These
grades are used for magazine printing, higher quality
advertisement newsprint inserts, coupon printing and
other low lifetime, but high quality, high resolution
print products. These grades are printed by heat set
offset and rotogravure print processes. Mechanical
fiber is the majority of the fiber used in these grades.
They are used for their high opacity, low cost and
compressibility for rotogravure printing. Some of these
grades which are referred to as MWC (medium weight
coated) are double coated, but most of the volume of
papers produced in this segment is single coated. They
require coating pigments that will provide good coverage
of the surface. That is because the bas sheet can be rough
and because of their being just the single coating being
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This is especially true for the lowest basis weight
grades usually referred to as ULWC (ultra-light
weight coated) where very low coat weights are
used. Some carbonate can be used in LWC (light weight
coated) and MWC grades of paper but require pseudo-neutral
papermaking. In this case the coating will contain
a minority of carbonate and a majority of kaolin.
Good kaolin pigments to use are Astra-Plate, Suprawhite
80, Capim NP, Contour 1500 and for certain situations
Capim DG in the heavier weights. In ULWC grades
almost all machines are acid and the mineral pigment
is almost all kaolin with the same pigments being
recommended for use. The carbonate pigments used
are usually Carbital 90 and 95, but steeper psd
pigments like Carbopaque and Opti-Cal 400/600 are
being used.
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