Polyolefins heat stabilizers

PY 151, Cl NO. 13980 Yellow H4G Green shade good fastness to light and solvents finds use in PVC and polyolefins heat stability to 425°F... 

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). 

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). 

UV3346) offer superior compatibility, low volatility, excellent resistance to extraction and contribute to heat stability. The nonextractable nature of these additives makes their quantification challenging. The quantification of Chimassorb 944 in polyolefins is possible using an UV absorption method after dissolution of the polymer [596]. 

The specific requirements for organic pigments in terms of heat stability result from the temperature levels at which individual polyolefins are processed. Standards have been developed to test the heat stability of pigments in polyolefins [33] (see also Sec. 1.6.7). 

In contrast, diarylide yellow pigments are used widely throughout the plastics field. This is particularly true for P.Y.13,17,81,83, and 113. The first German edition of this book reported that the heat stability (Sec. 1.6.7 1.8.3) of these pigments, for instance in polyolefins, was up to 200 to 270°C for 5 minutes, depending on the depth of shade. Results that have been published in the meantime [8], however, require rectification of these numbers. 

P.Y.17 is also frequently used in polyolefins, sometimes in the form of pigment preparations. Its heat stability in these media was said to be about 220 to 240°C, but must now, as a result of the detected thermal decomposition of diarylide yellow pigments in plastics, be limited to 200°C. This tendency to decompose excludes P.Y.17 from recommendation for use in polystyrene, in which the pigment largely dissolves under the processing conditions. The same is true for ABS. 

P.Br.23 shows excellent heat stability in polyolefins. 1/3 SD samples containing 1 % TiOz, as well as transparent colorations at 1/3 SD in HDPE are stable to exposure to 300°C for 5 minutes. In injection molding, P.Br.23 considerably affects the shrinkage of the plastic at 220°C, an effect which diminishes with increasing temperature (Sec. 1.8.3.2). 

In terms of heat stability, 1/3 SD polyolefin systems containing P.V.23 withstand exposure to 280°C. In lighter tints, this value is appreciably lower 1/25 SD... 

Lubricants are used in rigid PVC (PVC-U) in amounts 0.3-0.8% (metallic soaps acting primarily as heat stabilizers are used at levels up to 1.5 %). In polyolefins, calcium or zinc stearates used as antiacids provide the lubricating effect at 0.1 to 0.2%. Fluoropolymers are used specifically for L-LDPE. 

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... 

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