Lead phosphite

Dibasic Lead Sulfate. Dibasic lead sulfate [12036-76-9] 2PbOPbSO, is a white powder, mol wt 749.70, mp 961°C. The dibasic compound can be prepared by fusion of the two components. It has been sold as a PVC stabilizer in Japan and is sold in Europe in combination with dibasic lead phosphite. 

Dibasic Lead Phosphite. Dibasic lead phosphite [12141 -20-7] 2PbO PbHPO pfrac l 2 H2O, is a white crystalline powder, mol wt... 

Lead Whites. Basic lead carbonate, sulfate, siHcosulfate, and dibasic lead phosphite are commonly referred to as lead whites. Usage is limited because of environmental restrictions placed on the use of lead-containing compounds. 

Azocarbonamide (I) Carbonamide N2, CO, CO2 190-230 220 Most widely used blowing agent in PVC and polyolefins. High decomposition temperature reduced by a variety of metal salts and oxides such as lead carbonate, lead phosphite and zinc oxide. High gas yield. Reaction products show little odour or discoloration. ... 

Vulcanisation can be effected by diamines, polyamines and lead compounds such as lead oxides and basic lead phosphite. The homopolymer vulcanisate is similar to butyl rubber in such characteristics as low air permeability, low resilience, excellent ozone resistance, good heat resistance and good weathering resistance. In addition the polyepichlorohydrins have good flame resistance. The copolymers have more resilience and lower brittle points but air impermeability and oil resistance are not so good. The inclusion of allyl glycidyl ether in the polymerisation recipe produces a sulphur-curable elastomer primarily of interest because of its better resistance to sour gas than conventional epichlorhydrin rubbers. 

Another method for slowing oxidation of rubber adhesives is to add a compound which destroys the hydroperoxides formed in step 3, before they can decompose into radicals and start the degradation of new polymer chains. These materials are called hydroperoxide decomposers, preventive antioxidants or secondary antioxidants. Phosphites (phosphite esters, organophosphite chelators, dibasic lead phosphite) and sulphides (i.e. thiopropionate esters, metal dithiolates) are typical secondary antioxidants. Phosphite esters decompose hydroperoxides to yield phosphates and alcohols. Sulphur compounds, however, decompose hydroperoxides catalytically. 

The main method of crosslinking the homopolymer and copolymer is by use of thioureas, and, as the cure reaction requires basic conditions, an acid acceptor is also added. Litharge, red lead, magnesium oxide and dibasic lead phosphite are commonly used acid acceptors, and the most commonly used thiourea is ethylene thiourea, but this has a tendency to promote mould fouling. 

Zinc oxide/dibasic lead phosphite Least tendency to scorch, intermediate acid resistance. 

VDC polymerization and, 25 696 water-vapor transmission rate, 3 387t PolyCvinyl chloride) cable, 77 848 PolyCvinyl chloride-co-vinyl acetate), 7 524 Poly(vinyl chloride) polymers, lead phosphite in, 14 791... 

Diethyl phosphite was probably first prepared in 1854 by the reaction between alcohol and phosphorus(III) chloride.1 It can also be prepared from phosphorus(III) oxide and alcohol,2 from phosphorous acid and diazoethane,3 or from lead phosphite and ethyl iodide.4... 

Its density, D1, was 0-9605, it boiled at 156° C., was insoluble in water, soluble in many organic solvents, and had a molecular weight of 154 in benzene. It reduced mercuric chloride. The other, prepared by the action of lead phosphite on ethyl iodide, or phosphorous oxide on ethyl alcohol, had a density,, of 1-028, boiled at 198° C. and did not reduce mercuric chloride. This was probably diethylethyl phosphite, having the formula C2H5 -PO = (OC2H5)2. A diethyl ester has also been prepared which boils at 187°-188° C. and may have either formula... 

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). 

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... 

Gabel also investigated the use of corrosion inhibitors. She found that antimony trioxide and dibasic lead phosphite appeared to have a synergistic effect in reducing corrosion with a phenolic-bonded coating. She also found that sodium nitrate, which acts as an oxidising passivator on steel, was effective, but less so than dibasic lead phosphite. 

SYNS C.I. 77620 DIBASIC LEAD METAPHOSPHATE DIBASIC LEAD PHOSPHITE LEAD OXIDE PHOSPHONATE, HEMIHYDRATE LEAD PHOSPHITE, dibasic (DOT)... 

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. 

Applications Phosphorous acid is mainly directly used by the producer for the manufacture of phosphonic acids. For example ca. 41 10 t of H3PO3, corresponding to 48% of the USA consumption of phosphorus(III) chloride, was utilized in the USA in 1994 for the manufacture of N-phosphonomethyl-glycine (glyphosphate), quantitywise the most produced phosphonic acid. Other phosphonic acids produced from phosphorous acid are utilized as water treatment chemicals. Basic lead phosphite is used as a PVC-stabilizer. 

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