Octoates

The physical properties of polyurethane adhesives result from a special form of phase separation which occurs in the cross-linked polyurethane stmcture. The urethane portions of polyurethanes tend to separate from the polyol portion of the resin, providing good shear strength, good low temperature flexibiUty, and high peel strength. Catalysts such as dibutyltin dilaurate [77-58-7], stannous octoate [1912-83-0], l,4-diazabicyclo[2.2.2]octane... 

Toluhydroquinone and methyl / fX butyUiydroquinone provide improved resin color retention 2,5-di-/-butyIhydroquinone also moderates the cure rate of the resin. Quaternary ammonium compounds, such as benzyl trimethyl ammonium hydroxide, are effective stabilizers in combination with hydroquinones and also produce beneficial improvements in color when promoted with cobalt octoate. Copper naphthenate is an active stabilizer at levels of 10 ppm at higher levels (150 ppm) it infiuences the cure rate. Tertiary butylcatechol (TBC) is a popular stabilizer used by fabricators to adjust room temperature gelation characteristics. 

Catalyst Selection. The low resin viscosity and ambient temperature cure systems developed from peroxides have faciUtated the expansion of polyester resins on a commercial scale, using relatively simple fabrication techniques in open molds at ambient temperatures. The dominant catalyst systems used for ambient fabrication processes are based on metal (redox) promoters used in combination with hydroperoxides and peroxides commonly found in commercial MEKP and related perketones (13). Promoters such as styrene-soluble cobalt octoate undergo controlled reduction—oxidation (redox) reactions with MEKP that generate peroxy free radicals to initiate a controlled cross-linking reaction. 

Some fabrication processes, such as continuous panel processes, are mn at elevated temperatures to improve productivity. Dual-catalyst systems are commonly used to initiate a controlled rapid gel and then a fast cure to complete the cross-linking reaction. Cumene hydroperoxide initiated at 50°C with benzyl trimethyl ammonium hydroxide and copper naphthenate in combination with tert-huty octoate are preferred for panel products. Other heat-initiated catalysts, such as lauroyl peroxide and tert-huty perbenzoate, are optional systems. Eor higher temperature mol ding processes such as pultmsion or matched metal die mol ding at temperatures of 150°C, dual-catalyst systems are usually employed based on /-butyl perbenzoate and 2,5-dimethyl-2,5-di-2-ethyIhexanoylperoxy-hexane (Table 6). 

A number of different cobalt salts have been used in the oxidation of toluene, the most common being cobalt acetate [71-48-7] cobalt naphthenate, and cobalt octoate [1588-79-0],... 

Cd(C24H2g02)2, are of this type. Liquid stabilizers such as cadmium octoate [2191 -10-8] Cd(CgH2g02)2, cadmium phenolate [18991 -05A] Cd(CgHgO)2, cadmium decanoate [2847-16-7] Cd(C2QH2Q02)2, cadmium benzoate [3026-22-0] and cadmium naphthenate are more versatile and... 

Application. Polyesters are cured by free radicals, most commonly produced by the use of peroxides. A wide range of peroxide initiators (qv) are available for use in curing polyesters. Most peroxide initiators are thermally decomposed into free radicals, and the common initiators used at room temperature requke the use of a promoter such as dimethylaniline or cobalt octoate. 

A great variety of resia formulations is possible because other thermosets, such as epoxies or acrylates, and reactive diluents, such as o-diaUyl phthalate [131-17-9] triaUyl cyanurate [101-37-17, or triaUyl isocyanurate [1023-13-6J, can be used to further modify the BT resias. The concept is very flexible because bismaleimide and biscyanate can be blended and copolymerized ia almost every ratio. If bismaleimide is used as a major constituent, then homopolymerization of the excess bismaleimide takes place ia addition to the copolymerization. Catalysts such as ziac octoate or tertiary amines are recommended for cure. BT resias are mainly used ia ptinted circuit and multilayer boards (58). 

Octoates were the next drier development. Because these driers are produced from synthetic 2-ethylhexanoic acid, the chemical composition can be controlled and uniformity assured. Also, other synthetic acids, eg, isononanoic and neodecanoic, became available and are used for metal soap production. Compared to naphthenic acid, these synthetic acids have high acid values, are more uniform, lighter in color, and do not have its characteristic odor. It is also possible to produce metal soaps with much higher metal content by using synthetic acids. 

Other Octoate Uses. Metal octoates are also used as driers in printing inks. Another appHcation of octoates includes the use of the aluminum salt to gel paint. Stannous, dibutyltin, and bismuth carboxylates find appHcation as catalysts in polyurethane foam appHcations in order to obtain a reaction efficiency suitable for industrial production. In polyurethane foam manufacture the relative rate of polymeriza tion and gas foaming reactions must be controlled so that the setting of the polymer coincides with the maximum expansion of the foam. 

Whilst lead compounds have been, and still are, the most important class of stabiliser for PVC the metallic soaps or salts have steadily increased in their importance and they are now widely used. At one time a wide range of metal stearates, ricinoleates, palmitates and octoates were offered as possible stabilisers and the efficiency of many of them has been examined. Today only the compounds of cadmium, barium, calcium and zinc are prominent as PVC stabilisers. 

Somewhat better results have been obtained with octoates and benzoates but these still lead to some plate-out. The use of liquid cadmium-barium phenates has today largely resolved the problem of plate-out whilst the addition of a trace of a zinc salt helps to improve the colour. Greater clarity may often be obtained by the addition of a trace of stearic acid or stearyl alcohol. Thus a modem so-called cadmium-barium stabilising system may contain a large number of components. A typical packaged stabiliser could have the following composition ... 

Mention has already been made of epoxide stabilisers. They are of two classes and are rarely used alone. The first class are the epoxidised oils, which are commonly employed in conjunction with the cadmium-barium systems. The second class are the conventional bis-phenol A epoxide resins (see Chapter 22). Although rarely employed alone, used in conjunction with a trace of zinc octoate (2 parts resin, 0.1 part octoate) compounds may be produced with very good heat stability. 

More frequently either methyl ethyl ketone peroxide or cyclohexanone peroxide is used for room temperature curing in conjunction with a cobalt compound such as a naphthenate, octoate or other organic solvent-soluble soap. The peroxides (strictly speaking polymerisation initiators) are referred to as catalysts and the cobalt compound as an accelerator . Other curing systems have been devised but are seldom used. 

Cobalt naphthenate is generally supplied in solution in styrene, the solution commonly having a cobalt concentration of 0.5-1.0%. The cobalt solution is normally used in quantities of 0.5-4.0% based on the polyester. The accelerator solution is rather unstable as the styrene will tend to polymerise and thus although the accelerator may be metered from burettes, the latter will block up unless frequently cleaned. Cobalt naphthenate solutions in white spirit and dimethyl phthalate have proved unsatisfactory. In the first case dispersion is difficult and laminates remain highly coloured whilst with the latter inferior end-products are obtained and the solution is unstable. Stable solutions of cobalt octoate in dimethyl phthalate are possible and these are often preferred because they impart less colour to the laminate. 

In recent years there has been some substitution of TDI by MDI derivatives. One-shot polyether processes became feasible with the advent of sufficiently powerful catalysts. For many years tertiary amines had been used with both polyesters and the newer polyethers. Examples included alkyl morpholines and triethylamine. Catalysts such as triethylenediamine ( Dabco ) and 4-dimethyla-minopyridine were rather more powerful but not satisfactory on their own. In the late 1950s organo-tin catalysts such as dibutyl tin dilaurate and stannous octoate were found to be powerful catalysts for the chain extension reactions. It was found that by use of varying combinations of a tin catayst with a tertiary amine... 

The cross-linking of the resin is, of course, not carried out until it is in situ in the finished product. This will take place by heating the resin at elevated temperatures with a catalyst, several of which are described in the literature, e.g. triethanolamine and metal octoates. The selection of the type and amount of resin has a critical Influence on the rate of cure and on the properties of the finished resin. 

The pieces of cloth are then plied up and moulded at about 170°C for 30-60 minutes. Whilst flat sheets are moulded in a press at about lOOOlbf/in (7 MPa) pressure, complex shapes may be moulded by rubber bag or similar techniques at much lower pressures ( 15 Ibf/in ) (0.1 MPa) if the correct choice of resin is made. A number of curing catalysts have been used, including triethanolamine, zinc octoate and dibutyl tin diacetate. The laminates are then given a further prolonged curing period in order to develop the most desirable properties. 

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. 

The most common catalyst used in urethane adhesives is a tin(lV) salt, dibutyltin dilaurate. Tin(IV) salts are known to catalyze degradation reactions at high temperatures [30J. Tin(II) salts, such as stannous octoate, are excellent urethane catalysts but can hydrolyze easily in the presence of water and deactivate. More recently, bismuth carboxylates, such as bismuth neodecanoate, have been found to be active urethane catalysts with good selectivity toward the hydroxyl/isocyanate reaction, as opposed to catalyzing the water/isocyanate reaction, which, in turn, could cause foaming in an adhesive bond line [31]. 

Homogeneous catalysis by lin compounds is also of great indusirial importance. The use of SnCU as a Friedel-Crafts catalyst for homogeneous acylation, alkylation and cyclizaiion reactions has been known for many decades. The most commonly used industrial homogeneous tin catalysis, however, are the Sn(ll) salts of organic acids (e.g. acetate, oxalate, oleale, stearate and ocToate) for the curing of silicone elasloniers and, more importantly, for the production of polyurethane foams. World consumption of tin catalysts for the.se Iasi applications alone is over 1000 tonnes pa. 

Cerium octoate, in fuel additives Cerium salts, as fuel additives Cerium sulfonate, in fuel additives CFR21 172.615... 

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