Antioxidants oligomeric

Additional uses for higher olefins include the production of epoxides for subsequent conversion into surface-active agents, alkylation of benzene to produce drag-flow reducers, alkylation of phenol to produce antioxidants, oligomerization to produce synthetic waxes (qv), and the production of linear mercaptans for use in agricultural chemicals and polymer stabilizers. Aluminum alkyls can be produced from heavy olefin streams and olefin or paraffin streams have been sulfaled or sulfonated and used in the leather (qv) industry. 

Higher Moiar Mass Antioxidants. To address the problem of physical loss of antioxidants, oligomeric and macromolecular antioxidants were developed. A broad range of such antioxidants (both thermal- and photoantioxidants) have been synthesized (159) using a variety of methods (eg, free-radical... 

Polymer-type antioxidants have been prepared by Eriedel-Crafts reaction of -cresol andp- and/or y -chloromethylstyrene in the presence of boron trifluoride-etherate (198). The oligomeric product resulting from the alkylation of phenyl-a-naphthylamine using C12—15 propylene oligomer in the presence of AlCl or activated white clays is used as an antioxidant additive for lubricating oils (199). 

Oligomeric hindered amine light stabilizers are effective thermal antioxidants for polypropylene. Thus 0.1% of A[,Af-bis(2,2,6,6-tetramethyl-4-piperadinyl)-l,6-hexanediamine polymer, with 2,4,6-trichloro-l,3,5-triazine and 2,4,4-trimethyl-2-pentaneainine [70624-18-9] (35) (Fig. 5), protects polypropylene multifilaments against oxidation when exposed at 120°C in a forced-air oven (22) for 47 days. 3,5-Di-/ l -butyl-4-hydroxytoluene [128-37-0] (0.1%) affords protection for only 14 days. 

The above-described issues are the reasons for an increased interest in the synthesis of new antioxidants with the possibility to graft to the polymer backbone or to form polymeric or oligomeric antidegradants. In the last two decades, several approaches have been evaluated in order to develop such new antioxidants ... 

Antioxidant free radicals (A H) produced in this way are relatively stable, but they may react with another lipid free radical to form a quinone [15.3] and [15.4]. Quinones can react with amine or thiol groups of proteins, forming polymerisable yellow or red coloured compounds (Pokorny, 1987). Antioxidant free radicals may also react with either another antioxidant free radical or a lipid free radical, forming dimers [15.5] or copolymers [15.6] and [15.7], respectively. Oligomeric or condensated products of antioxidant free radicals usually possess moderate antioxidant activities too (Pokorny et al, 1974) ... 

Recent scientific investigations of natural polyphenols have demonstrated their powerful antioxidant property (Niki et al, 1995). Several classes of polyphenols have been chemically identified. Some of these are grape polyphenols, tea polyphenols, soy polyphenols, oligomeric proanthocyanidines (OPA) and other natural polyphenols of the flavone class. Rice bran polyphenols are different from the above in that they are p-hydroxy cinnamic acid derivatives such as p-coumaric acid, ferulic acid and p-sinapic acid. Tricin, a flavone derivative, has also been isolated from rice bran. 

Off-line coupling of HPLC with FD-MS has been used by several authors [118-121] for the determination of oligomers, oligomeric antioxidants (such as poly-TMDQ), ozonation and vulcanisation products. Pausch [122] reported on rubbers, cyclic polyurethane oligomers, as well as on the determination of the molecular weight distribution (up to 5300 Da) and oligomer analysis of polystyrene. Also the components of an aniline-acetone resin were deduced from FD-MS molecular weights [122]. 

The evolution of HALS technology to meet the requirements of emerging polyolefin markets and applications is a story of continuous improvement and structure/property optimisation [19-21], Current trends in the industry are toward low-volatility, extraction-resistant, hindered phenolic AOs, such as oligomeric polysiloxane based, high-MW antioxidants... 

To circumvent the inherent problem of loss of additives, different approaches were developed but in all cases emphasis is placed on those additives which initially comply with 1 above. In the case of antioxidants, for example, the trend over the past two decades has been towards the development of oligomeric antioxidants of sufficient solubility in the host polymer. In the 1960 s, Thomas and co-workers... 

Butylated p-Cresol-Dlcyclopentadlene Product. A complex non-staining oligomeric antioxidant marketed by Goodyear as "Wlngstay L" is the butylated reaction ptoduct of p-cresol and dlcyclopentadiene. After trying various analytical techniques, we found that GPC provides the best approach for following the reaction... 

Here we report the use of a readily prepared polymer immobilised TEMPO as a catalyst for alcohol oxidations.15 It was derived from a commercially available oligomeric, sterically hindered amine, poly[[6-[(l,l,3,3-tetramethylbutyl)amino]-l,3,5-triazine-2,4-diyl] [2,2,6,6-teramethyl-4-piperidinyl)-imino]-1,6-hexane-diyl[(2,2,6,6-tetramethyl-4-piperidinylimino]], better known as Chimassorb 944 (MW 3000 see figure 3 for structure). This compound is used as an antioxidant and a light stabiliser for plastics. It contributes significantly to the long-term heat stability of polyolefins and has broad approval for use in polyolefin food packaging.16... 

The pine bark and grape seeds contain the flavonoids oligomeric proan-thocyanidins (OPCs), which offer antioxidant protection against heart diseases and cancers. 

Oligomeric proanthocyanidin Widespread (fruit, vegetables, nuts, COX, LOX [Al, antioxidant]... 

Proanthocyanidins (PAs) are oligomeric and polymeric flavan-3-ols, better known as condensed tannins. They are ubiquitous and one of the most abundant groups of natural phenols (Porter, 1988). PAs affect the texture, color, and taste of many common foods including cereals, fruits, vegetables, and wines. PAs in foods are also of interest in nutrition and medicine because of their potent antioxidant capacities and beneficial effects on human health in reducing the risk of chronic diseases, such as cardiovascular diseases and cancers (Santos-Buelga and Scalbert, 2000 Prior and Gu, 2005). 

Concerns over their potential to function as endocrine disruptors led to a Japanese study on the levels of alkylphenols in 60 rubber products. Such compounds are used as starting materials in the manufacture of a number of mbber additives, particularly oligomeric phenolic antioxidants. The work concentrated on four compounds p-/er/.butyl phenol (PTBP), p-/er/.octylphenol... 

Overall, the research effort to identify health properties of the dried plum relies on two primary signatures for superfruit status—dietary fiber and mixed polyphenols. A Japanese research group has done much of the work on polyphenols, establishing a list of candidates for antioxidant or other cellular effects of prune compounds. Oligomeric proanthocyani-dins, chlorogenic acid, caffeoylquinic acid, various other phenolic acids, and lignans have exhibited antioxidant activity in test-tube studies. Each of these compounds is under research for potential beneficial roles supporting human health. 

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