Filtration is an integral process in nearly every facet of life—from living spaces to transportation to food and drink. Coffee and tea are filtered before drinking, while more sophisticated filters are found in home HVAC systems as well as in the air-handling and oil filtration systems of cars. Dairy products are prepared using filtration. And beer, wine, and fruit juice can be clarified using membrane filters.
Filtration can be broadly described as separating one substance from another. One example is separating solids from a liquid, such as metal fragments from engine oil or coffee grounds from coffee. Particulates can be separated from a gas such as air, or one gas can be separated from another, like carbon dioxide from natural gas (methane). Filtration keeps people safer, but engineering effective filtration membranes can pose some unique challenges. Membrane manufacturers are searching for the right ingredients to balance their need to create high-quality membranes with long service lives against production requirements that include faster line speeds and lower defect rates.
Eastman cellulose esters have been used in the manufacture of membrane filters for decades. In 1947, Eastman Kodak was granted a patent on an asymmetric hemodialysis membrane based on a mixture of polyvinylpyrrolidone and cellulose acetate. Over the next seven decades, cellulose esters have been used effectively in many different membrane filtration systems, including microfiltration, ultrafiltration, nanofiltration, reverse and forward osmosis, and gas filtration. Eastman offers a wide range of cellulose ester compositions and molecular weights that allow formulators to fine-tune desirable properties, including water flux, salt rejection, and solubility parameters. In addition, these products are available for use in applications that require food contact compliance. This versatility of choice helps formulators achieve their production and performance goals.
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