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formed on their surfaces. This material tended to flake off as corrosion proceeded. All bronzes tested corroded sufficiently under all conditions used to cause considerable contamination of the vinegar with heavy metals. Since the contamination of foods with heavy metals is undesirable, it is inadvisable t o use any of the bronzes tested in the vinegar industry, and it is particularly inadvisable to use the three containing a high percentage of lead.
799
LITERATURE CITED (1) Benik, Korrosion u. MefaZZschutz, 5 , 247 (1929). Food I & , 1, 559 (1929). (2) Mrak and (3) Philip, Trans. Faraday SOC.,11, 244 (1915). (4) Rawdon and Groesbeck, Bur. Standards, Tech. Paper 367 (192s). (5) St* Metazs & A z z o y s ~ 242 (6) Seiler, Gerber, 55, 209 (1929).
cruess,
January 23, 1932,
Some Studies in the Fat-Liquoring of Chrome Leather 11.
Effect of Various Oils upon Oil Adsorption and Strength of Leather
EDWINH . THEIS,Department of Chemical Engineering, Lehigh University, Bethlehem, Pa., S. HUNT,Research Laboratories, Hunt-Rankin Leather Co., Peabody, Mass.
AND
FRANK
S -4 p r e v i o u s p a p e r the
1. Raw n e a t ’ s - f o o t oil and Characteristic oil-adsorption curves are obs u l f o n a t e d neat’s-foot oil, the writers discussed the effect tained f o r various mixtures of raw and sulfonated mixtures varying from 100 per of hydrogen-ion concentracent raw oil to 100 per cent suloils used in the fat-liquoring of chrome-tanned tion upon oil adsorption and fonated oil. calfskin. I f is shown that the percentage of showed that, as the p H value of 2. Raw cod oil and sulfonated sulfonated oil added to raw oil drasiically the skin or fat liquor varied, the cod oil. amount of oil adsorbed by the 3. Raw cod oil and moellon affects the amount of oil adsorbed by the leather. oil. chrome leather varied also. I t The efeci of p H ralue, the oil concentration, 4. R a w neat’s-foot oil a n d was further shown that each ins u l f o n a t e d castor oil, the fat and stability of the f a t liquor upon the oil addividual fat liquor gave a charliquors being adjusted to pH 4 and sorbed during the period qf fat-liquoring are acteristic absorption curve over pH 9. giuen. A comparison, with relation to oil 5. Raw cod oil and sulfonated a pH range of 1 to 12. If a mixc a s t o r oil, t h e r e s u l t i n g fat ture of oils was used, the charadsorpfion by the leather, of some sixteen different liquors being adjusted to pH 4 and acteristic curve of the pure oil f a t liquors is shown. The effect of moisture conpH 9. was changed in proportion to 6. Sulfonated cod oil and salted the chrome leather upon oil adsorption tent of the mixture used. egg yolk, adjusted to pH 4 and is given. pH 9. The experimental work was 7 . Raw c a s t o r oil a n d sulextended to include the followfonated castor oil. ing effects: mixtures of raTv and sulfonated oils upon oil 8. Raw neat’s-foot oil and egg yolk. adsorption and ultimate strength of the leather; moisture in 9. Temperature of fat-liquoring upm oil adsorption and releather before fat-liquoring upon oil take-up and strength of sultant strength of leather. finished leather; and mixtures 10. Comparison of sixteen different and varied fat liquors. of different oils upon oil adsorp11. Effect of pH, oil concentration, and stability of fat liquor tion, strength of leather, and dis- upon oil adsorption and ultimate strength of finished leather 12. Effect of skin moisture and degree of washing before fatt r i b u t i o n of oil throughout the liquoring upon oil adsorption. skin.
EXPERIMENTAL PROCEDURE Chrome-tanned calfskin, direct from shaving, was cut into pieces, 2 X 4 i n c h e s , and fat-liquored in the oil e m u l s i o n s to be noted a t 120” F. (48.9’ C.) a n d for 30 minutes. ilt the duration of the fat-liquoring period, the skin mas removed and dried slowly (room temperature:, and the oil adsorbed was determined, using bP L R C20f N T S U40L F O Nb0A T t D BOOIL !OG’ low-boiling p e t r o l e u m ether as FIGURE1. EFFECTOF t h e e x t r a c t i v e . At the same MIXTURESOF SULFON- time the tensile s t r e n g t h a n d ATED A N D R ~ NEAT’Sw the tearing strength of the fatFOOT OJL ON OIL liquored leather were determined. ADSORPTION AND STRENGTH OF FINSHED The following s l s t e m s were studied: LE.4THER
When raw and sulfonated oils are mixed, and c h r o m e l e a t h e r is fat-liquored in such emulsions, the oil adsorption and strength of the l e a t h e r v a r i e s with the m i x t u r e . Figure 1 shows the effect upon strength n e c e s s a r y for tear and upon oil adsorbed, of mixtures of raw and sulfonated n e a t ’ s - f o o t oil. It is r e a d i l y seen from Figure 1 that with raw n e a t ’ s - f o o t oil a l o n e the oil adsorbed by the chrome leather is v e r y small, b u t , a s t h e p e r c e n t a g e 9f s u l f o n a t e d oil added increases, the oil adsorbed becomes i n c r e a s i n g l y greater, p r o b a b l y b e c a u s e of t h e in-
10
PER
40 60 80 100 CENT SULFONATED OIL
FIGURE2. EFFECTOF MIXTURES OF SULFONATED AND RAW COD OILS ON OIL ADSORPTION AND STRENGTH (TEAR) OF
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INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
Vol. 24, No. 7
50 per cent moellon. The tensile strength of the leather, however, attains its maximum value a t 75 per cent moellon. Figure 4 gives the graphical data obtained when mixtures of raw neat's-foot oil and sulfonated castor oil are used for the fat-liquoring of chrome leather. At both pH 4 and 9 the oil adsorbed rises to a maximum value a t 25 per cent sulfonated castor oil. At pH 4 the oil adsorbed is greater than in the more alkaline system of fat liquors. The tear test is greater at pH 4 than a t pH 9; in the case of the fat liquor a t pH 4, this test shows a maximum value a t 75 per cent sulfonated castor oil. With regard to the tensile strength of the leather, a t high concentrations of raw neat's-foot oil, the fat liquor of the higher pH value shows the greater strength, while the reverse is true at higher concentrations of sulfonated castor oil. It would appear that the alkaline fat liquors, made up of mixtures of raw neat's-foot and sulfonated castor oils, show a lessened oil adsorption and tend to yield a somewhat weaker I I 0 20 40 60 a0 100 I PER C E N T MOELLON leather. 0 20 4a bo 80 MO FIGURE3. CHARACTERISTIC PER CENT SULFONATEDCASTOR OIL Figure 5 shows the data obtained using mixtures of sulOF FAT-LIQUORING, FIGURE4. OIL ADSORBED, fonated castor oil and raw cod oil. I n this case, again, there CURVES USINGRAWCODAND MOELTEARSTRENGTH, AND TENLON OILS SILE STRENGH, USINGSYS- is a greater adsorption using acid fat liquors than alkaline ones. In both cases the oil adsorDtion reaches a maximum value TEM NEAT'S-FOOTOILSULFONATED CASTOR OIL at a 50 per cent concentration. The tensile strength of the r e s u l t i n g leathers s h o w s c r e a s e d s t a b i l i t y of the that the acid fat liquors are emulsion formed, and of the strongest when the raw cod combination of the evapooil predominates, while the rated oil with the leather. a l k a l i n e fat l i q u o r s are With regard to the strength s t r o n g e s t when the sulof the l e a t h e r under such fonated castor oil is in extreatment (measured by the cess. The tensile strength t e a r t e s t ) , t h e strength curves show that, in either first i n c r e a s e s , then deacid or alkaline condition, creases rapidly, until a t 100 m i x t u r e s of the oils are per cent sulfonated oil the stronger than either single leather s t r e n g t h is below component. that of 100 per cent raw When chrome leather is neat's-foot oil, even though fat-liquored with mixtures the p e r c e n t a g e of oil adof sulfonated cod oil and sorbed is g r e a t e r a t that salted egg yolk, an entirely point. This indicates that different p i c t u r e r e s u l t s . the amount of actual oil adI n the first place, the adPCR CENTSULFONATEO CASTOR OIL sorbed is no criterion of uldition of even very small FIGURE5. CURVESFOR SYStimate strength of finished amounts of egg yolk retards 6. EFFECTOF ADDITEM RAW CODOIL-SULFON- FIGURE leather. When a mixture TION OF EGGYOLKTO SULthe adsorption of oil. There ATED CASTOR OIL of raw cod and sulfonated FONATED COD OIL is little difference in oil adcod oils are used in the fatsorption between fat liquors liquoring a somewhat different picture results (Figure 2). As in the case of the system raw neat's-foot oil-sulfonated neat'sfoot oil, the addition of sulfonated cod oil results in an increased oil adsorption which reaches a maximum value at about 50 per cent sulfonated oil. The strength of the leather in all cases is higher when sulfonated oil is added to the fat liquor, but reaches a maximum value a t 50 per cent sulfonated oil. Figure 3 shows the characteristic curves obtained when chrome calfskin is fat-liquored in various mixtures of raw cod oil and moellon. At pH 4 (natural pH of the fat liquors of this mixture) there is a steady rise in oil adsorbed as the percentage of moellon in the fat liquor increases. At pH 4 there is very little change in the tear of the leather. The tensile strength, however, changes, rising to a maximum value a t 75 per cent cod oil and 25 per cent moellon, then decreasing OIL ADSORBED sharply as the percentage of moellon further increases. At pH 9, however, an entirely different system results, since the 0 20 40 LO 80 io presence of alkali tends to disperse the oils more readily. PEP CENT SULFONATED OIL 0 PER 20 CENT 40 EGG 6 D YOLK 60 100 The oil adsorbed rises to a maximum value.of 50 per cent FIGURE8. EFFECTOF moellon and then decreases sharply. The strength of the FIGURE ADDITIONOF SULFON7. EFFECT OF ADleather, as measured by the tear test, follows the same general ATED CASTOROIL TO DITION OF EGGYOLKTO RAWCASTOR OIL NEAT'S-FOOT OIL trend as that of the oil absorbed, rising to a maximum value of
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at pH 5 or 9. At pH 5 the strength of the leather (either tear or tensile) is constant, decreasing as the percentage of egg yolk increases. At pH 9, however, the strength of the resulting leather increases up to 50 per cent egg yolk. The data obtained are shown graphically in Figure 6. Figure 7 shows similar data for the system raw neat's-foot oil-egg yolk. In this case, again, egg yolk apparently retards the oil adsorption. The l e a t h e r , h o w e v e r , is strengthened up to a concentration of 25 per cent egg yolk. From the results obtained and shown in Figures 6 and 7, it would appear that the addition of salted egg yolk retards the adsorption of oil by the c h r o m e l e a t h e r . It was pointed o u t in a p r e v i o u s paper that oil adsorption is retarded a t certain hydrogenionconcentrations. This contention is s t r e n g t h e n e d in this work. Figure 8 shows the adsorp FIGURE9. EFFECTOF TEM- tion of oil from mix%ures of PERATURE ON OIL ADSORPraw and sulfonated castor oils. TION As s u l f o n a t e d castor oil is added, the oil adsorption increases t o a maximum, and, as greater amounts of sulfonated oil are added, the oil adsorption decreases rapidly. The maximum tear strength is attained a t 75 per cent raw and 25 per cent sulfonated castor oil.
EFFECTOF TEMPERATURE UPON FAT-LI QUORING Chromed calfskin is usually fat-liquored a t an initial temperature of 100' to 120" F. (37.8' to 48.9"C.), and it was of interest to determine just what role temperature plays with regard to oil adsorp tion and leather strength. F i g u r e 9 shows the data obtained for a temperature interval ranging f r o m 70" to 180" (21.1" t o 82.2" C.). It is readily seen that, as the temperature in-
8 2
+
s o r p t i o n a l s o increases; beyond this point, however, the
FIGURE10. RELATIVECOMPARISONest t e n s i l e and tear OF SIXTEEN DIFFERENT FATLIQUORS, strength are attained; INCLUDING RAW AND SULFONATEDboth of' these factors OILS, MOELLON, AND SOAP decrease rapidly b e y o n d 80' F. (26.7' C.). It would appear that increasing the temperature (up to 120-140" F., or 48.9-60" C.) favors oil adsorption, but such treatment has a tendency to give tender leather. COMPARISON OF VARIOUS FATLIQUORS Some sixteen different fat liquors were used for a relative comparison of oil adsorption and resulting strength of leather. The fat liquors used were similar to those in regular use in tannery practice. Figure 10 shows the data obtained. The curves were plotbed in relation to a decreasing tensile strength,
and it is to be noted that, in general, the oil adsorbed and the tear strength bear little relation to each other. It is generally found that leather fat-liquored with a sulfonated oil is decidedly stronger with regard to tear a n d t e n s i l e strength than a correspond$l!%z
80 1
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