Analysis and Chemistry of Aluminum Based Paper Machine Deposits, 1996 Papermakers Conference Proceedings

Aluminum in the form of alum, PAC or sodium aluminate is essential for rosin sizing. Yet these aluminum compounds can also form complex deposits on paper machines. Descriptions of the structure and form that aluminum exists in these deposits has been discussed in the literature. This paper describes the analysis of paper machine deposits, the preparation of laboratory based aluminum deposits and their analyses by FTIR (fourier transform infrared spectroscopy) and X-ray fluorescence spectroscopy. The usefulness of these analytical techniques in the paper industry is discussed. The analytical dam describe the formation of two distinct aluminum precipitates that are found in the pH ranges 5- 7 and 8-10. The precipitates in the higher pH (8-10) region appear to be a form of aluminum hydroxide. The laboratory precipitates at pH 5-7 for both alum and alum/sodium aluminate were found to give IR and X-ray spectra that matched the corresponding spectra of paper machine deposits. These deposits are referred to a aluminum based deposits or complexed aluminum hydroxide. The importance of wet end chemistry and guidelines for the proper use of alum in papermaking are reviewed.