Regeneration method of waste polyester-cotton textile fabric

Abstract

The invention discloses a regeneration method of a waste polyester-cotton textile, and belongs to the technical field of waste textile regeneration, and the regeneration method comprises the following steps: treating the waste polyester-cotton textile in a sodium hydroxide aqueous solution containing hydrogen peroxide; then putting the obtained product into a hydrogen peroxide solution containing urea to be treated; and treating the obtained product in an acidic aqueous solution. The regeneration method is suitable for waste polyester cotton textiles dyed by reactive dyes, the problem of incomplete stripping in the prior art is solved, the cotton pulp which is high in whiteness, high in alpha cellulose content, low in iron ion content and free of polyester component residues is obtained, and the obtained cotton pulp can partially replace wood pulp to be used as a raw material of viscose or lyocell fibers.

Description

Technical Field

[0001] The invention belongs to the technical field of waste textile regeneration, and in particular relates to a method for regenerating waste polyester-cotton textiles. Background Art

[0002] my country has a huge amount of waste textiles generated and stored. Due to the lack of high-value recycling technology, the utilization rate of waste textiles is less than 20%. Polyester-cotton blended fabrics are one of the most common clothing fabrics. The resource recycling of polyester-cotton waste textiles can help reduce the consumption of petroleum resources and reduce carbon emissions.

[0003] Dissolving pulp is the raw material for preparing regenerated cellulose fibers such as viscose or lyocell. It is mainly prepared by purifying and decolorizing cellulose extracted from wood. Since polyester-cotton waste is rich in cotton cellulose, extracting cotton cellulose to prepare cotton pulp, which is used to replace wood pulp to prepare viscose or lyocell fibers, is one of the effective ways to achieve high-value utilization of polyester-cotton waste.

[0004] At present, the process for waste regeneration generally involves alkali treatment, acid treatment, and oxidative bleaching. For example, the Chinese invention patent with publication number CN115003879A discloses a method for separating cellulose fibers and non-cellulose fibers from a mixed fiber textile material containing cellulose fibers and non-cellulose fibers, comprising the following steps: mechanically decomposing the textile material by cutting, grinding, grinding or milling, and then contacting with an acid at a temperature in the range of 50-100°C for 30-240 minutes, and then contacting with an alkali at a temperature in the range of 50-200°C for 30-240 minutes. The obtained product after the acid and alkali contact can be further chemically bleached using ozone and hydrogen peroxide / peracetic acid bleaching series, or further reacted with urea at 100-170°C. These methods have a good regeneration effect when used to treat indigo-dyed polyester-cotton denim, and can obtain cotton pulp with high whiteness. However, when used to treat polyester-cotton blended fabrics dyed with reactive dyes, the treatment effect is poor. The obtained cotton pulp cannot be used in many downstream fields due to incomplete stripping and low whiteness. For example, it cannot be used to replace wood pulp to prepare viscose or lyocell fibers. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for regenerating high-whiteness cotton pulp from waste polyester-cotton textiles dyed with reactive dyes.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for regenerating waste polyester-cotton textiles, comprising the following steps: S1. treating the waste polyester-cotton textile in an aqueous sodium hydroxide solution containing hydrogen peroxide; S2, treating the product obtained in S1 in a hydrogen peroxide solution containing urea; S3, treating the product obtained in S2 in an acidic aqueous solution.

[0007] The beneficial effects of the present invention are as follows: the method provided by the present invention can realize the complete stripping of polyester-cotton fabric dyed with reactive dyes by sequentially performing an alkali treatment containing hydrogen peroxide, a bleaching treatment containing urea and an acid treatment, so as to obtain white, high-purity cotton pulp, the whiteness of the obtained cotton pulp can reach 70% or more, the type A cellulose content reaches 95% or more, the iron ion content is below 15ppm, the polymerization degree is 500-800, and the obtained cotton pulp has no polyester component residue, can partially replace wood pulp as a raw material for viscose or lyocell fiber, prepare high-quality recycled products, and effectively realize the efficient regeneration of waste textiles. DETAILED DESCRIPTION

[0008] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in conjunction with the implementation methods.

[0009] The method for regenerating waste polyester-cotton textiles comprises the following steps: S1. Alkali treatment: treating the waste polyester-cotton textile in an aqueous sodium hydroxide solution containing hydrogen peroxide; S2, bleaching treatment: placing the product obtained in S1 in a hydrogen peroxide solution containing urea for treatment; S3. Acid treatment: The product obtained in S2 is treated in an acidic aqueous solution.

[0010] From the above description, it can be seen that the beneficial effect of the present invention is that for polyester-cotton blended fabrics dyed with reactive dyes, the traditional alkali treatment and hydrogen peroxide bleaching and decolorization treatment cannot effectively remove the dyes on the cotton fibers, resulting in low whiteness of the prepared cotton pulp, which limits downstream applications. The method provided by the invention comprises the following steps: firstly, an aqueous sodium hydroxide solution containing hydrogen peroxide is used for alkali treatment; hydrogen peroxide is added in the alkali treatment process; the obtained raw pulp has high whiteness and is easy to bleach, thereby reducing the pressure of the subsequent oxidation decolorization process; then, in the bleaching treatment stage, the temperature of the traditional hydrogen peroxide bleaching of 60-100 DEG C is increased to 130-170 DEG C; urea is added at the same time; at the treatment temperature, urea will decompose isocyanic acid; the isocyanic acid will not only react with the hydroxyl groups on the cellulose molecular chain to generate cellulose, but also destroy the chemical bonding between the dye and the cellulose molecular chain, thereby greatly improving the oxidation decolorization effect of cotton cellulose and improving the whiteness of the obtained cotton pulp; finally, an acid treatment is performed with an acidic aqueous solution to remove metal ions; at the same time, a small amount of carbamate groups formed on the main chain of the cellulose molecule will be decomposed and removed, and the molecular structure of cellulose will be restored, thereby obtaining cotton pulp with a polymerization degree of 500-800, a whiteness of ≥70%, a cellulose alpha content of ≥95%, an iron ion content of ≤15 ppm, and no residual polyester component. In the whole treatment process of the present invention, the order of the steps is crucial and they must be performed in sequence. For example, acid treatment followed by alkali treatment as in the Chinese invention patent with publication number CN115003879A may result in incomplete dye removal and destruction of the cellulose molecular structure.

[0011] Furthermore, the waste polyester-cotton textile fabric is polyester-cotton fabric dyed with reactive dyes.

[0012] From the above description, it can be seen that the method provided by the present invention has a good treatment effect on polyester-cotton fabrics dyed with reactive dyes, and can also be used for polyester-cotton fabrics dyed with indigo dyes, and also has a good treatment effect.

[0013] Furthermore, the treatment temperature in S1 is 130-180° C., preferably 140-160° C., the treatment time is 1-5 h, preferably 1-3 h, the concentration of sodium hydroxide in the sodium hydroxide aqueous solution containing hydrogen peroxide is 5-10 wt %, and the concentration of hydrogen peroxide is 0.1-0.5 wt %.

[0014] From the above description, it can be seen that selecting an appropriate alkali treatment process can ensure the removal of part of the dye while avoiding polyester residues, while retaining more methyl cellulose.

[0015] Furthermore, the treatment temperature in S2 is 130-170°C, preferably 130-150°C, the treatment time is 0.5-3h, preferably 1-2h, and the H 2 O 2The concentration of hydrogen peroxide is 0.1-0.5wt%, the concentration of urea is 1-5wt%, and the pH of the hydrogen peroxide solution containing urea is 9-12.

[0016] From the above description, it can be seen that the addition of urea to the hydrogen peroxide solution is crucial. Compared with using them separately, directly adding urea to hydrogen peroxide can play a synergistic role and obtain cotton pulp with higher whiteness.

[0017] Furthermore, the treatment temperature in S3 is 30-50° C., the treatment time is 30-40 min, and the pH value of the acidic aqueous solution is less than or equal to 2.

[0018] From the above description, it can be seen that during acid treatment, the pH of the treatment liquid should be controlled in a lower range and a higher temperature should be maintained to avoid too many residual metal ions, such as iron ions; at the same time, excessively high temperatures should be avoided to cause degradation of cotton fibers, resulting in the problem of substandard polymerization degree.

[0019] The treatments mentioned in the present invention are all immersion in a solution or immersion in a solution under stirring conditions, and solid-liquid separation is performed after immersion, the liquid part of the previous step is removed and the solid part is collected for the next step of treatment. Whether to stir and the stirring rate are not particularly required, and the main function is to ensure that the object to be treated can be fully immersed in the solution, which can be selected and adjusted according to the actual production conditions and the amount of the object to be treated.

[0020] Embodiment 1 of the present invention is: The method for regenerating waste polyester-cotton textiles comprises the following steps: S1. Add 10g each of blue, red and military green polyester-cotton blended fabrics into the reactor; Among them, the polyester in the polyester-cotton fabric is dyed with disperse dyes, and the cotton is dyed with reactive dyes. The cotton content is 65%, the polyester content is 35%, and the woven fabric has a gram weight of 160 g / m 2 ; S2, add 600g of sodium hydroxide aqueous solution containing hydrogen peroxide into the reactor, and treat at 150°C for 1.5h; The concentration of NaOH in the sodium hydroxide aqueous solution containing hydrogen peroxide is 5 wt%, H 2 O 2 The concentration is 0.2 wt%; S3, take 15 g of the product obtained in S2, add it to 450 g of a hydrogen peroxide solution containing urea, and treat at 150° C. for 1 h; Among them, H 2 O 2 The concentration was 0.15 wt %, the urea concentration was 1 wt %, and the pH was adjusted to 11 with NaOH; S4. Take the product obtained in S3, add it into a sulfuric acid aqueous solution with a pH of 2, and treat it at 40°C for 30 minutes.

[0021] Embodiment 2 of the present invention is: The method for regenerating waste polyester-cotton textiles comprises the following steps: S1. Add 10g each of blue, red and military green polyester-cotton blended fabrics into the reactor; Among them, the polyester in the polyester-cotton fabric is dyed with disperse dyes, and the cotton is dyed with reactive dyes. The cotton content is 65%, the polyester content is 35%, and the woven fabric has a gram weight of 160 g / m 2 ; S2, add 600g of sodium hydroxide aqueous solution containing hydrogen peroxide into the reactor, and treat at 150°C for 1.5h; The concentration of NaOH in the sodium hydroxide aqueous solution containing hydrogen peroxide is 10 wt%, H 2 O 2 The concentration is 0.5 wt%; S3, take 15 g of the product obtained in S2, add it to 450 g of a hydrogen peroxide solution containing urea, and treat at 130° C. for 1 h; Among them, H 2 O 2 The concentration was 0.1 wt %, the urea concentration was 5 wt %, and the pH was adjusted to 11 with NaOH; S4. Take the product obtained in S3, add it into a sulfuric acid aqueous solution with a pH of 2, and treat it at 40°C for 30 minutes.

[0022] Embodiment 3 of the present invention is: The method for regenerating waste polyester-cotton textiles comprises the following steps: S1. Add 10g each of blue, red and military green polyester-cotton blended fabrics into the reactor; Among them, the polyester in the polyester-cotton fabric is dyed with disperse dyes, and the cotton is dyed with reactive dyes. The cotton content is 65%, the polyester content is 35%, and the woven fabric has a gram weight of 160 g / m 2 ; S2, add 600g of sodium hydroxide aqueous solution containing hydrogen peroxide into the reactor, and treat at 150°C for 1.5h; The concentration of NaOH in the sodium hydroxide aqueous solution containing hydrogen peroxide is 5 wt%, H 2 O 2 The concentration is 0.1 wt%; S3, take 15 g of the product obtained in S2, add it to 450 g of a hydrogen peroxide solution containing urea, and treat at 150° C. for 1 h; Among them, H 2 O2 The concentration was 0.5 wt %, the urea concentration was 1 wt %, and the pH was adjusted to 11 with NaOH; S4. Take the product obtained in S3, add it into a sulfuric acid aqueous solution with a pH of 2, and treat it at 40°C for 30 minutes.

[0023] Embodiment 4 of the present invention is: The method for regenerating waste polyester-cotton textiles comprises the following steps: S1. Add 10g each of blue, red and military green polyester-cotton blended fabrics into the reactor; Among them, the polyester in the polyester-cotton fabric is dyed with disperse dyes, and the cotton is dyed with reactive dyes. The cotton content is 65%, the polyester content is 35%, and the woven fabric has a gram weight of 160 g / m 2 ; S2, add 600g of sodium hydroxide aqueous solution containing hydrogen peroxide into the reactor and treat at 140°C for 3h; The concentration of NaOH in the sodium hydroxide aqueous solution containing hydrogen peroxide is 6 wt%, H 2 O 2 The concentration is 0.3 wt%; S3, take 15 g of the product obtained in S2, add it to 450 g of a hydrogen peroxide solution containing urea, and treat at 140° C. for 2 h; Among them, H 2 O 2 The concentration was 0.2 wt %, the urea concentration was 2.5 wt %, and the pH was adjusted to 9 with NaOH; S4. Take the product obtained in S3, add it into a sulfuric acid aqueous solution with a pH of 2, and treat it at 35° C. for 30 minutes.

[0024] Embodiment 5 of the present invention is: The method for regenerating waste polyester-cotton textiles comprises the following steps: S1. Add 10g each of blue, red and military green polyester-cotton blended fabrics into the reactor; Among them, the polyester in the polyester-cotton fabric is dyed with disperse dyes, and the cotton is dyed with reactive dyes. The cotton content is 65%, the polyester content is 35%, and the woven fabric has a gram weight of 160 g / m 2 ; S2, add 600g of sodium hydroxide aqueous solution containing hydrogen peroxide into the reactor, and treat at 155°C for 2.5h; The concentration of NaOH in the sodium hydroxide aqueous solution containing hydrogen peroxide is 7wt%, H 2 O 2 The concentration is 0.4 wt%; S3, take 15 g of the product obtained in S2, add it to 450 g of a hydrogen peroxide solution containing urea, and treat at 135°C for 1.5 h; Among them, H 2 O 2 concentration was 0.4 wt %, urea concentration was 3 wt %, and pH was adjusted to 10 with NaOH; S4. Take the product obtained in S3, add it to a sulfuric acid aqueous solution with a pH of 1.5, and treat it at 50°C for 35 minutes.

[0025] Embodiment 6 of the present invention is: The method for regenerating waste polyester-cotton textiles comprises the following steps: S1. Add 10g each of blue, red and military green polyester-cotton blended fabrics into the reactor; Among them, the polyester in the polyester-cotton fabric is dyed with disperse dyes, and the cotton is dyed with reactive dyes. The cotton content is 65%, the polyester content is 35%, and the woven fabric has a gram weight of 160 g / m 2 ; S2, add 600g of sodium hydroxide aqueous solution containing hydrogen peroxide into the reactor and treat at 160°C for 1h; The concentration of NaOH in the sodium hydroxide aqueous solution containing hydrogen peroxide is 8 wt%, H 2 O 2 The concentration is 0.5 wt%; S3, take 15 g of the product obtained in S2, add it to 450 g of a hydrogen peroxide solution containing urea, and treat at 145°C for 1 h; Among them, H 2 O 2 The concentration was 0.3 wt %, the urea concentration was 3.5 wt %, and the pH was adjusted to 12 with NaOH; S4. Take the product obtained in S3, add it to a sulfuric acid aqueous solution with a pH of 1, and treat it at 30°C for 40 minutes.

[0026] Embodiment 7 of the present invention is: The method for regenerating waste polyester-cotton textiles comprises the following steps: S1. Add 10g each of blue, red and military green polyester-cotton blended fabrics into the reactor; Among them, the polyester in the polyester-cotton fabric is dyed with disperse dyes, and the cotton is dyed with reactive dyes. The cotton content is 65%, the polyester content is 35%, and the woven fabric has a gram weight of 160 g / m 2 ; S2, add 600g of sodium hydroxide aqueous solution containing hydrogen peroxide into the reactor and treat at 130°C for 5h; The concentration of NaOH in the sodium hydroxide aqueous solution containing hydrogen peroxide is 5 wt%, H 2 O 2 The concentration is 0.2 wt%; S3, take 15 g of the product obtained in S2, add it to 450 g of a hydrogen peroxide solution containing urea, and treat at 135°C for 3 h; Among them, H 2 O 2 The concentration was 0.15 wt %, the urea concentration was 1 wt %, and the pH was adjusted to 11 with NaOH; S4. Take the product obtained in S3, add it into a sulfuric acid aqueous solution with a pH of 2, and treat it at 40°C for 30 minutes.

[0027] Embodiment 8 of the present invention is: The method for regenerating waste polyester-cotton textiles comprises the following steps: S1. Add 10g each of blue, red and military green polyester-cotton blended fabrics into the reactor; Among them, the polyester in the polyester-cotton fabric is dyed with disperse dyes, and the cotton is dyed with reactive dyes. The cotton content is 65%, the polyester content is 35%, and the woven fabric has a gram weight of 160 g / m 2 ; S2, add 600g of sodium hydroxide aqueous solution containing hydrogen peroxide into the reactor and treat at 180°C for 1h; The concentration of NaOH in the sodium hydroxide aqueous solution containing hydrogen peroxide is 5 wt%, H 2 O 2 The concentration is 0.2 wt%; S3, take 15 g of the product obtained in S2, add it to 450 g of a hydrogen peroxide solution containing urea, and treat at 170°C for 0.5 h; Among them, H 2 O 2 The concentration was 0.15 wt %, the urea concentration was 1 wt %, and the pH was adjusted to 11 with NaOH; S4. Take the product obtained in S3, add it into a sulfuric acid aqueous solution with a pH of 2, and treat it at 40°C for 30 minutes.

[0028] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the NaOH concentration in S2 is 3 wt %.

[0029] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that the concentration of NaOH in S2 is 12 wt %, and the concentration of H 2 O 2 The concentration is 0.6wt%.

[0030] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that the treatment temperature in S3 is 120°C.

[0031] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that no urea is added to the treatment liquid of S3.

[0032] Comparative Example 5: The difference between Comparative Example 5 and Example 1 is that the pH of the aqueous sulfuric acid solution in S4 is 3.

[0033] Comparative Example 6: The difference between Comparative Example 6 and Example 1 is that the acid treatment of S3 is performed first, and then the alkali treatment of S1 and the bleaching treatment of S2 are performed in sequence.

[0034] Comparative Example 7: The method for regenerating waste polyester-cotton textiles comprises the following steps: S1. Add 10g each of blue, red and military green polyester-cotton blended fabrics into the reactor; Among them, the polyester in the polyester-cotton fabric is dyed with disperse dyes, and the cotton is dyed with reactive dyes. The cotton content is 65%, the polyester content is 35%, and the woven fabric has a gram weight of 160 g / m 2 ; S2, add 600g of sodium hydroxide aqueous solution containing hydrogen peroxide into the reactor, and treat at 150°C for 1.5h; The concentration of NaOH in the sodium hydroxide aqueous solution containing hydrogen peroxide is 5 wt%, H 2 O 2 The concentration is 0.2 wt%; S3, take 15g of the product obtained in S2, add it to 450g of hydrogen peroxide solution, and treat it at 150°C for 1h; Among them, H 2 O 2 The concentration was 0.15 wt%, and the pH was adjusted to 11 with NaOH; S4, taking the product obtained in S3, adding it to a urea solution with a urea concentration of 1%, and treating it at 150°C for 1h; S5. Take the product obtained in S4, add it into a sulfuric acid aqueous solution with a pH of 2, and treat it at 40° C. for 30 minutes.

[0035] The physical properties of the cotton pulp obtained in Examples 1 to 3 and Comparative Examples 1 to 6 were tested, and the results are shown in Table 1. The whiteness was tested in accordance with "FZ / T 50010.7-1998 Pulp for viscose fibers - Determination of whiteness"; the degree of polymerization was tested in accordance with "FZ / T 50010.3-2011 Pulp for viscose fibers - Determination of viscosity"; the alpha cellulose content was tested in accordance with "FZ / T 50010.4-2011 Pulp for viscose fibers - Determination of alpha cellulose content"; the polyester residue was confirmed based on the infrared spectrum of the pulp, and the molecular structure of the polyester fiber contained a carbonyl absorption peak at 1720 cm -1 The cellulose in cotton fiber has no absorption peak here. Therefore, according to the infrared spectrum of cotton pulp, the absorption peak at 1720 cm -1 Check whether there is an absorption peak at the location to confirm whether there is any polyester residue.

[0036] Table 1

[0037] In summary, the method for regenerating cotton pulp using waste textiles provided by the present invention can treat polyester-cotton blended fabrics dyed with reactive dyes and obtain good treatment effects. The waste polyester-cotton blended fabrics treated by the regeneration method of the present invention can be recycled to obtain cotton pulp with high whiteness (≥73%), high type A cellulose content (≥95%), low iron ion content (≤15ppm) and no polymer residue. The cotton pulp can replace wood pulp as the raw material of viscose or lyocell fiber, effectively reducing resource waste and environmental pollution, and reducing the exploitation of primary resources. It is not only of great significance to environmental protection and resource conservation, but also has a positive role in promoting economic development, technological innovation and market demand.

[0038] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention specification, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for regenerating waste polyester-cotton textiles, characterized in that: The following steps are involved: S1. treating the waste polyester-cotton textile in an aqueous sodium hydroxide solution containing hydrogen peroxide; S2, treating the product obtained in S1 in a hydrogen peroxide solution containing urea; S3, treating the product obtained in S2 in an acidic aqueous solution.

2. The method for regenerating waste polyester-cotton textiles according to claim 1, characterized in that: The treatment temperature in S1 is 130~180℃.

3. The method for regenerating waste polyester-cotton textiles according to claim 1, characterized in that: The processing time in S1 is 1~5h.

4. The method for regenerating waste polyester-cotton textiles according to claim 1, characterized in that: The concentration of sodium hydroxide in the sodium hydroxide aqueous solution containing hydrogen peroxide is 5-10 wt %, and the concentration of hydrogen peroxide is 0.1-0.5 wt %.

5. The method for regenerating waste polyester-cotton textiles according to claim 1, characterized in that: The treatment temperature in S2 is 130~170℃.

6. The method for regenerating waste polyester-cotton textiles according to claim 1, characterized in that: The processing time in S2 is 0.5~3h.

7. The method for regenerating waste polyester-cotton textiles according to claim 1, characterized in that: The concentration of hydrogen peroxide in the urea-containing hydrogen peroxide solution is 0.1-0.5 wt %, and the concentration of urea is 1-5 wt %.

8. The method for regenerating waste polyester-cotton textiles according to claim 1, characterized in that: The treatment temperature in S3 is 30~50℃.

9. The method for regenerating waste polyester-cotton textiles according to claim 1, characterized in that: The processing time in S3 is 30~40min.

10. The method for regenerating waste polyester-cotton textiles according to claim 1, characterized in that: The pH value of the acidic aqueous solution is less than or equal to 2.

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