White top paperboard
AssigneeMeadWestvaco Corporation
InventorsBruce Babcock, Tricia Thomas
Life of this patent
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Abstract
A multi-layered paperboard having a high brightness and exceptional uniformity. The white topped paperboard has a base layer(s) made from wood pulp and a top fibrous layer made of unbleached wood fiber, filler and a binder to create a top fibrous layer of sufficient uniformity at moderate brightness levels. The top fibrous layer optionally contains a coagulant and/or a retention aid. In a preferred embodiment, the top fibrous layer of the multi-layered paperboard product is coated with a coating of additional fillers and binders to produce the desired level of brightness and uniformity. The invention also includes a process for making a multi-layered paperboard.
Claims20
A multi-layer paperboard product comprising a base layer of unbleached cellulose fibers and a top fibrous layer comprised of from about 20% to about 30% by weight of fibers, from about 60% to about 90% by weight of a filler, and from about 3% to about 10% by weight of a binder, wherein said paperboard sheet exhibits a GE brightness of at least 40%.
A multi-layered paperboard product comprising a base layer having at least 50% unbleached kraft pulp fibers selected from softwood fibers, hardwood fibers and mixtures thereof varying from about 20 lbs/1000 sq. feet to about 100 lbs/1000 sq. feet, and a top fibrous layer bonded to said base layer(s), said top fibrous layer varying from about 5 lbs/1000 sq. feet to about 17 lbs/1000 sq. feet comprising from 20 to 30% by weight of fiber, from about 60 to about 90% by weight of a filler selected from the group consisting of clay, calcium carbonate, talc, titanium dioxide, silica, zinc oxide, magnesium carbonate, magnesium hydroxide, and aluminum trihydrate, and from about 4 to about 6% by weight of a binder selected from the group consisting of acrylic latexes, styrene-butadiene rubber, polyisoprene latex and derivatives thereof, and cationic starches.
A method of making a multi-layer paperboard comprising, forming a kraft pulp stock, forming a second pulp stock comprising from about 20 to 30% by weight of fiber, from about 60 to 90% by weight of a clay, and from about 3 to 10% by weight of a latex, and bonding said second pulp stock to said kraft pulp stock.
Dependencies are inferred from the claim text.