Patented method removes undesirable resins from birch and other wood sources
The U.S. Patent and Trademark Office has issued patent No. 8,052,840 to Davit Sharoyan, senior staff scientist, Ashland Water Technologies.
What is it?
Titled "Pulping additives for a reduction of resin from Kraft pulp," the patent is a method for removing triterpene and triterpenoid resin from wood bark and chips processed in a Kraft pulping process. If not effectively removed, the resins may create problems later in the papermaking process or form deposits on papermaking equipment surfaces.
Birch resin is particularly difficult to remove because it contains betulin, a naturally occurring triterpenyl alcohol in its bark. Betulin has a significantly higher melting point than the other pitch components and doesn't fully dissolve during the Kraft process, creating problems in the papermaking equipment.
Manufacturers can completely remove the birch bark before the Kraft process, but that means less paper will be produced. Therefore, a stronger additive is needed to reduce the betulin found in birch bark.
In the Kraft cooking process, the wood chips are cooked in huge pressurized vessels called digesters. Some digesters operate in batch manner and some in continuous processes. A typical digester produces about 1,000 tons of pulp per day. The process takes several hours at 130 to 180 °C (266 to 356 °F) and the solid pulp is then collected and washed.
Sharoyan's patented method combines wood chips, Kraft pulping liquor (a strongly alkaline solution used to separate out the cellulose fiber), oils from plant sources, and at least one poly(alkylene glycol)-based surfactant or rosin soap/tall oil, and sends it through the Kraft cooking process. The process extracts the triterpenyl alcohol from the wood chips without having to reduce or completely eliminate the bark prior to processing.
By using Sharoyan's mixture, the undesirable resins are removed from the birch wood. That means increased pulp yield for our manufacturers. The patented composition can also be used for other wood sources, such as eucalyptus and tropical hardwoods.