Phosphite processing stabilizers

Phosphite processing stabilizers are used in PET to maintain the IV, suppress yellowing and overall to reduce thermo-oxidative degradation. 

Phosphite processing stabilizer for polypropylene, polyethylene, and adhesives. 

Both LEXAN 141 and 143 [1] show a distinctive loss of similar intensity in the range -120 C to -130 C below 3 Hz which is not observed in LEXAN 145 [3]. It is concluded that the low temperature process below 3 Hz is a consequence of the presence of the phosphite processing stabilizer in the former which is absent in LEXAN 145. 

For impact-modified PC/PBT and PC/PET blends evidence has been presented for partial miscibility of the component polymers and for a two-phase blend morphology with a polyester-rich dispersed phase in a continuous matrix rich in polycarbonate. Other absorptions are attributed respectively to MWS interfacial polarization, to the presence of the impact modifier and to a phosphite processing stabilizer. 

Blends of primary anti-oxidants and a high-temperature hydrolytically stable organophosphite secondary anti-oxidant have been developed for high-temperature processing of polyolefins, polyamides, and polycarbonates in colour-critical applications. Irganox LM blends of primary anti-oxidants and a new phosphite processing stabilizer offer melting at 90°C and can be applied to polymer reactor products, especially polyolefins, linear polyesters, polycarbonates, polyamides, HIPS, ABS, SAN, and elastomers. 

These polymers are subjected to high temperatures, ca 300°C, duting extmsion and iajection molding. Processing stabilizers are used to decrease both the change ia viscosity of the polymer melt and the development of color. A phosphite, such as tris(2,4-di-/ f2 -butyiphenyi)phosphite (25) or bis(2,4-di-/ f2 butyiphenyi)pentaerythritol diphosphite [26741-53-7] ia combination with a phenoHc antioxidant such as octadecyl... 

New developments are hydroxylamines and lactones (for processing stability), which operate at an earlier stage during stabilisation. Lactone (benzofuranone) chemistry has been identified as commercially viable, and marks a revolutionary advance in comparison to hindered phenols and phosphites [18]. New lactone chemistry (Figure 10.1) provides enhanced additive compatibility, reduced taste and odour (organoleptics), resistance to irradiation-induced oxidation, and inhibition of gas fade discoloration. The commercial introduction of fundamentally new types of stabilisers for commodity and engineering polymers is not expected in the near future. 

The following six hindered phosphonite and phosphite esters were studied as processing stabilizers and compared with 7. and 8. 

A number of ortho hindered alkyl-substituted phenyl phosphites and phosphonites were found to be effective process stabilizers for polypropylene and high density polyethylene combining more effective stabilization activity at high temperatures with good storage stability at relatively elevated humidity and ambient temperature, as well as resistance to discoloration. 

Here we discuss a new class of polypropylene stabilizers—the polymeric phenolic phosphites. These compounds exhibit unique, broad-spectrum activity which may allow simplification of polypropylene stabilizer systems. The most active species are synergistic with thiodipro-pionate esters, are effective processing stabilizers when used alone or with other compounds, and contribute to photostability. Compounds of this type appear to function as both free radical scavengers and peroxide decomposers, and through a mechanism not yet completely understood, allow significant reductions in the concentration of ultraviolet absorbers required to achieve high levels of photostability. 

Processing Stability. The ability of tris (nonylphenyl) phosphite to prevent degradation of polypropylene during processing is believed related to its efficiency to decompose peroxides into non-active species. In a similar way, the phosphite groups on the polymeric phosphites may also be capable of decomposing peroxides (see top of p. 217). 

Three separate processing stability tests were run, and comparisons were made between (1) tris (nonylphenyl) phosphite and a PPP, (2) two commercial resins, and unstabilized resin containing the synergistic DLTDP-PPP combination, and (3) DLTDP alone, a PPP alone, a combination of the two, and unstabilized resin. 

Figure 1. Processing stability of polypropylene, PPP vs. aryl phosphite...

Where aryl phosphites are good processing stabilizers, they do not contribute much to light stability or heat stability at elevated temperatures. Where hindered phenolics are good heat stabilizers, they do not contribute much to photostability. Some phenolics are effective processing stabilizers, but the phenolics are not as effective as aryl phosphites or the polymeric phenolic phosphite compounds. 

The polymeric phenolic phosphites are excellent heat and processing stabilizers and can contribute significantly to photostability. These broad-spectrum stabilizers offer possibilities for simplifying polypropylene stabilizer systems. They may allow one to use lesser amounts of other additives, and they open up a new area for potential cost savings in formulating polypropylene resins. 

Di(octadecyl)hydroxylamine (18) (Seltzer et al., 1989 PospiSil and Nespurek, 1997) was recently introduced commercially for the stabilization of PO, PP in particular. 18 is a hydrolysis-resistant processing stabilizer used in combination with aromatic phosphites, and a long-term heat stabilizer used in combination with suitable HAS. Di-alkylhydroxylamine is considered as scavenger of radicals POO" and P. The latter are trapped by nitroxide or nitrone, arising from the parent hydroxylamine (Eq. 3-7). 

Secondary liquid phosphite antioxidant that functions as a peroxide decomposer and as a processing stabilizer in a wide variety of polymers, including polyolefins and styrenics. 

In a previous paper, the effectiveness of certain hindered mono phosphites and phosphonites as processing stabilizers for polyolefinsC1) was discussed. 

The present paper describes several new classes of hindered phenyl bis- and tris-phosphites having di-benzo[d,f][1,3,2]dioxaphosphepin and dibenzo[d,g]-[1,3,2]dioxaphosphocin rings. The latter compounds exhibit superior effectiveness as processing stabilizers together with greater resistance to discoloration and hydrolysis. The di- and tri-alkanolamine esters are of particular interest because of their even greater resistance to hydrolysis at 50°C for extended time periods previously achievable only in the case of certain di-hindered phenyl phosphonites. 

The two classes of hindered substituted bis- and tris- phosphites having either (a) dibenzo[d,f][1,3,2]dioxaphosphepin or (b) dibenzo[d,g][1,2,3Jdioxaphosphocin rings were selected for study as processing stabilizers because their bicyclic structures promised stabilizers of increased thermal and hydrolytic stability compared to the acyclic hindered phenylphosphonites previously studied (1). 

Compounds j4 and 5, two of the experimental processing stabilizers listed in Figure 2, remained essentially unchanged when exposed neat to an air atmosphere of 80% relative humidity at room temperature for 50 days. This is in contrast to some of the commercial compounds such as 1 1, and 3 which hydrolyze rapidly under the same conditions (Table V). Hydrolysis tests at 50°C/80% relative humidity show that compounds 4 to 9 inclusive are much more resistant to hydrolysis than 3 (Table VI). Of particular interest in this respect is the dramatic increase in hydrolytic stability of compounds 6 and 9 all of which have tertiary amino functions in their phosphite structures capable of preferentially neutralizing... 

In many stabilizer formulations, different types of stabilizers are used. As processing stabilizer phenolic antioxidants and phosphites are applied, for long-term heat stability phenolic antioxidants and thioethers are used and for UV stability, combinations of HALS with other types of UV stabilizers can be applied. HALS stabilizers show interactions with these types of stabilizers that can lead to synergisms as well as antagonisms. 

The lack of the melt processing activity of HAS means that they do not contribute to the conventional melt processing formulations consisting of hindered phenols and aromatic phosphites. A properly selected combination of processing stabilizers and HAS has, however, a favourable effect on the LTHS and light stability of the polymer during the longterm application [129,135]. 

Vanstay. [R.T. Vand ilt] Organic phosphite chelatm, stabile, synergist, processing aid for PVC fomuila-tkms. 

Typical processing stabilizers for polypropylene and butylated hydroxy-toluene (BHT) as the primary antioxidant and phosphates and phosphonates as secondary antioxidants. Examples of the latter that are commonly used are tetrakis-(2,4-di-terr-butyl-phenyl)-4-4 -bisphenylylenediphosphonite, distearyl-pentaerythrityl-diphosphonite, tris-(nonylphenyl)-phosphite, tris-(2,4-di-teft-butyl-phenyl)-phosphite and bis(2,4-di-ferr-butyl-phenyl)- pentaerythrityl-diphosphite. In commercial polypropylenes, phosphorous compounds are always used together with a sterically hindered phenol. The compounds are commonly added in concentrations between 0.05 and 0.25%. 

Low-density polyethylene (LDPE) is extensively used for the manufacture of films. During processing, which is carried out at temperatures of approximately 200°C, cross-Unking, and thus formation of gel, can occur through oxidation if the polymer is not stabilized. Such gel particles are visible in the film as agglomerates, known as fish eyes or arrow heads. The processing stabilizers used in LDPE consist of systems commonly used for polypropylene, namely, combinations of a phosphite or phosphonite and a long-term heat stabilizer (hindered phenol) in overall concentrations up to 0.1%. Concentrations seldom exceed 0.1%, since the compatibility of any additive in LDPE is considerably lower than in any other polyolefins. 

Melt-processing stabilization of AOs. Unstabilized HOPE shows large changes in melt-flow index with each extrusion pass. However, phenolic/phosphite AO blends without and with a lactone AO component (Ciba Irganox B 215 and HP 2215) reportedly keep the melt flow more consistent after repeated extmsion passes. 

Lactone + phenolic + phosphite 181314-48-7, 6683-19-8, 31570-04-4 Irganox HP 2215 g Effective PP and PE processing stability for demanding applications... 

Lactone + amine + phosphite 181314-48-7, 65447-77-0, 31570-04-4 Fiberstab L 112 p Process stabilization for low-gas-fade PO fiber applications... 

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