Handbook of Solvents - George Wypych - ChemTech - Ventech!

14.19.2 Recent advances in coalescing solvents 973
14.19.2.5.6 Color
A coalescing agent should be colorless, to prevent discoloration of the product.
14.19.2.5.7 Coalescing efficiency
The effectiveness of a coalescing agent is based upon the MFFT test.
14.19.2.5.8 Incorporation
A good coalescing agent should be capable of addition during any stage of paint manufacture.
Any particular coalescing agent may need premixing prior to addition with varying
amounts of the water and surfactant used in the paint stage.
14.19.2.5.9 Improvement of physical properties
A good coalescing agent can provide a significant improvement in scrub resistance, stain resistance,
flexibility and weatherability.
14.19.2.5.10 Biodegradability
A good coalescing agent should exhibit acceptably rapid biodegradation quickly.
14.19.2.5.11 Safety
The use of the coating system requires that the nature of the coalescing agent should permit
use in the domestic environment. The suitability of such a material is therefore obviously
dependent on its toxicity, flash point, vapor pressure and VOC classification.
14.19.2.6 Comparison of coalescing solvents
From the above, it may readily be seen that AB type coalescing solvents give the best performance
in use. These are the high molecular weight esters and ester alcohols. Other species
have some of the benefits of these materials but have side effects, which render them
less suitable. Minimization of the quantity used tends to be a key financial issue, as well as
offering the best environmental option. In virtually all cases, the efficiency of the AB group
in application is so marked, that they have become the industry standards. Several other
properties, perhaps less important, than efficiency must then be considered when selecting
between these.
These products are usually used in enclosed spaces, where product odor will be vital
for acceptance to the consumer. The dibasic esters are virtually odor free. For legislative
reasons, a solvent not classified as a VOC will be of definite benefit, given the current attitude
to organics in consumer products. Again, the dibasic esters have initial boiling points
considerably above the VOC threshold of 250°C.
The stability of the product towards hydrolysis is also a significant factor in the selection
of the optimum coalescing agent. Effectively, this parameter determines the storage
stability of the product. Again, dibasic esters, particularly those produced from higher molecular
weight alcohols appear to have advantage.
The efficiency of the AB group of coalescents towards almost all polymer types has already
been mentioned. For styrene-acrylics and vinyl acetate - Veova copolymers, the
diesters have a significant edge in performance compared with other members of that group.
This advantage is shown in the reduction in amount required to attain a particular MFFT or
the actual MFFT for a given addition level.
Coasol manufactured by Chemoxy is the blend of di-isobutyl esters of the dibasic acids;
adipic, glutaric and succinic. These acids are produced as a by-product in the production
of adipic acid in the manufacture of Nylon 6,6. The ratio of the acids is 15-25% adipic,