Acid solution polymerization

Chemical Reactivity - Reactivity with Water Reacts violently forming flammable hydrogen gas and a strong caustic solution Reactivity with Common Materials May ignite combustible materials if they are damp or moist Stability During Transport Stable if protected from air and moisture Neutralizing Agents for Acids and Caustics Caustic that is formed by the reaction with water should be flushed with water and then can be rinsed with dilute acetic acid solution Polymerization Not pertinent Inhibitor of Pofymerization Not pertinent. 

Several isopolymolybdates which have been isolated from solution are polymeric or appear to have structures that do not persist in solution. These include the trimolybdates M2M03O10 XH2O, obtained as fibrous crystals from appropriately acidified solutions. The structures of Rb2Mo3Oi0H2O and RbNaMo3Oio contain infinite double chains of edge-shared MoOs octahedra.42 From more acidic solution polymeric pentamolybdates [MMosOi6H(H20)] slowly crystallize. The structure of the potassium salt reveals a complex three-dimensional network of MoOe octahedra.43... 

The tendency toward Pu(IV) polymerization is of considerable practical importance in process operations involving plutonium solutions. Dilution of an acidic plutonium solution with water can result in polymerization in localized regions of low acidity, so plutonium solutions should be diluted instead vdth acid solutions. Polymerization can result from leaks of steam or water into plutonium solutions or by overheating during evaporation. Polymer formation can clog transfer lines, interfere with ion-exchange separations, cause emulsification in solvent extraction and excessive foaming in evaporation, and can result in localized accumulation of plutonium that may create a criticality hazard [CS]. 

Stable YSZ colloidal sol was prepared by mixing 8YSZ nano-powder (Tosoh Cooperation, Tokio, Japan and Sigma-Aldrich GmbH, Steinheim, Germany) with diluted nitric acid solution. Polymeric... 

Scott, R. A., Peppas, N. A. (1997). Kinetic study of acrylic acid solution polymerization. 

The amide group is readily hydrolyzed to acrylic acid, and this reaction is kinetically faster in base than in acid solutions (5,32,33). However, hydrolysis of N-alkyl derivatives proceeds at slower rates. The presence of an electron-with-drawing group on nitrogen not only facilitates hydrolysis but also affects the polymerization behavior of these derivatives (34,35). With concentrated sulfuric acid, acrylamide forms acrylamide sulfate salt, the intermediate of the former sulfuric acid process for producing acrylamide commercially. Further reaction of the salt with alcohols produces acrylate esters (5). In strongly alkaline anhydrous solutions a potassium salt can be formed by reaction with potassium / /-butoxide in tert-huty alcohol at room temperature (36). 

Aqueous mineral acids react with BF to yield the hydrates of BF or the hydroxyfluoroboric acids, fluoroboric acid, or boric acid. Solution in aqueous alkali gives the soluble salts of the hydroxyfluoroboric acids, fluoroboric acids, or boric acid. Boron trifluoride, slightly soluble in many organic solvents including saturated hydrocarbons (qv), halogenated hydrocarbons, and aromatic compounds, easily polymerizes unsaturated compounds such as butylenes (qv), styrene (qv), or vinyl esters, as well as easily cleaved cycHc molecules such as tetrahydrofuran (see Furan derivatives). Other molecules containing electron-donating atoms such as O, S, N, P, etc, eg, alcohols, acids, amines, phosphines, and ethers, may dissolve BF to produce soluble adducts. 

Development efforts at Celanese Research Co. estabHshed soHd-state polymerization as the most practical process for engineering scale-up. Homogeneous solution polymerization of PBI in polyphosphoric acid was eliminated because of the need to work with low soHd compositions (in the range of 3—5%) during the precipitation, neutralization, and washing steps required for isolation of the product. 

The first-order decomposition rates of alkyl peroxycarbamates are strongly influenced by stmcture, eg, electron-donating substituents on nitrogen increase the rate of decomposition, and some substituents increase sensitivity to induced decomposition (20). Alkyl peroxycarbamates have been used to initiate vinyl monomer polymerizations and to cure mbbers (244). They Hberate iodine quantitatively from hydriodic acid solutions. Decomposition products include carbon dioxide, hydrazo and azo compounds, amines, imines, and O-alkyUiydroxylarnines. Many peroxycarbamates are stable at ca 20°C but decompose rapidly and sometimes violently above 80°C (20,44). 

At equihbrium, the specific composition of a concentrated phosphoric acid is a function of its P2 s content. Phosphoric acid solutions up to a concentration equivalent of about 94% H PO (68% P2O5) contain H PO as the only phosphoric acid species present. At higher concentrations, the orthophosphoric acid undergoes condensation (polymerization by dehydration) to yield a mixture of phosphoric acid species (Table 5), often referred to genericaHy as polyphosphoric or superphosphoric acid, H20/P20 = - 3, or ultraphosphoric acid, H20/P20 = - 1. At the theoretical P2O5 concentration for orthophosphoric acid of 72.4%, the solution is actually a mixture containing 13% pyrophosphoric acid and about 1% free water. Because the pyrophosphoric acid present is the result of an equihbrium state dependent on the P2 5 content of the solution, pure orthophosphoric acid can be obtained because of a shift in equihbrium back to H PO upon crystallization. 

Primary aromatic amines react with aldehydes to form Schiff bases. Schiff bases formed from the reaction of lower aUphatic aldehydes, such as formaldehyde and acetaldehyde, with primary aromatic amines are often unstable and polymerize readily. Aniline reacts with formaldehyde in aqueous acid solutions to yield mixtures of a crystalline trimer of the Schiff base, methylenedianilines, and polymers. Reaction of aniline hydrochloride and formaldehyde also yields polymeric products and under certain conditions, the predominant product is 4,4 -methylenedianiline [101 -77-9] (26), an important intermediate for 4,4 -methylenebis(phenyhsocyanate) [101-68-8], or MDI (see Amines, aromatic amines, l thylenedianiline). 

Fig. 10. Polymerization behavior of silica. In basic solution (B), particles grow in size and decrease in number in acidic solution or in the presence of flocculating salts (A), particles aggregate into three-dimensional networks and form gels (1).

In acidic solutions, equiUbtium is achieved more slowly. Polymerization of smaller species appears to occur sequentially a given polymer species first increases in size and then disappears, presumably because of its inclusion in higher order polymers. Depolymerization of siUcate species appears to be rapid, because crystalline Na2Si02 and Na2H2Si04 8H2O yield equivalent distributions of siUcate species in water upon dissolution. 

Solution Polymerization. In solution polymerization, a solvent for the monomer is often used to obtain very uniform copolymers. Polymerization rates ate normally slower than those for suspension or emulsion PVC. Eor example, vinyl chloride, vinyl acetate, and sometimes maleic acid are polymerized in a solvent where the resulting polymer is insoluble in the solvent. This makes a uniform copolymer, free of suspending agents, that is used in solution coatings (99). 

The tetramer exists in two-molal zirconium chloride and nitrate solutions, but it polymerizes into cross-linked chains on hydrolysis (190—191) in strong acid solutions, the hydroxyl bridges can be replaced by other anions to form trimers (192) and monomers (192—193). 

Antimonic acid has been used as an ion-exchange material for a number of cations in acidic solution. Most interesting is the selective retention of Na" in 12 Af HQ, the retention being 99.9% (24). At lower acidities other cations are retained, even K". Many oxidation and polymerization catalysts are listed as containing Sb203. 

Polyborates and pH Behavior. Whereas bode acid is essentiaHy monomeric ia dilute aqueous solutions, polymeric species may form at concentrations above 0.1 M. The conjugate base of bode acid in aqueous systems is the tetrahydroxyborate [15390-83-7] anion sometimes caHed the metaborate anion, B(OH) 4. This species is also the principal anion in solutions of alkaH metal (1 1) borates such as sodium metaborate,... 

Commercial aromatic polyester resins or polyarylates are a combination of bisphenol A with isophthahe acid or terephthahe acid (79). The resins are made commercially by solution polymerization or melt transesterification (47). 

During the period of boiling in acid solution a small amount of polymeric material forms, and this is separated when the charcoal is removed by filtration. 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials Corrosive, particularly when diluted. Attacks most common metals, including most stainless steels. Excellent solvent for many synthetic resins or rubber Stability During Transport Stable Neutralizing Agents for Acids and Caustics Dilute with water, rinse with sodium bicarbonate solution Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

---