Polymerization inhibitors sulfur

Sulfuric acid is also a very satisfactory catalyst aluminum alkoxides also are useful, especially when the alcohols would be adversely affected by strong acids. Sodium alkoxides produce undesirable side reactions and give lower yields. When alkaline catalysts are employed, an alkaline polymerization inhibitor, such as j j-phenylenediamine or phenyl-d-naphthylamine, should be used instead of hydroquinone. 

The reaction of alkylene oxides or epoxides with sulfur dioxide to give cyclic sulfites is effected by carrying out the reaction at about 150°C for 4 hr at 2000 atm of S02 [28]. Pyridine is used in small amounts as a polymerization inhibitor. In addition, it has been reported that free radical-producing catalysts give improved yields and allow the reaction to be carried out at lower temperatures [28] (Eq. 19). 

Japanese investigators reported that liquid sulfur dioxide polymerizes styrene derivatives (e.g., p-methyl styrene, a-methyl styrene) (19). Unfortunately, the experiments were not executed under rigorously anhydrous conditions (high vacuum) so that the possibility for proton (e.g., sulfurous or sulfuric acid) initiation exists although the authors seem to believe that S02 is the catalyst, probably by the following process 2S0a SO2 +SO e. The cationic nature of the mechanisms was proven by the facts that no polysulfones formed, that the polymerization was inhibited by bases, and that free radical inhibitors did not affect the reaction. These authors also claim that formaldehyde is polymerized by sulfur dioxide to a product which does not contain sulfur and whose infrared spectrum closely resembles that of a low temperature sample. 

The crown structure of cpc/o-octasulfur, Sg, is only one member of an homologous series of S (n = 6-26) rings (Figure 4). Additionally, cyclic sulfur oxides such as SeO and S7O2 and mixed sulfur-selenium systems are known. These latter compounds are of some coimnercial significance, with applications as diverse as antidandruff shampoos, fireworks, and polymerization inhibitors. 

Acidolysis. One method for the preparation of anhydrous acrylic acid is by heating methyl acrylate with 98% formic acid in the presence of a catalytic amount of sulfuric acid and of hydroquinone as polymerization inhibitor. ... 

Use Stibonium salts, cocatalyst in converting trienes to aromatics and hydro aromatics, reacts with nitric-sulfuric acid to give trinitro derivatives, polymerization inhibitor, lubricating-oil additive. 

The exit stream is condensed and, after addition of a polymerization inhibitor (usually sulfur), is successively distilled under reduced pressure to a styrene purity of better than 99.7%. A few ppm of 4-t-butylcatechol inhibitor is added to the purified product after which it is ready to be shipped. Industrial yield (selectively) of styrene from ethylbenzene is about 90%. 

Purification this step features the second innovation of the process which, to eliminate the by-product acrolein, favors the formation of cyanohydrin by means of the hydrogen cyanide which is also present This operation takes place at low temperature (20 Q in agitated reactors, either continuously in the presence of a copper-based catalyst, or semi-continuously with a reaction phase in basic medium (caustic soda addition), followed by a neutralization period (sulfuric acid addition). The cyanohydrin obtained is then removed by vacuum distillation. The withdrawal may be sent to a thin layer evaporator to recover entrained acrylonitrile. These treatments must be conducted in the presence of a polymerization inhibitor and at a temperature below 55 C to prevent the rede-composition of cyanohydrin.... .. ... 

Uses Mfg. of diaminophenol, picric acid, picramic acid herbicide reagent for detection of potassium and ammonium ions chemical synthesis biochemical research acid-base indicator polymerization inhibitor in styrene prod. intermediate for prod, of azo dyes. Cl sulfur black 1, Cl sulfur black 2, explosives, photographic developers fungicide for metalcutting oil emulsions, railroad ties, wood, pressure-treated wood wood preservative insecticide, miticide to control mosquitoes formerly as metabolic stimulator to aid in weight reduction... 

Hazardous Decomp. Prods. Heated to decomp., emits toxic fumes of Sb Uses Stibonium salts cocatalyst in converting trienes to aromatics and hydroaromatics reacts with nitric-sulfuric acid to give trinitro derivatives polymerization inhibitor lubricating oil additive Manuf./Distrib. Aldrich http //www.sigma-aidrich.com] Fluka http //www.sigma-aidrich.com] Sigma... 

Under similar conditions, the emulsion polymerization of chloroprene proceeds about 700 times faster than that of isoprene. The resulting heat of polymerization therefore must be dissipated as quickly as possible by effective external cooling or by using flow techniques. Alternatively, the reaction rate can be moderated by adding an inhibitor. Sulfur is used commercially for this purpose with chloroprene, although this inhibitor cannot be used in the polymerization of butadiene or isoprene. Coagulation of emulsion is finally brought about by the addition of acids or multivalent salts. The emulsion polymerizates possess only about 1.5% 1,2 structures. 

The two types of inhibitors used in cyanoacrylate adhesives are radical polymerization inhibitors and anionic polymerization inhibitors. The former type are usually phenolic, for example, hydroquinone, p-methyloxyphenol, or hindered phenolics. They are generally employed in 0.1-1.0% concentrations. The amine- or sulfur-based inhibitors and the metal-chelating inhibitors should be avoided owing to their nucleophilic character. Radical inhibitors are used to protect the adhesive during storage from polymerization induced by heat or light and other adventitious radical sources. These... 

One method to reduce the volatility of sulfur dioxide is to complex it with imidazole and then add the complex to the adhesive. Chelates of boric acid derivatives with polyhydroxy compounds have also been prepared as anionic polymerization inhibitors. The chelates can be preformed or prepared in situ by adding the boric acid compound and the polyhydroxy compound to the adhesive. Sulfamides have been used to stabilize cyanoacrylates. The sulfamides (24) in question are prepared by reacting sulfuryl diisocyanate (23) with active hydrogen compounds such as carboxylic acids, as shown in Eq. (7). ... 

Other compounds have also been reported as effective anionic polymerization inhibitors. Organic sulfur compounds when added to the prepolymer slurry in the manufacturing process before cracking or depolymerization have been... 

Other miscellaneous compounds that have been used as inhibitors are sulfur and certain sulfur compounds (qv), picryUiydrazyl derivatives, carbon black, and a number of soluble transition-metal salts (151). Both inhibition and acceleration have been reported for styrene polymerized in the presence of oxygen. The complexity of this system has been clearly demonstrated (152). The key reaction is the alternating copolymerization of styrene with oxygen to produce a polyperoxide, which at above 100°C decomposes to initiating alkoxy radicals. Therefore, depending on the temperature, oxygen can inhibit or accelerate the rate of polymerization. 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials Attacks rubber and most fibrous materials. May cause ignition of organic materials such as wood. Some acids, such as sulfuric acid, may result in explosion Stability During Transport Stable Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

Ammonium salts of alkenyl succinic half-amides have teen described for use as corrosion inhibitors in oil and gas production technology to combat corrosion by media containing CO2, H2S, and elemental sulfur [1366]. The inhibitor composition may contain a dispersing agent, such as a low molecular weight or polymeric anionic surfactant like an alkylsulfonic acid or an alkyl-aryl sulfonic acid. 

Steel objects, when exposed to humid atmospheres or when immersed in electrolytes, corrode at a rapid rate. For example, abrasively polished, cold-rolled steel panels will show signs of rust within 15 minutes when immersed in dilute chloride solutions with pH in the range of 7-10. One of the methods used to control this rapid corrosion is to coat the metal with a polymeric formulation such as a paint. The role of the paint is to serve primarily as a barrier to environmental constituents such as water, oxygen, sulfur dioxide, and ions and secondarily as a reservoir for corrosion inhibitors. Some formulations contain very high concentrations of metallic zinc or metallic aluminum such that the coating provides galvanic protection as well as barrier protection, but such formulations are not discussed in this paper. 

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