An interesting review of the different materials that must be taken into account when making a correct formulation of paintings for the architectural sector.
by José Tomás Rojas*
Architectural paintings are known by several names: Emulsified Paints, Rubber Paints, Water-Based Paints, Vinyl Paints, and surely others, depending on the country in question. Perhaps the most curious name is that of rubber paints, which surely must come from natural rubber.
In its origins, a natural emulsion was obtained by extracting the bark of the rubber tree (Hevea Brasilensis). This material was used, among other things, to manufacture the tires of the first cars, and generated a very profitable business for the countries that produce this raw material, including Brazil and Venezuela. Thanks to science, it was possible to develop a synthetic rubber, the so-called styrene butadiene latex, an emulsion, whose success in terms of performance ruined natural rubber, meaning the end of this industry, and the origin of another: the development of emulsion polymers for different purposes, including the manufacture of paints. Hence, the terms emulsion and rubber have an interesting history in common, which explains the name given to paintings of this type, in some countries.
Below I mention the materials and describe their components:
Latex
The main component of water-based architectural paints are latex or latices. These materials are manufactured through emulsion polymerization. In it, the monomers that make it up, such as Butyl acrylate, Acrylic Acid, Styrene, Acrylic Vinyl, are mixed with water, stabilizing agents, surfactants and initiators, forming with them, a stable emulsion, through mixture. Each drop of emulsion contains an equivalent fraction of each material, which is polymerized, individually, with the help of temperature, giving rise to latex. Depending on the monomers that make it up, they can be Vinyl Acrylics, Acrylic Styrene, 100% Acrylic, among others.
Pigments
The pigment that is most used is Titanium Dioxide, Rutile grade. This has an explanation, since about 60% of the Architectural Paintings that are manufactured, are white. Usually grades with a lot of surface treatment are used, to improve dispersion in process.
In order of importance follow the yellow and red Iron Oxides, the blues and greens of phthalocyanin, and the yellow and red pigments, of organic base. In the past, yellow and orange inorganic-based pigments (Chromium Yellow, Molybdate Orange) were used, but their use is very restricted, since these pigments have an important lead content, and their impact on health has been demonstrated.
Today, the use of pigments, with the exception of white, has been replaced by pigment dispersions, which facilitate incorporation into the process, saving the time that was invested in the dispersion phase. These new materials have also allowed the automation of the dosing of dyes, as they are also called.
Thickeners
Although it is customary to place thickeners in the category of additives, I prefer to give them a separate category, in view of the great importance that these materials have on the performance of paints. The most used are those based on Hydroxy Ethyl Cellulose (HEC). Associative thickeners are also used, generally derived from acrylic polymers in emulsion. These materials differ from cellulosics, since they require the presence of an alkaline medium to develop their effect, and in general require a more careful control in plant for their dosage, since an excess of use can seriously disturb the characteristics of the paint, which does not happen with cellulosics.
Additives
They are used in various types. We have the additives that are used to facilitate the production process. Among them we have dispersing agents, emulsifying agents, water softeners, pH regulators, defoamers and process bactericides. Other types of additives are those that are used to ensure the integrity of the material in the container, such as bactericides, and biocides that guarantee the integrity of the film, such as fungicides / algaecides.
Extenders or Loads
The most used, with length, are calcium carbonates. There is an important variety; micronized, ultra micronized, white, gray, natural and synthetic. It is followed in order of importance by Aluminum Silicates, also known as Kaolines, which can be natural or calcined. To a lesser degree, Wallastonites and other natural silicates are used.
In conclusion, we can affirm that the materials for the manufacture of emulsified paints are relatively uncomplicated, and easy to acquire. However, on their own, they do not constitute a good painting. Only the careful combination of them, in the right proportions, will give rise to a coating whose cost-performance ratio makes it attractive to the market. This process is known as Formulation.
* I take the opportunity that this column gives me, to ask you to have Venezuela in your thoughts. My country is going through a difficult situation at the moment, from which, hopefully, we can recover soon.
* José Tomás Rojas. JTROJAS Pinturas, F.P. You can send your comments to the email [email protected]
