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TECHNICAL:

The Effect of Center Plane Resistance on the Drainage and Sheet Forming

By John Xu, Roger Danby, Dale Johnson, John VanderKolk, Bruce Janda
AstenJohnson Inc

ABSTRACT

The 3D structures of three different types of triple layer fabrics are investigated based on -Ray micro-tomography and 3D modeling. It is found that the sheet support binder (SSB) fabric and the warp tied fabric have a very open structure between the top layer and the bottom layer of the fabric. In a warp integrated sheet support (WISS) fabric, however, all MD yarns pass from the top layer to the bottom layer and thus create a unique center layer between the paper side and machine side of the fabric.

Laboratory drainage testing indicates that, compared to SSB and warp tied fabrics, the WISS fabrics drains slower at low sheet basis weights (< 15 ~20 g/m2). However, the WISS fabric drains faster when sheet basis weight is higher than 20 g/m2. It is found that the resistance created from the center layer retards the initial impingement drainage which leads to a slower drainage of the WISS fabric at low sheet basis weight. On the other hand, because of the higher center plane resistance, fibers have less tendency to plug the drainage holes in a WISS fabric, which leads to a high drainage rate at higher sheet basis weights.

A Pilot papermaking trial confirms that, because of the center plane resistance, the WISS fabric will retard the initial high impingement drainage and shift the drainage downstream on the forming table. Field trial indicated that, because of the center plane resistance and reduced impingement drainage, sheets formed on the WISS fabrics have better formation and fines/filler retentation.

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