Melt Filter Processing In Nonwoven Fabric Production
June 13, 2022
One way to ensure the cleanliness of materials in the production of nonwoven fabric is to use a filtration system. This article introduces two German - made filters. When they replace the filter, the process does not fluctuate. At the same time, they can be directly produced using recycled filter cloth material to reduce costs.
In the process of spunbond production of non woven fabric roll, the processes of fiber drawing and non woven fabric formation are combined into one. The polymer raw material enters the spinneret in a molten state through an extruder, and then directly enters the conveyor belt after spinning, and finally forms a nonwoven fabric.
After being mixed and fed, the spunbond technology slices produced by the nonwoven fabric of the spunbond production line enter the extruder, pass the filter, and enter the melt pump in the melt state. Usually. Filters and other components are installed in the filter to block impurities in the melt and avoid entering downstream equipment.
For the filter, the most important requirement is that during the filter replacement screen, it will not cause adverse effects on production and will not cause interruption or reduction of materials. The melt pump can enhance the melt pressure and ensure the stable delivery of melt material.
According to this process, fiber spinnerets have different design methods. Generally, the spinneret system is equipped with many melt pumps, which need to ensure that the spinning can proceed smoothly.
The spinneret system design and precise control can ensure that the melt passing through the spinneret is stable and free of fluctuations. In addition, there are filters in the spinneret to ensure that the melt is uniform and clean. The filter of the spinneret is composed of multiple layers of woven mesh, and the residual impurities in the melt are blocked by it, so the filter mesh needs to be replaced regularly.
When replacing the spinneret filter, the work of this station needs to be stopped, and sometimes the entire production line needs to be stopped. The finer the filter, the longer the life of the spinneret. Therefore, the filter before the spinneret should remove as much impurities as possible in the melt to increase the service life of the filter.
Spunbond process flow In the melt spinning process, the melt is injected directly into the hot high - speed air flow, the melt changes from liquid to fibrous, and the diameter of the fiber is 0.5 ~ 30 um, usually 2 ~ 7 um. The fiber and the hot air enter the accumulation net together, and are cooled and solidified after contact with the cold air.
Fluctuation of the air flow causes the fibers to be randomly oriented, and the randomization of the fiber orientation is precisely the requirement of the nonwoven fabric melt - spinning process. Therefore, it can meet the homogenization requirements of non woven fabric production. These opaque nonwoven fabrics have low tear strength, large surface area, and insulation and filtration properties.
The salient feature of the melt spinning process is that the melt is heated to a higher temperature. Therefore, the design of the melt flow channel, 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 are dead corners, the melt will be thermally degraded. If the degraded material enters the spinneret, it will form holes or black lumps in the final product. This will have to stop the entire production line to clean the conveyor belt.
In the process, the filament enters the cold air zone after being extruded. At this time, due to changes in the air flow and static electricity, the fibers do not stick together.
The non woven fabric stacking process occurs in the perforated stacking belt. The stacking belt is transported until the nonwoven fabric is rolled and packed. The diameter of the single filament is 15 ~ 35um. Similar to the melt spinning process, the fiber structure is disordered, but it is light, warm and highly absorbent. Compared with other fabrics, nonwoven fabrics have excellent tensile strength per unit density / weight, and are mainly used in waterproof sealing materials, sanitary products or geotextiles, such as preventing water and soil loss.
In the " Reicofil " process, air is spread throughout the woven fabric, and in subsequent processes, the fibers are separated and mixed by cyclones.
The production line provided by Neumag, part of the Saurer Group, to Turkey uses ASON Spunbound technology. Due to the variable position of the spinneret, syringe and stacking belt, production flexibility is greatly enhanced. Therefore, a single production line can produce many kinds of products, and the switching time is very short. At the same time, you can also use different non woven fabric raw material, such as composite fibers and polyester materials that are growing rapidly in the nonwoven fabric market.
Stacking of nonwoven fibers The filtration system in the production of nonwoven fabrics In the production process of non woven fabrics. The role of the melt filtration system is to remove impurities in the melt and protect the spinneret. Because even small impurities may force the spinneret to be replaced, causing the entire production line to shut down. At the same time, the breakage of each fiber can cause defects and irregularities in the nonwoven fabric. In addition, in the fiber spinning process, the frequency of spinneret replacement is also low.
The requirements for the fineness of filtration depend on the structure and application area of the nonwoven fabric. For geotextile fabric products, impurities that are visible to the naked eye are allowed. And for medical supplies, any tiny impurities must be removed. The filter fineness of the spinneret filter is determined by the final product and the diameter of the fiber, usually 20 ~ 75 um.
In most cases, the replacement of the spinneret filter can only be performed during the stoppage of the production line, while the pressure is released through the upstream melt filter. Generally, the filtration fineness of the upstream melt filter is equal to or finer than that of the spinneret filter, so as to prolong the life of the spinneret.
When selecting the filter type, it must be considered that the filter will not have any effect on the melt characteristics. Dead corners, long residence time, air entering the filter or oxidized melt may cause polymer degradation, change raw material characteristics and cause product quality defects, so they must be shut down to clean.
On the other hand, the increase in raw material prices and operating costs requires that the economic factors of the filtration system must be taken into consideration. Prolonging the screen change time of the spinneret filter and improving product quality can save costs. At the same time, investment and operating costs must also be considered.
In addition, it is important to consider whether recycled materials can be used. Since raw materials account for a large proportion of the entire production cost, the use of cheaper recycled materials can quickly recover investment. Generally, the investment filter's recovery period should be less than 12 months .
Non woven fabric production requires continuous process and stable pressure to ensure continuous spinning process. The filter developed by Gneuβ in Germany has a large filtration area of the melt flow channel, and adopts the rotary filtration technology with patented technology.
