USES OF INDUSTRIAL FISH OILS 265 



or saturation of the oils. Other examples of this type of process will be 

 discussed later. 



Chemical reactions of the carboxyl groups in fish oils afford the other 

 important class of reactions. In a saponification or ''fat splitting" process, 

 fish oils can be made to yield fatty acids and glycerine. The resultant 

 fatty acids possess many of the chemical properties of the original oil 

 triglycerides with the added advantage of the higher reactive carboxyl 

 groups. The carboxyl end of the fatty acid chain can be readily converted 

 to other functional groups, which may be more advantageous than the 

 carboxyl group, depending on the use of the product. An example of this 

 is in the preparation of fatty alcohols, which possess hydroxyl rather than 

 carboxyl groups^l This and similar reactions will be discussed later. 



A special class of reaction applicable to fish oil is one that takes advan- 

 tage of the reactivity of the hydrogen atoms attached to carbons adjacent 

 to the ethylenic bonds. These hydrogens in the ''allylic position" exhibit 

 particular reactive or acid-like properties. An example of this reaction 

 applied to unsaturated fatty acid methyl esters is the bromination using 

 N-bromosuccinimide^^. 



Present and Past Uses of Fish Oils 



Commercial fish oils are used by industry today in a variety of 

 ways''-^^'^^ Many of the applications are not generally known because of 

 their confidential nature to the manufacturers using fish oils. However, 

 there are several applications that are well known and are discussed below. 



Protective Coatings. Paints and varnishes are perhaps the most widely 

 recognized industrial products from fish oils used in the United States at 

 this time. The use of fish oils in protective coatings was reported by 

 MattiP^ Crude fish oils are generally high in saturated fatty acid con- 

 tent (approximately 30 per cent), thereby preventing the formation of 

 hard, tack-free films. Even a ''cold-pressed" oil having iodine values of 

 190 to 200 and with from 60 to 70 per cent of saturated and mono- 

 unsaturated acid groups removed results in dried films that lack hardness 

 and strength^^ Therefore, fish oils, such as those from menhaden, must 

 be heat-bodied or thermally polymerized to yield products that dry faster 

 and give harder films than untreated oils. More recently, alkyd resins 

 produced from fish oils have provided a most versatile, durable, and eco- 

 nomical class of film binders. Coatings produced from phthalic anhydride 

 fish oil alkyds and cyclopentadiene copolymers of fish oils are major steps 

 forward in the protective coating field. 



Linoleum and Oil Cloth. Linoleums and oil cloths may include fish oils 

 in their formulations. A process of linoleum manufacture involving blend- 

 ing of fish oil with Unseed "Unoxyn" is described by Fritz ^°. Here linseed 



