HLAS reactive binder in detergent granulation: relationship between phase behaviour and wetting and adhesive properties.
Doctoral thesis, University of London.
The main aim of the work reported in this thesis is to gather experimental evidence of the relationship between HLAS (Linear Alkylbenzene Sulphonic Acid) phase changes and binding performance in detergent granulation. In order to fulfil this goal a novel micromechanistic apparatus, the EC-MFB (Environmentally Controlled Micro Force Balance), capable of characterising binder-particle interactions, such as contact angles and liquid bridge adhesive forces, in an environmentally controlled glove box, has been designed developed and commissioned. Linear alkylbenzene sulphonic acid (LAS acid or HLAS) is a reactive binder used in industrial detergent granulation processes. The neutralisation of HLAS with sodium carbonate particles during granulation generates Sodium Linear Alklybenzine Sulphonate (LAS-Na), one of the world’s most used anionic surfactants for washing powder formulations. The reaction neutralises HLAS to increasing degrees, depending on the amount of acid reacted to form the salt. During granulation the binder has the dual function of forming physical links between the particles and participating in the neutralisation reaction to form LAS-Na. Both HLAS and LAS-Na have been found to be highly hygroscopic. The experimental investigation described here is aimed at establishing whether the extent of HLAS neutralisation and the binder water content influences the wettability and adhesive strength of individual liquid bridges holding particles together during the granulation process. HLAS being a reactive binder , the characterisation of the wetting and adhesive behaviour is complicated by their strong dependency on the kinetics of the binder-powder reaction. Hence, a novel approach to reactive binder studies is presented here, with the experiments carried out using inert particles and acid that has been partially pre-neutralised with Na2CO3. Contact angle and spreading velocity measurements show that the higher the degree of neutralisation the lower is the tendency of the liquid to wet the particles. Moreover, it will be shown that particle wetting is strongly dependent on binder water content and relatively humidity (RH). A “sticky regime map” is presented as a function of neutralisation and water content distinguish between wetting and non-wetting conditions. This highlights the importance of controlling the environmental conditions, both during the granulation process and the storage of the product materials.
|Title:||HLAS reactive binder in detergent granulation: relationship between phase behaviour and wetting and adhesive properties|
|UCL classification:||UCL > School of BEAMS > Faculty of Engineering Science > Chemical Engineering|
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