Dibutyltin system

The unblocking temperature usually refers to the temperature at which the blocked urethane system must be heated for 30 min in order to achieve cure. The reaction can be accelerated by curing at higher temperatures and/or by the addition of catalyst, as shown in Fig. 6 [62]. Common urethane catalysts like dibutyltin dilaurate are known to decrease the unblocking temperature. 

Figures 20.13 and 20.14 describe the effect of dibutyltin dilaurate (DBTDL) on the tensile strength and tensile modulus for the 25/75 LCP/PEN blend fibers at draw ratios of 10 and 20 [13]. As expected, the addition of DBTDL slightly enhances the mechanical properties of the blends up to ca. 500 ppm of DBTDL. The optimum quantity of DBTDL seems to be about 500 ppm at a draw ratio of 20. However, the mechanical properties deteriorate when the concentration of catalyst exceeds this optimum level. From the previous relationships between the rheological properties and the mechanical properties, it can be discerned that the interfacial adhesion and the compatibility between the two phases, PEN and LCP, were enhanced. Hence, DBTDL can be used as a catalyst to achieve reactive compatibility in this blend system. This suggests the possibility of improving the interfacial adhesion between the immiscible polymer blends containing the LCP by reactive extrusion processing with a very short residence time.

Figure 15 illustrates the effect of a 45-minute dwell time on two plastisols containing 75 p.h.r. of DOP with different stabilizer systems. The upper example is a liquid cadmium-barium system and the lower a thiotin-dibutyltin maleate system. The organotin system is obviously the more effective. The leading yellow zone, which is followed by a dark zone, may indicate two different breakdown mechanisms. 

Metal chelates of 8-hydroxyquinoline such as (111) with photoconductive properties are reported to be useful in electrophotographic systems.233 The incorporation of a tin complex into a photo-conductive zinc oxide layer is stated to reduce dark decay . In other words, the electrostatic charge applied to the photoconductor has a longer lifetime. Two of the complexes disclosed for this application are (112) and (113). These compounds are prepared from dibutyltin oxide by reaction with 2-mercaptopropionic add and thioglycolic acid, respectively 234... 

Inflammatory changes consisting of hyperemia and bronchitis were observed in the respiratory system of rabbits exposed to 4-6 mg/m (0.30-0.45 ppm) tributyltin chloride for 95 days (Gohlke et al. 1969). Histopathology, consisting of severe bronchitis and vascular and alveolar edema, was seen in rats exposed to 2 mg tin/m (0.41 ppm) as a mixture of tributyltin dibromide (0.39 ppm), dibutyltin bromide (0.02 ppm) and hydrocarbon impurities for 80 days (Iwamoto 1960). Since these were terminal histopathological evaluations only, it is not known whether the changes were reversible or would have produced functional impairment in the animals if exposure had continued. 

The system of Eqs. 13.3-17 and 13.3-18 can be solved for the adiabatic, isothermal, or constant wall flux cases using the Crank-Nicolson method. The thermomechanical and reaction data for such systems were evaluated by Lifsitz, Macosko, and Mussatti (99) at 45°C for a polyester triol and a chain extended 1,6-hexamethylene diisocyanate (HDI) with dibutyltin as a catalyst. Figure 13.46 gives the temperature profiles for the isothermal-wall case. Because of the high heat of polyurethane formation and the low conductivity of... 

OTCs have severe effects on the immune systems, causing premature atrophy of thymus gland and lymphoid tissues as well as inhibition of spleen cell activity. Inhibition of phagocytosis and cytolysis of polymorphonuclear leukocytes with resultant depression of cell-mediated immune responses have also been demonstrated21-37. The influence of the thymus atrophy-inducing dibutyltin dichloride Bu2SnCl2 on the differentiation and proliferation of immature rat thymocyte subsets were studied in vivo and in vitro. The atrophy results from a depletion of small CD4+CD8+ thymocytes which is caused by a diminished production of immature CD4+CD8+ and CD4+CD8+ thymoblasts. Dibutyltin dichloride inhibits the activation, but not the differentiation of immature CD4+CD8+ thymocytes in vivo and in vitro, suggesting a selective antiproliferative activity of this compound. It also... 

PSA Formulation and Properties. The formulations used in this study for the Hycar 2103-Prepolymer C and Hycar 2106-Prepolymer C PSA contain OH/NCO ratios of 1.7 and 1.3, respectively. Dibutyltin dilaurate catalyst is used at a 0.2 wt.% level based on the total adhesive solids. PSA samples are made from an 80% solids solution (by wt.) with a dry solvent system (27/73 by wt. of ethyl acetate-toluene) and cured at 150°C for 45 seconds. The samples are then evaluated by running 180° peel, static shear, rolling ball tack, and vinyl film shrinkage tests. 

The IPNs prepared were composed of a rubbery polyurethane and a glassy epoxy component. For the polyurethane portion, a carbodiimide-modified diphenyl-methane diisocyanate (Isonate 143L) was used with a polycaprolactone glycol (TONE polyol 0230) and a dibutyltin dilaurate catalyst (T-12). For the epoxy, a bisphenol-A epichlorohydrin (DER 330) was used with a Lewis acid catalyst system (BF -etherate). The catalysts crosslink via a ring-opening mechanism and were intentionally selected to provide minimum grafting with any of the polyurethane components. The urethane/epoxy ratio was maintained constant at 50/50. A number of fillers were included in the IPN formulations. The materials used are shown in Table I. 

The most important hydrogen bond donating group in directed epoxidations is the hydroxy group. For allylic or homoallylic alcohols, peracids or tert-butyl hydroperoxide/vanadylbis[2,4-pentanedionate] (see Houben-Weyl, Vol. IV/la, p 231) are generally the most efficient reagent systems less common catalysts are tri-te/ f-butoxyaluminum, dibutyltin oxide, and molybdenum- and titanium-based systems (see Houben-Weyl, Vol. IV/la, p 227, Vol. E13/2, p 1176). The two classes of reactions show distinct differences in their stereoselectivity patterns. 

Tertiary amines alone can be used as catalysts, but for some applications, such as spraying, more speed is desirable. Metal salts, particularly tin salts, accelerate the foaming reactions, and can be used alone or in combination with the tertiary amine-type catalysts. Tin catalysts of importance for rigid urethane foams are stannous octoate and dibutyltin dilaurate. Stannous octoate will hydrolyze rapidly in the presence of a basic catalyst with loss of activity. Masterbatches containing stannous octoate and moisture are stable for only a few hours at room temperature. Resin masterbatches containing dibutyltin dilaurate may stay stable for months. For this reason this catalyst is preferred for foaming systems packaged for use at other locations or plants where the resin masterbatch is not used immediately (20). 

In polycondensation systems, a poly(dimethylsiloxane) with hydroxy end-groups at either end and a viscosity of 10- to 10 mPa s is crosslinked with tetraalkoxysilanes, e.g. tetraethoxysilane, in the presence of a condensation-accelerating tin compound e.g. dibutyltin dilaurate. Since this hardening, in contrast with single component products, is not dependent upon water diffusion through the hardening mass, thick layers of such rubber systems can be crosslinked quickly and homogeneously. 

Dibutyltin dichloride (DBTC) is a widespread environmental pollutant that exhibits developmental toxicity in animals 19 and immunotoxic effects in human cells in vitroJ2°l No studies were found in the literature that compared the developmental and immunotoxic effects of DBTC alone to a mixture of DBTC and ethanol. One study, however, found that ethanol co-administered with DBTC increased the toxicity of DBTC in the liver and pancreas of laboratory animals both acutely and chronically. 21 An analysis of this study suggests that the combination of DBTC and ethanol might be expected to show enhanced toxic effects on other body organs and systems. 

Series II Unfilled PUs using various compatible polyol blends (PB) in which the code numbers in Table I represent in order the weight ratios of polyols T32/75, LHT240 and EG. A mixture of triethylene diamine and dibutyltin dilaurate was used as catalyst throughout. The various polyol-based reactants and derived RIM PUs are summarised in Table I, including isocyanate/hydroxyl ratios (multiplied by 100), expressed as the System Index. Thus, 1001 represents stoichiometric equivalence, 1041 a 4% excess by weighted equivalents of isocyanate and 971 a 3% excess of hydroxyl. 

Our attention turned next to a widely used type of commercial stabilizer, dibutyltin di-isooctylthioglycolate. The ligand exchange reaction in the dibutyltin di-isooctylthiogylcolate/dibutyltin dichloride system was studied by both JH and 18C NMR. In the experiments the resonance of the methylene group in the thioglycolate moiety (-S-CH2-COO-) was used to follow the reaction. When Compounds 7 and S (Table III, Experiments 6, 7, and 8) were mixed at 25°C in deutero-... 

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