Introduction to Nonwoven Materials and Engineering Professional Courses-Compulsory Course for Nonwovens

1. Introduction The four technological processes included in the principle of nonwoven production and the definition of nonwovens. Familiar with the applications of durable nonwovens and disposable nonwovens, and the classification method of nonwovens. Understand the fibers used in non-woven fabrics, and focus on understanding the hot melt adhesive fibers. Understand the production method of microfiber. Understand wood pulp fiber and polylactic acid fiber. Understand the application of nonwoven materials. 1. Nonwoven production principle: Four production processes: fiber/raw material preparation, web formation, web reinforcement, finishing and forming. (1) Fiber/raw material preparation: fiber (main body); adhesives, finishing chemicals (auxiliary materials), polymers, etc. (2) Netting: The fibers are formed into a loose fiber layer structure. (3) Fiber web reinforcement: Reinforce the loose fiber layer through related processes and give it physical and mechanical properties. (4) Finishing and forming: improve the structure, feel and performance of the product, and transform it into the final product on the forming machine. 2. The definition of non-woven fabric: oriented or randomly arranged fibers are combined by friction, entanglement or bonding or a combination of these methods to make sheets, webs or pads (excluding paper, woven fabric, tufts) Fleece fabrics, stitched fabrics with stitched yarns and wet felted felts). The fiber used can be natural fiber or chemical fiber; it can be short fiber, filament or fibrous material formed on the spot. 3. Durable non-woven fabric Non-woven fabric that has been used repeatedly or has a certain service life. 4. Disposable nonwovens refer to disposable nonwovens. In fact, they can be used more than once, even as many as 4 to 5 times. 5. Classification of non-woven fabrics ① 　Fabric forming methods: dry-laid, wet-laid, and spun-laid ② Classification by use (1) Medical and health care (2) Clothing and footwear (3) Household Decoration (4) Industrial cloths (5) Civil engineering (6) Others 6. Fibers used in non-woven fabrics The fibers used can be natural fibers or chemical fibers; they can be short fibers, filaments or fibrous objects formed on the spot. Almost every known raw material can be used in nonwoven production. Textile scraps are difficult to spin and process fibers, such as glass fiber, metal fiber, etc. Some new types of chemical fibers, such as high temperature resistant fibers, ultra-fine fibers, etc. 7. Hot-melt bonding fiber (hot-melt) bonding fiber: The fiber that bonds and consolidates the fibers in the web after being heated and melted and cooled. The fibers produced by the melt spinning method are all, but some fibers have high melting points. Low melting point binder fiber: low melting point, wide softening temperature range, small shrinkage when softened. The most commonly used low-melting bonding fibers are polypropylene and ES fibers (PP/PE composite fibers). When hot-melt bonding, the ES fiber content in the web must exceed 50%, and thin products can use 100% ES fiber. 8. Production method of superfine fiber. Fiber with fineness below 0.44dtex (0.4d). There are two main production methods: composite spinning technology: first make two-component composite fiber (sea-island type or orange petal type) and make it into traditional fabric or non-woven fabric, and then use mechanical or chemical methods to process to form ultra-fine Fiber products. Melt-blown non-woven technology: directly obtain non-woven materials composed of ultra-fine fibers, with an average fiber diameter of 2 to 5 μm. Microfiber non-woven fabric can be used as filter material, synthetic leather base fabric, etc. 9. Wood pulp fiber and polylactic acid fiber l Wood pulp fiber, also called fluff pulp fiber, is a natural cellulose fiber made from logs. l Fluff pulp fiber production: wood → cut into small wood chips → high temperature and high pressure cooking with chemicals (removing lignin and extractables) → bleaching and mechanical screening and cleaning → cellulose pulp → dehydration and drying into pulp board l fluff pulp The main difference between fiber and wood pulp fiber for papermaking: A. The average length of fluff pulp fiber is 2mm, and the average length of wood pulp fiber for papermaking is 1mm. B. The residue of extractables in wood pulp fibers for papermaking is relatively large, which affects its hygroscopicity. C. Wood pulp fibers for papermaking usually have a higher moisture content. The production process of polylactic acid fiber: corn→starch→glucose→lactic acid→high-purity polylactic acid→polylactic acid fiber. Polylactic acid fiber is biodegradable and renewable. It is a kind of green fiber. Application of Polylactic Acid Fiber (PLA)