Chemical addition to wet webs using foam application

In papermaking, the conventional way to add chemicals to the web is to dose them into the fiber stock and form the paper afterwards. However, in many cases, adding chemicals directly to the stock is challenging. For example, strength aids tend to increase flocculation in the stock, which limits the addition amounts of those aids. The need for better performance of paper (and paperboard) products has given rise to the need for functionalization of paper. Adding such functional chemicals to the stock is usually rather inefficient. Hence, novel methods are need-ed to add chemicals to the paper bulk. One such method is dosing chemicals to the wet web via foam application. In this study, we built a laboratory-scale sheetfed dynamic foam application device and utilized it to study addi-tion of starch to wet bleached chemithermomechanical pulp (BCTMP) paper handsheets. The impact of parameters such as vacuum level, the amount of added chemical, and the viscosity of the foaming liquid on the penetration of starch into the wet web was explored. Starch penetration into wet webs was measured via iodine-potassium iodide staining, followed by image analysis. According to our results, controlling the viscosity of the foaming liquid gives the best possibility to control the penetration.

Automated summary

The conventional way of adding chemicals to paper is challenging in many cases, leading to inefficiency in functionalization of paper. One novel method is dosing chemicals to the wet web via foam application, which allows better control over the penetration of starch. The impact of parameters such as vacuum level, amount of added chemical, and viscosity of the foaming liquid on starch penetration into wet webs was studied.