Dear Reader of TissueMAG,
We are glad to be on TissueMAG pages, drawing your attention on some new improvements on yankee coating technology. As you perfectly know, yankee coating, together with stock preparation, is the very heart of tissue making process, and a proper set up of coating chemistry is mandatory to obtain desired bulk and surface properties of tissue, contribute to high production process performance and yield, provide optimal protection of the yankee cylinder surface and allow efficient converting operations.
All tissue makers have got used to have their own coating chemistry recipe, developed together with their supplying ‘partners’, term which, in no other case, is as adequate due to level of knowledge required to project a proper yankee coating chemical program. Experience, wide range of reliable coating chemicals and full control over the quality of the raw materials are required from supplying companies. A typical coating recipe is based on specific categories of chemicals, in particular protection aids, for the long term preservation of the yankee surface, release agents, controlling adhesion on the surface, and filming agents, providing the base coating film needed to have stable adhesion, film whose properties can be additionally controlled by the use of modifiers and, locally, applied on the out-of-hood section of the yankee, edge control chemicals.
The greatest challenge in tissue is to have a stable coating layer despite a huge number of interferences such as reduction of fresh water consumption, variable pulp acidity, a growing fraction of short fiber and waste paper in the paper recipe, shorter production campaigns, frequent changes between toilet and ws production and the request for bulkier and softer paper, leading to the use of creping blade with aggressive geometry and materials.
MARE provides the Tissue and Towel producers with all the chemical requirements to ensure optimum product quality
In this scenario, filming agents play a primary role, as they provide the first stabilisation of the paper sheet, when the wet web comes in contact with the yankee, and the first external barrier created between the blades and the yankee surface as well. The ideal filming agent shows high stability despite high production speed (1800 m/min or more) and uneven moisture profile, limits to the maximum blade wear, helps with maintaining stable paper quality until the end of blade life, combines with the protection aid to provide a flexible film with moderate adhesion behaviour, basic requirement to have low blade vibration and actively prevent chatter-marks formation, and, moreover, allows an easy shift between various tissue grades, for example between soft and bulky hankies and facials and kitchen towel, or between lightweight toilet paper and high basis weight kitchen towel, or between virgin pulp and deinked or waste paper.