Development of a Tissue Creping Test Rig
One of the key technologies in the production of tissue is the creping process, where the wet paper is adhered to a large drying cylinder and then peeled off the cylinder, when dried, with a doctor blade. The doctoring process changes the structure of the tissue, breaking bonds between the fibres, greatly increasing the thickness while reducing the length of the sheet and creating the soft feel of the tissue.
This paper will describe a laboratory scale rig that we have built to investigate the creping process. The creping rig is fed by a continuous web from an unwind stand. The web is processed by spraying the desired level of adhesive type, concentration and volume onto an internally heated cylinder, adhering the web to the heated rotating cylinder using a presser roll, and then doctoring the web from the cylinder and rewinding.
Controllable parameters include spray rate, adhesive concentration and type, cylinder temperature, rewind tension and dryer speed. Creping effectiveness is measured on-line from the reduction in web length and from the force required to doctor the sample off the cylinder. Effectiveness is also measured off-line from the change in thickness, strength and stretch of the samples. This paper will discuss some of the design details of the rig and the challenges that have been overcome to obtain stable and reproducible running on the rig. A typical set of trial results will also be discussed and compared with those obtained from commercially produced tissue.