Dibutyl tin oxide

Acetylsucrose [63648-81-7] has been prepared in 40% yield by direct acetylation of sucrose using acetic anhydride in pyridine at 40° C (36). The 6-ester has subsequently been obtained in greater than 90% yield, by way of 4,6-cycHc orthoacetate. Other selective methods for the 6-acylated derivatives include the use of alkyl tin reagents such as dibutyl tin oxide (37) and of dibutyl stannolane derivatives (38). Selective acetylation of sucrose by an enzymic process has also been described. Treatment of sucrose with isopropenyl acetate in pyridine in the presence of Lipase P Amano gave, after chromatography, 6-0-acetylsucrose (33%) and 4/6-di-O-acetylsucrose (8%). The latter compound has been obtained in 47% yield by the prolonged treatment (39). 

Cychc carbonates result from polyols by transesterification using organic carbonates (115). Thus sorbitol and diphenylcarbonate in the presence of dibutyl tin oxide at 140—150°C form sorbitol tricarbonate in quantitative yield (116). 

The polymetallosiloxanes above may in fact be considered as variants of a series of polymetalloxanes which are akin to the silicones but which contain, for example, tin, germanium and titanium instead of silicon. Of the poly-organostannoxanes, dibutyl tin oxide finds use as a stabiliser for PVC and as a silicone cross-linking agent. Polyorganogermanoxanes have also been prepared (Figure 29.13). 

Diazo aminobenzene Di-t-butyl-p-cresol Dibutyl tin maleate Dibutyl tin oxide Dichlorophene 2,4-Dichiorophenoxy ethyl benzoate... 

After reaching the desired DP, 40-50 % of the oligomeric melt is transferred to the polymerization vessel. Titanium butoxide (50-150 ppm) or dibutyl tin oxide catalyst (100-250 ppm), or some combinations of the two catalysts, is added to catalyze polymerization at 260-275 °C. A vacuum of <0.15 kPa is applied to remove the condensed water so as to drive the reaction until the polymer reaches an intrinsic viscosity (IV) of 0.7-0.9 dL/g. 

Indirect food additives Adhesives and components of coatings and polymers Dibutyl tin oxide, hydroxybutyl tin 177.2420... 

PETG (90-80) / EVAc (10-20) internal mixer at 210°C / SEM / NMR model study / rheology / DMA / interfacial tension measurements by breaking thread method / dibutyl tin oxide catalyst (0-1%) Lacroix et al., 1996 a, b... 

Hu and Lambla [1995] have blended EM Ac (90-65 parts) with mono-hydroxy-terminated PS (10-35 parts) in an internal mixer at 180-220°C in the presence of dibutyltin dilaurate or dibutyl-tin oxide catalyst. A compatibilizing copolymer arises from transesterification between pendent ester groups of EMAc and terminal hydroxy groups of PS. The effects on blend properties of PS molecular weight were reported. The effects of processing conditions and addition of solvent on conversion kinetics were studied. 

The PTT is aromatic polyester prepared by the melt polycondensation of 1,3-propanediol (1,3-PDO) with either TPA or dimethyl terephthalate (DMT). The PTT is synthesized by the transesterification of propanediol with dimethylene terephthalate or by the esterification of propane diol with TPA. The reaction is carried out in the presence of hot catalyst like titanimn butoxide (Ti(OBu) ) and dibutyl tin oxide (DBTO) at a temperature of 260°C. The important by-products of this reaction include acrolien and allyl alcohol (Chuah, 2001). Direct esterification of propane diol and TPA is considered as the least economic and industrial method. The reaction is carried out in the presence of a heel imder a pressure of 70-150 kPa at a temperature of 260°C. The heel is usually referred to the added PTT oligomers which act as a reaction mediiun and increase the solubility of TPA (Chuah, 2001). Recent studies by different groups show that the selection of the catalyst plays a major role on the reaction rate and PTT properties. Commonly used catalysts like titanium (Doerr et al., 1994), tin (Kurian and Liang, 2001 Fritz et al., 1969) and antimony (Karayannidis et al., 2003 Fitz et al., 2000) compounds have their own limitations. Titanimn-based catalysts are active but the PTT is discolored, antimony-based catalysts are toxic and only active in polycondensation while tin-based compounds have lower catalytic activity. Karayannidis and co-workers (2003) reported the use of stannous oetoate ([CHj(CH2)3CH(C2Hj)COO]jSn) as the catalyst for PTT synthesis but its catalytic activity is poor, resulting in a low molecular weight PTT which was confirmed... 

Table 1 indicates the rate constants (k k2> and activation energies (E E2) for zinc acetate and dibutyl tin oxide catalyzed reactions for PBT 50 and HQDA + TA 50 mole% concentration. The values of kl are found to be the range of 0.03136 to 0.5 kJ/mole while for k2 it is in the range of 0.004 to 0.1 kJ/mole. No major decrease in the value of the rate constants ki and k2 ate noticed. The activation energy values indicate that DBTO at 0.25 mole% concentration is a suitable catalyst for the PBT 50 mole% concentration. 

Figure 2 Second order plot of 0.25 mole% dibutyle tin oxide catalyzed reaction for PBT (30%) and (HQDA+TA) (70%) with the model...

Figure 4 Arrhenius plots for uncatalyzed and dibutyl tin oxide catalyzed reaction for 50 mole% PBT...

PTT is melt-polymerized by either the transesterification of PDO with DMT or by the direct esterification of PDO with TPA. The process is similar to the polymerization of PET but with several important differences. Since the reactivity of PDO is much lower than that of ethylene glycol, hot catalysts such as titanium butoxide (12) and dibutyl tin oxide (13), normally too fast for PET, are used to polymerize PTT. Melt polymerization is carried out between 250 and 275°C, about 40° C lower than that used for PET. PTT has different polymerization side reaction products. Instead of cyclic trimers, PTT produces cyclic dimers. It also gives off acrolein and allyl alcohol instead of acetaldehyde gaseous by-products. Acrolein requires special handling and disposal. 

Direct esterification of PDO with TPA is the preferred commercial route to polymerize PTT because it is more economical than using DMT. Figure 1 shows the reaction scheme. Because TPA has a melting point > 300°C and has poor solubility in PDO, esterification is carried out in the presence of a heel and imder a pressure of 70-150 kPa at 250-270°C for 100-140 min. Heel is an oligomeric PTT melt with a degree of polymerization (DP) of 3-7 purposely left in the reaction vessel from a previous reaction to act as a reaction medium and to increase TPA solubility. The esterification step is self-catalyzed by TPA. After reaching a DP of about 3-7, 40-50% of the oligomers is transferred to the polymerization vessel. Titanium butoxide or dibutyl tin oxide catalyst (50-150 ppm) is added to initiate polymerization at 260-275°C. Vacuum (<0.15 kPa) is applied to remove the condensed water until the polymer reaches an intrinsic viscosity (IV) of 0.7-0.9 dL/g. 

Lead dioxide has traditionally been the preferred curing agent, but it cannot be used in white or light-tint compositions. Other curing agents which have been used are manganese dioxide, tellurium oxide, barium peroxide, calcium peroxide, zinc peroxide, and dibutyl tin oxide. Silane adhesion promoters are often utilized in polysulfide sealants. ... 

In 1993, Miura and co-workers studied the use of organotin-alkyl phosphate condensates derived from dibutyl-tin oxide and tributyl phosphate to catalyze the polymerization of propylene oxide (Figure 4). They observed that the polymeric product could be fractionated into benzene-hexane soluble and insoluble fractions. On studying the stereoerrors of the product by NMR, they determined that the insoluble... 

Figure 5.8 (a) HPLC trace of cyclic PBT oligomers from a solution ring-chain reaction in 1,2-dichlorobenzene with dibutyl tin oxide as catalyst and (b) HPLC trace of cyclic PBT oligomers extracted from chip with mixed xylene... 

---