Modern Approach for Precise Sizing Measurement, 2004 Paper Summit, Spring Technical & International Environmental Conference, (including Papermakers; Process Control, Electrical & Information; Product & Product Quality)
Paper converting processes, like coating and printing, involve direct contact of paper with water and other liquids.
Sizing measurement is critical due to penetration behavior differences of liquids, which lead to product variations
and quality loss. Predicting the performance of sized papers has always been somewhat difficult. Available
measurement standards do not precisely match the requirements and specifications of all sized paper markets. Sizing
additives are used in grades that were previously unable to use the technology, such as newsprint. These newer
sized grades require very quick and precise sizing measurement. Continuing the development of these grades
requires an objective precision measuring method be developed as well. In the future, low sized paper will become
increasingly important since the ink must dry quickly to meet printer requirements. This is especially true in the
multi-purpose office paper markets such as laser, inkjet and copy. Existing techniques like Cobb and HST have
weaknesses. HST and Cobb are used within a wide range of basis weight papers, but they are not suited for low
sized papers. These measurements are best suited for half and full sized papers. For light basis weight grades or
grades with low levels of sizing, the Cobb absorption test does not yield meaningful results due to the complete
saturation of these papers. The HST test cannot really measure fluid penetration for low size paper grades because
this measuring technique is too slow/long and does not model the actual effect that a papermaker wants to achieve.
For printed papers, the contact time with the aqueous solutions is very short. In this type of application, it is much
more interesting to look at water penetration after only a few milliseconds contact time and to understand the rate of
liquid penetration over this timeframe. The EST test allows this type of measurement and provides not only sizing
measurement but also surface roughness and wettability. This paper will compare the ultrasonic-attenuation method
to other techniques for sizing measurement and describe how each one relates to paper properties. It will
demonstrate how useful a quick and simple sizing measurement can be for papermakers, R&D, and the quality
control laboratory. Case studies will demonstrate sizing chemical dosage versus the actual degree of paper sizing.