Hydroxyl value phthalic anhydride

International Organization for Standardization, Nonionic surface active agents— polyalkoxy-lated derivatives—determination of hydroxyl value—phthalic anhydride method, ISO 4327 1979. Geneva, Switzerland. 

As previously discussed, solvents that dissolve cellulose by derivatization may be employed for further functionahzation, e.g., esterification. Thus, cellulose has been dissolved in paraformaldehyde/DMSO and esterified, e.g., by acetic, butyric, and phthalic anhydride, as well as by unsaturated methacrylic and maleic anhydride, in the presence of pyridine, or an acetate catalyst. DS values from 0.2 to 2.0 were obtained, being higher, 2.5 for cellulose acetate. H and NMR spectroscopy have indicated that the hydroxyl group of the methy-lol chains are preferably esterified with the anhydrides. Treatment of celliflose with this solvent system, at 90 °C, with methylene diacetate or ethylene diacetate, in the presence of potassium acetate, led to cellulose acetate with a DS of 1.5. Interestingly, the reaction with acetyl chloride or activated acid is less convenient DMAc or DMF can be substituted for DMSO [215-219]. In another set of experiments, polymer with high o -celliflose content was esterified with trimethylacetic anhydride, 1,2,4-benzenetricarboylic anhydride, trimellitic anhydride, phthalic anhydride, and a pyridine catalyst. The esters were isolated after 8h of reaction at 80-100°C, or Ih at room temperature (trimellitic anhydride). These are versatile compounds with interesting elastomeric and thermoplastic properties, and can be cast as films and membranes [220]. 

Examination of a number of alkyds, with formulations typical of the range in common use, showed that the measured hydroxyl value corresponded to the theoretical figure only when the system had a functionality of two. In connection with the availability of the hydroxyl groups, Kienle et al. [211 could not explain the glycerol-phthalic anhydride reaction by simple second- or third-order equations, whereas in fatty acid-modified polyester Wekna and Klausch [22] and Berg-mann [23] claim second-order kinetics apply. 

Solomon and Hopwood [24] find that, in the case of alkyd prepared from fatty acid, glycerol, and phthalic anhydride in the molar ratio 1.0 1.26 1.11, the measured hydroxyl values are considerably less than the calculated figures and the difference between these values increases with the molecular weight and the complexity of the polymer molecule. The difficulties encountered in the kinetic analysis of the formation of alkyd resins could be related, at least in part, to the availability of the hydroxyl group. 

Plots of dT (defined as the height of the recorder deflection) against hydroxyl value (determined by the conventional phthalic anhydride method) for five glycerol -propylene oxide condensates ranging in molecular weight between 300 and 4000 pass very near to the origin. 

Chen and Liu (14) coupled low-molecular-weight (number average values of 106 to 1000) polyoxyethylenes with 5-sulfo-isophthalic acid dimethyl ester sodium salt by condensing methanol from the molecules and forming the corresponding hydroxyl-terminated, ester-linked polyethers. These compounds were then reacted with phthalic anhydride by means of addition and condensation reactions to form water-soluble, polyester-linked poly(ethylene oxide)s with molecular weights between 6000 and 9000. The products had excellent surface-active properties, as well as excellent dispersant properties for disperse dyestuffs. 

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