Chemistry Reference
In-Depth Information
products mean that there may be significant quantities of unethoxylated alcohol or
phenol in the mixture as well as some molecules with significantly more OE units,
which will be sulfated in subsequent steps and can have a significant impact on the
characteristics of the final product.
2.4.1.4. Sulfated Fats and Oils
A final class of sulfated alkyl surfactants is that of the sulfated fats and oils in which
the sulfate esters are obtained by the treatment of a variety of hydroxylated or unsa-
turated natural fats and oils with sulfuric or chlorosulfonic acids. These materials
represent the oldest types of commercial synthetic surfactants, dating back to the
original turkey red oils. Because of the nature of the starting materials and prepara-
tion processes, the sulfated fats and oils are chemically heterogeneous materials
whose properties are very sensitive to their history. In fact, the preparation of such
materials may correctly be considered to be more art than science. They will con-
tain not only sulfated glycerides similar to those discussed above but also sulfated
carboxylic acids and hydroxycarboxylic acids produced by hydrolysis of the start-
ing materials. With the increased availability of more chemically pure surfactant
materials, the use of the sulfated fatty oils has decreased considerably. They do
still have their uses, however, especially where purity is not a major concern and
cost is important.
From a technological point of view, the aliphatic sulfate ester surfactants have
not attained a wide range of applicability, even though they are heavily used in
areas where their properties fit the need. With few exceptions they are used as deter-
gents, wetting agents, or both, with good detergency favored by the longer hydro-
carbon chains and good wetting by the shorter homologs. The more chemically
pure materials, especially the n-alkyl sulfates such as SDS, have found application
in a number of areas related to emulsion polymerization and, of course, represent
probably the most intensively characterized family of surfactants known.
2.4.2. Sulfonic Acid Salts
Although chemically similar to the sulfate esters, the sulfonic acid salt surfactants
can differ considerably in properties and chemical stability. As with the sulfates,
there exist a wide variety of hydrophobic groups that control the properties and
applications of these materials. Some of the major groups or sources are discussed
briefly below.
Some sulfonic acids were no doubt produced in the early sulfuric acid processing
of the ''sulfated oils'' in the late nineteenth century. The first commercially available
sulfonate surfactants, however, were produced as a result of raw-materials shortages
in Germany during World War I. Some short-chain sodium alkylnaphthalene sulfo-
nates were developed and despite relatively poor detergent properties were found to
be good wetting agents and are still used as such today. The sulfonates in this series
have also found use as emulsifying agents and dispersants in several agricultural
and photographic applications. The postwar expansion of the chemical industries
of Great Britain, Germany, and the United States led to the development of a
