Wax emulsions are used in the glass industry in the following applications:
- Glass Fiber Sizing
- Cold-end treatment of bottles
Glass fiber sizing
Wax emulsions based on Maleic Anhydride grafted Polypropylene wax are used to size glass fibres so that they become compatible with the PP compound that they need to reinforce. These very sophisticated products are often used in combination with Silane based coupling agents, among other functional additives. Key parameters of such emulsions are excellent stability and non-yellowing.
Cold-end treatment of bottles
All glass bottles and jars are coated with a very thin layer of Polyethylene wax, which is applied via a dilute wax emulsion right after the annealing step. The wax coating allows for slip and gloss and helps to increase the life cycle of returnable bottles.
Important features of these products are food contact approval, low foaming and hard water stability. The dry wax coating should not interfere with the adhesion of paper and plastic based labels. That means that labels should still stick well right after filling, but should also still come off during a caustic washing step after return.