OCTOBER, 1936
ISDUSTHIAL .iSD ENGIh-EEHING CHEMISTRY
well knolin that the type of pigment and ita particle size are important factors in determining the quality of a paint or enamel. Tlie following data show that the type of resin is also an important factor.
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229 2oo
so
160 FIGCRE 1 hen-c: the characteristics of various resin solutions with titanium dioxide pigment. I n all cases 140 the repinq studied were made u p with mineral spirit.., the I20 qolution containing 50 per cent solvent and 50 per cent resin. Five gram3 of titanium dioxide were ground in this I00 qtandard r e h solution. The rate of flow of the colloid so was mea>ured in millimeter- on a polished glass plate placed 60 a t 90". At the top of the glass a hemisphere, 0.5 inch (1.27 cm.) in diameter, wa> ground into the plate which ierved 40 a> a receptacle for the paste. 20 I n each of the qeren resin solutions here presented, the flow increabed n ith decreasing concentration of the pigment 0 PER CENT OF DIChlENT IN M I X T U R E in the solution. ;Il-o, the flow wac: greateit in the case of 50 45 40 35 30 the petroleum polnner. . I~IOURE 2. FLOW OF TITANIUM DIOXIDEPIGMEST IN Solvent as well as pigiiient has a marked effect upon this I VEHICLECOMPOSED OF 50 PERCENTRESIS A N D 50 flowing characteristic. I n comparing polar and nonpolar PERCENTSOLVESSO solvents, the results may be quite different, and we cannot predict the f l o from ~ a st'udy of one solvent' alone. The results differ even when cornT.IBLE I. COMP.LRISOK OF TITAXIEM DIOXIDE AND OF LITHOPONE PASTES GROUND WITH BUHRSTONE MILL paring two nonpolar solvents (Figure 2). The alkyd resin gives better results in Solvesso than -Titanium Dioxide PastesQ-Lithopone Faqtes*---Grinding time, Grinding time, it does in mineral jpirits. sec./100 g. sec./100 g . 1st 2nd 3rd 1st 2nd 3rd A comparison was made of tlie settling of grind grind grind Ttiisotlopg grind grind grind Thisotl opy Reail] titanium dioxide pigment in mineral spirit solu1154 6.1 6 . 3 Considerable 1 5 . 6 5.4 5 . 3 Slight Blank tions co 11t a i n i t i g various resins in designated Hydrocarbon 149 8 . 1 6 . 4 Mild 5.1 5 . 3 4 . 8 Mild 184 6 . 3 Moderate 29 2 5.2 5 . 4 Conalderable amounta. Tlie tests were made by thoroughly f~$~6~tep;lenol,c 1y9 6 . 9 Considerable 5.8 5.3 5 . 3 Considerable agitating tlle niixture of piglnent 2nd resin soluCoumarone indene 952 5.8 6 . 1 Considerable 8 9 . 5 5.0 5 . 2 >loderate 1000 grams of pigment and i 5 0 grams of vehicle ( r a n linseed oil $. 1 per cent i'esui + tion in 50-cc. graduates, allowing the inixture to stand, and measuring tlie Fettling in iiiillimeters r F ~ ~ ~ ~ $:Illd ? ~~500, ;grarnb ~ of \-chicle ~ ~ linseed ~ $-~ 1 per.$c e l i f l e i , l l 1 per cent mineral ' p i r l t * ) , a t l-arioi1.q time interval$. K i t h some resin -~ ~ _ _ qolutions an i n c r e a s e in resin concentration increases the amount of settling; with other -4sIJIPORTAKT cost item in the production of paint? resins an increase ill resin Concentration decreases the settling. and enamel. is the power co.?ts required for t.he grinding The results obtained with mixtures containing one grain operations. Table I show> the results obtained by grinding of resin are slioir-11 in Figure 3. -411 of the resin solution. titaniulii dioxide pigment n.ith a vehicle composed of ranshow increased settling time; the rate of settling, while linseed oil, containing one per cent resin and one per cent different in each specific case, follows curves of h i i l a r type. mineral spirits. The rerults record the grinding time in The exception to this general rule is ro5in ester, n-hicli proseconds necessary t o put 100 grams of the mixture through ceeds along a curl-e of normal type for approsiniat'ely 20 the Huhr stone mill. Saturally, the grinding tinie for the minutes, when it suddenly jumps t,o almost complete prefirst grind is more significant than the grinding time for s w cipitation. This lieliavior iiiay he due to a chemical reaction ceediiig grinds, which are approxiinately the same. hetween the resin and the pigment. The data on litliopone (Table I) were olitained in the same m y . The outstanding difference 24C 5hoWn in this series of teits is the behavior oi 2a ro3in ester. Its wetting properties are comparable to those of the hydrocarbon resin when used Zoo to grind titanium dioxide, but it iq one of the 180 poorest wetting agent. when used with lithopone. 160 The extent of deflocculation or dispersion ( 3 ) of pigments in pure organic liquids depends upoii 140 the polarity of the liquids. Sonpolar liquids I20 gire flocculated -uspensions of large volume, arid polar liquids give varying degree of deIC€ flocculation or dispersion, which is dependent so upon the degree of polarity of the liquid. Since 60 the hydrocarbon resins diswlved in some nolipolar solvents ihow marked influence on the 40 settling and dispersing of titanium dioxide, it i> 20 difficult to explain this phenomena in the absence of a pronounced polar group on the polymer. 0 50 45 40 35 M 25 However, Lowry (1) showed that double bonds may he regarded as polar groups. If the dispersl'I(rVRE 1 FLOW OF TITANIUM DIOXIDEP I G M E S T I S A VEHICLE CoXPOSED OF 50 PER CEXTRESINASD 50 PERCENTMISERALSPIRITS ing effect of the hydrocarhon resin is due to the
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43
INDUSTHIAL AND EKGIi$EERlXG CHEMISTRY
1176
VOL. 28, NO. 10
60
50
40
30
20
10
240
230
22C
210
200
190
160
FIGURE 4. SETTLING CHARACTERISTICS OF HYDROCARBON RESIN COMPARED WITH IODINE NUMBER 0
20
10
0
FIGURE 3.
30
40
50
OF TITA~TIuM DIOXIDEPIGMENT SPIRITS CONTAINIKG VARIOUSRESINS
SETTLINQ
IN
MINERAL
polarity of the carbon-to-carbon double bond, the settling of titanium dioxide in a nonpolar solvent containing a hydrocarbon resin may vary with the unsaturation of the resin. Hydrocarbon resins of varying degree of unsaturation were prepared from petroleum hydrocarbons by controlling the polymerizing conditions. Settling tests were made with each of the resins prepared, using a mixture of 3 grams of a 50 per cent resin solution in mineral spirits, 12 grams of mineral spirits, and 5 grams of pigment. The settling increased with increasing iodine number of the resin until an iodine number of approximately 180 was reached (Figure 4). A further increase in the iodine number beyond this point re-
sulted in a decrease in the rate of settling. This behavior may be due to the influence of a second factor-namely, molecular weight-which steadily decreases with increasing iodine number under the method of polymerization employed.
Literature Cited (1) Lowry, T. M.. J. Chem. SOC.,123, 822 (1923). (2) Polanyi, M., Umschau, 34, 1001 (1930). (3) Ryan, Harkins, and Gans, IND.ENQ.CEEM.,24, 1288 (1932). (4) Thomas, C. A., and Carmody, W. H., J. Am. Chem. Soc., 54, 2480-4 (1932); 55, 3854-6 (1933); IND. ENQ. CHEM.,24, 1125-8 (1932): U. S. Patents 1,836,629. 1,939,932 (1933): 1,947,626, 1,982,707, 1,982,708 (1934); 2,023,945, 2,039,363. 2,039,365,2,039,367 (1935) ; Canadian Patent 333,230 (June 13, 1933); British Patent 340,001 (March 12, 1931). ( 5 ) Thomas, C. A . , and Marling, P. E., ISD. ESQ. CHEM., 24, 871-3 (1932). RECEIVED September 15, 1936
(End of Symposium)
Improved Method for Electrodepositing Alloys H. KERSTEN
AND
WM.T. YOUNG
University of Cincinnati, Cincinnati, Ohio
W
HER the anode in an electroplating bath is an alloy, the metals of which it is composed do not usually dissolve in the correct proportion to produce a deposit with the same composition as the anode. I n some cases a deposit of the desired composition may be obtained by using an anode whose composition has been properly altered; in other cases frequent additions of salts of the metals which become depleted are made. In the improved method,' described here for nickel-iron alloys, the bath is kept saturated with respect to a salt of one of the metals (in this case, nickel formate), and the salt of the other (ferrous sulfate) is added continuously or a t frequent intervals. An insoluble anode is used, and the p H of the solution is kept constant by frequent additions of a neutralizing substance or by passing the electrolyte continuously over a solid 1
U.8.Patent
1,924,439 (1933).
neutralizing substance. With this method a number of alloys may be electrodeposited more conveniently and with a more uniform composition over a period of time, than with some of the older methods. The process is limited to those cases where one of the metals can be electrodeposited from a saturated solution, where the solutions do not react disadvantageously with each other chemically, and where a suitable neutralizing substance can be found. The apparatus is illustrated schematically in Figure 1: The electrolyte was contained in a one-liter beaker, immersed in a water bath whose temperature was held at 50" C. The electrolyte was siphoned from the bath t o a flask containing calcium carbonate which acted as a neutralizing agent. This agent was chosen because it is insoluble in water and therefore could not cause an excess of alkalinity, and because, as will be shown later,
