Among the synthetic resins for coatings, alkyd resins have the largest output, the most varieties, and the widest range of uses, accounting for about 15% of the world’s total output of synthetic resins for coatings. my country’s alkyd resin coating production accounts for about 25% of the total coatings, and several sets of equipment with an annual output of 4,500 tons have been introduced from abroad.
(1) Alkyd resin varnish
Alkyd resin varnish is composed of medium or long oil alkyd resin dissolved in an appropriate solvent (such as Toluene), added with driers (such as naphthenate salts of metal cobalt, zinc, calcium, manganese, and lead), and obtained through purification. Alkyd resin varnish dries quickly, and the paint film is bright and hard. It has good wear resistance and oil resistance; but because there are residual hydroxyl and carboxyl groups in the molecules, the water resistance is not as good as that of phenolic resin tung oil varnish. It is mainly used as a varnish for furniture paint and color paint, and can also be used as a general electrical insulating paint.
(2) Alkyd resin paint
The most popular among alkyd resin paints is medium oil alkyd resin enamel, which dries quickly and is glossy. It has the advantages of good adhesion, hard paint film, good oil and weather resistance, etc. It can be dried at room temperature or in the oven. It is mainly used for mechanical parts, trucks, agricultural machinery, steel equipment, etc. It can be used indoors and outdoors, and is more suitable for dry spraying.
Iron red alkyd resin primer is the most commonly used paint. It is used as a primer when painting steel objects. It dries quickly and has good adhesion, so it can be used as a volatile paint such as nitrocellulose paint. Primer for paint.
The representative exterior paint made of long-oil dry alkyd resin is bridge topcoat. Its biggest feature is excellent weather resistance. The disadvantage is that the gloss is not strong. Long-oil resin has better Excellent brushability • Suitable for brush construction.
Modified alkyd resin
In addition to oil-modified alkyd resin, you can also use Different polybasic acids, polyols and other resins or monomers modify alkyd resins.
(1) Use pentaerythritol instead of glycerol
Due to its high activity , generally used to make long oil resins. Its brushability, drying, water resistance, weather resistance, color retention and other properties are better than glycerol alkyd resin. If pentaerythritol and ethylene glycol are combined, when the molar ratio is 1:1 , its average functionality is 3, which is the same as glycerol. It can replace glycerol to make short oil resin. Its performance is better than that made by glycerin. The production process of pentaerythritol alkyd resin is simple.
Using trimethylol The alkyd grease-burning paint made of base propylene instead of oil has short drying time, high paint film hardness, good alkali resistance, good color and gloss retention, and baking resistance. It’s also good.
(2) Modification with polybasic acid
If adipic acid or sebacic acid is used instead of phthalic anhydride, the alkyd resin obtained It is extremely soft and can only be used as a plasticizer; use cisgan to replace benzene, and the resulting resin will have high viscosity and light color; use chlorine-containing dibasic acid to replace benzene, and the alkyd resin will have good flame resistance; The resin modified by undecylenic acid has a light color and is not prone to yellowing; using isophthalic acid instead of benzene, the drying rate of the alkyd resin produced is improved, and the heat resistance is also superior.
Others Modified alkyd resin In addition to fatty acids, polyols, and benzene, other synthetic resins or monomers can also be added to the alkyd resin for modification.
