Irgafos

CIB -GEIGY Technical Bulletins, Irganox 1098 (Apr. 1974) Irgafos 168 in Combination with Irganox A.ntioxidants (Oct. 1989), CIBA-GEIGY Corp., Ardsley, N.Y. 

Process 5, the conversion of hydroperoxides to alkoxy and hydroxyl radicals, can be interrupted by incorporation of a secondary antioxidant such as phosphites (e.g. Irgafos 168) or thioesters (e.g. Evanstab 12). These materials act as reducing agents, converting hydroperoxides to alcohols and themselves being converted to phosphates or sulfoxides, respectively (see Fig. 16). 

The advantages of automation of extraction under reflux versus manual sample preparation are well illustrated for HDPE/(Irganox 1010, Irgafos 168) (Table 3.7) [118]. No spikes were observed in the former case, as opposed to the latter. Boiling under reflux is considered by some [4] as the best all round conventional extraction method. 

Table 3.7 Extraction under reflux of HDPE/(Irganox 1010, Irgafos 168)...

Applications Extraction is typically accomplished by refluxing the polymer in an appropriate solvent for l-48h [84,199]. In many cases, ultrasonic exposure reduces the extraction time [90,200], According to Table 3.5 there are several reports of US extraction from polymers. Ultrasonic extraction has been used for HDPE/(BHT, Irganox antioxidants, Isonox, Cyasorb, Am 340, MD 1024, Irgafos 168) [56], LDPE/Chimassorb 81 [201], SBR/tri(nonylphenyl) phosphite [200], HDPE/(Tinuvin 770, Chimassorb 944) [114], etc. Nielson [90] compared the recoveries obtained for a variety of analytes from PP, LDPE and HDPE with Soxhlet, ultrasonic bath and microwave oven. For all samples, the ultrasonic extraction could be achieved within 1 h. For LDPE and PP most compounds (except Irganox 1010) were extracted within 10 min. Further experiments by Nielson [56] on extraction from HDPE confirmed these results. Where phosphite antioxidants (such as Irgafos 168) are present the use of the solvent mixture DCM-cyclohexane was preferred as it prevented hydrolysis of the phosphite by extraction solvents such as alcohols [56]. Similarly, phosphite esters also undergo hydrolysis... 

Table 3.10 shows the recovery from PP of Irgafos 168 and its oxidised and hydrolysed by-products by various extraction procedures. As may be observed, One-Step Microwave-Assisted Extraction (OSM) and US lead both to negligible hydrolytic additive degradation. The measured additive decay (by oxidation) is essentially due to the antioxidant activity during the processing (extrusion) step of the polymer and not to the US or microwave heating treatment. 

Table 3.10 Recovery from PP of Irgafos 168 and its oxidised and hydrolysed by-products by different extraction procedures...

As to Irgafos 168 the reader is advised to notice the results of a round-robin involving PP/(Irganox 1076, Irgafos 168) [209a], Ultrasonication at room temperature with anhydrous n-hexane or acetone is a suitable soft extraction mode for the determination of aromatic phosphites and phosphonites, such as Ultranox 626 and Sandostab P-EPQ, which easily degrade in heating extraction procedures [210]. 

SFE has also been used to analyse phenanthrene in PET and PMMA [404]. Nazem and Taylor [405] used SFE to determine antioxidant (Irganox 1010/1076, Irgafos 168) recovery from variously TEGDMA cross-linked polymethacrylates (PMMA, PEMA, PBMA). 

HDPE, LDPE, PP Irgafos 168, Chimassorb 81, Irganox 1010 Acetone/heptane (1 1) trichloroethane [96]... 

Figure 3.15 Microwave extraction of 81 Irganox 1010 ( ), Irgafos 168 (O) and Chimassorb 0.1% (+) from powdered (20 mesh) HDPE with acetone/n-heptane (1 1 v/v). After Freitag and John [96]. From W. Freitag and O. John, Angewandte Macromoleculare Chemie, 175, 181-185 (1990). Wiley-VCH, 1990. Reproduced by permission of Wiley-VCH...

Table 3.30 shows the excellent performance of OSM for the extraction of the medium polar additive Irganox 1010. The reader may compare the results with a round-robin comprising the analysis of PP/(Irganox 1010, Irgafos 168) [209a]. 

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