Felt, paper machine

Polyolefin—ceUulose composites also are used in nonasbestos flooring felts, waUpapers, filter media, labels, embossable papers, and other nonwoven fabrics that are made on paper machines. Use of synthetic fibers in paper has been reviewed (103,104). 

Water Clarification. Process water that aeeds to be clarified comes from several differeat sources ia the recycling mill rejects from screeas and mechanical cleaners rejects from washers, thickeners, and flotation cells water that drains from the pulp as it is converted iato paper oa the paper machine (white water) and water from felt washers. These waters contain different dissolved chemicals and suspended soflds and are usually processed separately. 

Fiber from PPS resins has been made in two forms. Monofilament is used in paper machine drier felts to replace polyester, which is attacked by the hot, corrosive conditions of papermaking. Staple fibers are made into filter bags for flue treatment, and are considered a growth area. 

As the machine speed has continuously has increased the dynamic forces to the web have increased and it has forced to support the web with felts to avoid web breaks. Before 30 s typically the web had open draw between press and wire section which was soon replaced with pick-up suction roll arrangement. In this arrangement web is picked up with a suction roll from wire and supported by press felt to the first nip. Most recent fast paper machines are using the same principle of suction roll and supporting fabric not only through press but also through dryer section. 

Paper machine Machine on which paper or paperboard is manufactured. The most common type is the fourdrinier machine using the fourdrinier wire as a felting medium for the fibers. 

Use Continuous conditioning and batch washing of paper machine felts. Paper-mill system boil-outs. Deinking of secondary fiber. 

Paper machine components other than suction rolls can experience corrosion fatigue cracking. Dorsch et al. [43] used a fuU size felt roll journal as a laboratory fatigue test specimen in simulated white waters containing thiosulfate ions. 

Even though oxidants can be very effective and are relatively inexpensive biocides, they can also cause problems for the papermaker. Oxidants can corrode the metals used in the paper machine and destroy felts used in the press section. Oxidants can also react with and destroy other chemicals used in papermaking including... 

These substances affect paper machine runnability and paper quality. They can be found on paper machine wires, felts, vacuum boxes, dryer cans, calender rolls and in the finished paper. The consequences vary from early replacement of wire and felts, to web breaks, dirt and even holes in the finished paper. In order to understand the mechanism of fixation for particles within this size range, one has to... 

A paper machine comprises a framework at the tending side and one at the drive side of the paper machine supporting different kinds of rolls and stationary elements like dewatering elements or beams for sensors. Almost throughout the whole paper machine the paper web is in contact with forming wires, press felts... 

All press nips in modern paper machines are single or double felted. Shoe presses are mainly double felted. The pick-up felt is in the first press felt position it has to transfer the wet paper web from the forming wire to the press section. Whilst the loads of the press nips increase from press position to press position of the press section, the diameter of the felt fibers on the paper side surface decreases. Changing from a coarser press felt surface to a finer one enables the transfer of the paper web, due to the increased adhesion by capillary forces and larger contact area. 

Seamed felts, in contrast, are used mainly in the production of board and packaging and are not endless. They are closed in the paper machine with a seam, produced in a special variation of the weaving process. They are very common in North America (about 60% of all press felts in NA are seamed felts) and are easier... 

Shoe presses have been standard in press sections for board and packaging grades since the 1980s. Later, they have also become state-of-the-art presses for graphic paper machines. Today modern press sections of high-speed paper machines consist of only two nips. They have for instance two double-felted nips or one double-felted nip followed by a second nip with a felt and a transfer belt... 

A reliable web guidance system is important to prevent web breaks, especially at high machine speeds, low basis weights, and at low dry contents of the web, as found after the first press nip. In modern paper machines, especially in the press section, the web is not conveyed freely, but is nearly always supported by a felt, belt or wire, or by the surface of a roll (closed draw). 

Figure 6.81 shows a schematic of a modem paper machine for LWC paper production started up in 2004. It includes a gap former wire section, a press section with a double-felted first press nip and a second press nip with felt and transfer... 

From the press section, the paper goes to the dryer sections. Steam heated or infrared dryers are the most expensive dewatering methods on the paper machine. The dryers willl reduce water in the sheet from 60% to 5-8%. Steam dryers are a series of cylinders over which the paper web passes, while being held to the siuface by felts. Drying also occurs between the cylinders by heated air blown into the gaps. This is known as pocket ventilation. 

Another consideration relative to measures of plasma surface modification with paper-based materials is surface roughness. Surface roughness with papers is inherently influenced within the manufacturing process and will vary dramatically with the side processed. The sides are known as wire side and felt (top) side . The side in contact with the paper machine wire during manufacturing is called the wire side. The opposite side is top side. Prior to the deposition of thin layers of fibers on machine wire, fillers are drained away. As such, the wire side will have less fillers compared to the top side. Process controls predetermine a designated level of surface roughness on each side of papers prior to surface modification by plasma treatment, as well as texture and absorbency. 

---