A method for stripping phthalocyanine-based reactive dyes from cotton fabric

Abstract

This invention discloses a method for stripping dyed cotton fabrics with phthalocyanine reactive dyes, belonging to the field of textile treatment. The method includes the following steps: (1) pre-mordant treatment: immersing the fabric in a solution containing a certain mass concentration of thiourea dioxide (TD) and Fe... 2+ The solution was pre-treated with trisodium citrate (TCD) at a certain temperature for a certain period of time, then removed and thoroughly washed with water to obtain Fe-loaded solution. 2+ (2) Hydrogen peroxide treatment: The fabric after the pre-mediating treatment in step (1) is placed in a stripping solution containing hydrogen peroxide and sodium pyrophosphate of a certain mass concentration, and the stripping is carried out at a certain temperature. After a certain time, it is taken out again, thoroughly washed with water and dried to obtain the stripped fabric.

Description

Technical Field

[0001] This invention belongs to the field of textile processing, and specifically relates to a method for stripping dye from cotton fabrics dyed with phthalocyanine reactive dyes. Background Technology

[0002] Stripping of textiles is a necessary step in repairing dyed and printed defective products and recycling colored waste fabrics. In actual production, stripping of textiles is mainly done by chemical methods, which use the oxidizing or reducing properties of chemical reagents to destroy the chromophores in the dye molecule structure and the bonds between the dye and the fiber to achieve the purpose of stripping.

[0003] Phthalocyanine dyes possess a chromophore consisting of a 16-center, 18π-electron cyclic conjugate composed of 8 nitrogen atoms and 8 carbon atoms. This chromophore exhibits excellent optical, thermal, and chemical stability. The vacancies within the central cavity of the ring can coordinate with various metals, resulting in diverse color characteristics, including vibrant colors and good dyeability. However, due to the highly stable structure of its chromophore group, traditional stripping methods for phthalocyanine dyed fibers and fabrics require a complex process: high-temperature alkaline boiling followed by stripping with a stripping agent in an alkaline environment. This process is complex, involves high temperatures, consumes significant energy, and yields low stripping rates. Therefore, finding a low-temperature, high-efficiency stripping method suitable for phthalocyanine dyed textiles is of great importance. Summary of the Invention

[0004] [Technical Issues]

[0005] The traditional stripping process for textiles dyed with phthalocyanine dyes has several drawbacks: the dyed fabric needs to be boiled in high temperature alkali before stripping, making the process complex; the stripping agent produces hazardous substances during use, which are harmful to the environment and human health; the stripping agent is unstable and difficult to transport and store; the stripping process requires high temperature and consumes a lot of energy; the dye removal effect is not thorough enough, and the stripping rate and whiteness of the fabric are low after stripping, leaving the base color, which is not conducive to subsequent reuse.

[0006] [Technical Content]

[0007] The purpose of this invention is to overcome the shortcomings of traditional phthalocyanine dye-dyed textiles, such as complex stripping processes, high energy consumption, and low stripping rates, and to provide a low-temperature, high-efficiency stripping method based on the Fenton reaction. This method utilizes the highly oxidizing hydroxyl radicals generated during the Fenton reaction to oxidize and degrade the chromophores of the dye, achieving efficient stripping. During the Fenton reaction, Fe... 2+Fenton's reagent can catalyze the production of hydroxyl radicals from H₂O₂. Hydroxyl radicals possess extremely strong oxidizing properties, with an oxidation potential reaching 2.8 eV. The Fenton reaction has a rapid initiation time and mild initiation conditions, proceeding even at low or room temperature. It is non-selective in its oxidizing properties, exhibiting oxidizing activity towards most organic compounds. Uncatalyzed hydrogen peroxide will decompose naturally, and the decomposition products pose no harm to humans or cause environmental pollution. In recent years, Fenton's reagent has been widely used in water pollution treatment and soil remediation research. However, research on the use of Fenton's reagent for the stripping of colored textiles is limited. Therefore, introducing the Fenton reaction into the field of textile stripping is of great significance for expanding the research scope of textile stripping and improving the recycling value of colored waste textiles.

[0008] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0009] A method for stripping dye from cotton fabrics dyed with phthalocyanine reactive dyes includes the following steps:

[0010] (1) Pre-treatment: The fabric is immersed in a solution containing a certain mass concentration of thiourea dioxide (TD) and Fe. 2+ The fabric is pre-treated in a solution containing trisodium citrate (TCD) at a certain temperature for a certain period of time, then removed and washed with water to obtain the pre-treated fabric.

[0011] (2) Hydrogen peroxide treatment: The fabric after the pre-treatment in step (1) is placed in a stripping solution containing a certain mass concentration of hydrogen peroxide and sodium pyrophosphate, and oxidized and stripped at a certain temperature. After a certain time, it is taken out again, washed with water and dried to obtain stripped fabric.

[0012] Furthermore, the fabric mentioned in step (1) includes cotton fabric, wool fabric, and silk fabric.

[0013] Furthermore, the composition of the treatment solution in step (1) is as follows: the concentration of thiourea dioxide is 1-8 g / L, the concentration of ferrous iron is 4-10 g / L, the concentration of trisodium citrate is 0.1-0.4 g / L, and the concentration of acetone O is 0.1-0.2 g / L.

[0014] Preferably, the composition of the treatment solution in step (1) is as follows: the concentration of thiourea dioxide is 1-8 g / L, the concentration of ferrous iron is 4-8 g / L, the concentration of trisodium citrate is 0.1-0.4 g / L, and the concentration of acetone O is 0.1-0.2 g / L.

[0015] Furthermore, in step (1), the ferrous iron is derived from soluble ferrous salts.

[0016] Furthermore, the bath ratio for pre-media treatment in step (1) is 1:30 to 60.

[0017] Furthermore, in step (1), the pre-media treatment temperature is 50-60℃ and the time is 30-35min.

[0018] Furthermore, the composition of the stripping solution in step (2) is as follows: the concentration of hydrogen peroxide is 20-70 g / L, the concentration of sodium pyrophosphate is 4-8 g / L, and the concentration of 0.1-0.2 g / L.

[0019] Preferably, the composition of the stripping solution in step (2) is as follows: the concentration of hydrogen peroxide is 20-40 g / L, the concentration of sodium pyrophosphate is 4-8 g / L, and the concentration of 0.1-0.2 g / L.

[0020] Furthermore, in step (2), the bath ratio for oxidative stripping is 1:30 to 60.

[0021] Furthermore, in step (2), the temperature for oxidative stripping is 50-60℃ and the time is 30-60 min.

[0022] [Beneficial Effects]

[0023] 1. The present invention has a high stripping rate and high whiteness of dyed cotton fabrics after stripping.

[0024] 2. The process conditions of this invention are mild, the peeling temperature is low, and the energy consumption is small.

[0025] 3. The present invention causes less damage to the fabric during the color stripping process and does not affect the wearability of the fabric after color stripping.

[0026] 5. The process of this invention is not selective for dyes and is suitable for stripping fabrics dyed with different types of dyes. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to specific embodiments.

[0028] The testing method for the indicators in this invention:

[0029] (1) Stripping rate: In D 65 Under light source and 10° field of view conditions, the test fabric was stacked into 4 layers, and the K / S value of the fabric was measured using a Datacolor colorimeter. The K / S value was measured at any five points, and the arithmetic mean was calculated.

[0030] (2) Strength retention rate: According to GB / T3923.1-2013 "Textiles - Tensile properties of fabrics - Part 1 Determination of breaking strength and elongation at break (strip method)", the fabric was cut into 5cm×30cm specifications, and the breaking strength of the cotton fabric before and after stripping was tested using a YG(B)026H-250 electronic fabric strength tester. Each sample was measured 3 times and the average value was calculated.

[0031] (3) Whiteness: The whiteness of the sample was measured using a WSD-3C intelligent digital whiteness meter according to the GB / T17644-2008 standard. Each sample was measured 3 times and the average value was calculated.

[0032] Example 1

[0033] This embodiment deals with cotton fabric dyed with phthalocyanine reactive dye Reactive Blue KN-G, and the following steps are used for dye stripping:

[0034] Step (1): Pre-media treatment;

[0035] Weigh 3g of dyed cotton fabric and prepare a treatment solution at a liquor ratio of 1:50. The stripping process is carried out in a constant temperature shaking water bath. The concentration of ferrous sulfate in the treatment solution is 4g / L, the concentration of thiourea dioxide is 2g / L, the concentration of trisodium citrate is 0.1g / L, and the concentration of O-type iodine is 0.2g / L. After heating the treatment solution to 60℃, immerse the dyed cotton fabric in the treatment solution and remove it after 30 minutes. Wash it thoroughly with water and then squeeze the fabric until it no longer drips.

[0036] Step (2): Hydrogen peroxide oxidation treatment;

[0037] The cotton fabric that underwent pre-modification and reduction treatment in step 1 was placed in a hydrogen peroxide stripping solution (liquor ratio 1:50). The concentration of hydrogen peroxide in the stripping solution was 40 g / L, the concentration of sodium pyrophosphate was 5 g / L, and the concentration of O was 0.2 g / L. The water bath temperature was controlled at 60℃. After treatment for 60 minutes, the fabric was removed again, thoroughly washed with water, and dried for subsequent testing.

[0038] Table 1 shows the performance indicators of cotton fabrics dyed with phthalocyanine reactive blue KN-G after stripping, according to the present invention.

[0039] Table 1

[0040]

[0041] As shown in Table 1, after TD-Fe 2+ After TCD pre-mordant treatment, the dye on the cotton fabric was partially reduced and degraded by TD, achieving a stripping rate of 73%. When the pre-mordant-treated cotton fabric was placed in an H2O2 stripping solution, the Fe2+ loaded on the cotton fabric... 2+ The catalytic decomposition of H2O2 generates hydroxyl radicals that oxidize and degrade the chromophores of the dye. After H2O2 oxidation and stripping, the stripping rate of the fabric increases to 92%, and the whiteness value of the fabric is further improved from 54.14 in the original sample to 84.19. After hydrogen peroxide oxidation and stripping, the strength retention rate of the fabric is also maintained above 90%. It can be seen that after treatment by the method of this invention, phthalocyanine dyes can be effectively removed, and the fabric can obtain a high whiteness value.

[0042] Comparative Example 1

[0043] The subject of this comparative example is cotton fabric dyed with phthalocyanine reactive dye Reactive Blue KN-G, in order to demonstrate TD-Fe 2+ - The catalytic effect of TCD pre-treatment on hydrogen peroxide. The steps in Example 1 were followed, except that step (1) was omitted and only step (2) was used to treat the sample. The results are shown in Table 2 below, based on the data from Example 1.

[0044] Table 2

[0045]

[0046] As shown in Table 2, the fabric without TD-Fe 2+ -TCD reduction pre-treatment, after only hydrogen peroxide stripping, resulted in a very low stripping rate of only 1.58% for the fabric, and the fabric whiteness value was only slightly increased compared to the original sample.

[0047] Comparative Example 2

[0048] The subject of this comparative example is cotton fabric dyed with the anthraquinone reactive dye Reactive Blue KN-G. To demonstrate the effect of Fe... 2+ Catalytic effect of hydrogen peroxide. The steps in Example 1 were followed, except that ferrous sulfate and TCD in step (1) were omitted, and only TD was used to reduce the dyed cotton fabric. Then, step (2) was used to treat the sample. The results are shown in Table 3 below, based on the data from Example 1.

[0049] Table 3

[0050]

[0051] Table 3 shows that the fabric is not treated with Fe 2+ Pre-mortar treatment, using only TD reduction treatment, resulted in a stripping rate of only 72.76% after H2O2 stripping, lower than the 92.56% stripping rate obtained in Example 1. The fabric's whiteness value was 72.70, also significantly lower than the 84.19 whiteness value obtained in Example 1. (Note: Fe...) 2+ It plays an important role in the decomposition of H2O2.

[0052] Comparative Example 3

[0053] The subject of this comparative example is cotton fabric dyed with anthraquinone reactive dye Reactive Blue KN-G. To demonstrate the reducing and protective effect of TD in the pre-mordant treatment process, the steps in Example 1 were followed, except that thiourea dioxide in step (1) was omitted, and only Fe was used. 2+The dyed cotton fabric was pre-treated with TCD, and then the sample was treated using step (2). The results are shown in Table 4 below, based on the data from Example 1.

[0054] Table 4

[0055]

[0056] As shown in Table 4, without the reduction treatment of thiourea dioxide, only substances containing Fe... 2+ When cotton fabrics were pre-mordanted in a TCD treatment solution, the color removal rate after hydrogen peroxide oxidation was only 16.42%. This is because the pre-mordanting solution lacked the reducing protection of thiourea dioxide, allowing a large amount of Fe to escape. 2+ It is oxidized to Fe by oxygen in the air. 3+ This significantly reduces the catalytic decomposition ability of hydrogen peroxide in subsequent oxidative stripping, resulting in a low stripping rate.

[0057] Comparative Example 4

[0058] The subject of this comparative example is cotton fabric dyed with phthalocyanine reactive dye Reactive Blue KN-G. The dyed cotton fabric was stripped using the following steps: wherein, Fe in step (1) was... 2+ Instead of using TCD, only TD is used to reduce the sample, removing Fe. 2+ The TCD was added to step (2) along with H2O2 to treat the sample. The specific steps for decolorization were as follows:

[0059] Step (1): Thiourea dioxide reduction treatment;

[0060] Weigh 5g of dyed cotton fabric and prepare a stripping solution at a liquor ratio of 1:50. The concentration of thiourea dioxide in the stripping solution is 2g / L, and the concentration of 0.2g / L is 0.2g / L. Place the cotton fabric in the stripping solution and perform stripping treatment in a constant temperature shaking water bath. Control the water bath temperature at 60℃ and treat for 30 minutes. Remove the fabric, wash it thoroughly with water, and then squeeze the fabric until it no longer drips.

[0061] Step (2): Fe 2+ / TCD / H2O2 one-bath oxidation and decolorization;

[0062] The cotton fabric that underwent reduction treatment in step 1 was placed in a hydrogen peroxide stripping solution with the following concentrations: ferrous sulfate 4 g / L, trisodium citrate 0.1 g / L, hydrogen peroxide 40 g / L, sodium pyrophosphate 5 g / L, and O-containing solution 0.2 g / L. The water bath temperature was controlled at 60°C. After treatment for 20 minutes, the fabric was removed again, thoroughly washed, and dried for subsequent testing.

[0063] Table 5

[0064]

[0065]

[0066] Table 5 shows that the stripping rate of the sample after only TD reduction treatment was 68.78%, and after Fe treatment... 2+ After oxidative stripping with the / TCD / H2O2 mixed stripping solution, the stripping rate of the fabric increased to 75.84%, and the whiteness value of the fabric increased slightly from 68.13 to 70.83.

[0067] Comparative Example 5

[0068] To demonstrate the superior stripping effect of this invention on phthalocyanine dyes, the stripping effect of this invention on phthalocyanine dyes is compared with that of other stripping processes. Other stripping process steps:

[0069] Step (1): Thiourea dioxide reduction treatment;

[0070] Weigh 5g of dyed cotton fabric and prepare a stripping solution at a liquor ratio of 1:50. The concentration of thiourea dioxide in the stripping solution is 2g / L, the concentration of sodium hydroxide is 6g / L, and the concentration of 0.2g / L of 0.5g O is 0.2g / L. Put the cotton fabric into the stripping solution and perform stripping treatment in a constant temperature shaking water bath. Control the water bath temperature at 60℃ and treat for 20 minutes. After treatment, take it out, wash it thoroughly with water, and then squeeze the fabric until it is no longer dripping.

[0071] Step (2): Sodium persulfate oxidation treatment;

[0072] The cotton fabric that underwent reduction treatment in step 1 was placed in a sodium persulfate stripping solution with a sodium persulfate concentration of 6 g / L, a sodium hydroxide concentration of 4 g / L, and a leveling agent concentration of 0.2 g / L. The water bath temperature was controlled at 60°C. After treatment for 20 minutes, the fabric was removed again, thoroughly washed with water, and dried for subsequent testing.

[0073] Based on the data from Example 1, the comparison results are shown in Table 6:

[0074] Table 6

[0075]

[0076] As shown in Table 6, compared with the two stripping methods, the stripping rate and whiteness value of the fabric obtained by the present invention are better than those of the dioxourea-sodium persulfate reduction oxidation stripping method, indicating that the present invention has high efficiency in degrading phthalocyanine dyes.

[0077] Comparative Example 6

[0078] The steps were performed according to Example 1, except that thiourea dioxide in step (1) was replaced with sodium hydrosulfite. The results are shown in Table 7 below.

[0079] Table 7

[0080]

[0081]

[0082] As shown in Table 7, when the reducing agent thiourea dioxide in the pre-treatment process of this invention is replaced with sodium hydrosulfite, the fabric obtained after hydrogen peroxide oxidation and color removal has a color removal rate of 84.30% and a fabric whiteness value of 77.81. Both are lower than the data obtained in Example 1. This is because thiourea dioxide has better reducing properties than sodium hydrosulfite, and compared to sodium hydrosulfite, thiourea dioxide decomposes more slowly during use, has a higher reduction potential, a longer reduction time, and produces sodium sulfate and urea as the products after the reaction, which have less environmental pollution and are an excellent substitute for sodium hydrosulfite.

[0083] Comparative Example 7

[0084] The steps were performed according to Example 1, except that thiourea dioxide in step (1) was replaced with sodium bisulfite. The results are shown in Table 8 below.

[0085] Table 8

[0086]

[0087] As shown in Table 8, when the reducing agent thiourea dioxide in step (1) of this invention is replaced with sodium bisulfite, the stripping rate of the fabric after hydrogen peroxide stripping is only 34.02%, and the fabric whiteness value increases from 54.14 to 60.11. This is because sodium bisulfite has weak reducing properties, and its reducing power is insufficient to protect Fe in the pre-mortar treatment process. 2+ It is oxidized, resulting in a lower peeling rate and whiteness value.

[0088] Comparative Example 8

[0089] The procedure was performed according to Example 1, except that the hydrogen peroxide in step (2) was replaced with sodium persulfate. The results are shown in Table 9 below.

[0090] Table 9

[0091]

[0092] As shown in Table 9, after replacing the hydrogen peroxide in step (2) of this invention with sodium persulfate, the final color removal effect of the fabric is poor. Persulfate can be reacted with Fe... 2+ The catalytic generation of sulfate radicals, which have oxidizing properties, has a lower oxidation potential than the hydroxyl radicals generated by the decomposition of hydrogen peroxide, and therefore its color-peeling effect is inferior to that of the present invention.

[0093] Comparative Example 9

[0094] The steps are the same as in Example 1, except that the concentration of thiourea dioxide in step (1) is adjusted to 4 g / L, 6 g / L, and 8 g / L, while the other steps remain unchanged.

[0095] Table 10

[0096]

[0097] Table 10 shows the effects of different concentrations of thiourea dioxide on the fabric's color peeling rate, strength retention rate, and whiteness value. With increasing thiourea dioxide dosage, the reducing power of the solution system increases, and the oxidized Fe... 2+ Reduce, thus having more Fe 2+ Loading H2O2 onto cotton fabrics catalyzes the destruction of dye chromophores, thus the fabric's stripping rate and whiteness value increase with increasing thiourea dioxide concentration.

[0098] Comparative Example 10

[0099] The procedure is carried out according to Example 1, except that only Fe in step (1) is used. 2+ The concentrations were adjusted to 2 g / L, 4 g / L, 6 g / L, 8 g / L, and 10 g / L.

[0100] Table 11

[0101]

[0102] As shown in Table 11, the Fe in step (1) of this invention 2+ The concentrations were adjusted to 4 g / L, 6 g / L, 8 g / L, and 10 g / L, when Fe 2+ Increasing the concentration from 2 g / L to 4 g / L significantly improved the fabric's stripping rate and whiteness value, but with the increase of Fe... 2+ As the concentration continues to increase, the color peeling of the fabric gradually slows down; conversely, the whiteness value of the fabric increases with increasing Fe content. 2+ The decrease in concentration with increasing concentration indicates an excess of Fe. 2+ Excessive Fe is not conducive to color removal. 2+ It will cause H2O2 to decompose ineffectively, and excess Fe 2+ It will also remain on the fabric surface and be oxidized into Fe. 3+ This causes a decrease in the whiteness value of the fabric.

[0103] Comparative Example 11

[0104] The steps are carried out according to Example 1, except that the concentration of hydrogen peroxide in step (2) is adjusted to 30 g / L, 50 g / L, 60 g / L, and 70 g / L.

[0105] Table 12

[0106]

[0107] Table 12 shows that as the amount of hydrogen peroxide increases, the Fe in the stripping solution... 2+ The more free radicals such as hydroxyl radicals generated by catalytic decomposition, the better the color removal effect of the fabric. When the hydrogen peroxide concentration exceeds 40 g / L, the growth rate of the fabric's color removal rate and whiteness value slows down. Further increasing the concentration of hydrogen peroxide has no significant effect on the color removal effect. Excessive hydrogen peroxide will also have an adverse effect on the fabric's strength.

[0108] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for stripping dye from cotton fabrics dyed with phthalocyanine reactive dyes, characterized in that, Includes the following steps: (1) Pre-mordant treatment: The cotton fabric is placed in the treatment solution and pre-mordant treated at 50~60 ℃ for 30~35 min. After that, it is taken out and thoroughly washed with water to obtain the pre-mordant treated fabric. The composition of the treatment solution is: the concentration of thiourea dioxide is 4~8 g / L, the concentration of ferrous iron is 4~8 g / L, the concentration of trisodium citrate is 0.1~0.4 g / L, and the concentration of 0.1~0.2 g / L. (2) Oxidation treatment: The fabric after the pre-media treatment in step (1) is placed in the stripping solution and oxidized and stripped at a certain temperature. After a certain time, it is taken out again, thoroughly washed with water and dried to obtain the stripped fabric. The stripping solution is composed of: hydrogen peroxide concentration of 40-60 g / L, sodium pyrophosphate concentration of 4-8 g / L, and 0.1-0.2 g / L of acetone O.

2. The color stripping method according to claim 1, characterized in that, In step (1), the bath ratio for pre-media treatment is 1:30~60.

3. The color stripping method according to claim 1, characterized in that, In step (2), the bath ratio for oxidative stripping is 1:30~60, the temperature is 50~60 ℃, and the time is 30-60 min.

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