October 1950
INDUSTRIAL AND ENGINEERING CHEMISTRY
Rinea and Korf (6) have recently studied the styrenation of linseed oil and have reported that at 150' C. the reaction can be carried out so that no polystyrene is formed. On the other hand, Brunner and Tucker (1)claimed that, on refluxing styrene and dehydrated castor oil in xylene at 14.0' C., at least 90% of the styrene can be accounted for as pure polystyrene. Hewitt and Armitage (S), using the same materials and refluxing 25 hours, ehow that 85 to 90% of the styrene combines with the oil. It is thus not clear that polystyrene is found in styrenation reactions. It seems possible that the incompatibility observed in many instances may be fatty acids to which many styrene segments have combined forming materials more nearly resembling polystyrene than the oils in their solubility properties. This mtuation is undoubtedly more pronounced in oils where three fatty acids, combined with many styrene segments, might well be expected to separate from the oil. It has not been proved that a second group can add to acids like linolenic which has several positions where a growing chain could add. Whether a fatty acid with two chains of 10 styrene wgments would have the same solubility properties as a fatty acid with one chain containing 20 styrene segments is not known, but, if they do, this might be an explanation of the observed difference in solubility with the same styrene content. The addition of more than one styrene chain per fatty acid may be an explanation of the apparent lack of fatty acids containing 4 to 7 styrene segments, because if formed, these may combine with other growing styrene chains to give more highly otyrenated acids.
2099
CONCLUSIONS
Styrene adds to oleic acid a t 160' C. to form styrenated oleic acid. Styrene combines with linseed fatty acids a t 180"to 275' C. to form styrenated fatty acids containing 1 to 25 styrene segments. As the temperature is increased, the products are more soluble. On separation of reaction products from an equal weight of unsaturated acids no evidence of uncombined polystyrene was obtained. ACKNOWLEDGMENT
The assistance of L. E. Novy in carrying out the experimental work is gratefully acknowledged. LITERATURE
crrm
Brunner, W,, and Tucker, D. R.,Research, 2, No. 1, 42 (1949). Dunbrook, R.F., India Rubber World, 117, No. 2,205 (1947). Hewitt, D. H., and Armitage, F. J.. J . Oil C o h r Chmists' A8~oc.,29, No. 312, 109 (1946).
Peterson, N. R., Paint Varnish Production Mor., 28,234 (1948). Powers, P. O., IND. ENO.CHEM.,ANAL.ED., 14,387 (1942). Rinse, J., and Korf, C., Oil & Colour Chemists' Aseoo., Rothesay Conference (May 1949). Schroeder, H. M.. and Terrill, K. L.. J . Am. Oil Chemist#' 800.. 26, 153 (1949).
RECEIVEDSeptember 15, 1949. Presented before the Division of Paint, Varnish, and Plastics Chemistry, 116th Meetins, AYRRICAN CAEMIOAL SOCIETY. Atlantic City. N. J.
Electrodeposition of Copper Powder from Acid Sulfate Baths D. W. DRUMILERl, R. W. MOULTON, AND G. L. PUTNAM University of Washington, Seattle, Wash. Copper powder was prepared by electrodeposition from copper sulfatglsulfuric acid solutions. The limits of the operating variables studied were as follows: temperature, 26.3' to 50.3' C.4 current density, 34.1 to 83.5 amperes per square foot; copper concentration, 6.7 to 38.4 grams of copper, as the sulfate, per liter; and sulfuric acid concentration, 9.9 to 195 grams per liter. Current yields decreased at the lower temperatures and at the lower copper sulfate concentrations; increasing the temperature and copper sulfate concentration above the optimum values
c
OPPER powder is
t
1~ basic raw material in powder metallurgy. Good flow rate, chemical purity, and low oxide content are properties usually desired in a powder. Moreover, apparent density also markedly influences the characteristics of the finished products; where tensile strength is important, materials of high density are used; where lubrication is important, it is often desirable to use low density powders which tend to give shape products of high porosity. Flow rate and apparent density are controlled by particle sise, shape, and sise dietribution. Thus Constock (S) states that the regulation of particle shape and density and the careful modulation of particle sizes have been responable forsurprisinglygreat improvements of metal powder products. 1
Prewnt address. Shell Oil Company. Martiner. Cblif.
resulted in deposition of the copper as an adherent plate instead of powder. Under the conditions tested, the yield of copper powder increased with increasing acid concentration. Flow rate of the product increased with increase in copper concentration and reached a maximum at about 100 grams of sulfuric acid per liter, whereas the percentage of powder finer than 200 mesh increased with decrease in temperature, current density, and wpper concentration. Over the range investigated, apparent density of wpper powder increased with increase in current efficiency.
Production of copper powder by electrodeposition, one of the principal methods of manufacture ( I , & 7, IO), is conducted under carefully controlled conditions. The range over which the opera& ing conditions may be varied is limited by two other competing reactions-either evolution of hydrogen or deposition of copper as an adherent plate at the cathode. Within the operating range, powders of varying properties may be obtained. The general conditions favoring powder deposition are low temperatures, low copper concentration, high acid concentration, and high current density combined with frequent removal of powder from the cathode, Hothersall and Gardam (8) recommended conditions as follows for the economic production of high density copper power on a pilot plant scde:
INDUSTRIAL AND ENGINEERING CHEMISTRY
2100
Vol. 42, No. 10
EXPERIMENTAL
HERMOMETER
Figure 1 illustrates the cell and auxiliary apparatus used. Two anodes and one cathode, each 4 X 6 X l/le inches of electrolytically refined copper, were spaced 1 inch apart in a glass vessel. Constant agitation of the electrolyte was provided with an electric stirrer with a 1-inch propeller. The electrodes were cleaned before each trial with steel wool, followed by a dilute nitric acid dip and water rinse. All chemicals used were C.P. grade. The copper contents of the baths were determined by the iodine-thiosulfate method (6). Acid concentrations were determined by titrating a 10-ml. sample with sodium hydroxide until a permanent cupric hydroxide precipitate appeared. Titration of copper sulfate solutions of known acid concentration proved this method to be sufficiently accurate for this work. Copper purity was determined by heating a bgram sample of the powder to constant weight in hydrogen. It was assumed that. the hydrogen-reduced sample was pure copper,
loa 90 80 70
0 40 80 120 I60 200 ACID CONCENTRATION IN CRAMS PER LITER
Figure 1. Cell Used for Laboratory Production of Electrolytic Copper Powder
:: 6 405
t
20 30 40 so CRAMS COPPER PER UTER
eo
Cathode current density, 72 amperes per square foot Temperature, 30" C. Copper concentration, 10 to 15 grams of copper per liter, as the eulfate Acid concentration, 140 to 160 grams of sulfuric acid per liter Removal of powder from cathode a t 15 minute intervals 50 n
70 80 90 100 AMPS / FTz CURRENT MNSlTY
60
100
90 80
70 20
30
40 50 60 TEMPERATURE,%.
m
Figure 3. Effect of Operating Variables on Powder Current Efficiency
IO-ML GRAWATE CYLINDER
Figure 2. Apparatus Used for Determination of Flow Rate of Copper Powder
Jones (9) has also listed general conditions for production of suitable powders. Excellent reviews of the patent literature were made available by Rossman (11)and Cordiano ( 4 ) . The testing, uses, and properties of copper.powder have been summarized by Baeza (2), Cordiano ( 4 ) , Schumacher and Souden ( I $ ) , and Wulff (14).
The purpose of the study reported here was to determine the specific effect of operating variables on the product characteristics and cell efficiencies of copper powder electrolytically deposited from acid sulfate baths.
Unless otherwise noted, the duration of current flow in each experiment was 30 minutes, the current being interrupted after 15 minutes in order to remove the deposit with a test tube bruah. The same cathode was used for the remainder of the experiment. The powder removed from the cathode was collected in a 12-inch evaporating dish filled with water, the powder being washed by decantation until barium chloride did not give a sulfate test. The powder was finally collected in a weighing bottle and dried at 60' C. in a vacuum oven. Occasionally the powder wad slightly caked when removed from the oven, and it was necessary to disintegrate the cake by placing between two sheets of paper and rubbing lightly. The powder was stored in a glass vial and sealed with paraffin. The apparatue used for determining the flow rate and apparent density of 10-gram powder samples is shown in Figure 2. Tests with the same sample gave results in close agreement. Apparent density was determined from the final volume which the powder occupied after prolonged tapping resulted in no further decrease in volume (13). The data on flow rate and apparent density are
INDUSTRIAL
October 1950
.
AND ENGINEERING CHEMISTRY
cathode is insufficient to carry the current, was observed at high current densities, low copper concentration, and low temperatures. Apparently, high copper concentration in the cathode film increases the tendency for formation of adherent copper plate, since the latter type deposit tended to form at low current densities, at high copper concentrations in the electrolyte, and at high temperatures. In these experiments, convection was held constaht with a stirrer, but undoubtedly the characteristics of the deposited copper are also influenced by the rate of flow of solution past the cathode. Optimum efficiencies were found at 40' C., 75 amperes per square foot, 12 to 31 grams of copper per liter, and 90 to 200 grams of sulfuric acid per liter. I n the experiments on
TABLE I. OPERATINGCONDITIONS FOR COPPERPOWDBIR PREPARATION Current
Variable Teated Temperature Current density Copper sulfste concn. Sulfuric acid concn.
T ~ ~ ~Density, , ,
' c*
.. 40
40 40
Amp./s9. Ft. 75 75 75
ararns of aramof Cu/Liter
H2s04/Litsr
12.7 12.7
92.5 92.5 92.5
..
31.9
2101
reproducib1e it in ?& ' Powder s c r e e n i n g waa done with a 5gram sample and a Ro-Tape machine with 1W, 15&, and 2OO-mesh, 8-inch Tyler sieves; t h e time of shaking waa 25 m i n u t e s . Calculation of powder current e f f i c i e n c y PERCENT CUWiENT ETrlClE*Y baaed On the COPPER POWDER & A M R E N T COPPER w e i g h t of d r i e d Figure. 4. Effect of Operating powder r e c o v e r e d Variables on Apparent Density of from each trial, asCopper Powder suming the deposit to be pure copper. The operating variables studied were: temperature, 213.3~ to 50.3' C.; current density, 34.7 to 83.5 amperes per square foot; copper concentration, 6.7 to 38.4 grams, of copper liter, as copper sulfate; and sulfuric acid concentration, 9.9 to 195 grama per liter. Table I gives the values of the conditions held constant during each series of experiments. DISCUSSION OF RESULTS
P O W D CURRENT ~R EFFICIENCY.Powder current efficiency, based on the amount of copper actually recovered, is reduced by evolution of hydrogen or by deposition of copper as an adherent plate a t the cathode. The specific effect of operating variables on powder current efficiencyis shown in Figure 3. Hydrogen evolution, which occurs when the rate of diffusion of copper ions to the
Figure 5. Apparent Density us. Total Metal Current Efficiency
TABLE 11. ELECTROLYTIC PREPARATION OF COPPERPOWDER Current Density,
1
Cu Acid Concn., Concn., Run TzT, @!$[ Grams/ Grams/ No. Liter Liter 5A 12.5 92.5 5B 12.3 93.6 5c 12.5 94.5 5D 12.5 94.5 5E 13.3 88.0 6A 13.5 84.8 0B 13.9 88.0 6C 85.7 13.5 8A 26.5 79.8 8B 78.0 38.4 8C 77.2 31.3 8D 16.3 82.8 8E 6.72 85.7 9A 80.8 9.9 31.4 9B 56.8 9c 31.7 92.6 9D 139.0 32.2 9E 195.0 33.1 32.8 87.2 10 11A 7.77 93.8 11B 13.9 90.4 11c 20.0 90.4 llD 25.8 88.5 11E-I 31.2 91 .o ia 13.5 94.3 14A 13.2 76.4 14B 31.4 90.0 4 Copper powder plus adherent copper. b Funnel tapped conetsntly t o produae flow.
Powder Current Efficiency,
%
74.7 83.2 93.8 88.7 92.7 85.5 89.9 92.2 93.6 7.8 88.3 95.3 72.7 19.8
80.0
94.7 93.0 95.0 88.5 75.9 90.0 91.0 92.8 89.3 80.0
91.5 88.1
Total Metal Current E5ciency4,
%
Cell Voltage, Volt8
87.8
0.80
... ... ... 1.00 ,*.
... ... .
I
.
9r:7
.... .*
99.9 100 I O 98.0 100.0 99.0 98.5 77.4 93.2 96.8 96.8 99.3
... ... ...
Apparent Density Grams/
MI.
1.23 1.11 1.05 1.09 0.98 1.06 1.18 0.99
1.53 1.02 1.30 1.37 1.42 1.45 1.17 1.41 3.60
1 .oo 1.08 1.21 2 80 1.34 0.94 0.83 0.76 1.04 1,18 1.13 1.07 1.08 0.97 1.13 1.21 0.98
3:ie 2.05 0.88 4.00 3.63 3.40 3.50 2.40 2.24 1.16 1.25 1.67 1.93 2.53 1.04 0.95 3.63
0.86
Flow Rate, Grams/ See. Poorb Poorb Poorb 1.16 2.30 2.32 1.58 1.25 5.90 8 .'do
3.84 0.15b 6.00 8.50 8.20 8.70 5.20 3.00 0.80s 0.70b 1.97 4.20 6.00 4.20b 1.84 9.10
200 Mesh,
% 72 75 61 64 79 95 76 80
63
ii 80
87
..
65
62
61 60 62 77 63 57 55 46 65 85 71
Purity, in 3yTirO:en 1:45 0.61
.. ..
1:io
0.52
.. ..
0:is 1 .oo
..
0:09 0.38 0.11 0.10 0.53 0.20 0.13 0.10 0.13 0.30 0.23 0.10
2102
INDUSTRIAL AND ENGINEERING CHEMISTRY
V d 42, No. IO
n
1
Figure 6. Photomiuographe of Copper Powder A
B
--
Run 11.4 7.77 m x m a of m p p p u I~I u r Rum 8C.' 31.3 m r n a of mppu pu li-
variation in scid Wuccntration. LIEcopper concentration was increased from 12.7 to 82 grams per liter because of the poor flow oharacteristics of tha powder8 produced a t the lower copper wnoentrsticns. CELLVOLTAQS.Cell voltage was primarily a funotion of acid concentration. At acid eoncentrations within the optimum range of 90 to 200 gams per liter, cell voltnges varied fmm 0.8 lo 1.25 volts, depending on current densi!,y, t,emporature, and oopper canceritratinn as shown in Tahlo 11. A w n n e a ~I)F:ssI-. As shown by Figure 4, apparent density Increased with increase in mppw concentration, increase in temperature, and decrease in wid concentmtion. Change in current density had little effect. Evidently the larger size particles were deposiied as plathg conditions were approached-tha! is, increased teinporaturo and copper roncfntration-rpiultirlg in powder o f higher q)p~reiitdensity. Apparent density %.as also found to incrcase with increaac in total current effirioncy based on the toto1 capper deposited as powder and &F d i e r e n t wpper. The difference between IW and the total current efficiency may be taken as a memure of the evolution of hydrogen. To B remarkable degree (Figure 5 ) , s p parent density of the copper posder can he eorrelsted with total metal current efficicnoy. FLOWRmn, Flow rake hicretmed with increw in wpper w n cantistion. With regard to %id concentration, flow rste reached B maximum at diwt 100 grams oi sulfuric acid per liter (Table 11). Photomicrograph8 of coppcr powder (Figure 0) show that apparent density and Row rate o m be correlated with particle ≊ the nodular form Row8 much faster and has D higher density tfian the fcrnlike dendritic iorm of powder. Copper conoentration influenod particle shape more than any other vsriable, high concentration8 of oopper tending to promote formation of nodular pwticles. SCREENANALYSIS. As shown by Table 11 the percentage of powder finer than 2W mesh decreased with increase in temperature, ourrent density, and oopper concentration.
ACKNOW LEOGMENT
The authors are indebted to the University of Warhingtolr Experiment Station for financial Basistanee in connection with this proieot. Tho suthora also express their sincere ~ppreciationto Jack Finley for suggestions regarding soreening of the copper powders and to Darrell M e r m d T.Rreitmsyer for aasistanra in preparing the photomicmgrspha. LITERATURE CITEU
(I) American Metal Co.. LW..New York. N. Y..trade literature. ( 2 ) Baeas. "A Course in Powder M~tnllurw." New York. &inhold Publishing Corp.. 1943. (3) Comatock. Metal Pmjmaa, 35, 48.5 (193s). (4) Cordiano, T~ona.Elecfrochem. Sac.. 85. 97 (1944). ( 5 ) Furman, "Scott'a Standard Methods of Andysis." 6th mi.. Vol. 1. P. 368, New York. D. Yair Nostrand Co.. Ins.. 1935. (6) General Metals Powder Co..Akron. Ohio. trade literature. (7) Hardy. Chaa., Inc.. New York, N. Y., trade Iiterat~m. ( 8 ) Hothersall and Gerdsm, Mef. I d . (Lowion). 66. 234 (1945). (9)Jones, "Powder Metallrrrw." Landon. Fkiward Arnold Co.. ,097 _""*.
(10) Metsla Refining Co., Division of (iliddw Co.. Hammond. Ind..
trade literature.
(11) Rowmsn, Trana. Elelrochem Btc., 85, I(i0 (1944). (121 Sohumaoher and Souden. Metal8 dllovs. .. 20,. 1327 (19441. (13) Skaupy, "Prinoiplee of Powder M~ialhtigy,"p. 22. N e w i w k .
Philosophical Libraw, 1944.
(14) Wulff, "Powder Metallurgy." p~ M I . Clwrlsnd. Ohio. Am. s i r .
for Matals. 1942. K s c r . w m Dscernbei 8. 1949. Prasantsd Idore the Division of 1nduatri.l end Enginssting Cherniatry, 116th Meeting. A l r s n r c ~Caeurcnb ~ 8ociarr. Ran Pmnciaco, Calif. Based on tberis preacnted by Daniel W. Drumiler i n ~ ~ r t i fulfillmsol sl of the mauir~rneotsfor the degree 01 master 01 ~ e i m in ~ v ahsmicii enzin~lring.University of Washington, 8 ~ * t t l a .Wauh.
Corrections In the artiole entitled "Thermadynnmio Properties of Sulfur" [West, J. R.,IND. ENU.Cmx.,42,713 (1950)1 the third equatioii io the second column of page 715 should r e d :
CONCLUSIONS
Optimum results were obtained when conditions were such that wall amounta of hydrogen were evolved, probably due to insufficientdiffusion of copper ions to the cathode. Factors tending to deerease tho concentration of copper in the cathode film, suoh LB law tempersture, low electrolyk eopper concentration, and high csthode current density, favcrrml the deposition of copper in powder form.
hs
=
0.0. 123P
+ 0.176T t 137.9
lrt the wtiolc entitled "Pure 1 Iydrocarbons from Petroleum" [Griswotd, Chew, and Kleoke, IN^. h a . CHEM.,42, 124651 (1950)l error8 occurred in the subhedings of Table 11, page 1249.
All tabular materid on this page is far the methyloyeloherane system and "methylcyclohexme" should be substituted for "nheptane" wherever the lstter a p p m in the subheads
