Properties of adhesive apllied to panels from the substitution for lignosulfonate of the sulfite process

Abstract

Considering the agglomerated panel industries, most of them use synthetic adhesives, especially urea-formaldehyde, and to this end, studies covering the characteristics of alternative materials for the panel industry become important, especially when considering the final cost of the products generated. The present work had as general objective to evaluate the alterations in the chemical structure of the adhesive that could cause possible modifications in its binder properties as a function of the substitution of the adhesive urea-formaldehyde by the lignosulfonate. Therefore, it was determined the basic chemical composition of the lignosulfonate and its chemical bonds by infrared spectroscopy (IR) and the nuclear magnetic resonance (NMR), pure and in composition with different catalysts; the properties of urea-formaldehyde and its modifications such as pH, viscosity, gel time and viscosity. NMR analysis showed the lignosulfonate to the same pattern usually obtained for lignin derivatives in their chemical bonds. The elementary chemical analysis showed high Mg, Ca and Na. The addition of lignosulfonate on urea-formaldehyde caused the adhesive acidification and reduction of viscosity values. The effect on gel time was also affected. However, it was found that the methodology for this type of polymer should be adequate compared to the traditional method, submitting the same to temperatures above 90°C. The results showed that it is possible to use lignosulfonate to replace the urea-formaldehyde adhesive.

Keywords:
Sulfite liquor; Natural adhesive; Synthetic adhesive