Antioxidant metal soap

Typically, soHd stabilizers utilize natural saturated fatty acid ligands with chain lengths of Cg—C g. Ziac stearate [557-05-1/, ziac neodecanoate [27253-29-8] calcium stearate [1592-23-0] barium stearate [6865-35-6] and cadmium laurate [2605-44-9] are some examples. To complete the package, the soHd products also contain other soHd additives such as polyols, antioxidants, and lubricants. Liquid stabilizers can make use of metal soaps of oleic acid, tall oil acids, 2-ethyl-hexanoic acid, octylphenol, and nonylphenol. Barium bis(nonylphenate) [41157-58-8] ziac 2-ethyIhexanoate [136-53-8], cadmium 2-ethyIhexanoate [2420-98-6], and overbased barium tallate [68855-79-8] are normally used ia the Hquid formulations along with solubilizers such as plasticizers, phosphites, and/or epoxidized oils. The majority of the Hquid barium—cadmium formulations rely on barium nonylphenate as the source of that metal. There are even some mixed metal stabilizers suppHed as pastes. The U.S. FDA approved calcium—zinc stabilizers are good examples because they contain a mixture of calcium stearate and ziac stearate suspended ia epoxidized soya oil. Table 4 shows examples of typical mixed metal stabilizers. 

The effects of release additives on bulk properties must also be carefully considered, particularly with integral additives to plastics. Eor example, partial solubiHty usually confers some plastici2ing effect. This may improve impact strength but could reduce the heat distortion temperature. Some release additives such as metallic soaps have secondary antioxidant and heat-stabiH2er benefits. Such effects are exploited in multipurpose formulations. 

Saturated hydrocarbons (waxes), fatty acids, metal soaps, fatty acid amides and esters (primarily Cig-Cis) act as internal lubricants, fluoro elastomers as external lubricants. Many other polymer additives, e.g. antistatic agents, antifogs, antioxidants, UV stabilisers, etc., act as lubricants in the barrel of the extruder once they are in the liquid form. 

In addition to the antioxidants, other co-stabilisers, such as metal soaps as acid acceptors, are also added. Metal soaps are used to neutralize resi-... 

Phospholipids can form salts, for example with metal ions, due to the presence of one free hydroxyl group of the bound phosphoric acid in phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol and two free hydroxyl groups in phosphatidic acid. Mostly, calcium and magnesium ions are involved in these reactions, but the resulting complexes have hydrophobic character, as in metal soaps. Cations of heavy metals (copper, manganese and iron) bound in phospholipids catalyse autoxidation significantly less than free metal ions, phospholipids can thus become synergists of antioxidants. 

Ba/Cd stabilisers are fatty acid soaps and the choice of organic acid (lauric, stearic, ricinoleic, etc) is critical in calendering application to minimise the risk of plate-out. Ba/Cd and Ba/Cd/Zn stabilisers are often sold as a tailor-made complex package for a particular application, and may contain antioxidants such as diphenylol propane, phosphite chelators and other ingredients in addition to the metal soaps. Usual levels of addition are 1-3 phr, the lower levels being used in certain plastisols subject to fairly mild curing conditions. 

Epoxidized oils (- epoxides) are used as plasticizers, stabilizers and antioxidants for some coatings. Other plasticizers are - fatty acid esters, stand oils (- drying oils) and - castor oil. - Fatty acid amides and - metallic soaps (Zn and Ca) are used as matting or flattening agent and as hydro-phobic additive. Fatty acid derivatives, such as - glyceryl monostearate, chlorides and ammonium salts, improve the electric conductivity while - fatty amine ethoxylates, fatty acid amides and ammonium sulfates function as antistatic additives. Lit UUmann (5.) A18,465... 

Besides the metal soaps and general antioxidants, some species used to stabilize poly(vinyl chloride) are organotin compounds, epoxy compounds, phosphites, and... 

The basic metal salts and soaps tend to be less cosdy than the alkyl tin stabilizers for example, in the United States, the market price in 1993 for calcium stearate was about 1.30— 1.60, zinc stearate was 1.70— 2.00, and barium stearate was 2.40— 2.80/kg. Not all of the coadditives are necessary in every PVC compound. Typically, commercial mixed metal stabilizers contain most of the necessary coadditives and usually an epoxy compound and a phosphite are the only additional products that may be added by the processor. The requited costabilizers, however, significantly add to the stabilization costs. Typical phosphites, used in most flexible PVC formulations, are sold for 4.00— 7.50/kg. Typical antioxidants are bisphenol A, selling at 2.00/kg Nnonylphenol at 1.25/kg and BHT at 3.50/kg, respectively. Pricing for ESO is about 2.00— 2.50/kg. Polyols, such as pentaerythritol, used with the barium—cadmium systems, sells at 2.00, whereas the derivative dipentaerythritol costs over three times as much. The P-diketones and specialized dihydropyridines, which are powerful costabilizers for calcium—zinc and barium—zinc systems, are very cosdy. These additives are 10.00 and 20.00/kg, respectively, contributing significantly to the overall stabilizer costs. Hydrotalcites are sold for about 5.00— 7.00/kg. 

In the Codex Alimentarius (42), maximum free fatty acid levels are specified as 0.65% for lard, 1.00% for premier jus, and 1.25% for rendered pork fat and edible tallow. For all these, a peroxide maximum of lO-miUiequivalents active oxygen per kilogram fat is specified. The Codex standards also specify levels for antioxidants and antioxidant synergists and maximum allowed amounts of impurities, soaps, and certain metals. 

Properties Yel. clear liq. sol. in most org. soivs. and oils pract. insol. in water m.w. 365.60 dens. 0.93 kg/l f.p. -31 C amphoteric Uses Emulsifier, corrosion inhibitor in sol. cutting oils antifoam for antibiotic prod. pigment grinding aid and dispersant wetting agent for paper, textiles, metal cleaners detergent antioxidant emulsion stabilizer acid acceptor in salts, soaps antistat Trade Names Alkaterge -E... 

Soaps must also contain an appropriate preservative system, which is usually a combination of a chelating agent such as ethylene diamine tetraacetic acid (EDTA) to complex any free metal ions and an antioxidant to prevent possible oxidation of the fatty constituents. For example, the presence of copper or iron can cause discoloration and unpleasant smells resulting from a catalytic oxidation of unsaturated oils (Table 6.1). 

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