Assessment of Emulsion Quality during the Drawing of Copper Wire Rod
Abstract Generated abstract
This paper examines criteria for assessing the quality of oil-in-water emulsions used in copper wire rod drawing. It argues that plant indicators such as total fat content and alkalinity are not objective measures, because hydrolysis and reactions with residual copper sulfate can promote decomposition and copper soap accumulation with little change in those values. The authors propose copper soap content as a more reliable criterion and compare analytical approaches, noting the limitations of acid decomposition followed by iodometric copper determination. Experiments with organic solvents show that turpentine, toluene, benzene, and xylene selectively dissolve copper soaps, suggesting a basis for a colorimetric method using solvent coloration intensity.
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ASSESSMENT OF EMULSION QUALITY IN THE PROCESS OF DRAWING COPPER ROD
S. A. Babenko, R. I. Tasoev
(Presented by the scientific seminar of the departments of PMKhP and OKhT)
In the drawing of copper wire, an oil-in-water emulsion is used to lubricate the surface of the metal being drawn and the drawing channel. The emulsion is prepared by heating a mixture consisting of linseed oil, water, and caustic soda in a weight ratio of 25:5:1, followed by dilution with water in mechanical mixers and ultrasonic treatment. As a result of this treatment, a sufficiently stable oil emulsion is formed, stabilized by sodium soap.
In the process of drawing, the emulsion is gradually consumed. Owing to the hydrolysis of the sodium soap, fatty acids are released which, interacting with copper, form copper soaps. The alkalinity of the emulsion should thereby increase. On this basis, under plant conditions the quality of the emulsion is judged by total fat content and alkalinity.
An analysis of the processes occurring in the emulsion during drawing indicates that these indicators are not objective criteria of emulsion quality. Indeed, the following reactions occur in the emulsion:
\[ \mathrm{RCOONa + H_2O \to RCOOH + NaOH}. \tag{1} \]
Hydrolysis of the sodium soap leads to an increase in the alkalinity of the emulsion, which will be neutralized by the sulfuric acid released during the formation of copper soap:
\[ \mathrm{2RCOOH + CuSO_4 \to (RCOO)_2Cu + H_2SO_4}. \tag{2} \]
Copper sulfate enters the system, as our studies have shown, because of insufficient washing of it from the surface of the copper rod after pickling.
Since the transfer of copper into the organic phase increases with increasing pH [1], the binding of alkali shifts the hydrolysis reaction to the right. Thus, during operation, decomposition of the emulsion and accumulation of copper soaps in the emulsion occur, although the alkalinity and total fat content change insignificantly.
On the basis of the foregoing, the content of copper soaps in them may serve as a more objective criterion of the quality of working emulsions. The amount of the latter can be determined indirectly by analyzing the emulsion for copper content; for this purpose the emulsion is first decomposed with sulfuric acid, with formation of fat and a copper sulfate solution. Copper in the solution is determined by the iodometric method. This method
The method for determining copper in a working emulsion has the following drawbacks: it is time-consuming (the time for complete settling after decomposition of the emulsion with sulfuric acid is 1–2 h), laborious, and insufficiently accurate, since the amount of copper in the solution is determined by the completeness of decomposition of the copper soaps, and this process depends on the temperature of the emulsion, the acid concentration, and other factors.
It is more convenient to determine copper soaps by selectively dissolving them in organic substances. To select a suitable solvent, the following substances were investigated: kerosene, gasoline, turpentine, toluene, benzene, xylene, heptane, and hexane.
The experimental procedure was as follows. The emulsion to be analyzed was poured into a test tube, to which an equal amount of solvent was added. After 20 min of mechanical shaking, the test tube was placed in a centrifuge, in which, over 10 min at 4.5 thousand rpm, the emulsion was separated from the copper soap dissolved in the organic substance. Visual observation showed that kerosene, gasoline, heptane, and hexane, under these conditions, dissolve the copper soaps and oil and completely decompose the emulsion. Turpentine, toluene, benzene, and xylene predominantly dissolve the copper soaps, as can be judged from the dark-green coloration of the solvent. The intensity of the color depends on the amount of copper soaps contained in the emulsion and therefore can serve as a measure for their determination by a colorimetric method.
REFERENCES
- Gindin et al. ZhNKh, vol. 5, no. 8, pp. 1868–1875, 1960.