Heat stabilizers organic soaps

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). 

The prints exhibit excellent application properties. They are, for instance, entirely fast to organic solvents, soap, alkali, and acids. They are also fast to sterilization. Metal deco prints demonstrate very good heat stability. The products withstand exposure to 200°C for 10 minutes or to 180°C for 30 minutes. Although not quite as fast to heat as halogenated types of Copper Phthalocyanine Green, P.B.15 3 is thus somewhat more heat stable than stabilized a-Copper Phthalocyanine Blue. 

Market Volume. The total market for PVC heat stabilizers may be about 100 million pounds in the United States and 1 biUion pounds worldwide, half for organotin and half for metal soap-epoxidized fatty ester-organic phosphite systems. 

Metallic soaps and salts of stearic acid and other organic acids are used both as lubricants and as auxiliary heat stabilizers. Metallic stearates are the most widely used lubricants. They are predominantly used in PVC, but also find use in polyolefins, ABS, polyesters, and phenolics. The primary disadvantage of metallic stearates is their lack of clarity. Calcium stearate, the most common metallic stearate, is primarily used as an internal lubricant, but in PVC applications it provides external lubrication and mold-release characteristics while also acting as a heat stabilizer. In addition to PVC, the calcium sterarates go into polypropylene, polystyrene, and ABS. Zinc stearates are used in crystal and impact polystyrene, ABS, and phenolics. 

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. 

Composite heat stabilizers are liquid or solid compounds based on salts or metal soaps and compounds based on organic tin. Metal salts include Ca-Mg-Zn, Ba-Ca-Zn, Ba-Zn, and Ba-Cd common organic acids include organic fatty acids, naphthenic acid, oleic acid, benzoic acid, and salicylic acid. 

Some additives used in plastics are surfactants but are not used primarily for their surface or interfacial activity. Rather they contain functional groups that, because of their chemical nature, are polar but they also contain non-polar groups, such as hydrocarbon chains, in order to provide compatibihty with the polymer. Good examples are the heat stabilizers used in plastics such as PVC to prevent thermal degradation. Typical additives used for this purpose are soaps (metal salts of alkyl carboxylates) or metal salts of other organic acids such as phenols. The metal cations used most commonly are tin, calcium, barium, zinc and cadmium. Lead salts are also used in electrical cables, pipes and window frames. Tin salts are especially useful for stabilizing clear, rigid PVC bottles. 

A thermal stabilizer is used to improve the chemical stability of PVC at processing temperatures. Many highly effective PVC thermal stabilizers are already known [16,23-29], but their action mechanism is not yet completely established [13,30-33]. Frye and Horst [34,35] suggest the following mechanism for an organic soap type heat stabilizer where chlorine atoms in labile positions are replaced by the alkyl carboxylate group as follows ... 

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