Coatings World - September 2016

Recent Trends in Architectural Coatings

formulations consist of more resin and less pigment.

Another challenge brought about by the lack of VOC in waterborne paint is open time or workability. Without the presence of slow-evaporating solvents, the paint will quickly become tacky when the water evaporates. In low humidity environments, water is quickly released from the paint as it is applied. Therefore, a second technical challenge for material developers is to come up with raw materials that enable longer open time for the paint user. It is not clear if this will be most easily achieved through binder design or through additive design.

The data in Table 1 show the current state of architectural paint VOC regulation in North America.2-7 Clearly, there are areas in which higher VOC coatings are still allowed. However, markets like California, the Ozone Transport Commission (OTC) states and the Lake Michigan Air Directors Consortium (LADCO) states drive manufacturers toward lower VOC formulations. The OTC includes twelve states plus the District of Columbia in the region from Virginia to Maine. The LADCO states include Illinois, Indiana, Michigan, Wisconsin, Ohio and Minnesota. To produce special formulations for each market is quite a logistical and formulation management challenge. For this reason, many coatings companies simply supply coatings nationwide that are compliant with the most stringent regulatory market, currently the South Coast Air Quality Management District of California (SCAQMD). In addition to being the district with the most stringent VOC regulations, SCAQMD is the only district with limitations on colorant VOC. This district is currently in the process of updating its VOC rules for architectural coatings. In particular, the so-called “small container exemption,” which allows manufacturers to sell higher VOC products in quantities of one liter or less, will be restricted. Note that the OTC has recently adopted the latest California Air Resources Board (CARB) standards.

The regulatory landscape can be chal-
lenging to understand. California, for
example, is made up of 35 different air
districts but only a portion have adopted
the current (or even the previous) CARB
standards. Similarly, not every OTC or
LADCO state has adopted its region’s
standards. However, what is very clear
is that the regulations will continue to be-
come more rather than less stringent. The
Clean Air Act requires the EPA to review
the National Ozone Standard every five
years to protect public health. In 2008,
the EPA lowered the standard to 0.075
parts per million (ppm). Very recently,
on October 1, 2015, the EPA lowered the
standard to 0.070 ppm. As a result, more
states and counties in the United States
will be driven to create more stringent lo-
cal VOC standards in order to attain the
new ozone limits. It is unclear today if
and when the EPA will begin the work
of updating the national VOC standard
which today allows far higher VOC levels
than those districts that have implement-
ed more recent rulings.

Alkylphenol Ethoxylates
(APEOs)

Alkylphenol ethoxylates have been in use
for many years because of their surfactant
properties. For the last decade, they have
been severely restricted from use in the
European market due to concerns around
their aquatic toxicity profile and bioac-
cumulation profile. 10 Further concern
exists that their biodegradation pathway
may result in the formation of the cor-
responding alkylphenols, which have bio-
accumulation profiles of greater concern
than the ethoxylated analogs. 11 The most
commonly used APEOs are based on
nonylphenol (Figure 2).

As with many chemical compounds, there is disagreement in the industry concerning the level of risk associated with their usage. In the North American market, formulators have been encouraged to voluntarily eliminate APEOs, although there is no regulation. The author’s company has gradually and voluntarily replaced older generation APEO-containing materials with APEO-free resins and surfactants, even though customers and regulatory agencies are not insisting on it. Indeed, one of the benefits of waterborne coatings is that the application tools can be easily cleaned up with soap and water, therefore it is desirable not to have water soluble chemicals of environmental concern in the formulation. If there is a chance that a material in the paint is toxic to aquatic life, we would rather err on the side of caution and eliminate it.

In-Can Preservation

As VOC levels in architectural coatings have been reduced, preservation of finished paints and also paint ingredients against biological contamination has