Synthesis,characterization, and application of oligomer‐type‐based phosphites

Organic alkyl and aryl phosphites are effective antioxidants and photostabilizers with applications in a wide range of polymers. The primary role of phosphites is to decompose hydroperoxide. However, aryl phosphites are also capable of reacting as antioxidants by affecting the kinetics. In particular, oligomer‐type phosphites have a greater effect on polymer degradation because of their high compatibility, reactivity, and solubility with almost all polymers. Generally, phosphites are sensitive to hydrolysis. In order to overcome this hydrolytic sensitivity in phosphites, a novel hydrolytically stable oligomeric phosphite incorporating a sterically hindered aromatic alcohol (2,4‐di‐tert‐butyl‐6‐methylphenol) that gives hydrolytic stability to the phosphite was synthesized and characterized, and its performance as an antioxidant for polypropylene was investigated. J. VINYL ADDIT. TECHNOL., 22:146–155, 2016. © 2014 Society of Plastics Engineers     

Synthesis,characterization, and application of a hydrolytically stable liquid phosphite

Organic alkyl and aryl phosphites are effective antioxidants and photostabilizers with applications in a wide range of polymers. The primary role of phosphites is to decompose hydroperoxide. However, aryl phosphites are also capable of reacting as antioxidants by negatively affecting the kinetics. In particular, liquid phosphites have a greater effect on polymer degradation because of their high compatibility, reactivity, and solubility with almost all polymers, but they are sensitive to hydrolysis. In order to overcome this hydrolytic sensitivity in liquid phosphites, a novel hydrolytically stable liquid phosphite incorporating a sterically hindered aromatic alcohol (2,4‐di‐tert‐butyl‐6‐methylphenol) that gives hydrolytic stability to the phosphite was synthesized and characterized, and its performance as an antioxidant for polypropylene was investigated. J. VINYL ADDIT. TECHNOL., 22:163–168, 2016. © 2014 Society of Plastics Engineers     

Phosphororganische Antioxidatien. X [1]. Über die hydroperoxidzersetzende Wirkung von Phosphiten,Phosphoniten und Thiophosphiten

Organophosphorus Antioxidants. X. The Hydroperoxide Decomposing Action of Phosphites, Phosphonites and Thiophosphites The kinetics and mechanism of reactions of phosphites, phosphonites, thiophosphites and hydrogenphosphites with cumyl (CHP), t-butyl (TBHP) and α-tetralyl (THP) hydrogenperoxides has been studied by means of ³¹P-n.m.r. spectroscopy, high performance liquid chromatography and iodometric titration. All three valent phosphorus compounds studied initially react with hydroperoxides stoichiometrically to give the corresponding PO products and alcohol. Some species are able to decompose cumyl hydroperoxide catalytically to form phenol and aceton. Acyloin phosphites decompose CHP catalytically after a stoichiometric reaction as thiophosphites do. Tetramethylpiperidinyl phosphites (“HALS-phosphites”) react with hydroperoxides only stoichiometrically but with high velocity. Phosphonites react with hydroperoxides in the same way as the corresponding phosphites. Their reactivity, however, is much higher. Hydrogenphosphites are less reactive than phosphites in the reaction with hydroperoxides. They are able to act catalytically.     

Synergistic profiles of chain‐breaking antioxidants with phosphites and hindered amine light stabilizers in styrene–ethylene–butadiene–styrene (SEBS) block copolymer

The photostabilization of poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) (SEBS) by phosphite/p‐hydroxybenzoate antioxidants and hindered phenol/hindered amine light stabilizers (HALS) was studied by using a variety of spectroscopic methods, including FTIR, UV, and luminescence spectroscopy coupled with crosslinking and hydroperoxide analysis. The results were compared with those obtained for hindered phenols and their combinations with phosphite antioxidants. All the stabilizing packages stabilized the SEBS in terms of the inhibition of discoloration and the formation of hydroperoxides, acetophenone, and oxidation products, as well as chain scission and disaggregation of the styrene units. Although phosphite/p‐hydroxybenzoate combinations appeared to reduce the formation of oxidation products, they did not show any remarkable enhancement in long‐term stabilization with respect to phenolic/phosphite antioxidants. On the other hand, strong synergistic profiles were found with the HALS. Mobility and diffusion impediments in the polymeric material appeared to play an important role in the stabilizing activity of the HALS. J. VINYL. ADDIT. TECHNOL. 12:8–13, 2006. © 2006 Society of Plastics Engineers     

Study of some parameters responsible for the efficiency of hindered amine light stabilizers

The photooxidation of a styrene-butadiene-styrene block copolymer previously hydroperoxidized by reaction with singlet oxygen has been studied by measuring the increase of the carbonyl absorbance at 1720 cm^?1. Five different hindered amine light stabilizers (HALS) have been introduced into the polymer by diffusion from methanolic solutions, and their efficiencies as inhibitors of the photooxidation have been compared. The sequence of efficiency observed is: tert. amine > sec. amine > amino ether Under the experimental conditions used HALS are localized preferentially in oxidized regions of the polymer, and their efficiency can be correlated with their ability to catalyze the decomposition of clustered hydroperoxides. As a consequence, HALS are oxidized to nitroxy radicals that are the actual inhibitors of the photooxidation. A high local concentration of HALS in oxidized regions of the polymer also contributes to their efficiency, and this effect justifies the observation that some tertiary amines are more efficient than others.     

Characterization of new hindered amine light stabilizers

New polymerizable urethane functional monomers containing hindered amine (III, III′) and their copolymers with styrene (S) and methyl methacrylate (MMA) are characterized and tested as hindered amine light stabilizers (HALS). Experimental results indicated that the monomers possess high photostabilizing effectiveness comparable to that of Tinuvin 770 and Tinuvin 765. Their copolymers with S and MMA showed lower photostabilizing effectiveness mainly due to the low hindered amine content in the copolymers. The copolymers, however, showed very high resistance to liquid extraction. UV and ESR analyses indicate that the photostabilizing mechanism of these HALS is through the scavenging action of nitroxyl radicals formed from degradation of the substrate polymer. © 1993 John Wiley & Sons, Inc.     

Aspects of stabilization with phosphorous antioxidants in polymers

As plastics are being used in a variety of applications, demands on a greater level of processing stability are increasing. Phosphites are noteworthy as effective processing stabilizer and the performance of phosphite antioxidants can be correlated to the chemical structure of phosphites. Cyclic phosphite esters derived from 2, 2′ methylene bis-2, 4-di-tert-butylphenol and some commercially available phosphites were submitted to comparative studies. Decomposition of cumene hydroperoxide, melt flow of polypropylene and consumption of additives after multiple extrusions were investigated to understand the activity of phosphites as process stabilizers in polypropylene. This study suggests that phosphites play an important role in process stabilization when used in combination with sterically hindered phenols, and that the activity of phosphites may be predicted by their reactivity on hydroperoxide.     

Inhibition of soybean lipoxygenase-1 by chain-breaking antioxidants

The aim of this investigation was to determine whether chain-breaking antioxidants able to prevent lipid peroxidation can inhibit lipoxygenase-1 (EC 1.13.11.12). Therefore, the effects of ascorbic acid, 6-palmitoylascorbic acid and trolox on the enzyme activity were analyzed by means of Lineweaver-Burk double reciprocal plots and Yoshino's graphical method. The effect of these compounds on the formation of free radicals during lipoxygenase-1 reaction was investigated as well, by monitoring the enzymic formation of oxodienes. We present evidence that the chain-breaking antioxidants ascorbic acid, 6-palmitoylascorbic acid and trolox inhibit soybean lipoxygenase-1 in the micromolar concentration range (Ki 27, 3 and 18 μM, respectively). The inhibition is competitive, complete and reversible. All three compounds trap the free radicals formed during the lipoxygenase-catalyzed reaction, which might substantially contribute to their inhibitory ability. These findings can have physiological significance in the light of the lipoxygenase involvement in biomembrane remodelling.     

Chemiluminescence study of thermal and photostability of polyethylene

The oxidation stability of low density polyethylene to UV light has been studied in the presence of various types of antioxidants (hindered phenols, HALS and synthetic N-alkylamines). A chemiluminescence procedure has been applied. Kinetic parameters of oxidation are obtained from isothermal measurements at 180 °C. The synergistic effect of antioxidant couples is examined and a stabilisation order is determined. © 1999 Society of Chemical Industry     

Effects of polymerization catalyst technology on the melt processing stability of polyethylenes. part 2. single stabilizer performance

The effects of a range of thermal and light stabilizers on the melt stability (investigated via multiple pass extrusion) and color stability of three different polyethylenes (PEs) were examined. The PEs varied in terms of the catalyst system used to synthesize the polymers and included an HDPE produced by using a chromium‐based Phillips catalyst and two LLDPEs produced via chromium‐based metallocene and titanium‐based Ziegler‐Natta catalysts. The additive types included a range of phenolics of different functionality, phosphites, hindered piperidines, an hydroxylamine, and Vitamin E. The results obtained for the three PEs confirmed that primary antioxidants (AOs) such as highly hindered and less, hindered phenols or hydroxylamines promoted good melt stability but in some cases tended toward yellowing. The secondary AOs such as the phosphites or thioethers behaved in the opposite way; color suppression was good, but melt stabilization was poor. It was also shown that for different types of phenols (all with similar molar activity), reducing steric hindrance to the phenolic OH enhanced the tendency to form chromophoric groups and hence color led to better efficiency than high hindrance. Those phenol with higher molar activity (mol OH/kg AO) showed the best processing performance. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Wirksamkeit sterisch gehinderter amine bei anspruchsvollen applikationen von polypropylen

The influence of some types of antioxidants on the efficiency of low molecular hindered amine light stabilizers (HALS) has been investigated in a comparison with the behaving of high molecular HALS. Most of the antioxidants used exhibit favourable influence. Convenience of both low and high molecular HALS in compounds depends on the character of the stabilised product and the technological conditions for its production.     

Influence of the chemical structure of para-bridged group on the antioxidant behavior of hindered phenol antioxidants in HDPE resin

A hindered phenol antioxidant with rigid para-bridged group (antioxidant AP) was synthesized to study the effect of the chemical structure on the antioxidant properties of hindered phenol antioxidants in high density polyethylene (HDPE). Antioxidant behavior of series of hindered phenol antioxidants with different para-bridged groups in HDPE resin was also investigated by the thermal oxidation experiment, the mobility test, and the long-term accelerated thermal aging test. The results showed that the rigidity of para-bridged group and the molecule size have the important influences on the antioxidant performance of hindered phenol antioxidants in the HDPE resin, and the antioxidant abilities of antioxidant AP and Irganox 1,330 with the aryl para-bridged group was superior to Irganox 1,098 and 1.0G dendritic antioxidant with the alkyl para-bridged group at the same testing conditions. Compared with the hindered phenol antioxidants with alkyl para-bridged group, the hindered phenol antioxidants with aryl para-bridged group have better thermal oxygen stability and less mobility in the HDPE resin. Irganox 1,010 with ester groups is prone to hydrolysis to increase the mobility rate in hot water and the migration resistance of hindered phenol antioxidants in n-hexane. Moreover, the high content of phenolic OH group and the aryl para-bridged group are favorable for improving the antioxidant performance of hindered phenol antioxidants.     

Synthesis and antioxidative properties of novel multifunctional stabilizers

New multifunctional stabilizers containing hindered amino, phosphite, and in some cases also free phenolic moieties have been synthesized starting from tris(diethylamino)phosphine. Some of them proved to be efficient stabilizers for model hydrocarbons and for polypropylene during processing, thermo‐, and photooxidation. Various sterically hindered phenols, amines (HAS), and phosphites have been modified by the reaction with isophorone diisocyanate (IPDI) to get new multifunctional stabilizers for polymers. The synthesized products have been investigated regarding their thermal and antioxidative behavior. The novel urethane stabilizers are, depending during the polymer processing to release the antioxidatively active parent phenols.     

Effect of hindered piperidine light stabilizer molecular structure and UV absorber addition on the oxidation of HDPE. Part 2: Mechanistic aspects—molecular modeling and electron spin resonance spectroscopy study

The first in this series of papers explored the effect of the structural characteristics of 2,2,6,6‐tetramethylpiperidine‐based hindered amine light stabilizers (HALS) on the thermal and photostabilization of high‐density polyethylene. In the second part, the energies (stabilities) of the nitroxyl radicals and various intermediate species have been predicted using AccuModel® and related to stabilization performance and electron spin resonance (ESR) spectral data. Nitroxyl radicals with low predicted stability generally afforded improved thermal and photostabilization. ESR spectra were used to obtain values of nitroxyl radical concentration ([>N? O·]) and g‐factor as a function of pre‐aging time for combinations of pre‐aged HDPE and >N? H HALS. Demethylation reactions of > N‐methyl HALS resulted in uselessly weak ESR spectra. The HALS that afforded poor thermal oxidative stabilization gave rise to pronounced minima in [>N? O·] that coincided with a maximum in hydroperoxide concentration. The g‐factor values indicated that a predominant nitroxyl canonical form generally promoted superior thermal oxidative stabilization, whereas a predominance of the dipolar N·⁺?O^? form promoted superior photo‐oxidative stabilization. These trends may be related to greater radical‐scavenging and peroxide‐trapping effects, respectively. Molecular modeling and ESR spectra can therefore provide valuable insight into the effectiveness of HALS and stabilization mechanisms. J. Vinyl Addit. Technol. 10:159–167, 2004. © 2004 Society of Plastics Engineers.     

各类稳定剂对聚乙烯薄膜光氧老化的稳定作用

研究了不同光稳定剂和抗氧剂及其配合使用、光稳定剂含量对聚乙烯薄膜耐光氧老化性的影响。结果表明：在各类光稳定剂中、受阻胺类稳定剂的效果最好;紫外线吸收剂与受阻胺配合使用可使膜的耐老化性有所提高;各类抗氧剂对聚乙烯膜的耐光氧老化性没有不利影响;光稳定剂含量增加,薄膜耐老化寿命提高。     

Contribution to the study of mechanism of stabilizing action of esters of phosphorous acid

The rate of the reaction of a series of phosphites with cyclohexene hydroperoxide and cyclohexene peroxy radicals was studied. The results of the measurements were compared with the stabilization efficiency of the same compounds in isotactic and in atactic polypropylene at 160°C and 120°C respectively and during the course of atmospheric ageing. It was found the reverse relation between the stabilization efficiency and the reaction constants of the reaction of phosphites with hydroperoxides. The main stabilization reaction of the phosphorous stabilizers seems to be the reaction of phosphites or of their decomposition products with radicals. The possibility of splitting off of free phenol from phosphites as a result of the reaction of the esters with hydroperoxide groups was checked.     

Active species in hydroperoxide decomposition by hindered amine light stabilizers and its reactivity with phenol

Hydroperoxide decomposition by hindered amine light stabilizers (HALSs) is an important process producing active HALS derivatives and has been studied energetically. The decisive active species of the decomposition, however, has not been proposed yet. In this article, HALS nitrosonium that forms in the decomposition of a hydroperoxide by HALSs and a ring‐opening product of the nitrosonium, a nitroso compound, are proposed as active species for hydroperoxide decomposition. Furthermore, the reactivity of the nitrosonium with phenols is discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1310–1317, 2006     

Study of the thermal-oxidative stability of polybenzoheterocyclic binder

The results of investigating highly thermostable polymer matrices with softening temperatures of 400–450°C are reported. Binders based on a tetranitrile of an aromatic tetracarboxylic acid and bis(o-cyanoamine) are used as polymer matrices. Traditional antioxidants, such as aromatic amines, phenols, and alkyl aryl phosphites, cannot be applied as thermostabilizers. Detailed tests of an efficient stabilizer carborane-containing dinitrile were also unsuccessful because the initial period of retardation in the thermal-oxidative degradation is followed by irreversible changes in the polymer at 350–400°C. Only a new thermostabilizing system based on carborane-containing aromatic compounds with a set of conjugated bonds demonstrates a positive effect. It is established that the developed thermostabilizing system retards the thermal-oxidative degradation and makes it possible to obtain the polymer matrix with a thermal stability of 350–400°C.     

Model studies on the mechanism of hals stabilization

Hindered Amine Light Stabilizers (HALS) are know to inhibit the photo-oxidation of polymers. A key reaction in their stabilization mechanism is believed to be the conversion of a hindered aminoether into a nitroxyl radical. Several different possible mechanisms for this conversion were explored. One, the elimination of the aminoether to form an olefin and hydroxylamine (an intermediate in the formation of a nitroxyl), while possible at high temperatures, cannot account for the inhibitory activity we observed for secondary and primary aminoethers. Direct radical displacement by peroxy radicals was also considered. However, the products predicted by this reaction pathway were not observed. Finally, oxidation of the nitrogen by a peroxy radical, by either electron transfer or a radical attack on the nitrogen, was investigated. While electron transfer was shown to be unlikely, direct oxidation of the aminoether nitrogen was supported by our results. A detailed mechanism for the reaction of both alkyl- and acyl-peroxy radicals with aminoethers is proposed.     

耐药型受阻胺光稳定剂的发展

介绍了耐药型受阻胺光稳定剂（HALS）的发展。针对低pKa值HALS,含缚酸剂的HALS,以及N-烷基化和N-烷氧基化HALS,详细叙述了典型品种的性能特点,并报道了耐药型受阻胺光稳定剂的最新研究成果。