How are bio-based chemical fibers processed?
The representatives of traditional bio-based virgin fibers, that is, natural fibers, are cotton fibers and mulberry silk. The history of producing cotton fiber and mulberry silk textiles in my country has lasted for thousands of years. "Silk satin" is used to describe the exquisite and high-grade quality of silk fiber textiles, and it was a symbol of power and wealth in ancient times.
The production of cotton fiber and mulberry silk mainly uses cotton and silk as raw materials, and is mainly prepared by various physical means. In the early days of liberation in my country, the handmade "bounce cotton" widely used by the people was the process of physically classifying cotton seeds and cotton fibers and further processing them into fiber products.
So, how are today's bio-based chemical fibers processed and prepared from biomass?
The representative of the direct solvent method is the development of a new solvent system represented by N-methylmorpholine-N-oxide (NMMO). The NMMO production process is a process of preparing cellulose fibers without chemical reaction. First, the pulp and NMMO containing crystal water are fully mixed and swelled, and then most of the crystal water is removed under reduced pressure and dissolved to form a stable, The transparent and viscous spinning stock solution is spun after filtering and defoaming.
It has the advantages of short process flow, small pollution and good solubility. The regenerated cellulose fiber produced by the NMMO method is called "Lyocell fiber" (Lyocell), which is known as the green fiber of the 21st century.
The representative of the direct solvent method is the development of a new solvent system represented by N-methylmorpholine-N-oxide (NMMO). The NMMO production process is a process of preparing cellulose fibers without chemical reaction. First, the pulp and NMMO containing crystal water are fully mixed and swelled, and then most of the crystal water is removed under reduced pressure and dissolved to form a stable, The transparent and viscous spinning stock solution is spun after filtering and defoaming.
It has the advantages of short process flow, small pollution and good solubility. The regenerated cellulose fiber produced by the NMMO method is called "Lyocell fiber" (Lyocell), which is known as the green fiber of the 21st century.
It can be seen from the above content that the solvent method can omit a series of chemical treatment processes, shorten the production process and reduce pollution. At present, researchers at home and abroad are working on the development of other solvent systems.
Other solvents include ionic liquid and low temperature alkali/urea system, among which the low temperature alkali/urea system is a cellulose dissolving system independently developed by my country.
The research on the cleaning process of cellulose fibers also includes the melt-spinning method of cellulose esters, that is, the fiber raw materials are prepared by derivatization of biomass raw materials, and then melt-spun. However, due to the complex chemical structure of natural biomass raw materials, including multiple hydroxyl functional groups, it is prone to high temperature degradation. Although the process has been reported, it has not yet become a commercial product.
(2) Processing of bio-based synthetic fibers
The processing process of bio-based synthetic fibers is similar to the preparation process of traditional polyester, nylon and other fibers. They are mainly prepared into slices by melt polymerization, and then the fibers are prepared by melt spinning process. With the further development of the process, the melt direct spinning process can also be developed.
Taking polylactic acid as an example, the monomer of polylactic acid is lactic acid, or lactide prepared by the dimerization and cyclization of lactic acid, which can be obtained by biological fermentation from crops such as corn, potato and sugar beet. The output of these crops in our country is very large, so the development potential of polylactic acid fiber in our country is great. The production of polylactic acid chips mostly adopts a two-step method. First, lactic acid is polycondensed to form oligomers, then lactide is prepared under the action of a catalyst, and then polylactic acid is prepared by catalytic ring-opening polycondensation after distillation and purification in a vacuum.
Further using slices, through the melt spinning process, polylactic acid fibers of various specifications can be prepared for downstream market applications. The processing process of bio-based synthetic fibers is similar to the preparation process of traditional polyester, nylon and other fibers. Both are prepared into slices by polymerization, and then the fibers are prepared by melt spinning process. With the further development of the process, the melt direct spinning process can also be developed.
