Partial Hydrolyzates

If we consider an open polypeptide chain consisting of N residues, complete hydrolysis will give rise to N amino acids, many of which may 

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Chlorine is soluble in water and in salt solutions, the solubihty decreasing with salt strength and temperature (see Fig. 34). It is partially hydrolyzed in aqueous solution as... 

Esters. The mono- and diesters of glycerol and fatty acids occur naturally ia fats that have become partially hydrolyzed. The triglycerides are primary components of aaturaHy occurring fats and fatty oils. 

The most commonly used polymers are partially hydrolyzed polyacrylamides (32). The optimum degree of hydrolysis depends on the apphcation, injection water composition, and reservoir conditions (33,34). More salt-tolerant acrylamide copolymers may permit this technology in higher salinity injection water (35). Eield apphcations of cross-linked xanthan gum have also been reported (36). 

Copolymers of sodium acrylate with sodium 2-acrylamido-2-methylpropane sulfonate (AMPS) or /V, /V- dim ethyl acryl am i de (52) have been used to prepare cross-linked systems at high temperatures and salinity. Chromium cross-linked gels, prepared from a 3 1 blend of partially hydrolyzed... 

Pyrotechnic mixtures may also contain additional components that are added to modify the bum rate, enhance the pyrotechnic effect, or serve as a binder to maintain the homogeneity of the blended mixture and provide mechanical strength when the composition is pressed or consoHdated into a tube or other container. These additional components may also function as oxidizers or fuels in the composition, and it can be anticipated that the heat output, bum rate, and ignition sensitivity may all be affected by the addition of another component to a pyrotechnic composition. An example of an additional component is the use of a catalyst, such as iron oxide, to enhance the decomposition rate of ammonium perchlorate. Diatomaceous earth or coarse sawdust may be used to slow up the bum rate of a composition, or magnesium carbonate (an acid neutralizer) may be added to help stabilize mixtures that contain an acid-sensitive component such as potassium chlorate. Binders include such materials as dextrin (partially hydrolyzed starch), various gums, and assorted polymers such as poly(vinyl alcohol), epoxies, and polyesters. Polybutadiene mbber binders are widely used as fuels and binders in the soHd propellant industry. The production of colored flames is enhanced by the presence of chlorine atoms in the pyrotechnic flame, so chlorine donors such as poly(vinyl chloride) or chlorinated mbber are often added to color-producing compositions, where they also serve as fuels. 

Expect some product contamination if feed components can react with water, eg, ester will be partially hydrolyzed to acid and alcohol fate of reaction product species depends on above rules, eg, methanol from methyl ester hydrolysis probably not stripped out of bottoms stream. 

Com symps [8029-43 ] (glucose symp, starch symp) are concentrated solutions of partially hydrolyzed starch containing dextrose, maltose, and higher molecular weight saccharides. In the United States, com symps are produced from com starch by acid and enzyme processes. Other starch sources such as wheat, rice, potato, and tapioca are used elsewhere depending on avadabiHty. Symps are generally sold in the form of viscous Hquid products and vary in physical properties, eg, viscosity, humectancy, hygroscopicity, sweetness, and fermentabiHty. 

Partially hydrolyzed products of the form RSn(OH)2Cl are beHeved to be mixtures in most cases. 

Solubility. Poly(vinyl alcohol) is only soluble in highly polar solvents, such as water, dimethyl sulfoxide, acetamide, glycols, and dimethylformamide. The solubiUty in water is a function of degree of polymerization (DP) and hydrolysis (Fig. 4). Fully hydrolyzed poly(vinyl alcohol) is only completely soluble in hot to boiling water. However, once in solution, it remains soluble even at room temperature. Partially hydrolyzed grades are soluble at room temperature, although grades with a hydrolysis of 70—80% are only soluble at water temperatures of 10—40°C. Above 40°C, the solution first becomes cloudy (cloud point), followed by precipitation of poly(vinyl alcohol). 

The hydroxyl groups in poly(vinyl alcohol) contribute to strong hydrogen bonding both intra- and intermolecularly, which reduces solubiUty in water. The presence of the residual acetate groups in partially hydrolyzed poly(vinyl alcohol) weakens these hydrogen bonds and allow solubiUty at lower temperatures. 

Adhesives. Poly(vinyl alcohol) is used as a component in a wide variety of general-purpose adhesives to bond ceUulosic materials, such as paper and paperboard, wood textiles, some metal foils, and porous ceramic surfaces, to each other. It is also an effective binder for pigments and other finely divided powders. Both fully and partially hydrolyzed grades are used. Sensitivity to water increases with decreasing degree of hydrolysis and the addition of plasticizer. Poly(vinyl alcohol) in many appHcations is employed as an additive to other polymer systems to improve the cohesive strength, film flexibiUty, moisture resistance, and other properties. It is incorporated into a wide variety of adhesives through its use as a protective coUoid in emulsion p olymerization. 

Partially hydrolyzed poly(vinyl alcohol) grades are preferred because they have a hydrophobic /hydrophilic balance that make them uniquely suited for emulsion polymerization. The compatibUity of the residual acetate units with the poly(vinyl acetate) latex particles partly explains the observed stabilization effect. The amount of PVA employed is normally 4—10% on the weight of vinyl acetate monomer. The viscosity of the resulting latex increases with increasing molecular weight and decreasing hydrolysis of the PVA (318). 

The fully and super hydrolyzed PVA grades are preferred by the paper industry for their superior strength, greater adhesion to cellulose, better water resistance, and better foaming characteristics. However, the intermediate and partially hydrolyzed grades provide better surface filming characteristics on many paper and paperboard substrates. 

Poly(vinyl alcohol) is used as an additive to dry-wall joint cements and stucco finish compounds. Rapid cold-water solubiUty, which can be achieved with finely ground PVA, is important in many dry mixed products. Partially hydrolyzed grades are commercially available in fine-particle size under the name S-grades. The main purpose of the poly(vinyl alcohol) is to improve adhesion and act as a water-retention aid. 

Partially hydrolyzed grades are used in many cosmetic appHcations for their emulsifying, thickening, and film-forming properties. Poly(vinyl alcohol) is also used as a viscosity builder for aqueous solutions and dispersions. 

Zirconium alkoxides readily hydrolyze to hydrous zirconia. However, when limited amounts of water are added to zirconium alkoxides, they partially hydrolyze in a variety of reactions depending on the particular alkoxide (222). Zirconium tetraisopropoxide [2171 -98-4] reacts with fatty acids to form carboxjiates (223), and with glycols to form mono- and diglycolates (224). 

Cellulose acetate [9004-35-7] is the most important organic ester because of its broad appHcation in fibers and plastics it is prepared in multi-ton quantities with degrees of substitution (DS) ranging from that of hydrolyzed, water-soluble monoacetates to those of fully substituted triacetate (Table 1). Soluble cellulose acetate was first prepared in 1865 by heating cotton and acetic anhydride at 180°C (1). Using sulfuric acid as a catalyst permitted preparation at lower temperatures (2), and later, partial hydrolysis of the triacetate gave an acetone-soluble cellulose acetate (3). The solubiUty of partially hydrolyzed (secondary) cellulose acetate in less expensive and less toxic solvents such as acetone aided substantially in its subsequent commercial development. 

The most important reaction with Lewis acids such as boron trifluoride etherate is polymerization (Scheme 30) (72MI50601). Other Lewis acids have been used SnCL, Bu 2A1C1, Bu sAl, Et2Zn, SO3, PFs, TiCU, AICI3, Pd(II) and Pt(II) salts. Trialkylaluminum, dialkylzinc and other alkyl metal initiators may partially hydrolyze to catalyze the polymerization by an anionic mechanism rather than the cationic one illustrated in Scheme 30. Cyclic dimers and trimers are often products of cationic polymerization reactions, and desulfurization of the monomer may occur. Polymerization of optically active thiiranes yields optically active polymers (75MI50600). 

When PMMA was adsorbed onto an iron substrate, four components were not sufficient to explain the C(ls) spectrum (see Fig. 21b) and a fifth component had to be added at 288.1 eV as shown in Fig. 21c. This component was attributed to carboxyl groups, indicating that the ester groups were partially hydrolyzed. Similarly, Leadley and Watts found that there were five components in the C(ls) spectrum of PMMA spin-coated onto aluminum, copper, and nickel substrates 124]. 

In addition to polymer standards, a number of broad distribution, water-soluble polymers can be characterized on TSK-PW columns using universal calibration. These include both fully and partially hydrolyzed PVA, PAAM, PEE, and dextran. PVA, the world s largest-volume, synthetic, water-soluble polymer, was first successfully separated on TSK-PW columns by Hashimota et al. (10). In the 1980s, the use of low-angle, laser light-scattering detection... 

Molecular weights for fully hydrolyzed and partially hydrolyzed grades of PVA (expressed in terms of 4% solution viscosity) from aqueous SEC-MALLS are summarized in Table 20.6. M values range from less than 20,000 Da for a 3 centipoise (cP) viscosity grade to over 230,000 Da for a super-high viscosity... 

FIGURE 20.6 DRI chromatograms of partially hydrolyzed PVA (low molecular weight type) using TSK-PW columns. 

Heating 2,3-dinitroaeetanlllde (5) with sodium ethoxide in DMF gave a mixture of 2-methyl-7-nitro-benzoxazole (6) and 2-nitro-6-aeetamidophenol (7) (Eq. 4). The latter is also formed under the same eonditions from 6. Consequently, the probable meehanism of the reaetion Involves primarily the denitroeyelization reaetion leading to 6, whleh is then partially hydrolyzed to 7 (80KGS417). 

The polymerization of acrylamide in aqueous solutions in the presence of alkaline agents leads to the ob-tainment of partially hydrolyzed polyacrylamide. The polymerization process under the action of free radicals R (formed on the initiator decomposition) in the presence of OH ion formed on the dissociation of an alkali addition (NaOH, KOH, LiOH), and catalyzing the hydrolysis can be described by a simplified scheme (with Me = Na, K, Li) ... 

G.L. Griffith W.L. Schwoyer, USP 3457128 (1969) CA 71, 72517 (1969). Particulate self-explosive nitrated materials, such as Nitro-starch, PETN, TNT,.and their mixts, can be made relatively safe to handle and transport thru formation of a uniform nongelled aq slurry containing 10—50% water and 0.5—10% partially hydrolyzed polyacrylamide suspending agent having 0.1—50% free acid, and = 50% unhydrolyzed amide groups, and a mw of 1,000,GOO-... 

The reaction rate increased with temperature. The hydrolysis rate of AG at temperatures lower than 70 °C was very slow. At 80 °C, only complete release of arabinose was achieved, but partially hydrolyzed galactose residue was left. The conversion of AG was 43%. A complete conversion of AG to monomers was achieved at 90 and 100 °C. After the hydrolysis at 100 °C, traces of degradation products such as furfural were observed. For this reason, the temperature for AG hydrolysis shall not exceed 100 °C. 

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