A decolorization method for colored nylon fabric and a dyeing method for nylon fabric

Abstract

The present invention belongs to the technical field of decolorization and dyeing and finishing of waste textiles, and relates to a decolorization method for colored nylon fabrics and a dyeing method for nylon fabrics. Decolorization method: The colored nylon fabric is placed in a decolorization solvent for decolorization, and the decolorized nylon fabric and the colored waste liquid are separated after decolorization, and the decolorization solvent is a mixed solution of D5 and DMSO with a mass ratio of 1-3:2. Dyeing method: When the colored nylon fabric is decolorized, the colored waste liquid is collected, and the DMSO in the colored waste liquid is separated to obtain a concentrated colored waste liquid, and D5 is added to the concentrated colored waste liquid to be configured into a dyeing liquid, and the pH value of the dyeing liquid is adjusted to 3.5-5.5, and then the nylon fabric is dyed. The present invention compounds D5 with DMSO, which not only improves the decolorization rate of the colored nylon fabric, but also can use D5 / DMSO as a dyeing medium to recycle the colored waste liquid, thereby reducing the harm of the dye to the environment and human health.

Description

Technical Field

[0001] The invention belongs to the technical field of decolorization and dyeing and finishing of waste textiles, and relates to a decolorization method for colored nylon fabrics and a dyeing method for nylon fabrics. Background Art

[0002] Chemical decolorization has a wide range of applications and a short decolorization time. It has a good decolorization effect on fibers dyed with various dyes. However, traditional chemical decolorization methods are often carried out under strong alkali and high temperature conditions, which will cause irreversible damage to the fibers. Therefore, it is necessary to add additives or surfactants to reduce the temperature and alkali dosage, but it also leads to poor biochemical properties of the decolorization effluent, increasing the difficulty of subsequent treatment. For example, the document (Nylon Variegated Waste Short Flannel Decolorization Process, 1997.) decolorizes nylon variegated waste short lint by successively treating it with liquid alkali, anisole, and reducing agent FM. The decolorization process of this decolorization method is complicated, the cost of waste liquid treatment is high, and it causes certain damage to the fabric. The patent with publication number CN109403101A discloses a method for decolorizing fabrics dyed with acid dyes under low temperature conditions. The preparation process of the low-temperature decolorization catalyst used is complicated, the raw materials used are expensive and cannot be recycled and reused, and compared with the traditional thiourea dioxide reduction decolorization, the irreversible damage to the fabric is greater.

[0003] The physical decolorization process is simple and easy to operate and does not damage the fabric, but the decolorization effect is worse than that of the chemical method, and the organic solvents used are usually toxic, so a large amount of colored solvent waste liquid needs to be recycled and treated. With the continuous progress of scientific research, it is expected to find or design a specific solvent system to improve the decolorization effect. Dimethyl sulfoxide (DMSO) is a highly polar aprotic organic solvent, which has been widely used as a swelling agent in the pre-treatment of waste textile stripping. Since the solubility parameter of DMSO is very similar to that of polyamide 6, the literature (Complete separation of colorants from polymeric materials for cost-effective recycling of waste textiles, 2022) has proved that this characteristic of DMSO can be combined with the regulation of process parameters such as temperature and pH value to achieve non-destructive and complete decolorization of waste polyamide 6 textiles. However, for industrially dyed and fixed polyamide 6 textiles, the decolorization ability of DMSO is greatly reduced (under the neutral environment of DMSO, the decolorization rate of primary decolorization is only about 20%, and the decolorization rate of secondary decolorization is only about 50%).

[0004] Therefore, it is necessary to improve the prior art in order to solve the above problems. Summary of the invention

[0005] The purpose of the invention is to solve the problem in the prior art that DMSO has a poor decolorization effect on industrially dyed and fixed nylon fabrics, provide a decolorization method for colored nylon fabrics, and on this basis propose a dyeing method for nylon fabrics.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A decolorization method for colored nylon fabric comprises placing the colored nylon fabric in a decolorization solvent for decolorization, separating the decolorized nylon fabric and colored waste liquid after decolorization, wherein the decolorization solvent is a mixed solution of D5 and DMSO in a mass ratio of 1-3:2.

[0008] The present invention adopts a mixed solution of D5 (decamethylcyclopentasiloxane) and DMSO (dimethyl sulfoxide) as a decolorizing solvent. D5 has a very small surface tension (D5 is about 19-21 mN / m, water is about 72.8 mN / m, and DMSO is 43.5 mN / m), which makes D5 have good spreadability, wettability and permeability. D5 can quickly penetrate into the interior of nylon fiber to make it swell, and as a transmission medium, it can bring DMSO into the interior of the fiber more quickly and bring the separated dye into DMSO more quickly, thereby improving the decolorization efficiency.

[0009] The mass ratio of D5 to DMSO in the decolorizing solvent is controlled to be 1-3:2. Since the mass ratio of DMSO to fabric is very small, if the proportion of D5 in the decolorizing solvent is too small, the penetration and swelling effect of a very small amount of D5 on the fabric is very weak. If the proportion of D5 in the decolorizing solvent is too large, a large amount of D5 mixed in will greatly change the solubility parameter and polarity of the original DMSO unit solvent system, thereby weakening the maximum degree of swelling that DMSO can form on the fabric, and finally reducing the decolorizing effect.

[0010] As the preferred technical solution:

[0011] In the above-mentioned decolorization method for colored nylon fabric, during decolorization, the bath ratio (mass ratio of colored nylon fabric to decolorization solvent) is 1:5-20, the temperature is 100-120°C, and the time is 20-40 minutes.

[0012] The decolorization temperature of the present invention is set at 100-120° C. in order to allow DMSO to swell the nylon fiber to the greatest extent possible without dissolving the nylon, thereby destroying the binding force between the dye and the nylon fiber (including van der Waals forces, ionic bonds, hydrogen bonds, etc.).

[0013] When the prior art uses DMSO as a decolorization solvent, under the premise of the same decolorization temperature, a longer decolorization time is required to achieve a decolorization rate equivalent to that of the present invention. Under the premise of the same decolorization time, a higher temperature is required to achieve a decolorization rate equivalent to that of the present invention.

[0014] In the decolorization method of colored nylon fabric as described above, the decolorization solvent does not contain alkali; before decolorization, the colored nylon fabric is sequentially alkali washed, water washed, and dried (air-dried); during alkali washing, the colored nylon fabric is added to the alkali solution, heated to 50-70°C and then kept warm.

[0015] When DMSO is used as a decolorizing solvent in the prior art, in order to achieve a better decolorizing effect, DMSO needs to be adjusted to a medium-strong base (pH ≥ 10), and the bath ratio must be higher than 1:20. Commonly used alkaline agents (such as sodium hydroxide and potassium hydroxide) are insoluble in DMSO, so a small amount of water needs to be added for preparation, but a large amount of alkaline agents will still precipitate. After 2-3 decolorization cycles, the nylon fabric turns yellow due to a side reaction due to long-term exposure to medium-strong alkali and high temperature during the decolorization process, and may even react to the chromophores of some dyes. The colored waste liquid is also medium-strong alkaline, with a large amount of alkaline agents precipitated, and it also contains various residual auxiliaries (such as leveling agents, color fixatives, softeners, etc.) that have been boiled off, with poor physical and chemical properties and low purity. In the subsequent solvent distillation recovery and reuse process, the alkaline DMSO is easy to decompose, and the sulfur atoms in DMSO may be attacked by the nucleophilic attack of hydroxide ions, resulting in the breakage of SO bonds or CS bonds, and may generate dimethyl sulfide and other oxygen-containing compounds. From the perspective of reaction mechanism, hydroxide ions can trigger a rearrangement reaction within the DMSO molecule, causing some groups to detach and accompanied by the formation of new chemical bonds, which will lead to a decrease in the recovery rate of DMSO. Therefore, acid-base neutralization is required before distillation.

[0016] The present invention performs alkali washing on the colored nylon fabric before decolorization, and the temperature of the alkali washing is 50-70°C, near the glass transition temperature (60°C) of nylon, so that the hydroxide ions can fully enter the chain segments of the nylon, weaken the ionic bond between the dye and the nylon terminal amino group in advance and protect the free terminal amino group, so that the subsequent decolorization process only needs to be carried out under neutral conditions to achieve excellent decolorization effect, so that the colored waste liquid has better physical and chemical properties, and the yellowing of the nylon fabric and the deformation of the dye are avoided. In addition, the alkali washing can be used as a process similar to washing to wash the additives and impurities remaining on the surface of the nylon fabric in advance, thereby further improving the purity of the colored waste liquid.

[0017] In the decolorization method of colored nylon fabric as described above, during alkali washing, the bath ratio (mass ratio of colored nylon fabric to alkali solution) is 1:20-40, the concentration of alkali solution is 10-30g / L, the heating rate is 2-5℃ / min, and the holding time is 20-40min.

[0018] In the method for decolorizing colored nylon fabric as described in any one of the above items, after separating the decolorized nylon fabric and the colored waste liquid, the decolorized nylon fabric is sequentially subjected to D5 washing, water washing and drying (air-drying).

[0019] A decolorization method for colored nylon fabric as described above, wherein the dye in the colored nylon fabric is an acid dye or a disperse dye;

[0020] The dyes used for nylon dyeing are mainly acid dyes, disperse dyes, direct dyes, and reactive dyes. The decolorization method of the present invention has a decolorization effect on these four types of dyes, among which the decolorization effect on acid dyes and disperse dyes is particularly excellent. Therefore, the present invention selects colored nylon fabrics with acid dyes and / or disperse dyes for exemplary description;

[0021] When the dye in the colored nylon fabric is an acid dye, since D5 itself does not dissolve the acid dye, liquid separation can be achieved through the difference in surface tension and density between solvents, and there is no recycling cost. Specifically, after washing with D5 and before washing with water, the washing liquid (composed of D5 and DMSO) is also collected, and the washing liquid is kept at the decolorization temperature for 1-5 minutes. During this process, D5 and DMSO are obviously separated, and liquid separation can be achieved through a separating funnel, thereby obtaining clean D5; after washing with water, the washing liquid (composed of D5 and water) is also collected, and the washing liquid is left to stand for 1-2 hours or heated to 50-70°C for insulation. During this process, D5 and water are obviously separated, and liquid separation can be achieved through a separating funnel, thereby obtaining clean D5;

[0022] When the dye in the colored nylon fabric is a disperse dye, since D5 does not dissolve disperse dyes at room temperature but can dissolve disperse dyes at high temperatures, if D5 is to be recovered, the above separation and purification process of D5 needs to be adjusted;

[0023] The decolorization rate of bleached nylon fabric calculated according to K / S value is more than 95%, the strength retention rate measured according to GB / T 3923.1-2013 is more than 95%, and the whiteness measured according to GB / T 17644-2008 is 70-80.

[0024] A dyeing method for nylon fabric, wherein when decolorizing the colored nylon fabric using a decolorizing method for colored nylon fabric as described in any one of the above items, the colored waste liquid is collected, DMSO in the colored waste liquid is separated to obtain concentrated colored waste liquid, D5 is added to the concentrated colored waste liquid to prepare a dyeing solution, the pH value of the dyeing solution is adjusted to 3.5-5.5, and then the nylon fabric is dyed.

[0025] The present invention utilizes D5 as a dyeing medium, can re-dye the detached dye onto the nylon fabric as much as possible, and realizes direct recycling of D5.

[0026] As the preferred technical solution:

[0027] In the dyeing method of nylon fabric as described above, DMSO in the colored waste liquid is separated by reduced pressure distillation; during reduced pressure distillation, when the condensation port temperature of the distillation device reaches 60-65°C, the condensation water and the vacuum pump are turned on; when the gas phase temperature reaches and is maintained at 80-85°C and the vacuum degree is 0.094-0.105MPa, the water in the colored waste liquid has been completely distilled; when the gas phase temperature reaches and is maintained at 85-90°C, DMSO is gradually distilled.

[0028] In the dyeing method of nylon fabric as described above, the content of concentrated colored waste liquid in the dye liquor is 1-5wt%; during dyeing, the bath ratio (mass ratio of nylon fabric to dye liquor) is 1:15-30, and the temperature is raised to 95-99°C at a heating rate of 2-5°C / min and then kept warm for 1-2h.

[0029] The dyeing method of nylon fabric as described above further includes color fixing, soaping and washing in sequence after dyeing.

[0030] According to the dyeing method for nylon fabric as described above, after dyeing, the dye uptake rate of the nylon fabric is above 97%.

[0031] Beneficial effects:

[0032] (1) The present invention provides a method for decolorizing colored nylon fabrics. The nylon fabrics are first subjected to an alkali washing pretreatment, which can not only effectively remove impurities and residual chemical additives on the surface of the fabrics and improve the physical and chemical properties of the colored waste liquid for easy recycling, but also weaken the binding force between the acid dye and the amino group of the nylon through the hydroxide ions in the alkali solution, thereby improving the decolorization performance of DMSO.

[0033] (2) The decolorization method of the present invention adopts a DMSO / D5 binary system, in which the addition of D5 has a dual effect: on the one hand, since D5 has an extremely low surface tension, it can accelerate the penetration of DMSO into the fiber and promote the diffusion of the stripped dye, thereby greatly improving the decolorization efficiency; on the other hand, since D5 does not dissolve acid dyes and can separate from DMSO and water, the cost of solvent recovery is greatly reduced.

[0034] (3) The present invention uses DMSO / D5 as a decolorizing medium, and can also re-dye the removed acid dye onto the fabric, giving the meaning of dye regeneration. This method not only reduces the harm of dyes to the environment and human health, but also realizes the efficient recycling of resources in the process of recycling waste textiles, and has significant economic benefits and social values ​​such as energy saving, environmental protection, and ecology. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the decolorization kinetics of nylon fabrics with different dyeing processes under different decolorization processes; in the figure, Fblue-AW-DMSO / D5 is a colored nylon fabric sample decolorized in the DMSO / D5 system, Fblue-AW-DMSO is a colored nylon fabric sample decolorized in the DMSO system, and Blue-AW-DMSO is a non-fixed nylon fabric sample decolorized in the DMSO system;

[0036] Figure 2 It is a schematic diagram of the two-stage fitting of the first-order kinetics of nylon fabrics with different dyeing processes under different decolorization processes; in the figure, Fblue-AW-DMSO / D5 is the decolorization of colored nylon fabric samples in the DMSO / D5 system, Fblue-AW-DMSO is the decolorization of colored nylon fabric samples in the DMSO system, and Blue-AW-DMSO is the decolorization of unfixed nylon fabric samples in the DMSO system; it should be noted that the data points used for fitting in the figure are representative data points in the actual experimental process. Since the dividing point between the fast decolorization stage (the first decolorization stage) and the slow decolorization stage (the second decolorization stage) is not selected, the line segments on the figure are disconnected, but this does not affect the conclusions that can be shown by the data in the figure. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0038] Test methods for relevant performance indicators in the embodiments and comparative examples:

[0039] Decolorization rate: calculated according to the K / S value, using UltraScan PRO spectrophotometer, under the conditions of D65 light source, 10° viewing angle, reflection mode UV400 cutoff, φ18, the K / S value of the textile before and after decolorization was measured. Each group of samples was measured 4 times, and the average value was taken. The decolorization rate of the fabric was calculated according to the following formula:

[0040] 00%;

[0041] Where: is the K / S value of the textile before bleaching, It is the K / S value of the textile after bleaching.

[0042] Strength retention rate: Use YG 026B electronic fabric strength tester, according to GB / T 3923.1--2013 "Tensile properties of textile fabrics Part 1 Determination of breaking strength and elongation at break (strip method)" standard, and calculate the strength retention rate of the fabric according to the following formula:

[0043] 00%;

[0044] Where: is the breaking strength of the textile before bleaching, It is the breaking strength of the textile after bleaching.

[0045] Whiteness: measured according to GB / T 17644-2008, fold the fabric into 8 layers, use WSB-2 digital whiteness meter to measure, measure 5 times in parallel, and take the average value (whiteness is expressed as a percentage, usually record the value directly without "%").

[0046] Example 1

[0047] A method for decolorizing colored nylon fabric comprises the following steps:

[0048] (1) Prepare materials:

[0049] Decolorization solvent: a mixture of D5 and DMSO in a mass ratio of 1:2, without alkali;

[0050] Colored nylon fabric: industrially dyed and fixed nylon fabric, specifically FDY fully drawn nylon series No. 38 (70D / 48F; knitted; matte; dark blue) produced by Zhejiang Jiahua Special Nylon Co., Ltd.

[0051] Alkali solution: sodium hydroxide aqueous solution with a concentration of 30g / L;

[0052] (2) Alkaline washing:

[0053] The colored nylon fabric was placed in an alkali solution at a bath ratio of 1:20, heated to 60°C at a heating rate of 2°C / min, and then kept warm for 30 minutes, followed by washing and drying in sequence;

[0054] (3) Decolorization:

[0055] The colored nylon fabric after alkali washing was placed in a decolorizing solvent at a bath ratio of 1:10, and after decolorization at 110°C for 30 minutes, the decolorized nylon fabric and the colored waste liquid were separated, and then D5 washing (80°C, bath ratio of 1:10), water washing and drying were carried out in sequence;

[0056] By adopting the method for decolorization, the decolorization rate of the decolorized nylon fabric is 97%, the strength retention rate is 98%, and the whiteness is 75.

[0057] A method for dyeing nylon fabrics, comprising: collecting colored waste liquid when decolorizing the colored nylon fabric in the above step (3), separating DMSO in the colored waste liquid by vacuum distillation to obtain concentrated colored waste liquid; adding D5 to the concentrated colored waste liquid to prepare a dye liquor, wherein the content of the concentrated colored waste liquid in the dye liquor is 1wt%; adjusting the pH value of the dye liquor to 3.5, adding the nylon fabric to the dye liquor at a bath ratio of 1:15, heating the dye liquor to 99°C at a rate of 5°C / min and keeping the temperature for 2h, and then sequentially performing color fixation, soap washing and water washing; wherein a cationic color fixative (manufacturer: Dongguan Jiewei Industrial Co., Ltd., brand: JV-6030) is used for color fixation, the amount of the color fixative is 3% owf, the color fixation temperature is 60°C, the color fixation time is 30 min, and the bath ratio is 1:15;

[0058] The dyeing method is used to dye the nylon fabric, and the dye uptake rate measured according to GB / T 23976.1-2009 is 100%.

[0059] Comparative Example 1

[0060] A decolorization method for colored nylon fabric is basically the same as the decolorization method for colored nylon fabric in Example 1, except that: in the decolorization solvent of this comparative example, the mass ratio of D5 to DMSO is 1:5.

[0061] The decolorization method of this comparative example is adopted, and the decolorization rate of the decolorized nylon fabric is 92%, the strength retention rate is 97%, and the whiteness is 63.

[0062] Comparative Example 2

[0063] A decolorization method for colored nylon fabric is basically the same as the decolorization method for colored nylon fabric in Example 1, except that: in the decolorization solvent of this comparative example, the mass ratio of D5 to DMSO is 5:1.

[0064] The decolorization method of this comparative example is adopted, and the decolorization rate of the decolorized nylon fabric is 90%, the strength retention rate is 97%, and the whiteness is 60.

[0065] Compared with Example 1, the decolorization effects of Comparative Examples 1 and 2 are worse. This is because, when the proportion of D5 in the decolorization solvent is too small, the penetration and swelling effect of a very small amount of D5 on the fabric is weak, and the decolorization effect is not good; and when the proportion of D5 is too large, the mixing of a large amount of D5 will significantly change the solubility parameters and polarity of the original DMSO unit solvent system, thereby weakening the maximum swelling capacity of DMSO on the fabric, resulting in a decrease in the decolorization effect.

[0066] Example 2

[0067] A method for decolorizing colored nylon fabric comprises the following steps:

[0068] (1) Prepare materials:

[0069] Decolorization solvent: a mixture of D5 and DMSO in a mass ratio of 3:2, without alkali;

[0070] Colored nylon fabric: nylon fabric that has been industrially dyed and fixed, specifically CF68-01 (water blue) produced by Yuanchuangfa Publishing House in Yanbu, Nanhai, Foshan;

[0071] Alkali solution: sodium hydroxide aqueous solution with a concentration of 15g / L;

[0072] (2) Alkaline washing:

[0073] The colored nylon fabric was placed in an alkali solution at a bath ratio of 1:30, heated to 65°C at a heating rate of 2.5°C / min, and then kept warm for 25 minutes, followed by washing and drying in sequence;

[0074] (3) Decolorization:

[0075] The colored nylon fabric after alkali washing was placed in a decolorizing solvent at a bath ratio of 1:10, and after decolorizing at 100°C for 30 minutes, the decolorized nylon fabric and the colored waste liquid were separated, and then D5 washing (80°C, bath ratio of 1:10), water washing and drying were carried out in sequence;

[0076] By adopting this method to decolorize, the decolorization rate of the decolorized nylon fabric is 98%, the strength retention rate is 97%, and the whiteness is 78.

[0077] If D5 in the decolorization solvent is replaced with DMSO of equal mass, the decolorization rate of the decolorized nylon fabric is 93% when the decolorization temperature and decolorization time remain unchanged; when the decolorization temperature and decolorization rate remain unchanged, the decolorization time needs to be extended to 50 minutes; when the decolorization time and decolorization rate remain unchanged, the decolorization temperature needs to be increased to 115°C.

[0078] A method for dyeing nylon fabrics, comprising: collecting colored waste liquid when decolorizing colored nylon fabrics in the above step (3), separating DMSO in the colored waste liquid by vacuum distillation to obtain concentrated colored waste liquid; adding D5 to the concentrated colored waste liquid to prepare a dye liquor, wherein the content of concentrated colored waste liquid in the dye liquor is 1wt%; adjusting the pH value of the dye liquor to 5.5, adding nylon fabric to the dye liquor at a bath ratio of 1:30, heating the dye liquor to 99°C at a rate of 2°C / min and keeping the temperature for 2h, and then sequentially performing color fixation, soap washing and water washing; wherein a cationic color fixative (manufacturer: Dongguan Jiewei Industrial Co., Ltd., brand: JV-6030) is used for color fixation, the amount of the color fixative is 3% owf, the color fixation temperature is 60°C, the color fixation time is 30 min, and the bath ratio is 1:15;

[0079] The dyeing method is used to dye the nylon fabric, and the dye uptake rate measured according to GB / T 23976.1-2009 is 98%.

[0080] Example 3

[0081] A method for decolorizing colored nylon fabric comprises the following steps:

[0082] (1) Prepare materials:

[0083] Decolorization solvent: a mixture of D5 and DMSO in a mass ratio of 1.5:2, without alkali;

[0084] Colored nylon fabric: industrially dyed and fixed nylon fabric, specifically FDY fully drawn nylon series No. 38 (70D / 48F; knitted; matte; dark blue) produced by Zhejiang Jiahua Special Nylon Co., Ltd.

[0085] Alkali solution: sodium hydroxide aqueous solution with a concentration of 25g / L;

[0086] (2) Alkaline washing:

[0087] The colored nylon fabric was placed in an alkali solution at a bath ratio of 1:20, heated to 50°C at a heating rate of 3°C / min, and then kept warm for 20 minutes, followed by washing and drying in sequence;

[0088] (3) Decolorization:

[0089] The colored nylon fabric after alkali washing was placed in a decolorizing solvent at a bath ratio of 1:5, and after decolorizing at 100°C for 20 minutes, the decolorized nylon fabric and the colored waste liquid were separated, and then D5 washing (80°C, bath ratio of 1:10), water washing and drying were carried out in sequence;

[0090] By adopting the method for decolorization, the decolorization rate of the decolorized nylon fabric is 95%, the strength retention rate is 97%, and the whiteness is 70.

[0091] A method for dyeing nylon fabrics, comprising: collecting colored waste liquid when decolorizing colored nylon fabrics in the above step (3), separating DMSO in the colored waste liquid by vacuum distillation to obtain concentrated colored waste liquid; adding D5 to the concentrated colored waste liquid to prepare a dye liquor, wherein the content of concentrated colored waste liquid in the dye liquor is 3wt%; adjusting the pH value of the dye liquor to 4, adding the nylon fabric to the dye liquor at a bath ratio of 1:20, heating the dye liquor to 99°C at a rate of 4°C / min and keeping the temperature for 1.5h, and then sequentially performing color fixation, soap washing and water washing; wherein a cationic color fixative (manufacturer: Dongguan Jiewei Industrial Co., Ltd., brand: JV-6030) is used for color fixation, the amount of the color fixative is 3%owf, the color fixation temperature is 60°C, the color fixation time is 30 min, and the bath ratio is 1:15;

[0092] The dyeing method is used to dye the nylon fabric, and the dye uptake rate measured according to GB / T 23976.1-2009 is 99%.

[0093] Example 4

[0094] A method for decolorizing colored nylon fabric comprises the following steps:

[0095] (1) Prepare materials:

[0096] Decolorization solvent: a mixture of D5 and DMSO in a mass ratio of 2:2, without alkali;

[0097] Colored nylon fabric: nylon fabric that has been industrially dyed and fixed, specifically CF68-01 (water blue) produced by Yuanchuangfa Publishing House in Yanbu, Nanhai, Foshan;

[0098] Alkali solution: sodium hydroxide aqueous solution with a concentration of 20g / L;

[0099] (2) Alkaline washing:

[0100] The colored nylon fabric was placed in an alkali solution at a bath ratio of 1:25, heated to 60°C at a heating rate of 3.5°C / min, and then kept warm for 30 minutes, followed by washing and drying in sequence;

[0101] (3) Decolorization:

[0102] The colored nylon fabric after alkali washing was placed in a decolorizing solvent at a bath ratio of 1:20, and after decolorization at 110°C for 30 minutes, the decolorized nylon fabric and the colored waste liquid were separated, and then D5 washing (80°C, bath ratio of 1:10), water washing and drying were carried out in sequence;

[0103] By adopting the method for decolorization, the decolorization rate of the decolorized nylon fabric is 99%, the strength retention rate is 97%, and the whiteness is 80.

[0104] A method for dyeing nylon fabrics, comprising: collecting colored waste liquid when decolorizing colored nylon fabrics in the above step (3), separating DMSO in the colored waste liquid by vacuum distillation to obtain concentrated colored waste liquid; adding D5 to the concentrated colored waste liquid to prepare a dye liquor, wherein the content of concentrated colored waste liquid in the dye liquor is 1.5wt%; adjusting the pH value of the dye liquor to 5.5, adding nylon fabric to the dye liquor at a bath ratio of 1:30, heating the dye liquor to 99°C at a rate of 2°C / min and keeping the temperature for 2h, and then sequentially performing color fixation, soap washing and water washing; wherein a cationic color fixative (manufacturer: Dongguan Jiewei Industrial Co., Ltd., brand: JV-6030) is used for color fixation, the amount of the color fixative is 3% owf, the color fixation temperature is 60°C, the color fixation time is 30 min, and the bath ratio is 1:15;

[0105] The dyeing method is used to dye the nylon fabric, and the dye uptake rate measured according to GB / T 23976.1-2009 is 98%.

[0106] Example 5

[0107] A method for decolorizing colored nylon fabric comprises the following steps:

[0108] (1) Prepare materials:

[0109] Decolorization solvent: a mixture of D5 and DMSO in a mass ratio of 2.3:2, without alkali;

[0110] Colored nylon fabric: nylon fabric that has been industrially dyed and fixed, specifically CF68-01 (water blue) produced by Yuanchuangfa Publishing House in Yanbu, Nanhai, Foshan;

[0111] Alkali solution: sodium hydroxide aqueous solution with a concentration of 10g / L;

[0112] (2) Alkaline washing:

[0113] The colored nylon fabric was placed in an alkali solution at a bath ratio of 1:35, heated to 55°C at a heating rate of 4°C / min, and then kept warm for 35 minutes, followed by washing and drying in sequence;

[0114] (3) Decolorization:

[0115] The colored nylon fabric after alkali washing was placed in a decolorizing solvent at a bath ratio of 1:20, and after decolorization at 110°C for 30 minutes, the decolorized nylon fabric and the colored waste liquid were separated, and then D5 washing (80°C, bath ratio of 1:10), water washing and drying were carried out in sequence;

[0116] By adopting the method for decolorization, the decolorization rate of the decolorized nylon fabric is 99%, the strength retention rate is 98%, and the whiteness is 80.

[0117] A method for dyeing nylon fabrics, comprising: collecting colored waste liquid when decolorizing colored nylon fabrics in the above step (3); separating DMSO in the colored waste liquid by vacuum distillation to obtain concentrated colored waste liquid; adding D5 to the concentrated colored waste liquid to prepare a dye liquor, wherein the content of concentrated colored waste liquid in the dye liquor is 2wt%; adjusting the pH value of the dye liquor to 5.5, adding nylon fabric to the dye liquor at a bath ratio of 1:30, heating the dye liquor to 99°C at a rate of 2°C / min and keeping the temperature for 2h, and then performing color fixation, soap washing and water washing in sequence; wherein a cationic color fixative (manufacturer: Dongguan Jiewei Industrial Co., Ltd., brand: JV-6030) is used for color fixation, the amount of the color fixative is 3% owf, the color fixation temperature is 60°C, the color fixation time is 30 min, and the bath ratio is 1:15;

[0118] The dyeing method is used to dye the nylon fabric, and the dye uptake rate measured according to GB / T 23976.1-2009 is 97%.

[0119] Example 6

[0120] A method for decolorizing colored nylon fabric comprises the following steps:

[0121] (1) Prepare materials:

[0122] Decolorization solvent: a mixture of D5 and DMSO in a mass ratio of 2.6:2, without alkali;

[0123] Colored nylon fabric: industrially dyed and fixed nylon fabric, specifically FDY fully drawn nylon series No. 38 (70D / 48F; knitted; matte; dark blue) produced by Zhejiang Jiahua Special Nylon Co., Ltd.

[0124] Alkali solution: sodium hydroxide aqueous solution with a concentration of 30g / L;

[0125] (2) Alkaline washing:

[0126] The colored nylon fabric was placed in an alkali solution at a bath ratio of 1:40, heated to 70°C at a heating rate of 5°C / min, and then kept warm for 40 minutes, followed by washing and drying in sequence;

[0127] (3) Decolorization:

[0128] The colored nylon fabric after alkali washing was placed in a decolorizing solvent at a bath ratio of 1:15, and after decolorizing at 120°C for 40 minutes, the decolorized nylon fabric and the colored waste liquid were separated, and then D5 washing (80°C, bath ratio of 1:10), water washing and drying were carried out in sequence;

[0129] By adopting the method for decolorization, the decolorization rate of the decolorized nylon fabric is 98%, the strength retention rate is 95%, and the whiteness is 78.

[0130] A method for dyeing nylon fabrics, comprising: collecting colored waste liquid when decolorizing the colored nylon fabric in the above step (3), separating DMSO in the colored waste liquid by vacuum distillation to obtain concentrated colored waste liquid; adding D5 to the concentrated colored waste liquid to prepare a dye liquor, wherein the content of the concentrated colored waste liquid in the dye liquor is 5wt%; adjusting the pH value of the dye liquor to 3.5, adding the nylon fabric to the dye liquor at a bath ratio of 1:30, heating the dye liquor to 95°C at a rate of 3°C / min and keeping the temperature for 1h, and then sequentially performing color fixation, soap washing and water washing; wherein a cationic color fixative (manufacturer: Dongguan Jiewei Industrial Co., Ltd., brand: JV-6030) is used for color fixation, the amount of the color fixative is 3% owf, the color fixation temperature is 60°C, the color fixation time is 30 min, and the bath ratio is 1:15;

[0131] The dyeing method is used to dye the nylon fabric, and the dye uptake rate measured according to GB / T 23976.1-2009 is 99%.

[0132] The present invention also compares the decolorization kinetics of DMSO and DMSO / D5. Figure 1 , Figure 2As shown in Figure 1, by fitting the first-order kinetics of the decolorization process (bath ratio 1:10; decolorization temperature 130°C), the data results in Table 1 show that in the rapid decolorization stage, the decolorization reaction rate of the DMSO / D5 system is 0.134 mol·L -1 ·min -1 The decolorization reaction rate of the DMSO system is 0.114 mol·L -1 ·min -1 This shows that the addition of D5 can effectively increase the decolorization rate of DMSO. And as the decolorization temperature decreases, the fiber swelling degree decreases, and the improvement effect brought by D5 is more significant. Therefore, the gain effect brought by the addition of D5 is reflected in the process as a reduction in decolorization time or a reduction in decolorization temperature.

[0133] Table 1 Decolorization reaction rate constants of first-order kinetics with two-stage fitting

[0134] Sample name <![CDATA[k1(min -1 )]]> <![CDATA[k2(min -1 )]]> R1 R2 Fblue-AW-DMSO 0.114 0.010 0.972 0.925 Fblue-AW-DMSO / D5 0.134 0.016 0.962 0.963 Blue-AW-DMSO 0.142 0.050 0.964 0.999

[0135] In Table 1, k1 represents the reaction rate constant of the first decolorization kinetics fitting, R1 represents the correlation coefficient of the first decolorization kinetics fitting, k2 represents the reaction rate constant of the second decolorization kinetics fitting, and R2 represents the correlation coefficient of the second decolorization kinetics fitting.

Claims

1. A method for decolorizing colored nylon fabric, comprising placing the colored nylon fabric in a decolorizing solvent for decolorization, and separating the decolorized nylon fabric and the colored waste liquid after decolorization, characterized in that: The decolorizing solvent is a mixture of decamethylcyclopentasiloxane and DMSO in a mass ratio of 1-3:2; The decolorizing solvent does not contain alkali; before decolorizing, the colored nylon fabric is sequentially subjected to alkali washing, water washing and drying; during alkali washing, the colored nylon fabric is added into the alkali solution, heated to 50-70°C and then kept warm.

2. The method for decolorizing colored nylon fabric according to claim 1, characterized in that: When decolorizing, the bath ratio is 1:5-20, the temperature is 100-120℃, and the time is 20-40min.

3. The method for decolorizing colored nylon fabric according to claim 1, characterized in that: During alkali washing, the bath ratio is 1:20-40, the concentration of the alkali solution is 10-30g / L, the heating rate is 2-5℃ / min, and the insulation time is 20-40min.

4. A method for decolorizing colored nylon fabric according to any one of claims 1 to 3, characterized in that: After separating the decolorized nylon fabric and the colored waste liquid, the decolorized nylon fabric is sequentially washed with decamethylcyclopentasiloxane, washed with water and dried.

5. The method for decolorizing colored nylon fabric according to claim 4, characterized in that: The dyes in colored nylon fabrics are acid dyes or disperse dyes; The decolorization rate of the decolorized nylon fabric calculated according to the K / S value is more than 95%, the strength retention rate measured according to GB / T 3923.1-2013 is more than 95%, and the whiteness measured according to GB / T 17644-2008 is 70-80.

6. A method for dyeing nylon fabric, characterized in that: When the colored nylon fabric is decolorized by the decolorization method of any one of claims 1 to 5, the colored waste liquid is collected, and the DMSO in the colored waste liquid is separated to obtain a concentrated colored waste liquid. Decamethylcyclopentasiloxane is added to the concentrated colored waste liquid to prepare a dye solution, and the pH value of the dye solution is adjusted to 3.5-5.5 before dyeing the nylon fabric.

7. A method for dyeing nylon fabric according to claim 6, characterized in that: The DMSO in the colored waste liquid was separated by vacuum distillation.

8. The method for dyeing nylon fabric according to claim 6, characterized in that: The content of concentrated colored waste liquid in the dye liquor is 1-5wt%; during dyeing, the bath ratio is 1:15-30, the temperature is raised to 95-99°C at a heating rate of 2-5°C / min and then kept warm for 1-2h.

9. The method for dyeing nylon fabric according to claim 6, characterized in that: After dyeing, the dye is fixed, soaped and washed with water in sequence.

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