New decorative and convenient solutions for glass coatings
Decorative alternatives to through-colored glass
When it comes to giving glass a colored appearance, today there are alternatives to coloring molten glass. The variety of colors and surface textures can be increased significantly. If glass is coated rather than produced by the traditional method of using colored glass melt, only one - transparent – glass melt instead of several different needs to be operated and stocked. Therefore any special coloring can be obtained in small batches without the use of any possibly toxic heavy metal salts. In addition, polyurethane-based glass coatings satisfy even very demanding requirements on the properties in daily use.
Another advantage of this method is the easier recycling. There is no need for sorting differently colored glass. During the remelting process any organic material is simply combusted leaving a clear transparent product.
Polyurethane coatings provide additional functional properties The coloring of glass with polyurethane-based coatings opens the opportunity to add special properties enhancing its practical value. The polyurethane coating can perform functional tasks like the protection from mechanical and chemical stress. It increases scratch resistance, adds shatter protection and makes it more dishwasher proof.
Functional polyurethane-based coatings can increase the resistance to internal stresses (burst protection). With a polyurethane coating the internal stress resistance of lightweight glass bottles can be increased to the standard of regular bottles.
New effects
Other than the characteristics mentioned above like abrasion- and chemical resistance, the polyurethane dispersions show particular rheological characteristics. They make it possible to formulate effect coatings like metallic, pearl or other special effects. In addition the formulation of softfeel-coatings with an exceptional surface haptic is possible if highly flexible systems are used.
The product range for glass coating
Bayer MaterialScience offers amino resin-crosslinkable polyester and polyarcrylate dispersions and also a one- and two-component polyurethane based product range of raw materials for glass coating. Compared to other alternatives Bayhydrol® polyurethane dispersions offer some distinct benefits:
best combination of durability and flexibility
high resistance against chemical agents, e.g. caustic solutions and acids
very good adhesion on glass surfaces
excellent scratch and abrasion resistance
Due to the increasing need to reduce VOC emissions, water based one-component baking systems are more and more replacing the conventional two-component polyurethane systems. Waterbased glass coatings can be formulated with products like these:
In combination with Bayhydur® BL 5335 for coatings with high scratch resistance and resistance against solvents and caustic soda solution (an NMP-free version is being worked on)
