High Yield Poly(ethylene-alt-maleic acid) Grafting to Wood Pulp while Minimizing Fiber/Fiber Wet Adhesion

Area of Science:

• Materials Science
• Polymer Chemistry
• Pulp and Paper Engineering

Background:

• Heating bleached kraft pulps with poly(ethylene-alt-maleic acid) (PEMAc) can graft carboxylated polymers to fibers, increasing yield.
• High wet strength in cured pulp often prevents effective repulping, limiting practical applications.

Purpose of the Study:

• To develop a modeling tool for optimizing laboratory pulp curing conditions.
• To translate laboratory curing conditions to industrial processes for carboxylated polymer grafting.

Main Methods:

• Impregnation of pulp with PEMAc solutions at pH 4, followed by catalyst-free curing at 120-180 °C.
• Development of a model based on the power-law dependence of wet tensile indices on the βΓ product (polymer conversion and application amount).

Main Results:

• Achieved fixation yields >85% while maintaining repulpability by optimizing curing time and temperature.
• Identified that the curing extent for high grafting yields is less than that for high wet strength.
• Demonstrated a power-law relationship (slopes of 0.6) between wet tensile index and βΓ, with pre-exponential terms varying by polymer and pulp type.

Conclusions:

• The developed model and established relationships can predict repulpability of larger-scale processes.
• Optimized curing conditions balance high polymer fixation with the ability to repulp treated kraft pulps.
• This research facilitates the practical application of carboxylated polymer grafting in the pulp and paper industry.