Retained solvents

Lamination Inks. This class of ink is a specialized group. In addition to conforming to the constraints described for flexo and gravure inks, these inks must not interfere with the bond formed when two or more films, eg, polypropylene and polyethylene, are joined with the use of an adhesive in order to obtain a stmcture that provides resistance properties not found in a single film. Laminations are commonly used for food applications such as candy and food wrappers. Resins used to make this type of ink caimot, therefore, exhibit any tendency to retain solvent vapor after the print has dried. Residual solvent would contaminate the packaged product making the product unsalable. 

Charcoal Tubes Reference has been made earlier to adsorption, which is the property of some solid materials, such as activated charcoal, to physically retain solvent vapors on their surfaces. In environmental health testing, the adsorbed vapors are removed, generally with a solvent, in a laboratory. The solvent is then analyzed by physical methods (gas chromatography, etc.) to determine the individual compounds whose vapors, such as benzene, were present in the sampled air. Industrial atmospheric samples can be collected in small glass tubes (4 mm ID) packed with two sections of activated charcoal, separated and retained with fiberglass plugs. To obtain an air sample, the sealed ends of the tube are broken off, and air is drawn through the charcoal at the rate of 1 liter per minute by means... 

Solvent (gm) H2 (psig) Corrected Solubility (%, daf) Total Retained Solvents (gm/ gm coal organics)... 

The checkers product retained solvent. The product was heated for a short period at 120° (20 mm.) and a crystalline solid, free of solvent, was obtained. 

It is interesting that tris-acetylacetonato-Yb(III)-monohydrate tends to retain solvent molecules. Thus if Yb(acac)3 3HaO is recrystaUized from acetone or benzene, one molecule of the solvent is present for two molecules of Yb(acac)3 H2O. The hemibenzene solvated Yb(acac)3 of composition [Yb(acac)3 H2O O.bCeHs] also crystallizes in triclinic space group PT, hke the unsolvated complex, with a =8.728, 6 = 8.435, c = 15.623 A, and a = 95.95°, /S = 107.72° and y =96.18° but with two formula units per unit cell (84). 

As far as the practical work-up procedure is concerned, the adducts possess many of the physical and chemical properties typical of air-sensitive compounds. However, because all the adducts tenaciously retain solvent molecules, which can prove troublesome in elemental analyses and in 13C NMR, it is worth outlining a procedure, found highly useful by the authors, which circumvents the problem ... 

Adducts of alkali metal salts prepared in anhydrous alcoholic media generally retain very little alcohol of solvation after being dried under vacuum at room temperature (see Table I). The unusual ability of adducts of D-glucitol to retain alcohol is probably due largely to the great ability of D-glucitol itself to retain solvent. Adducts of alkaline-earth metal salts, however, are more strongly solvated by alcohol than adducts of alkali metal salts. For example,21 lactose CaClj 4 MeOH is relatively stable at 60° at atmospheric pressure under vacuum (< 19 mm. of Hg), a molecule releases only two of the four molecules of methanol. From aqueous alcoholic media, adducts of alkaline-earth metal salts tend to crystallize as hydrates. 

Dielectric monitoring has been used to determine the optimum time at which pressure can be applied on adhesives and composites that are very pressure-dependent. This is especially important for films and prepregs that have a high degree of retained solvent. Optimum pressure should not be applied until the solvent has had a chance to escape the adhesive when it is in the liquid state. Pressure is then applied when the solvent has escaped and the viscosity of the adhesive is high enough to prevent squeeze-out from the joint. 

VAN DEVENTER D and MALLiKARJUNAN P (2002), Comparative performance analysis of three electronic nose systems using different sensor technologies in odor analysis of retained solvents on printed packaging , J Food Sci, 67(8), 3170-3183. 

GC has been the method of choice for drug analysis for many years however, with the advances in HPLC, GC is utilized less often. It is still used for the analysis of retained solvents, such as the USP test for volatile organic solvents. 

Ergotaminine [639-81-6] M 581,7, m 241-243 , [a]p +369 (c 0.5, CHCI3). It forms rhombic plates from MeOH which retain solvent unlike its isomer ergotamine (previous entry). It is less soluble than ergotamine, and its solubility is 0.1% in boiling ethanol and 0.07% in methanol. [Stoll Helv Chim Acta 28 1299 and 1306 1945, Beilstein 25 II 860, 862,25 III/IV 966.]... 

A third method was tried that gave undesirable results. The initiator and monomer were dissolved in tetrahydrofuran, a common solvent. In attempting to strip off the THF in a roto-vac at room temperature, it was found that polymerization of the BA-DAB-BA was initiated and advanced, even while there was still retained solvent. Since these factors contribute to processing difficulties and undesirable porosity in cured specimens, this method was discarded, and the methanol precipitation method was selected. 

These polymers all retained solvents very strongly, which made the elemental analysis extremely unreliable as a guide to polymer structure. For example, the polymer from diallylaminoethylpyridine (VII) contained more than 6% chlorine even after vacuum drying at room temperature for 48 hr. This could only be reduced below 1% by prolonged vacuum treatment at 60°C, conditions under which polymer decomposition occurred. 

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