from Table 10, replacing the use of sodium persulfate for stripping in the second step of the present invention with the use of hydrogen peroxide for stripping, after such process treatment, the stripping rate of the fabric obtained is only 90.08%, and the strength retention rate is 93.49%. As an oxidant, sodium persulfate has high solubility in water, a wide applicable pH range, and can be activated by various methods such as heat and alkali, and then generate sulfate radicals with oxidizing properties to oxidize and degrade the substrate. While hydrogen peroxide needs to be used under high temperature and strong alkali conditions, which will cause certain damage to the fabric fibers. In addition, hydrogen peroxide is easily decomposed at high temperature, requires a large amount during stripping, has a long stripping time, and large energy consumption.

[0104] Comparative Example 7

[0105] The steps of Example 1 were followed, wherein only the sodium persulfate in step (2) was replaced with sodium hypochlorite, and the results are shown in Table 11 below.

[0106] Table 11

[0107]

[0108] As can be seen from Table 11, replacing the use of sodium persulfate for stripping in the second step of the present invention with the use of sodium hypochlorite for stripping, after such process treatment, the stripping rate of the fabric obtained is 87.33%, and the strength retention rate decreases slightly, being 90.25%. The aqueous solution of sodium hypochlorite is easily decomposed, has a pungent odor and strong corrosiveness, and is prone to generating chlorine-containing toxic substances such as chlorine during use, which is highly toxic to the human body.

[0109] Comparative Example 8

[0110] The steps of Example 1 were followed, wherein only the concentration of thiourea dioxide in step (1) was adjusted to 4 g / L, 6 g / L, and 8 g / L.

[0111] Table 12

[0112]

[0113] As can be seen from Table 12, with the increase in the concentration of thiourea dioxide, the stripping rate obtained after reduction stripping shows a slight decrease. After oxidation stripping with sodium sulfate, the stripping rate of the fabric does not show a significant change. This indicates that the increase in the concentration of thiourea dioxide does not affect the change in the final stripping rate of the fabric.

[0114] Comparative Example 9

[0115] It was carried out with reference to the steps of Example 1, wherein only the concentration of sodium persulfate in step (2) was adjusted to 8 g / L, 10 g / L, and 12 g / L.

[0116] Table 13

[0117]

[0118] As can be seen from Table 13, after the first-step stripping with thiourea dioxide, when the concentration of sodium persulfate is increased, the stripping rate of the fabric increases slightly but not significantly. When the concentration of sodium persulfate is 12 g / L, compared with 6 g / L used in the present invention, the stripping rate of the fabric only increases by about 2%, and the whiteness value of the fabric hardly changes.

[0119] In summary, the present invention synergistically uses thiourea dioxide and sodium persulfate to strip the waste cotton fabric. While retaining the wearing performance of the fabric, it maximally improves the stripping rate. Compared with the traditional stripping process, the stripping time and temperature are significantly reduced, achieving the combination of economy and efficiency, and providing a new method for stripping waste cotton fabric.

[0120] The embodiments provided above are not intended to limit the scope covered by the present invention, nor are the described steps intended to limit their execution order. Obvious improvements made by those skilled in the art to the present invention in combination with the existing common general knowledge also fall within the protection scope defined by the claims of the present invention.

Claims

1. A fabric stripping method with high efficiency in energy conservation and environmental protection, characterized in that, It includes the following steps; (1) Thiourea dioxide reduction treatment: Put the fabric into a stripping solution containing thiourea dioxide and NaOH, carry out impregnation stripping at a certain temperature, take it out after a certain time, wash with water, and obtain the reduced and stripped cotton fabric; (2) Sodium persulfate oxidation treatment: Put the fabric after the reduction treatment in step (1) into a stripping solution containing Na2S2O8 and NaOH, carry out the second oxidation stripping at a certain temperature, take it out again after a certain time, wash with water and then dry to obtain the stripped fabric.

2. The method according to claim 1, wherein The fabric described in step (1) includes cotton fabric, wool fabric, silk fabric, and fabric made of hydrophilic fibers.

3. The method according to claim 1, wherein The composition of the stripping solution in step (1) is as follows: the concentration of thiourea dioxide is 2 - 8 g / L, the concentration of sodium hydroxide is 4 - 8 g / L, and the concentration of Peregal O is 0.1 - 0.2 g / L.

4. The method according to claim 1, characterized in that, The stripping temperature in step (1) is 50 - 60 °C, and the stripping time is 20 - 25 min.

5. The method according to claim 1, characterized in that The composition of the stripping solution in step (2) is as follows: the concentration of sodium persulfate is 6 - 12 g / L, the concentration of sodium hydroxide is 4 - 8 g / L, and the concentration of Peregal O is 0.1 - 0.2 g / L.

6. The method according to claim 1, characterized in that The stripping temperature in step (2) is 50 - 60 °C, and the stripping time is 20 - 25 min.

7. A method for improving the whiteness of a fabric after stripping, characterized in that, It includes the following steps: S1. Thiourea dioxide reduction treatment: Put the fabric into a stripping solution containing thiourea dioxide and NaOH, carry out impregnation stripping at a certain temperature, take it out after a certain time, wash with water, and obtain the reduced and stripped cotton fabric; S2. Sodium persulfate oxidation treatment: Put the fabric after the reduction treatment in step S1 into a stripping solution containing Na2S2O8 and NaOH, carry out the second oxidation stripping at a certain temperature, take it out again after a certain time, wash with water and then dry to obtain the stripped fabric.

8. The method according to claim 1, characterized in that, The fabric described in step S1 includes cotton fabric, wool fabric, silk fabric, and fabric made of hydrophilic fibers.

9. The method according to claim 1, wherein In step S1, the composition of the stripping solution is as follows: the concentration of thiourea dioxide is 2 - 8 g / L, the concentration of sodium hydroxide is 4 - 8 g / L, and the concentration of Peregal O is 0.1 - 0.2 g / L; the stripping temperature is 50 - 60 °C, and the stripping time is 20 - 25 min.

10. The method according to claim 1, characterized in that In step S2, the composition of the stripping solution is as follows: the concentration of sodium persulfate is 6 - 12 g / L, the concentration of sodium hydroxide is 4 - 8 g / L, and the concentration of Peregal O is 0.1 - 0.2 g / L; the stripping temperature is 50 - 60 °C, and the stripping time is 20 - 25 min.

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