Flushable Nonwoven Material Processing Technology
With the rapid improvement of people's living standards and the continuous advancement of science and technology, people's living habits are constantly changing. Wet wipes have gradually become an indispensable cleaning and hygiene product in people's lives. Especially since the outbreak of the new coronavirus pneumonia, the usage of cleaning, hygiene and disinfection wipes has increased rapidly. As the use of disposable sanitary products continues to increase, while they bring healthy and convenient life to people, they also slowly bring about some environmental problems. The annual consumption of wet wipes places a huge burden on the environment. Especially since the invention and marketization of wet toilet wipes, how to better adapt to usage scenarios and comply with the requirements of municipal sewage facilities such as drainage pipes has become a focus of the market. This has also affected the flushability and flushability of flushable wet wipes products. Indicators such as degradability have put forward higher requirements.
There are three main web-forming processes for flushable nonwovens: carding, air-laid and wet-laid. Currently, the wet-laid spunlace reinforcement process is the fastest growing and most used in the world.
Carding into a web generally requires longer fiber lengths, and functional fibers are often used for production. With the continuous improvement of flushability standards, it is difficult for carded web products to pass flushability testing. The flushability produced by this process The product has been gradually eliminated from the market. Air-laid transports the carded single fibers to the receiving curtain through airflow, and finally forms a fiber web. Compared with carded web, the fiber arrangement is more random, and the mechanical properties basically show isotropic characteristics. Wet laying is similar to the papermaking process. Fiber and water are beaten in a beater in a certain proportion to form a slurry, which is then evenly coated on the mesh curtain. After removing excess water, a fiber web is formed. The fibers used in the wet-laid process are the shortest in length among the three web-laying methods, and their uniformity is relatively better.
The fibers prepared through the above three web-forming methods also need to go through the most important process, which is to reinforce the fiber web, so that the flushable nonwoven products not only have better wet usability, but also have flushability. Dispersion performance. Currently, three common reinforcement processes for flushable nonwovens include chemical bonding, thermal bonding and spunlace. The key to strengthening flushable nonwovens by chemical bonding is the use of special adhesives, which are required to be dissolved under the shear and erosion of water flow, and the fibers become dispersed. The type of adhesive used in this method plays a decisive role in the flushability of the product. The safety and irritation of chemical reagents are also important considerations.
Thermal bonding flushable nonwovens are made by mixing a small amount of heat-meltable fibers and cellulose fibers into a fiber web. The fibers are melted by hot rolling or hot air heating to bond and strengthen the cellulose fibers. Fibers that can be heated and melted generally include ES fiber, polylactic acid fiber (PLA), polyethylene fiber and polypropylene fiber. However, hot-melt fibers are generally not 100% biodegradable. If used in large quantities, non-degradable fibers will accumulate in the sewage treatment system, increasing the burden of sewage treatment. However, with the development of degradable PLA, polybutylene terephthalate-adipate (PBAT) and other materials, fully degradable materials using thermal bonding methods will also have good room for development.
Hydroentanglement reinforcement can strengthen the fiber web formed by the three web-forming methods mentioned above. It uses high-pressure water jet to hydroentangle the fiber web. The fibers in the fiber web are displaced under the puncture of the water jet. At the same time, part of the water jets are re-ejected and pierced the fiber mesh under the blocking effect of the net curtain, causing the fibers to shift, cling and entangle with each other, and the fiber mesh is reinforced. Spunlacing reinforcement is a kind of physical and flexible reinforcement that does not damage the fibers, and the product also has higher safety. The spunlace reinforcement method requires appropriate spunlace process parameters to ensure a low loss rate during the production process and a suitable degree of entanglement of ultra-short fibers, and the final product has suitable wet strength and flushability.