my country is a major country in the production and application of chemical fibers in the world. In 2019, my country’s total chemical fiber output was 58.27 million tons, of which 47.51 million tons were polyester, accounting for 81.5% of the total chemical fiber output. Along with the huge production volume, the problem of waste pollution has become increasingly serious. Therefore, the development of recycled chemical fibers is an important way for my country’s chemical fiber industry and even the textile industry to achieve sustainable development. The following will take recycled polyester as an example.
Regeneration Polyester fiber production technology
Recycled polyester raw materials are currently mainly derived from waste polyester bottle flakes, sheets, films and polyester blocks and waste from polyester polyester production. Silk etc.
Waste polyester bottle flakes
The preparation method of regenerated polyester fiber can be mainly divided into For physical methods, chemical methods and physical chemical methods.
Physical method
The physical method refers to the recycling of waste polyester materials A regeneration method in which raw materials are directly used for melt spinning after sorting, cleaning, drying and other processes.
Brief process of physical method (using waste polyester bottles as raw materials)
Chemical method
Chemical method refers to the use of chemical reactions to depolymerize waste polyester materials into polymerized monomers or polymerized intermediates, and then purify and separate them. The steps are followed by a process of regenerative polymerization and melt spinning. Chemical recycling technologies currently on the market include processes such as glycolysis, methanolysis and alkaline hydrolysis.
Brief process of chemical method
Physics Chemical method
The physical and chemical method is a recycled chemical fiber produced by crushing and cleaning polyester waste (waste bottle flakes) and adding viscosity during the spinning process. The physical and chemical method perfectly combines the process advantages of physical recovery and chemical recovery.
The advantages and disadvantages of physical methods and chemical methods
Relatively speaking , the physical method is currently the dominant polyester regeneration method due to its simple production technology, short process flow and low production cost. More than 70% to 80% of the production capacity of recycled polyester fiber is recycled using the physical method. However, physical recycling methods are basically one-way recycling. Even food-grade bottle-to-bottle recycling technology cannot currently achieve complete closed-loop recycling of PET; due to the unstable dyeability, recycled polyester fiber is currently mainly used as some Non-clothing fabrics and home textile fabrics, such as filling fibers, clothing linings, home textiles, spray-coated cotton, packing tapes, non-woven fabrics and industrial fabrics, etc.; due to open-loop recycling, as the number of processing increases, polyester The inherent viscosity, molecular weight distribution and impurity content of the fiber will continue to change, and eventually it will no longer be possible to recycle it physically.
In recent years, chemical methods have shown a growing trend through innovations in equipment and processes. Its main advantage is that it can achieve complete recycling of waste polyester; the use of waste polyester Sorting and cleaning requirements are low. The raw material for the chemical method can be waste silk or even the polyester component of clothing. From a recycling perspective, chemical methods are more conducive to solving the problem of clothing waste. As the market’s requirements for various functionalities of polyester products increase, the use of non-single polyester material products increases rapidly. It is very difficult to recycle these products through physical methods. Only chemical recycling can solve these technical problems.
Related cases
Taiwan Far East New Century Company passed chemical glycolysis The solution involves glycolysis of PET to produce the oligomer BHET. After the glycolysis process, the oligomers are finely filtered and then repolymerized into PET; the regenerated PET is then spun into fibers.
Using glycolysis process to chemically recycle waste PET bottle flakes
Japan Teijin started to scale in 2002 Chemical uses chemical methods to produce regenerated polyester products. The glycolysis (ethylene glycol)/alcolysis (methanol) transesterification combined PET recycling process developed by it has the highest DMT monomer recovery rate, highest purity, and most stable quality. commercialization process route.
Teijin’s glycolysis (ethylene glycol)/alcohollysis (methanol) transesterification combined process flow
Ethylene glycol depolymerization is another major chemical recycling method for PET. At present, Japan’s Teijin, Goodyear, DuPont, Hoechst and Taiwan’s Far East Textile and other companies have realized the operation of commercial devices, and the process conditions are basically mature.
In 2013, the domestic Zhejiang Jiaren New Materials Co., Ltd. adopted Teijin’s chemical method (glycolysis/alcoholization transesterification combined PET recycling process) to regenerate polyester.Property.
Liquid-phase viscosification, homogenization and chain extension technology are physical and chemical methods that appear in the production process of recycled polyester fiber in my country. Process technology, it is said that this technology can produce products with physical performance indicators that are close to or even exceed those of virgin polyester fiber. In addition, the physical and chemical process technology also includes trace alcoholysis and alcoholysis repolymerization technology. Ningbo Dafa has been engaged in the research and development of regenerated polyester fiber since 2008, and has continuously upgraded its technology from liquid phase viscosity increasing, conditioning viscosity increasing, micro alcoholysis – conditioning viscosity increasing; in addition, Longfu Technology, Yangzhou Tianfu and You Enterprises such as Cai Environmental Protection have also adopted physical and chemical methods for the production of recycled polyester.
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