The Waterborne Symposium

Emerald Kalama Chemical has developed a new coalescent to address challenges in the industry for improving key properties of coatings while minimizing volatile organic compound (VOC) values of waterborne latex coating formulations.  Environmental regulatory groups continue to lower VOC limits in coatings, and traditional low vapor pressure coalescents can lower VOC while improving gloss values and scrub resistance.  However, block resistance, hardness development, and dirt pickup resistance can be challenging to achieve with these materials in low PVC formulations.  Emerald’s new coalescent increases coalescent efficiency, hardness development, dirt pickup resistance, and blocking resistance even when compared to commonly used high VOC coalescent aids.  With respect to specific binders, improvement in wet edge, open time and scrub resistance values have been observed.  Emerald is continuing to develop new technologies which also contribute to improved properties in deep base formulations as well as flash rust prevention.

A special measuring geometry, rotating at low constant angular velocity through a paint film, was developed to record the increase of torque during drying under constant temperature and humidity conditions, thus giving access to a qualitative and quantitative differentiation of additives regarding their impact on the drying behavior of the paint.  A series of additives with different hydrophilic lipophilic balance values was tested in two paints, an acrylic lacquer with a pigment volume concentration of 36.2% and an indoor/outdoor dispersion paint with a pigment volume concentration of 78.6%.  Interestingly, the additive performance was found to be dependent on the paint composition, suggesting that specific interactions between the additives and the paint ingredients are mainly responsible for influencing the drying process.  This method represents an interesting alternative for additive testing and identification of the best choice to achieve the desired impact on the drying behavior of waterborne dispersion paints.

Siloxane-based additives are critical tools in coating applications because their structures can be varied to provide a broad range of performance benefits in many types of formulations and chemistries.  Surfactants and defoamers are some of the more commonly recognized additive classes, but many other functionalities can be derived from siloxane chemistries; particularly attributes related to surface control such as flow and leveling, slip, scratch resistance, and haptic properties. This extensive range of performance is achievable due to the broad flexibility inherent in siloxane chemistry, allowing a fine-tuned balance of compatibility, incompatibility, and surface activity.
As with many additive types, a broad range of functionalities creates many options for improvement and innovation but also presents challenges in finding the right additive and optimizing to achieve the desired performance. This paper will attempt to clarify the general structure-property relationships that drive the performance attributes of siloxane additives and detail the continuum that exists between wetting, leveling, defoaming and slip within this chemistry class. Surface control properties and testing will be reviewed and related to recent evaluation work conducted in developing novel siloxane surface control additives.