September, 1931
I N D U S T R I A L A N D Eh'GI-VEERING CHEMISTRY
of a lubricant. The most desirable lubricant, other things being equal, is one which has a very flat viscosity curve; in ,other words, it is one which possesses the same viscosity at high temperatures as a t the temperature a t which the lubricant is inserted in the valve. This condition, however, is only approximated, and, as a result, lubricants are seldom as efficient on high-temperature services as they are on low. Generally speaking, satisfactory lubricants are available for temperatures up to 500' F. (260' C.). It will thus be seen that an efficient lubricant plays a large part in resisting corrosion. There are also certain services
989
which are quite beyond the range of a lubricated valve; a t least until suitable lubricants can be devised to handle very high temperatures. It is likewise apparent that where conditions are beyond the ability of a lubricant to withstand them, the lubricated valve is no more effective against corrosion than a non-lubricated valve. On the many services, however, where suitable lubricants are available, the lubricated plug valve offers an effective means of successfully combating this corrosion, both through the means of pressure lubrication and the natural ability of the plug-cock type of valve to handle corrosive services.
Value of Rubber Hydrocarbon in Reclaimed Rubber' C. W. Sanderson GOODYEAR 'kRE
AND
RUBBERCOMPANY, AKRON,O H I O
The rubber hydrocarbon of reclaimed rubber is From this analysis the followHE i n v e s t i g a t i o n reevaluated by road tests in a series of stocks using coning was derived to duplicate ported in this article stant composition as derived from analysis of the rethe composition of the reis concerned with the claim. The hydrocarbon from reclaim is at its maxiclaim: e v a l u a t i o n of the rubber % mum value in the 100 per cent reclaim stock where the h y d r o c a r b o n of reclaimed Rubber., . . . . . . . . . . . . . . . 55.00 abrasion is 50 per cent as good as the all-new rubber rubber as measured by resistMineral rubber.. . . . . . . . . . 6 . 1 0 stock. It is not possible to compensate for the degradance to road wear in a tire Pine tar.. ............... 6 . 1 0 ing effect of the reclaim because any method proposed Carbon black.. . . . . . . . . . . 11.00 ltread stock. The work is a Zinc oxide.. . . . . . . . . . . . . . 9.00 can also be applied to the non-reclaim stock with correconfirmation by r o a d t e s t s Clay.. . . . . . . . . . . . . . . . . . . 6 . 5 0 sponding improvement. of that reported by Vogt (5) Whiting.. . . . . . . . . . . . . . . . 4 . 1 0 under this same subject Sulfur.. . . . . . . . . . . . . . . . . . 2 . 2 0 and is Rimilar to previous work by the author (4). The The insolubles were assumed as clay and the balance of the method of constant composition as used by Vogt was emminerals, minus the zinc oxide, as whiting. The acetone ployed in this work. However, the series was carried from 50 per cent to allow for the part of extract was increased by 0 to 100 per cent reclaimed rubber hydrocarbon, instead of mineral rubber not extracted and was assumed to be 50 per cent from 0 to 60 per cent as in Vogt's work. mineral rubber and 50 per cent pine tar. The starting point for the series of stocks used was the 100per Experimental Tests cent reclaim compound. It was derived by adding as much The reclaim used was whole-tire alkali reclaim, and in order carbon-black loading as the stock would stand and still be cat o get an average material the lot used was prepared by select- pable of processing in the factory. No zinc oxide was used in ing daily samples over a period of about 3 months and then this compound, as i t had been found by previous work that its blended. Mixed with 5 per cent sulfur and cured 17 minutes presence in such a compound adds neither to the physical tests at 141.5' C. it gave: nor to the road performance. The composition of this stock Tensile stresgth.. . . . . . . . . . . . . . . . . . . . 55 kg. per sq. cm. (9 in Table I), taking into consideration the ingredients in the Elongation.. . . . . . . . . . . . . . . . . . . . . . . . . 437 reclaim with the exception of the sulfur, was then used to compound the series as given in Table I. Three and a half per cent The chemical analysis of the reclaim was as follows: of sulfur, 4.0 per cent of stearic acid, and 0.75 per cent of Captax % based on the rubber hydrocarbon were constant in the series Sp. gr. . . . . . . . . . . 1.155 and the activating effect of the reclaim was adjusted for by Moisture, . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.46 using litharge in the low reclaim stocks. The black was added Alkalinity (4 hrs.).. . . . . . . . . . . . . . . . . . . 0,008 as a 60-40 master batch with rubber and as a 75-25 master Alkalinity (48 hrs.). . . . . . . . . . . . . . . . . . . 0.007 7.12 Acetone extract.. .................... batch with reclaim. The stocks were judged to have a uniform Chloroform extract. . . . . . . . . . . . . . . . . . . 28.24 optimum technical cure a t 60 minutes a t 126.4' C.
T
Alcoholic potash extract.. . . . . . . . . . . . . . 1 . 0 8 Free sulfur . . . . . . . . . . . . . . . . 0.07 2.47 Combined sulfur.. . . . . . . . . . . . . . . 11.18 Free carbon.. . . . . . . . . . . . . . . . . . . . . . . . 18.55 Ash.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The analysis of ash was: Silica ................................ Iron and adurninurn oxide.. . . . . . . . . . . . . Calcium oxide.. . . . . . . . . . . . . . . . . . . . . . . Magnesium oxide.. . . . . . . . . . . . . . . . . . . . . Zinc oxide.. .......................... Sulfates (SOr).. . . . . . . . . . . . . . . . . . . . . . . . 1 Received
April 6,1931.
% 2.42 2.60 1.37 1.10 9.00
1.21
Physical Tests
Standard methods of testing, as recommended by the Physical Testing Committee, were used except as noted. The tests were made on samples taken from tubed treads. TENSILE STRENGTH-The tensile tests were made with the Goodyear autographic machine. Table I1 shows the tensile, elongation, and moduli (load a t 300 per cent and 500 per cent elongation). The relative values (non-reclaim stock, 100) are shown on Figure 1. The noteworthy fact is that the tensile properties do not fall off until over 15 per cent reclaimed rubber hydro-
INDUSTRIAL AND ENGINEERING CHEMISTRY
990
Table I-Composition Stock 1 Rubber. . . . . . . . . . . . . . 100 Reclaim. . . . . . . . . . . . 0 Carbon black.. . . . . . . . 49.2 Zinc oxide 16.38 Clay.. . . . . . . . . . . . . . 11.56 Whiting. . . . . . . . . . . . 7.46 Mineral rubber.. . . . . . 10.50 Pine t a r . . . . . . . . . . . . . 10.50 Litharge.. . . . . . . . . . . . 0.60 Sulfur. . . . . . . . . . . . . . . 3.50 Stearic acid, . . . . . . . . . 4.00 Captax.. . . . . . . . . . . . . 0.75 T o t a l . . . . . . . . . . . . . . 214.45
-
2 95.0
3 90.0 18.2 47.2 14.74 10.40 6.71 9.45 9.45 0.20 3.50 4.00 0.75 214.60
9.1
48.2 16.56 10.98 7.09 9.98 9.98 0.40
3.50 4.00 0.75 214.54
-
4 85.0 27.3 46.2 13.92 9.83 6.34 8.93 8.93 0.10 3.50 4.00 0.75 214.80
of Series 5 80.0 36.4 45.2 13.10 9.25 5.97 8.40 8.40 0.10 3.50 4.00 0.75 215.07
-
Table 11-Results of Tensile Tests RECLAIMED RUBBERHYDROCARBON
%
7 50.0 91.0 39.2 8.19 5.78 3.73 5.25 5.25 0 3.50 4.00 0.75 216.66
8 25.0 136.5 34.2 4.10 2.89 1.87 2.63 2.63 0
9 0 182.0 29.2 0 0 0 0
0 0
3.50 4.00 0.75 218.07
3.50 4.00 0.75 219.45
Discussion of Results
TENSILE ELONGALOAD STRENGTH TION At 300% At 500% K g . / s q . cm. % K g . / s q . cm.
226 222 230 225 190 180 150 118 84
0 5 10 15 20 25 50 75 100
6
75.0 45.5 44.2 12.29 8.67 5.60 7.88 7.88 0 10 3.50 4.00 0.75 215.37
Vol. 23, No. 9
178 180 178 174 170
590 580 560 566 520 515 470 485 325
carbon is reached, this being in direct contrast to the road results. .kBRASION-LabOI’atOry abrasion tests were carried out by two methods: the Goodyear, called method A by Vogt ( 5 ) ,and the Du Pont abrader. The results are shown in Table 111.
Using the method of Vogt (5)for interpreting the results, Let A = value of abrasion resistance of new rubber hydrocarbon with assigned value of 100 units B = value of reclaim hydrocarbon in same units C = experimentally determined values for abrasion resistance (based on new rubber stock = 100) of various stocks Y = amount of new rubber hydrocarbon as decimal fraction 1.00 Y = amount of reclaim hydrocarbon as decimal fraction. Then A Y B (1.00 - Y ) = C, on assumption that qualities of two types of hydrocarbon are additive.
+
B=-C-AY
Solving
1.00
-
Y
Lsing the road values, Table Vis obtained. Table 111-Results of Abrasion Tests RECLAIMED RUBLoss BY B B R HYDROCARBONGOODYEAR D U PONT % cc. Cc./hp-hv. 19.6 402 0
5 10 15 20 25 50 75 100
19.3 20.3 21.7 22 23.9 28.8 34.4 37.1
377 359 456
481 413 562 685 856
The Goodyear abrasion results (relative) are shown on Figure 1. They check fairly well with the road tests except that here again the results on the 0 to 25 reclaimed rubber hydrocarbon are too high. The Du Pont abrader results between 0 and 25 are very erratic and are not plotted. Road Test
Table V-Values of Reclaimed Hydrocarbon RECLAIM HYDROCARBON B VALUE
%
n
5 10 15 20 25 50 75 100
Neg. Neg.
7 4
16 30 41 50
These results check very well with Vogt’s (5) conclusionnamely, “The value of the reclaimed rubber hydrocarbon varies from 0 when substituted in small percentages, up to a maximum of 50 per cent of the v$ue of new rubber when compounded in large percentages.” There is a close similarity between these results and those obtained in the previous work by the author, even though in that series the composition was not constant.
The stocks were run on a tubing machine and built into twoway treads for 4.50-21 tires. The comparisons were made as follows: 1us. 2, 2 z’s. 3, 3 us. 4, 4 us. 5, 5 US. 6, 6 tis. 7 , 7 us. 8,8us. 9, also 1 21s.4, 4 us. 6, and 6 us. 8. The tires were run in general service, the majority being on Ford cars. The tests were run over a period extending from March to December, 1930. The rating was determined by design height measurements on an average of eight tires per test. Table IV-Results of Road Test RECLAIMED RUBSECONDARY BBR HYDROCARBON R.4TING RATING
% 0
5 10 15 20 25 50 75 100
100 92 87 86 81 79 65 56
100 86
Figure 1-Evaluation
of Reclaimed Rubber Hydrocarbon
78 57
50
The results are quite consistent and the secondary comparison checks the main series. The results are shown graphically on Figure 1.
The relative road abrasion value of the rubber hydrocarbon in the reclaim having been shown, the next question is, what does this value mean when used in practical tread compounding? Bierer and Davis ( I ) , while perfectly clear on the fact that the rubber hydrocarbon from reclaim is inferior to new hydrocarbon, attempted to show that this could be overcome
September, 1931
INDUSTRIAL A N D ENGINEERING CHEMISTRY
or compensated for, when substituting ieclaim for rubber, by taking diluents or excess filler from the rubber stock and by adding reenforcing material to the reclaim stock. They failed t o realize that the same measures which would improve the reclaim tread could be applied to the base stock. If it were true that, due to the plasticizing effect of the reclaim, it would be possible to carry higher black loading in the reclaim tread stock with the same ease of handling, there would be some weight to the argument that the reclaim can be compensated for by adding black. Factory practice does not show this to be the case. On the contrary, the added black must be considerably reduced t o keep the same handling conditions. If i t were possible to process the reclaim stock with higher black, then it would also be possible to add more black to the non-reclaim stock and keep the, differential in road wear. Since this is the case, if the non-reclaim tread stock is taken with no diluent or excess zinc oxide and with as much black loading as can be processed, then it is not possible t o make compensation for the effect of the reclaim. These facts were put forth very clearly by Cranor (g), who better tread can be made without states that than can possibly be made with it." The series in the present paper was not designed primarily
991
to show the extent to which wear will fall off with the use of reclaim in a series of practical tread stocks. However, since no compensation for its effect is possible, the wear in such a series would fall off even faster than in the series in this paper, for in the latter diluent materials were added to the non-reclaim stock. Therefore, it can be said that up to 20 per cent, the use of reclaim will cut down the resistance to road wear by approximately the percentage used. This is essentially the conclusion reached by Holt and Wormeley ( 3 ) . Their method was severely criticized by Bierer and Davis, but considering that their base stock was as stiff and tough as was considered practical at the time, this criticism was not justified and their conclusions were essentially in line with the facts. Acknowledgment
The writer wishes to express his appreciation to W.W. Vogt for valuable suggestions and criticism. Literature Cited Bierer and Davis, I N D . ENG. CHBM.,18, 348 (1926). Cranor, India Rubber Tire Rev., 27, No. 12, 26 (1927). Holt and Wormeley, Bur. Standards, Tech. Paper 294 (1925) Sanderson, I n d i a Rubber W o r l d , SO, 453 (1929). ( 5 ) v o g t , I N D . E N O . CHEM., ao, 140 (1928)
(1) (2) (3) (4)
Extraction of Potash from Polyhalite 11-Produc tion of Syngenite and By- Product Magnesia' H. H. Storch and N. Fragen NONMETALLIC MINERALS E X P E R I M E N T S T A T I O N , UNITED S T A T E S BUREAU OF
MINES,
NEWBRUNSWICK, N. J
A discussion is presented of data concerning the conT h e r a t e of s o l u t i o n of U B L I C A T I O N S by Wroth (7), Stor& @), version of polyhalite (K2S04.MgS04.2CaS04.2Hz0) to MgS04 from minus 30-mesh and Storch and Clarke syngenite (KaSO~.CaSO~.HaO) and the production of polyhalite calcined a t 5OO0C., by-product magnesia by way of the precipitation and using a 10-11 per cent KzS04 (4) have indicated the cornsubsequent thermal decomposition of M ~ C O I . ( N H ~ ) ~ -s o l u t i o n as leach liquor, is mercial p o s s i b i l i t i e s in the COa.4HzO. Processes are suggested for the production fairly rapid, being practically p r o d u c t i o n of K2S04from complete a t theend of 3 hours. Texas-New Mexico polyof either syngenite or K&Od or both. The rate of drop of to halite and have given the results of experiments on the calcination and subsequent leaching the equilibrium value is much slower, about 6 hours being neceswith water a t 100" C. In this paper it is desired to present sary to obtain a 3 per cent KzS04concentration in the mother a discussion of the results of experiments concerning the con- liquor. The solid phase a t the completion of the reaction is a version of polyhalite to syngenite, and the production of by- very h e l y divided powder. Its composition depends upon product magnesia. The detailed, tabulated data upon which the percentage of natural anhydrite present in the polyhalite, this discussion is based have already been presented by the but if it is possible to obtain industrial quantities of polyhalite containing not more than 5 per cent a n h ~ d r i t ethe , ~ syngenite authors ( 5 ) . The equilibrium diagram at 25" C. (2) for the system product would contain about 50 per cent K2S04,5.2 per cent K'-Mg+ +-Ca '-S04---Hz0 indicates that syngenite (PO- HzO, and 44.8 per cent CaS04. The potash content of this tassium calcium sulfate monohydrate) is stable in the presence product is completely n-ater-soluble, and it should be a desirof a concentrated MgS04 solution, the KzSO, concentration able potash fertilizer, as the CaS04is a common constituent of being comparatively low (2.6 per cent). Hence, it is to be mixed fertilizers. Some mixing tests conducted on 5-pound expected that, when calcined2polyhalite is leached with water to 10-pound batches of syngenite by the laboratories of one a t 25" C., a mixture of syngenite and gypsum will constitute of the largest mixed-fertilizer companies indicate that this the solid phase. If, however, a leach liquor containing product is suitable for the production of mixed fertilizers. sufficient K2S04to combine with the gypsum is used instead Production of K & 0 4 from Syngenite of water, practically pure syngenite is obtained. The liquid phase contains practically all of the MgS04 from the polyhalite I n one of the processes to be described below, KzS04 is as well as any soluble impurities, such as NaCI. The solid phase will also contain any natural anhydrite and other produced by the conversion of calcined polyhalite to syninsoluble materials present in the polyhalite, since the former genite, and subsequent leaching of the latter with 3 per cent material reacts only very slowly with KZSC)4 solutions. a The average of core samples from a number of wells was between 5 and
P
I Received May 6, 1931. Published by permission of the Director, U. S. Bureau of Mines. (Xot subject to copyright.) 2 The uncalcined material reacts too slowly for industrial purposes See Storch ( 3 ) for rate of reaction of uncalcined polyhaliti: with €120 a t
25'
C.
10 per cent based on the quantity of polyhalite present (i. e., excluding soluble impurities such as NaCI). The actual natural anhydrite content of the run of mine material will be of considerableimportancein the production of syngenite, unless the rate of the reaction between such anhydrite and KiSOa solutions can be increased by catalytic agents or very fine grinding.
