Sustainable development and the circular economy is not a vision of the future, but the present in the perception of raw materials, also for the production of latex paints. Modifications of the formulations to make them more ecological is not only the elimination of VOC / SVOC, but a real concern for resources in the form of raw materials, the use of which excessively burden the environment or cause that they will soon be exhausted. The growing awareness in various industry sectors is also diffusing to the water-based paint industry, where it has been known for a long time that the mere fact that the formulation is water-based does not make it ecological.
Factors Impacting Critical Performance Features
The first factor that determines the suitability of a bio-resource raw material is the possibility of substitution into the formulation and obtaining the same stability with the highest possible share of bio-resource raw materials. The ideal would be a “plug and play” substitution, i.e. replacing the dispersant in the amount of 1:1 or substituting the polymer dispersion in the same proportion and the behavior of PVC, CPVC, Q, etc.
Unfortunately, ideal solutions only exist in theory, and reality makes that such changes require appropriate research. This especially applies to the conversion of conventional raw materials to raw materials derived from all bio-resources. A positive result is that, after appropriate tests, the desired stability and performance of the coatings can be obtained. This article shows an example based on the BIO-Dispersants project implemented in our laboratory, in which only one of the tested parameters was discussed for public release on the blog – washability in accordance with ASTM D3450, i.e. removing soilant from coatings.
Raw materials and formulation used in the project
The paint formulations were prepared in the Spektrochem laboratory with the assumption of various dispersants and VAE polymer emulsions based on renewable raw materials. All samples based on BIO-renewable materials were compiled to the corresponding reference paint prepared from conventional raw materials not based on renewable raw materials.
The standard VAE binder with a non-volatile content of 60% and a MFFT ca. 3 °C and a Tg ca. 10 °C was adopted as the reference polymer dispersion. VAE binders with various BIO-renewable components were used in the research:
- BIO-based VAE emulsion No. 1 – with 60 % BIO-content*
- BIO-based VAE emulsion No. 2 – with 100 % BIO-content*
*Mass balance involves calculating the renewable content
Other BIO-raw materials used in the formulations:
- BIO-based dispersant No. 1 (70 % active substances) 100% renewable
- BIO-based dispersant No. 2 (70 % active substances) 100% renewable
- Coalescing agent** based on linear ester based on 100 % renewable materials
- Neutralizing amine (50 % active substances) 75 % renewable content
- Defoamer based on 100 % renewable content
**Despite the low MFFT of VAE emulsions, it was decided to use approx. 1% coalescing agent to improve drying and extend the open time
The scheme of preparation of paint samples is presented in Table 1. Renewable resources BIO-content means all non-volatile components from renewable resources in terms of non-volatile components in the liquid paint.
|Paint sample||VAE emulsion||Dispersant||Defoamer||Renewable resources BIO-content|
|Reference #1||Standard VAE||Standard type of sodium salt of polyacrylic acid||Silicone-free polymer-based||0 %|
|#2||BIO-based VAE emulsion No. 1||BIO-based dispersant No. 1||BIO-based defoamer||ca. 15 %|
|#3||BIO-based VAE emulsion No. 1||BIO-based dispersant No. 2||BIO-based defoamer||ca. 15 %|
|#4||BIO-based VAE emulsion No. 2||BIO-based dispersant No. 1||BIO-based defoamer||ca. 24 %|
|#5||BIO-based VAE emulsion No. 2||BIO-based dispersant No. 2||BIO-based defoamer||ca. 24 %|
Other non-renewable raw materials used in the formulations:
- In-can biocide based on mixture of BIT and ZnP
- Rutile TiO2 pigment (grade V compliant ASTM D476)
- Ground calcium carbonate standard fillers
- Mineral thickener based on magnesium aluminum silicate
- Hydrophobically modified HEC thickener
- HEUR thickener (newtonian)
- Corrosion inhibitor for metal cans protection
- Demineralized water with conductivity < 1 µS/cm
The characteristics of formulations constants are given in Table 2:
|PVC (excluding additives)||34 %|
|Volume solid||ca. 45 %|
The prepared paints had an average gloss of ca. 20 GU @60° and 45 GU @85°, which allows them to be classified as low sheen gloss.
The test is performed on the coating obtained on Leneta P121-10N panels after 7 days of conditioning. The test is based on the percentage recovery of the reflectance of the coating after washing with a standardized soil medium. Washing is carried out in a predetermined manner with a sponge with a non-abrasive medium (used in the project), after four cycles of 25 strokes with each refilling of the washing medium and water on the sponge. The reflectance was measured using a 0/45 relectometer.
RESULTS AND DISCUSSION
The performed tests gave very varied results of percentage reflectance recovery. The test results are shown in Picture 2.
Reference paint #1 is the reference for the rest of the test results. Paint #2 containing dispersant No. 1 and BIO-VAE emulsion No. 1 and the proportion of BIO-ingredients at the level of 15 % has slightly better result as the reference paint.
The remaining paints have much lower test results, which shows a much higher difference in dirt acceptance and cleansability. These results show that not only the changed polymer dispersions affect the difference in cleaning ability but also the dispersing additives used.
The biggest difference in the result is seen between samples #2 and #3, which are prepared on the basis of BIO-VAE emulsion No. 1, but with two different BIO-dispersant (paint #2 is based on BIO-dispersant No. 1 and paint #3 is based on BIO-dispersant No. 2).
Samples #4 and #5 have poor cleansability scores, however, and between them, a significant difference can be seen and the effect of the dispersants on the result. The results in this case, however, look completely opposite, because it is BIO-dispersant No. 2 has a better result compared to the BIO-dispersant No. 1.
The presented results show how important role in formulation tests is played not only by polymer dispersions, but also dispersing additives.
The presented results of the washability test for samples with different contents of bio-VAE emulsion as well as with different types of bio-dispersants show that obtaining similar values of washability results to the reference paint is possible (sample #2). In the combinations made, there was just one sample with similar washability properties, but not with the highest percentage of bio-VAE emulsion in the formulation.
“Plugh and play” substitution does not give satisfactory results, hence these results show that modifying conventional formulations and substituting them with raw materials from renewable resources, as exemplified in this article, requires appropriate extensive research in the laboratory.
It is very important to properly supply the starter formulations with comprehensive ladder test results and case studies to support the R&D departments of latex paint manufacturers. Awareness of the appropriate shipment for laboratory work and their facilitation with the use of appropriate technical materials is our common step in the care of our common Home – Earth.
The article is part of the BIO-dispersants project carried out by the Spektrochem Research Laboratory (Architectural Paint Formulation & Raw Materials Lab) in 2020-2021.
The presented article contains only selected characteristics and data of the prepared formulations.