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A number of surfactants was selected to be produced at a pilot scale, then given to latex producers, for analysing and finally applying these latexes. In the mean time, the academic laboratories were studying the synthesis of new surfactants and latexes with a special interest for some new polymerisation procedures.
Two classes of surfactants have been selected: the first one was the maleic and fumaric hemiesters (or hemiamides) of fatty alcohols (or amides), and the second was sulfonated polymers.
A set of products belonging to the first class were actually produced, characterized, and used in the synthesis of two kind of latexes: all acrylic latexes for paints, printing inks, and metal coating applications, and vinylic latexes for textile binder, paints and paper coating applications. In addition styrene-acrylic latexes were synthesized for paper coating applications.
One partner was able to work on a smaller rythmus up to the end of the third year. The second one, working on the acrylics latexes, did continue to develop a formulation of latexes for the application of wood stains finishes for which the use of a Einecs registered SURFMER (Surface Maintenance Effectiveness Review) was proved to lead to improvements of the property of blocking, without affecting the other properties. This formulation has been patented, and samples given to selected customers lead to the conclusion that some progress should be made to get better answer to water resistance tests. It is expected to put this formulation on the market very soon.
The academic laboratories were able to prepare and test in emulsion polymerisation:
i) Some new amphiphilic block copolymers PO-EO with a set of polymerisable functions.
ii) Sulfonated polystyrene and polydiene copolymeres (polybutadiene b-ethylene oxide) block co-polymers.
iii) A transurf working with an addition-fragmentation mechanism.
iv) Maleic esteramide surfactants and also nonionic maleic diesters (and diamides) and glycidol derivatives.
v) Polymerizable surfactants from condensation of alcohol monomers with maleic, succinic and sulfosuccinic anhydrides.
The item i) was produced in amounts large enough to be given to the industrial partners P6 and P8 for testing in industrial formulations of latexes (both acrylic and vinylic). Finally, the use of reactive surfactants was tested in newer polymerisation procedure, such as mini-emulsions, micro-emulsions, and controlled radical polymerisations. Some basic properties of latexes, formulated or not, have been studied such as the rheological properties and flow behaviour, surface morphology of films studied by AFM, and finally mechanical properties of the films. In all these studies, the latexes synthesized using polymerizable surfactants were compared to those prepared using conventional surfactants.A lot of effort has been put on the modelling of the mechanical properties of the films reinforced with either polystyrene particles or silica nanoparticles.
The latexes, used as binders of pigments or other charges in many water-borne coating applications, need for the control of their particle size and of their stability the use of surfactants in the recipe used for their production. Detrimental effects are caused by these surfactants on the stability of the latexes and on some properties of the films, due to the possible migration of the surfactants. The main objective of the use of reactive surfactants is to fix these surfactants on the surface of the particles, because of their reactivity in the polymerisation process as comonomers. Another possibility is to use surfactants, which are so strongly adsorbed at the surface of the particles that they cannot be desorbed and migrate.
The strategy adopted was to select surfactants that are easy to prepare with cheap and available chemicals that are also friendly to the environment. Our first choice was orientated by the results of a previous Network of the programme "Human Capital and Mobility" to which several academic partners belonged. The chemicals used were maleic anhydride and fatty alcohols and amines. The selected surfactants were to be produced in a scale larger than the laboratory by one industrial partner and given to two others to produce latexes, respectively acrylic and vinylic, also at a scale large enough to permit evaluation in several end-use applications. In addition to these industrial objectives, the academic partners had several objectives: evaluation of the basic properties of the latexes, such as the rheology, film formation, morphology and the mechanical properties of the films. Furthermore, three partners were involved in the preparation of new kinds of surfactants or new methods of synthesis, as well as new methods of polymerisation, in order to prepare the further selections. These selections were expected to take place at the beginning of the second and of the third year.
The main drawback of that strategy is the difficulty to meet the EINECS regulations. For that reason there are more chances to push the use of polymeric surfactants, which allows us to escape the need to register the selected surfactants if the amount needed in the formulation is above 2%.
In case of success relative to improved properties, a part of the market of surfactants used in polymerisation (40000 t/year) should be displaced. Other benefits expected for the users is to avoid the interferences between the surfactants used for other purposes in the formulations. Other impacts on the environment can be expected in others fields, for instance the rubber industry.
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