TWI854185B - Disposal method for waste fabric containing polyester, spandex and dye - Google Patents

Abstract

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

Description

Processing method for waste fabrics containing polyester, spandex 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, spandex and dyes.

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 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 spandex 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, 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.

The method for treating waste fabrics containing polyester, spandex and dyes of the present invention 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.

The present invention found 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 enhancing the economic value of recycling and reuse.

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.

Figure 1 is a partial schematic diagram of a method for treating waste containing polyester and spandex 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, spandex and dyes.

In one embodiment, the method of obtaining recyclables includes, for example, collecting various types of recyclables or waste containing spandex 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 thereto. The fiber composition used in the clothing will be indicated on the regular clothing label.

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 (such as clips, fasteners, accessories, labels and/or other items that are obviously not containing spandex or polyester); performing preliminary cleaning of the recyclables (such as washing stains, throwing off impurities, etc., but not limited to); reducing the single size of the recyclables by physical means (such as shearing, cutting, 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 spandex and polyester (such as, but not limited to, recycled old clothes).

It should be noted that the term "spandex" herein includes polymers commonly referred to as spandex or polyurethane elastomeric fibre. In textile applications, 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). The spandex may include polyester spandex or polyether spandex. In this article, it particularly refers to polyester spandex. In the chain expansion reaction for forming polyester spandex, the prepolymer used may be formed by a mixed reaction of a glycol (such as ethylene glycol (EG)) and a diisocyanate monomer.

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 often used for dyeing spandex 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 a first-stage treatment 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 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 sieve, but not limited thereto).

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) can be about 1:8~1:30. Preferably, in the first stage of treatment, the weight ratio of the recyclate to the co-solvent mixed with the oxidant can be about 1:10~1:15.

In one embodiment, the first stage of the treatment of the elution can be performed by immersing the recyclate in a co-solvent mixed with an oxidant and heating it to about 80°C~160°C. Preferably, it can be heated to about 90°C~150°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 160°C), the decomposition or decolorization of the organic dye 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 first stage of the treatment of the leaching can be performed by immersing the recyclate 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. More preferably, stirring and/or standing for about 2 hours to 8 hours.

In one embodiment, the first stage of the treatment of the elution 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 still (the stirring and/or standing still time can be as described above).

In one embodiment, the first stage of treatment can be performed by dissolving in a mixture of an amide solvent and water.

In one embodiment, the more suitable amide solvent may include dimethylformamide, dimethylacetamide or a combination thereof, one of the reasons being that dimethylacetamide or dimethylformamide is more commonly used as a solvent in the reaction of synthesizing ammonia.

In one embodiment, a more suitable amide solvent is dimethylformamide. At the same usage amount, dimethylformamide may have better solubility in ammonium than dimethylacetamide.

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

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

In one embodiment, in the leaching 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 leaching of the first stage treatment, 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 easier to apply and/or treat (such as: waste liquid or waste gas treatment, but not limited to).

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 with the method of "first dissolving or degrading the spandex with a solvent without an oxidant, and then removing the dye for decolorization (such as using an oxidant) after separating the polyester-spandex", this embodiment or a method similar to the embodiment can further improve the recovery quality of polyester and spandex, and can enhance their recycling value.

In one embodiment, in the co-solvent mixed with the oxidant, the concentration of the oxidant is about 0.5wt%~10wt% based on the whole co-solvent mixed with the oxidant. Preferably, the concentration of the oxidant is about 1wt%~8wt% based on the whole 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.

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 spandex) (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 or an organic solvent.

In one embodiment, the first solid may include other non-spandex 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 spandex.

In one embodiment, the first liquid may include a co-solvent and ammonia/degraded ammonia, ammonia suspension or degraded ammonia suspension dissolved in the co-solvent. 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-ammonia 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 ammonia in the aforementioned recyclables, the amount of ammonia in the first liquid is approximately 75wt%~90wt%, and the amount of ammonia in the first solid is correspondingly approximately 25wt%~10wt%.

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.

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, spandex 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 spandex 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 of treatment may include dilution. For example, the non-organic solvent (such as 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 appropriate means (such as filtration with a sieve or static separation, but not limited thereto).

In one embodiment, the second stage treatment method may further 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 thereto.

In one embodiment, the second stage treatment method may further 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 thereto.

In one embodiment, the first stage treatment may include dissolution 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 concentration of dimethylformamide in the solution to less than about 20 wt%.

In one embodiment, the second solid may include spandex.

In one embodiment, the second liquid may include a co-solvent and ammonia/degraded ammonia, ammonia suspension or degraded ammonia suspension dissolved in the co-solvent. The concentration of the organic solvent in the second liquid is less than the concentration of the organic solvent 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 of treatment may include leaching. In one embodiment, the leaching method of the third stage of treatment may be similar to the leaching 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 (such as filtering with a sieve, but not limited to).

In one embodiment, the third stage of dissolution treatment can be performed by immersing the first solid in a co-solvent 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 third stage of dissolution treatment can be performed by immersing the first solid in a co-solvent and stirring and/or standing (e.g., 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.

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

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

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

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

In one embodiment, dimethylformamide with a purity of 99wt% or more can be mixed with a recycled dimethylformamide/water co-solvent with a concentration of less than about 20%, and then the aforementioned 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, in the aforementioned mixed solution, the concentration of dimethylformamide can be greater than 80wt%. In this way, a better dissolution effect can be achieved on ammonia.

In one embodiment, the aforementioned recovered dimethylformamide/water co-solvent may include a 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, a 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 ammonia/degraded ammonia, ammonia suspension or degraded ammonia suspension dissolved in the recovered dimethylformamide/water co-solvent (such as the second liquid and/or the fourth liquid) can be continuously recovered, thereby increasing the amount of ammonia recovered.

For example, the method for treating waste fabrics containing polyester, spandex and dyes may include 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. 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 dissolution of the third stage treatment of the Nth time includes dissolution by the second liquid of the Mth time.

For another example, a method for treating waste fabrics containing polyester, spandex and dyes may include 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. 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. Step e: performing a fourth stage treatment on the third liquid (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 dissolution of the third stage treatment of the Nth time includes dissolution by the fourth liquid of the Pth time, where P is less than N.

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

In one embodiment, the proportion of ammonia in the third solid (which may be the weight ratio of ammonia to the entire third solid) is less than the proportion of ammonia in the first solid (which may be the weight ratio of ammonia 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 a co-solvent and ammonia/degraded ammonia, ammonia suspension or degraded ammonia suspension dissolved in the co-solvent.

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

In one embodiment, the first stage treatment may include dissolving out 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 dissolving out the third stage treatment by using two stages of dimethylformamide/water co-solvents of different concentrations, and the fourth stage treatment may include adding water to the aforementioned third liquid to reduce the concentration of dimethylformamide in the solution to less than about 20%.

In one embodiment, the fourth solid may include ammonium.

In one embodiment, the fourth liquid may include a co-solvent and ammonia/degraded ammonia, ammonia suspension or degraded ammonia suspension dissolved in the co-solvent. The concentration of the organic solvent in the fourth liquid is less than the concentration of the organic solvent in the third liquid.

[Recycling of Spandex]

The second solid state and/or the fourth solid state including spandex can basically be recycled and reused by appropriate means (such as spandex drawing or spandex granulation, but not limited to).

In one embodiment, the second solid and/or the fourth solid can 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.

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 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.

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)-spandex blended waste fabric (L=27%, PET weight accounts for 80%, spandex weight accounts for 20%), put it into a 1 liter (L) reaction tank, and add 100g of water, 400g of dimethylformamide, and 1.5g of sodium hypochlorite. Stir for 6 hours at a temperature of 120℃, the spandex has dissolved, and the 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 spandex slurry (i.e., the first liquid).

Second stage of treatment: The ammonia slurry (i.e., the first liquid) is separated from the ammonia and the co-solvent by a 10 micrometer (μm) filter, and the ammonia 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).

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 32g 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 third liquid from the ammonia and the co-solvent 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 99.7%; L=84%, a=0.9, b=5.7, which is conducive to recycling applications.

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 ratio sulfuric acid aqueous solution, 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 air, pour 200cc of 75% weight ratio sulfuric acid aqueous solution into the funnel to wash the fabric and drain the air, then pour 200cc of clean water into the funnel to wash the fabric twice; each time, drain the liquid by vacuuming. 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 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 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=85%, a=0.9, b=3.4, which is conducive to recycling applications.

[Comparison Example 1]

Similar to the first stage of treatment: Take 20g of PET-spandex blended waste fabric (L=27%, PET weight accounts for 80%, spandex weight accounts for 20%), put it into a 1L reaction tank, and add 100g of water and 400g of dimethylformamide, stir at a temperature of 110℃ for 6 hours, the spandex has dissolved, and the PET retains the fiber structure. Cool down to 40℃, pass through a 3mm sieve to separate PET (i.e., similar to the first solid; abbreviated as: quasi-first solid) and spandex slurry (i.e., similar to the first liquid; abbreviated as: quasi-first liquid).

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

Similar to the third stage treatment: PET fiber (i.e., the first solid) is placed on a 3mm screen, washed with the second liquid, and then washed with 32g 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).

Similar to the fourth stage of treatment: Use a 1μm filter to separate the third-like liquid from the ammonia and the co-solvent, and 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).

PET fiber (i.e., third-class solid) was dried at 105℃ for 2 hours, and the purity weight ratio of PET fabric was 99.4%; L=57%, a=2.2, b=9.4. PET fiber is grayish yellow and needs to be decolorized before it can be recycled.

[Industrial Utilization]

By the method of the present invention, the spandex or polyester in the recyclate can be recovered. Moreover, the recovered spandex or polyester can be reused. The reuse method includes, but is not limited to: the manufacture of fabrics, curtains, tires and other spandex-containing materials. The processing method of the recycled polyester includes 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 recovered 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 the recycled polyester can refer to the Taiwan patent application with application number 110113065.

Claims (9)

A method for treating waste fabrics containing polyester and spandex, comprising: step a: providing waste fabrics containing polyester, spandex and dyes; step b: performing a first-stage treatment on the waste fabrics 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 The method comprises the steps of: performing a first-stage treatment to obtain a fourth liquid and a fourth solid, wherein: the first-stage treatment comprises dissolution by a co-solvent mixed with an oxidant; the second-stage treatment comprises a dilution treatment; the concentration of the organic solvent in the second liquid is less than the concentration of the organic solvent in the first liquid; the first solid comprises recycled polyester; the first liquid comprises recycled ammonia or degraded ammonia, or the second solid comprises recycled ammonia; the concentration of the oxidant used in the dissolution of the first-stage treatment is 0.5wt%~10wt%; the dissolution of the first stage treatment further includes heating to 80℃~150℃; Based on the total amount of polyester in the waste fabric, the proportion of polyester in the first liquid is greater than the proportion of polyester in the first solid; the third stage treatment includes dissolution; the fourth stage treatment includes dilution treatment; the concentration of organic solvent in the fourth liquid is less than the concentration of organic solvent in the third liquid; the third solid contains recycled polyester, and/or the first The four solids include recovered ammonia; 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 elution of the third stage treatment for the Nth time includes the second liquid obtained by the second stage treatment for the Mth time; or the elution 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. The method for treating waste fabrics containing polyester and spandex as described in claim 1, wherein the co-solvent used in the dissolution of the first stage of treatment is a mixture of an amide solvent and water. The method for treating waste fabrics containing polyester and spandex as described in claim 2, wherein the organic solvent used in the co-solvent only includes dimethylformamide or dimethylacetamide. The method for treating waste fabrics containing polyester and spandex 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 spandex as described in claim 1, wherein the concentration of the organic solvent in the co-solvent used in the elution of the first stage treatment is 20wt%~95wt%. The method for treating waste fabrics containing polyester and spandex as described in claim 1, wherein the dissolution is carried out at a temperature higher than the glass transition temperature of the polyester. The method for treating waste fabrics containing polyester and spandex as described in claim 1, wherein in step b, the weight ratio of the waste fabric to the co-solvent mixed with an oxidant is 1:8~1:30. The method for treating waste fabrics containing polyester and spandex as described in claim 1, wherein the treatment time of the first stage treatment is 1 hour to 9 hours. The method for treating waste fabrics containing polyester and spandex as described in claim 1, wherein the L value of the recycled polyester is greater than 75%, the a* value is from -4 to +4, and the b* value is from -8 to +8.

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