Process Efficiency
A chemical measurement quantifies the percentage of suspended solids in paper machine stock that are retained on the forming wire. This value determines the efficiency of raw material use during the continuous production of paperboard. In paper mill operations, first-pass retention dictates how much starch, filler, and sizing agent remains in the sheet rather than escaping into the process water.
Filler Retention
Papermaking chemistry utilizes polymers and inorganic microparticles to control first-pass retention during high-speed sheet forming. These retention aids agglomerate fine clay and cellulose fibres, which allows them to be caught by the forming fabric. Low retention values mean that expensive additives are lost, which increases the cost of production and can lead to uneven distribution of materials throughout the board thickness.
Machine Stability
Monitoring this parameter helps paper mills reduce the buildup of fine material and chemicals in the process water loop. Excess fines in the white water can cause deposits on the paper machine, leading to paper breaks and holes in the sheet. Maintaining a stable retention rate ensures that the physical properties of the paperboard, such as stiffness and surface smoothness, remain uniform across different production runs.
This stability is also linked to reduced energy consumption, as a cleaner wet end requires less chemical cleaning and less steam to dry the sheet because of the more uniform water drainage on the wire.
