Preparation of water-in-oil emulsions using microporous polypropylene hollow fibres:: Conditions for producing small uniform droplets

The preparation of water-in-oil emulsions was investigated in a Microdyn membrane module consisting of 40 hydrophobic polypropylene hollow fibres with a mean pore size of 0.4 mum. The experiments have been carried out using demineralized water as the disperse phase, mineral oil Velocite No. 3 as the continuous phase, and polyglycerol polyricinoleate as the emulsifier. The mean droplet diameter increased with increasing transmembrane pressure and with decreasing the emulsifier contentration. At the emulsifier content of 10 mass % and transmembrane pressure of 28 kPa the mean droplet diameter was only 0.27 mum, which is 33 % lower than the membrane pore size. One of the possible explanations is that water cannot completely displace oil from the interior of the pores due to high viscosity of oil compared with water. Therefore, some amount of oil phase was retained inside the pores reducing the effective pore diameter.