Method for treating waste fabrics containing polyester, spandex and dyes

Abstract

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

Description

Technical Field

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

[0002] Polyester fiber fabrics or spandex fiber fabrics are widely used in the market or in daily life. For example, polyester fiber can be co-woven with spandex 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 spandex 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, spandex and dyes, which can reduce the overall usage of co-solvents and / or increase the recovery amount or quality of polyester and / or spandex.

[0004] According to an embodiment of the present invention, a method for treating waste fabrics containing polyester, spandex and dyes comprises the following steps. Step a: providing waste fabrics containing polyester, spandex and dyes. Step b: performing a first stage treatment including dissolution on the waste fabrics to obtain a first liquid and a first solid. The first stage treatment includes dissolution by a co-solvent mixed with an oxidant. The first solid contains recycled polyester, and / or the first liquid contains recycled spandex or degraded spandex.

[0005] The present invention finds that in a co-solvent 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, spandex and dyes of the present invention can reduce the overall usage of co-solvents and / or increase the recovery amount or quality of spandex 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 spandex 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 necessary.

[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, spandex and dyes.

[0015] In one embodiment, the method of obtaining recyclables includes, for example, collecting various types of recyclables or wastes containing spandex 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 spandex 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 containing spandex 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 spandex and polyester (such as, but not limited to, recycled old clothes).

[0018] It should be noted that the term "spandex" herein includes polymers commonly referred to as spandex or polyurethane elastomeric fibre. In the application of fabrics, common trade names of spandex polymers include Acepora, Creora, Dorlastan, Elaspan, ESPA, INVIYA, Linel, Lycra, Neolon, ROICA, etc. Spandex can be formed by chain extension reaction of a prepolymer and a diamine. In the aforementioned chain extension reaction, the solvent used is usually dimethylformamide (DMF) or dimethylacetamide (DMAc). Spandex can include polyester spandex or polyether spandex. In this article, polyester spandex is particularly referred to. In the chain extension reaction for forming polyester spandex, the prepolymer used can be formed by a mixed reaction of glycol (eg, ethylene glycol (EG)) and a diisocyanate monomer.

[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 spandex 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 recovered material is subjected to a first-stage 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 recyclate in a mixture of an organic solvent and water (hereinafter referred to as a cosolvent) (which may be referred to as elution). For example, the recyclate may be immersed in a cosolvent mixed with an oxidant; or, the recyclate may be immersed in a cosolvent, 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 filtering with a mesh, but not limited thereto).

[0028] In one embodiment, in the first stage of treatment, the weight ratio of the recyclate to the co-solvent mixed with the oxidant (i.e., the weight of the recyclate: the weight of the co-solvent 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 co-solvent mixed with the oxidant may be about 1:10 to 1:15.

[0029] In one embodiment, the first stage of the treatment of the elution can be to immerse the recyclate in a co-solvent mixed with an oxidant and heated to about 80°C to 160°C. Preferably, it can be heated to about 90°C to 150°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 160°C), the decomposition or decolorization 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 first stage of the treatment of the elution can be performed by immersing the recyclable material in a co-solvent 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 first stage of the elution treatment can be performed by immersing the recovered material in a co-solvent mixed with an oxidant and heating it (the heating temperature can be as described above); and, during the heating process, stirring and / or standing (the stirring and / or standing time can be as described above).

[0032] In one embodiment, the elution of the first stage treatment may be performed by using a mixture of an amide solvent and water.

[0033] In one embodiment, the more suitable amide solvent may include dimethylformamide, dimethylacetamide or a combination thereof. One of the reasons may be that dimethylacetamide or dimethylformamide is more commonly used as a solvent in the reaction of synthesizing spandex.

[0034] In one embodiment, a more suitable amide solvent is dimethylformamide. Compared with dimethylacetamide, dimethylformamide may have better solubility in spandex at the same usage amount.

[0035] In one embodiment, the concentration of the organic solvent in the co-solvent mixed with the oxidant is about 20 wt% (weight percentage) to 95 wt% based on the total amount of the co-solvent mixed with the oxidant. Preferably, the concentration of the organic solvent is about 30 wt% to 90 wt% based on the total amount of the co-solvent mixed with the oxidant.

[0036] For example, the concentration of dimethylformamide is about 20 wt % to 95 wt % based on the total amount of dimethylformamide / water co-solvent mixed with the oxidant. Preferably, the concentration of dimethylformamide is about 30 wt % to 90 wt % based on the total amount of dimethylformamide / water co-solvent mixed with the oxidant.

[0037] In one embodiment, in the leaching of the first stage of 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.

[0038] In one embodiment, in the acid treatment of the first stage 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 is easier to use and / or treat (such as: waste liquid or waste gas treatment, but not limited to).

[0039] In one embodiment, the oxidant is suitable for oxidizing the organic dye, thereby decomposing or decolorizing it. Therefore, the co-solvent containing the oxidant can have both separation and decolorization effects on polyester-spandex blended fabrics containing dyes. In other words, compared to the method of "first dissolving or degrading spandex with a solvent without an oxidant, and then removing the dye for decolorization (such as using an oxidant) after separating the polyester-spandex", the method of this embodiment or similar embodiments can further improve the recycling quality of polyester and spandex, and can enhance their recycling value.

[0040] In one embodiment, the concentration of the oxidant in the co-solvent mixed with the oxidant is about 0.5wt% to 10wt% based on the total amount of the co-solvent mixed with the oxidant. Preferably, the concentration of the oxidant is about 1wt% to 8wt% based on the total amount of the co-solvent 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.

[0041] 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).

[0042] 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 spandex) (ie, decolorized).

[0043] In one embodiment, the decomposed or structurally changed organic dye may be more easily dissolved in a solvent by the treatment with an oxidizing agent. For example, the decomposed or structurally changed organic dye may be more easily dissolved in water or an organic solvent.

[0044] In one embodiment, the first solid material may include other polymers other than spandex (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 spandex.

[0045] In one embodiment, the first liquid may include a cosolvent and spandex / degraded spandex, spandex suspension or degraded spandex suspension dissolved in the cosolvent. However, it should be noted that the present invention does not exclude the first liquid from also including a small amount of non-spandex polymers.

[0046] 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.

[0047] In one embodiment, based on the total amount of spandex in the recyclate, the amount of spandex in the first liquid is approximately 75 wt % to 90 wt %, and the amount of spandex in the first solid is correspondingly approximately 25 wt % to 10 wt %.

[0048] In one embodiment, the recovery amount or quality of spandex and / or polyester can be increased by using the aforementioned co-solvent mixed with an oxidant.

[0049] In one embodiment, the color of the recycled polyester can be close to white. According to the chromaticity coordinate diagram (CIE1931 color space) developed by the International Commission on Illumination (CIE), if the color brightness (i.e., L* value) of the recycled material containing polyester, spandex 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.

[0050] In one embodiment, by improving the whiteness, the utilization value of recycled materials (such as recycled spandex and / or recycled polyester) can be increased.

[0051] [Second stage processing]

[0052] 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.

[0053] In one embodiment, the second stage of treatment may include dilution. For example, the non-organic solvent (e.g., water) used for dissolution in the first stage of 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).

[0054] In one embodiment, the second stage treatment method may also include adding the aforementioned non-organic 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 to this.

[0055] In one embodiment, the second stage treatment method may also include adding the aforementioned non-organic 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.

[0056] In one embodiment, the first stage treatment may include elution of the first stage treatment by using a dimethylformamide / water co-solvent containing an oxidant and 20 wt % to 95 wt % dimethylformamide, and the second stage treatment may include adding water to the aforementioned first liquid to reduce the dimethylformamide concentration in the solution to below about 20 wt %.

[0057] In one embodiment, the second solid material may include spandex.

[0058] In one embodiment, the second liquid may include a cosolvent and spandex / degraded spandex, spandex suspension or degraded spandex suspension dissolved in the cosolvent. The concentration of the organic solvent in the second liquid is less than the concentration of the organic solvent in the first liquid.

[0059] In one embodiment, the second liquid may not contain an oxidant.

[0060] [Third stage processing]

[0061] 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.

[0062] In one embodiment, the third stage of treatment may include elution. In one embodiment, the elution method of the third stage of treatment may be similar to the elution method of the first stage of treatment. For example, the first solid may be immersed in a co-solvent, and then the third liquid and the third solid may be separated from each other by an appropriate method (e.g., filtering with a sieve, but not limited thereto).

[0063] In one embodiment, the elution in the third stage of treatment may be performed by immersing the first solid in a co-solvent and heating it (eg, heating it to about 70±5° C. to 100±5° C.), but the present invention is not limited thereto.

[0064] In one embodiment, the elution in the third stage treatment may be performed by immersing the first solid in a co-solvent 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.

[0065] In one embodiment, the organic solvent used in the elution of the third stage process may be the same as or similar to the organic solvent used in the elution of the first stage process.

[0066] In one embodiment, the organic solvent concentration in the co-solvent of the elution processed in the third stage is different from the organic solvent concentration in the co-solvent of the elution processed in the first stage; and the organic solvent concentration in the co-solvent of the elution processed in the third stage is different from the organic solvent concentration in the second liquid.

[0067] In one embodiment, the organic solvent concentration in the co-solvent of the elution treated in the third stage is less than the organic solvent concentration in the co-solvent of the elution treated in the first stage; and the organic solvent concentration in the co-solvent of the elution treated in the third stage is greater than the organic solvent concentration in the second liquid.

[0068] In one embodiment, in the leaching 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 for the leaching of the third stage may not contain the oxidant.

[0069] In one embodiment, dimethylformamide with a purity of 99 wt% or more can be mixed with a recycled dimethylformamide / water co-solvent with a concentration of less than about 20%, and then the mixed solution can be used as a co-solvent for the third stage of treatment. In this way, the overall usage of dimethylformamide can be reduced. In one embodiment, the concentration of dimethylformamide in the mixed solution can be greater than 80 wt%. In this way, a better dissolution effect can be achieved on spandex.

[0070] In one embodiment, the aforementioned recovered dimethylformamide / water co-solvent 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 dimethylformamide can be reduced, and the spandex / degraded spandex, spandex suspension or degraded spandex suspension dissolved in the recovered dimethylformamide / water co-solvent (such as: the second liquid and / or the fourth liquid) can continue to be subsequently recovered, thereby increasing the amount of spandex recovered.

[0071] For example, a method for treating waste fabrics containing polyester, spandex and dyes may include the following steps. Step a: Provide waste fabrics containing polyester, spandex and dyes. Step b: Perform a first stage treatment including elution 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 elution of the third stage treatment for the Nth time includes elution by the second liquid for the Mth time.

[0072] For another example, a method for treating waste fabrics containing polyester, spandex and dyes may include the following steps. Step a: Provide waste fabrics containing polyester, spandex and dyes. Step b: Perform a first stage treatment including elution 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 elution of the Nth third stage treatment includes elution by the Pth fourth liquid, where P is less than N.

[0073] In one embodiment, the third solid material may include other non-spandex polymers (eg polyester). However, it should be noted that the present invention does not exclude the third solid material from also including a very small amount of spandex.

[0074] In one embodiment, the proportion of spandex in the third solid (which may be the weight ratio of spandex to the entire third solid) is smaller than the proportion of spandex in the first solid (which may be the weight ratio of spandex to the entire first solid).

[0075] 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).

[0076] In one embodiment, the third liquid may include a co-solvent and spandex / degraded spandex, spandex suspension or degraded spandex suspension dissolved in the co-solvent.

[0077] In one embodiment, the spandex content in the third liquid may be about 90 wt% or more, or more preferably 95 wt% or more, based on the total spandex content in the first solid. In other words, through the two-stage dissolution (i.e., the dissolution in the first stage and the dissolution in the third stage), the spandex in the recyclate may be almost dissolved or degraded and separated in the subsequent steps.

[0078] [Fourth stage processing]

[0079] 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.

[0080] In one embodiment, the fourth stage of treatment may include dilution. For example, the non-organic solvent used for dissolution in the first stage of treatment or the third stage of 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, filtration with a screen or static separation).

[0081] 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.

[0082] In one embodiment, the fourth stage treatment method may also include adding the aforementioned non-organic 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.

[0083] In one embodiment, the first stage treatment may include eluting the first stage treatment by using a dimethylformamide / water co-solvent containing an oxidant and 20 wt % to 95 wt % dimethylformamide, the third stage treatment may include eluting the third stage treatment by using two stages of dimethylformamide / water co-solvents with different concentrations, and the fourth stage treatment may include adding water to the aforementioned third liquid to reduce the dimethylformamide concentration in the solution to less than about 20%.

[0084] In one embodiment, the fourth solid material may include spandex.

[0085] In one embodiment, the fourth liquid may include a cosolvent and spandex / degraded spandex, spandex suspension or degraded spandex suspension dissolved in the cosolvent. The concentration of the organic solvent in the fourth liquid is less than the concentration of the organic solvent in the third liquid.

[0086] [Recycling of spandex]

[0087] The second solid and / or the fourth solid including spandex can basically be recycled and reused by appropriate methods (such as spandex drawing or spandex granulation; but not limited).

[0088] In one embodiment, the second solid and / or the fourth solid may be further washed with water to reduce the concentration of organic solvents 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.

[0089] In one embodiment, the second solid material and / or the fourth solid material may be dried, but the present invention is not limited thereto.

[0090] [Recycling of polyester]

[0091] The third solid material including polyester can basically be recycled and reused by appropriate methods (such as polyester granulation, but not limited to).

[0092] In one embodiment, the first solid and / or the third solid may be further washed with water to reduce the concentration of organic solvents 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.

[0093] In one embodiment, the first solid and / or the third solid may be dried, but the present invention is not limited thereto.

[0094] [Examples and Comparative Examples]

[0095] 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.

[0096] [Example 1]

[0097] First stage treatment: Take 20 grams (g) of polyester (PET)-spandex blended waste fabric (L=27%, PET accounts for 80% by weight, spandex accounts for 20% by weight), put it into a 1 liter (L) reaction tank, and put in 100g of water, 400g of dimethylformamide, and 1.5g of sodium hypochlorite. Stir for 6 hours at a temperature of 120°C, the spandex has dissolved, and the PET retains the fiber structure. Cool down to 40°C, and pass through a 3 mm (millimeter; mm) screen to separate PET (i.e., the first solid) and spandex slurry (i.e., the first liquid).

[0098] Second stage of treatment: The spandex slurry (i.e., the first liquid) is separated from the spandex and the co-solvent by a 10 micrometer (μm) filter, and the spandex powder (i.e., the second solid) is washed with 8g of water. The co-solvent separated by the 10μm filter and the water used for washing can be collected (i.e., the second liquid).

[0099] The third stage of treatment: The PET fiber (i.e., the first solid) is placed on a 3 mm screen, washed with the second liquid, and then washed with 32 g of water. The washed PET fiber 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).

[0100] The fourth stage of treatment: the third liquid is separated from the spandex and the co-solvent by a 1 μm filter to obtain a fourth solid and a fourth liquid.

[0101] The PET fiber (ie, the third solid) is dried at 105° C. for 2 hours to obtain a PET fabric with a purity weight ratio of 99.7%; L=84%, a=0.9, b=5.7, which is conducive to recycling application.

[0102] The method for measuring the purity weight ratio of PET is as follows: take a 1000 cubic centimeter (cc) Erlenmeyer flask, pour 600cc of 75% by weight sulfuric acid aqueous solution into it, take 3g of the separated PET fabric sample into the flask, heat the flask to 50℃±5℃ 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 75% by weight sulfuric acid aqueous solution into the funnel to wash the fabric and drain the liquid, 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.

[0103] [Example 2]

[0104] The steps or methods are similar to [Example 1], only dimethylacetamide is used to replace dimethylformamide, and the purity weight ratio of the obtained PET fabric is 99.3%; L=81%, a=1.4, b=6.9, which is conducive to recycling application.

[0105] [Example 3]

[0106] The steps or methods are similar to [Example 1], only calcium hypochlorite is used instead of sodium hypochlorite, and the purity weight ratio of the obtained PET fabric is 99.6%; L=85%, a=0.9, b=3.4, which is conducive to recycling application.

[0107] [Comparative Example 1]

[0108] Similar to the first stage of treatment: 20g of PET-spandex blended waste fabric (L=27%, PET accounts for 80% by weight, spandex accounts for 20% by weight), placed in a 1L reaction tank, and added with 100g of water and 400g of dimethylformamide, stirred at a temperature of 110°C for 6 hours, the spandex has dissolved, 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 spandex slurry (i.e., similar to the first liquid; referred to as: quasi-first liquid) through a 3mm sieve.

[0109] Similar to the second stage of treatment: the spandex slurry (i.e., the first liquid-like substance) is separated from the spandex and the co-solvent by a 10 μm filter, and the spandex powder is washed with 8 g of water (i.e., similar to the second solid; referred to as the second solid-like substance). The co-solvent separated by the 10 μm filter and the water used for washing can be collected (i.e., similar to the second liquid-like substance; referred to as the second liquid-like substance).

[0110] Similar to the third stage treatment: PET fiber (i.e., quasi-first solid) is placed on a 3 mm screen, washed with quasi-second liquid, and then washed with 32 g of water (i.e., similar to the third solid; referred to as quasi-third solid). The quasi-second liquid after washing and the water after washing can be collected (i.e., similar to the third liquid; referred to as quasi-third liquid).

[0111] Similar to the fourth stage of treatment: the third-like liquid is separated from the spandex and the co-solvent by a 1 μm filter to obtain a solid similar to the fourth solid (abbreviated as: the fourth-like solid) and a liquid similar to the fourth liquid (abbreviated as: the fourth-like liquid).

[0112] 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 99.4%; L = 57%, a = 2.2, b = 9.4. PET fiber is grayish yellow and needs to be bleached before it can be recycled.

[0113] [Practicality]

[0114] By means of the method of the present invention, spandex or polyester in the recyclate can be recovered. Moreover, the recycled spandex or polyester can be reused. The ways of reuse include, but are not limited to: the manufacture of spandex-containing materials such as fabrics, curtains, and tires. The treatment 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 treatment method of recycled polyester can refer to the Taiwan Patent Application No. 110113065 and / or the Chinese Invention Patent Application No. 202110825541.8.

[0115] 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 spandex, characterized in that: include: Step a: providing waste fabrics containing polyester, spandex and dyes; as well as 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 to obtain a third liquid and a third solid; 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 of treatment includes dissolution by a co-solvent mixed with an oxidant; The second stage of treatment includes a dilution process; The concentration of the organic solvent in the second liquid is lower than the concentration of the organic solvent in the first liquid; The first solid material comprises recycled polyester; The first liquid material comprises recycled spandex or degraded spandex, and the second solid material comprises recycled spandex; The concentration of the oxidant used in the dissolution of the first stage treatment is 0.5wt% to 10wt%; The first stage of treatment further comprises heating to 80°C to 150°C; Based on the total amount of spandex in the recyclate, the amount of spandex in the first liquid is 75wt% to 90wt%, and the amount of spandex in the first solid is 25wt% to 10wt%; The third stage of treatment includes leaching; The fourth stage of treatment includes dilution treatment; The concentration of the organic solvent in the fourth liquid substance is lower than the concentration of the organic solvent in the third liquid substance; The third solid material comprises recycled polyester, and the fourth solid material comprises recycled spandex; 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 dissolution of the third stage treatment for the Nth time includes dissolution of the second liquid obtained by the second stage treatment for the Mth time; and The dissolution of the third stage treatment for the Nth time includes dissolution performed by 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 spandex according to claim 1, characterized in that: The co-solvent used in the dissolution of the first stage treatment is a mixture of an amide solvent and water.

3. The method for treating waste fabrics containing polyester and spandex according to claim 2, characterized in that: The organic solvent used in the co-solvent only includes dimethylformamide or dimethylacetamide.

4. The method for treating waste fabrics containing polyester and spandex 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 spandex according to claim 1, characterized in that: The concentration of the organic solvent in the co-solvent used in the dissolution of the first stage treatment is 20 wt % to 95 wt %.

6. The method for treating waste fabrics containing polyester and spandex according to claim 1, characterized in that: The dissolution is carried out at a temperature higher than the glass transition temperature of the polyester.

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

30.

8. The method for treating waste fabrics containing polyester and spandex 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 spandex 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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