Materials & Chemicals : Paper


Efficient Method for Pretreating Lignocellulosic Materials to Produce Paper with Improved Properties

UW-Madison researchers now have improved their previous technology by using derivatives of oxalic acid, preferably diethyloxalate (liquid) and dimethyloxalate (solid). These derivatives work better than oxalic acid in the pulping process.  They can be added to the wood chips as dry components and then treated with steam.

Paper Pulp Pre-Processor

A researcher at the University of Wisconsin – Stevens Point has developed a mathematical technique for producing a final pulp of consistent fiber-length distribution from two or more original pulps of varying fiber-length.

A pulp fiber length distribution is a mathematical representation of the total number of fibers with specified lengths. This is important in papermaking because long fibers have a greater tendency to tangle into undesirable tufts—flocs—than short fibers. Normally, fiber length distributions are ignored because newly produced pulp sources are derived from a constant wood source and a single pulping process—factors that make create a uniform pulp length. However, paper production is becoming more reliant on the incorporation of waste paper that has an uncontrolled fiber length distribution because it has been recycled from many sources.

The technique described in this invention allows a source of short fiber (hardwood), a source of long fiber (softwood) and a source of variable length, recycled pulp to mix together in such a way that the fiber length distribution of the mixture flowing onto the paper machine remains constant. Each source stream flows into a single mixing hold. The analyzer controls the valve positions for each stream. When the recycled pulp’s fiber distribution becomes shorter in length, the analyzer compensates by balancing with an increase in longer pulp fibers. In this way, the fiber lengths of the recycled pulp are continuously analyzed, and the amount of hardwood and softwood pulps added to the mixture is adjusted to prevents flocs and maintain a constant, even distribution.

Method for Producing Pulp

UW-Madison researchers have developed a method for producing pulp from wood chips by pretreating the chips with oxalic acid and sodium bisulfite. Prior to pulping, wood chips are cooked in a solution of oxalic acid and sodium bisulfite for a short period of time. This processing step requires little time and improves both the economics of the pulping process and the properties of the finished paper product, which exhibits greater strength and no loss in brightness.