Agri-Pure® Polyunsaturated Oils
Regional availability: Europe, Middle East, Africa
Polyunsaturated vegetable oils (sometimes called ‘drying oils’) contain a high proportion of linoleic acid, a C18-chain fatty acid with two double bonds, and (sometimes) linolenic acid, a C18-chain fatty acid with three double bonds; important examples include soybean, sunflower and linseed oil. These ‘polyunsaturated’ fatty chains confer liquidity to the oil, and also make the oil more reactive to heat and oxygen; this reactivity is exploited in the various applications of polyunsaturated vegetable oils.
One of their most important uses is as a raw material in the production of alkyd resins, which in turn form the basis for ink, paint and coating products. The resin comprises a high percentage of fatty chains derived from the parent vegetable oil which, when applied as a thin film, react slowly with the air to form a durable cross-linked film. By adjusting the oil blend, alkyd resin producers can control the drying speed and other properties of the resin.
Linseed oil contains around 50% of linolenic acid, which is the most reactive of the unsaturated fatty chains . Some special applications have developed around this unique and versatile oil: it is a major component in linoleum flooring, and is used for wood treatment and in the production of putty, sealants and mastics.
As well as direct uses, polyunsaturated vegetable oils serve as raw materials for the production of other industrially important ingredients such as epoxidized oils, esters, soaps and polymerized oils. Many of these derivatized oil products also exploit the reactivity to air of the polyunsaturated fatty chains.
The most important characteristic of polyunsaturated vegetable oils is the reactive double bonds they contain. Comparisons between different oils are commonly made using Iodine Value (IV) as the defining parameter; Iodine Value is an indication of the average number of double bonds in the oil - the higher the value, the more double bonds (and hence more reactive) is the oil.
- Agri-pure® AP-22 is a general-purpose polyunsaturated oil used extensively in production of alkyd resins. It has an IV of approximately 128.
- Agri-pure® AP-25 is a premium polyunsaturated oil, with a very low content of linolenic fatty acid chains; this gives it superior resistance to ‘yellowing’, the tendency of vegetable oil-based coatings to discolour over time due to the chemical effects of light and air. It has an IV of approximately 130.
- Agri-pure® AP-30 is based on corn oil, with a balance of unsaturated chains intermediate between AP-22 and AP-25, and an IV of approximately 120.
- Agri-pure® AP-18 is refined linseed oil, with an IV of > 175.
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