Disclosure of Invention
The invention aims to solve the defects of the existing polyester-cotton textile recycling technology, and separates and recycles the waste polyester-cotton textiles by taking biodegradable organic acid from the nature as a catalyst and matching with a hydrothermal reaction method, and does not cause secondary pollution to the environment.
In order to achieve the aim, the invention provides a method for separating and recovering waste polyester-cotton textiles by a hydrothermal reaction catalyzed by organic acid, which comprises the following steps:
cutting waste polyester-cotton textiles into fragments, and dispersing the fragments in an aqueous solution system of an organic acid catalyst to obtain a mixed system;
heating the mixed system to 110-180 ℃ in a high-pressure reactor to enable the cotton fibers in the waste polyester-cotton textiles to undergo degradation reaction for 0.5-3h to obtain a mixture; and
and filtering the mixture by using a screen, cleaning to obtain a polyester fiber aggregate, performing vacuum filtration on the rest part by using a filtering membrane, and cleaning to obtain cotton fiber fragments.
In one embodiment of the process of the present invention, the organic acid is methanesulfonic acid, oxalic acid, tartaric acid, citric acid, malic acid, formic acid or acetic acid, preferably methanesulfonic acid, oxalic acid, citric acid.
In another embodiment of the method of the present invention, the polyester content in the polyester-cotton textile is 1% to 99% by weight percentage.
In another embodiment of the process of the present invention, the aqueous system comprises from 0.1% to 30%, preferably from 0.5% to 10% by weight of the organic acid catalyst.
In another embodiment of the method of the present invention, the solid-to-liquid ratio of the mixed system is 1: 30-200, preferably 1: 50-150.
In another embodiment of the method of the present invention, the temperature of the mixed system is increased under stirring at a rate of 4 to 6 ℃/min.
In another embodiment of the process of the present invention, the mixed system is warmed to form an autogenous pressure, which is 0.10 to 1 MPa.
In another embodiment of the method of the present invention, the method further comprises drying the polyester fiber assembly and the cotton fiber pieces in a forced air oven to a constant weight, respectively.
In another embodiment of the method of the present invention, the method further comprises subjecting the polyester fiber assembly to a mechanical action to become a re-spinnable fiber raw material.
In another embodiment of the method of the present invention, further comprising reusing the cotton fiber pieces as a cellulosic production feedstock.
Compared with the prior art, the method for separating and recycling the waste polyester-cotton textiles through the hydrothermal reaction catalyzed by the organic acid has the advantages that the process is advanced and simple, the catalyst used in the process is from the nature and can be biodegraded, the catalyst cannot be decomposed in the process, secondary pollution to the environment cannot be caused, and the separation, recycling and reutilization of the waste polyester-cotton textiles can be efficiently realized.
Detailed Description
The technical solution of the present invention is further explained below according to specific embodiments. The scope of protection of the invention is not limited to the following examples, which are set forth for illustrative purposes only and are not intended to limit the invention in any way.
The method for separating and recovering the waste polyester-cotton textiles is realized by using hydrothermal reaction catalyzed by organic acid, and mainly comprises the following steps:
cutting waste polyester-cotton textiles into fragments, and dispersing the fragments in an aqueous solution system of an organic acid catalyst to obtain a mixed system;
heating the mixed system to 110-180 ℃ in a high-pressure reactor to enable the cotton fibers in the waste polyester-cotton textiles to undergo degradation reaction for 0.5-3h to obtain a mixture; and
filtering the mixture by a screen, cleaning to obtain a polyester fiber aggregate, performing vacuum filtration on the rest part by a filter membrane, and cleaning to obtain cotton fiber fragments.
Fig. 1 is a scanning electron microscope image of waste polyester-cotton textiles before treatment, as shown in fig. 1, in the method for separating and recovering waste polyester-cotton textiles of the present invention, the polyester-cotton textiles are fabrics woven by yarns blended from polyester and cotton fibers, the waste polyester-cotton textiles may be waste polyester-cotton textiles containing polyester content in any proportion, and the polyester content of the waste polyester-cotton textiles treated by the present invention is preferably 1% to 99% in terms of weight percentage, that is, the method is suitable for most of the polyester-cotton textiles.
The waste polyester cotton textile can be cut into pieces by cutting or shredding, and the size of the cut pieces is determined according to specific production conditions.
The organic acid mentioned in the invention refers to natural acid which comes from nature and can be biologically degraded, and can not be decomposed in the process of separating and recovering the waste polyester-cotton textile, and can not cause secondary pollution to the environment, such as methanesulfonic acid, oxalic acid, tartaric acid, citric acid, malic acid, formic acid, acetic acid, etc., preferably methanesulfonic acid, oxalic acid, citric acid.
The aqueous solution system of the organic acid catalyst is an aqueous solution formed by mixing organic acid (as a catalyst for subsequent degradation reaction) and water, wherein the content of the organic acid as the catalyst is 0.1-30% by weight, preferably 0.5-10% by weight, the content of the organic acid can accelerate the degradation reaction, so that the required reaction time is shortened, and in addition, the high content also can be beneficial to decomposing thicker clothes or clothes with tighter structure.
Dispersing waste polyester-cotton textile fragments in an aqueous solution system of an organic acid catalyst to obtain a mixed system with coexisting solid and liquid, wherein the solid-liquid ratio of the mixed system is 1: 30-200, preferably 1: 50-150, and the solid-to-liquid ratio is small, the reaction is relatively fast, and vice versa.
In order to degrade the cotton fibers in the waste polyester-cotton textiles, the mixed system is put into a closed high-pressure reactor, the temperature is increased to 110-180 ℃ at the temperature increase rate of 4-6 ℃/min under the stirring condition and is maintained for 0.5-3h, and the generated autogenous pressure (namely the pressure difference between the inside and the outside of the high-pressure reactor) is 0.10-1 MPa.
Under the subcritical hydrothermal condition, the cotton fibers can be subjected to degradation reaction, the polyester fibers are not affected, and the degraded cotton fibers are stripped from the textile in the form of fragments, so that the cotton fibers and the polyester fibers are separated. High temperatures or longer reaction times result in smaller sized cotton fiber pieces.
After cotton fiber and polyester fiber separate, retrieve polyester fiber and cotton fiber respectively through filterable mode, concrete step includes: filtering the mixture with a screen (such as a 20-mesh screen), cleaning to obtain a polyester fiber aggregate, vacuum-filtering the rest (the residual mixture after filtration) with a filtering membrane (such as PTFE (polytetrafluoroethylene) membrane), and cleaning to obtain cotton fiber fragments.
After the polyester fiber aggregate and the cotton fiber fragments are obtained, the polyester fiber aggregate and the cotton fiber fragments can be respectively dried in a blast oven to constant weight, and then the polyester fiber aggregate and the cotton fiber fragments are weighed to calculate the yield.
As shown in fig. 2-5, the product recovered by the method of the present invention, after being analyzed by Scanning Electron Microscope (SEM), fourier transform infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and recovery yield, is found to have a recovery rate of the polyester fiber aggregate of more than 95%, and not containing cellulose, the chemical properties thereof are basically preserved, and the polyester fiber aggregate can become a fiber raw material capable of being re-spun through mechanical opening and carding action (such as an opener, a carding machine, and the like), so as to realize the recycling of the polyester fiber; the recovery rate of the cotton fiber fragments is more than 80%, and the cotton fiber fragments do not contain polyester fibers, and can be reused as cellulose production raw materials, such as paper making raw materials entering a pulp mill.
In addition, the method does not involve the use of harmful chemical substances and a large amount of expensive solvents, but uses water as a reaction medium, and has extremely small catalyst dosage, thereby being beneficial to reducing the fiber recovery cost, improving the production efficiency and realizing the recovery and reutilization of the real green and environment-friendly polyester-cotton textiles.
Unless otherwise defined, all terms used herein have the meanings that are commonly understood by those skilled in the art.
The present invention will be further described with reference to the following examples.
Examples
The chemical reagents used in the following examples are commercially available and analytically pure reagents unless otherwise specified, and the procedures and instruments used in the following examples are those commonly used in the art unless otherwise specified. The proportions, ratios, contents, and the like described in the following examples are by weight unless otherwise specified.
Example 1
Putting 15g of waste white shirts with the ratio of polyester to cotton of 65/35 into 1.8L of aqueous solution with the citric acid content of 5%, heating the high-pressure reaction kettle to 130 ℃ at the heating rate of 5 ℃/min under the condition of stirring, and maintaining for 1.5h, so as to carry out degradation reaction on cotton fibers.
After the reaction is finished, the electric heater is closed, after the reaction kettle is cooled to room temperature, the reaction kettle is opened, and a reaction product is taken out.
Filtering the reaction product by a screen to obtain a polyester fiber aggregate, performing vacuum filtration on the residual mixed solution by a filter membrane to obtain cotton fiber fragments, cleaning the polyester fiber aggregate and the cotton fiber fragments, and drying the polyester fiber aggregate and the cotton fiber fragments in a blast oven to constant weight, wherein the recovery rate of the obtained polyester fiber aggregate is 98% and the recovery rate of the cotton fiber fragments is 83%.
Example 2
Placing 17g of waste bed sheet with the ratio of polyester to cotton of 20/80 in 1.5L of aqueous solution with the content of methanesulfonic acid of 1%, heating the high-pressure reaction kettle to 140 ℃ at the heating rate of 6 ℃/min and maintaining for 1h, and carrying out degradation reaction on cotton fibers.
After the reaction is finished, the electric heater is closed, after the reaction kettle is cooled to room temperature, the reaction kettle is opened, and a reaction product is taken out.
Filtering the reaction product by a screen to obtain a polyester fiber aggregate, performing vacuum filtration on the residual mixed solution by a filter membrane to obtain cotton fiber fragments, respectively cleaning the polyester fiber aggregate and the cotton fiber fragments, and drying the cotton fiber aggregate and the cotton fiber fragments in a blast oven to constant weight, wherein the recovery rate of the obtained polyester fiber aggregate is 99 percent, and the recovery rate of the cotton fiber fragments is 81 percent.
In conclusion, the method for separating and recycling the waste polyester-cotton textiles through the hydrothermal reaction catalyzed by the organic acid has the advantages that the process is advanced and simple, the catalyst used in the process is from the nature and can be biodegraded, the catalyst cannot be decomposed in the process, the environment cannot be polluted, and the separation, the recycling and the reutilization of the waste polyester-cotton textiles can be efficiently realized.
The embodiments described above are presented to enable those skilled in the art to make and use the invention. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the embodiments described herein, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.