With the increasing speed and width of paper machines, there are two serious problems in the dryer section: the first is uneven moisture distribution, and the second is the instability of the paper web, which is commonly referred to as paper jitter. . Solving or alleviating these two problems is inseparable from the use of suitable drying fabrics.
In order to run on a paper machine, the Paper Machine Fabric must meet certain requirements in terms of strength and dimensional stability:
1) Avoid degradation in high temperature and high humidity environment
2) It must be anti-wear, anti-disturbance, and cleanable.
Only with such conditions can the dry blanket run at a specific air permeability.
At the same time, the Drying Fabric also has the following functions: supporting and guiding the paper, assisting in drying, preventing wrinkles and controlling shrinkage.
Material and structure
When selecting the drying material, the main consideration is the degradation of the fabric under the action of moisture and heat. Through experimental comparison, synthetic fibers are better than cotton and wool fibers.
Commonly used synthetic fibers are polyester, polypropylene, polyamide and acrylonitrile. Polyester has the best performance for new drying fabrics. Polypropylene, polyamide and acrylonitrile have good hydrolysis resistance. The air permeability selection of the dry blanket depends on the speed of the paper machine and the basis weight of the paper. The dry blanket with low air permeability is commonly used in the first and second sections of the dryer. As the strength of the paper increases, the air permeability of the dry blanket Gradually increase.
Polyester Forming Wire Fabric
Polyester Forming Wire Fabric
Traditional dry blanket
Such dry blankets include cotton blankets and cotton-synthetic fiber blended blankets, which are woven into two or three layers with worsted yarn (multifilament yarn is commonly used as a reinforcing backbone).
Needle-punched dry blanket fabric
In this type of structure, 100% synthetic fiber multifilament or monofilament yarn is used in the longitudinal direction and monofilament yarn is used in the transverse direction. A section of the base fabric is plain weave or double-layer woven. The synthetic fiber fleece is needled into both sides of the base fabric to increase its stability, strength and surface smoothness, while protecting it from physical and degradation effects. Because 100% synthetic fiber yarns are commonly used in needle-punched dry carpet fabrics, they are all heat-set before being put on the machine.
Net-like drying fabric
Its design structure is smoother and more open than needle-punched fabrics, and it is manufactured to control air permeability. It is woven by multifilament or worsted yarn longitudinally, and woven by worsted yarn or glass fiber transversely.
Worsted acrylonitrile yarns with varying fiber composition in the longitudinal direction are as low as 100% synthetic fiber content, and glass fiber blended yarns are commonly used in the transverse direction to maintain its stability. Two-layer or three-layer weaving is often used.
Monofilament drying fabric
Like the net-like drying fabric, it is manufactured to control air permeability. Monofilament is used for longitudinal yarn, and monofilament and multifilament blended yarn is used for transverse yarn to control air permeability. Synthetic fiber monofilament and multifilament are woven in one, two or three layers. The yarn is made of Polyester Forming Wire Fabric and polyamide. Polyester and polyamide blended yarns can obtain a longer life under humid and hot conditions. The monofilament drying fabric has been overheated and shaped before being put on the machine.