Date of Award
Master of Science in Chemical Engineering - (M.S.)
C. L. Mantell
The objective in this work has been to determine, through a critical literature survey, the possible application of ultrafiltration, and other related techniques, towards the solution of certain problems encountered in the research and testing of various pigments.
Among these problems may be mentioned the following:
- The determination of water-soluble salts in pigments, which when dispersed in water to leach out the salts, tend to peptize, thus being unfilterable through the usual filter paper. Among these pigments are the following: iron blue, certain chrome yellows, pigment green B, copper maroon, and several others. It may be added that these pigments do not give a clear supernatant liquid when subjected to ordinary centrifugation.
- The determination of "bleed" tests in water, alcohol, and other solvents on the above mentioned pig: eats, as well as several others. In the normal "bleed" test on pigments, the pigment is shaken in the solvent and then filtered through ordinary filter paper. The filtrate is compared with that of a standard to determine the intensity of the "bleed". If the pigment tends to peptize at all, the filtrate will contain same of the pigment, giving an erroneous test.
- The determination of particle size of pigments. Among the various methods of determining particle size may be mentioned the following: ultracentrifugation, ultramicroscopy, light microscopy, electron microscopy, light scattering, x-ray scattering, nitrogen adsorption, and several others. All of these techniques are either very tedious or require the use of expensive equipment. In addition, most give only average values for particle size.
- The determination of "over-size" particles. In many applications of pigments it is undesirable to have present, particles or aggregates larger than a certain size class. Such over-size particles may present such problems as poor texture in printing inks and enamels, poor tinting strength, and less transparency in inks and metallic finishes.
- The separation of pigment from a vehicle, such as in a paint, has always been a problem for the analyst. Other techniques rarely effect a complete separation of the pigment from the vehicle or of the vehicle from the pigment.
- The separation of one pigment from another in a mixture. Many pigments are sold as mixtures, either as a blend of two or more related colors or of a color extended with a white. A notable example would be a "chrome" green, which is a mixture of a chrome yellow and an iron blue. Ultrafiltration may be applicable in cases where the differ?ent components of a mixture are of widely different particle sizes.
In order to fully evaluate the possibilities in applying ultrafiltration to these problems, the following aspects of the technique are covered: terminology, historical background, preparation of the various types of ultrafilters, mechanisms involved in ultrafiltration, and applications in various fields. Only those applications and techniques used in other fields, which may possibly apply to the pigment field, are included, and it is not intended that this should be considered as a comprehensive survey of the entire field of ultrafiltration.
Manger, Charles Walter, "Ultrafiltration in the pigment field : a critical literature survey" (1953). Theses. 2220.