Through-drier

Paint Driers and Polymer Additives. Paints based on alkyd resins (qv) dry by the oxidation and cross-linking of unsaturated side chains. Metal catalysts are included in paint formulations to promote this drying. Cerium carboxylates, eg, the naphthenate, are used as through driers, ie, to promote drying in the body of the paint film rather than at the film s surface (44). 

The net result is formation of water and a high concentration of free radicals. The cobalt cycles between the two oxidation states. Lead and 2irconium salts cataly2e drying throughout the film and are called through driers. Calcium salts show Httle, if any, activity alone, but may reduce the amount of other driers needed. 

Through-circulation dryers, 9 120, 148 Through driers, 2 149 Throwing power, 9 773 Thujopsene, 24 543-544 Thulium (Tm), 14 631t, 635t electronic configuration, l 474t Thyme, 23 171... 

Also in this category is the matter of mechanical handling. The adsorbent must dump from filters, flow through driers and kiln tubes, and perform well in mechanical handling equipment. As has been shown,4 granular solids exhibit significant variations in these respects. 

Metal catalysts, included in paint formulations promote drying. Cerium carboxylates are used as Through driers, i.e. to promote drying in the body of the paint film [20]. 

The apparatus utihzed in the Van der Made system is a column of suitably protected steel in small installations, reinforced concrete in large ones. The column is divided into sections of horizontal perforated celluloid plates with 0.7-mm. holes. Both the water and air enter at the bottom and pass upward through several of these plates. This method provides good mixing and allows utilization of low concentrations of ozone. Another novel characteristic of this process is the recovery of excess ozone at the top of the column and its recycle through drier, ozonator, and piston-type compressor. By use of a variable speed compressor, the quantity of ozone injected can be varied in accordance with the quality of the water. 

Recently work has been done on the introduction of a new group of through driers, the aluminium alkoxide derivatives. These compounds may have the general formula... 

The use of lead salts ( through driers) is being abandoned in many countries on toxicity grounds. A new group of through driers are now being introduced which are aluminium alkoxide derivatives. 

The secondary and through driers are of a group of metals, including lead, zirconium, calcium and cerium, which assist the drying of the lower layers of the paint film by mechanisms which are not fully understood, but probably involve interactions of the metal with carboxyl (and perhaps hydroxyl) groups in the film-former. Because lead is a cumulative poison, permissible levels of lead in household paints have been reduced so much that paint manufacturers now formulate paints of this type without the use of any added lead at all. 

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. 

Mooney Driers Co, Ca, DRI-Rx Mooney Driers Co, Mn, DRI-Rx Nuodex Nuxtra Cobalt Nuodex Nuxtra Zirco Nuodex Nuxtra Calcium Nuodex Adr (Blended Metals/Surface Drier) Nuodex Ltd (Complex of Metals/Through Drier) Nuodex Utd (Complex of Metals/Through Drier) Active 8 (Drier Stabilizer and Accelerator) Manchem Manosec CD-44 Cobalt/calcium/lithium carboxylates... 

Lead driers have traditionally been the most common, although toxicity concerns now severely restriet their use. Lead is a secondary drier as its sole function is to catalyze oxygen uptake. This and its relatively low reactivity make it a good through drier. For this reason it was widely used in combinations with primary driers in the past. It is still used where toxicity and atmospheric sulfide staining do not rule it out. Caleium soaps have been used with lead driers to improve lead solubility and low temperature drying. 

---