Tin octoate catalyst

The actual chemistry involved in making the foams is very complex and involves several molecular weight PDMS reactants in addition to cross-linking agents and tin octoate catalyst. Another example of a chemically blown foam... 

A typical condensation system involves the reaction of a silanol-terminated polydimethylsiloxane with a multi-functional organosilicon cross-linking agent such as Si(RO)4 Figure 29.8). Pot life will vary from a few minutes to several hours, depending on the catalysts used and the ambient conditions. Typical catalysts include tin octoate and dibutyl tin dilaurate. 

Figure 7. Surface concentration (Cs) of the hydroxyl groups phenylurethanated with and without tin octoate for cellulose films (O) Visking without catalyst (0) cellophane with tin octoate...

It is also seen that when phenylurethanation is carried out at 30°C with the use of tin octoate as catalyst, the reaction proceeds with a higher rate than that without catalyst in spite of lower temperature, but the products show a similar saturated level of urethanation. 

Currently, tin(II) bis-(2-ethyUiexanoate), also referred as tin octoate, is the most widely used catalyst for the ROP of lactones. This popularity stems from its acceptance by the American Food and Drug Administration (FDA) for the formulation of polymer coatings in contact with food. Moreover, tin(II) bis-(2-ethyUiexanoate) is less sensitivity towards water and other protic impurities than aluminum alkoxides, which facilitates its use in the laboratory and in industry. 

For selectiveness of initiation of graft reactions, the use of a tin octoate (SnOct2) (or tin(II) 2-ethylhexanoate) catalyst is convenient for preparing this type of copolymers, polysaccharide-gra/f-PHAs, because the ring-opening polymerization of cyclic esters such as lactides and e-caprolactone (CL) can be initiated efficiently by hydroxo-initiators (i.e. based on hydroxyl groups) in the presence of SnOct2 [12-16], as exemplified in Scheme la. 

Silanol-silane reaction. A is removal of H B is Si-O-Si crosslinked polymer tin octoate is the catalyst. 

EINECS 206-108-6 2-Ethylhexanoic acid tin(2-<-) salt Metacure T-9 NSC 75857 Nuocure 28 Stannous 2-ethylhexanoate Stannous 2-ethylhexoate Stannous octoate Tin 2-ethylhexanoate Tin bis(2-ethylhexanoate) Tin diocloate Tin ethylhexanoate Tin octoate Tin(2-r) 2-ethylhexanoate Tin(ll) 2-ethylhexanoate Tin(ll) 2-ethylhexylate Tin(ll) bis(2-ethylhexanoate). Catalyst used in production of PU coatings, adhesives, and sealants uniform activity and excellent stability. Arr Products Chemicals Inc. 

Two-component RTV formulations involve separate packages for the polysiloxane and cross-linking agent. A typical two-component RTV formulation cures by reaction of silanol end groups with silicate esters in the presence of a catalyst such as tin octoate or dibutyltin dilaurate (Figure 4.38). 

Lactide is produced by degradation reactions, mainly via intramolecular chain scission of the prepolymer. Lactide synthesis from a prepolymer with a DP in the range of 10-15 in the presence of various catalysts at 4-5 mbar and 190-245°C is reported by Noda and Okuyama [9]. The best performances were reported using 0.05-0.2 wt% tin catalysts and tin octoate (stannous 2-ethylhexanoate) in particular, which is widely available. The catalyst increases the rate of backbiting reactions from hydroxyl chain ends of prepolymers to form lactide molecules [9, 15]. The melt viscosity of the prepolymer increases because of the esterification reactions during the process, which results in decreased rate of mass transfer. 

Despite the fact that the metal ions enable to control the polymerisation, they also pose an important downside as the formed polymers will always contain metal residues. These metal ions might have detrimental health effects. Aluminium derivatives have already been linked to Alzheimer s disease, although this hypothesis is controversial [50], while tin octoate, despite being FDA approved, has already been shown to be cytotoxic. As tin levels often exceed 1000 ppm, the FDA has set a limit of 20 ppm for polyesters used for biomedical applications [51]. To circumvent this problem, attention has already been paid to less toxic catalysts including magnesium and calcium alkoxides. Conversely, attempts are being made to remove the catalyst residues from the polymer. 

Poly(lactic acid)s can be synthesized by two methods (i) polyeondensation of lactic acids and (ii) ROP of LAs [1, 3, 8, 54, 55], Figure 8.3 shows the synthesis of PLLA, PDLA, and their block copolymers [11], Tin-based catalysts such as tin (II or IV) chloride and tin (II) bis-2-ethyUiexanoic acid (stannous octoate or tin octoate) were reported to effectively increase the molecular weight of the resulting PLAs up to an order of 10 and 10 g mol for polyeondensation [56,57] and ROP [58-61], respectively. Moreover, bulk polymerization in the presence of these catalysts aids in avoiding racemization and transesterification during the ROP of LA. 

The establishment of the equilibrium is often accelerated by acidic or basic catalysts, for example, by strong acids (p-toluenesulfonic acid), metal oxides (antimony trioxide), Lewis acids (titanium tetrabutoxide, tin acetates or tin octoates), weak acid salts of alkali metals or alkaline earth metals (acetates, benzoates), or by alcoholates. 

Basic Research on Batch Lactide Synthesis and the Catalysts Used Noda and Okuyama reported on the batch synthesis of lactide from DP 15 prepolymer with various catalysts at 4—5 mbar and 190-245°C [74]. In a batch synthesis with 50 g of oligomer in a stirred flask, the evolution rate of crude lactide is rather constant and then starts to dechne and the conversion levels off at 80-90%. The tin catalyst performed best compared to other catalysts and showed the lowest levels of racemization. Tin octoate... 

In a nutshell, the total hydroxyl content, including R-OH initiator and lactic acid impurities, determines the maximum attainable (number-average molecular weight) [4, 6]. The rate of polymerization is controlled by factors such as temperature and catalyst content, with the remark that a tin (II) octoate catalyst requires traces of the initiator to become active. 

Lactide polymerization with the addition of tin octoate is proposed via the coordination—insertion mechanism, as shown in Figure 2.10 (Henton, et al., 2005). The tin catalyst initiates the ring-opening reaction by attacking the nearest double-bond oxygen of the lactide. The hydroxyl and nucleophilic species simultaneously react with the ring-opened radical and finally... 

Among the coordination insertion catalysts, tin 2-ethylhexanoate (tin octoate, or Sn(Oct)2) is the most widely used and studied due to its ability to produce highly crystalline PLA in relatively short periods of time with high conversion and low racemization up to 180°C. It has also been approved by the United States Food and Drug Administration for food contact (16), making it ideal for many packaging applications. 

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