Polyolefins, additives Antioxidants

The metal coordination complexes of both sahcylaldehyde phenyhiydrazone (91) and sahcylaldoxime provide antioxidant (92) protection and uv stabihty to polyolefins (see Antioxidants). In addition, the imines resulting from the reaction of sahcylaldehyde and aromatic amines, eg, p- am in oph en o1 or a-naphthylamine, can be used at very low levels as heat stabiLizers (qv) in polyolefins (93). 

Applications The broad industrial analytical applicability of microwave heating was mentioned before (see Section 3.4.4.2). The chemical industry requires extractions of additives (antioxidants, colorants, and slip agents) from plastic resins or vulcanised products. So far there have been relatively few publications on microwave-assisted solvent extraction from polymers (Table 3.5). As may be seen from Tables 3.27 and 3.28, most MAE work has concerned polyolefins. 

Uses Antioxidant for rubbers, SBR, polymers, polyacetals, linear saturated polyesters, PVC, polyolefins, polyamides antioxidant for food-grade polymers in side seam cements for food-contact containers Regulatory FDA 21CFR 175.300, 178.2010 Manuf./Distrib. Ciba Spec. Chems./Plastic Addit. http //www. cibasc. com Trade Name Synonyms Irganox 1098 [Ciba Spec. Chems. Switzerland http //www.cibasc.com, Ciba Spec. Chems./Plastic Addit. http //w. cibasc.com] Lowinox HD 98 [Great Lakes http //www. greatiakeschem. com]... 

Di-/ f2 -butyl-4-methylphenol, which is commonly known as BHT (butylated hydroxy toluene), is a widely used phenoHc antioxidant in the stabilization of oils, mbber, and polyolefins (44). BHT is also one of the few phenolic antioxidants approved by the FDA as a direct food additive where it is used to retard the oxidation of naturally occurring oils in food. 

A large number of hindered phenoHc antioxidants are based on the Michael addition of 2,6-di-/ f2 -butylphenol and methyl acrylate under basic catalysis to yield the hydrocinnamate which is a basic building block used in the production of octadecyl 3-(3,5-di-/ f2 butyl-4-hydroxyphenyl)propionate, [2082-79-3], tetrakis(methylene-3(3,5-di-/ f2 butyl-4-hydroxylphenyl)propionate)methane [6683-19-8], and many others (63,64). These hindered phenolic antioxidants are the most widely used primary stabilizers in the world and are used in polyolefins, synthetic and natural mbber, styrenics, vinyl polymers, and engineering resins. 2,6-Di-/ f2 -butylphenol is converted to a methylene isocyanate which is trimerized to a triazine derivative... 

Mixtures of a titanium complex of saturated diols, such as TYZOR OGT, and a titanium acylate, such as bis- -butyl-bis-caproic acid titanate, do not have a yellowing or discoloring effect on white inks used to print polyolefin surfaces (506). The complexes formed by the reaction of one or two moles of diethyl citrate with TYZOR TPT have an insignificant color on their own and do not generate color with phenol-based antioxidants (507). The complexes formed by the addition of a mixture of mono- and dialkyl phosphate esters to TYZOR TBT are also low color-generating, adhesion-promoting additives for use in printing polyolefin films (508). 

The stabili2ation of polyolefins used to insulate copper conductors requires the use of a long-term antioxidant plus a copper deactivator. Both A[,Ar-bis(3,5-di-/ A-butyl-4-hydroxycinnamoyl)hydra2ine (29) and 2,2 -oxamidobisethyl(3,5-di-/ A-butyl-4-hydroxycinnamate) (30) are bifimctional. They are persistent antioxidants that have built-in metal deactivators. Oxalyl bis(ben2yhdenehydra2ide) (28) is an effective copper deactivator when part of an additive package that includes an antioxidant. 

Polyolefins such as polyethylene and polypropylene contain only C—C and C—H bonds and may be considered as high molecular weight paraffins. Like the simpler paraffins they are somewhat inert and their major chemical reaction is substitution, e.g. halogenation. In addition the branched polyethylenes and the higher polyolefins contain tertiary carbon atoms which are reactive sites for oxidation. Because of this it is necessary to add antioxidants to stabilise the polymers against oxidation Some polyolefins may be cross-linked by peroxides. 

Marcato, B., Guerra, S., Vianello, M. and Scalia, S. (2003). Migration of antioxidant additives from various polyolefinic plastics into oleaginous vehicles, Int. J. Pharm., 257, 217-225. 

Goydan, R., Schwope A. D., Reid R.C., and Cramer G., 1990, High temperature Migration of Antioxidants from Polyolefins. Food Additives and Contaminants 1,323-337. 

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