TWI854184B - Disposal method for waste fabric containing polyester, nylon and dye - Google Patents

Abstract

A disposal method for waste fabric containing polyester, nylon and dye includes the following steps: step (a): providing a waste fabric containing polyester, nylon and dye; and step (b): performing a first-stage treatment including acid treatment on the waste fabric to obtain a first liquid material and a first solid material. The first-stage treatment includes acid treatment with an acid solution mixed with an oxidant. The first solid material includes recycled polyester, and/or the first liquid material includes recycled nylon or degraded nylon.

Description

Treatment of waste fabrics containing polyester, nylon and dyes

The present invention relates to a method for treating waste fabrics, and in particular to a method for treating waste fabrics containing polyester, nylon and dyes.

Polyester fiber fabrics or nylon fiber fabrics are widely used in the market or in daily life. For example, polyester fiber can be co-woven with nylon fiber, and then a variety of hats, clothes, pants, skirts, socks and other fabrics can be made by the common methods in the textile industry or garment industry. Therefore, how to recycle the polyester and/or nylon in these co-woven fabrics and/or treat the waste containing polyester has become a current research topic.

The present invention provides a method for treating waste fabrics containing polyester, nylon and dyes, which can reduce the overall usage of acid and/or increase the amount or quality of recycled polyester and/or nylon.

The method for treating waste fabrics containing polyester, nylon and dyes of the present invention comprises the following steps. Step a: providing waste fabrics containing polyester, nylon and dyes. Step b: subjecting the waste fabrics to a first-stage treatment including acid treatment to obtain a first liquid and a first solid. The first-stage treatment includes acid treatment with an acid solution mixed with an oxidant. The first solid contains recycled polyester, and/or the first liquid contains recycled nylon or degraded nylon.

The present invention found that in an acidic environment, the decolorization function of the oxidant can be enhanced, including the physical removal of the dye from the fiber and the removal of the chromophore, thereby improving the hue quality of the recycled fiber and enhancing the economic value of recycling and reuse.

Based on the above, through the above steps, the method for treating waste fabrics containing polyester, nylon and dyes of the present invention can reduce the overall usage of acid solution and/or increase the recovery amount or quality of nylon and/or polyester.

Figure 1 is a partial schematic diagram of a method for treating waste containing polyester and nylon according to an embodiment of the present invention.

In the following detailed description, for the purpose of illustration and not limitation, exemplary embodiments that disclose specific details are described to provide a thorough understanding of the various principles of the present invention. However, it will be apparent to one of ordinary skill in the art that, with the benefit of this disclosure, the present invention may be practiced in other embodiments that depart from the specific details disclosed herein. In addition, descriptions of well-known devices, methods, and materials may be omitted to avoid obscuring the description of the various principles of the present invention.

Ranges may be expressed herein as from "about" one particular value to "about" another particular value, which may also be expressed directly as one particular value and/or to another particular value. When expressing the range, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when a value is expressed as an approximation by using the antecedent "about," it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each range may be expressly related or independent of the other endpoint.

In this document, non-limiting terms (such as: may, can, for example, or other similar terms) refer to non-essential or optional implementation, inclusion, addition, or existence.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention belongs. It will also be understood that terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning consistent with that in the relevant technical context and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[Recyclables]

Provides recycled materials containing polyester, nylon and dyes.

In one embodiment, the method of obtaining recyclables includes, for example, collecting various types of recyclables or waste containing nylon and polyester; the recyclables can be classified according to the type, color and/or purpose of use. The recyclables can include clothing, but the present invention is not limited to this. The fiber composition used in the clothing will be indicated on the regular clothing label.

In one embodiment, the recyclables containing nylon and polyester can be further subjected to one of the following pre-treatments (i.e., treatment before subsequent treatment; still recyclables in essence): removing objects on the recyclables (such as clips, fasteners, accessories, labels and/or other items that are obviously not nylon or polyester); performing preliminary cleaning on the recyclables (such as washing stains, shaking off impurities, etc., but not limited to); reducing the single size of the recyclables by physical means (such as cutting, trimming, slicing or dicing, but not limited to); and/or drying the recyclables.

In one embodiment, the method of obtaining recyclables may also include, for example, directly purchasing processed recyclables containing nylon and polyester (such as, but not limited to, recycled old clothes).

It should be noted that the term "nylon" in this article includes polymers commonly referred to as nylon, such as: Nylon 66, Nylon 6, Nylon 510, Nylon 1,6, other similar polymers including polyamide functional groups and similar to the aforementioned polymers, the aforementioned copolymers or the aforementioned interwoven fabrics.

It should be noted that the term "polyester" in this article includes polymers commonly referred to as polyesters, especially aromatic polyesters, and here specifically refers to polyesters derived from terephthalic acid (purified terephthalic acid; PTA) and ethylene glycol (ethylene glycol; EG) (i.e., polyethylene terephthalate (PET)).

In addition, the polyester in this article may also be, for example, poly(trimethylene terephthalate), poly(butylene terephthalate), polyethylene naphthalate, or a combination thereof. In this embodiment, the polyester is preferably polyethylene terephthalate, poly(trimethylene terephthalate), or a combination thereof. In addition, copolymers may also be used, which specifically refer to copolymers obtained by using two or more dicarboxylic acids and/or two or more diol components.

In one embodiment, the dyes used for fabrics are mostly organic dyes. For example, azo dyes (such as monoazo dyes or disazo dyes) are commonly used for dyeing nylon or polyester. Organic dyes usually have better adhesion to polymers. It is worth noting that the present invention does not limit the type of organic dyes.

In one embodiment, the dye used for the fabric does not include inorganic dyes. Most inorganic dyes contain heavy metal elements, which may be more likely to cause allergies or discomfort to the human body.

[First stage processing]

The aforementioned recyclables are subjected to the first stage of processing to obtain a first liquid and a first solid.

It should be noted that the term "liquid" in this article is not limited to the object being completely liquid. For example, "liquid" may include liquid; and suspended matter suspended in or on the liquid. The particle size of the suspended matter may be less than or equal to 1 millimeter (mm); or, according to the ASTM E11-01 standard, the suspended matter may pass through a sieve with a mesh number of 18 or more. For another example, "liquid" may include polymer colloid or other similar colloids.

It should be noted that the term "solid" in this article is not limited to the object being completely solid. For example, a "solid" may include a solid; and a liquid attached to the solid or located between two solids by capillary phenomena. The "solid" can be dried by appropriate means (such as heating drying and/or pressure reduction drying) to obtain a solid that is almost free of liquid. Based on the total weight of the "solid", the weight of the solid after drying can be about 80% or more; preferably about 90% or more; and more preferably about 95% or more.

In this embodiment, the first stage of treatment may include immersing the recyclate in an acid solution (which may be referred to as pickling or acid treatment). For example, the recyclate may be immersed in an acid solution mixed with an oxidant; or, the recyclate may be immersed in an acid solution, and then the oxidant may be mixed therein. Thereafter, the first liquid and the first solid may be separated from each other by an appropriate method (such as filtering with a sieve, but not limited thereto).

In one embodiment, in the first stage of treatment, the weight ratio of the recyclate to the acid solution mixed with the oxidant (i.e., the weight of the recyclate: the weight of the acid solution mixed with the oxidant) can be about 1:8~1:30. Preferably, in the first stage of treatment, the weight ratio of the recyclate to the acid solution mixed with the oxidant can be about 1:10~1:15.

In one embodiment, the acid treatment of the first stage of treatment can immerse the recyclate in an acid solution mixed with an oxidant and heat it to about 80°C~150°C. Preferably, it can be heated to about 90°C~140°C, which is higher than the glass transition temperature of polyester. If the heating temperature is too low (e.g., less than 80°C), the production capacity utilization rate may be poor due to the slow reaction. If the heating temperature is too high (e.g., greater than 150°C), the decomposition or decolorization of organic dyes may be poor (e.g., too much oxidant produces self-oxidation-reduction reaction), and/or there may be concerns about industrial safety.

In one embodiment, the acid treatment of the first stage of treatment can be performed by immersing the recyclate in an acid solution mixed with an oxidant and stirring and/or standing for about 1 hour or more. Preferably, stirring and/or standing for about 1 hour to 9 hours. More preferably, stirring and/or standing for about 2 hours or more. More preferably, stirring and/or standing for about 2 hours to 8 hours.

In one embodiment, the acid treatment in the first stage of treatment can be performed by immersing the recyclable material in an acid solution mixed with an oxidant and heating it (the heating temperature can be as described above); and, during the heating process, stirring and/or standing still (the stirring and/or standing still time can be as described above).

In one embodiment, the acid treatment of the first stage treatment can be performed by an aqueous solution of an organic acid. If nitric acid, hydrochloric acid or sulfuric acid is used, it is easy to cause damage to the acid treatment tank (such as: pickling tank; but not limited) or other possible metal tools (such as: stainless steel tools; but not limited). The mixture of nitric acid and oxidizing agent is easy to cause industrial safety hazards. Hydrochloric acid is easy to produce hydrogen chloride gas after heating (such as: above 80°C). Sulfuric acid may cause other non-nylon fibers (such as: polyester fibers) to dissolve, resulting in reduced separation between liquid and solid. Hydrofluoric acid is more likely to cause industrial safety hazards. Oxalic acid has a low water solubility (such as: about 14.3g/100ml@25°C), so it is difficult to prepare a high-concentration aqueous solution at room temperature to dissolve nylon. Phosphoric acid has poor solubility in nylon.

In one embodiment, the acid treatment of the first stage treatment can be performed by an aqueous solution of a fatty acid. Aromatic acids (such as, but not limited to, benzoic acid) have low water solubility and are therefore difficult to prepare into high-concentration aqueous solutions at room temperature to dissolve nylon. Moreover, compared to nylon, other non-nylon fibers (such as polyester fibers or other polymers containing aromatic groups) may be more difficult to be dissolved by fatty acids.

In one embodiment, the acid treatment of the first stage treatment can be performed by an aqueous solution of a straight chain fatty acid. Compared with fatty acids with the same carbon number, straight chain fatty acids can generally have better water solubility than side chain fatty acids.

In one embodiment, the acid treatment of the first stage treatment can be performed by an aqueous solution of a straight chain fatty acid with a carbon number of 3 or less. The straight chain fatty acid with a carbon number of 3 or less can have better water solubility.

In one embodiment, the acid treatment of the first stage of treatment can be performed by an aqueous solution of formic acid (i.e., ant acid; secreted by ants, bees and other hymenoptera) or acetic acid (i.e., acetic acid; produced by acetic acid bacteria). Formic acid and acetic acid are biological acids found in nature and are more eco-friendly in application and/or treatment (such as, but not limited to, wastewater treatment).

In one embodiment, the acid treatment of the first stage treatment can be performed by an aqueous solution of formic acid. Compared with acetic acid, formic acid dissolves nylon more easily.

In one embodiment, in the acid solution mixed with the oxidant, the acid concentration is about 20wt% (weight percentage) to 95wt% based on the entire acid solution mixed with the oxidant. Preferably, the acid concentration is about 30wt% to 90wt% based on the entire acid solution mixed with the oxidant.

In one embodiment, in the acid treatment of the first stage treatment, the oxidant used is an inorganic oxidant. The inorganic oxidant may include hydrogen peroxide, chlorate (such as sodium chlorate or calcium chlorate), hypochlorite (such as calcium hypochlorite or sodium hypochlorite), perchlorate, nitric acid, nitrate, perborate (such as sodium perborate), permanganate (such as potassium permanganate), dichromate (such as sodium dichromate) or a combination thereof.

In one embodiment, in the acid treatment of the first stage, the inorganic oxidant used includes hydrogen peroxide or hypochlorite. The reduction product of hydrogen peroxide is usually water, oxygen or hydroxide. The reduction product of hypochlorite can usually be chlorine ions. Hydrogen peroxide or hypochlorite is more eco-friendly in application and/or treatment (such as waste liquid or waste gas treatment, but not limited to).

In one embodiment, the oxidant is suitable for oxidizing the organic dye in an acidic environment, thereby decomposing or decolorizing it. Therefore, the acid solution containing the oxidant can have both separation and decolorization effects on polyester-nylon blended fabrics containing dyes. In other words, compared with the method of "first dissolving or degrading nylon with a solvent without an oxidant, and then removing the dye for decolorization (such as using an oxidant) after separating the polyester-nylon", this embodiment or a method similar to the embodiment can further improve the recycling quality of polyester and nylon, and can enhance their recycling value.

In one embodiment, in the acid solution mixed with the oxidant, the concentration of the oxidant is about 0.5wt%~10wt% based on the whole of the acid solution mixed with the oxidant. Preferably, the concentration of the oxidant is about 1wt%~8wt% based on the whole of the acid solution mixed with the oxidant. If the concentration of the oxidant is too low (e.g., less than 0.5wt%), the decomposition or decolorization effect of the organic dye may be poor. If the concentration of the oxidant is too high (e.g., greater than 10wt%), there may be concerns about industrial safety.

In one embodiment, the oxidizing agent can decompose the organic dye so that it (i.e., the decomposed organic dye) does not have the original color (i.e., fades).

In one embodiment, the oxidizing agent can change some functional groups of the organic dye, so that it (i.e., the organic dye after structural change) can be more easily removed from other polymers (such as polyester or nylon) (i.e., decolorized).

In one embodiment, the decomposed or structurally changed organic dye may be more easily dissolved in a solvent by treatment with an oxidizing agent. For example, the decomposed or structurally changed organic dye may be more easily dissolved in water.

In one embodiment, the first solid may include other non-nylon polymers (such as polyester). However, it is worth noting that the present invention does not exclude the first solid from including a small amount of nylon.

In one embodiment, the first liquid may include an acid solution and nylon/degraded nylon, nylon suspension or degraded nylon suspension dissolved in the acid solution. However, it is worth noting that the present invention does not exclude the possibility that the first liquid further includes a small amount of non-nylon polymers.

In one embodiment, the first liquid may not contain an oxidant. For example, hydrogen peroxide may be decomposed into water and oxygen after heating. For another example, hydrogen peroxide that has not reacted with the dye may be decomposed into water and oxygen after heating.

In one embodiment, based on the total amount of nylon in the aforementioned recyclate, the amount of nylon in the first liquid is approximately 75wt%~90wt%, and the amount of nylon in the first solid is correspondingly approximately 25wt%~10wt%.

In one embodiment, the acid solution mixed with an oxidant can improve the recovery amount or quality of nylon and/or polyester.

In one embodiment, the color of the recycled polyester can be close to white. According to the chromaticity coordinate diagram (CIE 1931 color space) developed by the International Commission on Illumination (CIE), if the color brightness (i.e., L* value) of the recycled material containing polyester, nylon and dye is about 20, the color brightness of the polyester recycled by the above method can be about 75 or more, the a* value can be about -4~+4, and the b* value can be about -8~+8.

In one embodiment, the utilization value of recycled materials (such as recycled nylon and/or recycled polyester) can be increased by improving whiteness.

[Second stage processing]

In one embodiment, the first liquid material can be subjected to a second stage of treatment to obtain a second liquid material and a second solid material.

In one embodiment, the second stage treatment may include dilution. For example, the solvent (such as water) used in the acid treatment in the first stage treatment may be added to the first liquid, and then the second liquid and the second solid may be separated from each other by appropriate means (such as filtration with a sieve or static separation, but not limited to).

In one embodiment, the second stage treatment method may further include adding the aforementioned solvent to the aforementioned first liquid, and then cooling the solution (e.g., cooling to room temperature (about 25°C); or, cooling to below room temperature and above freezing point), but the present invention is not limited thereto.

In one embodiment, the second stage treatment method may further include adding the aforementioned solvent to the aforementioned first liquid, and then stirring and/or standing the solution (e.g., stirring for 3 minutes and standing for more than 30 minutes; or, stirring for 5 minutes and standing for more than 60 minutes), but the present invention is not limited thereto.

In one embodiment, the first stage treatment may include an acid treatment of the first stage treatment by an aqueous solution containing an oxidant and 20 wt% to 95 wt% formic acid, and the second stage treatment may include adding water to the aforementioned first liquid to reduce the formic acid concentration in the solution to below about 20 wt%.

In one embodiment, the second solid may include nylon.

In one embodiment, the second liquid may include an acid solution and nylon/degraded nylon, nylon suspension or degraded nylon suspension dissolved in the acid solution. The concentration of the acidic substance in the second liquid is less than the concentration of the acidic substance in the first liquid.

In one embodiment, the second liquid may not contain an oxidizing agent.

[Third stage processing]

In one embodiment, the first solid material can be subjected to a third stage of treatment to obtain a third liquid material and a third solid material.

In one embodiment, the third stage treatment may include acid treatment. In one embodiment, the acid treatment method of the third stage treatment may be similar to the acid treatment method of the first stage treatment. For example, the first solid state may be immersed in an acid solution, and then the third liquid state and the third solid state may be separated from each other by an appropriate method (such as filtering with a sieve, but not limited to).

In one embodiment, the acid treatment in the third stage can be performed by immersing the first solid in an acid solution and heating it (e.g., heating it to about 70±5℃~100±5℃), but the present invention is not limited thereto.

In one embodiment, the acid treatment in the third stage can be performed by immersing the first solid in an acid solution and stirring and/or standing still (e.g., stirring and/or standing still for more than 30 minutes; or, stirring and/or standing still for more than 60 minutes), but the present invention is not limited thereto.

In one embodiment, the solute and solvent used in the acid treatment of the third stage treatment may be the same or similar to the solute and solvent used in the acid treatment of the first stage treatment.

In one embodiment, the acid concentration of the acid treatment in the third stage is different from the acid concentration of the acid treatment in the first stage; and the acid concentration of the acid treatment in the third stage is different from the acid concentration of the second liquid.

In one embodiment, the acid concentration of the acid treatment in the third stage is less than the acid concentration of the acid treatment in the first stage; and the acid concentration of the acid treatment in the third stage is greater than the acid concentration of the second liquid.

In one embodiment, in the acid treatment of the third stage, the concentration of the oxidant in the solution used may be less than 0.5wt%. In one embodiment, the solution used in the acid treatment of the third stage may not contain an oxidant.

In one embodiment, a 99wt% formic acid aqueous solution can be mixed with a recovered formic acid aqueous solution with a concentration of less than about 20%, and then the aforementioned mixed solution can be used as the acid solution for the acid treatment in the third stage. In this way, the overall usage of formic acid can be reduced. In one embodiment, in the aforementioned mixed solution, the concentration of formic acid can be greater than 80wt%. In this way, it can have a better dissolving effect on nylon.

In one embodiment, the formic acid aqueous solution recovered may include a second liquid obtained by performing the second stage treatment (including: the second liquid obtained in this treatment cycle; and/or the second liquid obtained in the previous treatment cycle when the method of the present invention is performed multiple times); and/or, a fourth liquid obtained by performing the fourth stage treatment (described in detail below) in the previous treatment cycle (when the method of the present invention is performed multiple times). In this way, the overall usage of formic acid can be reduced, and the nylon/degraded nylon, nylon suspension or degraded nylon suspension dissolved in the recovered formic acid aqueous solution (such as the second liquid and/or the fourth liquid) can continue to be recovered, thereby increasing the amount of nylon recovered.

For example, the method for treating waste fabrics containing polyester, nylon and dyes may include the following steps. Step a: providing waste fabrics containing polyester, nylon and dyes. Step b: performing a first stage treatment including acid treatment on the waste fabric to obtain a first liquid and a first solid. Step c: performing a second stage treatment on the first liquid to obtain a second liquid and a second solid. Step d: performing a third stage treatment on the first solid to obtain at least a third liquid. In the multiple treatment processes, step a, step b and step d can be performed N times, where N is greater than or equal to 1; step c is performed M times, where M is less than or equal to N; and the acid treatment of the third stage treatment of the Nth time includes acid treatment by the second liquid of the Mth time.

For another example, the method for treating waste fabrics containing polyester, nylon and dyes may include the following steps. Step a: providing waste fabrics containing polyester, nylon and dyes. Step b: subjecting the waste fabrics to a first stage treatment including acid treatment to obtain a first liquid and a first solid. Step c: subjecting the first liquid to a second stage treatment to obtain a second liquid and a second solid. Step d: subjecting the first solid to a third stage treatment to obtain at least a third liquid. Step e: subjecting the third liquid to a fourth stage treatment (described in detail below) to obtain a fourth liquid and a fourth solid. In the multiple treatment processes, step a, step b, step d and step e can be performed N times, where N is greater than or equal to 2; the acid treatment of the third stage treatment of the Nth time includes acid treatment by the fourth liquid of the Pth time, where P is less than N.

In one embodiment, the third solid may include other non-nylon polymers (such as polyester). However, it is worth noting that the present invention does not exclude the possibility that the third solid includes a very small amount of nylon.

In one embodiment, the proportion of nylon in the third solid (which may be the weight ratio of nylon to the entire third solid) is less than the proportion of nylon in the first solid (which may be the weight ratio of nylon to the entire first solid).

In one embodiment, the proportion of polyester in the third solid (which may be the weight ratio of polyester to the entire third solid) is greater than the proportion of polyester in the first solid (which may be the weight ratio of polyester to the entire first solid).

In one embodiment, the third liquid may include an acid solution and nylon/degraded nylon, a nylon suspension, or a degraded nylon suspension dissolved in the acid solution.

In one embodiment, the amount of nylon in the third liquid can be about 90wt% or more, or even 95wt% or more, based on the total amount of nylon in the first solid. In other words, through the two-stage acid treatment (i.e., the acid treatment in the first stage treatment and the acid treatment in the third stage treatment), the nylon in the aforementioned recyclate can be almost dissolved or degraded and separated in the subsequent steps.

[Phase 4 Processing]

In one embodiment, the third liquid material can be subjected to a fourth stage of treatment to obtain a fourth solid material and a fourth liquid material.

In one embodiment, the fourth stage treatment may include dilution. For example, the solvent used in the acid treatment in the first stage treatment or the third stage treatment may be added to the third liquid, and then the fourth liquid and the fourth solid may be separated from each other by an appropriate method (such as filtration with a sieve or static separation, but not limited thereto).

In one embodiment, the fourth stage treatment method may further include adding the aforementioned solvent to the aforementioned third liquid, and then cooling the solution (e.g., cooling to room temperature (about 25°C); or, cooling to below room temperature and above freezing point), but the present invention is not limited thereto.

In one embodiment, the fourth stage treatment method may further include adding the aforementioned solvent to the aforementioned third liquid, and then stirring and/or standing the solution (e.g., stirring for 3 minutes and standing for more than 30 minutes; or, stirring for 5 minutes and standing for more than 60 minutes), but the present invention is not limited thereto.

In one embodiment, the first stage treatment may include an acid treatment of the first stage treatment by an aqueous solution containing an oxidant and 20wt% to 95wt% formic acid, the third stage treatment may include an acid treatment of the third stage treatment by two stages of formic acid aqueous solutions of different concentrations, and the fourth stage treatment may include adding water to the aforementioned third liquid to reduce the formic acid concentration in the solution to below about 20%.

In one embodiment, the fourth solid may include nylon.

In one embodiment, the fourth liquid may include an acid solution and nylon/degraded nylon, nylon suspension or degraded nylon suspension dissolved in the acid solution. The concentration of the acidic substance in the fourth liquid is less than the concentration of the acidic substance in the third liquid.

[Recycling of nylon]

The second solid and/or fourth solid including nylon can basically be recycled and reused by appropriate means (such as nylon drawing or nylon granulation; but not limited).

In one embodiment, the second solid and/or the fourth solid can be further washed with water to reduce the concentration of acid or other substances (such as decomposed or structurally changed organic dyes or decomposed or undecomposed oxidants; but not limited to) in the second solid and/or the fourth solid, but the present invention is not limited to this.

In one embodiment, the second solid and/or the fourth solid can be dried, but the present invention is not limited thereto.

[Recycling of polyester]

The third solid including polyester can basically be recycled and reused by appropriate means (such as polyester granulation; but not limited to).

In one embodiment, the first solid and/or the third solid can be further washed with water to reduce the concentration of acid or other substances (such as decomposed or structurally changed organic dyes or decomposed or undecomposed oxidants; but not limited to) in the first solid and/or the third solid, but the present invention is not limited to this.

In one embodiment, the first solid and/or the third solid can be dried, but the present invention is not limited thereto.

[Examples and Comparisons]

The following examples and comparative examples are presented to specifically illustrate the present invention, but the present invention is not limited to the following embodiments at all.

[Example 1]

The first stage of treatment: Take 20 grams (g) of polyester (PET)-nylon blended waste fabric (L=22%, PET weight accounts for 70%, nylon weight accounts for 30%), put it into a 1 liter (L) reaction tank, and add 50g of water, 450g of formic acid, and 1.5g of sodium hypochlorite. After stirring at 90℃ for 6 hours, nylon has dissolved or cracked, and PET retains the fiber structure. Cool down to 40℃, and pass through a 3 millimeter (millimeter; mm) screen to separate PET (i.e., the first solid) and nylon slurry (i.e., the first liquid).

Second stage of treatment: Nylon slurry (i.e., the first liquid) is separated from nylon and acid by a 20 micrometer (μm) filter, and nylon powder (i.e., the second solid) is washed with 12g of water. The acid separated by the 20μm filter and the water used for washing can be collected (i.e., the second liquid).

The third stage of treatment: PET fiber (i.e., the first solid) is placed on a 3mm screen, washed with the second liquid, and then washed with 28g of water. The washed PET fiber can be collected (i.e., the third solid). The second liquid and water used for washing can be collected (i.e., the third liquid).

Fourth stage of treatment: Use a 1μm filter to separate the nylon and acid from the third liquid to obtain the fourth solid and the fourth liquid.

The PET fiber (i.e., the third solid) was dried at 105°C for 2 hours to obtain a PET fabric with a purity weight ratio of 99.5%; L=81%, a=1.2, b=6.4, which is conducive to recycling application.

The method for measuring the purity weight ratio of PET is as follows: Take a 1000 cubic centimeter (cc) triangular flask, pour 600cc of 75% weight sulfuric acid aqueous solution, and take 3g of the separated PET fabric sample into the flask. After that, heat the flask to 50℃±5℃ and maintain for 1 hour, and shake it once every 10 minutes. After completion, use a funnel with a 3mm screen to evacuate and drain the liquid, pour 200cc of 75% weight sulfuric acid aqueous solution into the funnel to wash the fabric and evacuate and drain the liquid, then pour 200CC of clean water into the funnel to wash the fabric twice; each time, evacuate and drain the liquid. Afterwards, the treated PET fabric was placed in an oven and dried at 105°C for 2 hours and weighed to 2.986g, confirming that the purity weight ratio was 99.5%. This method is used in the following other embodiments and comparative examples, so it will not be described in detail.

[Example 2]

The steps or methods are similar to [Example 1], except that acetic acid is used instead of formic acid to obtain a PET fabric with a purity weight ratio of 99.2%; L=80%, a=1.6, b=7.2, which is conducive to recycling applications.

[Example 3]

The steps or methods are similar to [Example 1], except that calcium hypochlorite is used instead of sodium hypochlorite to obtain a PET fabric with a purity weight ratio of 99.6%; L=88%, a=0.8, b=3.6, which is conducive to recycling applications.

[Comparison Example 1]

Similar to the first stage of treatment: Take 20g of PET-nylon blended waste fabric (L=22%, PET weight accounts for 70%, nylon weight accounts for 30%), put it into a 1L reaction tank, and add 50g of water and 450g of formic acid. Stir for 6 hours at a temperature of 90℃, nylon has been dissolved or cracked, and PET retains the fiber structure. Cool down to 40℃, and pass through a 3mm screen to separate PET (i.e., similar to the first solid; abbreviated as: quasi-first solid) and nylon slurry (i.e., similar to the first liquid; abbreviated as: quasi-first liquid).

Similar to the second stage of treatment: nylon slurry (i.e., quasi-first liquid) is separated from nylon and acid by a 20μm filter, and nylon powder is washed with 12g of water (i.e., similar to the second solid; referred to as: quasi-second solid). The acid separated by the 20μm filter and the water used for washing can be collected (i.e., similar to the second liquid; referred to as: quasi-second liquid).

The third stage of treatment: PET fiber (i.e., the first solid) is placed on a 3mm screen, washed with a second liquid, and then washed with 28g of water (i.e., similar to the third solid; referred to as the third solid). The second liquid and water used for washing can be collected (i.e., similar to the third liquid; referred to as the third liquid).

Fourth stage of treatment: Use a 1μm filter to separate the nylon and acid from the third-like liquid, and obtain a solid similar to the fourth solid (abbreviated as: fourth-like solid) and a liquid similar to the fourth liquid (abbreviated as: fourth-like liquid).

PET fiber (i.e., third-class solid) was dried at 105℃ for 2 hours, and the purity weight ratio of PET fabric was 99.3%; L=58%, a=2.4, b=8.9. PET fiber is grayish yellow and needs to be decolorized before it can be recycled.

[Industrial Utilization]

By the method of the present invention, nylon or polyester in the recyclables can be recovered. Moreover, the recycled nylon or polyester can be reused. The reuse method is, for example, but not limited to: the manufacture of nylon-containing materials such as fabrics, curtains, and tires. The processing methods of recycled polyester include physical reprocessing or chemical reprocessing. Physical reprocessing includes using an extruder to melt the treated polyester and then extrude it into granules. Chemical reprocessing includes using a chemical depolymerization liquid to depolymerize the recycled polyester, and then repolymerizing the monomers and/or oligomers obtained after depolymerization under specific conditions, and then granulating; the chemical depolymerization liquid can be water, methanol, ethanol, ethylene glycol, diethylene glycol or any combination. The processing method of recycled polyester can refer to the Taiwan patent application with application number 110113065.

Claims (9)

A method for treating waste fabrics containing polyester and nylon, comprising: step a: providing waste fabrics containing polyester, nylon and dye; step b: performing a first-stage treatment on the waste fabric to obtain a first liquid and a first solid; step c: performing a second-stage treatment on the first liquid to obtain a second liquid and a second solid; step d: performing a third-stage treatment on the first solid to obtain a third liquid and a third solid; and step e: performing a fourth-stage treatment on the third liquid to obtain a A fourth liquid and a fourth solid are obtained, wherein: the first stage treatment includes acid treatment by using an acid solution mixed with an oxidant to decompose or decolorize the dye and dissolve the nylon in the first stage treatment; the second stage treatment includes dilution treatment; the acid concentration of the second liquid is less than the acid concentration of the first liquid; the first solid contains recycled polyester, and the first liquid contains recycled nylon or degraded nylon or the second solid contains recycled nylon; the first stage treatment The concentration of the oxidant used in the acid treatment is 0.5wt%~10wt%; the acid treatment of the first stage treatment further includes heating to 80℃~150℃; Based on the total amount of nylon in the waste fabric, the proportion of nylon in the first liquid is greater than the proportion of nylon in the first solid, the third stage treatment includes acid treatment; the fourth stage treatment includes dilution treatment; the acid concentration of the fourth liquid is less than the acid concentration of the third liquid; the third solid contains recycled polyester, and/or The fourth solid includes recycled nylon; the step a, the step b, the step d and the step e are performed N times, wherein N is greater than or equal to 2; the step c is performed M times, wherein M is less than or equal to N; and the acid treatment of the Nth third stage treatment includes the second liquid obtained by the Mth second stage treatment; or the acid treatment of the Nth third stage treatment includes the fourth liquid obtained by the Pth fourth stage treatment, wherein P is less than N. The method for treating waste fabrics containing polyester and nylon as described in claim 1, wherein the acid used in the acid treatment in the first stage of treatment is only a straight-chain fatty acid. The method for treating waste fabrics containing polyester and nylon as described in claim 2, wherein the acid used in the acid treatment in the first stage of treatment includes only formic acid or acetic acid. The method for treating waste fabrics containing polyester and nylon as described in claim 1, wherein the oxidant is an inorganic oxidant, and the inorganic oxidant includes hydrogen peroxide, permanganate, nitric acid, nitrate, chlorate, perchlorate, hypochlorite, perborate, dichromate or a combination thereof. The method for treating waste fabrics containing polyester and nylon as described in claim 1, wherein the acid concentration used in the acid treatment of the first stage is 20wt%~95wt%. The method for treating waste fabrics containing polyester and nylon as described in claim 1, wherein the acid treatment is carried out at a temperature higher than the glass transition temperature of the polyester. The method for treating waste fabrics containing polyester and nylon as described in claim 1, wherein in step b, the weight ratio of the waste fabric to the acid solution mixed with an oxidant is 1:8~1:30. The method for treating waste fabrics containing polyester and nylon as described in claim 1, wherein the treatment time of the first stage treatment is 1 hour to 9 hours. A method for treating waste fabrics containing polyester and nylon as described in claim 1, wherein the L value of the recycled polyester is more than 75%, the a* value is -4 to +4, and the b* value is -8 to +8.

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