PAPER CHEMISTRY LABORATORY, INC.
.....the acknowledged leader in papermaking chemistry Instrumentation

 

 

Procedure

Wet End Chemistry:
Using the MARK III or MARK IV a sample of furnish is poured into the jar and mixed at a pre selected speed.

The drain valve is opened. After 30 seconds, the valve is closed. This resultant volume of fluid or "white water" represents the Dynamic Drainage parameter, which is measured using a graduated cylinder. The Dynamic Drainage liquid may then be used to measure first pass retention and the electrokinetic parameters, zeta potential, conductance, temperature and pH.

The MARK III or MARK IV may also be used to determine Water Removal Efficiency, without additional dedicated hardware. Dewatering, or ease of water removal, is a key parameter and should be measured along with drainage, retention, electrokinetic and physical properties when one is altering or optimizing the wet end chemistry. We have developed a test method for measuring water removal without additional dedicated hardware. Good correlation is obtained between our method and the centrifuge method as described in TAPPI Journal vol 63 no.9, September, 1980. The standard deviation of our test method varies from 1 to 5% depending on the variability and complexity of the papermaking furnish. The efficiency of data collection makes the MARK IV method highly suitable for mill trial work.

Hand sheet Preparation:
Using the MARK IV (large valve base) or MARK V, the sample of furnish is mixed at a preselected speed. The drain valve is opened, causing rapid evacuation of water. A laboratory vacuum pump and collection flask is attached to the jar via the valve for further water removal.

Felt Plugging/Felt Conditioning

Maximizing coagulation chemistry on the wet end can have the unfortunate result of maximizing press section problems. The reason for this is that the fiber used in felt making behaves electrokinetically much like cellulose. Therefore, the cationic (and anionic) chemicals that act to coagulate/flocculate the cellulose fibers and fines (and fillers; pitch, etc.) have a very similar effect on the felts in the press section. This results in filling, loss of porosity, and other operating difficulties which can have the effect of decreasing useful felt life and seriously impairing efficiency. A test method is provided in which the wire mesh screen is replaced with a piece of new machine felt. A felt and plastic wire cutter is optionally available to cut out experimental discs. This test may be used to predict felt filling or for the screening of felt conditioning agents.

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