Uncoated Mechanical market
Uncoated Mechanical (groundwood) papers are light weight grades based on mechanical or recycled fibre . Typical substances range from 45-60 gsm and the papers are used to print phone books, newspaper inserts, low quality magazines, catalogues and a host of other applications where the life of the print is short, but the quality of the image must be good. These papers are printed by rotogravure, offset and flexographic printing (which is replacing letterpress). The paper must be smooth, low cost and print well.
The majority of pigment used here is in the supercalanedered or SC sub-segment. Filler levels in these applications can be as high as 30-35% and filler choice is generally based on coarse kaolins which give the required gloss, porosity and printability . Kaolin pigments like Intramax 40, Intramax 60, Capim SBF, Capim CC, and WP are typically used depending on geography, machine runnability and brightness requirements.
More recently in an attempt to lower cost and achieve higher brightness levels pseudo-neutral papermaking and carbonate pigments have been introduced along side kaolin. However, carbonate use is often restricted to relatively low levels within the filler system because of its adverse effect on porosity and printability especially in SC rotogravure applications. Typically carbonate use is between 20 and 50% depending on the brightness requirement in SC. Typical filler carbonates are based on engineered GCCs such as Intracarb or PCCs like Imerys’ Opti-Cal filler range.
