Alcoholysis process

Alkyds are made by different processes, depending upon the available raw materials, final product properties and cost. The alcoholysis process (also called the monoglyceride process) or acidolysis process is used when oil is one of the starting materials, while direct esterification uses fatty acids as starting materials, with better control of final resin properties, but generally at higher cost. 

This is the most commonly used route in alkyd resin manufacturing. Oils, being cheaper raw materials as compared to corresponding fatty acids, are naturally preferred for alkyd resins, but the oil does not react readily with acid or alcohol. Therefore, to avoid a heteroge- 

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Non-drying oil resins are soluble only in Aromatic hydrocarbons. They are used with amino resins for stoving finishes for appliances. Medium resins are used as plasticisers for cellulose nitrate. Along with natural oils several natural occurring and synthetic acid like resin (abiotic acid) pelargonic acid and isooctanoic acid are added to modify alkye resins. The alkyd resins are obtained by two processes, i.e., (1) Fatty Acid Process and (2) Alcoholysis process. 

Alcoholysis Process In alcoholysis process the oil is heated with polyol at 240°C in presence of a base like calcium hydroxide. The principal product formed is a monoglyceride. The dibasic acid is then added and further esterification done ... 

For the esterification reaction, there is of course no way of distinguishing between the two proposed mechanisms. The fact that protonated acetic acid reacts with H2lsO to produce CH3C(OH)18OH+ in a thermoneutral exchange with displacement of H20 can be accommodated by either of the mechanisms. Failure to observe the alcoholysis process (76) cannot be rationalized in terms of one mechanism or the other. 

Different chemical procedures may be used for the synthesis of alkyd re si ns. The choice is usually dictated by the selection of the starting ingredients. Procedures include the alcoholysis process, the fatty acid process, the fatty acid-oil process, and the acidolysis process. 

The majority of the early procedures for the cleavage of the (3-lactams /Vj-CT bond deal with hydrolysis and alcoholysis processes under rather harsh acid or basic reaction conditions. One example is the ring opening of (3-lactam 2 under acidic conditions to afford almost quantitative (3-amino ester 3, a component of the dimeric cyclic depsipeptide onchidin, 1, isolated from the marine mollusc Onchi-dium sp., Scheme 1 [54]. 

Surprisingly few studies have been directed towards the development of noncinchona alkaloid-based catalysts for the alcoholative ASD of meso-anhydrides, or indeed any of the enantioselective alcoholysis processes. Uozumi has reported a series of (2S, 4R)-4-hydroxyproline-derived 2-aryl-6-hydroxyhexahydro-lfi-pyr-rolo[l,2-c] imidazolones which mediate the methanolytic ASD of ds-hexa-hydrophthalic anhydride in up to 89% ee when employed at the 10 mol% level for 20 h at —25 °C in toluene [186]. Additionally, Nagao has described the use of a bifunctional chiral sulfonamide for the thiolytic ASD of meso-cyclic anhydrides in up to 98% ee when employed at the 5 mol% level for 20 h at rt in ether [187]. 

Alcoholysis and Glycerolysis Alcoholysis is the esterification reaction between an alcohol and a TAG (Figure 2a). In the alcoholysis of vegetable oils, a TAG reacts with an alcohol in the presence of a strong acid or base, producing a mixture of alkyl esters and glycerol. The alcoholysis process is a sequence of... 

G. Pruckmayr, Alcoholysis Process for Preparing Poly-(Tetramethylene Ether) Glycol, US Patent No.4,230,892 (1980). 

In comparing the fatty acid and alcoholysis processes, it is evident that the reactions involved are quite different. The interchange reactions involved in alcoholysis and the subsequent reaction with the polybasic acid are slow compared to polyesterification. Performance comparisons indicate that performance differences do exist between alkyds of the same composition that are prepared by the fatty acid and monoglyceride (alcoholysis) processes (6). 

The alcoholysis process ulso is readily adaptable to continuous operation. Procedures in general are similar to those used for continuous esterification processes. 

In the second method, known as the alcoholysis process, the drying oil is heated with the glycerol in the first stage of the reaction, at about 240 °C. This is usually done in the presence of a transesterification basic catalyst to form monoglycerides ... 

Intellectual property assigned to this company covers an alcoholysis process using higher alcohols aimed at the production of higher esters of TA for use as plasticisers from scrap PET rather than the straight recovery of monomers or other PET precursors [200-202]... 

Vegetable oil-based polyesters 103 Monoglyceride / alcoholysis process... 

Reaction scheme for synthesis of polyester resin by an alcoholysis process. 

Alkyd resins cannot be prepared by simply heating a mixture of oil, polyol and dibasic acid. Because of the preferential reaction of the polyol and acid, a heterogeneous mixture of polyester and oil is obtained which has no value as a surface coating vehicle. There are two main methods whereby useful resins are prepared commercially, namely the fatty acid process and the alcoholysis process (often called the monoglyceride process). 

After the monoglyceride is formed, the dibasic acid is added and the mixture is treated as in the fatty acid process again either the fusion method or the solvent method may be employed. Acidolysis is an alternative to alcoholysis, but generally requires a higher temperature and is seldom used. Compared to the fatty acid process, the alcoholysis process gives less reproducible results but is usually cheaper to run. 

O—C17H31 Scheme 16.16. The alcoholysis process for alkyd resins. 

The alcoholysis process has lower raw material costs than the fatty acid process but higher production costs, since it is a two-step process. The decision whether to produce from oil or from fatty adds is thus largely based on the amount of od/fatty adds in the formulation (see short oil/long oil resins, discussed in Section 16.5.4). 

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