Phosphite ester compositions for PVC compounds

Abstract

The activity of various structural classes of liquid organophosphite esters has bee11 examined in flexible PVC applications. Blends of the most active phosphites have been developed as alternative heat stabilizers for PVC. These new phosphite mixtures eliminate the dependence of compounders upon mixed-metal stabilizer systems based on heavy metals such as barium and cadmium. Static oven aging tests showed the superior performance of these blends compared to that of traditional mixed-metal stabilizers. IWI'RODUCTIONhe WC industry began with the invention of plas-T ticized polyvinyl chloride by Waldo Semon of the B. F. Goodrich Company in 1933 (1). In 2001, over 12 billion pounds of flexible WC were employed throughout the world in a wide variety of commercial applications, including vinyl flooring, wall covering, roofing, pond and pool liners, film, upholstery, apparel, hose, tubing and wire insulation (2).In order to succes:sfully process flexiile vinyl compounds into finished vinyl articles by extrusion, calendering or molding, it is necessary to incorporate between one and five percent of a heat stabilizer to prevent dehydrochloilnation and discoloration of the polymer during theimal processing. The preferred vinyl heat stabilizers for most flexible PVC applications in the United States are referred to as "mixed metal" heat stabilize~s. They are complex multi-component chemical admixtures based upon combinations of alkaline earth and heavy metal salts with a variety of antioxidanrs, HCl absorbers and chelating agents. The most widely used mixed metals are based upon and referred to as barium-cadmium, bariumcadmium-zinc, barium-zinc, and calcium-zinc stabilizers (3).Early mixed metal stabilizers were solids based upon barium and cadmium soaps. For optimum performance these were used in combination with liquid phosphite esters such as biphenyl phosphite. Beginning in 1951, liquid mixed metal stabilizers were produced by dissolving the metallic components in liquid phosphite esters (4). Since 1980, phosphite esters have become an increasingly important component of liquid mixed metal stslbilizers. as formulatom have attempted to decrease or eliminate the use of toxic metal components. Today, state-of-the-art, high-efficiency mixed metal stabiliztm can contain over 5Owt?? of phosphite esters.Phosphite esters contribute to vinyl stabilization through a variety of mechanisms. They decompose hydroperoxides. react with HCl. add to double bonds, complex with Lewis acids and replace labile chlorides via Arbmv -Rearrangement (4,5). As the heavy metal components are decseased and phosphite ester components are in-ed in mixed metal stabilizers, seveml ancillary properties of the vinyl compounds improve, including heat stability, light stability, stain resistance, and plate-out resistance. The purpose of this paper is to illustrate the manner in which various phosphite esters can be used to augment or replace heavy metal components of mixed metal vinyl heat stabilizers. E x P E x u l u E m A LMatedab. WC resin (1.02 nr), dio...

Organophosphite transformations in flexible PVC formulations

“…The presence of an aryl group may decrease the hydrolysis of the phosphite in the polymer, thus allowing the phosphite to remain intact at longer processing times and delaying the decomposition of PVC. Blends of high performance/hydrolytically stable phosphites and zinc carboxylates have been used to replace Ba/Zn mixed-metal stabilizers directly in various commercial PVC formulations (2,5,12).…”

Intercalated hydrotalcite‐like materials and their application as thermal stabilizers in poly(vinyl chloride)

“…Although a lot of acid‐radical‐ion‐intercalated hydrotalcites have been studied, those anions were not phosphate ions. Because of the similarity between phosphate ions and phosphite ester, phosphite ester can be used as a kind of additive and a thermal stabilizer in PVC; it can react with unstable Cl atoms to improve the initial color of PVC . So, in this study, traditional corresponding salts were substituted with calcium hydroxide [Ca(OH) 2 ] and aluminum hydroxide [Al(OH) 3 ] to prepare hydrotalcites; this would greatly reduce the production costs.…”

“…Because of the similarity between phosphate ions and phosphite ester, phosphite ester can be used as a kind of additive and a thermal stabilizer in PVC; it can react with unstable Cl atoms to improve the initial color of PVC. 24 So, in this study, traditional corresponding salts were substituted with calcium hydroxide [Ca(OH) 2 ] and aluminum hydroxide [Al(OH) 3 ] to prepare hydrotalcites; this would greatly reduce the production costs. The papered samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and IR techniques with the result that Ca-Al-HPO 3 -LDH was successfully synthesized.…”