Green bio-based coalescing additives in latex paint formulations

April 22^nd is Earth Day and an opportunity to bring closer such a necessary topic as sustainability also in the water-based paint industry. While the transition from solvent-based paints to water-based paints is an obvious and undoubtedly necessary topic, the choice of bio-based raw materials for water-based paints and replacing the existing fossil-based raw materials raises some concerns and many doubts .

Renewable raw materials constitute a fairly substantial portfolio on the market. These are often raw materials in which fossil-based ingredients have been replaced with 100% bio ingredients. They are dispersion binders, additives such as defoamers, thickeners, as well as additives aspiring to be coalescents. In the Laboratory of the Research Center for Raw Materials for Water-Thinnable Paints “Spektrochem”, tests of the effectiveness of a promising linear ester additive, 100% based on renewable resources, were carried out in latex paint formulations. This additive is a newly developed auxiliary agent, which was tested in our laboratory for its manufacturer already at the R&D stage in order to optimize its effectiveness in formulations. This additive is hereafter labeled “Bio-based” and does not contain alkylphenol ethoxylate (APEO), biocides, formaldehyde releasers, VOCs or nonylphenol ethoxylates (NPE).

Effect on Minimum Film Forming Temperature

The first test that was performed to evaluate the new additive was the preparation of the MFFT coalescence curve using the ASTM D2354 test method and samples with ladder-dosed new bio-based additive in two polymer emulsions dedicated to wood paints and wall paints. The bio-based additive was compared to a conventional fossil-based coalescent from the market. The results of lowering the MFFT are shown in the graphs below.

When the MFFT reduction curves are made, it can be seen that the new Bio-based additive reduces the MFFT of both polymer emulsions (for wood paints and for wall paints). The effectiveness of MFFT reduction in the tested emulsion of acrylic polymers on wood is greater than that of a conventional coalescent (international brand), as the reduction to 0 °C takes place already at a dose of 3% in terms of total polymer emulsion. In the tested emulsion of acrylic polymers for wall paints, the effectiveness of lowering the MFFT is almost identical to that of the conventional coalescent.

Formulations for studies

The MFFT lowering test on the polymer emulsion alone is not everything. In order to determine the effect of the addition of a new potential coalescent, it was compared in formulations of wood paints and wall paints based on polymer emulsions in which the MFFT was determined. The following paints were prepared for this purpose. For the preparation of both wood & trim and wall paints, 4% of conventional coalescent and 3% of Bio-based coalescent were used, calculated as total polymer emulsion doses that ensured MFFT down to 0 °C.

Wood &trim paint, white semi-gloss, formulation dedicated to the US market.

…and wall paint, white semi-gloss, formulation also dedicated to the US market. The paints were prepared using a two-stage method, first slurries of pigments and fillers were prepared in the grinding process, and then the concentrated slurries were combined with the polymer emulsion and other ingredients.

Test results

The scope of the tests included several parameters, however, in this blog article we present hardness and scrubbability. Below is a graph showing how the hardness develops in both types of paints when the coalescent and its dose are changed. The charts clearly show the achievement of higher hardness of coatings with the use of Bio-based coalescing agent, especially in the wood & trim paint, where the increase in hardness after 10 days was as much as 76%, and in the wall paint it increased by 21%.

Wall paints took part in the scrub resistance tests and when tested according to ASTM D2486 showed almost the same result. A test paint prepared with Bio-based coalescing agents showed a 90% cycle to failure rate compared to a control paint containing conventional coalescing agent. This result is within the precision of the test method, and therefore it can be judged that the coatings have almost identical scrubbability.

Summary

The presented part of the scope of the project devoted to a new coalescent based on bio-based resources shows that properly characterized bio-additives do not have to cause problems with reformulating recipes. Their proper characteristics and guide formulations showing how the results can be achieved in comparison with the raw materials used so far allow to reduce the fear and risk associated with the use of raw materials from renewable resources.

The presented example concerns coalescents, however, similar comparisons with wide characteristics in various formulations are made in our laboratory for other raw materials for water-based paints. If you are interested in our offer, please contact us today.