Economic, versatile, durable and beautiful, it’s no surprise that wood remains an extremely popular choice for various markets around the world.
Working with wood has its challenges. As a natural product, there may be some imperfections caused by natural tree growth.
Knots are a common example. A knot is a normal imperfection that occurs when a branch on the tree becomes injured or dies and is overgrown by the rest of the tree.
These natural blemishes can add rustic beauty to furniture, but they can also create an issue for painters and paint formulators in the form of knot bleeding.
To prevent knot bleeding from occurring, choosing the right resins and additives for wood coatings is important. JONCRYL 9522 is a new 1K acrylic dispersion that helps prevent knot bleeding in stained or pigmented coating systems.
Primed for success
Visible in many wood products, knots resemble a dark circle or swirl and are comprised of thicker and tougher wood than the surrounding growth.
Knot bleeding occurs when resins from sap stain or “bleed” through the top coating of paint. This can create unsightly stains on the furniture and is more common in certain types of wood, such as pine or spruce.
Intended for use in primer formulations, JONCRYL 9522 helps stop knot bleeding by preventing extractives from knots from penetrating the film of the top paint. It plays an important role in coating systems, as it acts as the first defence against discoloration from knot bleeding.
It should be applied along with a topcoat to form a complete coating system.
“This resin needs to be combined with hydrophobic topcoats to deliver other necessary properties,” says Ziniu Yu, Technical Specialist at BASF. “A topcoat with JONCRYL 9530-A, for example, could deliver important chemical resistance, in addition to hydrophobic properties and alcohol resistance.”
A topcoat with strong UV and weathering resistance should be used for outdoor furniture applications.
Waterbased primer
JONCRYL 9522 is unique partly in that it’s an anionic dispersion with excellent barrier properties for knot bleeding. Cationic dispersions have been explored for this application but introduce complexity in formulating.
“Cationic dispersions are commonly used in primers for tannin or knot bleeding resistance,” explains Yu. “However, it is challenging to formulate cationic dispersions with a traditional additive package. In addition, other technologies, like epoxy coatings, 2K solvent coatings or UV coatings, are commonly used as primers for knot bleeding resistance. The challenges then are either VOC or handling. ”
The developed resin, on the other hand, is an anionic resin and has good compatibility with the majority of commercially available additive packages.
This resin also enables a faster drying time for coatings even at ambient temperatures. It can be sanding-ready after only 20 minutes at room temperature, making it easy to seal knots quickly and effectively before bleeding can occur.
“When we say curable at room temperature, we mean that this resin is fairly low in regard to minimum film formation temperature, or MFFT,” says Yu. “That means you can use less coalescence or fewer solvents to make a coating without it cracking. The advantage of that is you can create an effective formulation with very low VOCs.”
Refreshingly renewable
In addition to providing formulators with low VOC formulation capabilities, JONCRYL 9522 is also comprised of ~20% 14C renewable content and can contribute to customer sustainability goals and initiatives.
C14 analysis, or carbon-14 analysis, is used to measure the biogenic carbon content of a solution. The analysis is based on analytical standards such as ASTM D6866, which is a test method developed to determine the biogenic carbon content of solid, liquid, and gaseous samples using radiocarbon analysis.
“Manufacturers can use natural resources such as corn to generate ethanol, and the renewable resource can then be used in the manufacturing process instead of using fossil fuels,” says Yu.
Ready to go
JONCRYL 9522 is now available in North America and is ready to help formulators and their customers reach their sustainability goals and initiatives while boasting strong knot bleeding resistance.
“We have over 50 products right now that have bio-containing C-14 traceable content,” says Diana Rowe, Business Manager at BASF. “Within the coatings industry we have a complex raw material structure and we've used a number of specialty chemicals in the manufacturing of our products. It's about thinking creatively about how we can make our products with different raw materials that ultimately lower the impact on the environment.”
Learn More about JONCRYL 9522