Calcium/zinc stabilizers

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. 

Calcium—zinc stabilizers are used in both plasticized PVC and rigid PVC for food contact where it is desired to minimize taste and odor characteristics. AppHcations include meat wrap, water botdes, and medical uses. 

Many stabilizers require costabilizers. Several organic costabilizers are quite useful with barium—zinc and calcium—zinc stabilizers, eg, P-diketones, epoxies, organophosphites, hindered phenols, and polyols (122). 

The addition of small amounts of various stabilizers to untreated or polybutadiene-grafted PVC decreased the rate of hydrogen chloride evolution. Thus, as shown in Figure 1, 0.15 phr which is less than 10% of the recommended amounts of a mixture of non-toxic calcium-zinc stabilizers, increased the time for 0.1 mole % dehydrochlorination of suspension polymerized PVC from 28 to 36 minutes and of Type M PVC prepared from the suspension polymer from 41 to 47 minutes. Type P PVC prepared from the same polymer required 49 minutes for the same extent of dehydrochlorination. 

The inclusion of heat stabilizers is essential to protect the system against thermal decomposition at elevated temperatures during processing. For this purpose, tin carboxylate esters or liquid calcium-zinc stabilizers are preferred. Thio-tin compounds are very effective as heat stabilizers but must be regarded with caution, bearing in mind that they can lead to unpleasant and unacceptable residual odours. Secondary stabilizers that can be used include epox-idized soya bean oil. 

Liquid calcium-zinc stabilizer blends present a green alternative without sacrificing performance. 

The traditional stabilizer for hard PVC, harking back to the beginnings of PVC processing, is the cadmium-based stabilizer that was subsequently replaced by lead-based stabilizers for the most part in the 1980s. The demand for PVC formulae free of heavy metals has today led to an increasing use of calcium-zinc stabilizers free of heavy metals [23]. The many different demands made on modem PVC mixtures can hardly be met by one stabilizer alone, so that current practice frequently combined different stabilizer systems. Stabilizers are added to mixtures at ratios of around 14% by mass. 

Calcium-zinc stabilizer n. Any of a family of stabilizers based on compounds and mixtures of compounds of calcium and zinc. Their effectiveness is Hmited, but they are among the few that have been approved by the FDA for materials to be contacted by foods. 

Specialty Amines. Some substituted nitrogenous compounds can provide similar benefits. Esters of 2-aminocrotonate andbis-2-aminocrotonate, and appropriately substituted dihydropyridines, eg, 3,5-bis-lauryloxycarboxy-2,6-dimethyl-1,4-dihydropyridine [37044-66-7] and 3,5-bis-ethoxycarboxy-2,6-dimethyl-l,4-dihydrop3rridine [1149-23-1], are examples of these costabilizers. These relatively expensive costabilizers are used at 0.1-0.7 phr and are particularly effective when added to the calcium-zinc stabilizers. 

Mixed metal stabilizers, such as those used in flexible compounds, have generally not been used for rigids, with the exception of calcium/zinc stabilizers for some food grade bottles and sheet. Recently, more robust calcium/zinc formulations have been developed for rigid extrusion, including for pipe. 

Probably the most prevalent antioxidant in worldwide use is the para-methyl derivative of 2,6-di-t-butylphenol, BHT (here abbreviated as A/O—CH3). BHT is low-cost and fast-acting (highly mobile), and has many regulatory approvals. It has been used in (or with) organotin and calcium/zinc stabilizers for food contact and medical applications. BHT is volatile and inappropriate for service at elevated temperatures. It reacts rapidly with oxides of nitrogen, leading to discoloration and is thus unsuitable for outdoor use. The most pervasive problem is its oxidation ... 

An antioxidant widely used in recent barium/zinc- and calcium/zinc-stabilized PVC compositions is l,l,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, Topanol CA (AstraZeneca). This antioxidant has three hindered phenolic groups linked in the para position to the butane chain. Each has a t-butyl group ortho to the phenol, but has a methyl group, not in the other ortho position, but meta to the phenol. This leaves a more or less unblocked activated ortho C—H. This structure permits the antioxidant to act both in a repetitive and in a sacrificial mode, which... 

Lead-stabilized wire coverings generally use 0.2-0.5 phr of stearic acid to increase the mobility of the stabilizer that is, to act as an internal lubricant in the vicinity of the insoluble stabilizer particle. If the stabilizer itself is soluble, as with barium/lead stearate blends, the addition of stearic acid is unnecessary. The practice of using 0.25 phr stearic acid has carried over to those compounds that use barium/zinc or calcium/zinc stabilizers, where it is also probably unnecessary. 

NBR is also used to modify PVC/ABS blends, partieularly for automotive crash pads. A typical triblend may be based on 75 phr of ABS resin and 25 phr of a medium-Mooney-viseosify, usually crosslinked, NBR, plus a polymeric plasticizer, filler, pigments, antioxidant and stabilizCT. The dibasic lead phosphite originally used in such blends is being replaced with calcium/zinc stabilizers plus phosphite costabilizers. 

Fluidized Bed-Coated Dishwasher Racks As these compounds may contain up to 25 phr of filler and pigment, and 50-60 phr of phthalate plasticizer (chosen for low odor and extractability), a resin of 0.85-0.95 IV is desirable. Nontoxic calcium/ zinc stabilizers are used, with 4-5 phr of epoxidized soybean oil (ESO) and 2-4 phr of a dispersion resin. 

Rigid PVC extmsion compounds based on organotin stabilizers require about 1.5-2.5phr of total additive lubricants, properly balanced for the type of extmder. Lubricant levels much beyond these extremes will result in either under- or overlubricated conditions—seen as rough surface, sticking, melt fracture, and overheating in the former instance, or surging, lumpiness, and incomplete fusion in the latter. Much less lubricant is needed when lead, barium/cadmium or calcium/zinc stabilizers are used. 

Low cost non-toxic calcium/zinc stabilizer with equivalent effectiveness to tribasic lead sulfate. Epoxidized oils are not required with Halstab 1130. 

Low cost, non-toxic slightly lubricating calcium/zinc stabilizer with the effectiveness of a lead stabilizer. Does not require ESO. Epoxidized oils are not necessary. Primary applications Cable jackets and other filled compounds. General purpose and flexible PVC compounds. Can also be used as a booster for liquid stabilizers. 

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