Resorcinol and m- Aminophenol Modified Phenolic Resins

Resorcinol is a very reactive phenol that reacts with formaldyhyde at room temperature. Since the most reactive positions are 4 and 6, the initial condensate, especially when formed at ambient temperatures, is linear. Pizzi et al have determined that in resorcinol-formaldehyde condensates the proportion of 4- and 6-linkages relative to 2-linkages is about 10 to 1, giving a reactivity difference of about 5 to 1.  

The absence of methylol groups in lower molecular weight condensates indicates the high reactivity of resorcinol and the instability of such groups with respect to methylene linkages, allowing only the preparation of resorcinol-formaldehyde novolacs.  

Detailed analysis of resorcinol resins has been performed by Dankelman and de Wit using GLC, HPLC, GPC, and 

Since resorcinol resins are very expensive, only resorcinol and m-aminophenol modified phenolic resins are presently being used. A resorcinol-modified phenolic (20) can be produced by the reactions outlined in Eq. (19). 

The molar ratio of coreacted phenol and resorcinol can best be determined by NMR. m-Aminophenol is about 5 to 10 times more reactive than resorcinol and will react with methylol groups at room temperature to give methylene linkages. Analysis reveals that ring substitution predominates and that the ratio of ring methylene linkages to amino-ring methylene 

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