paper machine felt
The third generation of papermaking felts
Through the efforts of experts, the third generation of papermaking felts has been used for many years. This kind of felt are high-thread bottom-net needle-punched felts, also known as BOM papermaking felt. BOM papermaking blankets are currently the most widely used papermaking felt, and their use penetration rate has reached more than 95%. The high-thread bottom net needle punched papermaking felt is composed of two parts: the bottom net layer and the fiber layer. Its structural feature is that the bottom net layer is made of different weaving technologies in the vertical and horizontal directions. It is divided into single layer and double layer. , Multi-layer or multi-layer stacking, using multifilament chemical fiber material in the longitudinal direction, using monofilament or multifilament composite chemical fiber material in the transverse direction, and then piercing wool nets on both sides of the bottom net to make a blanket. The bottom net and the wool net are both 100% synthetic fiber, therefore, the high-thread bottom-net needle-punched papermaking blankets can be divided into single-layer, double-layer, multi-layer, laminated bottom-net needle-punched papermaking felt and no-node bottom-net needle-punched papermaking felt.
2. According to the different parts of the felt used
1, forming felt
As the name suggests, this type of blanket is mainly used in the forming part of a paper machine. Forming felts are mainly used in the forming section (wire section) of single-rotary screens, multi-rotary screens, and superforming paper machines, but it is customary that people can also classify it as a press felt. The forming part of this type of paper machine has higher requirements on the performance of paper removal (tape) of the felt, water filtration performance, breaking strength, and dimensional stability.
2, press cloth felt
This type of felt is mainly used in the press part of the paper machine, and plays a key role in the entire wet paper sheet press and dewatering process. According to the structure of the press device and the dehydration conditions, the press felts can be divided into: ordinary press felts, composite press felts, supporting press felts, vacuum return blankets, light press felts, groove press felts, vacuum press felts, and large rolls. Press blankets, shoe press blankets, and hot press blankets; according to the upper and lower parts of the blankets, they can be divided into: press upper blankets, press lower felts; according to the order in which the blankets are used in the press section, they can be further divided into: one press blanket, two press Blankets, anti-pressure blankets, etc.
People usually refer to forming blankets and press blankets collectively as wet blankets.
3, dry felt
In order to distinguish the forming felts and press felts mentioned above, we call the felts used in the dryer section of the paper machine as dry felts. During the drying process, the paper sheet is pressed tightly on the surface of the drying cylinder by the dry felt, which speeds up the drying, improves the drying speed and efficiency, and also makes the paper sheet flat and smooth.
According to different types of dryers, felts can be divided into group cylinder felts and MG felts (gloss cylinder felts with rollers).
According to the raw materials used in the manufacture of carpets and the structural status, it can be divided into canvas carpets, woven carpets, needle-punched carpets and flocked carpets (nets), etc.
(1) The canvas dry blanket is woven with cotton fiber yarn. Later, some synthetic fiber filaments and cotton yarn were added to increase the strength and wear resistance, and prolong the service life. The weaving method is generally double plain weave, triple plain weave, warp double weft three layers, warp three weft double layers, etc. The basis weight is 2 000～4 000g. m-2, the main processes are spinning, plying, weaving, leveling, clamping (seam), etc. Mainly suitable for small and medium paper machines and paper machines that produce high basis weight paper.
(2) The woven dry felt is made of high-quality wool through spinning, weaving, inlaying, washing and shrinking, drying and shaping, etc. The texture is 2/2 twill, and the basis weight is 2 000-4 000 g﹒ m-2. It is suitable for the production of tissue paper and high-grade tissue paper by Fourdrinier paper machine.
(3) Needle-punched dry felt is a second-generation high-chemical fiber and full-chemical fiber needle-punched product. It is characterized by better air permeability and high temperature resistance than woven dry felts, and it can be directly made into a ring shape. Needle-punched felts can be divided into BOB blankets and BOM blankets; BOB blankets mainly include latitude and non-latitude BOB blankets; BOM felts mainly include single-layer, double-layer, and three-layer BOM blankets. The production process is basically the same as that of BOB wet felt and BOM wet felt, and the basis weight is 1200～2000 g. m-2, suitable for products with higher paper requirements, such as cultural paper such as double offset paper and special paper.
(4) Flocking dry felt (also known as flocking dry net, composite dry blanket) Flocking dry felt is a new type of papermaking drying equipment, and it is also a typical netting combined product. It is produced by needle-punched flocking on one or both sides of the dry web that is in contact with the paper web. It can also be layered with thick and thin fibers, and then produced through processes such as heat setting, trimming, and edge sealing. Mainly divided into flocking monofilament dry felt, flocking multifilament dry felt, flocking spiral dry felt and other products. It not only has the fineness of the needle-punched dry felt surface, but also has good air permeability of the dryer fabric. It is suitable for wide, medium and high-speed paper machines to produce medium and high-end products.
At present, canvas and woven carpets have been basically eliminated. Needle-punched carpets, BOM carpets and flocked carpets are mainly used, and some parts have been replaced by dry nets.
