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of emulsion stress, concentration, conductivity, temperature and time. Switching from manual to automatic data collection and tuning emulsion stress parameters allowed us to use a chemometric and Design of Experiment (DoE) approach to solve these problem.
The optimum analysis method is comprised of two phases: 1. Foam formation Starting from 60 mL liquid at a fixed concentration in synthetic water, foam is produced by pumping air in to the fluid (air inflation) or by mechanical stress. This period lasts for 100 seconds but the test is stopped earlier if the total volume of liquid and foam reaches 260 mL – fig. 1.
2. Foam decay
Foam volume evolution data are collected through an automatic data recorder. Two meaningful parameters are recorded: maximum foam volume reached defined as the tendency to produce foam – foamability, and time of foam halving which is the tendency to have a stable foam – or foam stability.
All tested semi-synthetic emulsifiable MWFs during benchmarking have been grouped in three main clusters by matching data collected in Bellini’s laboratories, and feedback from the field (fig. 2).
An emulsion that shows a total volume exceeding 200 mL falls in an ‘high risk area’ hence it has high probability to cause foam issues in the field, while under this value foaming problems are related to fluid application. No products were found with a total volume below 85 mL which we defined as being within the ultra-low foaming area. So the next stage was to see how this volume target of below 85 mL could be reached by which method, and how this could be achieved.
Figure 2: benchmarking of semi-synthetics MWFs and areas
Formulation study To develop an ultra-low foaming formulation an intensive screening must be carried out on each surfactant.
For each surfactant solution the fluid’s foaming behaviour is collected, recorded, and the interactions between components are analysed with chemometrics.
The aim is to obtain a semi-synthetic MWF that is low foaming even if the defoamer concentration is zero. To do this a base formulation of mineral free oil, hazard label free and biocides-free semi-synthetic MWF is kept unchanged while the surfactants package is varied. Anti-foaming agents are not included in this first step. Anionic and non-ionic surfactants are tested one-by-one and divided in main categories such as fatty acids, carboxylates, sulfonates, alcohols, amides or the fatty acids Ethylene Oxide or Polyethylene Oxide (EO/PO).
Figure 1: Overlap of 5 tests performed on different products and foam data, each coloured line or bar denotes the characteristics of a different fluid sample.
Foaming is tested in a buffered solution at different water hardness (0°FF, 10° FF and 20°FF) and temperatures (20°C and 40°). As an example fig.3
Continued on page 22 20 LUBE MAGAZINE NO.169 JUNE 2022
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