Natrosol™ Plus hydrophobically modified hydroxyethylcellulose

Biostability and Enzyme Resistance
Biostability of waterborne paints and coatings is a complex and multi-faceted subject, but is often broken down into three general areas:

• Viscosity loss due to cellulase enzyme attack on cellulosic thickeners
• Resistance of the finished paint to growth of microorganisms (including bacteria and mold)
• Resistance of the dried paint film to surface growth of mold and mildew

The first two items above are generally mitigated through the use of biocides in the paint formulation. Ashland does not offer biocides, but they are at times used in Aquaflow™ nonionic synthetic associative thickeners for storage stability.

Enzyme production is a by-product of bacterial activity. Enzymes can be found in process water and finished paint, even after bacterial activity has been killed through the use of biocides. In particular, cellulase enzymes can be introduced in to the paint making operation through untreated water and raw materials. Over time, the presence of cellulase enzymes will break the bonds between adjacent unsubstituted anhydroglucose units in the cellulose backbone. This reduces the molecular weight leading to significant viscosity loss in paint.

Ashland offers superior biostable cellulosic thickeners in our Natrosol B-series HEC and Natrosol Plus modified HEC thickeners. These high performance workhorse thickeners for latex paints and coatings are manufactured in a way so as to protect the backbone from enzyme attack. The end result is vastly superior viscosity retention over time, even when paint is intentionally dosed with cellulose enzyme (at 1.0 ppm).

Spatter Resistance
Associative thickeners thicken via several mechanisms including hydrogen bonding, chain entanglement and hydrophobic association. The latter mechanism enables lower molecular weight polymers to thicken efficiently by forming a three-dimensional network in solution.