Isocyanate, silicon

On the other hand, the PU wastes represent a real value because in their composition there are extremely valuable petrochemical materials (e.g., oligo-polyols, isocyanates, silicon emulsifiers, flame retardants and so on) and for the formation of these petrochemical materials an appreciable quantity of energy was consumed. These ecological and economic reasons led to a very intensive research effort, to find a solution to render value to these valuable materials PU wastes. The scope of the recycling technologies described is to recover as much as possible of the materials and energy resources invested in the PU material. 

Manufacturers Comments Contains no solvent, isocyanate, silicones Manufecturers Comments Fast drying, high tack. ... 

Formulations for one-shot polyether systems are similar to those used for flexible foams and contain polyether, isocyanate, catalyst, surfactant and water. Trichloroethyl phosphate is also often used as a flame retardant. As with polyesters, diphenylmethane di-isocyanate is usually preferred to TDI because of its lower volatility. Tertiary amines and organo-tin catalysts are used as with the flexible foams but not necessarily in combination. Silicone oil surfactants are again found to be good foam stabilisers. Volatile liquids such as trichlorofluoro-methane have been widely used as supplementary blowing agents and give products of low density and of very low thermal conductivity. 

Another major use of organotin compounds is as curing agents for the room temperature vulcanization of silicones the 3 most commonly used compounds are Bu2SnX2, where X is acetate, 2-ethylhexanoate or laurate. The same compounds are also used to catalyse the addition of alcohols to isocyanates to produce polyurethanes. 

Addition, chloroform, to olefins to form 1,1,3 tnchloroalkanes, 46, 106 chlorosulfonyl isocyanate to isobutylene to give 0-isovaleiolactam-N-sulfonyl chloride, 46, SI cyclohexyl amine to silicon tetraiso-cyanate, 46, 69... 

Polymerisation resulting from a chemical reaction involving condensation. The synthetic elastomers produced by condensation polymerisation include polysulphide rubbers, silicone rubbers and the ester and isocyanate rubbers. 

Exchange reactions in volatile isocyanates and isothiocyanates of silicon,... 

Saka and Yakake (1993) chemically modified wood samples with 3-isocyanatopropyl-triethoxysilane (IPTES) (Figure 7.9c). Wood was impregnated with acetone solutions of IPTES of different concentrations. Where the wood had been pre-swollen by treating with pyridine vaponr, a maximnm WPG of 27 % was obtained, whereas without pre-swelling of the cell wall a WPG of only 7 % was obtained. Pyridine also serves as a catalyst for the reaction of isocyanate with wood. SEM-EDXA showed the presence of silicon in the cell walls of the treated wood. Becanse of the lower WPG obtained without cell wall swelling, ASEs of the order of 20 % were obtained, compared to about 60 % when swelling of the cell wall was used prior to reaction. 

Catalytic amounts of 35 (1 mol%) also promoted the reaction of aromatic aldehydes with silyl ethers [94], vinylogous silicon enolates [95] and even with isocyanates in the presence of stoichiometric amount of SiCl [98]. The products were isolated in high yield and enantioselectivity. 

De Mello et al. have constructed a so-called pSYNTAS (miniaturized synthesis and total analysis system). The system was used to perform an Ugi-type reaction to form several a-aminoacetamides from amines, isocyanates and formaldehyde in the presence of water (Scheme 25) [56-58]. The reported system consists of a glass/silicon nanoreactor [59] in connection to a TOF-MS for the real-time online analysis of the reaction stream. Reactions were conducted in the 600 nl volume chip under continuous flow of 20-2 pl/min flow rate. Reduced flow rates resulted in increased outputs. The analyzed outlet flow showed high yields of the desired products with small quantities of starting materials and intermediates (no exact yields were reported). 

The fillers used in urethane formulations are similar to those used in silicones calcium carbonate, talc, days, and silica are among the most common. On account of the undesirable reaction of isocyanates with water, fillers used in urethane formulations must be dry. 

Braatz et al.- studied the adsorption of proteins on polyurethane surfaces. They coated silica and silicone tubing with a variety of chemistries. Although they found differences, the polyuretlianes demonstrated minimal protein adsorption given sufficient coating thickness. Correlations between the relative number of hard (isocyanate) and soft (glycol) segments were drawn. More soft segments resulted in less adsorption. 

When a toluene solution of a mixture of cyclotrisilane 34 and cyclohexyl isocyanate (or f-butyl isocyante) was heated at 70 °C, cyclic di- and trisiloxanes 37 and 38, i.e. the cyclic dimer and trimer of the silanone 36, were obtained together with the corresponding isonitrile RN=C. The formation of 37 as well as 38 was completely suppressed in the presence of hexamethylcyclotrisiloxane (19 D3) instead, quantitative conversion of 35 into 39, the formal insertion product of the silanone 36 into the Si—O bond of D3, occurred (Scheme 14). Since neither cyclodisiloxane 37 nor cyclotrisiloxane 38 reacted with D3 under the reaction conditions, the possibility that 37 or 38 is the precursor of 39 was ruled out. Whereas the oxidation of 35 with cyclohexyl and t-butyl isocyanates proceeded with exclusive formation of 37 and 38 (as the silicon-containing compounds) the reaction of 35 with phenyl isocyanate resulted in the formation of 37 in low yield. Furthermore, in this case the presence of D3 did not totally suppress the formation of 37. According to the authors, these results indicate that the oxidation of 35 with cyclohexyl and f-butyl isocyanates appears to use other reaction channels than that with phenyl isocyanate. 

The most recent developments are water-based dispersions of PEEVE,81 some of them cross-linkable with waterborne isocyanates.82 Another FEVE-based polymer, developed and commercialized recently by Asahi Glass Co. Ltd., has trade name LUMISEAL and is used for high-performance sealants, similar to silicone sealants with the advantage of eliminating the staining problem associated with the latter.83... 

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