Methods and Systems for Vapor-Based Decolorization of Polyester Textiles

This application is a Continuation-in-part of International Application No. PCT/CN2024/074872 filed on Jan. 31, 2024, the contents of which are hereby incorporated by reference.

The present disclosure relates to the field of polyester textile recycling technology, and in particular, to methods and systems for vapor-based decolorization of polyester textiles.

With the continuous increase in the production and sales of polyester textiles (e.g., polyethylene terephthalate (PET)), the amount of discarded polyester textiles has grown accordingly. Due to the necessity of chemical dyeing during polyester manufacturing, the wide variety of colors significantly limits the applicability of recycled polyester textiles. Accordingly, decolorization of the discarded polyester textiles has become a critical process in polyester recycling.

Conventional decolorization techniques for the polyester textiles include an immersion-based decolorization technique and a vapor-based decolorization technique. The immersion-based decolorization technique has drawbacks, such as, excessive water consumption and the need for subsequent drying of the decolorized material. The existing vapor-based decolorization technique, such as the technique disclosed in Chinese Patent Application CN101644007A, includes heating a decolorizing agent to vapor for contact with the polyester textile to dissolve the dye. When a small amount of discarded polyester textiles is processed, the vapor-based decolorization technique overcomes the drawbacks of the immersion-based decolorization technique, and ensures sufficient contact between the vapor of the decolorizing agent and the discarded polyester textiles. However, when the amount of discarded polyester textiles increases, the discarded polyester textiles would be stacked in a vapor-based decolorization device. When a stacking thickness of the discarded polyester textiles is relatively large or a knitting density and an airtightness of the discarded polyester textiles are relatively high, resistance to vapor diffusion increases. Therefore, the vapor of the decolorizing agent has difficulty in penetrating into an interior of the stacked polyester textiles, preventing sufficient contact between the vapor of the decolorizing agent and the polyester textiles. This leads to a low decolorization rate and uneven decolorization.

Therefore, it is desired to provide methods and systems for the vapor-based decolorization of the polyester textiles. By adding a phase change material having a phase change property to the polyester textiles, when the vapor of the decolorizing agent rises, a local temperature difference can be generated within the stacked polyester textiles, thereby guiding the vapor of the decolorizing agent to penetrate into the stacked polyester textiles. As a result, the vapor of the decolorizing agent can sufficiently contact the polyester textiles, thereby improving the decolorization rate and the uniformity of decolorization.

Embodiments of the present disclosure are intended to provide a method and a system for vapor-based decolorization of a polyester textile to address the issues of low decolorization rate and uneven decolorization when processing a large amount of discarded polyester textile using the conventional vapor-based decolorization approach.

Through extensive research on decolorization techniques for discarded polyester textiles, it has been discovered that when a phase change material is used in the vapor-based decolorization of a colored discarded polyester textile, the phase change material undergoes a phase change under the influence of a high temperature of the vapor of a decolorizing agent. The phase change can create a local temperature difference within stacked polyester textile, thereby guiding the vapor of the decolorizing agent to penetrate the stacked polyester textiles. As a result, the vapor comes into sufficient contact with the polyester textile, significantly improving the decolorization rate and achieving uniform decolorization.

In order to achieve the above objects, one or more embodiments of the present disclosure provide a method for vapor-based decolorization of a polyester textile. The method comprises: obtaining a textile to be decolorized by adding a phase change material to the polyester textile for mixing, and performing the vapor-based decolorization on the textile to be decolorized. An amount of the phase change material correspondes to a weight of polyester in the polyester textile, and a phase change temperature of the phase change material is not greater than a vapor temperature of a decolorizing agent used in the vapor-based decolorization.

One or more embodiments of the present disclosure provide a system for vapor-based decolorization of a polyester textile, comprising a mixing device, a vapor-based decolorization device, and a processor. The processor is configured to: obtain a textile to be decolorized by adding a phase change material to the polyester textile for mixing through the mixing device, and perform the vapor-based decolorization on the textile to be decolorized through the vapor-based decolorization device. An amount of the phase change material corresponds to a weight of polyester in the polyester textile, and a phase change temperature of the phase change material is not greater than a vapor temperature of a decolorizing agent used in the vapor-based decolorization.

One or more embodiments of the present disclosure provide a non-transitory computer-readable storage medium storing computer instructions. When reading the computer instructions in the storage medium, a computer implements the method for vapor-based decolorization of a polyester textile provided in one or more embodiments of the present disclosure.

The present disclosure is described in further detail below by way of embodiments. All of the features disclosed in the present disclosure, or all of the operations in the methods or processes disclosed, may be combined in any manner except for mutually exclusive features and/or operations. It should be understood that the preferred embodiments described herein are for illustration and understanding of the present disclosure only, and are not intended to be limiting of the present disclosure.

The materials, reagents, or the like used in the embodiments of the present disclosure, unless otherwise specified, are commercially available. The experimental techniques for which specific conditions are not indicated in the embodiments are typically carried out under conventional conditions or under the conditions recommended by the manufacturer.

One or more embodiments of the present disclosure provide a system for vapor-based decolorization of a polyester textile. The system includes a mixing device, a vapor-based decolorization device, and a processor. The processor is configured to obtain a textile to be decolorized by adding a phase change material to the polyester textile for mixing through the mixing device, and perform vapor-based decolorization on the textile to be decolorized through the vapor-based decolorization device.

In some embodiments, the polyester textile may be a polyester-containing textile in which a mass percentage of polyester is within a preset percentage range. The preset percentage range may be predetermined based on historical experience. For example, the preset percentage range may be from 65% to 99%, etc.

In some embodiments, the polyester-containing textile may include at least one of a pure polyester textile (e.g., a polyester-containing textile in which the mass percentage of polyester is 99%, etc.), a polyester-cotton textile, a polyester-nylon textile, a polyester-spandex textile, a polyester blended textile, etc.

The textile to be decolorized refers to a polyester textile that requires vapor-based decolorization. The polyester textile refers to a discarded polyester-containing textile.

The mixing device refers to a device for mixing the polyester textile and a phase change material. In some embodiments, the mixing device may include a stirring mixer, etc. An operator (e.g., a worker, etc.) may add the polyester textile and the phase change material to the mixing device for mixing to obtain the textile to be decolorized.

In some embodiments, the mixing device may include a robotic arm, etc. The processor may control the robotic arm to add the polyester textile and the phase change material to the mixing device for mixing to obtain the textile to be decolorized.

In some embodiments, the processor may send a mixing parameter to the mixing device to control the mixing device to mix the polyester textile and the phase change material. The mixing parameter refers to a parameter related to the operation of the mixing device, such as a duration and a temperature of mixing and heating. More descriptions regarding the mixing parameter may be found elsewhere (e.g., Example 1, etc.) and relevant descriptions thereof.

The phase change material refers to a material capable of absorbing, storing, or releasing a large amount of thermal energy over a temperature range. During the vapor-based decolorization of the textile to be decolorized, the phase change material may change a temperature of the textile to be decolorized through a state transition (e.g., a transition from liquid to gas, a transition from solid to liquid, etc.). For example, the phase change material may absorb a large amount of thermal energy and change from a liquid state to a gaseous state, thereby reducing the temperature of the textile to be decolorized.

The vapor-based decolorization device refers to a device for performing vapor-based decolorization on the textile to be decolorized. In some embodiments, the vapor-based decolorization device may include a steam reaction vessel, a steam retort, or the like.

In some embodiments, a processing metal mesh may be provided in the vapor-based decolorization device. The processing metal mesh may be used to hold the textile to be decolorized and allow vapor to penetrate the textile to be decolorized. In some embodiments, a material of the processing metal mesh may include stainless steel, an alloy, or the like.

In some embodiments, the vapor-based decolorization device may heat a decolorizing agent to convert the decolorizing agent from a solid state or a liquid state into vapor, and allow the vapor of the decolorizing agent to remain in continuous contact with the textile to be decolorized, thereby performing vapor-based decolorization. The decolorizing agent refers to a reagent capable of removing color from the textile to be decolorized.

In some embodiments, the system for vapor-based decolorization of a polyester textile may further include a processor. The processor may be configured to process data from at least one device of the system or an external data source. In some embodiments, the processor may be communicatively connected with the mixing device, the vapor-based decolorization device, etc.

In some embodiments, the processor may include a central processing unit (CPU), an application-specific integrated circuit (ASIC), an application-specific instruction set processor (ASIP), an image processing unit (GPU), a physical operations processing unit (PPU), a digital signal processor (DSP), a controller, a microcontroller unit, a microprocessor, etc., or any combination thereof. In some embodiments, the processor may be integrated with a storage device. The storage device is configured to store data related to the vapor-based decolorization of the polyester textile.

More descriptions regarding the system for vapor-based decolorization of a polyester textile may be found below and in the relevant descriptions.

In some embodiments of the present disclosure, the system for vapor-based decolorization of a polyester textile mixes the polyester textile with the phase change material to obtain the textile to be decolorized, and performs vapor-based decolorization on the textile to be decolorized using the vapor-based decolorization device. This allows the vapor of the decolorizing agent to fully contact the polyester textile, thereby achieving effective vapor-based decolorization of the polyester textile. Additionally, the system is capable of processing various types and large amounts of polyester textiles.

is a flowchart of an exemplary process of a method for vapor-based decolorization of a polyester textile according to some embodiments of the present disclosure. In some embodiments, processis executed by a processor. As shown in, processincludes following operations.

In, a textile to be decolorized may be obtained by adding a phase change material to the polyester textile for mixing.

In some embodiments, the processor may mix the polyester textile and the phase change material through a mixing device to obtain the textile to be decolorized.

In some embodiments, an amount of the phase change material corresponds to a weight of polyester in the polyester textile. The corresponding relationship may be preset based on historical experience. For example, the corresponding relationship indicates that the amount of the phase change material ranges from 1% to 5% of the weight of the polyester in the polyester textile. As another example, the corresponding relationship indicates that the amount of the phase change material ranges from 2% to 4% of the weight of the polyester in the polyester textile. As yet another example, the corresponding relationship indicates that the amount of the phase change material may be 3% of the weight of the polyester in the polyester textile.

In some embodiments, a phase change temperature of the phase change material is not greater than a vapor temperature of a decolorizing agent used in the vapor-based decolorization. The phase change temperature refers to a temperature at which the phase change material is capable of changing state of matter. The vapor temperature of the decolorizing agent refers to a temperature of the vapor after the decolorizing agent is converted from a solid state or a liquid state to vapor due to an increase in temperature.

In some embodiments, the phase change temperature and the vapor temperature of the decolorizing agent are determined by properties of the phase change material and the decolorizing agent, which may be determined by consulting books, literature, etc.

In some embodiments, the phase change material may be a powdered solid.

In some embodiments of the present disclosure, the phase change material in the form of the powdered solid can be dispersed more uniformly on a surface of the polyester textile, thereby increasing a contact area between the phase change material and the polyester textile.

In some embodiments, the phase change material may include one or more of paraffin, polyethylene glycol, etc. In some embodiments, the paraffin may include industrial-grade paraffin, etc. An average molecular weight of the polyethylene glycol may range from 600 to 20,000, etc. For example, the average molecular weight of the polyethylene glycol may range from 1,000 to 15,000. As another example, the average molecular weight of the polyethylene glycol may range from 5000 to 12000. As yet another example, the average molecular weight of the polyethylene glycol may range from 7000 to 10000. The average molecular weight of the polyethylene glycol refers to an average of the molecular weights of all molecules in the polyethylene glycol.

In some embodiments, the phase change material may include a polyethylene glycol-based composite phase change material, or the like. A raw material of the polyethylene glycol-based composite phase change material includes polyethylene glycol. For example, the polyethylene glycol-based composite phase change material may be a composite phase change material that consists of polyethylene glycol compounded with expanded graphite, biomass carbon, or silicon oxide, etc.

In some embodiments, the polyethylene glycol-based composite phase change material may include a polyethylene glycol-silicon oxide composite material, or the like. In some embodiments, the polyethylene glycol-silicon oxide composite material includes a polyethylene glycol-silicon dioxide composite material, or the like.

In some embodiments of the present disclosure, due to the advantageous properties of the polyethylene glycol or the polyethylene glycol-based composite phase change material, such as suitable phase transition temperature, high latent heat capacity, non-toxicity, low vapor pressure, and excellent thermochemical stability after prolonged use, using the polyethylene glycol or the polyethylene glycol-based composite phase change material as the phase change material can enhance the recyclability and reuse efficiency of the phase change material.

In some embodiments, in the method for vapor-based decolorization of a polyester textile, preprocessing may be performed on the phase change material before adding the phase change material to the polyester textile through the mixing device.

In some embodiments, to perform the preprocessing, the processor determines a preprocessing manner based on a textile feature of the polyester textile, determines a preprocessing parameter based on the textile feature and the preprocessing manner, and performs the preprocessing on the phase change material based on the preprocessing manner and the preprocessing parameter through the preprocessing device.

The textile feature refers to data that characterizes attributes or properties of the polyester textile. In some embodiments, the textile feature may include at least one of a textile structure, a textile type, a knit density, a pile thickness, or the like. The textile structure may include a woven fabric, a knitted fabric, a nonwoven fabric, etc. The textile type may include pure polyester, a high polyester blend, a low polyester blend, etc. The knit density may include high density, medium density, low density, etc. The pile thickness may include high thickness, medium thickness, low thickness, etc.

In some embodiments, the system for vapor-based decolorization of a polyester textile may include a light source device, a measuring device, etc. The light source device may include a light source box, etc. The measuring device may include a spectrophotometer, a Near-Infrared (NIR) spectrometer, a fabric densitometer, a laser rangefinder, etc. The light source device, the measurement device, or the like may be communicatively connected with the processor.

In some embodiments, the processor may determine the textile structure based on light transmittance of the polyester textile. For example, the processor may randomly select a preset proportion of the polyester textile as a sample and control the light source device to irradiate a unit area of the sample to obtain, through the spectrophotometer or the like, the light transmittance per unit area of the sample, and the textile structure may be determined based on the light transmittance. The preset proportion may be set in advance based on historical experience, such as 10% of a total volume of the polyester textile. The unit area may be preset, such as 10 square centimeters, etc.

In some embodiments, if the light transmittance is greater than 50%, the textile structure is a woven fabric. If the light transmittance is between 30% and 50%, the textile structure is a knitted fabric. If the light transmittance is less than 30%, the textile structure is a nonwoven fabric.

In some embodiments, the processor may determine the textile type based on the mass percentage of polyester. For example, the processor may scan random spots of the polyester textile using the NIR spectrometer or the like to obtain the mass percentage of polyester at the random spots. If the mass percentage of polyester is greater than 95%, the textile type is pure polyester. If the mass percentage of polyester is between 70% and 95%, the textile type is a high polyester blend. If the mass percentage of polyester is less than 70%, the textile type is a low polyester blend. The count of the random points may be preset based on historical experience.

In some embodiments, the processor may determine the knit density based on a count of needle holes per unit area. For example, the processor may randomly select a preset proportion of the polyester textile as a sample and control a fabric densitometer or the like to obtain the count of needle holes per unit area on the sample, and determine, based on the count of needle holes, the knit density.

In some embodiments, if the count of needle holes per unit area is greater than 30 stitches/cm, the knit density is classified as high density. If the count of needle holes per unit area is between 15 stitches/cmand 30 stitches/cm, the knit density is classified as medium density. If the count of needle holes per unit area is less than 15 stitches/cm, the knit density is classified as low density.

In some embodiments, the processor may determine the pile thickness based on a height of the polyester textile. For example, the processor may measure the height of the polyester textile using a laser rangefinder or the like. If the height is less than 30 cm, the pile thickness classified as low thickness. If the height is between 30 cm and 50 cm, the pile thickness is classified as medium thickness. If the height is greater than 50 cm, the pile thickness is classified as high thickness.

In some embodiments, the preprocessing manner may include at least one of surface modification, microencapsulation, carrier integration, plasma processing, hybrid processing, etc. The hybrid processing may be a combination of the surface modification and the microencapsulation, a combination of the surface modification and the plasma processing, or the like.