In many markets, dispersion paints for indoor walls also require low-cost solutions that do not have to have high-performance coating properties. Their task is to obtain white, well-covering coatings with high PVC (Pigment Volume Concentration) intended for application by contractors. Such paints require formulation using raw materials that ensure minimum coating properties, and due to the balancing on the border of their parameters, the raw materials must also be appropriately selected.
Contractor’s budget paints can be found on European, Middle East, Asia, but also South America and Africa markets. They are usually intended for quick painting inside facilities that do not require the same properties as in the case of applying standard or premium paints. In Europe, these types of paints are classified by EN 13300 as class 4 or class 5 in terms of scrub resistance ISO 11998 (Figure 1).
Formulating
These paints are formulated to obtain high PVC, while filling the coating with a large amount of fillers and a small amount of titanium dioxide (the most expensive ingredient of the formulation) to obtain an optimally balanced formulation price. It’s not about using cheap raw materials, although they are also cheap, but about achieving a low input cost and ensuring good hiding power through a high concentration of fillers in the formulation. Such paints often use one thickener, usually cellulose ether, and are not expected to have great application properties. To ensure good hiding power, the coating is filled with PVC higher than CPVC to introduce air voids, which additionally increase the hiding power. In such paints, titanium dioxide is highly processed by inorganic surface treatment (ASTM D476 grade III) and gorund calcium carbonate obtained from local mines is used as fillers to minimize transport costs. To increase the fill and introduce a higher ratio of PVC to CPVC above it, kaolin is used as an extending filler with high oil absorption (Figure 2).
It should always be remembered that the binders used in such paints are relatively cheap polymer dispersions, with an MFFT in the range of 12 – 25 °C, with standard parameters that should be selected from the market to ensure balancing of the high PVC and utility of our formulation.
Case studies
To show how important the properly presented binding properties are for polymer dispersions, application studies were carried out for the budget interior paint formulation containing the fillers indicated in Figure 2. For this purpose, 10 styrene-acrylic polymer dispersions (MFFT from 16 to 23 °C) were tested in high PVC formulations (PVC 85%) using the previously mentoined titnaium dioxide, ground calcium carbonate fillers and kaolin extending fillers. The share of each of the two kaolins was 4% by weight in the formulation (total 8% by weight in the formulation), obtaining 10 paints with a solid content of 55% by weight (33% by volume) and a Q = 1.43 (PVC/CPVC). Each formulation was prepared using a cheap recycled solvent as a coalescent, ensuring a reduction of the MFFT to approximately 0-4 °C.
The prepared paints were tested in accordance with ISO 11998, obtaining the results of the loss of coating thickness after 40 cycles of the scrub resistance test performed after 28 days of conditioning in a climatic chamber (23 °C and 50% RH) and classifying the results in accordance with EN 13300. The test results are shown in Figure 3.
The tested polymer dispersions were marked from #1 to #10 and came from various countries in Europe and the Middle East. The results presented in the chart are also supplemented with photos of coatings after tests to show in which samples the substrate was exposed after the end of the 40th cycle.
The best result was achieved by polymer dispersion #8, whose thickness loss after 40 cycles was only 10 µm, which is of course still class 4, but with an excellent result indicating very good binding properties.
Polymer dispersion #8 achieved a Class 2 result for the PVC 80% sample (13 µm thickness loss after 200 cycles), while all other dispersions tested in the project for paints PVC 80% achieved Class 3 or 4 results [results not published in this article].
Polymer dispersion #1 also achieved a very good result for paint PVC 85% , and polymer dispersions #2, #5 and #6 have good prospects. Using them in the formulation, you can also try to increase the PVC to a level of e.g. 86-87% to keep the result still in class 4, but closer to the 70 µm loss limit, in case price optimization would be crucial.
Polymer dispersions #3, #7 and #9 achieved results very close to the Class 4 limit, and polymer dispersions #4 and #10 in paint formulations PVC 85% exceeded Class 4 with results in Class 5.
Summary
Such comparisons for budget paints are extremely important on many levels. Made on the basis of various polymer dispersions from the market, they allow to demonstrate competitiveness and advantage for a specific dispersion manufacturer and provide the market with a binder with good filler binding capacity and high oil absorption to optimize the cost of high PVC formulations. From the point of view of the polymer dispersion producer, it is a competitive advantage tool provided to the manufacturer of such paints, who often does not have its own laboratory or sometimes experience in the selection of binders, especially in markets with difficult access to knowledge. In turn, the manufacturer of such paint needs such materials for easier and faster introduction of this type of paint to the market, for which the R&D stage is not so important, and such technical materials confirm the effectiveness of the polymer dispersion in difficult formulations.
The Spektrochem Laboratory prepares such comparisons and also consults on such projects. If you are a manufacturer of polymer dispersions and would like to expand your portfolio of technical materials for product development with this type of applications, please contact us.
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