Stability laurates

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. 

Somewhere in the middle are soy lecithin and sorbitan mono-laurate, which make good foam stabilizers in whipped cream and similar products. 

Zinc, nickel, lead, and cadmium salts Ba-Cd-Zn stabilizers Organo-nickel complexes CdS, CdSe, lead stearate Cadmium laurate Stabilizers Pigments Lubricants... 

A number of cobalt(III) encapsulated cage complexes have been used as electron-transfer agents their advantage over viologens is their long-term stability in photochemical cycles. The most effective complex is [CoL] where L is l-chloro-3,6,10,13,16,19-hexaazabicyclo[6.6.6]eico-sane at a concentration of 4 x 10 mol dm , this cage exhibits a similar ability to methylviolo-gen to produce Laser flash photolysis in sodium dodecyl sulfate and sodium laurate... 

Wherever possible, the soaps and surfactants were added to the natural rubber latex as dilute aqueous solutions. The cases where this was not possible were (a) ethylene oxide-fatty alcohol condensates of low ethylene oxide fatty alcohol mole ratio, and (b) sparingly-soluble fatty-acid soaps such as lithium laurate and calcium soaps. The former were added as pastes with water, the latter as dry powders. In all cases, the latex samples were allowed to mature for about three days at room temperature before their mechanical stabilities were determined. This allowed some opportunity for the attainment of adsorption equilibrium. 

Counterion effects (5). Experiments which have been carried out using lithium, sodium, potassium, ammonium and morpholinium laurates have shown that the effects of these five laurates upon mechanical and chemical stability are broadly similar, although such differences as are observed are statistically significant. 

The results for effects upon mechanical stability are summarised in Table II. That lithium laurate behaves similarly to, say, potassium laurate is perhaps surprising, in that it is known that a lithium salt is mor ffective in reducing the mechanical stability of natural rubber -ftian is the corresponding potassium salt (6.). The inference has been drawn that the counterion of the car-boxylate soap has a negligible effect upon the ability of the soap to enhance mechanical stability, relative to the effect of the anion, at least for those cations for which specific adsorption effects are absent. 

Table II shows that morpholinium laurate is markedly less effective in enhancing mechanical stability than are the other laurates which have been investigated. This is attributed to specific counterion adsorption, with a consequent reduction of the effective surface potential at the rubber-water interface.

The abilities of the five laurates to protect natural rubber latex against chemical destabilisation appear to be broadly parallel to their effects upon mechanical stability. 

We have also recently discovered that added calcium laurate is able markedly to enhance the mechanical stability of natural rubber latex (2.). This observation is surprising, partly because of the low solubility of calcium laurate in water, and partly because calcium ions are known to be powerful destabilisers of natural rubber latex (j ). It indicates that the stabilising effect of the laurate anion is much greater than the destabilising effect of the calcium cation. 

It is important to point out that our investigation of counterion effects in carboxylate soaps has so far been concerned almost exclusively with laurate soaps. Laurate soaps were chosen partly because they are generally convenient to handle in that many of them are readily soluble in water to give solutions of low viscosity, and partly because, as has been shown above, laurate soaps are very effective in enhancing the mechanical and chemical stability of natural rubber latex. It must therefore be borne in mind that the conclusions which have been drawn from this investigation concerning effects attributable to counterion variation in laurate soaps may not be generally valid for carboxylate soaps as a family. 

Table II Effects of added laurate soaps of various counterions upon mechanical stability of natural rubber latex (5)...

Some data are also available for the effect of the counterion of a dodecyl sulphate upon its ability to enhance the mechanical stability of natural rubber latex. As in the case of the laurates the lithium, sodium, potassium and ammonium salts are similar in behaviour, but the morpholinium salt is slightly less effective. Again, the latter effect is attributed to specific adsorption of the morpholinium cation. Calcium and magnesium dodecyl sulphates are also effective in enhancing mechanical stability, their abilities being similar to that of morpholinium dodecyl sulphate. 

The reaction of 4-chloro-2-pentene with dibutyltin dilaurate, one of the first to be studied, provided some interesting observations. A plot of liberated chlorine vs. time (Figure 1) shows the reaction to be auto-catalytic. Investigation led to the discovery that dibutyltin dichloride, a product of the stabilization reaction, is a catalyst for the reaction (Figure 1). Further investigation revealed that at the outset all the reaction takes place by the unimolecular decomposition of the allylic chloride and that not until species with tin—chlorine bonds are present does this stabilizer undergo reaction with the allylic chloride. The reactive stabilizer in this instance is dibutyltin laurate chloride. Dibutyltin dilaurate does not react with the allylic chloride, and dibutyltin dichloride, which is very reactive,... 

Ba-Cd La = barium-cadmium laurate stabilizer (Ferro 1820, containing 15% Ba, 8% Cd)... 

Diepoxyethylbenzene was first prepared by Everett and Kon (3) as a liquid which evidently was not pure because analysis showed a difference of 4% in the carbon content. Our product was a white crystalline mass with melting point 79°C. and boiling point 95°C. at 0.06 mm. Catalytic hydrogenation gave the theoretical absorption. The stabilizing effect in PVC mixtures was about 30% of dibutyltin laurate—i.e., 3.3 times more of the stabilizer is necessary to obtain the same discoloration as dibutyltin laurate in a plasticized mixture of PVC with 30% dioctylph-thalate at 200°C. for 20 minutes. 1,3,5-Triacetylbenzene was prepared by the two methods mentioned above. 

Di(epoxyethyl)diphenyl was obtained from diphenyl by Friedel-Crafts reaction with chloracetyl chloride. Meerwein-Ponndorf reduction gave the dichlorohydrin, and treatment with alcoholic potassium hydroxide gave 97% of the theoretical yield of diepoxide, (f.p., 161 °C.). The stabilizing effect was about one-fourth that of dibutyltin laurate. 

The practical stability tests of these epoxides showed that there is a relationship between the number of epoxide groups and the stabilizing effect, but this behavior does not occur in all cases. Thus, for example, the epoxides of the Diels-Alder adducts of butadiene are not as effective as the diepoxides of diphenyl. The best effects were obtained with 1,3,5-triepoxyethylbenzene (ca. half the effect of dibutyltin laurate). Unfortunately, the stability of this product on storage is not satisfactory. After four weeks standing at normal temperature a considerable part of the... 

The stabilizing effect of organotin compounds can also be used for internal stabilization. In this respect, a French patent of 1957 suggests copolymerization of vinyl chloride with small amounts of a vinyltin compound (e.g., the vinyldiethyl laurate of tin), which considerably improves the thermal stability over homopolymeric vinyl chloride (8). An American patent of 1959 suggests two types of organotin compounds as stabilizers (13) ... 

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