Decoloration method of colored textile and implementation device

Abstract

The invention belongs to the technical field of decoloration and reutilization of textiles, and relates to a decoloration method for colored textiles and an implementation device. The decolorizing method comprises the following steps: adding a decolorizing solvent, a dye adsorption material and a colored textile into a closed device of which the bottom can be heated and is subjected to heat preservation treatment, the decolorizing solvent is positioned at the bottom of the closed device, and the dye adsorption material is positioned at the top of the closed device; the upper end of the colored textile is in contact with the dye adsorption material, and the lower end of the colored textile is not in contact with the decolorizing solvent, and heating to 39-69 DEG C below the boiling point of the decolorizing solvent for decolorizing. The implementation device comprises a decolorizing device, wherein the decolorizing device comprises a heating device, a sealing device, and a dye adsorption device and a clamp which are simultaneously positioned in the sealing device; the bottom of the sealing device can be heated; the heating device is used for heating the bottom of the sealing device. The method effectively solves the two problems of degradation or dissolution of textiles and re-pollution of a decolorizing solvent by a dye in the existing decolorizing technology.

Description

Technical Field

[0001] The invention belongs to the technical field of textile decolorization and reuse, and relates to a decolorization method and an implementation device for colored textiles. Background Art

[0002] With the processing, application and end of life cycle of a large number of chemical fibers, the environmental and ecological problems caused by the accumulation of waste textiles are becoming increasingly prominent. The realization of efficient and high-quality recycling of waste textiles faces several inevitable difficulties: first, textile materials are composed of multiple components with large structural differences, which require precise separation and recycling; second, the cost of separating dyes and chemicals is high, which has a great impact on quality; finally, the recycling path of waste textiles is complicated, the cost of recycled products is high, and the market acceptance is low. Among them, the decolorization of waste textiles is a key node both in the separation process and in the design of short-process efficient recycling paths, so it is particularly important to study the decolorization technology of waste textiles.

[0003] The purpose of decolorizing waste textiles is to remove the dyes (pigments) on the fabrics as much as possible without damaging the fabrics, so as to avoid the dyes affecting the regeneration process and the performance of the recycled materials. At present, the technology of using steam to decolorize textiles has become a research hotspot. These technologies generally use the vaporization of decolorizing solvents to form steam to decolorize textiles. The advantage is that steam can be continuously generated and fully contact with the textiles, achieving a deep and uninterrupted decolorization effect.

[0004] The document (Closed-loop utilization of polyester in the textile industry. Textile Progress, 2023.) uses boiling ethylene glycol steam to decolorize dyed polyester fibers for 30 minutes, and the decolorization rate reaches more than 97%. Ethylene glycol and dye can be separated by distillation and recycled. The patent with the authorization announcement number CN111607956B provides a decolorization method for polyester fibers colored with dyes, which extracts the dyes in the fibers by heating the alcohol ether solvent to continuously generate steam, and recycles the solvent to achieve decolorization. However, the aforementioned documents or patents heat the decolorization solvent to its boiling point during the decolorization process, which may cause the textile to degrade or dissolve, affecting the mechanical properties of the textile. In addition, the separated dyes often re-enter and contaminate the decolorization solvent below with the circulation of steam, which not only increases the cost of recycling and reusing the colored decolorization solvent in the later stage, but also may have an adverse effect on the decolorization effect. Summary of the invention

[0005] The purpose of the present invention is to solve the problems existing in the prior art and to provide a decolorization method and a decolorization device for colored textiles.

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

[0007] A method for decolorizing colored textiles comprises adding a decolorizing solvent, a dye adsorbing material and colored textiles into a closed device with a heatable bottom and subjected to heat preservation treatment, wherein the decolorizing solvent is located at the bottom of the closed device, the dye adsorbing material is located at the top of the closed device, the colored textiles are vertically suspended, the upper end is in contact with the dye adsorbing material and the lower end is not in contact with the decolorizing solvent, and the decolorizing is performed by heating to 39-69°C below the boiling point of the decolorizing solvent.

[0008] The present invention uses a closed device to decolorize the fabric, and controls the decolorization temperature to be 39-69°C below the boiling point of the decolorization solvent. In this temperature range, the saturated vapor pressure of the steam is small, that is, the concentration of the decolorization steam is low. At the same time, the closed device is heat-insulated so that the temperature of the space above the decolorization solvent inside the closed device remains consistent. Therefore, after the decolorization steam contacts the fabric, a very small amount of gas-liquid mixture is formed. The moisture absorption and moisture storage capacity of the fabric itself can be used to lock it without dripping due to gravity, thereby avoiding contamination of the clean decolorization solvent below. As the steam is gradually filled and circulated from bottom to top, the gas-liquid mixture tends to move upward and to both sides, and when it moves to contact the dye adsorption material, it is adsorbed by the dye adsorption material.

[0009] The decolorization temperature of the prior art is greater than or equal to the boiling point of the decolorization solvent, and the decolorization process is not carried out in a closed device, which will cause a large amount of decolorization steam to liquefy on the surface of the fabric. Under the action of gravity, a large amount of colored decolorization solvent drips into the clean decolorization solvent below to contaminate it.

[0010] As the preferred technical solution:

[0011] In the above-mentioned decolorization method for colored textiles, the dye in the colored textiles is a disperse dye or an acid dye.

[0012] As described above, a decolorization method for colored textiles, the decolorization object is colored nylon in the colored textiles, and the colored textiles are also subjected to alkali washing before decolorization, the alkali washing temperature is 60-80°C, the concentration of the alkali solution (such as NaOH solution) is 10-50g / L, the alkali washing time is 20-30min, and the decolorization solvent is dimethyl sulfoxide (DMSO, boiling point is 189°C); when the fiber material in the colored textile is only nylon or other fiber materials containing unbound dyes, decolorization can be directly carried out according to this condition. When the fiber material in the colored textile contains other fiber materials bound to dyes in addition to nylon, decolorization is first carried out according to this condition to separate the dye from the nylon, and then the conditions are changed for decolorization to separate the dye from other fiber materials.

[0013] In the prior art, steam decolorization is often limited by high decolorization temperature and long decolorization cycle. This is mainly due to the selection of traditional decolorization solvents, which usually have a high boiling point. In order to achieve an effective decolorization effect, it is usually necessary to heat it to the boiling point or higher. For some colored textiles, such as nylon, it needs to be dyed at high temperature (coloring above 98°C). Therefore, as the reverse process of dyeing, physical solvent decolorization also needs to be carried out under high temperature conditions to ensure fiber swelling and full opening of amorphous regions. In order to meet this high temperature condition, the decolorization solvent needs to have a high boiling point, otherwise it needs to be pressurized to reach the required decolorization temperature. However, the high boiling point decolorization solvents currently used (such as ethylene glycol, ethylene glycol methyl ether, acetic acid, etc.) are not good solvents for nylon. They rely more on high temperature and long decolorization cycle to achieve excellent decolorization effect.

[0014] The present invention adopts DMSO as a decolorization solvent, and DMSO is a good solvent for nylon. Experiments have shown that, compared with other solvents, at the same temperature and within the same decolorization time, DMSO can more fully swell nylon and open its amorphous region, thereby achieving a higher decolorization rate. Therefore, when DMSO is used as a decolorization solvent for the steam method, compared with existing decolorization solvents, it can reduce the decolorization temperature and shorten the decolorization cycle to a certain extent.

[0015] In the above-mentioned decolorization method for colored textiles, the dye adsorption material is a recycled cotton material, which needs to be compacted and filled in the dye adsorption device and needs to be replaced regularly, with a replacement cycle of 10-15 days.

[0016] In the decolorization method for colored textiles as described above, each colored textile is a strip bent into a U shape, with the bending part located at the lower end, which can further improve the efficiency of dye extraction and adsorption.

[0017] The decolorization method for colored textiles as described above has a decolorization time of 2-5 hours, and after decolorization, the decolorization rate of the colored textile calculated according to the K / S value is above 95%, the strength retention rate measured according to GB / T 3923.1-2013 is above 95%, and the whiteness measured according to GB / T 17644-2008 is 70-80.

[0018] The present invention also provides a device for implementing a decolorization method for colored textiles as described in any one of the above items, comprising a decolorization device, the decolorization device comprising a heating device, a sealing device, and a dye adsorption device and n clamps located in the sealing device, where n≥1;

[0019] The sealed device is heat-insulated and the bottom is heatable; the heating device is used to heat the bottom or the entire sealed device; the dye adsorption device and n clamps are all located on the top of the sealed device, the dye adsorption device is filled with dye adsorption material, the n clamps are used to clamp the colored textiles, and the n clamps are all connected to the dye adsorption device; the height of the clamp is 20-30mm, the width is 5-10mm, the length is 50-100cm, both sides are provided with through holes, and the distance between two adjacent clamps is 5-10cm.

[0020] As the preferred technical solution:

[0021] As described above, the sealing device is a cubic structure, including a left side plate, a right side plate, a front side plate, a rear side plate, a cover plate and a bottom plate, and both the left side plate and the right side plate have a lifting structure.

[0022] As described above, the implementation device has a total of m decolorization devices, m≥2; the m decolorization devices are arranged at intervals along the left and right directions; the implementation device also includes a horizontal conveyor belt, which passes through the m decolorization devices at the same time, and all the clamps are connected to the conveyor belt.

[0023] As described above, the decolorization device also includes a retractable baffle, which is horizontally arranged inside the closed device and below the dye adsorption device and the n clamps. When the cloth sample is replaced, the retractable baffle is controlled to be in an extended state to protect the bottom steam.

[0024] Beneficial effects:

[0025] (1) The present invention controls the bleaching temperature to 39-69°C below the boiling point of the bleaching solvent, thereby avoiding the problem of textile degradation or dissolution caused by high temperature. The saturated vapor pressure of steam in this temperature range is small, the concentration of bleaching steam is low, and the damage to the textile is minimal, thereby protecting the original structure and mechanical properties of the textile.

[0026] (2) The present invention places the decolorization process in a closed device and combines it with heat preservation treatment to ensure that the temperature of the space above the decolorization solvent inside the closed device remains consistent. This allows the gas-liquid mixture formed after the decolorization steam contacts the fabric to be locked by the moisture absorption and storage capacity of the fabric itself, rather than dripping due to gravity, thereby avoiding contamination of the clean decolorization solvent below.

[0027] (3) As the steam is gradually filled and circulated from bottom to top, the dye component in the gas-liquid mixture tends to move upward and to the sides. When it moves to contact the dye adsorption material, it is effectively adsorbed by the dye adsorption material, realizing efficient recovery of the dye. This not only improves the decolorization efficiency, but also reduces the cost of subsequent recovery and reuse of the colored decolorization solvent.

[0028] (4) In view of the limitations of the existing steam decolorization technology, such as high decolorization temperature or long decolorization cycle, the present invention uses DMSO as a decolorization solvent to achieve a more efficient and energy-saving decolorization effect.

[0029] (5) In the present invention, intermittent continuous decolorization of colored textiles can be achieved by only regularly replacing the adsorbent in the dye adsorption device and replenishing the decolorization solvent in the steam generator. The production efficiency is high and the decolorization cost is low, which has great application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 and Figure 2 is a schematic diagram of the structure of the decolorization device. Figure 1 For the main view, Figure 2 is a side view;

[0031] Figure 3 is a schematic diagram of a strip bent into a U-shape;

[0032] Among them, 1- conveyor belt, 2- clamp, 3- colored textile, 4- retractable baffle, 5- heating device, 6- sealing device. DETAILED DESCRIPTION

[0033] 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.

[0034] The following are the test methods for the relevant performance indicators in each embodiment and comparative example:

[0035] 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:

[0036] 00%;

[0037] Where: is the K / S value of the textile before bleaching, It is the K / S value of the textile after bleaching.

[0038] 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 for testing.

[0039] Whiteness: measured according to GB / T 17644-2008, the fabric was folded into 8 layers, and measured with a WSB-2 digital whiteness meter, and measured 5 times in parallel to take the average value.

[0040] The following embodiments are apparatus for implementing a method for decolorizing colored textiles, such as Figure 1 and Figure 2 As shown, it includes a decolorizing device and a horizontal conveyor belt 1;

[0041] There are m decolorization devices in total, m ≥ 2; m decolorization devices are arranged along the left and right directions (such as Figure 1 As shown, the arrow points to the right) spacing arrangement;

[0042] The decolorizing device comprises a heating device 5, a sealing device 6, a dye adsorption device, a clamp 2 and a retractable baffle 4;

[0043] The closed device 6 is a cubic structure, including a left side plate, a right side plate, a front side plate, a rear side plate, a cover plate and a bottom plate. Both the left side plate and the right side plate have a lifting structure. The volume of the closed device is 5.2m 3 (length × width × height = 400cm × 100cm × 130cm); the closed device 6 is heat-insulated (i.e., a layer of heat-insulating cotton is wrapped on its outside);

[0044] The heating device 5 is used to heat the bottom or the whole of the sealing device 6. Specifically, the heating device 5 can be an electric heating wire;

[0045] The number of the clamps 2 is n, n≥1; the height of the clamp 2 is 20-30 mm, the width is 5-10 mm, the length is 50-100 cm, both sides are provided with through holes, and the distance between two adjacent clamps 2 is 5-10 cm;

[0046] The dye adsorption device and the n clamps 2 are simultaneously located at the top of the closed device 6, and the n clamps 2 are all connected to the dye adsorption device;

[0047] The retractable baffle 4 is horizontally arranged inside the closed device 6 and below the dye adsorption device and the n clamps 2;

[0048] The conveyor belt 1 passes through m decolorizing devices at the same time, and all the clamps 2 are connected to the conveyor belt 1;

[0049] When the device is used to decolorize colored textiles 3, the dye adsorption material is compacted and filled in the dye adsorption device, the decolorization solvent is placed at the bottom of the closed device 6, and n colored textiles 3 are bent into U-shaped strips along the length direction (such as Figure 3As shown, the bend is located at the lower end) and are clamped on n clamps 2 respectively, and the colored textile 3 is kept vertically suspended, the upper end is in contact with the dye adsorbing material and the distance between the lower end and the decolorizing solvent liquid surface is maintained at 20 cm.

[0050] Example 1

[0051] A decolorization method for colored textiles, the specific steps are as follows:

[0052] (1) Preparation of raw materials;

[0053] Colored textiles: colored nylon, the manufacturer is Zhejiang Jiahua Special Nylon Co., Ltd., the product name is FDY fully drawn nylon, the serial number is 38, the specification is 70D / 48F, and the size (length × width) is 100cm × 60cm;

[0054] NaOH solution: concentration is 10g / L, solvent is water;

[0055] Decolorization solvent: DMSO;

[0056] Dye adsorption material: DENSORB general-purpose adsorption cotton, the manufacturer is De'an Environmental Protection Company;

[0057] (2) Alkaline washing treatment;

[0058] Alkaline washing treatment: Place the colored textile in a NaOH solution at 80°C for 30 minutes;

[0059] (3) Decolorization treatment;

[0060] Add decolorizing solvent, dye adsorbing material and colored textiles treated with alkali washing into the device, start the heating device in the device, heat the decolorizing solvent to a temperature of 120°C, and maintain it for 4 hours to complete the decolorization.

[0061] During the bleaching process, the retractable baffle is in a retracted state and the bleaching solvent is never contaminated; tests show that after bleaching, the bleaching rate of colored textiles is 95%, the strong retention rate is 98%, and the whiteness is 70.

[0062] Comparative Example 1

[0063] A method for decolorizing colored textiles, which differs from Example 1 only in that: in step (3), the decolorizing solvent is heated to 189°C.

[0064] Since colored nylon will dissolve in a large amount in a DMSO system above 160°C, and the temperature of the decolorization solvent in Comparative Example 1 is 189°C, the colored nylon gradually dissolves and enters the clean decolorization solvent below, causing pollution. After the decolorization is completed, the colored nylon is precipitated again in the form of blocks or powder without fiber form.

[0065] Comparative Example 2

[0066] A method for decolorizing colored textiles, which is different from Example 1 only in that the enclosed device has no cover plate.

[0067] The test shows that the decolorization rate of colored textiles after bleaching is 56% and the whiteness is 37.

[0068] Compared with Example 1, the decolorization rate and whiteness of the colored textile after decolorization in Comparative Example 2 are significantly reduced. This is because the top of the closed device is connected to the atmosphere and is no longer sealed. A large amount of decolorization steam will move upward with the pressure difference, and finally cool and liquefy at the dye adsorption device, and then return to the decolorization solvent at the bottom. Only a small amount of decolorization steam will stay on the surface of the fabric to react with it, resulting in a decrease in the decolorization rate and whiteness of the colored textile after decolorization.

[0069] Comparative Example 3

[0070] A method for decolorizing colored textiles, which is different from Example 1 only in that the closed device is not subjected to heat preservation treatment.

[0071] The test shows that the decolorization rate of colored textiles after bleaching is 86% and the whiteness is 56.

[0072] Compared with Example 1, the decolorization rate and whiteness of the colored textile after decolorization in Comparative Example 3 are significantly reduced. This is because when the closed device is not subjected to insulation treatment, on the one hand, the temperature conduction can only rely on the upward movement of the steam, which will form a certain temperature difference. Therefore, the steam concentration above the fabric is lower due to the lower temperature environment, which leads to the final decolorization effect above the fabric being poor; on the other hand, the saturated steam will liquefy on the cavity wall of the closed device, thereby weakening the concentration of the saturated steam, thereby affecting the decolorization rate to a certain extent, and a reduction in the decolorization rate will also lead to a reduction in whiteness.

[0073] Example 2

[0074] A decolorization method for colored textiles, the specific steps are as follows:

[0075] (1) Preparation of raw materials;

[0076] Colored textiles: colored nylon, the manufacturer is Zhejiang Jiahua Special Nylon Co., Ltd., the product name is FDY fully drawn nylon, the serial number is 38, the specification is 70D / 48F, and the size (length × width) is 100cm × 60cm;

[0077] NaOH solution: concentration is 30g / L, the solvent is water;

[0078] Decolorization solvent: DMSO;

[0079] Dye adsorption material: DENSORB general-purpose adsorption cotton, the manufacturer is De'an Environmental Protection Company;

[0080] (2) Alkaline washing treatment;

[0081] Alkaline washing treatment: Place the colored textile in a NaOH solution at 70°C for 25 minutes;

[0082] (3) Decolorization treatment;

[0083] Add decolorizing solvent, dye adsorbing material and colored textiles treated with alkali washing into the device, start the heating device in the device, heat the decolorizing solvent to a temperature of 135°C, and maintain it for 5 hours to complete the decolorization.

[0084] During the bleaching process, the retractable baffle is in a retracted state and the bleaching solvent is never contaminated; tests show that after bleaching, the bleaching rate of colored textiles is 99%, the strong retention rate is 95%, and the whiteness is 80.

[0085] Example 3

[0086] A decolorization method for colored textiles, the specific steps are as follows:

[0087] (1) Preparation of raw materials;

[0088] Colored textiles: colored nylon, the manufacturer is Zhejiang Jiahua Special Nylon Co., Ltd., the product name is FDY fully drawn nylon, the serial number is 38, the specification is 70D / 48F, and the size (length × width) is 100cm × 60cm;

[0089] NaOH solution: concentration is 50g / L, the solvent is water;

[0090] Decolorization solvent: DMSO;

[0091] Dye adsorption material: DENSORB general-purpose adsorption cotton, the manufacturer is De'an Environmental Protection Company;

[0092] (2) Alkaline washing treatment;

[0093] Alkaline washing treatment: Place the colored textile in a NaOH solution at 60°C for 20 minutes;

[0094] (3) Decolorization treatment;

[0095] Add decolorizing solvent, dye adsorbing material and colored textiles treated with alkali washing into the device, start the heating device in the device, heat the decolorizing solvent to a temperature of 150°C, and maintain it for 2 hours to complete the decolorization.

[0096] During the bleaching process, the retractable baffle is in a retracted state and the bleaching solvent is never contaminated; tests show that after bleaching, the bleaching rate of the colored textiles is 98%, the strong retention rate is 96%, and the whiteness is 76.

Claims

1. A method for decolorizing colored textiles, characterized in that: A decolorizing solvent, a dye adsorbing material and colored textiles are added into a closed device with a heatable bottom and heat-insulated treatment, wherein the decolorizing solvent is located at the bottom of the closed device, the dye adsorbing material is located at the top of the closed device, and the colored textiles are vertically hung with the upper end in contact with the dye adsorbing material and the lower end not in contact with the decolorizing solvent, and the decolorizing is performed by heating to 39-69°C below the boiling point of the decolorizing solvent.

2. The method for decolorizing a colored textile according to claim 1, characterized in that: Dyes in colored textiles are disperse dyes or acid dyes.

3. A method for decolorizing colored textiles according to claim 2, characterized in that: The bleaching object is the colored nylon in the colored textiles. Before bleaching, the colored textiles are also subjected to alkali washing treatment. The alkali washing temperature is 60-80°C, the alkali solution concentration is 10-50g / L, the alkali washing time is 20-30min, and the bleaching solvent is dimethyl sulfoxide.

4. The method for decolorizing a colored textile according to claim 1, characterized in that: The dye-absorbing material is recycled cotton.

5. The method for decolorizing a colored textile according to claim 1, characterized in that: Each colored textile is a strip bent into a U-shape, with the bend being located at the lower end.

6. The method for decolorizing colored textiles according to claim 1, characterized in that: The bleaching time is 2-5h. After bleaching, the bleaching rate of colored textiles calculated according to the K / S value is above 95%, the strength retention rate measured according to GB / T 3923.1-2013 is above 95%, and the whiteness measured according to GB / T 17644-2008 is 70-80.

7. A device for implementing a decolorization method for colored textiles according to any one of claims 1 to 6, characterized in that: The decolorizing device includes a heating device, a sealing device, a dye adsorption device and n clamps located in the sealing device, wherein n≥1; The sealed device is heat-insulated and has a heatable bottom; the heating device is used to heat the bottom or the entire sealed device; the dye adsorption device and n clamps are all located on the top of the sealed device, the dye adsorption device is filled with dye adsorption material, the n clamps are used to clamp colored textiles, and the n clamps are all connected to the dye adsorption device.

8. The implementation device according to claim 7, characterized in that: The sealing device is a cubic structure, comprising a left side plate, a right side plate, a front side plate, a rear side plate, a cover plate and a bottom plate, and both the left side plate and the right side plate have a lifting structure.

9. The implementation device according to claim 8, characterized in that: There are m decolorizing devices in total, m≥2; the m decolorizing devices are arranged at intervals in the left-right direction; the implementation device also includes a horizontal conveyor belt, the conveyor belt passes through the m decolorizing devices at the same time, and all the clamps are connected to the conveyor belt.

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