Development of a systematic quality control scheme for incoming raw materials and additives for the paper coating operation

The future development of printing papers will be determined by engineering and economic influences Ingoing control as the first stage of quality control is targeted to ensure adherence to requisite properties of a product within fixed tolerances. Within the framework of a special project, researchers have undertaken to identify the significance and optimum implementation of quality control for ingoing raw materials and additives intended for rise in the paper coating operation. The research project was aimed at improving the efficiency of production plants, enhancing quality and quality consistency and saving costs by developing a systematic ingoing control scheme for LWC manufacture in particular. The results obtained are transferable - perhaps in somewhat modified form - to the manufacture of other coated grades. In respect of qualify assurance specifications, the standards of the DIN EN ISO 9000 and others will be applicable. Detailed questionnaires were formulated and circulated to LWC mills in Germany and Europe in order to collect data on the actual state of ingoing control. Strikingly, the evaluation of the answers revealed a substantial lack of ingoing control in modern papermills. After the actual condition had been ascertained, a listing of selected measuring methods was prepared which lend themselves to systematic ingoing control in a mill environment. This listing primarily includes simple and meaningful test methods that may in part be applied before the raw materials and additives are unloaded. The methods were prioritized by relevance, test duration and costs. For coating pigment assessments, traditional well-proven methods are recommended, such as simple olefactory tests or a determination of screening residue, dry content, ash, viscosities, pH's, particle size distribution, abrasion and zeta potential In some areas it is advisable to determine the relative sediment volume (RSV). As far as synthetic binders are concerned, simple olefactory tests as well as a determination of active substances and dry contents, pH's viscosities, screening residue, dirt count and light transmission are considered suitable methods of assessment. All other additives may be tested along the lines of binder resting procedures.