Urea viscosity reducer

Example 6. High Solids, Two-Component, Clear, Aliphatic, Polyurea Coating. This example of an aliphatic, 100% urea coating utilizes polyaspartic esters as reactive diluents (see Section 4.2.3). These compounds allow fine tuning of reactivity and physical properties and eliminate the need for viscosity-reducing solvents. 

Furfuryl alcohol is used as a viscosity reducer for epoxy formulations. The addition of furfuryl alcohol to urea-formaldehyde resins improves the craze resistance and heat stability of the adhesives. Furfuryl alcohol serves as an effective wetting agent and solvent for phenolic resins in the manufacture of phenolic resin abrasive grinding wheels. Other miscellaneous uses of furfuryl alcohol include use in alkaline paint strippers and cleaning formulations, as a solvent and carrier for dyes in textile printing, and as a chemical intermediate. 

Ice water label paste is a very specialized water-based casein adhesive which is used primarily to adhere paper labels to beer bottles. The labels must remain attached if the bottles are chilled in ice or otherwise subjected to wet conditions, but they must wash off reusable bottles easily with hot water. Casein is dispersed with urea at an approximate 50 50 ratio in the presence of ammonium hydroxide as an additional dispersant. The high percent casein solids in this type formulation is possible because of the urea, which acts as a viscosity reducer. The urea, sometimes along with ammonium thiocyanate, functions also as a gel depressant. Zinc oxide and zinc acetate are used to crosslink and provide water resistance. A defoamer and a preservative are always included. Starch is one of several agents incorporated to shorten the thread of the adhesive to improve its performance on high speed labelling machines. 

In the propane process, part of the propane diluent is allowed to evaporate by reducing pressure so as to chill the slurry to the desired filtration temperature, and rotary pressure filters are employed. Complex dewaxing requires no refrigeration, but depends on the formation of a soHd urea—/ -paraffin complex which is separated by filtration and then decomposed. This process is used to make low viscosity lubricants which must remain fluid at low temperatures (refrigeration, transformer, and hydraulic oils) (28). 

Addition of 2% to 5% urea with respect to water is claimed to reduce the viscosity of the heavy hydrocarbon by at least 50% [308]. 

Emulsion blocks within the formation can form as a result of various well treatments and are more easily prevented (by using surfactants in conjunction with well treatments, see above) than removed. Aromatic solvents can be used to reduce the viscosity and mobilize oil-external emulsions (167). Low molecular weight urea-formaldehyde resins have been claimed to function in a similar manner in steam and water injection wells (168,169). Water-external emulsion blocks can be mobilized by injection of water to reduce emulsion viscosity. 

Most polypeptide chains devoid of cross-links assume a random-coil conformation in 8 M urea or 6 M guanidinium chloride, as evidenced by physical properties such as viscosity and optical activity. When ribonuclease was treated with P-mercaptoethanol in 8 M urea, the product was a fully reduced, randomly coiled polypeptide chain devoid of enzymatic activity. In other words, ribonuclease was denatured by this treatment (Figure 3.53). 

Changes in the hydrophilicity of UF resins are not uncommon. During an acid advance of a UF cook, solid urea is commonly added. This both adjusts the mole ratio of the cook to the desired level, and has the added advantage of reducing the viscosity. A surprisingly small amount of water will have the same effect on viscosity. 

In order to improve performance and processing efficiency of radiation curable systems it has been proposed that curing should be monitored using a technique of mechanical spectroscopy SS and in relation to this other workers have found that the molecular weight and structure of the diol component of multifunctional acrylates influenced the mechanical properties of the UV cured films produced 52,193. urea group in the resin tended to enhance the modulus of the cured film whereas a vinyl caprolactam diluent reduced resin viscosity for ease of coating. 

These features were also observed, although perhaps not quite as clearly in the dewaxing by urea and by methyl ethyl ketone (MEK) of an Indian washed Blue oil 27 (Figure 9.14) in which the solid point (closely related to the pour point) for the fractions is plotted against midfraction percent. The conclusion from this work is the same, that urea is much more effective in reducing the pour or solidification point for low viscosity (low boiling point) fractions than is solvent dewaxing. 

By extracting water from intracellular compartments, osmotic diuretics expand the extracellular fluid volume, decrease blood viscosity, and inhibit renin release. These effects increase RBF, and the increase in renal medullary blood flow removes NaCl and urea from the renal medulla, thus reducing medullary tonicity. Under some circumstances, prostaglandins may contribute to the renal vasodilation and medullary washout induced by osmotic diuretics. A reduction in medullary tonicity causes a decrease in the extraction of water from the DTL, which limits the concentration of NaCl in the tubular fluid entering the ATL. This latter effect diminishes the passive reabsorption of NaCl in the ATL. In addition, osmotic diuretics may also interfere with transport processes in the TAL. 

A typical urea resin would be made by charging urea and 37 per cent formalin to a kettle and adjusting the pH to 7.5 with dilute sodium hydroxide. The solution is heated to 90 C for 1 hr and then cooled to 70 C. The pH is reduced to 6.3, and reaction continued until a viscosity of 100 centipoise is obtained. The pH is then raised to 8.5 with sodium hydroxide and the batch cooled. 

---