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     

High‐performance phosphite stabilizer

The initial rates of air oxidation of eight aromatic phosphites were measured at 200°C in hydrocarbon solvents. The phosphites were oxidized to the corresponding phosphates, and, in every case, a small amount of the corresponding substituted phenol was also detected. The phenolic compounds likely arose from hydrolysis of the phosphites by water generated during oxidation. In general, alkyl substitution caused a decrease in the rate of oxidation. Phosphite 7 [bis(2,4‐dicumylphenyl) pentaerythritol diphosphite] and, to a lesser extent, phosphite 6 [bis(2,6‐di‐t‐butyl‐4‐methylphenyl) pentaerythritol diphosphite] had a combination of high rate of oxidation and good resistance towards hydrolysis in the bulk state, a combination that is not usual with most commercially available phosphites (1).     

Organophosphorus antioxidants action mechanisms and new trends

Phosphite and phosphonite esters can act as antioxidants by three basic mechanisms depending on their structure, the nature of the substrate to be stabilized and the reaction conditions. All phosph(on)ites are hydroperoxide-decomposing secondary antioxidants. Their efficiency in hydroperoxide reduction decreases in the order phosphonites > alkylphosphites > arylphosphites > hindered arylphosphites. Five-membered cyclic phosphites are capable of decomposing hydroperoxides catalytically due to the formation of acidic hydrogen phosphates by hydrolysis and peroxidolysis in the course of reaction. Hindered aryl phosphites can act as chain-breaking primary antioxidants being substituted by alkoxyl radicals and releasing hindered aryloxyl radicals which terminate the radical chain oxidation. At ambient temperatures, the chain-breaking antioxidant activity of aryl phosphites is lower than that of hindered phenols, because the rate of their reaction with peroxyl radicals and their stoichiometric inhibition factors are lower than those of phenols. In oxidizing media at medium temperatures, however, hydrolysis of aryl phosph(on)ites takes place giving hydrogen phosph(on)ites and phenols which are effective chain-breaking antioxidants. 2,2,6,6-Tetramethyl- and 1,2,2,6,6-Pentamethylpiperidinyl phosphites and phosphonites (HALS-phosph(on)ites) surpass many common phosphites, phenols and HALS compounds as stabilizers in the thermo- and photo-oxidation of polymers. Their superior efficiency is probably due to an intramolecular synergistic action of the HALS and the phosph(on)ite moieties of their molecules.     

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     

Performance and antioxidant activity of phenol/phosphite antioxidants in synergistic blends in the thermal and photooxidation of high‐density polyethylene (HDPE) film: Influence of zinc stearate

The influence of zinc stearate (ZnSt) on the thermal and photochemical stabilities of phenolic antioxidant/phosphite combinations has been determined in HDPE by using FTIR analysis. The results show that while under thermal aging the effects are generally antagonistic, under photooxidation the effects are synergistic. The interactions appear to be dominated by the role of complex formation between the phosphites and ZnSt. Such interactions would remove the hydroperoxide effectiveness of the phosphite in thermal oxidation, while under light they could cause stabilization. Derivative UV and FTIR analysis on pre‐melt blends of the additives in solution shows evidence for strong complexation for the phosphite antioxidants. Other acid scavengers such as hydrotalcite and calcium stearate also appear to influence the behavior of phenolic antioxidants in thermal oxidation. The antagonistic effect of zinc stearate was also confirmed following a single pass in an extruder, where for all formulations there was a greater reduction in MFI associated with crosslinking.     

Electronegativity Governs Enantioselectivity: Alkyl‐Aryl Cross‐Coupling with Fenchol‐Based Palladium‐Phosphorus Halide Catalysts

A series of bulky, modular, monodentate, fenchol‐based phosphites has been employed in an intramolecular palladium‐catalyzed alkyl‐aryl cross‐coupling reaction. This enantioselective α‐arylation of N‐(2‐bromophenyl)‐N‐methyl‐2‐phenylpropanamide is accomplished with [Pd(C₃H₅)(BIFOP‐X)(Cl)] as precatalysts, which are based on biphenyl‐2,2′‐bisfenchol phosphites (BIFOP‐X, X=F, Cl, Br, etc.). The phosphorus fluoride BIFOP‐F gives the highest enantioselectivity and good yields (64% ee, 88%). Lower selectivities and yields are found for BIFOP halides with heavier halogens (Cl: 74%, 47% ee, Br: 63%, 20% ee). NMR studies on catalyst complexes reveal two equilibrating diastereomeric complexes in equal proportions. In all cases, the phosphorus‐halogen moiety remains intact, pointing to its remarkable stability, even in the presence of nucleophiles. The increasing enantioselectivity of the catalysts with the phosphorus halide ligands correlates with the rising electronegativity of the halide (bromine<chlorine<fluorine), as can be rationalized from structural parameters and DFT computations.     

Additive interactions in the stabilization of film grade high-density polyethylene. Part I: Stabilization and influence of zinc stearate during melt processing

The melt stabilization activity of some of the most commercially significant phenolic antioxidants and phosphites (alone and in combination), without and with zinc stearate, was studied in high-density polyethylene (HDPE) produced by Phillips catalyst technology. Multiple pass extrusion experiments were used to degrade the polymer melt progressively. The effect of stabilizers was assessed via melt flow rate (MFR) and yellowness index (YI) measurements conducted as a function of the number of passes. The level of the phenolic antioxidant remaining after each extrusion was determined by high-performance liquid chromatography (HPLC). Phenolic antioxidants and phosphites both improved the melt stability of the polymer in terms of elt viscosity retention; the influence of zinc stearate was found to be almost insignificant. However, phosphites and zinc stearate decreased the discoloration caused by the phenolic antioxidants. A correlation was found between the melt stabilization performance of phosphites and their hydroperoxide decomposition efficiency determind via a model hydroperoxide compound. Steric and electronic effects associated with the phosphorus atom influenced the reactivity towards hydroperoxides. Furthermore, high hydrolytic stability did not automatically result in lower efficiency. Besides phosphite molecular structure, stabilization activity was also influenced by the structure of the primary phenolic antioxidant and the presence of zinc stearate.     

Design of Ionic Phosphites for Catalytic Hydrocyanation Reaction of 3‐Pentenenitrile in Ionic Liquids†

The synthesis and characterization of a novel class of ionic phosphites bearing either a single cationic group obtained by quaternization of aminophosphites or three cationic groups prepared by reaction of phosphorus trichloride with imidazolium phenols are reported. The catalytic hydrocyanation reaction of 3‐pentenenitrile (3PN) into adiponitrile has been performed in the presence of Ni(0) with ionic phosphite ligands, and a Lewis acid in biphasic ionic liquid/organic solvent system. The screening of several original cationic phosphites was performed and the experimental conditions were optimized for the tri‐cationic phosphite tris‐4‐[(2,3‐dimethylimidazol‐1‐yl)methyl]phenyl phosphite tris[bis(trifluoromethylsulfonyl)amide]. It is possible to obtain performance similar to molecular systems and the catalyst and the Lewis acid were immobilized in the ionic phase.     

Hydrolytic degradation and crystallization behavior of linear 2‐armed and star‐shaped 4‐armed poly(l‐lactide)s: Effects of branching architecture and crystallinity

“Linear” aliphatic polyesters composed of two poly(l ‐lactide) arms attached to 1,3‐propanediol and “star‐shaped” ones composed of four poly(l ‐lactide) arms attached to pentaerythritol (2‐L and 4‐L polymers, respectively) with number‐average molecular weight (M_n) = 1.4–8.4 × 10⁴g/mol were hydrolytically degraded at 37°C and pH = 7.4. The effects of the branching architecture and crystallinity on the hydrolytic degradation and crystalline morphology change were investigated. The degradation mechanism of initially amorphous and crystallized 2‐L polymers changed from bulk degradation to surface degradation with decreasing initial M_n; in contrast, initially crystallized higher molecular weight 4‐L polymer degraded via bulk degradation, while the degradation mechanism of other 4‐L polymers could not be determined. The hydrolytic‐degradation rates monitored by molecular‐weight decreases decreased significantly with increasing branch architecture and/or higher number of hydroxyl groups per unit mass. The hydrolytic degradation rate determined from the molecular weight decrease was higher for initially crystallized samples than for initially amorphous samples; however, that of 2‐L polymers monitored by weight loss was larger for initially amorphous samples than for initially crystallized samples. Initially amorphous 2‐L polymers with an M_n below 3.5 × 10⁴g/mol crystallized during hydrolytic degradation. In contrast, the branching architecture disturbed crystallization of initially amorphous 4‐L polymers during hydrolytic degradation. All initially crystallized 2‐L and 4‐L polymers had δ‐form crystallites before hydrolytic degradation, which did not change during hydrolytic degradation. During hydrolytic degradation, the glass transition temperatures of initially amorphous and crystallized 2‐L and 4‐L polymers and the cold crystallization temperatures of initially amorphous 2‐L and 4‐L polymers showed similar changes to those reported for 1‐armed poly(l ‐lactide). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41983.     

The preparation and performance of “Cage” diphosphites as secondary antioxidants in the stabilization of polyolefins

“Cage” diphosphites, a new family of phosphorus antioxidants, are discussed in regard to their preparation, properties, and effectiveness in polyolefins, particularly, with phenolic stabilizers, in respect to their ability to control melt flow and color during processing. These trivalent phosphorus compounds have two different types of phosphite functionalities in their structure. One phosphorus is part of an eight membered (1,3,2-dioxaphosphocine) ring system while the other is part of a tricyclic cage of carbon and oxygen atoms. This structures can contribute to improved hydrolytic stability over rather similar aryloxy-alkoxy phosphites and show competitive stabilization effectiveness in the processing of polyolefins. The possible modes of formation and of hydrolysis are discussed.     

Improvement of melt stability and degradation efficiency of poly (lactic acid) by using phosphite

Concurrent improvement of melt processing stability and degradation efficiency of poly(lactic acid) (PLA) is still a challenge for the industry. This article presents the use of phosphites: tris(nonylphenyl) phosphite (TNPP) and tris (2,4-di-tert-butylphenyl) phosphite (TDBP), to control the thermal stabilization, mechanical performance, and hydrolytic degradation ability of the compressed PLA films. The hydrolysis process is followed as a function of time at 45, 60, and 75°C. During melt extrusion, both phosphites function as a processing aid, besides acting as a chain extender stabilizing the PLA molecular weight. The phosphite structure plays a crucial role over crystallinity and water absorption, in controlling the hydrolytic degradation of PLA. The application of TNPP significantly catalyzes the hydrolysis of PLA, which is the initial step of the biodegradation process. The optimum amount of TNPP for best hydrolytic degradation efficiency and thermal stabilization of PLA is 0.5 wt%. The excessive TNPP loadings cause a drastic drop in PLA molecular weight and, as a consequence, a reduction of flexural strength. The reactions between PLA and phosphite molecules are discussed.     

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.     

Photostabilization of styrene–ethylene–butylene–styrene block copolymer by hindered phenol and phosphite antioxidants

The photostabilization of poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) (SEBS), by hindered phenols and their combination with phosphite antioxidants has been studied by using a variety of spectroscopic methods including FTIR, UV, and luminescence spectroscopy coupled with crosslinking and hydroperoxide analysis. The addition of a hindered phenol was found to photostabilize 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. Strong synergism was found with combinations of a hindered phenol and phosphite antioxidant, especially with an increase in the phosphite concentration. Residual titanium traces present as impurities in the material were found to play an important role in the photo‐oxidation of SEBS. Molecular weight appeared to be a determining factor in the proportion of chain scission/crosslinking reactions that occured. Nevertheless, the addition of antioxidants and the reduction of titanium content also proved satisfactory in stabilizing the low‐molecular‐weight material. J. VINYL. ADDIT. TECHNOL. 12:2–7, 2006. © 2006 Society of Plastics Engineers     

Novel organosoluble poly(amide‐imide‐imide)s synthesized from new tetraimide‐dicarboxylic acid by condensation with 4,4′‐oxydiphthalic anhydride, 1,4‐bis(4‐amino‐2‐trifluoromethylphenoxy)benzene,trimellitic anhydride,and various aromatic diamines

A new monomer of tetraimide‐dicarboxylic acid (IV) was synthesized by starting from ring‐opening addition of 4,4′‐oxydiphthalic anhydride, trimellitic anhydride, and 1,4‐bis(4‐amino‐2‐trifluoromethylphenoxy)benzene at a 1:2:2 molar ratio in N‐methyl‐2‐pyrrolidone (NMP). From this new monomer, a series of novel organosoluble poly(amide‐imide‐imide)s with inherent viscosities of 0.7–0.96 dL/g were prepared by triphenyl phosphite activated polycondensation from the tetraimide‐diacid with various aromatic diamines. All synthesized polymers were readily soluble in a variety of organic solvents such as NMP and N,N‐dimethylacetamide, and most of them were soluble even in less polar m‐cresol and pyridine. These polymers afforded tough, transparent, and flexible films with tensile strengths ranging from 99 to 125 MPa, elongations at break from 12 to 19%, and initial moduli from 1.6 to 2.4 GPa. The thermal properties and stability were also good with glass‐transition temperatures of 236–276°C and thermogravimetric analysis 10 wt % loss temperatures of 504–559°C in nitrogen and 499–544°C in air. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2854–2864, 2006     

Processing and hydrolytic degradation of aromatic,ortho‐substituted polyanhydrides

Polyanhydrides containing 1,3‐bis(p‐carboxyphenoxy)propane, abbreviated poly(p‐CPP), are currently being used as controlled‐release devices for the treatment of brain cancer. These polymers are biodegradable and biocompatible and release pharmaceuticals in a controlled fashion. However, polyanhydrides have an important drawback: The polymers themselves are highly insoluble in both organic solvents and water and have high melting temperatures, rendering them difficult to process into fibers and/or films. Previously, we synthesized polymers that overcame the solubility and, thus, processing problems associated with poly(p‐CPP). In this report, we describe the mechanical properties and hydrolytic degradation characteristics of these newly developed polyanhydrides. After formation of films by either compression‐molding or solvent‐casting, the polymer surfaces were examined by SEM. Mechanical studies were also performed on the compression‐molded samples. Compression‐molded samples were sterilized by γ‐irradiation and then examined by GPC for changes in their polymer structure. Lastly, the polymers and the degradation media were evaluated by TGA, DSC, GPC, and HPLC to gain a better understanding of the degradation process. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 32–38, 2001     

Synthesis and characterization of poly(arylene ether s‐triazine)s containing alkyl‐, aryl‐ and chloro‐substituted phthalazinone moieties in the main chain

Soluble and heat‐resistant polymers have great potential for use as processable, high‐temperature polymeric materials. In this study, four types of new poly(arylene ether s‐triazine)s containing alkyl‐, aryl‐ and chloro‐substituted phthalazinone moieties in the main chain were prepared through direct solution polycondensation of 2,4‐bis(4‐fluorophenyl)‐6‐phenyl‐s‐triazine with each of methyl‐, phenyl‐ and chloro‐substituted phthalazinones. A key feature of these polymers is the incorporation of phthalazinone and side groups into the poly(arylene ether s‐triazine) backbone to endow them with good solubility while maintaining other attractive properties. The polymers were obtained in high yields, and had inherent viscosities ranging from 0.38 to 0.55 dL g^?1. Their structure was characterized using Fourier transform infrared and NMR spectra and elemental analysis. The polymers were almost amorphous, and soluble in N‐methyl‐2‐pyrrolidone, pyridine, N,N‐dimethylacetamide, hot N,N‐dimethylformamide and sulfolane. Tough and nearly transparent films obtained by direct solution casting exhibited good mechanical properties. The resulting polymers displayed glass transition temperatures ranging from 255 to 265 °C and thermal decomposition temperatures for 10% mass loss ranging from 476 to 599 °C, according to differential scanning calorimetry and thermogravimetric analysis, respectively. The reactivity of substituted phthalazinones in nucleophilic displacement reactions and the effect of the side groups on the physical properties of the polymers were also investigated. The results obtained revealed that such s‐triazine‐containing polymers possessed good solubility while maintaining acceptable thermal stability and high mechanical strength with the incorporation of alkyl‐, aryl‐ and chloro‐substituted phthalazinone moieties into their backbones, which makes them an attractive series of high‐performance structural materials. Copyright © 2010 Society of Chemical Industry     

Synthesis and characterization of polyamides and poly(amide‐imide)s derived from 2,6‐bis(3‐aminophenoxy)benzonitrile or 2,6‐bis(4‐aminophenoxy)benzonitrile

A series of polyamides and poly(amide‐imide)s was prepared by direct polycondensation of ether and nitrile group containing aromatic diamines with aromatic dicarboxylic acids and bis(carboxyphthalimide)s respectively in N‐methyl 2‐pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. New diamines, such as 2,6‐bis(4‐aminophenoxy)benzonitrile and 2,6‐bis(3‐aminophenoxy)benzonitrile, were prepared from 2,6‐dichlorobenzonitrile with 4‐aminophenol and 3‐aminophenol, respectively, in NMP using potassium carbonate. Bis(carboxyphthalimide)s were prepared from the reaction of trimellitic anhydride with various aromatic diamines in N,N′‐dimethyl formamide. The inherent viscosities of the resulting polymers were in the range of 0.27 to 0.93 dl g^?1 in NMP and the glass transition temperatures were between 175 and 298 °C. All polymers were soluble in dipolar aprotic solvents such as dimethylsulfoxide, dimethylacetamide and NMP. All polymers were stable up to 350 °C with a char yield of above 40 % at 900 °C in nitrogen atmosphere. All polymers were found to be amorphous except the polyamide derived from isophthalic acid and the poly(amide‐imide)s derived from diaminodiphenylether and diaminobenzophenone based bis(carboxyphthalimide)s. Copyright © 2004 Society of Chemical Industry     

Benefits of a high‐performance phosphite in the gamma irradiation of polyolefins

The highly active process stabilizer bis(2,4‐dicumylphenyl)pentaerythritol diphosphite (P1) was compared in a series of polyolefin formulations with tris(2,4‐di‐t‐butylphenyl) phosphite (P2). Because of its high activity, there was less polymer degradation during processing with P1 as compared to P2. As a result, improvements in color and other physical properties were observed for the polymers, not only during processing, but also after treatment with gamma radiation.     

Synthesis and characterization of new rigid‐rod and organosoluble poly(amide–imide)s based on 1,4‐bis(trimellitimido)‐2,3,5,6‐tetramethylbenzene

A series of new aromatic poly(amide–imide)s (PAIs) was synthesized by triphenyl phosphite‐activated polycondensation of the diimide–diacid, 1,4‐bis(trimellitimido)‐2,3,5,6‐tetramethylbenzene (I), with various aromatic diamines in a medium consisting of N‐methyl‐2‐pyrrolidone (NMP), pyridine, and calcium chloride. The PAIs had inherent viscosities of 0.82–2.43 dL/g. The diimide–diacid monomer (I) was prepared from 2,3,5,6‐tetramethyl‐p‐phenylenediamine with trimellitic anhydride (TMA). Most of the resulting polymers showed an amorphous nature and were readily soluble in a variety of organic solvents including NMP, N,N‐dimethylacetamide (DMAc), and N,N‐dimethylformamide (DMF). Transparent, flexible, and tough films of these polymers could be cast from DMAc solutions. Their cast films had tensile strengths ranging from 80 to 95 MPa, elongation at break from 10 to 45%, and initial modulus from 2.01 to 2.50 GPa. The 10% weight loss temperatures of these polymers were above 510°C in nitrogen. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1162–1170, 2000     

Synthesis and characterization of new poly(amide‐imide)s based on 1,4‐bis(trimellitimido)‐2,5‐dichlorobenzene

A series of new aromatic poly(amide‐imide)s were synthesized by the triphenyl phosphite‐activated polycondensation of the diimide‐diacid, 1,4‐bis(trimellitimido)‐2,5‐dichlorobenzene (I), with various aromatic diamines in a medium consisting of N‐methyl‐2‐pyrrolidone (NMP), pyridine, and calcium chloride. The poly(amide‐imide)s had inherent viscosities of 0.88–1.27 dL g⁻¹. The diimide‐diacid monomer (I) was prepared from 2,5‐dichloro‐p‐phenylenediamine with trimellitic anhydride. All the resulting polymers were amorphous and were readily soluble in a variety of organic solvents, including NMP and N,N‐dimethylacetamide. Transparent, flexible, and tough films of these polymers could be cast from N,N‐dimethylacetamide or NMP solutions. Cast films had tensile strengths ranging from 92 to 127 MPa, elongations at break from 4 to 24%, and initial moduli from 2.59 to 3.65 GPa. The glass transition temperatures of these polymers were in the range of 256°–317°C, and the 10% weight loss temperatures were above 430°C in nitrogen. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 271–278, 1999