Water based systems
Natural latex and rubber
The early history of water based systems (emulsion polymerization) is connected with the hystory of latex and the natural rubber.
Many plants and trees exude when cut a white, milk-like liquid which is called latex (from Latin “latex”=milky fluid). Some of these latices coagulate on exposure to air to more or less sticky, elastic masses.
The Olmec people of Mesoamerica extracted and produced forms of primitive rubber from latex-producing trees, such as Castilla elastica as early as 3,600 years ago.
The Maya called such trees “weeping wood” (caa=wood, o-chu=weeping). The spelling was transformed too: Caa ochu become cauchuc in old Spanish and caoutchouc in French.
Synthetic latex and rubber
From 1906, in Farbenfabriken Bayer (Germany), Fritz Hofmann began the search for a synthetic alternative to natural rubber for use in tyres and for the electrical industry. In less than 3 years he managed the synthesis at high temperature of rubber starting from methyl isoprene, which was patented in the Imperial Patent Office in Germany on September 12, 1909.
The idea of using aqueous suspension or emulsion and emulsified monomer was developed starting from the observation of natural latex rubber, which is produced by trees at room temperature in dispersed particles stabilized by colloidal polymers.
In January 26, 1912 Hofmann patented the process for preparing artificial rubber starting from isoprene in viscous aqueous solutions of albumin. In 1913 he patented in USA a caoutchouc substance and process fo making the same which comprised polymerizing a butadiene in the presence of an aqueous colloidal solution.
In 1912, his research on rubber earned him the gold medal Emil Fischer, who granted the Association of German chemists.
In the years immediately following World War II, nearly 16 million American servicemen and women returned to civilian life, setting off an unprecedented housing and baby boom. By 1950, housing starts soared to 1.7 million, ten times as many as in 1944. And all of these new homes needed paint, both inside and out. Solvent-based paints, which dominated the market at the time, were made with alkyd resins. They were odorous, toxic, flammable and especially hard to clean up. Despite the paint’s trying nature, sales were brisk. There was a lot of room for improvement. And profit. That is, if an alternative could be found. Two chemists, Benjamin Kine and Gerald Brown, suggested that aqueous acrylic emulsion technology could be used to make terrific house paints. The acrylic emulsions that would develop in the years ahead have some amazing qualities. Emulsion polymers are prepared in water and stabilized with surfactants, molecules that are hydrophilic (“water-loving”) in one segment and hydrophobic (“water-hating”) in the other. Emulsion polymers begin forming when a free radical — acting as an initiator — breaks a double bond between two carbon atoms in an acrylic monomer, starting a reaction that causes as many as 10,000 monomer units to bind together into a polymer chain. As these chains take shape, they grow into submicron-sized spheres. Within each sphere there are about 300 acrylic polymer chains.