Dihydric Phenols as Antioxidants in Isotactic Polypropylene

Kotulák

Taimr

1968

Advances in Chemistry

Self Cite

The activity of the 2-alkylhydroquinones (Ia), 2,5-dialkylhydroquinones (Ib), 2,6-dialkylhydroquinones (IIa), and of 2,5-and 2,6-dialkyl-4-alkoxyphenols (Ic and IIb) was studied in isotactic polypropylene at 180 ± 0.1°C. The values ob tained were correlated with hydroquinone (A r1 ) and pyro catechol (A r2 ). All compounds studied (Ia) except the tert octyl denvative were inferior in activity to hydroquinone. Two alkyls of Types Ib and IIa exerted further but non -additive unfavorable effects, particularly the Ib type. Despite over-all low values of A r1 , a weak favorable steric effect of the tert-alkyls is apparent in Type Ia compounds. Etherification even as acetylation of one hydroxyl group (Ic, IIb), has a strong favorable effect. These compounds were the most active antioxidants of the entire hydroquinone series studied; nevertheless their activity did not reach that of pyrocatechol (A r2 < 1).Τ Tnsubstituted hydroquinone reportedly possesses antioxidative properties in various substrates. It is a common chemical and by com parison with pyrocatechol does not stain. However, it is less efficient than pyrocatechol and relatively insoluble, especially in nonpolar mediae.g., the difference in efficiency is evident from the data obtained in the study dealing with the stabilization process of carotene solutions in min eral oil; the ratio (2) of activity of phenol, hydroquinone, and pyro catechol is 1:8:84. A lower efficiency of hydroquinone, compared with pyrocatechol, was also found in the stabilization of fats (5, 7) and poly-191 Downloaded by STANFORD UNIV on February 18, 2015 |

mentioning

confidence: 99%

Dihydric Phenols as Antioxidants in Isotactic Polypropylene

Kotulák

Taimr

1968

Advances in Chemistry

Self Cite

Antioxidants and stabilizers. IL. 1,3,5‐trimethyl‐2,4,6‐tris (1‐tert‐butylperoxy‐3,5‐ditert‐butylcyclohexa‐2,5‐diene‐4‐onylmethyl)benzene: Formation, properties and effect on the oxidation of tetralin and isotactic polypropylene

Lerchová

1974

Angew. Makromol. Chem.

The transformation of the antioxidant 1,3,5-trimethyl-2,4,6-tris(3,5-ditert-butyl-4-hyd-roxybenzy1)benzene (I) by the oxidation with tert-butyl hydroperoxide in the presence of Co(I1)acetylacetonate was investigated. The reaction in tert-butyl alcohol gives rise to product 11 of partial oxidation, while in benzene cyclohexadienone 111 is formed.The oxidation products were defined, and their thermal properties and behaviour in light were determined. The oxidative transformation of trisphenol I leads to a loss of its antioxidative activity. The oxidation products I 1 and 111 at the temperature of their formation d o not exhibit an unfavourable effect on the process of thermal oxidation. However, after heating of the hydrocarbon substrate containing them to a temperature close to their decomposition point they act as initiators. They undergo photochemical transformation already at room temperature and give colour to the polymer. ZUSAMM ENFASSUNG :Es wurdc die Umwandlung des Antioxidans 1,3,5-Trimethyl-2,4,6-tris(3,5-ditert-butyl-4hydroxybenzyl)benzol (I) wahrend der Reaktion mit tert-Butylhydroperoxid in Anwescnheit von Kobalt(I1)-acetylacetonat verfolgt. In tert-butylalkoholischer Losung entsteht das Produkt I1 durch partielle Oxidation, in Benzol dagegen ist das Cyclohexadienon 111 das Hauptprodukt. Die Strukturen der beiden Oxidationsprodukte I1 und 111 wurden bestimmt und ihre thermischen und photochemischen Eigenschaften untersucht. Die antioxidative Aktivitat des Trisphenols I geht durch seine stufenweise oxidative Umwandlung verloren. Die Oxidationsprodukte I1 und 111 haben bei der Temperatur ihres Entstehens keinen negativen EinflulJ auf den Verlauf der thermischen Oxidation. Nach Erwhnen des organischen Substrats in die Nahe ihrer Zcrsetzungstemperatur wirken sie dagegen initiierend. Sie unterliegen schon bei Zimmertemperatur einer photochemischen Umwandlung und verfarben das Polymere.

Antioxidants and stabilizers. L. Transformation of the 1,3,5‐tris(4‐hydroxy‐3,5‐di‐tert‐butylbenzyl)cyanuric acid into alkylperoxycyclohexadienones, their properties and effects on the oxidation of tetralin and polypropylene

Lerchová

1974

Angew. Makromol. Chem.

The transformation of 1,3.5-tris(4-hydroxy-3,S-dI-tert-butylbenzyl~yanuric acid (I), designed as an antioxidant for polyolefins, during its reaction with tert-butylperoxyls was studied. In tert-butyl alcohol two oxidation products, I 1 and 111, are formed, while in benzene the reaction proceeds faster with formation of cyclohexadienone 111. The structures of the oxidation products were confirmed, their thermal properties were measured (by DTA) and the effect on the oxidation of tetralin and isotactic polypropylene was determined. The oxidative transformation makes trisphenol I lose its antioxidative property. The different behaviour of trisphenol I and another important phenolic antioxidant. namely, 1,3,5-trimethyl-2,4,6-tris(4-hydr~xy-3,5-di-t~rt-butylben~yl)benzenc (IV) under the conditions of inhibited oxidation of polyolefins is discussed. ZUSAMM ENFASSUNC;:Die Emwandlung von 1,3,5-Tris(4-hydroxy-3.5-di-tert-butylbcn~yl~yanursaure (I). die als Antioxidans fur Polyolcfine dient, wurdc wahrcnd der Rcaktion mit tert-Butylpcroxyl untersucht. Zwci Oxidationsproduktc I1 und I l l entstehen in tert-Butylalkohol; die Umwandlung liuft schnellcr in Bcnzol, und als Produkt cntstcht hier nur das Cyclohcxadienon 111. F.s wurdc die Struktur der Oxidationsprodukte bestatigt, die thermischen Eigenschaften mittels DTA gemcsscn und dcr Einflul3 auf den Oxidationsverlauf von Tetralin und Polypropylcn verfolgt. WBhrend dcr oxidativcn Umwandlung verlicrt das Trisphenol I seine antioxidativen Eigenschaften. Der I!nterschied in der AktivitBt von Trisphenol I und von cinem anderen wichtigcn phcnolischen Antioxidans, 1,3.5-Trimethyl-2.4,6-tris(4hydroxy-3.5-di-tcrt-butylbcnzy1)benzol (IV), unter den Bedingungcn der inhibicrtcn Oxydation von Polyolefinen wird diskutiert.