Methods for producing

Melt Extrusion. By far the most important method for producing film and sheeting materials reties on one or another of the various melt extmsion techniques (5). The main variations of melt extmsion are the slot (or flat) die-cast film process, the blown films process, and the flat die sheeting-stack process. These may be combined with one or more steps such as coextmsion wherein multilayer film or sheet is formed, biaxial orientation, and in-line coating (6). 

Petroleum. Thermal cracking (pyrolysis) of petroleum or fractions thereof was an important method for producing gas in the years following its use for increasing the heat content of water gas. Many water gas sets operations were converted into oil-gasification units (55). Some of these have been used for base-load city gas supply, but most find use for peak-load situations in the winter. 

The presence of the L-form of mannose is unusual. The side-chain substitution is randomly distributed (242) approximately two-thirds of the side chains ate rhamnose. The repeat unit may also contain an 0-acyl group, but the distribution of these units has not been completely determined. The polymer is moderately soluble in water but is insoluble in isopropanol solutions, which are used to obtain the polymer from the culture medium. A method for producing a rapidly hydrating form of welan is avaUable (243). 

In addition to large-scale process work, there is also some effort expended in providing synthetic methods for producing small amounts (<100 kg/yr) of materials needed for replacement of naturals that are being discontinued or in short supply. Examples are ambrinol (59) and dihydro-y-ionone (60) for the replacement of ambergris. More recendy, tincture of tonquin musk has been replaced by using, among other materials, mixtures of macrocyclic ketones and alcohols which have been found in the natural substance. 

Another method for producing petoxycatboxyhc acids is by autoxidation of aldehydes (168). The reaction is a free-radical chain process, initiated by organic peroxides, uv irradiation, o2one, and various metal salts. It is terrninated by free-radical inhibitors (181,183). In certain cases, the petoxycatboxyhc acid forms an adduct with the aldehyde from which the petoxycatboxyhc acid can be hberated by heating or by acid hydrolysis. If the petoxycatboxyhc acid remains in contact with excess aldehyde, a redox disproportionation reaction occurs that forms a catboxyhc acid ... 

This reaction is highly exothermic thus, it is difficult to control the reaction temperature (31). The oldest method for producing SiCl is the direct reaction of sihca and chlorine in the presence of carbon as a reducing agent (24). 

Manufacture. The oldest method for producing Na2S is by the reduction of sodium sulfate with carbon in a refractory oven at 900—1000°C. Whereas this method is no longer used commercially in the United States, a variation is used to produce sodium sulfide captively during kraft pulp processing to replace lost sodium and sulfur values that were initiated into the system by merchant-suppHed sodium sulfide. In this method, sodium sulfate is added to the system in the recovery furnace, where it is reduced by carbon from the wood pulp to produce sodium sulfide. 

Kingdom. Adapted to steelmaking, the open-hearth process was the principal method for producing steel throughout the world until 1970. As of this writing (1996), it is stiU used in China and the CIS. 

Efforts toward producing synthetic steroids, particularly cortisol, expanded during World War II to enable researchers to explore the possibiUty of medicinal appHcations of corticosteroids. In 1948, the discovery that cortisone dramatically alleviates the symptoms of arthritis led to intensive research on the antiinflammatory properties of corticosteroids. The development of partial and total syntheses for the commercial preparation of cortisone, alternative methods for producing cortisone, and the search for more potent antiinflammatory analogues gready stimulated both academic and industrial steroid research. 

Pyrolysis of the i j -pinane produces dihydromyrcene (24) (citroneUene) as the major product in 50—60% yield. Fractionation of the cmde product then gives an 87 wt % dihydromyrcene (57). Dihydromyrceno1 (25) produced from the dihydromyrcene is becoming increasingly important as a fragrance material. It has excellent stabiUty and has a powerhil, fresh, lime-like aroma. Hydration of citroneUene using formic acid has become an important commercial method for producing dihydromyrcenol (58). 

Vanadium metal can be prepared either by the reduction of vanadium chloride with hydrogen or magnesium or by the reduction of vanadium oxide with calcium, aluminum, or carbon. The oldest and most commonly used method for producing vanadium metal on a commercial scale is the reduction of V20 with calcium. Recently, a two-step process involving the alurninotherniic reduction of vanadium oxide combined with electron-beam melting has been developed. This method makes possible the production of a purer grade of vanadium metal, ie, of the quaUty required for nuclear reactors (qv). 

After 1950, benzene in motor fuel was largely replaced by tetraethyllead but the demand for benzene in the chemical industry persisted and soon exceeded the total production by the coal carbonization industry. To meet this growing demand, methods for producing benzene directiy from petroleum sources were developed. 

There are several mathematical methods for producing new values of the variables in this iterative optimization process. The relation between a simulation and an optimization is depicted in Eigure 6. Mathematical methods that provide continual improvement of the objective function in the iterative... 

Early attempts to produce cephalosporin analogs by varying the 7-acylamino substituent were frustrated because, in contrast to previous experience with penicillins, a good method for producing the necessary 7-amino compound (33a) could not be found. This problem was finally solved when it was discovered that diazotization of the a-aminoadipyl residue produces an iminolactone (33b) which can be hydrolyzed to the free amine in good yield. Subsequently an improved procedure was developed which involves silylation of the carboxyl groups followed by reaction with phosphorus pentachloride to yield iminochloride (33c)... 

The experimental methods for producing planar shock compression can be divided into three general categories, namely, explosives, guns, and energy deposition. Guns are considered the most versatile of the three. 

The method for producing formaldehyde was described in Chapter 19. In aminoplastics manufacture it is used in the form of formalin (36-37% w/w CH2O). As in the case of phenolic resin production, formalin with both high and low methanol content is used according to the needs of the manufacturer. The low methanol content formalin is more reactive but is also less stable and must be used soon after its preparation. For this reason some resin manufacturers prefer to use formalin with a high 7-10%) methanol content. 

The use of the Grignard reagents of the type RMgX for the production of alkyl-and aryl-chlorosilanes was pioneered by Kipping in 1904 and has been for a long time the favoured laboratory method for producing these materials. 

The RTV rubbers find use in the building industry for caulking and in the electrical industry for encapsulation. It also provides a useful casting material for craft work. Perhaps most important of all it provides a method for producing rubbery products with the simplest of equipment and can frequently solve a problem where only a small number of articles are required. 

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