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Cationic
Starch has a cationic charge attached to it, which improves the internal
strength properties of the paper. The elector-kinetic attraction promotes
a more intimate contact between the anionic cellulosic fiber surfaces and the
starch hydroxyls.
·
Cationic
starches represent a unique class of high performance starch derivatives which
have gained commercial acceptance because of their affinity towards negatively
charged substrate such as cellulose, aqueous suspensions of minerals and slimes
and biologically active macromolecules.
·
They
have already found extensive use in the paper manufacture in which they
function as internal binders and retention aids for various fillers and
emulsions and are added to the paper furnish before the sheet is formed.
·
They
are effective for improving such physical properties of paper as bursting and
tensile strength, elongation, fold endurance, and pick resistance.
·
Usually
0.5% to 1%addition of cooked cationic starch, gives the same improvement in the
paper as does 1.5% to 2% addition of corn starch.
·
Other
benefits of the cationic starches are improved drainage on the wire, better
sheet formation and enhancement of the sizing efficiency of an alum rosin size.
·
Cationic
starches also improve the retention of fillers such as titanium dioxide, clay,
calcium carbonate which are frequently incorporated in the furnish to improve
the opacity of high grade printing papers, fine writing papers, light weight
papers such as bread wraps, glassine etc.
·
With
increasing filler retention, the sheet loses strength because inert fillers
reduce the number of sites for fiber to fiber bonding.
·
Because
cationic starch acts both to improve strength properties and filler retention,
its use gives high strength properties at higher level of filler retention.
Advantages:
·
Increased
internal strength properties & retention of fillers & fines.
·
Faster
drainage & improved sheet formation.
·
Improved
effluent quality & reduced costs
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