Film cutting and twisting yarn is a new type of yarn forming process, which is to make sheet materials from polymers or short fibers, then cut them into narrow strips of a certain width, and then twist them into yarn. This method is an innovation in the traditional spinning form. It uses film-like materials instead of loose fibers as the spinning raw material, eliminating the need for spinning processes such as "cleaning, steel, and strips", further shortening the process, and can also achieve difficult-to-melt melting. , difficult to dissolve polymer into yarn. Depending on the form of the film, film cut and twisted yarn can be divided into polymer film cut and twisted yarn, nonwoven fabric cut and twisted yarn, and paper cut and twisted yarn (referred to as "paper yarn").
Polymer film slit and twisted into yarn
The technology of polymer film slitting and twisting into yarn was first developed by the Austrian company Lenzing in the 1920s, and it applied for a patent for the "cutting film cracking" method. This technology is widely used in the production of polyolefin materials. processing. Among them, polytetrafluoroethylene (PTFE) film slitting and twisting into yarn technology has the most in-depth research and the highest degree of industrialization.
The cross-section of the PTFE filament produced by the film cutting and twisting method is an irregular polygon, and the yarn surface is smooth and hairless. The stretching effect during film processing creates a large number of micropores on the surface of the film, which makes the final yarn also have a microporous structure. This structure can change the reflection, refraction, absorption, and scattering of light, giving the fabric a good gloss. . Because the macromolecules in the yarn are arranged more regularly and have a higher degree of orientation, the breaking strength of the yarn is higher, generally between 2 and 4.5 cN/dtex, and some are even as high as 6 cN/dtex. The linear density of the yarn has a wide range, generally between 90 and 2000 dtex.
PTFE material itself has the advantages of anti-oxidation, high temperature resistance, corrosion resistance, etc., and PTFE film-cut and twisted yarn has high tensile strength, large specific surface area, smooth surface, and is not easy to adhere to dust, so it is widely used in the production of smoke filter base cloth , long service life and good filtration effect.
Nonwoven fabrics slit and twisted into yarn
The yarn produced using the nonwoven slitting and twisting yarn technology has a uniform structure and stable quality; the yarn has a lot of hairiness and a strong sense of hair shape; there are a large number of pores inside, the volume density is low, and the hand feels fluffy. Yarns are generally thick, with linear density generally between 50 and 700 tex (a few yarns can be as low as 7.2 tex), high breaking strength and large elongation at break.
Thanks to its soft and fluffy feel and rich wooly feel, nonwoven slit and twisted yarn can be used to produce woven products, carpets, shoes, bags, clothing fabrics, etc. Japan's Asahi Kasei Company has explored nonwoven slitting and yarn cutting technology and launched a nonwoven slitting product series "SLARIT". Related products are for cutting nylon, polyester, polypropylene nonwovens, etc. into 3, 5, 10 mm strips, which can be used to produce flat yarn, fancy yarn, twisted yarn, etc.
Paper yarn has been produced in Japan as early as 1638. Paper with high fiber orientation is cut into narrow strips of about 2 mm, and then these narrow strips are twisted into yarn through a wooden spinning wheel or by hand. The paper used to produce paper yarn is long-fiber paper. The raw materials come from the bark of Pu tree, mulberry tree, wild goose bark, Sanya, etc., so the paper is thicker and has better toughness. As the mechanization of the papermaking industry increases, machine-made paper gradually replaces hand-made paper, and papermaking raw materials gradually evolve into Manila hemp, mulberry bark, chemical fiber, etc., and sometimes some wood pulp and waste paper are also used.
The production process of paper yarn is basically similar to that of slitting and twisting nonwoven fabrics into yarn. Both short fiber films are cut into narrow strips and then twisted into yarn. Compounding paper yarn with other yarns (such as polyester yarn, nylon yarn, etc.) can improve its breaking strength and elongation at break, and reduce breakage during the weaving process. Post-finishing paper yarn with silicone oil or glycerin can reduce its surface roughness and improve its weavability.
Paper yarn can be used to produce clothing fabrics and decorative fabrics. When weaving, the warp yarns can be made of cotton, wool, silk, linen, etc. Paper yarn is generally used as weft yarn. Since the tensile strength of paper yarn is lower than that of cotton yarn, the weft insertion speed of paper yarn is about 90% of that of cotton yarn at the same count.