Do You Know A Special Dryer Fabric for Paper Machine Dryer Section?

A Special Dryer Fabric for Paper Machine Dryer Section

The fabric used in the dryer section of paper machine according to different machine speed, use position and paper kind usually includes: BOM dryer felt, polyester dryer fabric and flocking dryer fabric. The commonly used are BOM dryer felt and polyester dryer fabric, which are further divided into flat yarn dryer fabric, round yarn dryer fabric and spiral dryer fabric; And the flocking dryer fabric is a new type of dryer section fabric with composite properties, mainly used in the key dryer parts of medium and high-speed paper machines to produce medium and high-end paper types, especially some high-end thin special paper.

The full name of the flocking dryer fabric is polyester woven flocking dryer fabric. we classify them into two types: endless and seamed flocking dryer fabric; From the perspective of the felt layer, it can be divided into single-sided felt layer and double-sided felt layer. From the perspective of the felt layer, it can be divided into single-sided felt layer and double-sided felt layer flocking dryer fabric. The seamed type flocking fabric represents the high-end product due to its high seam treatment technology and ease of installation.
The flocking dryer fabric produced abroad mainly uses polyester woven dryer fabric (endless or seam type) as the base mesh, and then implants a certain fineness and quantity of high-temperature resistant short fibers on both the front and back of the base mesh. It is a high-performance composite product that combines the advantages of ordinary needle punching and polyester woven fabric.

How is Flocking Dryer Fabric Manufactured?

• Dryer Fabric Weaving Process

  Using a heavy-duty weaving machine produced by the German company Eugen, polyester monofilaments with both warp and weft threads of Φ 0.5mm are used. The dryer fabric structure is a double-layer four heddle structure, with a warp density of 22 threads/cm and a weft density of 11 threads/cm.

• Fiber Mixing Process
  This process requires the uniform mixing and thorough loosening of PA short fibers of different (or the same) varieties and thicknesses. This process involves uniformly mixing 40% 30D * 86mm polyester staple fibers and 60% 30D * 98mm nylon staple fibers, adding a certain amount of felt oil, and the ratio of felt oil to water: oil: anti-static agent=100:1:2. The moisture regain when the mixture is opened is generally controlled at 9-10%.
• Needling Process
  The rationality of the needling process will directly determine the tightness (density), surface smoothness and fineness, as well as the degree of damage to the fibers and dryer fabric of flocking dryer fabric. Therefore, it is necessary to closely monitor and strictly control the selection of needles, the condition of the needle plate’s perforation and needle placement, the depth and number of needle punctures, the speed of fabric feeding, the control of needle breakage rate, and the status of the batt carding.
  1) Selection of Needles
  Although the flocking needle is small, it is a crucial component that affects the quality of needle piercing. The thickness of the needle rod will affect the convenience and fixation performance of needle replacement, and directly affect the effect of the felt surface and the degree of needle breakage. The length of the needle working blade will affect the required needle penetration depth, which in turn affects the physical and mechanical properties of the product; Excessive length of the working blade can lead to excessive needle penetration, causing fiber damage, and also easily causing needle breakage and other problems. For thick and long working blades, they not only cause damage to the substrate and fibers, but also easily leave serious needle marks on the product; For short and thin needles, the needle has a lower ability to withstand pressure and has certain limitations on fiber entanglement. The shape, size, and quantity of the protrusions on the needle groove teeth directly affect the amount of hook and belt fibers and the degree of damage to the fibers and skeleton materials. Due to the thick and hard wire diameter of the dryer fabric, it is easy for the wire to be punctured and a large number of needles to break. Therefore, we chose the triangular single-sided toothed flocking needle produced by Groz Beckert Group in Germany, which solved the problem and achieved excellent results.
  2) Needling Frequency
  The needling frequency should be moderate. A frequency that is too low can affect production efficiency, but a frequency that is too high can generate significant mechanical vibrations, which not only cause unnecessary damage to the machinery, but also increase the traction force of the needling on the fibers and damage to the dryer fabric, leading to excessive needle breakage or fiber breakage. We chose a needle puncture frequency of 400n/min.
  3) Number of Needle Areas
  Because the base mesh of the flocking dryer fabric is polyester dryer fabric, the material is stiff, and it cannot be reversed online during the flocking process, especially in the production of double-sided flocking dryer fabric. Therefore, we use the most advanced three needle double-sided batt heavy-duty needle punching machine in China.
  4) Feeding Speed
  The feeding speed must be reasonable. If the feeding speed is too fast, it will cause the needle to deviate from the needle hole of the pallet due to the tension of the fiber web, resulting in needle breakage. At the same time, the damage to the dryer mesh and fibers will also be correspondingly enhanced. Therefore, we chose a transmission speed of 2-3m/min.
  5) Needling Density
  During the drying process of paper sheets, high requirements are placed on the breathability and strength of the flocking dryer fabric, which are closely related to the needle density. Therefore, it is necessary to use an appropriate needle density. Excessive needle density can lead to a large number of broken needles during the needle punching process, causing excessive needle marks on the surface, making the structure too hard, and even affecting the strength; The needle density is too low, resulting in excessively loose fiber layers and insufficient wear resistance in the produced flocking dryer fabric. The fibers are prone to loosening during use. Therefore, we chose a needle density of 4000s/m.
  6) Needling Depth
  The depth of needling is the key to better bonding between short fibers and dryer fabric.
• Carding Process
  The flocking dryer fabric produced this time is a double-sided, endless flocking dryer fabric. The side in contact with the paper is the front side, with a slightly thicker layer of batt, and the other side has relatively less batt, in order to increase the holding force of the front fibers and improve wear resistance. According to the different requirements for the air permeability used in different positions, the amount of batt also changes accordingly, generally ranging from 150 to 400gsm. The front of this plan has batt coverage of 240gsm and the back has batt of 120gsm.
• Heat Setting Process
  Heat setting is used to make the size (length elongation, width shrinkage, and thickness changes) of the flocking dryer fabric more stable, the fibers bond more firmly, the internal stress of the flocking dryer fabric is redistributed, the surface is smoother and denser, and Improve wear resistance. There are two shaping processes in this case, one is the shaping of the polyester dryer fabric after weaving, with the aim of interweaving and stabilizing the warp and weft elbow joints, making it smoother, redistributing the internal stress, and making the size more stable; Once is the final shaping of the flocking dryer fabric, which makes the bonding between the batt fibers tighter and the mesh surface smoother. This case adopts the most advanced hot oil drum shaping machine in China, which integrates pressurization, water washing, chemical treatment, and heat shaping.