Kikumitsu Inoue

Studies on polymer stabilizers: Part V—Influences of structural factors on oxidative discoloration and thermal stability of polymers

Abstract 2- tert -Butyl-6-(3- tert -butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (GM, Sumilizer® GM) is known as an effective thermal stabilizer which protects polymers against thermal degradation caused by heat or mechanical stress especially under oxygen-deficient atmosphere. Its unique bifunctional stabilizing mechanism has been reported recently. 1 Further studies on the influences of structural factors of related phenols on oxidative discoloration and thermal stability of polymers has shown that 2-(1-(2-hydroxy-3,5-di- tert -pentylphenyl)ethyl)-4,6-di- tert -pentylphenyl acrylate (GS, Sumilizer® GS) not only has a more effective thermal stabilizing effect than GM but also has much higher resistance to oxidative discoloration.

Studies on polymer stabilizers: Part IV—Prevention of oxidative discoloration☆

By a model accelerated oxidative reaction and product analysis, 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (Sumilizer® GM) was found to give a stilbene quinone-type colored product through a quinone methide-type intermediate. The resistance of GM and its analogs against oxidative discoloration was remarkably improved by substitution with a bulky group at the para position to the phenolic OH group.

Studies on polymer stabilizers: Part VI—Relationship between performance and molecular conformation

Abstract 2- tert -Butyl-6-(3- tert -butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (GM, Sumilizer® GM) is known as an effective thermal stabilizer for butadiene type polymers especially under an oxygen-free atmosphere. Further studies on this range of thermal stabilizers has recently shown that 2-(1-(2-hydroxy-3,5-di- tert -pentylphenyl)ethyl)-4,6-di- tert -pentylphenyl acrylate (GS, Sumilizer® GS) is a more effective thermal stabilizer and has resistance to discoloration. In this study, the molecular structures of GM, GS and some of their substituted analogs were determined by X-ray crystallography, and were found to be very similar to each other except for the conformation of the acrylate group. These compounds were found to have an intramolecular hydrogen bonding between the phenolic hydroxyl group and the oxygen atom of the acrylate carbonyl group. IR spectra at various temperatures showed that the performance of the bisphenol monoacrylate type compounds was correlated with the strength of the intramolecular hydrogen bonding. The substitution on the bridged methylene group may restrict the bond rotation and stabilize the molecular conformation which can form the intramolecular hydrogen bonding at high temperatures. This will result in a more effective hydrogen transfer from the phenolic OH groups to enolate radical inducing improved performance in the stabilizing mechanism.