Hence, in a chemical
sense the terms alkyd and polyester are
synonymous. Commonly, the term “Alkyd” is
limited to polyesters modified with oils or fatty
acids. A typical alkyd resin is prepared by heating for example linseed oil, phthalic acid
anhydride and glycerol to obtain a fatty-acid containing polyester, as schematically shown
Fig 1.1. Paints based on alkyd resin binders are usually solvent-borne paints, common
solvents being white spirit (a mixture of saturated aliphatic and alicyclic C7-C12
hydrocarbons with a content of 15-20% (by weight) of aromatic C7-C12 hydrocarbons), or
xylene. Although European legislation drives paint development towards water-borne
systems, in order to reduce the amount of VOC’s (volatile organic compounds) in the
atmosphere, solvent-borne paints often show a number of advantages over water-borne
paints. Examples are: easier application properties, wider application and drying tolerance
under adverse conditions (low temperature, high humidity) and a higher level of
performance on difficult substrates, such as heavily stained or powdery substrates
Hence, in a chemical
sense the terms alkyd and polyester are
synonymous. Commonly, the term “Alkyd” is
limited to polyesters modified with oils or fatty
acids. A typical alkyd resin is prepared by heating for example linseed oil, phthalic acid
anhydride and glycerol to obtain a fatty-acid containing polyester, as schematically shown
Fig 1.1. Paints based on alkyd resin binders are usually solvent-borne paints, common
solvents being white spirit (a mixture of saturated aliphatic and alicyclic C7-C12
hydrocarbons with a content of 15-20% (by weight) of aromatic C7-C12 hydrocarbons), or
xylene. Although European legislation drives paint development towards water-borne
systems, in order to reduce the amount of VOC’s (volatile organic compounds) in the
atmosphere, solvent-borne paints often show a number of advantages over water-borne
paints. Examples are: easier application properties, wider application and drying tolerance
under adverse conditions (low temperature, high humidity) and a higher level of
performance on difficult substrates, such as heavily stained or powdery substrates
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