International Paper Company

Wadood Hamad

Xiang Yu

Henry J Kent

Robert A Hulbert

Bruce Lyne

Thomas D Sandry

Bruce Lynn

An engineered crack-resistant paper or board for improved runability formed by depositing a thin discontinuous thermoplastic or thermosetting polymer onto a cellulose fiber network web and having same absorbed into the network in specific geometrical formations. The base sheet thus formed may then be used for various end uses such as packaging, containers, plates, cups, low-weight coated printing grade boards or the like.

Engineered crack-resistant paper and board

A method of engineering score-line-crack-resistant multi-ply linerboard. The propensity for score-line cracking may be eliminated by engineering a ductile, plastically deforming top ply of a two-ply construction. Plasticity essentially extends the life span through which a material may deform (under external monotonic loading) prior to the initiation of damage (e.g., crack propagation) and ultimate failure. Hence the board's propensity for cracking is intrinsically linked to its fracture energy, or the energy consumed during plastic deformation (prior to failure). A top-ply fracture tester is used to measure the plastic energy consumed in deforming a single ply in a multi-ply system. The energy consumed in the plastic zone has shown excellent correlation to score-line cracking field performance of white-top linerboard. Machine trials were conducted to identify the principal variables that affect the propensity for score-line cracking. The principal variables identified were: fiber furnish (virgin vs. recycled), top-ply coverage (i.e., weight % of the top ply), refining energy of the top-ply furnish, and the starch and filler contents. Pulp quality, especially pulp viscosity, was also shown to play an important role in influencing cracking resistance. The engineering method provides recommendations for key operational parameters to produce score-line-crack-resistant white-top liner-board.

Methods for engineering and manufacturing score-line-crack-resistant linerboard

A mathematical model is used to design paper and paperboard having improved runnability. The mathematical model provides an estimate of fracture toughness for an optimized paper product based on specific measurement parameters, e.g., filler percent, softwood content and caliper for optimal fracture toughness. After the optimizing set of measurement parameters has been acquired, these parameters can be used to manufacture grades of paper having improved runnability performance, e.g., in printing presses.

Method for manufacturing paper and paperboard using fracture toughness measurement

A method and an apparatus for predicting a score-line cracking propensity of a multi-ply substrate. The method includes the steps of: bending the multi-ply substrate; acquiring tensile load data from the multi-ply substrate during bending; and computing a material property of a top ply of the multi-ply substrate based on the acquired tensile load data. The material property must show a strong correlation to the score-line cracking propensity of the multi-ply substrate. The material property which is computed is the energy consumed in plastic deformation of the top ply during the fracture process. The measurement results can be used to predict score-line cracking propensity in multi-ply board systems, such as multi-ply paperboard.

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Mahwah, NJ, United States of America

Wadood Hamad