Since the invention of alkyd resin in 1927, a new breakthrough has occurred in the coating industry. The coating industry has begun to get rid of the combination of drying oil and natural resin. The traditional method of making paint has truly become a sector of the chemical industry. The raw materials used are simple, the production process is convenient, and the performance is excellent, so it has developed rapidly.
Use alkyd Coatings made of resin have the following characteristics:
①The paint film forms a highly reticular structure after drying, which is not easy to age and has good weather resistance. Good, the luster lasts forever.
②The paint film is flexible, strong and resistant to friction;
③ It has good resistance to mineral oil and alcohol solvents. The water resistance, insulation and oil resistance of the baked paint film are greatly improved.
Alkyd resin paint also has some disadvantages:
① It dries quickly and forms a film, but it takes a long time to complete drying.
②Poor water resistance and alkali resistance;
③Although alkyd resin paint is not a paint, it has basically not escaped the scope of fatty acid-containing organisms, and its performance against moisture and heat, mold and salt spray cannot be fully guaranteed. Therefore, all should be considered when selecting varieties.
Introduction to the raw materials of alkyd resin
Alkyd resinis obtained by the polycondensation of polyols, polybasic acids and other unit acids through esterification. Among them, the most commonly used polyols are glycerol and pentaerythritol, followed by trimethylolpropane, sorbitol, xylose, etc. The most commonly used polyols are phthalic acid, followed by isophthalic acid, terephthalic acid, and maleic acid. Liver acid, sebacic acid, etc.
Unit acids are commonly used vegetable oil fatty acids, synthetic fatty acids, and rosin acids. Among them, those that exist in the form of oils such as tung oil, linseed oil, Dry oils such as catalpa oil and dehydrated castor oil, semi-drying oils such as soybean oil, and non-drying oils such as coconut oil and castor oil. The above-mentioned oils in acid form are hydrolyzed to obtain mixed fatty acids and synthetic fatty acids, undecylenic acid, benzoic acid and their derivatives, etc.
The most commonly used polybasic acid in the production of alkyd resin is glycerin, with a functionality of 3. The most commonly used polybasic acid is phthalic anhydride. Its functionality is 2 when benzene and glycerol react in an equivalent ratio.
The initially obtained ester functionality is 4. If two such molecules react, cross-linking will occur between the molecules to form a body shape. Structural grease pouring. The resin does not melt when heated and is not soluble in solvents. It is a thermosetting resin and has no value in coatings. Later, modification with fatty acids was used. This step was extremely important. It not only made the modified polyester suitable for use in coatings, but also became the backbone material of the coating.
The above-mentioned modification method is to introduce fatty acids with one functionality to reduce the total functionality. For example, glycerol, The reaction of the three components of benzene tincture and fatty acid can be regarded as under appropriate circumstances, the fatty acid and glycerol react first to form a difunctional product, and then the benzene tincture reacts with it, then the ratio of functionality is 2:2, easy Generates a chain structure without gelling, forming a thermoplastic resin. The resin is meltable when heated and soluble in solvents, and can be used as coatings.
