Recent Trends in Architectural Coatings
September 2016 www.coatingsworld.com Coatings World | 119
become more challenging. A waterborne
paint formulated at 250 g/L has enough
alcohol solvent in it to prevent growth of
microorganisms in the can. Today, however, most paints are formulated at 50
g/L or below, increasing their ability to
support the proliferation of microorganisms. Unfortunately, the options available to paint formulators are limited.
Formaldehyde-containing preservatives
came under scrutiny many years ago and
have been mostly formulated out of water-borne paints. Isothiazolinone derivatives
have been used effectively as substitutes,
but there are concerns around skin sensitization with such products. In Europe,
new labeling requirements for isothiazolinone derivatives became active in June
of this year. 12 These requirements require
that an “allergen phrase” appear on labels
of paints containing > 1.5 ppm of CMIT/
MIT (5-chloro-2-methyl-isothiazolin-
3-one / 2-methyl-isothiazolin-3-one), >
50 ppm BIT (1,2-benzisothiazolin-3-one),
and > 60 ppm MIT (2-methyl-isothiazo-
lin-3-one). These levels are, for the most
part, below the concentration at which
these materials are useful as preservatives, forcing most companies to put the
statement “Contains [active ingredient].
May produce an allergic reaction.” on the
label. It is not clear if any legislation of
this type will regulate isothiazolinone derivatives in the United States in the future.
Various forms of zinc, silver or copper
preservatives have been made available
to paint formulators as well, although
they can cause associated challenges with
paint stability and film discoloration.
Pyrithione compounds can be used alone
or in combination with other preservatives and are generally recognized as safe.
In summary, today’s architectural coatings are more susceptible to biological
contamination because of their low VOC
content. However, the preservation options are limited due to the regulatory
and safety limitations of these materials.
Some combinations of preservatives,
when used at higher levels, can actually
allow the coating to provide a sanitizing
effect. In other words, bacteria, mold
or viruses from the environment which
come into contact with such a coating
will be killed off by the preservative at
the film’s surface. In the United States,
the EPA strictly regulates the claims that
can be made relative to human health.
Although they allow phrases on the label
that fall under the “treated article ex-
emption,” any further claims require sig-
nificant testing and approval under EPA
protocol. 13 Therefore, it is common to
see label claims related to the dried film
being resistant to microorganisms, but it
is not common to see claims related to
keeping people healthy.
Labor Savings
Since 2009 there has been a major tran-
sition in the North American market to
paint-and-primer-in-one products. These
products are designed to provide primer
properties in the topcoat itself, allowing the
user to complete a job in a shorter amount
of time. If a topcoat can provide adhe-
sion to the substrate, hide imperfections,
block minor stains, and give a uniform ap-
pearance, then the user can eliminate the
step of applying a primer layer. In most
cases, a consumer who is performing a
residential repaint can apply a paint-and-
primer-in-one product. Common sense
should prevail in challenging jobs: it is still
recommended that a traditional primer be
used if the substrate is difficult to adhere
to, if the job involves varying porosity
in the substrate, if heavy stains are pres-
ent, if there is bare weathered wood, or if
the paint needs to cover severe water or
smoke damage. For a typical homeowner
attempting to repaint a room over a week-
end, paint-and-primer-in-one products of-
fer the opportunity to finish the job faster,
along with the convenience of only having
to buy topcoat (rather than primer and
topcoat).
Another labor-saving trend in the
North American market has been a transition to better hiding in architectural
coatings. Several items have contributed
to enable hiding using fewer coats. First,
the development of higher dispensing
accuracy of point-of-sale tinting equipment has allowed for the use of more
concentrated colorants for tinting. The
result is that more color pigment can be
incorporated in paint by a given volume
of colorant, resulting in better hiding. In
addition, the development of paint materials that help to properly space titanium
dioxide in the dried film has contributed
to improved hiding. Third, the introduction of higher hiding color pigments such
as pigment red 254 or pigment yellow
184 allows the formulation of colors with
high contrast ratios. As a result, today it
is more likely that a paint job can be done
in one or, at most, two coats.
Figure 3: A deck restoration coating applied on cracked, weathered wood.
