by Ingegärd Johansson, PhD, Surfactant Specialist Akzo Nobel Surface Chemistry AB, Surfactants Europe, R&D

The term “surfactant” is short for “surface active agent”, a name which describes the most important property of a surfactant, i.e. a material that is active at surfaces and interfaces. A typical surfactant is composed of a hydrophilic (water-loving) and a hydrophobic (water-hating) part. This is reflected in the production procedure where at least one step is to combine these two parts into one molecule. The sources should consequently be split into the origin of the hydrophilic part and the hydrophobic part respectively.

The hydrophobic part of the surfactants that are used in big volumes comes mostly from renewable sources like fatty acids from plants or animals, i.e. oleochemicals. Typical sources are coconut, palm kernel, rapeseed, sunflower, soybean, tall as well as lard, tallow or different fish oils. All these hydrocarbon chains are straight, even numbered and more or less saturated. Typical surfactants made from these starting materials are fatty acids as such or their sodium or potassium salts, alpha-sulfonated fatty acid esters, ethoxylated fatty acid esters, fatty acid ethanol amides and fatty acid ethanol amide ethoxylates. More or less hydrolyzed oils, i.e. mono or di- glycerides are also used as surfactants.

If the fatty acid is reduced to alcohol or reacted with ammonia or ammonia derivatives other categories can be made like fatty alcohol ethoxylates, fatty alcohol glucosides or fatty amines and ethoxylated fatty amines.

Looking at the hydrophilic part then brings us to the carboxylic function, different sackarides, glycerol, and of course non carbon containing functionalities like sulphates, sulphonates, phosphates.

During last century the development of more efficient surfactants gave rise to new hydrophobic structures containing more or less branched hydrocarbon chains as well as hydrophilic parts like ethoxylates. The latter constitutes a very important category of temperature sensitive, less hard water dependent, non charged surfactants which are used in cleaning agents esp for degreasing purposes. However both of these development routes meant using rawmaterial from petrochemical sources.

This emphasizes the need for new raw materials that come from nature and could be used to produce the modern surfactants. One way of solving this problem is to go into the field of bio refineries and use ethanol as starting material. From ethanol ethylene can be made and etylene oxide to be used for ethoxylation. Another derivative is acetaldehyde which could be condensed into longer chains with more or less branched structures. Thus both the needs sketched above could be fulfilled via the bio ethanol route.

Another issue concerns the competition between different users of oleochemical raw material. The natural oils and fatty acid esters as well as ethanol itself has an increasing use as fuels for different vehicles and as energy source overall. Being in the surfactant business dependant on renewable sources one might be worried how this will influence the market for these raw materials.

Source: www.nnfcc.co.uk