Synthesis and use of different types polyanhydrides

Synthesis and use of different types polyanhydrides:

In a typical synthesis, x1 g of each diacid monomer (Suberic acid, Azelaic acid, Sebacic acid, and Dodecanedioic acid) were melted at 140° C. under a nitrogen atmosphere.

Then different amounts (5 equiv., 1.0 equiv., 0.5 equiv., or 0.25 equiv.) of acetic anhydride with respect to carboxylic acid groups were added to the every molten diacid monomer and refluxed at 140° C. for 1 hr. Any excess acetic anhydride or acetic acid was evaporated. The residue was then subjected to melt condensation at 160° C. under vacuum (?10 m bar) for 4 h and characterized by NMR, FTIR, and GPC.

Aliphatic Polyanhydride Hardener APH

APH serves as a hardener for the combination with glycidyl-acrylic resins; it is a polyanhydride of aliphatic carboxylic acids. The partially crystalline compound has a melting point of 80 - 90 °C, an acid number of approx. 300 mg KOH/g and a molecular weight average of about 2,000 g/mol. It is relatively inert against humidity and the hardener has not to be labelled.

Glycidyl-fct.?Polyacrylate????????????????Polyanhydride of Dicarboxylic acids

APH in combination with suitable glycidyl-functional acrylic resins, like acryl TYPE 1436 is used for powder-clearcoats. As an aliphatic hardener it offers excellent weatherability. It shows outstanding flow combined with good mechanical properties and proper chemical resistance even at curing temperatures of only 140°C. This property is possible due to the melting- and reaction-characteristics of the APH TYPE 1381, which is different from aliphatic dicarboxylic acid, where the melting point is very close to the reaction temperature. APH TYPE 1381 is melting at 80 - 90°C and reacts with suitable acrylic-resins at about 140°C.

The powdercoating-film has enough time before crosslinking to spread itself evenly on the substrate.

?See DSC - analysis of acrylic powder-clearcoat systems