Melt filtration processing in non-woven fabric production

One of the methods to ensure the cleanliness of materials in the production of non-woven fabrics is to use a filtration system. This article introduces two filters made in Germany that do not fluctuate when the filter is replaced, and can be directly produced using recycled materials to reduce costs.
In the process of producing a nonwoven fabric by the spunbonding method, the fiber spinning process and the nonwoven fabric forming process are combined. The polymer raw material enters the spinneret through the extruder in a molten state, and then directly enters the conveyor belt after spinning to form a nonwoven fabric.
The spunbond process chips produced by the spunbond line non-woven fabric are mixed and fed, then enter the extruder, and then pass through the filter to enter the melt pump in a melt state. Typically, the filter is filled with components such as filters to block impurities in the melt and prevent entry into downstream equipment.
For the filter, the most important requirement is that during the filter replacement process, there is no adverse effect on the production and no material interruption or reduction. The melt pump enhances melt pressure and ensures stable delivery of the melt material.
According to this process, fiber spinnerets have different designs. Typically, the spinneret system is equipped with a number of melt pumps that ensure smooth spinning.
The spinneret system design and precision control ensure smooth, non-fluctuating melt through the spinneret. In addition, there are filters in the spinneret to ensure uniform and clean melt. The filter of the spinneret consists of a multi-layer mesh, in which residual impurities in the melt are blocked, so that the filter is periodically replaced.
When replacing the spinneret filter, it is necessary to stop the work of this station, and sometimes it is necessary to stop the entire production line. The finer the filter, the longer the life of the spinneret. Therefore, the filter before the spinneret should remove as much impurities as possible from the melt to increase the life of the filter.
In the spunbond process, the melt is directly injected into a hot high-speed air stream, and the melt is changed from a liquid to a fiber. The diameter of the fiber is 0.5 to 30 um, usually 2 to 7 um. The fibers enter the stacking net together with the hot air, and are cooled and solidified after contact with the cold air.
The fluctuation of the air flow causes the fibers to be randomly oriented, and the randomization of the fiber orientation is the requirement of the non-woven melt spinning process, and therefore, the homogenization requirement of the nonwoven fabric production can be satisfied. These opaque nonwovens have low tear strength, large surface area and insulation, and filtration properties.
A significant feature of the melt spinning process is that the melt is heated to a higher temperature, so the design of the melt runner, the internal structure of the spinneret and the optimization of the melt flow are very important.
If the melt flow rate is too low or there is a dead angle, the melt will be thermally degraded. If the degraded material enters the spinneret, it will form holes or black blocks on the final product, so the entire production line will have to be stopped to clean the conveyor belt.
In the process, the filaments are extruded into the cold air zone, and the fibers do not stick together due to changes in air flow and static electricity.
The non-woven fabric stacking process takes place in a porous packing belt, which is conveyed until the non-woven fabric is wound and packed, and the diameter of the single filament is 15 to 35 um. Similar to the melt spinning process, the fiber structure is disordered, but light, warm and highly absorbent. Compared with other fabrics, non-woven fabrics have excellent tensile strength per unit density/weight, and are mainly used for waterproof sealing materials, sanitary products or geotextiles, such as preventing soil erosion.
In the "Reicofil" process, air is distributed throughout the woven fabric, and in subsequent processes, the fibers are separated and mixed by cyclone.
The production line supplied to Turkey by Neumag, a subsidiary of Saurer, uses ASON Spunbound technology. Production flexibility is greatly enhanced due to the variable position of spinnerets, syringes and stacking belts. As a result, a single line can produce a wide range of products with very short switching times. At the same time, it is also possible to use different raw materials, such as composite fibers and polyester materials which are currently growing extremely rapidly in the nonwovens market.
Filtration system in the production of non-woven fabrics of non-woven fabrics In the production process of non-woven fabrics, the function of the melt filtration system is to remove impurities in the melt and protect the spinneret. Because even small impurities can force the replacement of the spinneret, causing the entire line to stop. At the same time, the breakage of each fiber can cause flaws and irregularities in the nonwoven fabric. In addition, in the fiber spinning process, the spinneret replacement frequency is also required to be low.
The requirements for the fineness of the filtration depend on the structure and application of the nonwoven fabric. For geotextile products, visible impurities are allowed, and for medical products, any tiny impurities must be removed. The fineness of the spinneret filter is determined by the diameter of the final product and fiber, typically 20 to 75 um.
In most cases, the filter that replaces the spinneret can only be stopped during the production line and is relieved by the upstream melt filter. Typically, the filtration fineness of the upstream melt filter is comparable to or finer than the filtration fineness of the spinneret filter to achieve extended spinneret life.
When selecting a filter type, it must be considered that the filter does not have any effect on the melt characteristics. Dead spots, excessive residence time, air entering the filter or oxidized melt can cause polymer degradation, change in material properties and product quality defects, and must be shut down for cleaning.
On the other hand, the rise in raw material prices and operating costs requires that the economic factors of the filtration system must be considered, and the time required to extend the screen change of the spinneret filter and improve product quality can save costs. At the same time, investment and operating costs must also be considered.
In addition, the important consideration is whether the recycled materials can be used. Since the raw materials account for a large proportion of the total production cost, it is more efficient to use the cheaper recycled materials to recover the investment quickly. Generally, the investment filter should be collected for less than 12 months. .
Non-woven production requires continuous process and pressure stability to ensure continuous spinning. Filter developed by Gneuβ, Germany, with large melt channel filtration area and patented rotary filtration technology