Alkaliarme reaktive Phenolharze für Span- und Faserplatten

A method has been developed to substitute 87.5 mol% sodium hydroxide with ammonia during the synthesis of a phenol-formaldehyde-resin (PF-resin). With 50% solid resin this glue contains only 1.07% sodium hydroxide. The bending strength of particle boards bonded with this low alkali PF-resin was much higher than the minimum requirement for V100 boards and comparable to results reached using a commercial PF-resin. For an application in the middle layer of particle boards the reactivity of the new glue was too low. However, a mixture of 2 parts of the new glue and one part of a commercial PF-glue, related to solid resin content, was suitable for the middle layer. With only 0.40% soduim hydroxide, particle boards made with this mixture in the middle layer and the pure low alkali glue in the surface layer fulfilled the requirements for V 100 boards.