Stabilization with metal soaps

Wypych J. The nature of synergism in stabilization with metal soaps and secondary stabilizers. Polym Mater Sci Eng 1985 52 545-9. 

Other stabilizers include special zincs for plasticized applications such as cable and organics added to calcium/zinc or used for pipe extrusion and co-stabilizers for metal soap and tin, improving long-term heat stability. Kickers (liquid barium/zinc and potassium/zinc) are PVC stabilizers that catalyse the decomposition of a blowing agent to be effective at lower temperatures, and can be used for sponge leather calendering. Epoxidized compounds are effective co-stabilizers in most systems chelators with metal soap improve heat stability. 

One may rationalize emulsion type in terms of interfacial tensions. Bancroft [20] and later Clowes [21] proposed that the interfacial film of emulsion-stabilizing surfactant be regarded as duplex in nature, so that an inner and an outer interfacial tension could be discussed. On this basis, the type of emulsion formed (W/O vs. O/W) should be such that the inner surface is the one of higher surface tension. Thus sodium and other alkali metal soaps tend to stabilize O/W emulsions, and the explanation would be that, being more water- than oil-soluble, the film-water interfacial tension should be lower than the film-oil one. Conversely, with the relatively more oil-soluble metal soaps, the reverse should be true, and they should stabilize W/O emulsions, as in fact they do. An alternative statement, known as Bancroft s rule, is that the external phase will be that in which the emulsifying agent is the more soluble [20]. A related approach is discussed in Section XIV-5. 

Heat stabilizers protect polymers from the chemical degrading effects of heat or uv irradiation. These additives include a wide variety of chemical substances, ranging from purely organic chemicals to metallic soaps to complex organometaUic compounds. By far the most common polymer requiring the use of heat stabilizers is poly(vinyl chloride) (PVC). However, copolymers of PVC, chlorinated poly(vinyl chloride) (CPVC), poly(vinyhdene chloride) (PVDC), and chlorinated polyethylene (CPE), also benefit from this technology. Without the use of heat stabilizers, PVC could not be the widely used polymer that it is, with worldwide production of nearly 16 million metric tons in 1991 alone (see Vinyl polymers). 

Absorption of Hydrogen Chloride. Effective heat stabilizers have the abiHty to bind hydrogen chloride. Most stabilizer systems contain one or more metallic soaps or salts which readily undergo a simple acid—base reaction with the by-product hydrogen chloride as the PVC degrades ... 

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. 

However, in a 1963 lecture it was pointed out that ether soaps had special characterics [10], i.e., good biodegradability, mildness to the skin, and less corrosiveness to metals, and that we should expect these soaps to play an important role in the future. However, the real breakthrough of the ether carboxylates came in the 1980s, when environmental properties of surfactants became even more important along with other properties of ether carboxylates such as chlorine stability, anticorrosiveness, lime soap dispersibility, electrolyte stability, alkaline stability, and so on. 

The effects of release additives on bulk properties must also be carefully considered, particularly with integral additives to plastics. For example, partial solubility usually confers some plasticizing 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-stabilizer benefits. Such effects are exploited in multipurpose formulations. 

Typical lubricants are fatty alcohols C]2-C22, fatty acids C14-Ci8, their esters with fatty alcohols, glycerol or pentaerythritol, amides (2) or diamides (3) and metallic soaps (see Heat stabilizers ), acids C28-C31 from montan wax and their esters, diesters of phthalic acid (4b), paraffin wax C2o-C70, PE waxes Ci25-C70o or their oxidized (polar) grades containing hydroxyl and carbonyl groups. 

Concentration levels of heat stabilizers in various PVC products are in the range 1.5-3.0% for metal soaps and 0.3-2.5 % for organotin stabilizers (Pospfsil, 1990c). Aliphatic (22) or mixed aliphatic/aromatic phosphites (23, 24) are used together with polyols (e.g., pentaerythritol or sorbitol) and acid scavengers as co-stabilizers in PVC (Pospfsil, 1990c). 

LDPE and PTFE are manufactured by processes involving little contact with metals, and should not be a major source of aluminum. On the other hand, HDPE and PP have similar manufacturing processes, based on catalysis, that involve aluminum, among other metals. The contamination risk may therefore be very high. In addition, the manufacture of the container itself can lead to aluminum contamination, considering the use of lubricants, stabilizers and other additives. For example, metal soaps, such as aluminum, magnesium, sodium, and tin, were sanctioned by the FDA to be used as stabilizers in plastic containers for parenteral nutrition solutions [76]. 

Journal of Applied Polymer Science 19, No.11, 14th March 2001, p.2029-37 SYNERGETIC EFFECT OF DIMERIZED PENTAERYTHRITOL ESTERS WITH SYNERGETIC METAL SOAP ON THE STABILIZATION OF POLY(VINYL CHLORIDE) Ikeda H Goto H Higaki Y Sunami M NakanO K Nakamura Y Iida T... 

CNC Deionizer N is a chemical compound which inactivates iron, calcium and magnesium ions in textile processing solutions. It increases the stability of soap baths and prevents the formation of metallic soaps. It prevents the reaction of metals with dyestuffs and therefore eliminates dulling of shades due to metallic ions present in dye solutions. A small quantity of CNC Deionizer N is merely disssolved into the bath before detergent or dyestuff is added. CNC Deionizer N is effective over a wide temperature and pH range and may be used in any textile process where trace metals are a possible source of trouble. Listed are a few of the many uses for CNC Deionizer N ... 

The metallic soaps of barium, cadmium, lead, and calcium are commonly used as stabilizers. They are HCl acceptors, but their reaction products often cause cloudiness in clear formulations. Alkyl and aryl phosphates are often used with them to inhibit precipitation of insoluble chlorides. Tin complexes have also been used successfully. 

With Organotins. In recent years the ability of organotins and metal soaps (see below) to prevent the appearance of color in degrading PVC has been ascribed most frequently to chemical reactions leading to the deactivation of defect sites. Very strong evidence for the operation of such a mechanism, at least in the case of the organotins, has been provided now by the chemical stabilization effects whose discovery (22,23, 24,25) was noted above. However, these effects do not rule out the concurrent operation of other mechanisms in technological situations (22,23). 

Owing to metal chlorides titration by the coulometric method, and carboxylic acid titration by the potentiometric method, it is possible to follow the metal soaps consumption during thermomechanical heat treatments. This new technique provides a better understanding of the stabilization mechanisms of PVC with the calciumr-zinc system, and offers a better explanation of synergistic effects between metal soaps and secondary stabilizers such as epoxidized soya-bean oil, a-phenylindole, and butanediol-p-aminocroto-nate. The influence of these last stabilizers on zinc chloride formation enables us to classify them into short- and longterm stabilizers. 

In the zinc-calcium formulations, metal soaps are associated with secondary stabilizers such as alkylphosphites, epoxy compounds, a-phenyl-indole, or -aminocrotonate esters that bring a synergistic effect. The first attempt to study the mechanisms behind this effect has been the reaction of all of these compounds with 4-chloro-2-hexene. 

Stabilizers are almost invariably added to PVC to improve its heat and light stability. The species found effective in stabilizing PVC are those that are able to absorb or neutralize HCl, react with free radicals, react with double bonds, or neutralize other species that might accelerate degradation. Lead compounds, such as basic lead carbonate and tribasic lead sulfate, and metal soaps of barium, cadmium, lead, zinc, and calcium are used as stabilizers. Obviously, they can react with HCl. Epoxy plasticizers aid in stabilizing the resin. Another group of stabilizers are the organotin compounds, which find application because of their resistance to sulfur and because they can yield crystal-clear compounds. 

Fatty adds are predominantly used as intermediates. Main applieations are water soluble soaps for household eleaning, personal care, industrial and institutional (I I) cleaning and synthetic rubber manufacturing by emulsion polymerization. Soaps are made by reaction of fatty acids with caustic alkalis, alkali carbonate or ammonia or (>90%) by direct saponification of the triglyceride oil. Another important group of fatty add soaps are dry, water-insoluble metal soaps used as lubricants or stabilizers for PVC and other plastics and aqueous calcium stearate dispersions applied as paper coating... 

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