Method for treating waste fabrics containing polyester, nylon and dyes

Abstract

The present invention provides a method for treating waste fabric containing polyester, nylon and dye, which comprises the following steps. Step a: providing waste fabric containing polyester, nylon and dye. Step b: performing a first stage treatment including acid treatment on the waste fabric to obtain a first liquid and a first solid. The first stage treatment includes acid treatment by an acid solution mixed with an oxidant. The first solid contains recycled polyester, and / or the first liquid contains recycled nylon or degraded nylon.

Description

Technical Field

[0001] The invention relates to a method for treating waste fabrics, in particular to a method for treating waste fabrics containing polyester, nylon and dyes. Background Art

[0002] 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 made into various hats, clothes, pants, skirts, socks and other fabrics 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. Summary of the invention

[0003] The present invention is directed to a method for treating waste fabrics containing polyester, nylon and dyes, which can reduce the overall usage of acid and / or increase the recovery amount or quality of polyester and / or nylon.

[0004] According to an embodiment of the present invention, a method for treating waste fabrics containing polyester, nylon and dyes 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.

[0005] The present invention finds 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 improving the economic value of recycling and reuse.

[0006] 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a partial flow diagram of a method for treating waste containing polyester and nylon according to an embodiment of the present invention. DETAILED DESCRIPTION

[0008] Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

[0009] In the following detailed description, for the purpose of illustration and not limitation, exemplary embodiments that disclose specific details are set forth 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.

[0010] 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 to or independent of the other endpoint.

[0011] In this document, non-limiting terms (such as: may, can, for example or other similar terms) mean that implementation, inclusion, addition or existence are optional or optional.

[0012] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those 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 their meaning in the relevant technical context and should not be interpreted in an idealized or overly formal sense unless explicitly defined as such herein.

[0013] [Recyclables]

[0014] Provides recycled materials containing polyester, nylon and dyes.

[0015] In one embodiment, the method of obtaining recyclables includes, for example, collecting various types of recyclables or wastes containing nylon and polyester; and classifying the recyclables according to their types, colors, and / or uses. The recyclables may include clothing, for example, but the present invention is not limited thereto. Generally, regular clothing labels will indicate the fiber composition used.

[0016] In one embodiment, the recyclables containing nylon and polyester may 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 (e.g., clips, fasteners, accessories, labels and / or other objects that are obviously not nylon or polyester); performing preliminary cleaning of the recyclables (e.g., washing stains, shaking off impurities, etc., but not limited to); reducing the single size of the recyclables by physical means (e.g., shearing, cutting, or slicing, but not limited to); and / or drying the recyclables.

[0017] 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).

[0018] 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 co-woven fabrics.

[0019] It should be noted that the term "polyester" herein includes polymers commonly referred to as polyesters, particularly aromatic polyesters, and particularly refers to polyesters derived from purified terephthalic acid (PTA) and ethylene glycol (EG) (i.e., polyethylene terephthalate (PET)).

[0020] In addition, the polyester herein 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 particularly refer to copolymers that can be obtained by using two or more dicarboxylic acids and / or two or more diol components.

[0021] 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 good adhesion to polymers. It is worth noting that the present invention does not limit the types of organic dyes.

[0022] In one embodiment, the dye used for the fabric does not include inorganic dyes. Most inorganic dyes contain heavy metal elements, which may easily cause allergies or discomfort to the human body.

[0023] [First stage processing]

[0024] The aforementioned recovered material is subjected to a first stage of treatment to obtain a first liquid material and a first solid material.

[0025] 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 aforementioned suspended matter may be less than or equal to 1 millimeter (mm); or, according to the standard of ASTM E11-01, the aforementioned suspended matter may pass through a sieve with a mesh number of 18 or more. For another example, "liquid" may include a polymer solution (polymer colloid) or other similar colloids (colloid).

[0026] It should be noted that the term "solid" herein is not limited to a completely solid state. For example, a "solid" may include a solid; and a liquid attached to the solid or located between two solids by capillary action. The "solid" may be dried in an appropriate manner (e.g., heating and / or reduced pressure 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 may be about 80% or more; preferably about 90% or more; and more preferably about 95% or more.

[0027] In this embodiment, the first stage of treatment may include immersing the recyclables in an acid solution (which may be referred to as acid washing or acid treatment). For example, the recyclables may be immersed in an acid solution mixed with an oxidant; or, the recyclables may be immersed in an acid solution, and then the oxidant may be mixed therein. Afterwards, the first liquid and the first solid may be separated from each other by an appropriate method (such as, but not limited to, filtering with a sieve).

[0028] 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) may be about 1:8 to 1:30. Preferably, in the first stage of treatment, the weight ratio of the recyclate to the acid solution mixed with the oxidant may be about 1:10 to 1:15.

[0029] 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 heating it to about 80°C to 150°C. Preferably, it can be heated to about 90°C to 140°C, which is higher than the glass transition temperature of the polyester. If the heating temperature is too low (e.g., less than 80°C), the 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 effect of the organic dye may be poor (e.g., too much oxidant produces its own redox reaction), and / or there may be concerns about industrial safety.

[0030] In one embodiment, the acid treatment of the first stage of treatment can be performed by immersing the recyclables 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. Even more preferably, stirring and / or standing for about 2 hours to 8 hours.

[0031] In one embodiment, the acid treatment in the first stage of treatment can be performed by immersing the recyclate 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 it (the stirring and / or standing time can be as described above).

[0032] 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 damage 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 oxidants is likely to cause industrial safety hazards. Hydrochloric acid is likely 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 substances. 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 more difficult to prepare a high-concentration aqueous solution at room temperature to dissolve nylon. Phosphoric acid has poor solubility in nylon.

[0033] In one embodiment, the acid treatment of the first stage of treatment can be performed by an aqueous solution of fatty acid. Aromatic acids (such as, but not limited to, benzoic acid) have low water solubility, so it is more difficult to prepare a high-concentration aqueous solution at room temperature to dissolve nylon. In addition, 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.

[0034] In one embodiment, the acid treatment of the first stage treatment can be performed by an aqueous solution of a straight chain fatty acid. When comparing fatty acids with the same carbon number, straight chain fatty acids generally have better water solubility than sidechain fatty acids.

[0035] In one embodiment, the acid treatment of the first stage treatment may be performed by using an aqueous solution of a straight chain fatty acid having a carbon number of 3 or less. The straight chain fatty acid having a carbon number of 3 or less may have better water solubility.

[0036] In one embodiment, the acid treatment of the first stage of treatment can be performed by an aqueous solution of formic acid (i.e., formic 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 terms of application and / or treatment (e.g., waste liquid treatment, but not limited to).

[0037] In one embodiment, the acid treatment of the first stage of treatment can be performed by using an aqueous solution of formic acid. Compared with acetic acid, formic acid is more likely to dissolve nylon.

[0038] In one embodiment, the acid in the acid solution mixed with the oxidant has an acid concentration of about 20 wt% to 95 wt% based on the total amount of the acid solution mixed with the oxidant. Preferably, the acid concentration is about 30 wt% to 90 wt% based on the total amount of the acid solution mixed with the oxidant.

[0039] 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, ozone, nitric acid, nitrate, perborate (such as sodium perborate), permanganate (such as potassium permanganate), dichromate (such as sodium dichromate), or a combination thereof.

[0040] In one embodiment, in the acid treatment of the first stage of treatment, the inorganic oxidant used includes hydrogen peroxide, hypochlorite or ozone. The reduction product of hydrogen peroxide is usually water, oxygen or hydroxide. The reduction product of hypochlorite can usually be chloride ions. The reduction product of ozone can usually be oxygen. Hydrogen peroxide, hypochlorite or ozone are more eco-friendly in application and / or treatment (such as: waste liquid or waste gas treatment, but not limited to).

[0041] 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 to 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", the method of this embodiment or similar embodiments can further improve the recovery quality of polyester and nylon, and can enhance their recycling value.

[0042] In one embodiment, in the acid solution mixed with the oxidant, the concentration of the oxidant is about 0.5wt% to 10wt% based on the total amount of the acid solution mixed with the oxidant. Preferably, the concentration of the oxidant is about 1wt% to 8wt% based on the total amount 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.

[0043] In one embodiment, the oxidant can decompose the organic dye, so that the organic dye (ie, the decomposed organic dye) does not have its original color (ie, fades).

[0044] In one embodiment, the oxidant can change some functional groups of the organic dye, so that the organic dye (ie, the organic dye with the changed structure) can be more easily separated from other polymers (eg, polyester or nylon) (ie, decolorized).

[0045] In one embodiment, the decomposed or structurally changed organic dye may be more easily dissolved in a solvent by the treatment with an oxidant. For example, the decomposed or structurally changed organic dye may be more easily dissolved in water.

[0046] In one embodiment, the first solid material may include other non-nylon polymers (eg polyester). However, it should be noted that the present invention does not exclude the first solid material from also including a small amount of nylon.

[0047] In one embodiment, the first liquid may include acid solution and nylon / degraded nylon, nylon suspension or degraded nylon suspension dissolved in the acid solution. However, it should be noted that the present invention does not exclude the first liquid from also including a small amount of non-nylon polymer.

[0048] 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.

[0049] In one embodiment, based on the total amount of nylon in the recyclate, the amount of nylon in the first liquid is about 75 wt % to 90 wt %, and the amount of nylon in the first solid is correspondingly about 25 wt % to 10 wt %.

[0050] In one embodiment, the acid solution mixed with the oxidant can improve the recovery amount or quality of nylon and / or polyester.

[0051] In one embodiment, the color of the recycled polyester can be close to white. According to the chromaticity coordinate diagram (CIE1931 color space) formulated 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 recycled polyester by the above method can be about 75 or more, the a* value can be about -4 to +4, and the b* value can be about -8 to +8.

[0052] In one embodiment, the utilization value of recycled materials (such as recycled nylon and / or recycled polyester) can be increased by improving the whiteness.

[0053] [Second stage processing]

[0054] In one embodiment, the first liquid material may be subjected to a second stage of treatment to obtain a second liquid material and a second solid material.

[0055] In one embodiment, the second stage treatment may include dilution. For example, the solvent (e.g., 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 an appropriate method (e.g., filtration with a mesh or static separation, but not limited thereto).

[0056] In one embodiment, the second stage treatment method may also 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.

[0057] In one embodiment, the second stage treatment method may also 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 to this.

[0058] 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 %.

[0059] In one embodiment, the second solid object may include nylon.

[0060] In one embodiment, the second liquid may include an acid solution and nylon / degraded nylon, a nylon suspension or a 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.

[0061] In one embodiment, the second liquid may not contain an oxidant.

[0062] [Third stage processing]

[0063] In one embodiment, the first solid material may be subjected to a third stage of treatment to obtain a third liquid material and a third solid material.

[0064] In one embodiment, the third stage treatment may include an 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 may be immersed in an acid solution, and then the third liquid and the third solid may be separated from each other by an appropriate method (such as filtering with a sieve, but not limited thereto).

[0065] In one embodiment, the acid treatment in the third stage may be performed by immersing the first solid in an acid solution and heating it (eg, heating it to about 70±5° C. to 100±5° C.), but the present invention is not limited thereto.

[0066] In one embodiment, the acid treatment in the third stage may be performed by immersing the first solid in an acid solution and stirring and / or standing (eg, stirring and / or standing for more than 30 minutes; or, stirring and / or standing for more than 60 minutes), but the present invention is not limited thereto.

[0067] In one embodiment, the solute and solvent used in the acid treatment of the third stage of treatment may be the same as or similar to the solute and solvent used in the acid treatment of the first stage of treatment.

[0068] In one embodiment, the acid concentration of the acid treatment in the third stage is different from that in the first stage; and the acid concentration of the acid treatment in the third stage is different from that in the second liquid.

[0069] In one embodiment, the acid concentration of the acid solution in the third stage of the acid treatment is less than that in the first stage of the acid treatment; and the acid concentration of the acid solution in the third stage of the acid treatment is greater than the acid concentration of the second liquid.

[0070] In one embodiment, in the acid treatment of the third stage, the concentration of the oxidant in the solution used may be less than 0.5 wt %. In one embodiment, the solution used in the acid treatment of the third stage may not contain the oxidant.

[0071] In one embodiment, a 99 wt% 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 mixed solution can be used as the acid solution for the third stage of treatment. In this way, the overall amount of formic acid used can be reduced. In one embodiment, the concentration of formic acid in the mixed solution can be greater than 80 wt%. In this way, a better dissolving effect can be achieved on nylon.

[0072] In one embodiment, the aforementioned recovered formic acid aqueous solution may include the second liquid obtained after 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, the fourth liquid obtained after the fourth stage treatment (described in detail below) performed 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 subsequently recovered, thereby increasing the amount of nylon recovered.

[0073] For example, a method for treating waste fabrics containing polyester, nylon and dyes may include the following steps. Step a: Provide waste fabrics containing polyester, nylon and dyes. Step b: Perform a first stage treatment including acid treatment on the waste fabric to obtain a first liquid and a first solid. Step c: Perform a second stage treatment on the first liquid to obtain a second liquid and a second solid. Step d: Perform a third stage treatment on the first solid to obtain at least a third liquid. In multiple treatment processes, steps a, b and d may 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 Nth third stage treatment includes acid treatment with the Mth second liquid.

[0074] For another example, a method for treating waste fabrics containing polyester, nylon and dyes may include the following steps. Step a: Provide waste fabrics containing polyester, nylon and dyes. Step b: Perform a first stage treatment including acid treatment on the waste fabric to obtain a first liquid and a first solid. Step c: Perform a second stage treatment on the first liquid to obtain a second liquid and a second solid. Step d: Perform a third stage treatment on the first solid to obtain at least a third liquid. Step e: Perform a fourth stage treatment (described in detail below) on the third liquid to obtain a fourth liquid and a fourth solid. In multiple treatment processes, steps a, b, d and e can be performed N times, where N is greater than or equal to 2; the acid treatment of the Nth third stage treatment includes acid treatment of the Pth fourth liquid, where P is less than N.

[0075] In one embodiment, the third solid may include other non-nylon polymers (such as polyester). However, it should be noted that the present invention does not exclude the third solid from also including a very small amount of nylon.

[0076] 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 smaller than the proportion of nylon in the first solid (which may be the weight ratio of nylon to the entire first solid).

[0077] 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).

[0078] 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.

[0079] In one embodiment, the amount of nylon in the third liquid may be about 90 wt% or more, or more preferably 95 wt% 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 recyclate may be almost dissolved or degraded and separated in the subsequent steps.

[0080] [Fourth stage processing]

[0081] In one embodiment, the third liquid material may be subjected to a fourth stage of treatment to obtain a fourth solid material and a fourth liquid material.

[0082] 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, but not limited to, filtering with a screen or standing to separate).

[0083] In one embodiment, the fourth stage of treatment may further include adding the aforementioned solvent to the aforementioned third liquid and then cooling the solution (eg, 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.

[0084] In one embodiment, the fourth stage treatment method may also 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 to this.

[0085] In one embodiment, the first stage treatment may include acid treatment of the first stage treatment by an aqueous solution containing an oxidant and 20 wt % to 95 wt % formic acid, the third stage treatment may include 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%.

[0086] In one embodiment, the fourth solid object may include nylon.

[0087] 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.

[0088] [Recycling of nylon]

[0089] The second solid and / or the fourth solid comprising nylon can basically be recycled and reused by appropriate methods (such as nylon drawing or nylon granulation; but not limited).

[0090] In one embodiment, the second solid and / or the fourth solid may 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.

[0091] In one embodiment, the second solid material and / or the fourth solid material may be dried, but the present invention is not limited thereto.

[0092] [Recycling of polyester]

[0093] The third solid material including polyester can basically be recycled and reused by appropriate methods (such as polyester granulation, but not limited to).

[0094] In one embodiment, the first solid and / or the third solid may 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.

[0095] In one embodiment, the first solid and / or the third solid may be dried, but the present invention is not limited thereto.

[0096] [Examples and Comparative Examples]

[0097] The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples at all.

[0098] [Example 1]

[0099] First stage treatment: Take 20 grams (g) of polyester (PET)-nylon blended waste fabric (L=22%, PET accounts for 70% by weight, nylon accounts for 30% by weight), 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 a temperature of 90°C for 6 hours, the nylon has dissolved or cracked, and the PET retains the fiber structure. Cool down to 40°C and pass through a 3 mm (millimeter; mm) screen to separate the PET (i.e., the first solid) and the nylon slurry (i.e., the first liquid).

[0100] Second stage of treatment: The nylon slurry (i.e., the first liquid) is separated from the nylon and the acid by a 20 micrometer (μm) filter, and the 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).

[0101] The third stage of treatment: The PET fibers (i.e., the first solid) are placed on a 3 mm screen, washed with the second liquid, and then washed with 28 g of water. The washed PET fibers can be collected (i.e., the third solid). The second liquid and the water used for washing can be collected (i.e., the third liquid).

[0102] Fourth stage treatment: Separate the nylon and the acid solution from the third liquid with a 1 μm filter to obtain a fourth solid and a fourth liquid.

[0103] The PET fiber (ie, 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.

[0104] The method for measuring the purity weight ratio of PET is as follows: take a conical flask with a volume of 1000 cubic centimeters (cc), pour 600cc of sulfuric acid aqueous solution with a concentration of 75% by weight, 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 drain the liquid, pour 200cc of sulfuric acid aqueous solution with a concentration of 75% by weight into the funnel to wash the fabric and drain the liquid, and then pour 200CC of clean water into the funnel to wash the fabric twice; each time, drain the liquid by draining the air. After that, place the treated PET fabric in an oven and dry it at 105℃ for 2 hours, and weigh it to get 2.986g, confirming that the purity weight ratio is 99.5%. This method is used in the following other embodiments and comparative examples, so it will not be repeated.

[0105] [Example 2]

[0106] The steps or methods are similar to [Example 1], only acetic acid is used instead of formic acid, and the purity weight ratio of the obtained PET fabric is 99.2%; L=80%, a=1.6, b=7.2, which is conducive to recycling application.

[0107] [Example 3]

[0108] The steps or methods are similar to [Example 1], only calcium hypochlorite is used to replace sodium hypochlorite, and the purity weight ratio of the obtained PET fabric is 99.6%; L=88%, a=0.8, b=3.6, which is conducive to recycling application.

[0109] [Comparative Example 1]

[0110] Similar to the first stage of treatment: Take 20g of PET-nylon blended waste fabric (L=22%, PET accounts for 70% by weight, nylon accounts for 30% by weight), put it into a 1L reaction tank, and add 50g of water and 450g of formic acid. Stir at a temperature of 90°C for 6 hours, the nylon has dissolved or cracked, and the PET retains the fiber structure. Cool down to 40°C, and separate the PET (i.e., similar to the first solid; referred to as: quasi-first solid) and the nylon slurry (i.e., similar to the first liquid; referred to as: quasi-first liquid) through a 3mm sieve.

[0111] Similar to the second stage of treatment: the nylon slurry (i.e., the first liquid-like substance) is separated from the nylon and the acid solution by a 20 μm filter, and the nylon powder is washed with 12 g of water (i.e., similar to the second solid; referred to as the second solid-like substance). The acid solution separated by the 20 μm filter and the water used for washing can be collected (i.e., similar to the second liquid; referred to as the second liquid-like substance).

[0112] The third stage of treatment: The PET fiber (i.e., the first solid) is placed on a 3 mm screen, washed with a second liquid, and then washed with 28 g of water (i.e., similar to the third solid; referred to as the third solid). The second liquid and the water used for washing can be collected (i.e., similar to the third liquid; referred to as the third liquid).

[0113] Fourth stage processing: Separate nylon and acid from the third-like liquid with a 1 μm filter to 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).

[0114] 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 99.3%; L = 58%, a = 2.4, b = 8.9. PET fiber is grayish yellow and needs to be bleached before it can be recycled.

[0115] [Practicality]

[0116] By means of the method of the present invention, nylon or polyester in recyclables can be recovered. Moreover, the recycled nylon or polyester can be reused. The ways of reuse include, but are 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 depolymerizing the recovered polyester using a chemical depolymerization liquid, 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 and / or the Chinese Invention Patent Application with Application Number 202110825541.8.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for treating waste fabrics containing polyester and nylon, characterized in that: include: Step a: providing waste fabrics containing polyester, nylon and dyes; 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 material to obtain a second liquid material and a second solid material; Step d: performing a third stage treatment on the first solid material to obtain at least a third liquid material and a third solid material; and Step e: performing a fourth stage treatment on the third solid to obtain a fourth liquid and a fourth solid, wherein: The first stage treatment includes acid treatment by acid solution mixed with an oxidant to decompose or decolorize the dye and dissolve the nylon in the first stage treatment; The second stage of treatment includes a dilution process; The acid concentration of the second liquid is lower than the acid concentration of the first liquid; The first solid material comprises recycled polyester, the first liquid material comprises recycled nylon or degraded nylon, and the second solid material comprises recycled nylon; The concentration of the oxidant used in the acid treatment of the first stage of treatment is 0.5wt% to 10wt%; The acid treatment of the first stage treatment further includes heating to 80°C to 150°C; Based on the total amount of nylon in the recyclate, the amount of nylon in the first liquid is 75wt% to 90wt%, and the amount of nylon in the first solid is 25wt% to 10wt%. The third stage treatment includes acid treatment; The fourth stage of treatment includes dilution treatment; The acid concentration of the fourth liquid substance is lower than the acid concentration of the third liquid substance; The third solid material comprises recycled polyester, and the fourth solid material comprises recycled nylon; Step a, step b, step d and step e are performed N times, where N is greater than or equal to 2; Step c is performed M times, where M is less than or equal to N; The acid treatment of the third stage treatment for the Nth time includes the second liquid obtained by the second stage treatment for the Mth time; and The acid treatment of the third stage treatment for the Nth time includes the fourth liquid obtained by the fourth stage treatment for the Pth time, wherein P is less than N.

2. The method for treating waste fabrics containing polyester and nylon according to claim 1, characterized in that: The acid used in the acid treatment of the first stage is only straight-chain fatty acid.

3. The method for treating waste fabrics containing polyester and nylon according to claim 2, characterized in that: The acid used in the acid treatment of the first stage treatment includes only formic acid or acetic acid.

4. The method for treating waste fabrics containing polyester and nylon according to claim 1, characterized in that: 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.

5. The method for treating waste fabrics containing polyester and nylon according to claim 1, characterized in that: The acid concentration used in the acid treatment of the first stage is 20 wt % to 95 wt %.

6. The method for treating waste fabrics containing polyester and nylon according to claim 1, characterized in that: The acid treatment is carried out at a temperature above the glass transition temperature of the polyester.

7. The method for treating waste fabrics containing polyester and nylon according to claim 1, characterized in that: Wherein in the step b, the weight ratio of the waste fabric to the acid solution mixed with the oxidant is 1:8 to 1:

30.

8. The method for treating waste fabrics containing polyester and nylon according to claim 1, characterized in that: The processing time of the first stage processing is 1 hour to 9 hours.

9. The method for treating waste fabrics containing polyester and nylon according to claim 1, characterized in that: The recycled polyester has an L value of 75% or more, an a* value of -4 to +4, and a b* value of -8 to +8.

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