Tribasic lead stearate

By far the most common lead salt used for PVC stabilization is tribasic lead sulfate. It can be found either alone or combined with another lead salt in almost every lead-stabilized PVC formulation. Many of the combinations are actually coprecipitated hybrid products, ie, basic lead sulfophthalates. Dibasic lead stearate and lead stearate are generally used as costabilizers combined with other primary lead salts, particularly in rigid PVC formulations where they contribute lubrication properties dibasic lead stearate provides internal lubrication and lead stearate is a good external lubricant. Basic lead carbonate is slowly being replaced by tribasic lead sulfate in most appHcations due the relatively low heat stabiHty of the carbonate salt which releases CO2 at about 180°C during PVC processing. 

Rigid Applications. The use of the lead stabilizers is very limited in the United States but, they are stiU used in several rigid PVC appHcations in Europe and Asia. The highest use of lead stabilizers in rigid PVC is for pipe and conduit appHcations. Tribasic lead sulfate is the primary heat stabilizer with lead stearates included to provide lubrication. The lead products are typically fully formulated, usually including lubricants and pigments for pipe extmsion appHcations. These lead one-packs, when used at about 1.8—2.5 phr, provide all of the stabilizer and lubrication needed to process the polymer. A lead one-pack contains tribasic lead sulfate, dibasic lead stearate calcium stearate, polyethylene wax, paraffin wax, ester wax, and pigments. 

Lead compounds, usually based on a mixture of lead salts, e.g., tribasic lead sulfate or dibasic lead phosphite, and lead soaps, e.g., dibasic or normal lead stearates, have been very cost effective heat stabilisers for many years, and function as HC1 absorbers (236, 365,438). 

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. 

Dried chlorella powder and PVC (n llOO) were used. As the stabilizer some chemical additives were used. These chemicals were dibasic lead stearate (DEL), tribasic lead sulfate (TC),cadmium/barium/lead fatty acids complex (U500), barium/zinc fatty acids complex (PSE) and paraffin. Usually we used the mixture of 20% chlorella and PVC with TC 1.5%, DEL 0.5%, 1 500 0.5% of PVC respectively. 

Tribase EXL Special, Tribase XL. See Lead sulfate, tribasic Tribase. See 1,3,3-Trimethyl-2-methyleneindoline Lead sulfate, tribasic Tribasic aluminum stearate. See Aluminum tri stearate... 

Lead Tribasic lead sulfate Dibasic lead phalate Dibasic lead stearate Wire Cable General Flexible Products... 

The lead compounds used as heat stabilisers include dibasic lead carbonate and phthalate, dibasic and neutral lead stearate, tribasic and tetrabasic lead sulphate, dibasic lead phosphate and phthalate, liquid lead carboxylates and tetrabasic lead fiunarate. Lead stearates are added to other lead compounds because some combinations show a synergistic effect. 

PVC lOOphr Corvic S67/111 (PVC resin) 5phr tribasic lead sulphate (stabilizer) 1 phr calcium stearate (lubricant), f ABS lOOphr Cycolac GSM. t FeOOH Bayferrox 3905, hydrated iron(ni) oxide (Bayer UK Ltd). 

Some stabilizers are effective in improving weathering behaviour. Lead compounds are good heat stabilizers basic lead carbonate or tribasic lead sulphate are favoured stabilizers but are toxic. The stearate, palmitate and octoate salts of Cd, Ba, Ca, Zn are increasingly used, but toxicity limits the range of applications for Cd. Organo-tin compounds are also effective stabilizers, especially for transparent products, but may also be somewhat toxic. 

Lead stabilizers have a strong tendency to adsorb small molecules. On occasion, oxidized products fiom additives used in resin manufacture may react with tribasic lead sulfate or dibasic lead phthalate to the detriment of color hold. This tends to vary with lot to lot and with grade of resin. It can be overcome by use of calcium or barium stearate-coated stabilizer or, in severe cases, by replacing 5—10 percent of sulfate or phthalate with dibasic lead phosphite. 

Lead-stabilized products, used in some parts of the world in rigid extrusions, often contain 0.4-0.8 phr of calcium stearate as internal lubricant, 0.2-0.5 phr of stearyl alcohol to improve the mobility of the stabilizer (normally dibasic lead phosphate or combinations with tribasic lead sulfate), and 0.4-0.75 phr of partly saponified mon-tanic ester as a multifunctional lubricant. For the ultimate in process stability, calcium stearate may be replaced by a barium/cadmium stearate blend. The inclusion of cadmium also reduces the severity of staining by airborne sulfur compounds. Although lead-stabilized rigid compounds offer advantages in material cost and process safety, their use should be abandoned because of the hazard involved and because such usage is prejudicial to acceptance of vinyl products. 

Haro Chem PTS-E. See Lead sulfate, tribasic Haro Chem ZGD, Haro Chem ZGN, Haro Chem ZGN-T, Haro Chem ZPR-2. See Zinc stearate... 

Stale EP101 a. Stale EP1023] Stale EP 1028] Stale EP 1032] Stale EP 1049] Stale EP 1051] Stale EP 1056-1] Stale EP 1095] Stale EP 1120-5] Stale EP 1144] Stale EP 1168] Stale EP 1211] Stale EP 1238-1] Stale EP 1545] Stale EPM101 a. Stale EPM 1011] Stale EPM 1012] Stale EPM Ilia, Stale EPM 1111] Stale EPM 1112] Stale EPM 1211. See Lead sulfate, tribasic Stale L 703. See Stearic acid Stale L 704. See Polyethylene, oxidized Stale L 705. See Paraffin Stale L 707. See Polyethylene, oxidized Stale L 710. See Polyethylene wax Stale L 712. See Paraffin Stale L 716. See Hydroxystearic acid Stale L 732. See Montan wax Stale M 200. See Calcium stearate Stale M 201. See Calcium laurate Stale M 206. See Barium laurate Stale M 240. See Zinc stearate Stale MB 1023] Stale MB 1032] Stale MB 1095] Stale MB 1168] Stale MB 1211] Stale ... 

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