The effect of long fibers on sheet properties in foam forming

valuable products. For the current products the technologies enabling the reduction of the raw material consumption and improvement of the energy and water efficiency are under great interest. This is a challenging goal since the quality of the end product should simultaneously remain intact. In a water-laid process the challenge to improve formation comes bigger when the fiber length increases. To date the only solution has been to move towards more diluted conditions i.e. to decrease the forming consistency when utilizing long natural or man-made fibers. However, when using foam as a carrier fluid flocculation of fibers is decreased and fiber length can be increased. This paper will show some results on foam forming studies that have been performed with long fibers in realistic process conditions at VTT's pilot environment. Our scope is on long-fiber suspensions that can still be run on existing paper machine geometries. The average fiber length and foam density were the main variables in these trials. The formation of papers made of short fibers was always very good. For longer fibers the formation improved with decreasing foam density and was much better than that of water-laid samples.