This report summarizes the work and findings of a national research project designed to investigate both the process parameters that affect resin application efficiency and the possibilities for optimizing MDF resin injection systems.
The scope of this research includes: developing and evaluating methods to quantify resin distribution, degree of resin pre-cure, and resin loss; conducting a series of experimental works using selected test methods to quantify the resin distribution of blowline-blended fibre, resin loss, resin pre-cure, and their correlations to MDF panel properties.
Based on experiment results, the following conclusions can be reached:
Blowline resin injection is still the most effective and economical method for resin blending in MDF production.
Blowline resin blending efficiency is affected by fibre characteristics, resin distribution, resin pre-cure, and resin loss during the MDF process.
Resin distribution is affected by steam/fibre flow dynamics and consistency, and resin spray characteristics.
The best resin distribution can be achieved with steady steam/fibre flow at an adequate velocity (approx. 80 m/s at the injection point with steam pressure of 4.5 bar) and high turbulence in the blowline, low resin viscosity, and a good injection nozzle system.
Both the XRF test method developed by Forintek and the nitrogen content test using the Kjeldahl method are effective methods for determining resin content and resin distribution on the MDF fibre.
For the typical MDF mill studied, resin loss during the MDF process is about 6.5%.
Overall resin pre-cure in a typical MDF process is about 20%. Results from the laboratory experiment confirm that at 40ºC, the rate and magnitude of resin curing reaction can be significant.
The test methods developed or adopted in this study for analyzing resin distribution, resin loss, and resin pre-cure, and the computer model for calculating refining energy balance can be effective tools for optimizing blowline resin injection systems in MDF mills.