Polyolefins antioxidants

Vitamin E is used in a variety of applications of which the main ones are enhancement of animal feeds, vitamin supplements in humans, polyolefin antioxidant, food additives, cosmetics and toiletries and in medicinal applications. More uses of vitamin E are coming to the limelight and uses are multiplying after availability of the synthetic product. In fact, it is the fastest growing vitamin in the world ... 

Uses Antioxidant stabilizer for styrenics, polyolefins, polyamide, PVC, urethane and acrylic coatings, adhesives, elastomers, cellulosics metal deactivator replaces BHT in polyolefins antioxidant, stabilizer in food-grade polymers, acrylic food pkg. in food-pkg. adhesives Regulatory FDA 21CFR 175.105,177.1010,178.2010 Manuf./Distrib. Aldrich Allchem Ind. ChemService Ciba Spec. Chems./ Addit. GE Spec. 

There are 130 additives currently under restriction, including the tin stabilisers used in PVC, the polyolefin antioxidant Irganox 1076, and process aids of the bis-ethoxylated amine type. 

Pobedimskii, D.G., Kurashov, V.l. and Kirpichnikov, P.A. (1983) Metal Complexes with Ligands - Organic Phosphites as Polyolefin Antioxidants. /. Polym. ScL, Polym. Chem. Ed., 21,55-66. 

Due to similarities in their rheological and thermal properties, E/CO resins (with CO levels up to at least 5 per cent) and LDPE of comparable melt index (MI) and molecular weight distribution (MWD) behave in sheet extrusion and blown film processing very much alike. Both E/CO and LDPE, when similarly stabilized with typical polyolefin antioxidants, exhibit very good processing thermal stability, even with high levels of reprocessing, and at temperatures of up to at least 260 °C. 

Ciba Specialty Chemicals Additives for Polyolefins Antioxidants (AO) Processing Stabilizers ... 

The 2-imino-4-thiazolines may be used as ultraviolet-light stabilizers of polyolefin compositions (1026). 2-Aminothiazole improves adhesive properties of wood to wood glue (271). Cbmpound 428 exhibits antioxidant properties (Scheme 242) (1027). Ammonium N-(2-thiazolyl)dithio-carbamate (429) is a bactericide and fungicide used in industrial products such as lumber, paint, plastics, and textiles (1037). Compound 430 is reported (1038) to form an excellent volume of foam coating in aluminum pans when ignited with propane. 

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). 

Both thermooxidation and photooxidation of polyolefins can be prevented by using the same antioxidants as those employed for the stabilization of polypropylene, ie, alkylated phenols, polyphenols, thioesters, and organic phosphites in the amount of 0.2—0.5% (22,25). 

Sesamex [51-14-9] (Sesoxane) (30) is a synergist oflow toxicity, acute oral LD q (rat) = 2000 2270 mg/kg, for pyrethrins and allethrin. 6,7-Dihydroxy 4-methylcoumarin has been offered as an antioxidant for phenoHcs and polymers, and as an anthelmintic. 2,4,5-Trihydroxybutyrophenone has been available as an antioxidant and light stabilizer for polyolefins, waxes, and foods. Isoflavones, eg (31), have been patented as components of antioxidant compositions for foods and cosmetics (qv) (97). 

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... 

Polymers. In combination with various metal salts, sorbitol is used as a stabilizer against heat and light in poly(vinyl chloride) (qv) resins and, with a phenohc antioxidant, as a stabilizer in uncured styrene—butadiene mbber (qv) compositions and in polyolefins (see Heat stabilizers Olefin POLYMERS Rubbercompounding). Heat-sealable films are prepared from a dispersion of sorbitol and starch in water (255). Incorporation of sorbitol in coUagen films gready restricts their permeabiUty to carbon dioxide (256). 

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). 

D. Burdick, S. Laermer, S. Young, and P. Zambetti, "A New Primary Antioxidant System for Polyolefins," presented 2l. ddditives 95 Clearwater,... 

Hindered Amines. Hiadered amines are extremely effective ia protecting polyolefins and other polymeric materials against photodegradation. They usually are classified as light stabilizers rather than antioxidants. 

When used alone at low temperatures, diaLkyl thiodipropionates are rather weak antioxidants. However, synergistic mixtures with hindered phenols are highly effective at elevated temperatures and are used extensively to stabilize polyolefins, ABS, impact polystyrene (IPS), and other plastics. 

Hindered amines are generally classified as light stabili2ers. The three selected products are derivatives of 1,6-hexanedianiine and are effective antioxidants for polyolefins. 

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. 

Phenylalkanes Bis-[2-hydroxy-5-methyl-3-( 1 - (VII) methylcyclohexyl)phenyl]methane Very slight Most powerful phenolic antioxidants. Widely used in polyolefins and some usage in PVC. 

Phosphites Tris-(p-nonylphenyl) phosphite (X) No Widely used in conjunction with conventional stabilisers (q.v.) in PVC. Some types appear to be useful heat and light stabilisers in polyolefins. Function primarily as peroxide decomposers rather than chain-breaking antioxidants. 

As with most polyolefins and polydienes the presence of copper has a strong adverse effect and most antioxidants are relatively ineffective. In these instances quite good results may be achieved by the use of 1% of a 50 50 phenol alkane-dilauryl thiodiproprionate blend instead of the 0.1-0.2% of antioxidants more commonly used in polypropylene. 

It has been only found that some antioxidants and light stabilizers show the ability for partial inhibition of thermal destruction of the polyolefins. 

---