Driers, primary

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). 

Loss of Dry. When the initial dry time of a solvent-based coating becomes substantially longer after aging, it is said to lose dry. The primary cause of this problem has been identified as adsorption of the drier on the pigment surface. Pigments with large surface areas are the worst offenders. 

Constipation can be due to primary and secondary causes (Table 18-1). Primary or idiopathic constipation is typified by normal-transit constipation, slow-transit constipation, and dyssynergic defecation. In the normal-transit type, colonic motility is unchanged and patients tend to experience hard stools despite normal movements. In the slow-transit type, motility is decreased leading to infrequent harder, drier stools. In dyssynergic defecation (also known as pelvic floor dysfunction), patients have lost the ability to relax the anal sphincter while coordinating muscle contractions of the pelvic floor. Some causes of secondary constipation are listed in Table 18-1. 

Primary driers like cobalt, lead and manganese napthenates or linoleates establish redox systems that lead to rapid auto-oxidation and cross-linking of resin. 

In the event of an explosion the lids were blown off, and this sometimes prevented the destruction of the drier. The method was not very safe, however, especially when drying other primary explosives. The fulminate was dried at a temperature between 35 and 45°C. 

Fig. 44. Diagrammatic view of a German brattice drier for primary explosives with screening of the product [67],...

Sometimes undesirable odors arise during or after a product s use The wet laundry odor in washing machines or the hot hair scent generated by hair driers are typical examples. In personal deodorants and air fresheners, diaper products and toilet cleaners, masking external odors is a primary reason for the products very existence. 

The bimodal agglomerates possess spherical morphology with sizes between 4 and 20 pm depending on the parameters of the spray drier. Agglomeration of smaller primary particles results in smoother agglomerate surface and better morphology. 

Previous w orkers concerned with the conveying function of rotary driers have generally given primary consideration to determining the time of passage. It was believed that the holdup in the drier was of vital importance in the drier design. Work on this problem was presented by Sullivan et al. (S15) and Smith (Sll, S12). 

Driers are metal salts, especially of cobalt, manganese, zirconium, calcium, and iron, that accelerate the conversion of the liquid film to a solid lead was commonly used as a primary drier, but due to its toxicity, it is rarely used now. 

A suspension of a-lactose monohydrate crystals in a lactose solution is atomized and dried in a spray drier. Approximately 10-20% of the total amount of lactose is in solution and the remaining 80-90% is present in the crystalline form. The spray-drying process predominantly produces spherical particles. The compactibility of the material and its flow characteristics are a function of the primary particle size of the lactose monohydrate and the amount of amorphous lactose. " ... 

I) Raw material. (2) Acid water. (3) Primary steam. (4) Secondary steam. (5) Vapor of 5.5 % furfural. (6) Demineralized water. (7) Cake to drier. (8) Reactor condensate. (9) Waste water. (10) Low boilers. 

Ionomer membranes based on perfluorocarbon polymers became available In the late 196O s. These materials have excellent chemical resistance, thermal stability, mechanical strength and strong acid strength, A number of functionalities have been studied. Including carboxylate, sulfonate and sulfonamide, but only the first two are available as commercial materials. Ferfluorlnated lonomers have been evaluated as membranes In a variety of applications, such as water electrolysis, fuel cells, air driers, Donnan dialysis In waste metal recovery, and acid catalysts, but the primary interest in these materials is for the permselective membrane In electrochemical processes such as In the production of chlorine and caustic (58). 

In practice, at the beginning of the primary drying stage, more than 90% of the water in the initial solution has frozen. The ice is then removed by sublimation. Unlike the freezing process, ice sublimation is amenable to some measure of control. The heat flow to the ice front must be adjusted to balance exactly the heat absorbed by the sublimation of ice at the operating temperature of sublimation. In this chapter, we discuss the contributing mechanisms by which heat is transferred from the shelves of the freeze-drier to the ice front and the mechanisms by which water vapour is transferred to the condenser (mass transfer), and their relative contributions to the overall sublimation process. 

Having estimated the optimum primary drying parameters, a pilot study should be performed. It is not good practice to carry out such a study either in an incompletely filled drier or by filling up shelves partly with empty vials. The reliability of pressure and temperature measurements should be checked at this stage. It has sometimes been found that the (apparent) product temperature exceeds the shelf temperature. Since this is an obvious physical impossibility, such an anomaly is due to faulty calibration of the thermocouple probe. 

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