SDS (Figure 8).
Unlike MEKO, the proprietary aminic
complex is not harmful to humans and
only in concentrated form can be harmful
to aquatic life if discharged directly into
watercourses.
Comparative Testing to
MEKO
These “advanced antioxidants” were
evaluated for in-can preservation, film
surface drying and film hardness development vs MEKO. MEKO is completely
volatile and does not interfere with curing while all antioxidants remain, at least
for a period of time, in the film to function properly. In these tests, we chose
a simple, clear alkyd formula based on
a long-oil alkyd resin and used a drier
package consisting of 0.04% cobalt and
0.1% calcium metal based on resin solids.
Results are shown in Figure 9.
Although not as effective as MEKO
with this drier package, the advanced antioxidants at low levels provide excellent
anti-skinning properties to this test system.
The overall hardness and integrity
of the dried film was not compromised
initially or after one week using the advanced antioxidant complex at any of the
levels tested (Figure 10). This confirms
that it does not remain in the film to interfere with crosslinking and final cure.
There is a slight loss of surface dry
using the advanced antioxidant complex
which is due to its lower volatility compared to MEKO and the different mechanism for inhibiting oxidation (Figure 11).
Excessive amounts should be avoided for
these reasons.
Summary – MEKO
Replacement
These less toxic alternatives to phenolic
and oximic antioxidants require less than
half the level of MEKO in most coatings
systems to provide effective anti-skinning
properties. They perform independently
of the oxidative metal drier and are recommended in cobalt replacement strategies. These “advanced antioxidants” are
suitable for clear and pigmented coatings
with no discoloration. However, the optimum level should be experimentally determined as excessive amounts may lead
