With the development of social economy, people's demand for textile products is also increasing, the problem of waste textiles is becoming more and more prominent, and it is urgent to carry out reasonable recycling of waste textiles. Single-component polyester or cotton fabrics are relatively easy to recycle, but polyester/cotton blended textiles are still difficult to be recycled, which is being paid attention by many scholars and enterprises, and the research on its separation method has become a hot topic in this field.
Currently, the commonly used methods of recycling waste polyester/cotton fabrics include physical and chemical methods. Among them, the physical method refers to the use of mechanical external forces on the waste material without changing the chemical structure of the fiber, open, remove impurities and other processes, and then processed into textiles, the resulting product is usually low value-added; the chemical method is a component of the dissolution or degradation into oligomers, or depolymerization into small molecules, and then through the polymerization, spinning and other processes to achieve the reuse of the product is usually able to obtain a higher value-added products. The products with higher value-added can usually be obtained.
The following mainly introduces several commonly used chemical methods for separating polyester and cotton fibers in waste polyester/cotton blended textiles.
Alcoholysis
Alcoholysis is the degradation and removal of polyester by depolymerizing agent under certain temperature and catalytic conditions, leaving only single-component cotton fiber to achieve the purpose of polyester/cotton separation. There are many depolymerizing agents commonly used in the process of alcoholysis, among which ethylene glycol is the most commonly used.
Ionic liquid dissolution
The ionic liquid dissolution method usually involves making one component completely dissolved in the ionic liquid without degradation, and the other component is retained and separated. Waste polyester/cotton blended fabrics were separated by ionic liquid 1-butyl-3-methylimidazolium chloride salt ([BMIM]Cl), and cotton fibers were dissolved and converted to solid cellulose, while polyester was separated as insoluble without significant changes in its properties.
Hydrothermal
Hydrothermal method refers to the dissolution and recrystallization of some insoluble or insoluble substances under high temperature and pressure. The use of polyester/cotton acid and alkali resistance is different, in a certain component to maintain a stable state, the other component will be hydrolyzed into monomers, so as to achieve the separation of cotton fibers and polyester.
Through comparison, it is found that each method requires the use of chemical reagents, and the subsequent treatment of its residual liquid will have a certain impact on the environment and even harm; each method has certain application prerequisites, so the recycling of waste polyester/cotton fabric should be considered as a combination of solutions, in order to improve the efficiency of the recycling of waste fabrics and at the same time minimize the secondary pollution of the environment.