Paperboards having improved bending stiffness and method for making same
AssigneeInternational Paper Company
InventorsDavid V. Reed, David A Dyer
Life of this patent
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Abstract
Paperboards having improved MD and CD bending stiffness by including a paperboard binder coalescing agent to cause starch paperboard binder to coat at least some of the paperboard fibers. Also a method for preparing these improved bending stiffness paperboards by combining with an untreated paperboard fiber stream a treated paperboard fiber stream where at least some/at least a portion of the paperboard fibers are coated with a starch paperboard binder due to the coalescing action of a paperboard binder coalescing agent.
Claims31
An article comprising a ply of paperboard comprising:
- paperboard fibers which comprise at least about 50% by weight hardwood fibers;
- a starch paperboard binder, and
- a paperboard binder coalescing agent in an amount sufficient to cause the starch paperboard binder to coat at least a portion of the paperboard fibers;
- the paperboard having:
- a caliper of from about 8 to about 28 points;
- a basis weight in the range of from about 105 to about 300 lbs/3000 ft2;
- a MD bending stiffness equal to or greater than a first curve defined by the equation:
- y1=0.5297x2.2095,
- wherein x is the caliper of the paperboard and y1 is the MD bending stiffness in Taber Stiffness Units;
- and
- a CD bending stiffness equal to or greater than a second curve defined by the equation:
- y2=0.2188x2.2681,
- wherein x is the caliper of the paperboard and y2 is the CD bending stiffness in Taber Stiffness Units.
A method for preparing a paperboard, which comprises the following steps:
- (a) providing a first stream of treated paperboard fiber stream comprising:
- untreated paperboard fibers comprising at least about 80% by weight untreated hardwood fibers;
- a starch paperboard binder in a weight ratio of starch paperboard binder to untreated paperboard fibers of from about 0.1:1 to about 2:1;
- and
- a paperboard binder coalescing agent in an amount sufficient to cause the paperboard binder to coat at least some of the untreated paperboard fibers to provide treated paperboard fibers;
- (b) combining the first treated paperboard fiber stream of step (a) with a second untreated paperboard fiber stream comprising at least about 50% by weight untreated hardwood fibers in a weight ratio of treated paperboard fibers to combined treated and untreated paperboard fibers in the range of from about 15 to about 50 lbs/ton to provide a paperboard web;
- and
- (c) forming the paperboard web of step (b) into paperboard having:
- a caliper of from about 8 to about 28 points;
- a basis weight in the range of from about 105 to about 300 lbs/3000 ft2;
- a MD bending stiffness equal to or greater than a first curve defined by the equation:
- y1=0.5297x2.2095,
- wherein x is the caliper of the paperboard and y1 is the MD bending stiffness in Taber Stiffness Units;
- and
- a CD bending stiffness equal to or greater than a second curve defined by the equation:
- y2=0.2188x2.2681,
- wherein x is the caliper of the paperboard and y2 is the CD bending stiffness in Taber Stiffness Units.
Dependencies are inferred from the claim text.