Concerns of Forming Wet Lay Nonwovens From Long Fibers, 1995 Nonwovens Conference Proceedings

Irwin M. Hutten

Institute of Paper Science and Technology

This discussion is concerned with the production of wet laid webs produced from long fibers (aspect ratio > 300: 1). A model is presented to show that dilution water requirements increase with the square of the aspect ratio. Other pertinent fiber properties are modulus, surface energies, shape, and quality. A variety of dispersion systems include wetting agents, viscosity modifiers, air-water emulsions, and associative thickeners. Other stock system chemicals include wet and dry strength additives, defoamers, biocides, pH control, and retention aids. Mechanical stock system concerns are agitation, vessel sizing, pump sizing, and pipeline restrictions. Inclined wire and rotary, two types of formers traditionally used in the production of wet laid nonwovens, are described. Twin wire and suction breast roll formers are potential high-speed formers (> 1200 fpm) that may be used for forming long fiber webs. Downstream concerns include wet pressing and drying. Drum drying and hot air drying are the two most common processes. Yankee drying is mentioned as a possibility. Binders are often added to wet laid nonwovens. This is done by beater addition, wet end saturation, and/or dry end saturation. The advantages and disadvantages of each are discussed. The possibilities of thermal bonding and thermal bonding fibers are mentioned.