LEAD PHTHALATE

Economics. The lead-based stabilizers tend to be priced relatively low, with 1992 prices ranging from 1.40 to 3.60/kg in the United States. The lead phthalates tend toward the higher end of this range, whereas the pipe one-pack products fall into the low end. 

Dibasic Lead Phthalate. Dibasic lead phthalate [17976-43-17, 2PbO Pb(02C)2CgH Xphacjl 2 H2O, is a white, crystalline powder, mol... 

For viayl compouads, the geaeral range of dibasic lead phthalate stabiHzet usage is betweea 4 and 4 phr resia. In 105°C electrical iasulation PVC stocks, approximately 7 phr is required. For vinyl plastics and foams, between 3 and 5 phr of lead stabiHzet is recommended. 

AppHcatioas of dibasic lead phthalate, coated grade, iaclude 90 and 105°C rated PVC electrical iasulation, plastisols, profile extmsions, calendered sheet, and molded products. The recommended range of usage ia viayl electrical iasulatioa is 5—7 parts pet huadred resia, depending oa the particular iasulatioa classiftcatioa to be met. Ia geaeral-purpose extmded and molded PVC stocks, approximately 3—6 phr of coated dibasic lead phthalate is suggested. 

Material used in GEON 103EP, MN = 195,000, MN = 64,000. Plasticizer is diisodecylphthalate. Samples also contain 5% lead phthalate stabilizer. 

Lead stabilisers have been used in a variety of PVC as well as other polymers for many years. In some halogenated polymers, such as chlorinated PE (CPE), chlorosulphonated polyethylene (CSM), polychloroprene (CR) and epichlorohydrin (ECO), dibasic lead phthalate and dibasic lead phosphite are used to scavenge HC1 arising from crosslinking as well as from degradation. In some of these cases, the metal may participate in crosslink formation. With lead-based stabilisers, the result is typically a product with greater water and chemical resistance than if a light metal, with more soluble halide salts, were used instead. In other cases, lead stabilisers may be used solely for function in metal oxide... 

IR and NMR spectra of basic lead carboxylates used as heat stabilisers for halogenated polymers, e.g. PVC, indicated that these salts were not complexes, or double compounds of lead oxide, as suggested in most textbooks, but unique compounds of interesting structure. Stabilisers studied included monobasic lead phthalate, tribasic lead maleate, tetrabasic lead fumarate, dibasic lead phthalate and dibasic lead stearate. Lead stabilisers probably functioned in these polymers by converting hydrogen chloride to water, interfering with acid catalysis of the elimination reaction. 6 refs. 

The variety of substances used as additives in polymers is considerable. For example, the fillers may include china clay, various forms of calcium carbonate, talc, silicas (diatomaceous silica), silicates, carbon black, etc. The impact modifiers typically include other polymers. Plasticizers include certain polymers with low (oligomers), dialkyl phthalates, dialkyl sebacates, chlorinated paraffin waxes, liquid paraffinic fractions, oil extracts, etc. Heat stabilizers include heavy metals salts such as basic lead carbonate, basic lead sulfate, dibasic lead phosphite (also acting as a light stabilizer), dibasic lead phthalate, stearates, ricinoleates, palmitates and octanoates of cadmium and barium, epoxide resins and oils, amines, diphenylurea, 2-phenylindole, aminocrotonates. The antioxidants include tris-nonyl phenyl phosphite, 2,6-di-ferf-butyl-p-cresol (BHT), octadecyl-3,5-di-terf-butyl-4-hydroxyhydrocinnamate, etc. The UV stabilizers include modified benzophenones and benzotriazoles. Processing lubricants include calcium stearate, stearic acid, lead stearate, various wax derivatives, glyceryl esters and long-chain acids. Fire retardants include antimony oxide, some pyrophosphates, etc. 

Lead Compounds—These were among the earliest stabilizers. Although quite effective as heat stabilizers, they are toxic, impart opacity to PVC compounds, and cause black coloration with time because of poor sulfide stain resistance. The primary use for lead compounds is in electric applications such as wire coatings. The principal lead compounds for this use are tribasic lead sulfate, basic lead sulfate silicate, basic lead carbonate, and basic lead phthalate. Use levels usually range from 3 to 8 parts-per-hundred parts of PVC (phr). 

Enviro-Stab 1155. [Monson Chem.] Dibasic lead phthalate, encapsulated. 

Two other sets of samples have been taken from a recipe for cable insulation and for an ignifugated protective envelope of an electric cable. The recipe for cable insulation includes (in phr) PVC (Kwert 70), 100 ditridecyl phthalate, 34 octyldecyl trimellitate, 17 calcium carbonate covered with stearic acid, 14 calcinated kaolin, 6 dibasic lead phthalate, 8 bisphenol A, 0.05. 

X-Ray Diffraction. This tecnnique has been used for lead formulation where lead phthalate and calcium carbonate show major x-ray peaks. Because of the morphology of the lead phthalate (platelets), oriented... 

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