Paper and Chemistry

Pulp and Paper Chemistry

Is an integrated chemical process

"Paper chemistry is an amazing process," says John Heitman, a professor of chemistry at North Carolina State University. "People use paper all the time, but they don't think about where it comes from and what it's made of." Likewise for students of chemistry, the pulp and paper industry is relatively unknown. So, departments of pulp and paper technology actively recruit high school students to their programs-many of which are industry supported and provide attractive scholarships.

Pulp chemistry and paper chemistry are integrated processes, but each is carried out somewhat separately. Chemists in the paper-making business tend to gain experience with both pulp and paper science, because knowledge of both is integral to the smooth running of a paper mill.

Pulping is a process of delignification-removing lignin from wood while leaving cellulose fibers intact. Most pulping is done through a "Kraft" delignification process, which uses sodium hydroxide and sodium sulfide to chemically remove lignin. After delignification, the color of the pulp is dark brown. If white paper is desired, the pulp is bleached. Delignified, bleached pulp is fed into paper machines after undergoing other chemical processes that produce the desired quality and characteristics for the paper. "Sizing" chemistry gives the paper resistance to moisture; "retention" chemistry binds fillers and shorter fibers into the paper; and "wet strength" chemistry ensures that products like paper towels will not disintegrate in water.

Is a changing industry

"Paper-making is changing rapidly," comments Martin Hubbe, senior research scientist at International Paper. "Concern about environmental impact is changing some of the chemical processes and the chemistry used in paper-making. A lot of the new emphases are on recycling and de-inking technologies." In addition, chemists are turning to chlorine dioxide and hydrogen peroxide as...