Hardeners dicarboxylic acid anhydrides

The most widely used hardeners are dicarboxylic acid anhydrides (e.g., phthalic acid anhydride, tetrahydro and hexahydrophthalic acid anhydride), long-chain hardener segments with carboxylic end... 

The hardeners used for hot-setting formulations, i.e., for hardening temperatures above 100°C, are preferably dicarboxylic acid anhydrides, dicyandiamide, and certain aromatic amines. The hardening temperatures, which are normally in the range 150-200°C, can be lowered by adding accelerants [49]. 

Horold, S. and Kleiner, H. J., (Clariant GmbH), Phosphorus-containing dicarboxylic reaction product of epoxy resins and phosphorus acid (anhydride) with hardener, U.S. Patent, 1999 5 959 043. 

Araldite HT 907 Cyclohexane-1,2-dicarboxylic anhydride EINECS 201-604-9 Hexahydrophthalic acid anhydride Hexabydrophthalic anhydride HHPA Lekutherm Hardener H NSC 8622 NT 907. Widely used as an epoxy hardener. It may also be used in the manufacture of alkyd resins, plasticizers, and polyesters. Crystals mp = 32 bpi 8 = 145. Buffalo Color Corp. 

The long-chain hardener segments are built up by a simple condensation reaction between a moles of a dicarboxylic acid and a-1 moles of a glycol, as shown in Fig. 5. Further reaction of the carboxylic groups with diepoxide groups then produces long-chain, flexible epoxide compounds, which require the use of corresponding hardeners. The best results have been obtained with anhydride hardeners. 

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