In recent years, bio-based fibers have been increasingly widely used in non-woven materials. According to the source of raw materials and production process, they can be divided into four major categories. Table 1 shows the main applications of this type of fibers in non-woven materials.
Table 1 Classification of bio-based fibers and their nonwoven materials
1 Regenerated cellulose fiber and its nonwoven materials
Regenerated cellulose fibers can be made into non-woven materials through needle punching, spunlace, thermal bonding and other methods, and can be used in personal hygiene care, filtration and other fields. Viscose fiber has good hygroscopicity, softness and entanglement properties, and is widely used. However, its wet strength is low, so it is often mixed with other fibers to make nonwoven materials. Through the spunlace process, it can be mixed with wood pulp fibers to make flushable wet wipes, and mixed with other chemical fibers to make facial mask base fabrics, car interiors, etc. In addition, viscose fiber can also be made into filter material through acupuncture process. For example, if it is mixed with chitosan, the prepared material has antibacterial properties and is an excellent dressing material; it can be combined with hemp fiber and PA6 nanofiber The multi-layer nonwoven material prepared by mixing has better oil absorption and filtration performance than ordinary filter materials.
Lyocell fiber has good moisture absorption and breathability, and can be used to prepare nonwoven materials through hydroentanglement, acupuncture, melt-blown and other processes, and can be used as filter materials, facial mask substrates, biological tissue engineering materials, etc. For example, a filter material prepared by mixing Lyocell fiber and viscose fiber through a needle punching process has better adsorption performance and a larger specific surface area than a material prepared from pure viscose fiber. Japanese patent (Patent No. JP 2014073432-A) discloses a method for preparing filter materials. A fiber web made of fibrillated Lyocell fiber and a fiber web made of chemical fiber short fibers with a diameter of 1 to 8 μm are combined. Nonwoven filter materials can be made through a thermal bonding process; patent US 2013269294 A1 discloses a multi-layer nonwoven material prepared by nano-Lyocell fiber, ultra-fine fiber and hot-melt fiber, with nano-level Lyocell as the top layer of the material. The content is 40% to 80% of the total weight. Ultrafine short fibers are used as the base layer of the material, and the content is about 20%. Polyester fiber, polypropylene fiber, polyurethane fiber, etc. can be used. The material weight is 65 to 113 g. /m2, this material can be used for the preparation of disinfection materials and packaging bags.
Although viscose fiber and Lyocell fiber have good physical properties and the spunlace nonwoven materials made from them are very comfortable for the human body, the uses of their products are relatively single and not diverse enough. To make its application fields wider, its processing methods should be further explored to make the products more diversified.
2 Regenerated protein fiber and its nonwoven materials
Because regenerated protein fibers are limited by their mechanical properties, they can only be made into nonwoven materials through processes such as spunlace and needle punching. The prepared materials have good skin-friendliness and comfort, good compatibility with the human body, and can be used for hygiene. Nursing field, bioengineering field, etc.
Collagen fibers can not only makeHydroentangled nonwoven materials are prepared, and cartilage tissue can also be prepared through a needle punching process. However, the mechanical properties of collagen needle-punched materials are low, so the mechanical properties of the cartilage tissue made from them are also at a low level. In addition, collagen nanofibers can also be prepared by electrospinning and used to prepare biological scaffold materials. Its outstanding advantage is that it can enhance the biochemical properties of the material without damaging its mechanical properties.
It takes about 60 hours to obtain regenerated protein fiber by wet spinning. The production line is too long, consumes a lot of energy, and requires a lot of chemical reagents in the production process, which causes relatively large environmental pollution. In addition, the strength of the fiber obtained is also low, which is not conducive to production and processing, and requires post-processing before it can be used in the textile field. Therefore, further research on regenerated protein fibers with a more environmentally friendly and energy-saving production process is a breakthrough. Patent US 20130256942 A1 introduces a more energy-saving and environmentally friendly method of producing milk protein composite fibers. This patent uses a melt spinning process to plasticize proteins extracted from milk together with a plasticizer at a temperature between room temperature and 140°C, and then extrusion under a certain pressure to obtain milk protein composite fibers. , the plasticizer can be water, glycerol, polysaccharides, etc.
3 Bio-based synthetic fibers and nonwoven materials
PLA fiber has good biocompatibility and biodegradability. It can be formed into a web by dry method, spunbond method, melt-blown method, and then reinforced by needle punching and thermal bonding methods to form non-woven materials for medical and packaging applications. Materials, filter materials, agricultural materials and other fields.
PLA and flax fiber are mixed, and non-woven materials are prepared using air-laid and hot-rolling processes. The product not only has good biodegradability, but also has certain physical and mechanical properties and can be used for packaging materials, etc. Although PLA has good biocompatibility and degradability, it does not have antibacterial properties, which also limits its application. If the prepared melt-blown PLA material is antibacterially finished with a halamine compound, the material can be used to make medical and sanitary products, filter materials, etc.
PLA has excellent biodegradability, so it can also be used as a covering film for crops. At present, a research team has prepared a PLA/PHA composite nonwoven material. Through weathering simulation tests, it has been determined that this material can be used as a multi-season biocompost covering material and is a good alternative to traditional agricultural coverings. choose.
In addition, the PLA nanofibers produced by electrospinning are directly compounded on spunlace nonwoven materials and melt-blown nonwoven materials to make PLA nanofiber nonwoven composite materials. The filtration performance of the material will be greatly improved; melt-blown nonwoven materials will be After electret treatment of PLA nonwoven materials, the filtration performance of the material can also be significantly improved, but the filtration resistance will not change much. Some researchers pointed out that although a single PLA melt-blown nonwoven filter material has high strength, it has poor flexibility. If PLA/PCL composite melt-blown nonwoven material is used, it can maintain the filtering effect and strength while maintaining the filtering effect. Flexibility will also be enhanced.
Although PLA nonwoven materials have good biodegradability and biocompatibility, their production process is not completely green, and due to limitations of their own physical properties, the application fields of nonwoven materials are limited. PLA fibers can be further optimized in the future. The production process makes it greener; it can also further improve the performance of PLA and make the materials it prepares have a broader application field.
4 Marine bio-based fibers and their unique characteristicsConstruction materials
Marine bio-based fiber refers to fiber raw materials that come from animals and plants in the ocean, such as algae, shrimp, crab shells, etc. This type of fiber generally has good physical and chemical properties, biocompatibility, antibacterial properties, etc. Nonwoven materials can be prepared through the needle punching process and are generally used in the field of medical dressings; nonwoven materials prepared through the spunlace nonwoven process are generally used. Used in personal hygiene materials, such as facial masks, diapers, etc.; micro-nano fibers spun through electrospinning can be used in the development of biological tissue engineering materials.
4.1 Alginate fiber
Seaweed fiber is often made by blending and spinning alginate and non-alginate polymers (such as cellulose), and has good applications in the medical field. For example, seaweed fiber prepared by using chitosan as a coagulant can be further prepared into medical dressings, which not only improves the strength of the dressing, but also improves its absorption performance. In addition to making dressings, seaweed fibers can also be used as materials for masks, tissue engineering composite scaffolds, etc.
Although seaweed fiber nonwoven materials have many uses, because the alginate aqueous solution is too viscous, even below the gel concentration, defects in the polymer chain and intermolecular repulsion will hinder the formation of fiber chains, making the seaweed fiber less durable. There are certain difficulties in processing. A new spinning method has been proposed in the literature. Microfluidic method can be used to continuously produce alginate filaments with grooves. This method is low-cost, simple to operate, and the fibers produced are also good biocompatibility. properties and can be used for the preparation of cell scaffold materials.
4.2 Chitosan fiber
Chitosan fiber has good antibacterial properties, degradability and biocompatibility. It is generally made into non-woven materials by needle punching process and can be used in biological tissues and filter materials.
Chitosan fiber can promote the rapid proliferation of fibroblasts, collagen synthesis and vascularization. Therefore, chitosan materials prepared by acupuncture technology are mainly used in the field of medical dressings, and their costs are low and their production speed is fast. The fiber can also be used to prepare filter materials. The filter media prepared by the wet-laying process has good filtration effects and can be used to replace wastewater and waste oil filter materials. Chitosan fibers produced by electrospinning can be further made into nonwoven materials due to their good adsorption properties and excellent filtration effects. For example, if nanochitosan/PEO fibers produced by electrospinning are combined with PP spunbond materials, the resulting materials can be used for liquid or air filtration.
Although chitosan fiber has many good properties, there are still some technical bottlenecks in the preparation process. For example, it is difficult to increase the degree of deacetylation, which limits the preparation of high-purity chitosan. Chitosan fiber has poor water solubility. It is difficult to achieve rapid bacteriostasis; it is difficult to mix, open, and card into webs, and the preparation of fiber webs is limited. If these problems can be solved, its application fields can be further expanded. At present, a team has studied methods to improve its water solubility, and the prepared succinyl chitosan is a water-soluble chitosan with better performance, good water solubility, and can be used to prepare foam dressings, etc.
Although marine bio-based fibers come from a wide range of raw materials and have good biocompatibility and degradability, some of their own performance characteristics also limit their development. Water such as alginate fiberThe performance of chitosan is too good, which makes fiber preparation difficult; chitosan fiber has excellent antibacterial properties, so most of it can only be used to prepare medical products. In addition, the suitable process method is relatively simple, and the applicable field of the product is also narrow, which has also become the direction of its future research.
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