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Patent reduces environmental concerns in alkyl ketene dimer preparation
| The U.S. Patent and Trademark Office has issued patent No. 7,960,497 to David Gerstenhaber, senior staff scientist, Ashland Water Technologies. |
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What is it?
Titled "Preparation of alkyl ketene dimers," the patent describes a solventless process for the preparation of alkyl ketene dimers (AKD). This process combines at least one polyamine with a fatty acid chloride to form a mixture of amine salt and dimer. This slurry is separated into two layers, an organic dimer layer and a water-based salt layer.
AKDs are waxy, water-insoluble substances used as sizing agents for the pulp and paper industry. Sizing reduces the dry paper's tendency to adsorb liquid, making it an important quality for the end product. Our Franklin, Va., dimer facility is the largest in the world.
Applications
By adding AKD to the wet end of the paper machine, customers can control the penetration of water and other liquids into the final sheet. This makes paper suitable for writing or printing. AKD is especially favored for products that need to resist water over a long period of time, like paper-based milk cartons and paper currency.
Ashland's imPress™ CL surface sizing agents radically improve the print performance of paper used in inkjet printers, especially inkjet printers utilizing pigment-based inks. Paper treated with an imPress CL surface sizing agent enables the end user to produce prints with exceptional image quality and definition using a variety of printing devices.
AKDs are often prepared by adding fatty acid chlorides to a heated mixture that includes an inert solvent. The inert solvent ensures good mixing and product separation. Without the solvent, a salt byproduct forms, making the reactants difficult to mix. However, the presence of residual solvents in the final product causes some environmental concerns. Residual solvents can also escape in the exhaust during the drying process. A previously unaddressed need exists to prepare AKD without the addition or solvents.
Benefits
The patented process prepares AKD with an end product containing significantly low levels of residual solvents. The method relies upon the ability of an amine (organic compound) to act as a solvent. No additional solvent is needed to produce AKD, making it an essentially solventless method. In addition to the environmental advantage of this method, the process results in high dimer levels that are attainable in the reaction mixture, making it a higher-performing AKD.
