Monomer stabilization sulfuric acid

The performance of many metal-ion catalysts can be enhanced by doping with cesium compounds. This is a result both of the low ionization potential of cesium and its abiUty to stabilize high oxidation states of transition-metal oxo anions (50). Catalyst doping is one of the principal commercial uses of cesium. Cesium is a more powerflil oxidant than potassium, which it can replace. The amount of replacement is often a matter of economic benefit. Cesium-doped catalysts are used for the production of styrene monomer from ethyl benzene at metal oxide contacts or from toluene and methanol as Cs-exchanged zeofltes ethylene oxide ammonoxidation, acrolein (methacrolein) acryflc acid (methacrylic acid) methyl methacrylate monomer methanol phthahc anhydride anthraquinone various olefins chlorinations in low pressure ammonia synthesis and in the conversion of SO2 to SO in sulfuric acid production. 

Once the latex is properly terminated, the unreacted monomers are removed from the latex. Butadiene is stripped by degassing the latex by means of flash distillation and reduction of system pressure. Styrene is removed by steam stripping the latex in a column. The latex is then stabilized with the appropriate antioxidant and transferred to blend tanks. In the case of oil-extended polymers or carbon black master batches, these materials are added as dispersions to the stripped latex. The latex is then transferred to finishing lines to be coagulated with sulfuric acid, sulfuric acid/sodium chloride, glue/sulfuric acid,... 

CHLOROSTYRENE or o-CHLOROSTYRENE (2039-87-4) Combustible liquid (flash point 143°F/62°C). Able to form unstable peroxides (may be stabilized with 0.1% hydroquinone). Contact with strong oxidizers may cause fire and explosions, strong acids. Incompatible with strong bases, butyl lithium, 2,5-dimethyl2,5-di(tert-butylperoxy)hexane, ferric chloride, halogens, sulfuric acid, xenon tetrafluoride. The uninhibited monomer vapor may block vents and confined spaces by forming a solid polymer material. 

Inhibition of spontaneous polymerization of (meth) acrylates is necessary not only at their storage but also in the conditions of their synthesis proceeding in the presence of sulfuric acid. In this case, monomer stabilization is more urgent, since sulfuric acid not only deactivates mat r inhibitors but also is capable of intensifying polymer formation. The concentration dependence of induction periods in these conditions has a brightly expressed nonlinear character. And, unlike polymerization in bulk, decomposition of polymeric peroxides is observed at relatively low temperatures in the presence of sulfuric acid, and the values [X] of the amines studied are by ca. 10 times lower than [HQ]. ... 

Inhibition of spontaneous polymerization of (meth) acrylates is necessary not only at their storage but also in the conditions of their synthesis proceeding in the presence of suffirric acid. In this case, monomer stabilization is more urgent, since sulfuric... 

Kinetic analysis gives additional information related to the reactivity of the free radicals obtained during the processes following a photoinduced electron transfer process. A variation in radical reactivity could be caused, for example, by their stability or their reactivity with monomer, as in the case of photoinitiation by 4-carboxybenzophenone-sulfur-containing carboxylic acid of free-radical polymerization [184]. 

The very first reported PHOST that is transparent in the DUV was prepared by thermolysis or acidolysis of PBOCST, which is in turn prepared via radical polymerization of the BOCST monomer by 2,2-azobis(butyronitrile) (AIBN), benzoyl peroxide (BPO), or other radical initiators. The BOCST monomer can be prepared by the Wittig reaction on a protected 4-hydroxybenzaldehyde with a rather high yield due to the good stability of the t-BOC group toward a base cata-lyst. " The PBOCST polymer thus obtained is readily converted to PHOST by heating the polymer to 200°C or by treating the polymer with an acid such as acetic acid or HCl in solution. And PBOCST can be synthesized via cationic polymerization in liquid sulfur dioxide. ... 

The third stage of this process, the thermal retropolymerization is conducted at temperatures between 150 and 300°C. Often a heat transfer agent, a high-boiling liquid such as tricresyl phosphate, is added at this stage.The heat transfer agent acts to lower the viscosity of the depolymerization mixture and to decrease the depolymerization temperature. The toluene must be fully stripped before depolymerization commences, and a radical inhibitor and an acid polymerization stabilizer are added to the pot. The depolymerization is conducted under high vacuum, and often in the presence of an acid gas such as sulfur dioxide. The raw monomer is... 

The monomer solution makeup involves addition and solubilization of elemental sulfur and rosin (substituted diterpenes) in the chloroprene monomer. The water solution is made in a second vessel. Deionized water, sodium hydroxide, and a dispersant are mixed to form the water solution. The dispersant is a condensation product of naphthalene-sulfonic acid and formaldehyde. The monomer and water solutions are mixed with centrifiigal pumps to form an oil-in-water emulsion. The emulsion formed by virtue of formation of the sodiiun salt of rosin and resin components (abietic and dehydroabietic acids) having hydrophobic and hydrophilic ends. The large carbon-bearing portion of sodium abietate is hydrophobic and thereby solubilizes the monomer. The sodium carboxylate portion of sodium abietate is the hydrophilic end that extends into the aqueous phase and forms the electronic double layer that is critical to emulsion stability (84,85). In the patent example, the emulsion was added to the reactor and the temperatiu-e was increased to 40°C polymerization temperatiu-e (Table 3). 

Cationic polymerization is the direct analogue of anionic polymerization but with a cation at the terminus of the growing polymer chain. Initiators are either strong acids such as sulfuric, perchloric, or hydrochloric acids, or Lewis acids such as BF3 or T1CI4. Usually the Lewis acids require water or methanol as a "cocatalyst", suggesting that the reactive initiator is actually a protic acid. The list of viable monomers is somewhat limited, including isobutene, methyl vinyl ether, and butadiene—all structures that can give stabilized cations. Cationic polymerizations are the least common of the types discussed here. 

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