I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
1598
Koepsell, H. J., Tsuchiya, H. M., Hellman, N. N., Kazenko, A., Hoffman, C. A,, Sharpe, E. S., and Jackson, R. W., J . Biol. Chem., 200, 793-801 (1953).
Koepsell, H. J., Tsuchiya, H. M., Hellman, N. N., Kazenko, A., Sharpe, E. S., Hoffman, C. A,, and Jackson, R. W., Bacteriol. Proc., 52nd mtg., p. 23 (1952). M f g . C h m i s t , 23, 49-55
2 952).
Nadel, H., Randlea, C. i s and Stahly. G. L., A p p l . Microbial., 1, 217--24 (1953).
Nelson, N., J . Biol. Chenz., 153, 375-80 (1944). Senti, F. R., Hellman, N. N., Ludwig, N. H., Babcock, G . E., Tobin, Robert, Glass, C. A,, and Lamberts, B. L., J . Polymer Sci., in press. Simha, R., Research NatL B u r . Standardst 42, 409-18 (1949). Tsuchiya, H. M., Hellman, N. N., and Koepsell, H. J., J . Am. Chem. Soc., 75, 757-8 (1953). Tsuchiya, H. M., Hellman, N. N., Koepsell, H. J., Corman, J., Stringer, C . S., Rogovin, S. P., Bogard, M. O., Bryant, G.,
Vol. 47, No. 8
Feger, V. H., Hoffman, C. A., Senti, F. R., and Jackson, R. W., Ibid., 77, 2412-19 (1956). (19) Tsuchiya, H. M., Koepsell, H. J., Corman, J., Bryant, G., Bogard, M. O., Feger, V. H., and Jackson, R. W., J . Eacteriol., 64, 521-6 (1952). (30) U. S. Military Medical Purchase Description, No. 4, Sept. 19, 1952, Stock NO. 1-161-890, Dextran Injection, M-1 S%, 500 cc., Armed Services Medical Procurement Agency, Brooklyn 1, N. Y . (21) Wolff, I. A., Illehltretter, C . R., Mellies, R. L., Watson, P. R., Hofreiter, R. T., Patrick, P. L., and Rist, C. E., IND.ENG. CHEM.,46, 370-7 (1954). RECEIVED for review May 10, 1954. ACCEPTED January 20, 1955. Presented before the Division of Carbohydrate Chemistry, Symposium on Dextran, at the 125th Meeting of the AMERICAN CHEMICAL SOCIETY,Kansas City, Mo.. March 1954. The mention of firm names or commercial products does not constitute an endorsement of such firms or products by the U. 5. Department of Agriculture.
END OF PRODUCT AND PROCESS DEVELOPMENT SECTION
New Polymeric Dispersants for Hydrocarbon Systems C. B. BISWELL, W. E. CATLIN, J. F. FRONING, AND G. B. ROBBINS E. I. du Pont de Nemours & Co., Wilmington, Del.
L
I T T L E fundamental work has been done on the behavior of surface-active agents in nonaqueous media. However, a variety of additives of this type has been used empirically in connection with painta, printing inks, dry cleaning and numerous other applications. I n general, these surface-active materials have been solvent-soluble modifications of the anionic, cationic, or nonionic types which have proved effective in aqueous systems. A rapidly growing demand for such additives has been found in the lubricating oil and fuel oil industries. Lubricating oil detergents have been principally oil-soluble sulfonates of various types although alkaline earth phenates have also been employed. Such additives have been extremely effective in promoting engine cleanliness under the high temperature conditions which exist in Diesel and spark-ignited engines during heavy-duty performance. Under the low temperature conditions that exist for most passenger cars during city driving conditions and for stop-and-go delivery service, these detergents are effective only when used in high concentrations. This fact has spurred the search for novel additive types that are more effective under this critical, but widespread, type of service. The broad class of oil-soluble surface-active agents described here is a result of that search. These compositions can be broadly characterized as polymers containing basic nitrogen substituents. They are actually copolymers of two monomer types which have distinct and separate functions. One type of monomer is predominately nonpolar. It has the function of contributing the property of solubility in oil to the polymer and is referred to as a n oleophilic monomer. The other type of monomer contains basic nitrogen. Its function is to contribute surface activity to the polymer through nonionic or cationic mechaniems and to act as the point of attraction for polar materials such as the sludge in fuel oil or lubricants. I n certain cases i t is possible t o add other relatively nonpolar mpnomers which d o not contribute to either the oleophilic nature or to basicity but act as innocuous extenders of the polymer chain. The ratio in which these different func-
tional types of monomers exist in the copolymer has a great influence on its properties. A variety of monomer structures can fulfill these different functions. Esters or amides of methacrylic and acrylic acids or polymerizable polycarboxylic acids, vinyl esters of carboxylic acids, vinyl ethers, or vinyl-substituted aromatic compounds are among the structuraI classes of monoiners that can be employed. Such a polymer might be represented for a simple vinyl system by a general formula:
-CH-CH2-CH-CH2-CH-CHz-CH--CH2-CH-CHS I
1
I
I
where 0 is a n oleophilic group, B is a basic group, and L is a group of atoms linking an 0 or B group t o the polymer chain Different radicals which may function in these different relations are as follows : 0 --CnHzn
L
B
+1
-(
CHz),--NRz
( m = 2 or more)
(n
=
8 or more)
-C-NHII
a -0(direct bond for aryl compounds -e.g., styrene)
INDUSTRIAL AND ENGINEERING CHEMISTRY
August 1955
Copolymers that indicate some of the compositions that were studied are given with weight ratios of the monomers:
Oil-soluble polymers containing basic nitrogen are effective
W t . Ratio of Monomers
Copolymer Hexndecyl ii.etliac~ylate.'dietli~lun.inoetI.yI n.ethitcrylnte Dodecyl methacrylate 4-vinyIpy4dinr ti'ethacrylatc Dodew1 tl.etlincr).late rr,.f-o~tyl4minoetl,yl Dodecyl fumarate/diethylaminoethyl methacrylate Vinyl laurate/vinyl diethylaminoethyl ether Decvl acrvlate/4-dimethvlaminomethvlstvrene
80:20
scrylamide Dodecyl methacrylate/styrene/dibutylaminoethyl methacrylate
90: 10
1599
. . . in promoting passenger car engine cleanliness . . . in stabilizing fuel oil
90:10 80 :20 95:5 9O:lO 95:5
80 :20 90:10
60:30:10
2. The incorporation of the basic groups in a polymer imparts unique properties that do not exist in nonpolymeric bases (comparison of tests B and G with D and E). 3. The neutralization of the basic group does not destroy its suspending properties (comparison of tests B and G).
Although we were not able to give the molecular weights of these polymers, the polymers are effective over a broad molecularweight range as determined by testing products with greatly differing viscosities. Monomers of different types (with different 1, groups) can be used in the preparation of a copolymer. The relative rate of polymerization of the different monomer types is the only factor limiting the formation of the copolymers. These copolymers possess properties that make them unique with respect to other oil-soluble polymers as well as to the common oil-soluble dispersants. Representative compositions have been studied in simplified systems which emphasize the surface activity, suspending action, and solubilizing properties of this group of polymers and demonstrate the effect of changes in composition upon these qualities.
Another noteworthy point is the insensitivity of the suspending action of the basic polymer to water in contrast to the failure of barium petroleum sulfonate to suspend carbon in the presence of moisture. This leads to speculation as to whether the relatively poor performance of sulfonate additives for luhricating oils under low temperature conditions may be related to the normal presence of condensed water in the crankcase.
Table I. INTERFACIAL TENSION MEASUREMENTS
Suspension of Carbon in Kerosine by Various Surface-Active Agents % Suspended after 4 Daya
The surface activity of these materials has been demonstrated through interfacial tension measurements on water-oil systems using a ring method. These measurements, which were made a t 25" C., show that the interfacial tension of the water-oil system was 37.7 dynes per cm., whereas 4.2% solutions of dodecyl methacrylate/diethylaminoethyl methacrylate (90: 10) copolymer or dodecyl methacrylate homopolymer in oil show values of 25.3 or 32.1 dynes per em., respectively. These data show that the basic copolymer is surface active and that this surface activity is predominantly a result of the basic groups in the polymer.
Test
Additive
A B C
None 0.5% Dodeoyl methacrylate/diethylaminoethyl methacrylate (90: 10) 0.5% Dodecyl methacrylate homopolymer 0.5% Dimethylcetylamine 0.5% Didodeoyl dimethylammonium chloride 0.5% Barium petroleum sulfonate 0.5% Dodecyl methacrylate/diethylaminoethyl methacrylate plus excess acetic acid
D
E
F
G
Dry 60
With 0.5% water 50
100
100 45 50
50 50
100
45
40 46
100
in0
SOLUBILIZING ACTION SUSPENDING ACTION
The solubilizing action of the basic copolymers toward engine sludge is unique. This property has been investigated through experiments employing the pentane-insoluble but benzenesoluble fraction of oxidized petroleum oil, a material which is closely related to the organic portion of engine sludge. The test involves the precipitation of this pentane-insoliible material from kerosine in the presence of the additive. The observations which are made on such tests may be visual comparisons of suspensions or solubilization of the material in the tubes or electron photomicrographs OP the tube contents.
The suspending action of these polymers has been studied by means of the settling behavior of dispersions of fine carbon black in ( a ) dry kerosine, ( b ) kerosine containing small amounts of water, or ( c ) solutions of various additives in either wet or dry kerosine. The results of such experiments are given in Table I. These data show that:
1. The basic groups in the polymer are responsible for its suspending power (comparison of tests B and C).
A
B
C
D
Figure 1. Effect of additives on pentane-insoluble sludge in kerosine Electron photomicrographs-1000 X Control (no additive) B. 1 % dodecyl methacrylate/diethylaminoethylmethacrylate (90:lO) copolymer C. 0.2 % dodecyl methacg4ate/diethylaminoethyl methacrylate (90:lO) copolymer D. 170 dodecyl methacrylate homopolymer E. 1 yo barium petroleum sulfonate A.
E
INDUSTRIAL AND ENGINEERING CHEMISTRY
1600
Figure 1 shows such photomicrographs for several different materials. The photomicrographs show clearly that 1% of a dodecyl methacrylate/diethylaminoethyl methacrylate (90 :10) copolymer dissolves the sludge completely and that only 0.270 of the same material partially dissolves it and finely disperses the remainder. A dodecyl methacrylate homopolymer has no effect on the insoluble material, showing that solubilization is brought about through the basic groups of the copolymer. This is true even after these basic groups have been converted t o salts. Barium petroleum sulfonate does not cause such a solubilization. EFFECT OF COPOLYMER COMPOSITION
As was mentioned earlier, the relative amounts of oleophilic and basic monomers in the copolymer have a great effect on its properties. The effect of variation in the amount of the basic groups is shown in a series of experiments similar to those that were used to demonstrate solubilization. I n these experiments, the minimum concentration of polymer which would give complete suspension of the pentane-insoluble sludge was compared for dodecyl methacrylate/diethylaminoethyl methacrylate copolymers of different compositions. The data are recorded in Figure 2.
Table 11. Residue Deposited on Oil Burner Screen by Fuel Oils Aged with and without Copolymer S Copolymer 9, Fuel Oil A
A
B B
Wt. yo
0
10
I
I
I
I
20
30
40
50
I 60
BASIC MONOMER IN COPOLYMER, W T Ye Figure 2. Suspension of pentane-insoluble sludge in kerosine by dodecyl methacrylate/diethylaminoethyl methacrylate copolymers
These data show the great difference in suspending ability that can be brought about by varying the relative amounts of a single pair of monomers. It also gives an indication of the considerable task involved in arriving a t the optimum copolymer t o perform any given function Additives of this type have several recognized practical applications. Various polymer compositions have proved to be optimum for different applications. This merely reflects the differences in the action of different copolymers that have been emphasized in preceding sections. FUEL OIL ADDITIVE
One important use of basic polymers is as a fuel oil additive to decrease the amount of insoluble residue which is formed and to hold the insolubles which are formed in a finely dispersed form. Such additives have become increasingly important with the use of greater amounts of catalytically cracked fuel oils since these fuels are more subject to the development of insolubles which result in decreased filter flow rates or increased nozzle plugging. The dodecyl methacrylate/diethylaminoethyl methacrylate ( 8 0 : 2 0 ) copolymer has proved to be effective in this application. This copolymer, which is referred to in the following discussion as copolymer S, has been shown to be effective in various fuel oils a t concentrations between 0.0015 and 0.1%. Table I1 shows the effect of copolymer S in decreasing the weight of the residue deposited on a 90 x 100 mesh oil burner screen by a 72-hour cir-
Insoluble Residue on Screen, Mg. 177 9 222 25
culation of fuel oils which had been aged in vented containers with and without copolymer S. Fuel oils A and B were lUOyo light catalytic cycle oils from fluid process cracking units. The sulfur content of these two oils was.0.9 and 0.37%, respectively. The effect of copolymer S on the aging of fuel oil A under drum storage conditions is shown in Table 111.
Table 111.
Effect of Copolymer S on Drum Aging of Fuel Oil A Copolynier S,
Wt., %
N P A Color
sf?
~ n g Conditions Months Temp., ’ F. 6 110 6 110 9 Rm. temp. 9 Rm. temp.
-A
None 0.005 None 0.005
Soluble residue, mg./100 ml. Insoluble residue, mg./100 ml.
z n
Vol. 47,No. 8
None
None
ll/z+
0.005
11/2+
None 0.005 None 0.005
10 15 Nil Nil
4
Aging 8 mo.
..
31/*+ 14
mo. 3I/sf 3+ 2:3 0.3
a1/z+ 20 2.6 1.7
10.5
mo. ..
.
26
32 3.4 2.5
.-
12
mo.
J’/z+
4‘/2
44 40
4 2
3 8
These show that copolymer S had no effect on color soluble residue in this fuel oil but that it had a great effect on the insoluble residue. Although copolymer S suppressed the formation of insoluble residue for the first 4 to 6 months’ storage, it showed no effect on the weight of residue after 11 to 12 months’ storage. However, the character of this residue is greatly altered. After 18 months, when both the control and treated fuels showed 9.4 mg. per 100 ml. of insoluble residue, the control fuel rapidly clogged burner screens while the oil treated with copolymer S was essentially nonclogging. I n addition to these effects, copolymer S acts as a dispersant for previously formed insolubles and as a mild antirust agent and is without effect on the ash content or other inspection d:ttn of fuel oil or diesel fuels. LUBRICATING OIL ADDITIVE
Another application for basic polymers is their use as detergente in lubricating oil. A dodecyl methacrylate/diethylaminoethyl methacrylate (90: 10) copolymer, which is called copolymer D hereafter, has proved t o be one of the most effective compositions for this purpose, and it illustrates this application. Copolymer D has proved effective in promoting engine cleanliness under the high temperature conditions of Diesel engines. For example, a mid-continent solvent-refined base oil containing 1.5 weight yo copolymer D and 0.5 weight yG of an antioxidant gave a piston cleanliness score of 88 (where 100 = clean) in a heavy duty test in a Buda Diesel engine, 8.9 compared to an identical score of 88 for a commercial oil meeting MIL-L-2104A specifications. Copolyiner D has proved even more effective in controlling varnish and sludge formation under low temperature conditions such as exist in most passenger cars operating in urban areas or in stop-and-go delivery services, especially during winter conditions. This is in contrast to other detergent types which are very much more effective under high temperature operation than they are for low temperature conditions. The low temperature performance of copolymer D is shown in Table IV. I n this table compositions of SAE 30 Grade containing copolymer D and 0.5% of antioxidant A (the zinc salt of a sulfur-containing acid) blended in a solvent-extracted mid-
INDUSTRIAL AND ENGINEERING CHEMISTRY
August 1955
1601
continent base stock have been compared with comTable IV. Performance of Copolymer D in FL-2 Tests mercial oils B and C and the CRC reference oil N o. 1 Av. REO-7 in Chevrolet engines by the FL-2 procedure. Piston Piston Over-all Over-all Total Sludge These data show the high degree of engine cleanCopolymer D, AO-A, Varnish Varnish Varnish Sludge and Varnish Wt., % W t . yo Ratinga Ratinga Ratingb Ratlngb Ratingo liness that can be attained by compositions 5.3 29 32 61 None 0.5 3.5 employing copolymer D under low temperature 8.6 37 37 74 0.5 7.0 0.3 9.3 41 44 85 0.5 0.5 8.5 conditions. Commercial oil B is an SAE 30 oil 9.3 44 47 91 1.0 0.5 9.0 of high MIL-0-2104 detergency level which has 7.7 31 36 67 5.5 Commercial oil B been recommended for low temperature service. 75 35 40 4.0 6.5 Commercial oil C 5.4 32 41 73 4.5 REO-7 Commercial oil C is a 2-104b 30 oil which is a 10 = clean. b 50 = clean. 100 = ideal rating for total sludge and varnish. composed of the same base oils that had been used in the preparation of the experimental blends. Table V. Performance of Copolymer D in Cyclic Low Temperature REO-7 is a detergent reference oil. Comparison Tests with the performance of these oils emphasizes the 4v. Total contribution of copolymer D. Piston Over-all Over-all Sludge Narrow Slot Copolymer D, AO-A, Varnish Varnish Sludge and Varnish Oil Ring This performance picture is extended by results Wt.. % Wt. % Ratinga Ratingb Ratingb RatingC Plugging, % of the same oil blends in cyclic tests which more None 0.5 5.0 28 35 63 18 closely simulate normal urban driving conditions 0.3 0.5 6.3 32 34 66 9 0 . 5 8 . 1 37 40 77 7 0.5 than do the FL-2 tests. Results are presented in 1.0 0.5 8.3 38 41 79 7 Table V. 5.5 27 34 61 4 Commercial oil B 5.2 27 36 63 21 Commercial oil C These data reemphasize that copolymer D is effective in promoting engine cleanliness under start10 = clean. b 50 = clean. c 100 = ideal rating for total sludge and varnish. and-stop operating conditions. Field service tests have been conducted under low temperature conditions on oils containing copolymer D-type deterimmediately filled with the suspension. Observation was made gents and show good correlation with the laboratory low temafter 4 days. Where water was included, 0.3 ml. of water was perature tests (1). added after the initial mixing time and mixing was continued Although the low temperature detergency of copolymer D is for an additional minute before pouring the sample for observation. remarkable, it is still an effective high temperature detergent. .4n oil blend containing 1.5 weight 7 0 of copolymer D The tests employing pentane-insoluble oxidized petroleum oil and 0.5 weight yo of an antioxidant gave a piston score of 86 were performed by the following procedure: in the standard CRC L-1 Diesel test as compared to scores of Pentane-insoluble material from Underwood oxidation testa 78 to 90 obtained on commercial oils meeting the 2-104B speciwas washed carefully with pentane and reprecipitated from a fication. filtered benzene solution. -4 benzene solution of this material I n regard to other pertinent performance features, copolymer was prepared which contained 2.5 grams of pentane-insoluble material per liter of solution. Twenty ml. of this solution was D has been shown to be relatively innocuous in its effect on bearmixed with 10 ml. of kerosine or the kerosine solution of the addiing corrosion. I n L-4 tests, blends containing copolymer D and tive in a 100-ml. beaker. A set of four to eight such beakers normal amounts of most commercial lubricant antioxidants give was heated a t 97' to 100" C. in an oil bath while the contents clean engines with no more than the normal amount of bearing were agitated (by wire loops suspended from a plate that was raised and lowered by a shaft to a belt-driven eccentric). Over a corrosion as shown in Table VI. period of 30 to40minutesthe benzenewasevaporatedleavin afinal By virtue of its polymeric nature, copolymer D acts as a visof 8 to 10 ml. in the beakers. The contents of t h e t e a k e r volume cosity index improver in lubricating oils. For example, the visincluding separated material were transferred to a graduate and cosity index of a base oil was raised from 94.5 to 113.4 by the kerosine was added to adjust the volume to 10 ml. If visual suspension data were desired, the sample could be observed in the addition of 1.5 weight yo of copolymer D. I n this function, it same graduate or in a 5-ml. graduate. If electron microscopic gives oil blends which show good stability of both viscosity and examination was desired, 2- to 5-ml. quantities of the sample were viscosity index. stored for 3 days in a vial and the sample was shaken well before the examination was made. C
Table VI.
Performance of Copolymer D in L-4 Tests
thermal reformate 4- 3.0 ml. TEL per gallon) Furfural-Extracted Conventionally Mid-Continent Refined Base Oil SAE 20 Pennsylvania SAE 20 None 0.5 None 1.0 Copolymer D , wt. % Antioxidant A, wt. % ' None 0.5 None 0.5 (Fuel:
Engine conditions Piston score (10 = clean) Engine score (100 = clean) Bearing cosrosion, mg. per whole bearing
8.0
74
9.3 89
6.0 73
9.5 93
350
150
1150
80
APPARATUS AND PROCEDURES
Carbon suspension tests were performed in kerosine according to the following procedure:
A paste containing 20% carbon black in a white oil base was prepared by milling Superba carbon black and Nujol on a threeroll ink mill for three passes. For the test, 3 grams of this paste was introduced into a Waring Blendor with 70 ml. (57 grams) of kerosine or a solution of the additive in kerosine. The material was mixed for 3 minutes. A 50-ml. graduated cylinder was
The cyclic low temperature engine tests employed a Chevrolet engine with narrow slotted oil rings. The test was of 96-hour duration divided into 2-hour cycles of each of three operating conditions which were repeated throughout the test. These rycles represent the following operating conditions:
1. A cycle of low engine speed and low engine load during which coolant temperature and oil sump temperature are held low (125' F.) in order t o simulate start-up or idling conditions. 2. A cycle of high engine speed and normal engine load during which the coolant temperature is low (100' F.) and the oil sump temperature is moderate (165' F.) in order to simulate driving conditions during the warm-up period. 3. A cycle of high speed normal load engine operation during which the coolant temperature is high (200' F.) and the oil sump temperature is high (245' F.) to simulate conditions of prolonged operation. LITERATURE CITED
(1) Willis, R. L., and Ballard, E. C . , Society of Sutomotive Engi neers' Golden Anniversary Annual Meeting, Detroit, Mich. January 11, 1955. RIDCEIVED for review September 22, 1954. ACCEPTEDMarch 7, 1955. Division of Petroleum Chemistry, 125th Meeting, ACS, Kansas Clty, M o . , March 1954.
