Paper Bleaching Chemicals : Paper Bleaching Auxiliaries

2017-01-08T00:14:16+00:00 Categories: Chemical Additives|Tags: , , , , , , , , , , |

Paper Bleaching Auxiliaries These products enable a more efficient bleaching of the chemical, mechanical and deinked pulps and lead to increased whiteness. They are generally based on sur¬face active agents, i. e. wetting agents (see Section 3.6.7.) which are resistant to bleaching chemicals as well as chelating (complexing) agents (see Section 3.6.3.). Some of the [...]

Paper Bleaching Chemicals : Bleaching Substances

2017-01-08T00:14:16+00:00 Categories: Chemical Additives|Tags: , , , , , , , , , |

Bleaching Substances . • Chlorination (C) with chlorine, an effective, selective and inexpensive bleaching agent that reacts very fast with lignin. For environmental reasons during the last ten years chlorine is being substituted by chlorine dioxide, ozone and/or oxygen all over the world. In Europe substitution is already 100 %. In this particular case bleached [...]

Paper Coating Machines : General

2012-03-14T12:23:08+00:00 Categories: Paper Coating Machines|Tags: , , , , , , , , , |

Paper Coating Machines Overview Coating machines are separate machines in which a previously produced dry base paper is unwound, coated, dried, and then reeled again (Fig. 7.24). In contrast to coating applicators placed on-line in a paper machine (Section 6.8), they are usu¬ally called “off-line coaters” or “OMC” (off-machine coaters).   In a paper mill, [...]

Paper Coating Machines : Blade And Rod Coating

2017-01-08T00:14:16+00:00 Categories: Paper Coating Machines|Tags: , , , , , , , , , |

Direct Coating In direct coating, the web is supported by a backing roll and the coating medium is fed in excess onto the web. After a certain distance, defining the “dwell time”, the coat layer is metered down to the final thickness, being the desired coat weight. In the “roll applicator” or “LDTA” (long dwell [...]

Paper Coating Machines : Film Press , Metering Rod

2012-03-14T12:22:03+00:00 Categories: Paper Coating Machines|Tags: , , , , , , , , , |

Indirect Coating As an alternative to direct coating, a film press can be used for the application of coating media. The film press was derived from the size press, which is used for the application of starch or size solutions. Today, a wide variety of coating media are applied, including pigment dispersions with high solids [...]

Paper Coating Machines : Curtain Coating

2012-03-14T12:21:52+00:00 Categories: Paper Coating Machines|Tags: , , , , , , , , , |

Curtain Coating Besides film and blade coating, curtain coating is used for the application of coat¬ing media onto paper surfaces. Although curtain coating is a very old application technique, going back to the end of the 19th century, it has only been used for coating of paper since the 1990s. Curtain coating is mainly used [...]

Paper Coating Machines : Application Concepts

2012-03-14T12:21:41+00:00 Categories: Paper Coating Machines|Tags: , , , , , , , , , |

Paper Coating Machine Application Concepts Typical coat weights for graphic papers are given in Fig. 7.28, plotted against the basis weight of the base paper. The coat weight is typically 25–40 % of the final basis weight of the paper. Wood-containing papers are mainly single-coated (LWC). Coat weights are usu¬ally between 6 and 10 g [...]

Paper Coating Machines : Coating Machine Driers

2017-01-08T00:14:20+00:00 Categories: Paper Coating Machines|Tags: , , , , , , , , , |

Coating Machine Driers After its application, the wet coat must be dried. Three different drying principles are used: radiation (infrared), convection (hot air), and contact (cylinders). Infrared drying yields a very good energy transport, whereas mass transfer is inferior. Therefore, infrared is especially suitable for heating the paper or board web to temperatures where considerable [...]

Objective of PM Control Systems

2017-01-08T00:14:22+00:00 Categories: Control Systems|Tags: , , , , , , , |

 Objective and General Terms of PM Control Systems 9.1.1 Objective A typical paper machine has a few thousands remote or automatically controlled functions like positioning systems, drives, valves and more than a thousand addi¬tional measurement devices to monitor the process and the condition of the ma¬chine. It is impossible for an operator to oversee all [...]

Paper Bleaching Chemicals

2012-08-07T11:02:39+00:00 Categories: Chemical Additives|Tags: , , , , , , , , , |

When chemical pulp, mechanical pulp and deinked recycled fibers are used in the production of white papers e. g. printing and writing papers, hygiene paper (tissue) or white top of board, these pulps have to be bleached up to a certain brightness. The bleaching of chemical pulp (see Volume 1) is carried out in several [...]