Industrial Silicone Products

CVD gaseous reactants (precursors) delivered to a heated substrate in a flow reactor undergo tliennal reaction to deposit solid films at atmospheric or reduced pressure, and volatile side products are pumped away. CVD is used for conductors, insulators and dielectrics, elemental semiconductors and compound semiconductors and is a workliorse in tire silicon microelectronics industry. 

Even though silicon is extremely abundant, only one silicon-containing compound appears in the list of top 50 industrial chemicals. That is sodium silicate, Na2 Si03, used for the manufacture of silica gel and glass. Nevertheless, with the advent of the electronic age silicon has become an extremely important substance that is the primary ingredient of most semiconductors. Because these are microscale devices, the quantity of production of silicon remains small compared with that of fertilizers and construction materials. Although relatively small in quantity, the value of silicon products is quite high. 

Industrial poisoning. The production of silicone products uses substances harmful for human health. These are inorganic substances (ammonia, chlorine, sodium and potassium hydroxides, sulfuric and hydrochloric acids, hydrogen chloride) and organic compounds of various types, such as hydrocarbons (methane, benzene and its homologues), chlorine derivatives (methyl- and ethylchloride, chlorobenzene), alcohols (methyl, ethyl, n-butyl, hydrosite), acetone, pyridine, etc. The information about their toxicity, explosion hazard, effect on human body, as well as maximum allowable concentrations of gases and vapours in the air at workplace can be found in special references.(Ryabov 1970). A comprehensive description of silicone substances is given in Table 29. 

This chapter gives a brief description only of the industries where silicone products have been most widely used. However, the applications of silicone polymers and materials are growing there is no doubt that the possibilities they offer will continue to increase with further research into this exciting field of chemistry. 

However, emission control dust or sludge from ferrochromium and ferrochromium-silicon production is listed as hazardous waste by EPA (1988b). The processed wastes from several chromium chemical industries are designated as hazardous wastes as well (EPA 1981), and disposal of process wastes is regulated by the EPA. Land filling appears to be the most important method for the disposal of chromium wastes generated by chemical industries. Of the total chromium released in the environment by chemical industries, 82.3% is released on land. An equally large amount of chromium waste is transferred off-site (see Section 5.2). It is anticipated that most of this off-site waste will be disposed of in landfills after proper treatment. It is important to convert chromium wastes into forms of chromium... 

Although the platinum-catalyzed reactions are not as practical as palladium used for the same purpose, several types of unique discoveries still are noteworthy. Besides electrophihc C-H activation, the platinum complexes are efficient catalysts for hydrosilation see Hydrosilation Catalysis) that is important to silicon polymer industry. Platinum carbene catalysts are prepared from Karstedt catalyst (9) and imidazolium salts. The trials of model hydrosilylation reactions show very high yields of regioselective products (<1% impurity) with remarkable TON (see Turnover) (<30ppm catalyst load) (Scheme 81). ... 

Silicone products give excellent adhesion to many substrates used in the building industry (e.g. concrete, glass, ceramics and metals), and in most cases primers are not needed. However, the use of primers gives much stronger adhesion. 

The market for silicone elastomer products of this decade has expanded dramatically with increase of business machines and home electronics such as personal computers, copy machines, printers, TV sets, video cameras and so on. Various silicone products are used for electrical and electronic fields Based on the electrical conductivity, there are three grades of silicone rubbers. Insulating stocks are used for anode caps used for the cathode ray tube of TV sets, or plug boots and oil bleed connectors for automobiles, for instance. Electrically conductive silicones are used in products like rubber contact switches for TV remote controllers, handy phones, zebra connectors, EMI (electron magnetic interference) shield gasket and so on. And semiconductive silicone elastomers used for semiconductive rollers for plain paper copy machines and page printers, and antistatic materials. These relatively new materials have the volume resistivity of 10 -10 ohm-cm, and may be used in many other industrial fields. 

Poly(organosiloxanes) are built up of a combination of the units R3SiO]/2 (monofunctional, abbreviated to M), R2Si02/2 (difunctional, abbreviated to D), RSi03/2 (trifunctional, abbreviated to T) and Si04/2 (tetrafunctional, abbreviated to Q). A combination of these units is chemically possible in the widest sense. In industrial silicone products R is generally a methyl- or a phenyl-group. 

These diverse polyorganosiloxanes form the basis of industrial silicone products. The product spectrum is vast, manufacturers with a complete product range having in excess of 1000 individual products in their program. 

Silicones have been produced industrially since the 1940 s. In 1995 there were thirteen silicone producers in Western industrialized countries. Silicone production can be estimated on the basis of the production of organochlorosilanes, the starting materials for silicone production, taking into account that ca. 0.5 kg of methylsiloxane is produced from 1 kg of dimethyidichlorosilane. Since silicone products generally contain additives, such as fillers, or are combined with other components, the total quantity of silicone products should be similar to the quantity of (organochloro)silanes produced. This was 1.3 10 t in 1995 with a value of ca. 8 10 DEM. The largest markets... 

Sino-America Silicon Products Inc. No. 8. Industrial East Road 2. Science-Based Industrial Park Hsinchu, Taiwan, R.O.C. 

For the solar industry, impurity control and alternative raw materials are of great interest. In the normal metallurgical silicon production furnace, silica is charged into the form of quartz lumps. The carbonaceous materials have many forms like charcoal coke, coal, and wood chips. The charge is carefully composed and the raw materials are selected to give best possible yield with respect to Si and to avoid unwanted impurities. Also, the refractory materials and the consumable electrodes are source of impurities. The Si from the arc... 

AI3-23126 3,5-Dimethyl-1-hexyn-3-ol EINECS 203-500-9 1-Hexyn-3-ol, 3,5-dimethyl- NSC 978 Surfynol Surlynol 61, Surfactant, wetting agent used for paper coatings. Inks, floor polishes, and glass cleaning formulations cleaner In silicon wafer industry, bp = 150° d= 0.859 08 = 1.4340. Air Products Chemicals Inc. 

Dow Coming Corporation and other companies have incorporated VMS fluids into a variety of formulated products to replace a variety of solvents. These include solvents classified as ODS, VOCs, or HAPs such as CFC-113, saturated hydrocarbons like hexane and Stoddard solvents, and in some cases aromatic solvents like toluene and xylene. All of the replaced solvents are VOCs except CFC-113 which is an ODS. Furthermore, hexane is a neurotoxin, and many of the others are thought to cause liver damage. These characteristics are in contrast to the environmental friendliness and low order of toxicity of the linear VMS fluids. Many applications depend on the excellent solvency of VMS fluids for other silicone materials. The impact of VMS is multiplied by the versatility of silicone products which serve a broad spectmm of US companies, including those in the transportation, constmction, electronics, health care, textiles, paper, personal care, coatings, and process industries. 

Fig. 1. Manufacture of silica and breakdown of silicone products (printed from A. Tomanek Silicon and Industry" published by Wacker Chemie GmbH, Munich, 1991).

The technology of silicon deals mainly with the big scale production of hyperpure silicon, silicon carbide, silicates and silica, and industrial silicone products. The surface synthesis and modification of a wide range of substrates may be accomplished with silanes. Deposition techniques include the... 

The market for silicon has grown from 500000 Mt in 1980 and exceeded for the first time 1 000 000 Mt in 2000. Its growth has accelerated recently, reaching rates of 5-8 % per year. In the same time span the industrial process for production of metallurgical grade silicon has improved its efficiency by almost 25 % and is currently operating close to the technical limits. Supply has been secured by improved productivity, by erection of new furnace capacity, and by conversion of ferrosilicon furnace capacity to silicon production. 

Miscellaneous silicone products. Most of the major silicone manufacturers sell over 100 different silicone products, and the applications of these cover a very wide range. Here there is space to mention only two more applications the first being the use of silicone oils and emulsions for the prevention of foam in numerous industrial processes, the other being the use of silicone-containing copolymers as surfactants in the manufacture of polyurethane foams from di-isocyanates, ethylene/propy-lene polyethers and a little water. Unless a suitable surface-active surfactant is added, polyurethane foams tend to collapse before the polymerization is complete. One of the best types of surfactant is a poly-siloxane to which polyethers are attached ... 

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