INDUSTRIAL AND ENGINEERING CHEMISTRY
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Corresponding rate of heat loss (1/9.27) is 0.108 per square foot of surface of cylinder per hour per O F . temperature difference. Heat loss (0.108 X 830) is 90 B. t. u. per square foot per hour. To figure effective surface resistance of cylindrical insulation per square foot of heated surface, it is necessary to multiply the coefficient of resistance per square foot of insulation surface for given temperature and air conditions by the ratio of diameter of vessel to diameter of insulation. Since this ratio must always be used in this part of a heat loss computation, it is convenient to relate the graph to this same ratio. The above example calculated on the assumption of flat insulation would be: Resistance of insulation, (1/0.50) X 5 Resistance of surface Total resistnnoe
10.00 0.57 10.57
Corresponding heat loss is (1/10.57) X 830 or 79 B. t. u. per square foot per hour. The true value is 90 B. t. u. or 14 per cent more, which illustrates that for high-temperature vessels it is often worth while to figure heat losses more accurately than the flat surface assumption allows. This chart is also useful in working out
VOL. 32, NO. 7
combinations of pipe insulation for which heat losses are not given in tables. TABLEI. EFFECTIVENESS OF PIPE INSULATION OF VARIOUS PROPORTIONS
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Di 600 500 400 350 300 260 233 220 200 190 180 175 167 150 140 133 125 120 116 108 104 102
101
E
Di 0.167 0.200 0,250 0.286 0.333 0,385 0.429 0.455 0.500 0.526 0.556 0.571 0.600 0,667 0.714 0.750 0.800 0.833 0,862 0.926 0.962 0,980 0.990
[Dc 100) -Correction Resistance, formula 2 0.358 0 402 0 462 0 501 0 549 0 597 0 635 0 657 0 693 0 713 0 735 0 746 0 766 0 811 0 841 0 863 0 892 0 912 0 928 0 962 0 981 0 990 0.895
FactorsConductance, formula 1 2.790 2.485 2.164 1.996 1.821 1,675 1.574 1,522 1.443 1.402 1.301 1.341 1,305 1.233 1.189 1.159 1.121 1.097 1.078 1.040 1.020 1.010 1.005
MAKING CASEIN FIBER E. 0. WHITTIER AND S. P. GOULDl Bureau of Dairy Industry, U. S. Department of Agriculture, Washington, D. C. ASEIN fiber has been of In making casein fiber, alkalies are required lems of making fiber from the considerable popular inproteins of the soybean, of the to dissolve the casein; salts of metals such terestsinceitscommercial as calcium, and barium to inpeanut, of silk waste, of fish production was announced in waste, and of slaughterhouse crease strength; fat acids to increase flexiItaly in 1936. Its characteristics waste. have been discussed in many bility; acids to coagulate the fiber; and articles in textile and dairy substances such as sugars and salts to deThe Casein journals, but, with a few excepThe method used in the manuhydrate it. Formaldehyde, or other aldehydes, are used to increase further the facture of the casein affects the tions, details of the manufacturing processes have been pubfiber made from it. As stated strength of the fiber, and oil emulsions to lished only in patents (1-6). by Ferretti exposure of Since patents covering the increase further the softness and flexibility* casein to acidities greater than The effectiveness of compounds used for those ordinarily employed in novel features of our researches these specific purposes is discussed in this commercial casein manufacture have either been issued or are pending, and since our work is has the effect of causing the paper. done in the public interest, we fiber made from it to be much are publishing our results for softer than that made from the information of any who may wish to develop further the commercial casein. This softness is obtained a t the sacrifice manufacture of casein fiber. of some strength. Caseins prepared by the use of sulfuric or I n barest outline, the process of converting a protein into a lactic acids give stronger fibers than those prepared by the use fiber consists of dissolving the protein in a n alkaline solvent of hydrochloric acid. “Cooked-curd” caseins appear to give and extruding the solution through fine openings into a prestronger fibers than do those made a t lower temperatures. cipitating bath that is strongly acid in reaction. Such a simHowever, solutions of cooked-curd caseins are somewhat more ple procedure produces a fiber, but a number of characteristics viscous than those of other caseins and, consequently, must be necessary for its use in textiles, such as strength, flexibility, diluted to smaller concentrations before extrusion. Thus the softness, and insolubility, are lacking. The supplying of strength advantage of cooked-curd casein is offset by the these characteristics constitutes the problems of casein fiber necessarily greater dilution required to extrude it. Other research. The chemical attack can be made a t four pointsfactors being equal, we have found fibers spun from solutions the protein, the protein solution, the precipitating bath, and of greater concentrations of casein to be stronger than those the solutions for aftertreatment. spun from solutions of less concentration. We have obtained The only protein considered here is casein; it is probable satisfactory fibers from 8 and 12 per cent casein solutions, but that most of the factors discussed apply as well to the proba t a working temperature of 50” C., the most practical percentage appears to be 10. 1 Dr Gould died September 12, 1939.
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JULY, 1940
INDUSTRIAL AND ENGINEERING CHEMISTRY
Casein Solution The following casein solvents have been found to be practical: sodium hydroxide, trisodium phosphate, ammonium hydroxide, triethanolamine, and sodium pentasulfide in quantities only slightly in excess of the minimum necessary for solution. Borax may be used whenever it is compatible with other components. Barium and calcium hydroxides may be used if other substances are added to prevent precipitation of barium or calcium caseinates, but their use primarily and exclusively as solvents is not recommended. Of rather doubtful value are sodium sulfide and combinations of sodium hydroxide and carbon disulfide. Sodium cymene sulfonate and formamide, though solvents for casein, are objectionable because of their unfavorable effects on the fiber. We have found i t practically necessary to have present in the casein solution at least two other components-one to increase the strength of the fiber, the other to increase its flexibility. As strengthening agents, certain compounds of aluminum, calcium, barium, and, to a less degree, of magnesium can be recommended to be used in relatively small, but not critical, percentages. When compounds of calcium or barium are used, i t has been necessary to add sulfates or sulfonates of alcohols, fats, or aromatic radicals, either with or without sodium hexametaphosphate, in order to avoid premature precipitation of caseinates of these metals. Sodium lauryl sulfate and sodium oleyl sulfate have been particularly effective for this purpose. Of less value as strengthening agents are sodium silicate, sodium chromate, sodium tungstate, and sodium stannate. Compounds shown to be of no value for this purpose are calcium formate, calcium thiocyanate, and sodium titanate. Of the substances added to the casein solution to increase the flexibility of the fibers, the following were effective in proportions of the order of 1 per cent: oleic acid, linseed oil acids, Turkey-red oil, sodium glycerophosphate, sodium tartrate, glycol phthalate, ethyl glycollate, butyl tartrate, amyl lactate, sodium maleate, and urea. The effects of the following were either nil or to decrease flexibility: latex, aniline, octyl alcohol, triacetin, butyl stearate, ethyl glycol monobutyl ether, and o-toluidine.
Precipitating Bath and Aftertreatment Effective and desirable precipitants included sulfuric acid, phosphoric acid, acetic acid, acetic anhydride, monocalcium phosphate, and sulfamic acid, used in percentages varying from 0.5 to 10.0. The desirability of calcium chloride as a precipitant seemed to vary with the other components of the precipitating bath. It aided the retention of calcium by the fiber. Hydrochloric and oxalic acids had weakening effects on the fiber. The most satisfactory substances to increase the speed of “setting-up” or dehydration of the fiber were the sugars, particularlY glucose in about 20 Per cent concentration. The sulfates of the alkali metals can also be used. Zinc sulfate is effective, but it appeared to increase tensile strength a t considerable expense to flexibility. Ethanol, glycerol, acetone, and diacetone alcohol dehydrated but had appreciable solvent action on the fiber. Of agents for strengthening and increasing the insolubility of casein fiber during its passage through the precipitating bath and in aftertreatments, the following aldehydes have been effective: formaldehyde, acetaldehyde, crotonaldehyde, butylaldehyde, and heptaldehyde. Approximately 5 per cent is a suitable concentration. It has not been possible to control the action of tannic acid, and furfural-
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dehyde and dichromates have not imparted the desired strength In aftertreating casein fiber, we have used 5 per cent emulsions of several oils sold commercially for aftertreating rayon and have found them all effective in increasing the softiiess and flexibility of the fiber. The above lists of substances do not include many compounds that were tried and found to be incompatible with other essential components of the solutions. I n particular, casein solutions containing calcium or barium compounds were unstable in the presence of many substances that seemed desirable to use.
Typical Formulas The preceding discussion shows that it is possible to make fiber from casein with the aid of a considerable variety of combinations of auxiliary substances. Two examples of recipes giving relatively strong flexible fiber are as follows: RECIPE1. The casein is allowed t o swell for half an hour in about half of the required quantity of water used for the spinning solution, and the sodium hydroxide is added as an 8 per cent solution. The solution is then stirred until it is uniform, the oleic acid added, the solution stirred again, and the sodium aluminate added in the form of a solution in the rest of the water. The solution is again stirred thoroughly and then deaerated by keep ing it under vacuum for several hours. It is then ready to spin. FOR RECIPE1 TABLE I. FORMULAS
Spinning S o h . (in Water), 70 Casein 10.0 Oleic acid 1.0 Sodium hydroxide 0 27 Sodium aluminate 0.80
Precipitating Bath (in Water), 7” Sulfuric acid 2 0 Formaldehyde 5 0 G 1u co s e 20.0
After the two solutions are brought to the same temperaturefor example, 50” C.-the spinning solution is extruded under pressure through a rayon spinneret into the precipitating bath and wound on a bobbin. The fiber is immersed in a 5 per cent formaldehyde solution for 16 hours, then in a 5 per cent oil emulsion and dried. RECIPE2. The casein is soaked in half the water for half an hour, and the sodium lauryl sulfate is stirred in (Table 11). The calcium hydroxide, previously mixed with the remainder of the water, is added slowly t o the casein mixture and stirred until the dispersion is uniform. It is then deaerated by means of vacuum. TABLE 11. FORMULAS FOR RECIPE2 Spinning S o h . (in Water), % Casein 8.0 Sodium lauryl sulfate 1.6 Calcium hydroxide 0.8
Precipitating Bath (in Water), % Phosphoric acid 5.0 .\lonocalcium phosphate monohydrate 10.0 Formaldehyde 5.0 GI u c o B e 20.0
The spinning and aftertreatments are carried out as in the previous exam le. The phosphoric acid and monocalcium phosphate are order that a greater roportion of the calcium may be retained in the fiber than wouldge retained if sulfuric acid were used.
usetin
Literature Cited (1) Ferretti, A., French Patent813,427 (June 1, 1937) : British P a t e n t s 483,731, 483,807-10 (April 21, 1938). (2) Gould, S. P., and Whittier, E. O., U. S. P a t e n t s 2,167,202 (July 25, 1939), 2,169,690 (Aug. 15, 1939) ; others pending. (3) Millar, A., British P a t e n t 6700 (April 19, 1899). (4) Todtenhaupt, F., German P a t e n t s 170.051 (April 28, 1906), 183,317 (April 5, 1907), 203.820 (Nov. 2, 1908); F r e n r h P a t e n t 356.434 (Oct. 3, 1905); U. S. P a t e n t 836,788 (Nov. 27, 1906). (5) Whittier, E. O., and Gould, S. P., U. S. P a t e n t 2,140,274 (Dec. 13, 1938); others pending.
