Drier

Driers, also referred as siccatives, are compounds used to catalyze the autoxidation process in drying or semidrying oil based resins at ambient or elevated temperatures. They are typically organometallic compounds, most commonly metal soaps of long chain monocarboxy-lic acids, supplied in a suitable solvent (carrier). These metal soaps are synthesized from a variety of metals and acids. Although the metal, being the active part of the compound, effects the drying reaction, the monocarboxylic acid component confers solubility and compatibility of the drier in solvents and resin. 

The first driers were based on fatty acids or rosin, which were subsequently replaced by naphthenic acid, a material obtained from crude petroleum. Due to scarcity of naphthenic acid, in modern driers it has been replaced by branched chain synthetic acids such as 2-ethylhexanoic acid and neodecanoic acid. 

Driers are supplied commercially as solutions in hydrocarbon solvents such as white spirit and a low amount of alcohols to improve stability against precipitation. Driers are generally specified by their metal content in the supplied form. 

Iron and cerium driers effectively catalyze polymerization and through-drying at elevated temperatures and therefore are used in baking enamels. Iron driers have the limitation of dark color, and hence cerium based driers are often preferred where color retention is important. 

Lead was used for years as a very effective through-drier, but for ecological and toxicity reasons, is rarely used in recent years. Zirconium driers are by far the most widely accepted replacements for lead. They improve through-drying mainly by the formation of coordination bonds with hydroxyl and carboxylic acid groups of the resin, and also by increasing the catalytic effect of primary driers. 

The saponification value is the mass in mg of KOH needed to completely neutralize 1 g of oil  

Usually an excess of base is used, and the excess is back-titrated with standard acid. 

Other characteristics of the oil are the melting point, the peroxide value, the free fatty acid content, and color. 

Linseed oil is the most commonly used fast drying oil for paint. It has one major disadvantage because it tends to yellow when used indoors. When exposed to sunlight, the yellowing tendency is inhibited or reversed. Hence, linseed oil-based paints are generally restricted to outdoor use or dark-colored indoor paints. 

The natural vegetable oils can be improved by cross-linking the glycerides. This is done by first converting the triglycerides into monoglycerides by the reaction 

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Anexcollent and inexpensive hotair drier (" A.M. Industrial Type Blower ) is manu factored by Bylock lilectric Ltd., Ponders End, Enfield. Middlesex. 

Drakkar Noir Dramamine DRAM cells DRAM devices Draperies Drawdown Drawing molten glass Draw-texturing Drew-Pfitzner ligands Dried algae meal Driente Driers... 

Paint driers Paint formulations Painting Paint removers... 

Panels then move into a cooling device, normally a wheel or rack, where they are held individually and air is circulated between them to remove the majority of heat remaining in the boards after pressing. It is desirable to reduce the average board surface temperature to about 55°C. This temperature is sufficient to complete the cure of adhesive in the core of the board. The heat also helps to redistribute moisture uniformly within the boards, because the board surfaces are drier than the core when the boards come out of the press. Warm boards are normally stacked for several hours to a day to allow for resin cure and moisture equalization. 

Polymer is separated from the polymerisation slurry and slurried with acetic anhydride and sodium acetate catalyst. Acetylation of polymer end groups is carried out in a series of stirred tank reactors at temperatures up to 140°C. End-capped polymer is separated by filtration and washed at least twice, once with acetone and then with water. Polymer is made ready for extmsion compounding and other finishing steps by drying in a steam-tube drier. 

Sodium Bicarbonate. Many soda ash plants convert a portion of their production to sodium bicarbonate [144-55-8], NaHCO. Soda ash is typically dissolved, carbonated, and cooled to crystallize sodium bicarbonate. The mother Hquor is heated and recycled. The soHd bicarbonate is dried in flash or tray driers, screened, and separated into various particle size ranges. Bicarbonate markets include food, pharmaceuticals, catde feed, and fire extinguishers. U.S. demand was approximately 320,000 t in 1989 world demand was estimated at one million metric tons. 

The most important feature of the pressure filters which use hydrauHc pressure to drive the process is that they can generate a pressure drop across the medium of more than 1 x 10 Pa which is the theoretical limit of vacuum filters. While the use of a high pressure drop is often advantageous, lea ding to higher outputs, drier cakes, or greater clarity of the overflow, this is not necessarily the case. Eor compressible cakes, an increase in pressure drop leads to a decrease in permeabiUty of the cake and hence to a lower filtration rate relative to a given pressure drop. 

Oxidation. Inks that dry by oxidation behave much like oil paint films and dry by means of the reaction of drying oils (qv) with oxygen. They contain metallic driers, which catalyze the absorption of oxygen by the drying oil (see Driers and metallic soaps Paint). 

Driers. These are generally soaps of cobalt, manganese, and other metals formed with organic acids such as linoleic, naphthenic, and other organic acids. They catalyze oxidation of drying oils (qv), and thus are used in inks that dry by oxidation (see Driers and metallic soaps). 

Other salts include lead arsenates and lead arsenites (see Insect control technology), lead chromates and lead sihcochromates (see Pigments), lead cyanide (see Cyanides), lead 2-ethyIhexanoate (see Driers and metallic soaps), and lead fluoroborate (see Fluorine compounds, inorganic). 

The floated mica concentrate is dewatered. After dewatering (qv), the mica is either dried in a fluid-bed rotary drier, flash dried in a fluid energy mill, or sold "drip-dry" to other mica grinders. The dry mica is then ground and screened to a si2e gradation dictated by the customer. 

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