Polymerization of drying oils

Graphical representation of the activation and polymerization phenomena of drying oils is possible by means of the specific refraction and the iodine value74, as shown in Fig. 84. 

In this diagram the triglycerides of pure linolenic, linoleic, oleic and stearic acid are represented by the points D, C, B and A, respectively the values for the specific 

Hydrogenation experiments with the triglycerides are given by the curve D-C-B-A theoretical polymerization curves of the esters (assuming removal of the double bonds without any change in the elementary composition) can be represented by D-D, C-C and B-B.  

Although the diagram does not give a quantitative interpretation of the heat-bodying phenomena of linseed oil it allows an easy comparison of the conjugation and polymerization reactions under different conditions. Chemical and physical analytical methods for the determination of conjugated double bonds (diene value, ultraviolet absorption spectra) confirmed the conclusions about the conjugation phenomena. 

It should be remembered that the iodine value gives no reliable information about the unsaturation of polymerized and conjugated oils60 61 the diagrams discussed above 

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During this process, the position and geometry of the double bond may change. The hydroperoxide mixtures produced by autoxidation and photooxidation are not the same, indicating that different mechanisms are involved. Free radical oxidation can be promoted or inhibited. Deliberate promotion speeds the polymerization of drying oils, and strenuous efforts are made to inhibit the onset of rancidity in edible oils. Frankel has recently reviewed this topic in depth (41) see also (1) for an extensive discussion of oxidation of food lipids. 

Polymerization of drying oils in the presence of sulfur dioxide was first described by Waterman and Van Vlodrop 16). The action of the catalyst is based mainly on its conjugating properties. 

The production of soap by alkaline hydrolysis (saponification) is usually carried out around 100 °C, with glycerol being recovered as a second commercial product. Sodium and potassium salts are used as soaps (Section 5.9). Salts of other metals are used to promote polymerization of drying oils, in the manufacture of grease and lubricants, and as ingredients in plastics formulations. 

Body n. (1) A term used loosely in the paint and adhesives industries to denote overall consistency, i.e., a combination of viscosity, density, pastiness, tackiness, etc. (2) An aspect of fabric quality, akin to drape and hand. (3) A general term referring to viscosity, consistency, and flow of a vehicle or ink. (4) Used also to describe the increase in viscosity by polymerization of drying oils at high temperatures. (5) A practical term widely used to give a qualitative picture of consistency. For Newtonian liquids, both is the same as viscosity. 

On the other hand, the high degree of unsaturation of this type of drying oil has made it a potential monomer for polymerization into useful polymers. More recently, Li and Larock (41) reported the conversion of tung oil to solid polymers by cationic copolymerization with divinylbenzene as a comonomor. The resulting polymers have proven to be thermosetting materials with good mechanical... 

Monolayer reactions have been studied for only twenty years. Striking applications have, however, already been made to other fields of investigation. Biological reactions, characterized by catalytic effects whose selectivity is similar to that of surface reactions, have become less mysterious. The mechanisms of the oxidation reactions in films of drying oils and of polymerization in emulsions of monomers have been clarified, although much remains to be done. It is the purpose of this review to show how novel and impressive are reactions taking place at liquid interfaces. 

The course of the activation process can be followed by measuring the diene value (6), ultraviolet spectra (7), specific refraction, and iodine value 8). This last principle allows an easy detection of the conjugation reactions in connection with polymerization processed of drying oils under different conditions, because of the considerable increase of the specific refraction during conjugation. 

ASTM D1962 Test Method for Saponification Value of Drying Oils, Eatty Acids, and Polymerized Fatty Acids... 

Copolymers as water dispersion have also been synthesized by emulsion polymerization in presence of poly(vinyl alcohol) as protective colloid and evaluated as wood adhesives. The corresponding polymer films have been subjected to mechanical characterization. An improvement in the water and solvent resistance has been observed due to the presence of drying oils. The cobalt acetate, if present as ceitalyst in the adhesive formulation, promotes cross-linking and produces a positive effect on the adhesive performance. 

Drier (1528) n. A composition, which accelerates the drying of oil, paint, printing ink, or varnish. They consist mainly of metallic salts, which exert a catalytic effect on the oxidation and polymerization of the oil vehicles employed and are available in both solid and liquid forms. 

FIGURE 22.12 Oxidative polymerization mechanism of drying oil. With permission of Springer from Li F, Larock RC. Novel polymeric materials from biological oils. J Polym Environ 2002 10 59-67. 

Marshall, J.A. Garofalo, A.W. J. Org. Chem. 1993,58(14), 3675-80 ASTM D1959, Standard Test Method for Iodine Value of Drying Oils and Fatty Acids, Aimual Book of ASTM Standards 06.03 399-401 2000 ASTM D1980, Standard Test Method for Acid Value of Fatty Acids and Polymerized Fatty Acids, Annual Book of ASTM Standards 06.03 418-419 2000. 

Kienle recognized that the condensation of difunctional reactants produced linear polymers and trifunctional reactants produced crosslinked, infusible network polymers. Accordingly, he used a reaction of ethylene glycol and phthalic anhydride in the presence of drying oils to obtain linear polymers that could undergo autoxidation polymerization like that described for oleoresinous paints. Kienle used syllables from the reactants alcohol and acid to coin the word alkyd. 

CH2=CHC = CCH = CH2. a colourless liquid which turns yellow on exposure to the air it has a distinct garlic-like odour b.p. 83-5°C. Manufactured by the controlled, low-temperature polymerization of acetylene in the presence of an aqueous solution of copper(I) and ammonium chlorides. It is very dangerous to handle, as it absorbs oxygen from the air to give an explosive peroxide. When heated in an inert atmosphere, it polymerizes to form first a drying oil and finally a hard, brittle insoluble resin. Reacts with chlorine to give a mixture of chlorinated products used as drying oils and plastics. 

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