Лако-красочные материалы — производство

Despite the wide range of properties of unmodified alkyd resins mentioned above, alkyds suffer from some inherent limitations. In general, coatings based on alkyd resins have poor water, alkali and chemical resistance, yellowing tendency and poor exterior dura­bility and gloss retention properties. In order to partly overcome these limitations, alkyds are frequently chemically modified. Che­mical […]

The key properties of alkyd resins controlled by type and content of fatty acid or oil are drying time, hardness and yellowing properties. The degree of unsaturation and presence of conjugated unsaturation in fatty acids increases the curing rate and improves their drying time. Oils with a high content of linoleic acid produce non-yellowing films, […]

Most common and traditional alkyd resins are classified on the basis of their oil content (wt% of oil in final resin) as: • Short oil alkyd resin: oil content <40 % • Medium oil alkyd resin: oil content 40 to 60 % • Long oil alkyd resin: oil content 60 to 70 % • Very […]

There are two major chemical processes used for manufacturing alkyds: the fusion process and the azeotrope process (solvent process). The fusion process is an old method of manufacturing alkyd that involves fusing all components at elevated temperature. An inert gas is continuously purged in the system to avoid oxidation as well as to drive off […]

Besides fatty acids, other monofunctional acids are often used in small quantities in certain alkyd resins (Figure 2.11). Rosin was ini­tially used to modify the drying time of alkyd resins because of its low cost, but it impairs durability of coatings. Some aromatic mono­functional acids such as benzoic acid or p-tert-butylbenzoic acid are used in […]

Although they are not the only type used, difunctional aromatic acids are most commonly used in alkyd resins, of which phthalic anhydride is the most important and commonly used diacid because of its avai­lability, low cost, relatively low melting point, and high reactivity. Isophthalic acid is another dibasic acid that is frequently used for alkyds […]

A diverse range of compounds are used as polyols for alkyd resins (see Figure 2.10). Polyols used in alkyds are generally at least tri­functional to permit branching and can provide the alkyd with hydroxyl groups for further reaction. Glycerol, having two primary and one secondary hydroxyl, is the traditional polyol used in alkyds; however, it […]

2.3.2.1 Fatty acids and oils Fatty acids and oils are one category of primary raw materials for alkyd resins. Their chemistry and compositions have been discussed in Section 2.2.3. Soybean oil, linseed oil, tall oil, sunflower oil, and safflower oil are common raw materials for air-drying alkyds, while coconut oil and castor oil are important […]

This process is faster and involves only one stage. As the name suggests, fatty acids along with polyol and dibasic acid are reacted in a single step via direct esterification. This process gives more latitude for selection of polyol component and is useful when polyols other than glycerol are to be used in a formulation. […]

This route for manufacture of alkyds, shown in Figure 2.9, is not widely used, and is only used when the diacid is insoluble in a reaction mixture or has a high melting point, for example, long oil alkyds based on terephthaleic acid or isophthalic acid. The reac­tion requires high temperature (270 to 290 °C) to […]