SYSTEMS COST-YISISG R O S I S S0.YPS
1G7
PHXSE STFDY OF ROSIS SOA4P-SODI1711CHLORIDE-WATER A%X D R 0SIS S0.1P-S 0DI 1-1 I SI L I C-ITE -ITIT E R SYST E 51S R . C hIERRILL
AND
R d T l I O S D GETTT
Phzladelphia Quartz Company, Philadelphza. PennsylLanza Receit-ed A i c g i t s t 26, 1.947
Rosin and silicates have been used in soaps for many years. The detergent action of silicates and of mixtures of silicates 11-ithfatty acid soaps is well established (for references see 10). Recent studies have been made of the detergent action of rosin, both alone and mised n-ith fatty acid soaps (2, 13, 14, 15). I n order t o overcome the tendency of soaps from ordinary n-ood or gum rosin to darken on aging, the rosin has been refined and made more resistant to oxidation by hydrogenation, dehydrogenation, and polymerization (1, 15). Soaps from dehydrogenated or disproportionated rosin have proved satisfactory as emulsifying agents for GR-S rubber (3). Jlixed fatty acid-rosin soaps usually contain sodium silicates, both t o improve detergency and to harden the soap. The addition of rosin t o a tallow soap stock makes it easier t o add the large amount of sodium silicates justified on the basis of detergency. Possible esplanations are that the rosin increases the miscibility of the soap with silicate solutions or the range of temperatures over n hich the hot soap-silicate mistures in the crutcher solidify on cooling. The purposes of the present investigation of the phase behavior of rosin soap-sodium chloride-water and rosin soapsodium silicate-water systems were t o provide data of value to the manufacturers and users of rosin soap mistures and to attempt to determine the method by n-hich the addition of rosin makes concentrated soap-silicate mistures more readily prepared. The data are also of interest in studying the behavior of high-polymer latex emulsions stabilized b p rosin soaps (6). S o previous systematic study has apparently been published on these systems, although 5IcBain has referred to preliminary unpublished data on sodium abietate (7). Livingston has presented a hypothetical diagram for rosin soap-sodium hydroxide-water systems based on a fen- experimental points, hut primarily b y analogy with the diagrams of 1IcBain and collaborators for fatty acid soaps (6). EXPERI3IEST.IL
The two types of rosin used in this n-ork Ivere a n-ood rosin of S Color grade representing a typical refined 11ood rosin commonly used in yellow laundry soaps and a hydrogenated rosin sold under the trade name Staybelite. Both were supplied through the courtesy of the Hercules Powder Co. The S n-ood rosin had an acid number of 162, and a saponification number of 184 corresponding to an average molecular Iveight of 349 for the sodium soap. The saponification number of sample of the hydrogenated rosin n-as 1’75, giving the corA $
1 Presented at the TiTenty-first Sational Colloid Symposium, n-hich \vas held undcr the auspices of the Division of Colloid Chemistry of the -4nierican Chemical Society a t Palo Alto, California, June 18-20,1947.
responding bodium boa11 an average molecular w i g h t of 343. Samplc 13 ol the hydrogenated rosin hat1 a +aponification number of 159. Its sodiuni soap vas le% soluble in water and more readily salted out by electrolytes. Other characteristics of regular 11 ood and hydrogenated rosin soaps have been p~ihlished ( I , 1.5). The s o a p were made by suponihcation with sodium ethouide in s l e o h l , and dried at 105°C‘. The rodium silicatt, \I a* :I iqgilar comnic~icia1 product of the 1’hil:dclphi:l Quartz Co. It n-us the wme as that used in preyioub phase studiea on ;I typirnl commeiwal mixed m i p , and on sodiiim palmitate. complete unaly been given (10, 11). The stock d i c a t e .;olutioti contained 45.5 per cent wlitts with a silica-to-alkali ratio 1)s \\-eight of 2.46. The sodiiim chloride c 1’. arid the water fre-hly distilled. -411 data w i e obtained by the synthetic nirthotl u h e d in previoub in\ e-tigations i i , (3, 10, I 1 i. lliltureh of soap, \\ rltei. antl sodium chloride, or bilicatr (if iiwlridetl’i, i n 13 x 50 mni. yealed Pyre\ tiilrc, were heated in an oil bath iintil the (#ontentsn-eie completely isotropic a n d honiogeneous. The miltiire I\ 215 then nllo~vedt o cool Both liquid-crystalline and crystalline or amorphous liytlrogenatccl rosin soaps are, in general, more soluble in 0.025 .ITsodium hydroxide than in pure imter. The solubility of crystalline fatty :wid soap is generally reduced by sodium . . hydroxide and salts; that of the liquid-crystalline phase, middle soap, is increased, whereas that of the liquid-crystalline phase, neat soap, is again reduced by sodium hydroxide and salts. The hydrogenated soap is much less soluble than the ordinary wood rosin soap. This reduction in solubility, due mostly to conversion of the unsaturated double bonds of the abietic and pimaric acids and other unsaturated molecules in the rosin to saturated clerjyatiyes, is considerably greater than that, betn-een sodiuni oleate and sodium stearate (8).
171
ROSIX SO IPS
?TSTElIB COST.\ISISG
The more pertinent comparison with sodium linoleate cannot be made, because no phase studies have been made of that soap. The effect of sodium hydroxide on the solution temperatures of 10, 20, 30, and 40 per cent rosin soup systems is given in table 2. The addition of sodium hydroxide to a hydrogenated rosin soap system first increases, and then decreases i t s solubility. The influence of sodium chloride on the solubility of the hydrogenated rosin soap in water is given in table 3 and shown in figure 2. The curves represent the solubility at definite temperatures (i,e., are isotherms) as deduced by linear ThBLE 2
Ej’ect of a l k a l i o n solution tettiperaiures of hiidrogenated rosin soap sijsletns R O S I N S04P
I1
,
1
S O L E T I O X TEXPER4TURE I N
H20
0 001
.v
SaOH
1
0 025
s
SaOH
I 1
0 25 Y
SaOH
XOLE PER CEST EXCESS
0,001
.v
0.025
SaOH
SaOH
.V
0 25 S
SaOH
7.8 3.4 1.9 1.2
0.31 0.13 0.081 0.053
IY’
SaOH
,
1
78 34 20
* Based on moles
of soap in system. from curve C in figure 1. $ Data from curve B in figure 1.
t Data
TABLE 3
S o l u t i o n a n d transatton temperatures f o r hydrogenated rosin soap-sodzuni chloride-Eater s us teins A . Liquid-crystal f o r m s ROSIN SOAP
SaCl
per cent
per cent
59.8 60.3 49.1 51.0 49.1 56.9 4T.8 53.8 64.2 65.5 66.1 66.7 68.2 i0.5 71.5 50.6 60.1
1.01 3.13 1.17 2.07 3.16 2.26 2.01 2.50 2.53 0.95 1.66 0.52 2.00 1.11 2.14 3.80 3.39 -~ -
-~ _ _ _. - -- -
1
S O L U T I O N TEYPEB.4TCRE
“C.
138 118 135 126 > 165 125 116 115 97 120 112 127 100 111 77 117 > 175 -
~
___
172
.
RIDBOGEUITED R O S I S 9OAP
sac:
p e r cexl
46.1 40.4 45.2 35.1 45.4 36.6 30.0 29.6 20.0 20.1
3.88 15.6 3.2s
4.00
T , r n l’,
per
CClll
i .15 I ,0!1 ‘2.55 3.94 1.04 1.IN u.95 2.61 1.03 2.34 2.93
Y. 119 112 11i > 180 115 105 88 99 82
RS
> 168
0.85
1.61 0.4i 2.48
76
on tlic 0 per cent salt u i i y rcprr-enting the ;.oliildity in pure I\ ater viere obtained from curve C of figure 1 . The intercept:, on the 0 per cent wap axis correspond t o the bolubility of sodium chloride in pure ivater, which i- 2 i per cent at GOo(‘. Aliow wbont 40 p i WIII wap wherc a liquid cryst:tl i- the wtiiratiiiq phaqe.
the addition of sodium chloride decreases the solubility of the soap. The liquidcrystalline phase of the rosin soap behaves like the neat-soap phase of the fatty acid soaps in being “salted out” by hodium chloride rather than being “salted in”, as is the other liquid-crystalline phase middle soap. Below approximately 40 per cent, where amorphous or crystalline soap is the saturating phase, the hrst addition of sodium chloride appearq to increase, hilt in general its effect is to decrease, solubility. At lon- soap concentration> the addition of salt results in the formation oi tu-o immiscible ibotropic solut ion3 in the characteridc indentation or “hay region” s h o r n alqo by systems oi the fatty acid boaps.
PIG. 2. Solubility curyes for hytlragctiatcd r a s h soap .Csodium chloride-water systems. Isotherms at 80”,No,13’, antl 150°C. Open circlcs represent compositions forming liquid crystal first on cooling from isotropic solution; filled circles thosc forming a sccontl iiiimisvihle isotropic liquid or niiior~)liousor crystallitic solid. Systenis of composition b e t m e n the upper 125°C. and YOOC. isotherm.; antl approsimately the dotted line are homogeneous isotropic solutions at the tcmperatureq indicated. For compositions above the clotted line the temperature required t o form a homogpnrous iwtropic .;vatem increases rapidly ivith concentration. Systems of lmv roiin yoap antl high salt concentration corresporitling to compositions in the h y region first showed separation of a second immiwihle isotropic liquid on cooling from homogeneous isotropic solution, as (lo the corresponding fatty acid soap syqtems. Hon-ever, rosin soap systems differ by again becoming homogeneous and isotropic on furthcr cooling. On still further
174
R . C . 1IERRILL AXD R h Y M O S D GETTY
cooling they become birefringent, o\ying t o separation of liquid crystal or a colloidal suspension of finely divided crystalline material. TABLE 4 Solutzon a n d transztzon tempcratuies f o r hydrogenated ioszn soap-sodturn chlorzde-0 025 Y s o d i u m h ydroxzde systems ROSIN
Sac1
p e r cefll
p e r cenl
24.8 7.0i 11.0 10.0 4.98 10.0 4.22 34.8 26.1 15.0 5.15 20.4 20.0
2.64 2.3s 2.68 1.98 1.83 1.30 1.60 2.40 2.34 2.15 2.15 2.06
5.05
3.21 3.62 3.75 2.10 3.23
15.1 5.04 30.9 11.7 20.0 4.68 19.8 18.0 4.05 4.11 40.2
2.0s 2.73
-
93
105 150 130 -
114 170 157 140 168 168 133 141 126 119
-
2.14 2.5s 0.73
124 < 20
2.33 0.49
116 86
27.1
1.81
122
30.1 li.4 40.0 14.2 30.0 20.1 48.1 11.!1
0.46
81 116
24.6 32.1 3 . 00
0.27
70
0.57
hO
1.11 1 .os 1.71
82 h7 112
i.14 10.5 ~
2.07
159
1,s; 1.31 2.45 1.31 1.31 1.21 0.62
-
85 92
so
76
-
99 102 97 97
85 85
89 91 -
89 88 94 92 96
112 110 105 100
94
-
-
100 105
83 96 81
97
89
81
90
ss 119 8i s4 106 66
~~
Ihotropic systems \\-hosr composition lies in region5 \\-here systm1s are ordinarily misotropic h a v ~1 ) ~ m reported previously (c.g.,4,l U , :tltho\igh it- is not'
SYSTEMS C O S T l I S I S G R O S I S SO.\PS
175
knoTvn n-ith certainty lvhether thew systems are anomalous or represent isotropic phaie fields. The eyistence of homogeneous isotropic phases which form tn-o immiscible isotropic phases on heating and a birefringent phase on cooling has not previously been reported for colloidal electrolyte systems. Several systems in this region n-ere isotropic when stationary but became definitely birefringent nhen flon-ed back and forth in the tube. The ease with which flon birefringence is observed shoir s the presence of readily oriented anisometric particles or micelles in such systems. The temperatures plotted in the “bay region” of figure 2 are those at which the homogeneous isotropic solution existing at high temperatures formed tn-o immiscible isotropic solutions on cooling. Homogeneous isotropic phases exist over a specific range a t temperatures belon- those indicated only in this region. Isotherms shon-ing the temperatures at Ivhich these systems again become
50
i 0
I
2
3
4
I o N a CI
FIG.3. Solubility curves for h>-drogeriat,edrosin soap-sodium chloride-0.025 S sodium hydroxide systems. Isotherms at 80”, go”, 125’, arid 150°C.
homogeneous and isotropic, and at which a birefringent phase is formed on still further cooling, are of the same general shape as those indicated. In order to see whether the alkalinity of the silicates might be in part responsible for their behavior with soap systems, a portion of the ternary phase diagram for rosin soap-sodium chloride-n-ater mis determined in 0.025 N sodium hydroxide solution instead of pure Tvater. The data are given in table 4 and figure 3. The escess sodium hydroxide based upon the weight of soap varied up to around i . 8 mole per cent for 10 per cent soap. The per cent excess was greatest in dilute solution n-here the degree of hydrolysis is proportionately greater. Figiire 3 shon-s that the added sodium hydroxide contributes t o the salting out of the soaps. The difference in the miscibility of sodium chloride and silicates n-it11 soap systems is not clue to the difference in alkalinity or pH. Figure 4 shon-s the solubility of hydrogenated rosin soap €3 in solutions of a sotliiim si!icate n3th a silica-to-alli:ili ratio of 2.46. The datu are given in table 5 . The diagram is qualitatively similar t o those \vith ?odium chloride, although
per cent
per cent
23.0 10.0 13.5 9.74 28.1 28.3 5.00 6.00 12.9 4.11 20.2 21.1 2 5 .(I 13.9 lS.!) 20 0 10.3 4.03 3 . io 3.76 11,s 32.1
4.75 4.85 5 . TO 5.23 9 . SS 14.0 3.2'2 11 .!I 3 . 30 5.87
I I
I ~
I
I ~
I
I
I
I
10.4 2.14 12.T
12.3 7.2s 1.36 2.26 2.25 8.10 15 .0 1.5.0 11.7 13. Liquid-crystal i'ornw
33.3 69.4 44.2 79.8 39.7 32.i 58.5 TG. 0 59.; 60.3
2.45 6 2h (i5fi 4 Sh
19 b 14.9 18 h 9 73 ~
49.4 42.3 45. f i
30.3 33.7 75.4
I
I I
5 07 12.b 9 . Oti 2 80 14 0 16 :3
8.49
3.34
~
iI i ~
I
i
~
i
I I
__ _ _
-
112
157 14-1 >I63 < 1 0 0 160 139 14B > 163 > 16.3 162
158 130 16" 156 122 144
the data arc not sufficiently numerous t o -how any iricrrxsed soap colubility in low concentrations of silicate. (Note that the scalc of the horizoiltal aui5 of
fignre 4 1s more than four times that of figures 2 and 3.) The slopes of the i-otherni? aho1-e about 32 per cent soap, where liquid c r p t a l is in equilibrium n it11 i-otropic solution, are less than those below this concentration, where arnorphoiis wap is the saturating phase. Figure 4 shows that the "bay region'' \there t n o isotropic immiscible liquids are in equilibrium iq just as pronounced in -ystems with silicate as in those nith sodium chloride. Complete separation of t lirse t n o phases n - a i considerably more difficult in the silicate systems, hov ei-ter. probably owing t o their higher yiscosity. For this reason the isotropic
901
(z
4
i
a-
0
.k 2.46
5 10 15 RATIO SODIUM StLICATE
FIG.4. Solubility ciirvps f o r hydiogenated rosin soap B-1:2.46 ratio sodium silicatewater systcnis The per cent of the 1:2.46 ratio silicate is on an anhydrous basis. Open circles I e111 e m i t compositions forming liquid crystal first on cooling from isotropic solution, filled circles those forming a second imniiscible isotropic liquid or amorphous or crystalline solid. Coinpositions between thc two dotted 150°C. isotherms are hoinogcnous and isotropic at t h a t temperature.
solutions which, in this range of concentrations, probably exist at temperatures lielow n region of two immiscible isotropic phabes nntl above a temperature where n birefringent phase separates, were not completely studied. Since sample €3 of the hydrogenated rosin soap waq used in obtaining the data in tahle 5 . they are not strictly comparable with those in the previous tables and figurec. Data on the silicate system obtained n-ith sample h of the hyclrogenateci rosin qonp. although not sufficiently complete for a phase diagram, do s h o ~ definitely that it is much more miscible than sample B with silicate. For e\;zimpIc, aboiit 1 0 per cent of anhydrous silicatc iq rcqiiiwd to raise the
solution temperature of a 40 per cent sy-tem oi hydrogenated main soap -1 to 125" C., whereas only 6 per cent is needed to raise that of the same concentration of sample B. The miscibility oi these two commercial Yamples of hydrogenated rosin soap with electrolytes varied considerably. The much greater miscibility of silicates as compared uith chloride is even larger than that indicated by comparison of figures 2-4 inclusive. DISCUSsIOS
Although the present data cover systems only u p t o 88 per cent soap, it appears that the addition of \rater t o an anhydrous ro4n soap markedly reduces to a minimum the temperature at which a homogeneous isotropic liquid forms. Further addition of water stabilizes the crystal lattice of the soap, presumably by forming a liquid-crystalline phase, and the system shows a maximum bolution or melting temperature. The minimum occurs for the hydrogenated rosin soap at around 82 per cent and the maximum a t 6'7 per cent, corresponding, on the average, to approximately 3 and 10 moles of water per mole of soap, respectively. For the wood rosin soap the minimum is at around 76 per crnt and the maximum at 63 per cent, corresponding to about 6 and 11 moles of water per mole of soap. The masimum for the hydrogenated rosin soap system is a t least 80' above the minimum, that of the wood rosin soap at least 20". The maximum probably does not represent a stoichiometric hydrate. The flatness of the maximum ancl the fairly large radius of curvature (figure 1) indicate that the hydrate, whether stoichiometric or not, is considerably dissociated in eolution. The change in slope of the solubility curve at the transition from amorphous or crystalline to liquid-crystalline is not so marked as in the case of the fatty acid soaps. This indicates that the btructure of the liquidcrystalline technical rosin soap which consists largely of three-ring compound5 is less abruptly stabilized than that of the long straight-chain fatty acid soaps. The solubility curve in water of colloidal electrolytes which shorv a fairly sharp change indicative of micelle formation in freezing point , conductivity, and other physicochemical properties at a particular concentration also shows a marked change in slope at about this same concentration (Krafft point). The existence of this marked change of slope in colloidal electrolyte systems might be regarded as indicating a "critical concentration" for micelle formation. Our data would then suggest that micelle formation in solutions of ordinary wood rosin soaps occurs very gradually over a range of concentrations, whereas solutions of the hydrogenated rosin would show a ' critica! concentration". Kolthoff and .Johnson ( 5 ) have shown by the dye solubilization technique that a rosin soap differs from fatty acid soap, by not showing a critical concentration. It would be interesting to see if hydrogenated robin soaps show a "critical concentration" by the dye solubilization, electrical conductivity, or osmotic coefficient methods for studying micelle formation. A positive result ~rouldnot be entirely unexpected, since changing the three hydroxyl groups of the threering compound w i i u m cholate t o the ketone groups of sodium dehydrocholate
hThTI':\IS
C O S T . \ I S I S G R O S l S SO 41%
179
converts a typical solubilizing colloidal electrolyte to one which has no solubilizing action (12). One of the practical implications of this work is that the effect) of rosin in making it easier t o incorporate large amounts of silicate in a soap system may lie attributed both to the increased miscibility of the soap with silicate and to providing a range of solidification points for the system. SUMMARY
Solubility curves for the very soluble wood rosin and the less soluble hydrogenated rosin soap in water and, for the latt>er,in 0.025 N sodium hydroxide, show both similarities to and differences from those of long-chain fa,tt,y acid soaps. Ternary diagmms of the hydrogenated rosin soap with sodium chloride in water and in 0.025 IV sodium hydroxide solution are qualitatively similar to those with fatty acid soaps but at low soap concentrations eshibit hit,herto unreported behavior. Large amounts of a sodium silicate with an SiO2/9a2O ratio by weight of 2.46 are incorporated into concentrated hydrogenated rosin soap systems without changing ]very much the phase behavior. Rosin makes it easier to incorporate large amounts of silicates in fatt,y acid soap systems by increasing miscibility and by providing a mnge of solidification t,emperatures for the system. REFERENCES (1) BORGLIN, J. S . ,E~LLIOTT,11. .I., . ~ N DMOSHER, 1'. l t . : Inti. I.:ng. ('hem. 36, 752 (1944). ( 2 ) BORGLIN, J . S . ,~ I O A H E1'. R , It.,XOBLE, BARBAR.*, .ixn I'TNSHON,T. : Oil &Soap 2 0 , i 7 (1943). (31 ('VTHBERTSON, G . I A N I ) (12) ~ I E R R I L L R ,. C'., ANI) h l ~ l 3 . + 1J.~ FV.: , ,J. Phys. C:licni. 46, 10 (1942). (13j I'OHLE,W. D . : Oil &- Soap 17,150 (1910);18,244,247 (1941); Soap 18, 20269 (1942). (141 PCJHLE, W.D., A N I ) S P E H C. , F.: Oil C Soap 17, 100. 214 (1940). (1.51 T-an ZILE, B. S.,ANI)I ~ O R G I . I XJ. , X.: Oil & Soap 21, 164 (1944); 22, 331 (1945). (16) VOLI),11.J.: J. .kin. C'heni. SOC.63, 1429 (1941). ( I .
