Metal Stearate Stabilisers

Various methods for the determination of stearate stabilisers are listed in Table 11.15. 

TLC thin-layer chromatography Source Author s own files  

Hallam and K.G. Thompson, Determination of Lead and Cadmium in Potable Waters by Atom Trapping Atomic Absorbance Spectroscopy, Divisional Laboratory, Yorkshire Water Authority, Sheffield, UK, 1986. 

Journal of Automated Methods and Management in Chemistry, 1982, 4, 2,61. 

Stockwell in Topics in Automatic Chemical Analysis, Volume 1, Ellis Horwood, Chichester, UK, 1979. 

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Whilst lead compounds have been, and still are, the most important class of stabiliser for PVC the metallic soaps or salts have steadily increased in their importance and they are now widely used. At one time a wide range of metal stearates, ricinoleates, palmitates and octoates were offered as possible stabilisers and the efficiency of many of them has been examined. Today only the compounds of cadmium, barium, calcium and zinc are prominent as PVC stabilisers. 

Crompton [21] has reviewed the use of electrochemical methods in the determination of phenolic and amine antioxidants, organic peroxides, organotin heat stabilisers, metallic stearates and some inorganic anions (such as bromide, iodide and thiocyanate) in the 1950s/1960s (Table 8.75). The electrochemical detector is generally operated in tandem with a universal, nonselective detector, so that a more general sample analysis can be obtained than is possible with the electrochemical detector alone. 

Thermal stabilisers for PVC are often heavy metal stearates (lead, barium), tin thiolates (R2Sn(SR2) = MZ2), and work by reacting the allylic... 

Journal of Applied Polymer Science 68, No.l, 4th April 1998, p.11-27 STABILISATION OF POLY(VINYL CHLORIDE) WITH PREHEATED METAL STEARATES AND COSTABILISERS. II. USE OF A POLYOL Benavides R Edge V Allen N S Tellez M M Mexico,Centro de Investigacion en Quimica Aplic. Manchester,Metropolitan University Coahuila,Universidad Autonoma... 

The influence of a beta-diketone on the already observed anomalous behaviour of preheated metal stearates, e.g. zinc stearate, calcium soap, as heat stabilisers for PVC was evaluated using dibenzoyl methane (Rhodastab-83), a short-term costabiliser. 19 refs. 

Many types of additives are used to stabilise PVC. For example, mixed metal salts of fatty acids, such as barium and cadmium stearates, are added at a 2 or 3% level. Metal stearates (MSti) react with and remove free hydrogen chloride, slowing down the degradation. 

Dover Chemical Corp. is a subsidiary of ICC Industries Inc. headquartered in New York City. Dover s products are extremely diverse the chemicals made include brominated and bromo-chlorinated flame retardants, benzophenone and hindered amine light stabilisers, phosphite stabilisers, surfactants, lubricants, metallic stearates, and alkyl phenols. It is also a leading manufacturer of chlorinated hydrocarbon waxes, and there are several chemical products unrelated to plastics. 

Heat stabiliser Organotin mercaptides/sulfides/carboxylates antimony mercaptides metal carboxylates lead stearate/phosphite/phthalate/sulfate S, Sb, Sn, Ba, Ca, Cd, Mg, Sr, Zn P, Pb, S... 

An investigation was carried out to determine the synergetic effect of dimerised pentaerythritol esters, used as novel costabilisers with metal soap, a mixture of zinc and calcium stearates, as stabilisers for polyvinyl chloride to control undesirable discolouration when heated. 17 refs. JAPAN... 

Pentaerythritol was chosen as long-term costabiliser. During normal stabilisation conditions, the polyol enhanced the induction time to degradation but produced large amounts of polyenes. The use of the preheated mixture of metal soaps and preheated zinc stearate enhanced even more such times, while preheated calcium stearate reduced them. The same effect was seen with the... 

A soap is an aliphatic or aromatic carboxylate, such as a stearate, benzoate, oleate, palmitate or myristate. An appropriate combination of two metal soaps can give rise to very useful PVC stabiliser systems. One must be chosen from Group llA of the periodic table (magnesium, calcium, strontium, or barium) and one from Group IIB (theoretically zinc or cadmium, but in practice cadmium is no longer used in Europe and most other countries). 

Mixed metal systems can be divided into solid and liquid types. Solid ones are calciiun-zinc combinations and are used to replace lead. The nature of the metal soap determines whether the stabiliser is liquid (as with the naphthenate, phenate and benzoate) or solid (stearate, ricinoleate and laurate). It also determines whether the PVC will be transparent. 

Traditional substances used as co-stabilisers include polyols, epoxidised soya bean oil, phosphites and certain antioxidants. Arkema markets Stavinor calcium stearate co-stabilisers for use with calcimn-zinc systems. Akcros Chemicals sells P24D, which stands for pyrrolidene-2,4-dione. Siid-Chemie is now marketing a synthetic hydrotalcite, Sorbacid 911, while the PQ Corporation is selling two grades of aluminosilicate (zeolite) imder the name Advera 401. They act as scavengers for acids and metal chlorides, and enable users of tin mercaptides to use less tin, saving on material costs. They also allow stabiUsation to take place with the very low tin levels required by law in food contact applications. 

Of the other types of organo-metallic stabilisers, Mal kova and co-workers (a.l7) have described an alternating current polarographic method for the determination of cadmium, zinc and barium stearates or laurates in PVC. Other techniques used on PVC extracts include, column chromatography for barium, cadmium and zinc salts of fatty acids, paper chromatography for cadmium, lead and zinc salts of fatty acids (a. 18) and polarography for cadmium, lead and zinc salts (a. 19). 

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