Various specialty papers Flashcards
What are the most important properties for cigarette paper?
Porosity, measured in Cu units so different than our typical measurements. The smoke values are adjusted by the porosity.
Ash content is very important as it influences the combustibility. High levels of filler and special impregnations allow the smouldering effect rather than burning.
Should be very clean, treated like direct food contact, using only virgin fibres.
Opacity, formation and brightness. To keep uniformness and mean the tobacco is not shining through
What are criteria’s for the production of insulation papers?
Very high requirements for purity, uniformity, and insulation. The paper machines are run with deionised or even distilled water to produce the higher grades of paper. The paper should be pore free and not contain any fillers or conductive impurities such as metals, salts and acids.
What is cast coating and how does it differ from conventional coating techniques?
Special coating method which gives you the highest gloss and highest smoothness. The coating is applied to the paper using non-contact method and then dried using direct contact with a Chromium cylinder. You keep the thickness of the paper because you do not use calendaring. This means the stiffness of the paper is much higher (thicker paper = higher stiffness).
But costs almost double. Quite a small and declining market. For label, packaging and photopapers mainly
What is the structure of a general cast coating paper and which components do you find in each layer?
Thick base layer with little ash content and open structure. We then have the top coat which is made of pigments, satin white, binders, dyes, and OBA’s.
Draw a schematic of the Champion cast coating method and explain the process!
Wet coating pressed (low pressure) to chrome cylinder using a rubber roll, this then allows the surface to be similar to that of the cylinder.
Draw a schematic of the SD Warren cast coating method and explain the process
Air stream used to control the coating weight, this is then dried then sent through a gelatinisation bath to be re-wetted before being pressed against a chrome cylinder. Which then gives the high gloss finish.
What are typical properties of cast coated papers?
Very high surface gloss and smoothness. High bending stiffness due to high thickness (no calendaring). High strength in Z direction.
What are metallised papers and for what applications can they be used?
Paper which has been ‘coated’ with a very thin layer of aluminium, the aluminium is applied in a vacuum. Giving mirror like, metallic glossy surface to the paper. Used for gift wrapping, food packaging, labels, tobacco packaging.
Principle is that at low pressures the aluminium can be vaporised at lower temperatures, it then condenses at the cooling roll onto the paper surface.
