Catalytic driers

A.ctive driers promote oxygen uptake, peroxide formation, and peroxide decomposition. At an elevated temperature several other metals display this catalytic activity but are ineffective at ambient temperature. Active driers include cobalt, manganese, iron, cerium, vanadium, and lead. 

A.uxilia driers do not show catalytic activity themselves, but appear to enhance the activity of the active drier metals. It has been suggested that the auxihary metals improve the solubiUty of the active drier metal, can alter the redox potential of the metal, or function through the formation of complexes with the primary drier. Auxihary driers include barium, zirconium, calcium, bismuth, zinc, potassium, strontium, andhthium. 

Water-emulsifiable vehicles contain emulsifiers that may act as plasticizers after film formation, affecting the hardness. Water-soluble vehicles usually contain a neutralizing amine, the primary purpose of which is to solubihze the resin. These amines can influence the drying properties as they tend to complex the metal drier, thus affecting the catalytic activity. Acceptable results are usually obtained with trialkylamines such as dim ethyl eth a n o1 amine, trimethyl amine, and aminomethylpropan o1 (7). 

If you do add catalytic recombiners, put flashback arrestors on either side of the catalytic recombiner tubes. In the recombination process, both water and heat are created. The arrestors make it a safer process. It is also necessary to provide a drier gas to the recombiner tube. Too much moisture on the catalytic bead surfaces will impede the action. 

For the preparation of co-precipitated, e.g. mixed metal oxide, catalysts, the drying step cannot be carried out satisfactorily in the preparation robot. Usually a spray drying step is applied in the production of this kind of catalyst, because the liquid phase of the precipitate suspension still contains dissolved salts that are essential for the catalytic performance. Hence, the suspension must not be filtered off nor can be dried by evaporation due to crystallization reasons. Since there are no laboratory spray-dryers available for that sample size, another method had to be implemented and was found in the freeze drying of these materials [4]. With this method almost the same is done like in spray diying but on another time-scale. Where a spray drier evaporates the water very quickly and thereby prevents the crystallization of the still dissolved salts, Ihe freeze drier literally at first freezes the solution and no crystallization can occur while the water is sublimated. Hence, an identical product is obtained. 

The oxidation of linseed oil, which takes place in drying, is attended by the generation of much heat. If the oil is exposed in thin layers on porous inflammable material, such as cotton rags or waste, spontaneous combustion may take place as the result of active oxidation. Linseed oil dries more rapidly when exposed to the air if it has been previously boiled for some hours. The process consists in heating the oil with certain oxides or salts, called driers, such as litharge, lead acetate, or borate of manganese, which probably act as catalytic agents... 

Utility — The catalysts of the present invention can be used in the same ways as prior art catalysts containing the same active catalytic materials. Catalysts of the present invention are particularly valuable for the treatment of combustion gases emitted from gas-buming devices such as stoves, furnaces, refrigerators, clothes driers, and the like, and for treatment of the fiunes from automobile exhaust and other internal combustion exhausts. The... 

Catalytic regenerators, sludge incinerators Kilns, driers, material handling Thermal processes, rock acidulating, grinding... 

Drier (1528) n. A composition, which accelerates the drying of oil, paint, printing ink, or varnish. They consist mainly of metallic salts, which exert a catalytic effect on the oxidation and polymerization of the oil vehicles employed and are available in both solid and liquid forms. 

Drier dissipation n. A loss in catalytic power of a drier due to a physical absorption or a chemical reaction with certain pigments. 

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. 

Iron driers are used in heat-cured paints where the poor color can be accomodated. Temperatures above 100°C are required for catalytic activity, but high film hardness is obtained. 

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