Foam forming-the effects of surfactant type on characteristics of fiber-foam suspension and properties of formed fiber network

The properties and behavior of pure aqueous foams have been quite extensively studied. On the other hand, very little is known about the chemical interactions between foaming agents and paper/board making raw materials in aqueous fiber-foam suspensions. The objective of this examination was to increase the understanding of basic mechanisms affecting fiber-foam suspension. In particular, gaining understanding of the chemical interactions between foaming agents and paper/board making raw materials was of great interest. The foaming behavior of pulp formulations in the presence of three anionic and four non-ionic foaming aids was tested with a tailor-made foaming test environment. Foaming aids for testing were chosen based on their reported good foaming properties, environmental safety, and availability as bulk chemicals, as well as their insensitivity to changes in temperature and pH within limits relevant to the foam forming process. Foam formed hand sheets with different furnish recipes were made and tested to evaluate the effect of the three selected foaming agents (selected based on their foaming characteristics) on the formation and retention processes, the technical properties of the hand sheets, and the performance of other chemicals used in paper/board manufacturing in the presence of the foaming aids. Additionally, the potential of utilizing the selected foaming aids in practical foam forming of paper or board was verified in a small-scale pilot trial. The results obtained in these laboratory and pilot-scale studies showed that the type and amount of foaming aids used have significant effects on foam properties, filler retention, sizing, dewatering, bulk, and mechanical properties of the fiber network. In fact, the selection of the foaming aid and its interaction with other wet end additives seems to be one of the key factors affecting the processability and quality of foam formed products.