December 1950
INDUSTRIAL AND ENGINEERING CHEMISTRY
244 1
CONCLUSIONS
From laboratory bench tests, performtirice tests in hydraulic equiptnent, and practical application in automotive and industrial gear installations, it would appear that polyalkylene glycol synthrtic lubricants have :t wide field of utilization in npplications where improvement in wear charactmist8icsis either niandatory or desirable. Their pronounced a n t h e a r proparties, combined with their high viscosity indexes, low pour points, and freedoni from sludge, varnish, and carbon formation a t elevated temprritturcks render the polyalkylene glycols and their derivativrs a valuable d d i t i o n to the ever-increasing supply of improvrd luhricnnts, hydr:iulic fluids, and he:tt trsnsfer media. LITERATURE CITED
Air Force-Navy Aeronautical Specification for Jet Engine Oil, AN-0-Sa(May 3,1948). ( 2 ) Ceramic Age, 54, No. 1,36 (July 1949). (3) Coordinating Research Committee, CRC Test Procedure, Designation L-17-545. (4) Eastman, E. C., Dinsmore, D. R., Godtrey, K. L.,and Blake, E.S., Petroleum P T O C P S3,S10934 ~ ~ ~ ,(November 1948). (5) Pain, J. M.,Chem. Znds., 59, 1012 (1946). (6) Hansberry, C., “Determination of Ignition Characteristics of Hydraulic Fluids under Simulated Flight and Crash Con(1 )
Refiming,25, NO.2 , i2?- 38 (1946). McKee, 8. A.. Rwindells, .J. F., White, H. S , and Mountjoy, W., J . Resrorch S a t / . Bur. StrriLdurdu. 42, 125-30 (1949). (9) iMillett, W.H., Iron Stwl Eno.,25, 51-60 (August 1948). (IO) Murphy, C. M., Romans, J. B., and Zisman, W. h., l‘rctnu. Ani. Soc. Mech. Etagrs., 71, No. 5,561-74 (July 1949). (11) Murphy, C. M., and Zisriian, IV. A . , Luhrierctinn Ena., 5 , Nos. (8)
5and 6, 231-6,264-9 (1949). (12)O’Rear, J. G . , Milits, R. 0.. Spessard, 1). It., and Zisman, W.
A., “Development of the Hydvolube Non-Flammable Hydraulic Fluids,” Naval Research Laboratory, R r p t . P-3020 (April 1947). (13) Iioehner. T. G.. and Cltrttiichael, E. H., Lubriccztw~ ECno., . 5.. NO.1, 25-18 (1949). (14) Russ. J . M., Jr.,Ibid., 2, No. 4,151 (1946). (15) Ituss, J. M., Jr., “Uron Synthetic Lubrirants and Hydraul& Fluids,” Special Treh. P i h . 77, Annual A.S.T.M. Meeting, Atlantic City, Jurie 194’7, (16) Sullivan, M. V., Wolfe, J. K., and Zisman, W. A . , IND. ENG. CHEM.,39,1607 (19417). (17) Upham, E. W., and Mougey, H. C., Trans. Roc. ilufomofive Eng., 2,No. 3,434-49 (1948). (18) Wilson, L?. K., Zbid., 2,No. 2,242 (1948). H A C B I V ~Jrine80,1950. D
P O L Y M E R I C ADDITIVES F O R S Y N T H E T I C ESTER L U B R I C A N T S F. J. GLAVIS Rohm & Haar Company, Philadelphia, Pa. Interest in ester lubricants justifies a study of polymeric additives for these fluids. Data on a single polymer blend in di-2-ethylhexyl sebacate are used to demonstrate the various interpretations possible in discussing viscosity-temperature properties. Viscositytemperature effects are discussed for blends of representative ester lubricants and a commercially available viscosity index improver. Viscosity increase and viscosity index improvement are then demonstrated for blends of acrylic polymers and polyesters of high molecular weight in various ester types, including inorganic esters, glycol ether esters, glycol diesters, alkyl acylated ricinoleates, aryl dibasic acid diesters, aliphatic dihasic acid diesters, and polyesters of low molecular weight.
Y S T I t E T I C lubricants arc being used in a small but significant portion of the total lubricant field, particularly in specialized applications. Among the synthetics, certain esters have achieved considerable importance by virtue of a combination of desirable properties, notably low volatility and low freezing or pour point for a given viscosity range. The scope of ester applications is indicated by their use in a number of government specifivation fluids, discussions of their properties in a number of periodicals (1, 8, 6, 7 , 9-11), and disrlosures of specific fluid formulations in some patents (2,8, 12,14-16‘, 2,@, 26). The use of polymeric additives in conventional petroleum lubricants is well 23,,%?4), and the references noted above menknown (4,6,17,18, tion the use of polymers in ester-type synthetic lubricants. This paper gives the solubility and viscosity behavior of certain polymeric additives in selected groups of ester fluids, with particular rcAfcrcnce to acrylic polymers.
S
VISC0SITY.TEMPERATURE CHARACTERISTICS
Polymeric additives have been used in petroleum lubricants primarily for the increase of visrosity, improvement in viscosity
index, or reduction in wax-iriducwl pour point. In the rase of synthetic ester lubricants, t2hepour point reduction would not be expected berause the pour point is :t funrtion of the base fluid itself, analogous to the viscous pour point of petroleum oils, and is therefore not amenable to reduction by addition of a material that will increase the viscosity of the resultant blend. Accordingly, the main functions of polymeric additives in synthetic ester lubricants are to increase the viscosity of the base fluid und to improve the visrosity-temperature charac*teristic*sof thr fluid. I n many cases both cre achieved in one operation. The methods used to express viscosity-temperature characteristics of a fluid system are varied and give different and often ambiguous results. The viscosity index wale of Dean and Davis was worked out for petroleum oils which, a t that time, rarely ex(*ceded 100 in .viscosity index. For polymer-containing petroleum oils and ester lubric*:tntswith or without polymeric additives, visrosity index values are often well above 100 and are dependent on the viscosity level. This lrtttcr point is illustrated in Table I, where it is shown that the viscosity index for an ideal fluid (one that exhibits no rhange o f visrosity with temperature), v d e s from 100 to 360, depending upon the viwosity level chosen.
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
2442 Table 1.
Viscosity lndex Values for an Ideal Fluid Viscosity Index 365 208 176 162 154 141 101
210° F. Viscosity, C s . 2.0 10.0 20.0 30.0 40.0 75.0 165
Table 11. Comparison of Viscosity-Temperature Eyaluation Methods in Di-2-ethylhexyl Sebacate Systems Polymer Acryloid 710
Paraplex G25hv
Viscosity, Concn., Cs. Wt. yo at 210" F. 0.0 3.350 0.5 3.943 1.0 4.692 2.5 7.056 5.0 13.77 10.0 34.71 0.8 1.0 2.5
3.848 4.028 4.656
D-D V.I. 152 183 191 172 163 146
H-N V.I. 146 154 158 160 168 170
A.S.T.M. Slope 0.706 0.662 0.615 0.565 0.451 0.338
V.1; Ratio 0.416 0.501 0.590 0.720 0.850 0,929
184 192 195
156 157 160
0.677 0.640 0.588
0.506 0.530 0.599
I n recent years, investigators have attempted to divorce the expression denoting viscosity-temperature characteristics from the viscosity level. This work has included the use b y Ramser ($0)of the slope of the visrosity-temperature curve at its point of maximum curvature, the relative viscosity-temperature number (VTN) of Sanderson (2'1 ), which indicates how the kinematic viscosity versus temperature curve of the liquid compares with t h e curve for a hypothetical standard pure compound having the same viscosity at 210" F.; the Hardiman-Sissan (IS) viscosity index number; and the viscosity index ratio (19),which compares the viscosity index of an actual fluid with that of a fluid of t h e same 210" F. viscosity but no change of viscosity with temperature. As an illustration of the divergent interpretations t h a t may be given to the same set of viscosity values, data are listed in Table I1 and graphically presented in Figure 1 for the viscosity-temperature relationships of a given fluid system when these relationships are expressed as Dean-Davis viscosity index values, Hardiman-Nissan viscosity index values, A.S.T.M. slope values, and viscosity index ratios. Keeping in m i c j the need for more accurate and standard means of expressing viscosity-temperature relationships, the discussion in this paper uses both the Dean-Davis viscosity index aiid the A.S.T.M. slope, the latter giving a more regular improvement in the viscosity-temperature relationship for polymerthickened fluids. I n the light of 'the interest in polymer-thickened ester-type fluids, it seems desirable to accumulate information on the effect of various polymeric thickeners in the different ester types. Where low freezing or pour point requirements necessitate the use of a fluid which is too light a t normal operating temperatures, a thickening agent is indicated. Where !ow temperature requirements are not so strict but the higher melting fluids possess inadequate viscosity index values, the polymeric additive should improve that viscosity index with a minimum increase in viscos1ty. There are at present three commercially available viscosity index improvers. These materials have been designed primarily for petroleum-base stpcks and their use in synthetics was never intended as a main goal. Paratone (a polybutene supplied by t h e Enjay Corporation), Santodex (an alkylated polystyrene offered b y Monsanto), and Acryloid 710 (one of a series of oilsoluble acrylic polymers supplied by Rohm & Haas) are available only as polymer concentrates in petroleum stocks and their use necessitates the incorporation of small amounts of petroleum fluid in the ester lubricants under consideration. The Acryloids can be prepared readily in the ester-type fluids, and this is pre-
Vol. 42, No. 12
sumed to be the case for the other two types mentioned where they are soluble in t h e fluid involved. Through use of available concentrates in petroleum stocks, solubility and viscosity data in a number of representative ester types can be compared. Table I11 lists qualitative solubility results at room temperature, solubility implying sufficient dissolved polymer to produce viscosity increase in the resultant clear solution. Solution of the polymer was accomplished by heating the blend, when necessary, and Precipitation of the polymer from the blend on cooling toward room temperature was taken as an indiration of polymer insolubility. Turbid solutions were indicative of incipient polymer precipitation. Where polymer precipitation was not immediately evident, indefinite storage at room temperature caused no visibly observed turbidity or precipitation. These data indicate the wide solubilitj differences in the ester types. All three polymers are insoluble in tricresyl phosphate. Santodex and Acryloid 710 shoii a similar solubility behavior in the ester types listed, while Paratone is insoluble in all but di-2ethylhexyl sebacate. The solubility of the latter polymer in high concentrations in this solvent is particularly striking in view of its insolubility in diiso-octyl adipate Solubility differences are thus marked not only in different ester types but as a result of only slight changes in structure in the same ester class. I n Table IT7 are listed visvosity data for fluid blends involving Acryloid 710. Corresponding data for Paratone and Santodex have been omitted because the absence of definite information as to the polymer concentration in the commercially available concentrates prevents accurate comparison among the three polymers a t equal polymer conrentrations in the ester fluids. These data demonstrate once again that polymeric thickeners impart improved viscosity index values to the resultant solutions, the effectiveness of this viscosity index improvement being somewhat clouded by the dependence of viscosity index upon the viscosity level of the fluid involved. The separation of some of these polymers from solution a t temperatures of about -40 O F. demonstrates the borderline solubility conditions at normal operating temperatures for these blends. This discussion refers only to viscosity-temperature characteristics and does not take into consideration such properties as stability t o heat, shearing stresses, and storage. The effect of varying the molecular weight of the polymeric additive is illustrated below for the 2-ethylhexoic acid ester of the 2-ethylhexyl monoether of tetrapropylene glycol (see Table VI). Commercial Acryloid 710 contains a polymer which has a viscosity a t 100" F. of about 160 centistokes when determined a t 30y0 concentration in toluene. Viscosity-temperature properties for this polymeric additive are compared for those of a modified polymer, Acryloid 710 lv, which has a corresponding viscosity of about 70 centistokes. A polymer of decreased molerular size must be used a t greater concentrations to achieve the same viscosity increase as that obtained with a product of higher molecular weight. Viscosity index improvement is about the same under these conditions. These results are similar to those obtained for petroleum lubricants. I n practice, compromise is necessary between maximum improvement in viscosity-temperature rharacteristics and the molecular
Table 111.
Polymer Solubility in Ester Fluids at
Room
Temperature
Ester Paratone Santodex Acryloid 710 Di-2-ethylhexyl sebacatea S S S S S Diiso-octyl adipate b S 8 Triethylene glycol di-2-ethylbexoated Tetraethylene glycol di-2-ethylhexoate6 IC S S Polyoxyalk lene glycol diesterf I S S Tricresyl pzosphatea I IC I C 5 Plexol201 Rohm & Haas. b Plexol244: Rohm & Haas. C Slightly soluble on heating. d Flexol3GO Carbide & Carbon. 6 Flexol4GO: Carbide & Carbon. 1 Fluid 818 Carbide & Carbon. 8 Lindol, Chanese Carp.
::
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Dedember 1950
2443
-- 1.0
noted in Table 111failed to dissolve any of the three c o m e r 195 cially available viscosity index 0.9,o improvers, but polymers of + butyl methacrylate and octyl 18 methacrylate are soluble in this fluid. In the case of the lower alkyl phosphates, the increased viscosity is desirable, 551 175and is achieved along with viscosity index improvement, 2 170 whereas in the higher alkyl and I. 165aryl phosphates the viscosity is already high and only viscosity 160index improvement is necesD sary. It is interesting,to note the improved viscosity index of the base fluid when it conI50 sists of the trialkyl derivative 145 in which the alkyl groups are 1 1 I I I I I 1 I I I ' ' I I 1 , ) branched, as in the isononyl 2 4 6 8 I O 12 14 16 18 20 22 24 26 28 30 32 34radical. Centistokes nt 2 1 0 ' E Glycol dicarbonates have Figure 1. Viscosity-Temperature Relrtionrhips sufficiently low volatilities but poor viscosity- t e m p e r a t u r e properties. Improvement in size tolerated by the shear breakdown requirements. No attempt this latter respect is given by polymer blends. Here the initial has been made to determine the actual molecular weight of these viscosity is sufficiently high and only viscosity index improvement polymers. For this comparison, the maximum allowable molecuis required for most possible uses. The same polymers are soluble Inr size has been determined by means of an arbitrary pump in the lower boiling simple carbonates. I n Table V and subtest on a standard fluid of known breakdown under the shear sequent tables, the molecular weights of the different polymers (3onditions.employed. A description of such a pump test can be have not been determined. All the polymers are inbthe approximate range of 50 to 100 centistokes viscosity for a 30% found in Bureau of Ordnance Sperification 51-I?-21. As an extoluene solution at 100 O F. This should give reasonably uniform ample of the control of polymer size for such applications, ArmyNavy Aeronautical Specification AN-0-366requires that the shear resistance to shear breakdown, although no data on this point breakdown of the polymer must not exceed that of a blend of have been collected. a standard polymer, as given in Army-Navy Aeronautical SpeciGLYCOL ETHER-ESTERS fication AN-F-53. Now that differences have been indieated in polymer solubility In some synthetic lubricant applications thr high volatility of and in viscosity-temperature vharacteristics in different ester many fluids eliminates them from consideration. The polymeric types, it seems advisable to turn to modifications in polymers additives discussed in this paper arc also suitable for the lighter which will give desired solubility and viscosity relationships in esters and other synthetics which are used in hydraulic formulathe different ester types that may be of interest as lubricants. tions. With the low volatility required for the usual lubricant Modifications have been made in the acrylic polymers. Other types of pol\ meric additives have also been investiTable IV. Viscosity Data for Blends Containing Acryloid 710 gated, but none of these gave as much Polymer Viscosity, Cs. visimprovement in the viscosity-temperaConcn., cosity A.S.T.M. Lure characteristics as the proper acrylic Fluid Wt. %" 210° F. 100° F - 4 O O F. Index Slope polymer. Such polymers include polyDi-2-ethylhexyl sebacate 0 0 3 350 12.90 1450 152 0.706 0 185 3 943 15 01 1630 183 0.662 vinyl acetates, formals and acetals of 0 370 4 692 17 77 1910 191 0 615 0.925 7.066 28 98 3040 172 0 565 polyvinyl alcohols, polystyrene, poly1.85 13 77 54 28 7110 163 0 451 vinyl chloride, ethylcellulose, and poly3 70 34 71 146 1 Indeterminate 146 0.340 vinyl alkyl ethers, in which the alkyl Dilso-octyl adipate 0.0 2 837 10 15 990 143 0 721 0.185 3 016 10 70 1020b 156 0.692 group was methyl or butyl. These poly0 370 3 188 11.32 1070b 166 0 690 0.925 3 844 13 70 1280b 195 0 634 mers were investigated in differenf vis1.85 5 160 18.43 1800b 195 0 580 cosity grades wherever possible, but the 3.70 8 529 31 16 3050b 175 0 496 avcrage molecular weight was not deTetraeth lene glycol di0.0 2 923 1 1 72 3210 112 0.763 2-ethyYhexoatec 0.185 3 079 12 22 3430 126 0 743 termined in any case. Polyesters offrr 0.370 3 244 12.79 3460) 138 0.722 0.925 3 834 14 86 Separated 174 0.672 interesting possibilities and are disrusscd 1 85 4 846 18 33 Separated 190 0 609 3.70 7 664 28.25 Separated 177 0 517 briefly below. The esters under study have been divided into classes. Polyoxyalkylene glycol 0 .O 2 562 9.765 2190 101 0.794 1
~
1
1
1
1
-
'
I~
l
~l
1
1
1
-
-
A-
-
-z
Fy
y
-
di&terJ
INORGANK ESTERS
Inorgttriic esters of possible intevebt phosphatesp carbonates, and borates. Data are given in Table V orl polymer combinations with some of these base fluids. The aryl phosphate class as
0.185 3 084 12.02 3020 132 0.733 0.370 3 250 12 57 3080b 145 0.717 o 925 a 791 14.53 moa 192 0.675 1 85 4.899 18.34 Separated 191 0.605 3.70 7.877 29.04 Separated 176 0.510 a Figures represent actual polymer concentration, but there has been added approximately equal weight of petroleum-base stock used as camer for polymer. b Turbid solution, incipient precipitation. 0 Flexol4GO. d Fluid 818.
I N D U S T R I A L A N.D E N G I N E E R I N G C H E M I S T R Y
2444 Table
V. Polymer Blends in Inorganic Esters
Ester Tricresyl phosphate
Concn.. Wt. %:
Polytncr \-one RhI.i'I OM.4h None OM.4h
Tricresyl phosphate Tributyl phosphate
...
5.0
15.0 10.0
..
5 :o 10.0 8 .3 15.0
RJI.1"
Bubyl diglycol carbonate Butoxyethyl diglycol carbonate h C
Bnt,yl methacrylate. Octyl methacrylate. Ethyl methacrylate.
Table Polyinrr Concn., Wt. yo
210' E'. 1.038 9.38'1 35.63 17.64 1.190 4.700 7.083 13.871 19.138 3..310 11.57 6.716 2.733 12.51
None ... EMAC 5.0 HM.4d 5.0 None ... BRIA" 21.0 DMIAF 16.0 9.051 None ... 3.567 R.\I.\a 15.0 12..X Hexyl methacrylate. e Dodecyl met,hacrylate
Triisononyl phosphate
0
-.V;SE!!EC~.
VI.
Polymer Blends with
-
1029.20
68.22 326.9 77.46 2.726 14.15 16.96 40.01 99.69
14.72 76.06 84.77 11..56 61.68 41.85 17.71 73.21
Viscosity Index -24 120 127 I55
,
227 204 160 149 136 134 147 77 153 1 3 84 144
Glycol Diester Diethylene glycol dipropionate Diethylene glycol diisobntsrate Triethylene glycol diisobutyrate
~
2100 F,
Table VII.
Slope 0.872 0.673 0.492 0.450 0.780 0.528 0.373 0.550 0.171 0 . 7'26 0.610 0.647 0.757 0.520
0.652 0.79R n, 570
OPJO'
Viscosity, Cs. Viscosity 1000 F. -400 F. Indey ... 3 .o m 12.03 3,370 121 3.2 9 807 40.89 10,400 164 4.0 11 .89 52.94 14,600 160 1.2 6 . '463 24.92 ... 174 Acryloid 710 ... 163 2.4 72.3.> 49.56 a 2-Ethylhexoic acid ester o f 2-ethylhexyl nionoether of tetrai)ropylrne glycol. Polymer None Acryloid 710 1v
.I,s,T.M.
A.S.T.;\I. Slope 0,755 0.56-5 0.510 0.563 0 , 468
Poiymer Blends in Glycol Diesters Polymer None
M .in
Polymer Concn., Wt. % 0.0 3.0 3.5 5.9 0.0
5.0 10.0 0.0
3.2 3.7 4.5 5.0 10.0 0.0 5.0 8.5 17. 24.4
-vJh%!&~%
21O0 .'I 1,111
100' F. 2,984
A . 619 19.81 26.24 8.268 19.38 63.38 1.302 3.321 6 1 . .54 19.73 113.3 433.0 4.174 1.544 29.61 9.566 38.45 12.11 28.52 17.44 .>3.80 21.99 117.3 474.3 2,923 11.72 41.10 10.35 75.69 18.04 9 . 0 3 3 33.59 13.46 50.20
Viscosity Index
...
199 186 162
...
162 153
...
1 80
173 163 163 151 112 160 5 6
4.S.T.M. Slope 0.928 n. 472 0.441 0.368 0.817 0.344 0.252 0.791 0.414 0.404 0.381 0.275 0.262 0,763 0.493 0.430 0.492 0,449
Vol. 42, No. 12
of alcohol. The product of such a rewtion represents a mixture of adducts containing varying numbers of oxyalkylerie groups per molecule. T o eliminate part of this heterogeneity, the glycol moiioethers have been distilled carefully before proceeding with the esterification. The glycol ether-esters have been. prcpared by interaction of the monoethers with an acid chloride selected from the group ranging from acetyl to dodecenoyl. Distillation is again carried out to ensure a narrow boiling range for the ether ester. I n this preparation, the use of alcohols or acids of low molecular weight produc6es fluids of high volatility, whereas the use of materials of high molecular weight results in the formation of high melting reaction products. Although the viscosity and viscosity index of all these esters are increased by the use of ac*rylic* polymers, the effects are given for the 2ethylhexoic acid ester of the 2-ethylhexyl monoether of tetrapropylene glycol This base fluid was selected as having reasonably low volatility (1.20/, by Coordinating Research Committee volatility test) and good low temperature behavior (freezing point below - 75' F.). Both viscosity and viscosity index can be increased markedly n hile retaining the good low temperature behavior of the base fluid. GLYCOL DIESTERS
C;lyrol diesters c*omprise one division of the diester group of synthetic lubrirants. Representative fluids are diethylNone Tetraethylene glycol di-2-ethylRMhb heroate ene glycol diproprionate, triethylene 172 OMAC glycol diisobutyrate, tetraethylene glycol di-2-ethylhesoate, decamethylene glycol a Methyl acrylate. di-2-ethylhexoate, and a commerciallj b Butyl methacrylate. Octyl methacrylate. available polyoxyalkylene gly-ol diester. l'olyoxyalkylerie compounds represent an Table VIII. Polymer Blends in 2-Ethylhexyl 2-Ethylbutyryl Ricinoleate average molecular weight and l):tse fluids Polymer of this type may not have identical visViscosity, CR. Concn., . _______ Viscosity A S.T.bl. Polymer Wt. % 210° F. 100° F. -40° F. Inder Slope cwsity-temperature values from hatrh to 0 686 batch, as the fluid is not a c.hrrniralentity. 15.28 1800 158 None ... 3.851 0 629 21.24 2370 173 Acryloid 710 0.8" 5.104 This lack of homogeneity m:iy account 2 6 . 7 8 3010 176 0 662 1.6 6.778 0 866 32.96 3860 164 2.4 7.626 in part for the good low temperature 4 7 . 5 3 .5560 162 0 304 4.0 11.12 fluidity of this rlass of diesters. While z . Unlike figures given in Table 11, values represent concentration the higher molerular weight members of these classes may require only viscosity index improvement, the laxer members require bath viscosity ixwrease and viscosity index iniprovement. applications, the use of monoesters is strirtly limited to the This can be accomplished, as evidenred by the data in Table VI1 materials of highcr molerula~ weight, and these are usually of as well as by some of the data in Table IV, where the rommercid such high melting point as to be unsatisfactory. However, esters viscaqity index improvers have heen used. of monoethers of polyoxyalkylene glycols represent one group of monoesters which meets these requirements. The pffect of polymeric additives other than higher polyoxyalkylene derivatives has ALKYL A C Y L A T E D RICINOLEATES not been disclosed. Acrylic polymers have now been incorpoThe alkyj esters of arylated ricinoleic acid romprise annther rated in these fluids t o give incieased viscosity and improved visdivision of the diester luhrirmt group. These compountls mav cosity index to the resultant blend. This is achieved while retainbe prepared by reaetion of acid halides with alkyl ririnoleates, the ing the excellent low temperature fluidity icherent in the lowlatter obtained from rastor oil by alcoholysis. The lower derivafreezing base fluid that can be ured undw these conditions. tives exhibit a high degree of volatility andrelatively poor luhricThe monoethers have lwen prepared in the author's lahoratorv ity, and the higher homologs have generally high viscous iJoUr or br adding propylene oxide to monohydric alcohols ranging from freezing points. Modified acrylic polymers are effertive i r i thic: butyl to dodecyl in a ratio or :tpprosimntely I moles of oxide to 1 C
INDUSTRIAL A N D ENGINEERING CHEMISTRY
December 1950
2445
previously demonstrated for the glycol ether esters, a polymer of increased molecular weight gives greater viscosity Polymer Concn., Viscosity~Ca. Viscosity A.S.T.M. Fluid Polymer Wt. % 210° F. looo F. Index Slope increase for a given polymer concentraDioctyl phthalate None ... 4.223 29.19 7 0.848 tion. This is shown for the case of octyl OMAO 3.5 10.39 70.88 129 0.635 methacrylate polymer in butyl phthalyl 4.5 12.61 85.10 134 0.600 OMAb 5.0 11.0 64.3 142 0.590 butyl glycolate. 6.8 13.24 85.37 137 0.588 Branched-chain alkyl diesters of ali10.0 21.6 112.2 147 0.429 12.0 39.52 273.8 134 0.426 phatic dibasic acids, already in use in Dioellosolve phthalate None 2.985 16.61 -3 0.883 MMAC 5:O 24.6 143.3 142 0.4d5 government specification fluids, represent 10.0 158.0 1417 127 0.370 a second group of dibasic acid diesters. Butyl phthalyl butyl glycolate None ... 3.747 24.18 -5 0.867 MMAC 5.0 29.26 218.8 134 0.468 Solubility differences in such closely re10.0 239.4 3859 110 0.417 OMA' 5.0 7.614 29.34 172 0.537 lated diesters as diiso-octyl adipate and 10.0 14.00 56.52 161 0.450 di-Zethylhexyl sebacate have been noted OMAb 5.0 5.230 28.61 126 0.717 10.0 13.03 51.38 161 0.462 in Table 111. For this class of fluids, di16.0 29.7 125.5 148 0.336 2-ethylhexyl sebacate (Plexol 201) will a Viscosity of 30% solution of this polymer of octyl methacrylate in toluene a t 100' F. is approxiT~~effects of variServe as an mate1 1 0 0 0 s . b d m o s i t y of 30% solution in toluene of this octyl methacrylate polymer a t 100' F. is approximately O U ~modifications of acrylic polymers 40 08. Methyl methacrylate. are noted in Tables I V and X. The viscosity-temperature c h a r a c t e r i s t i c s differ somewhat as the molecular conTable X. Polymer Blends in Di-2-ethylhexyl Sebacate figuration changes. As the molecular weight of the polymer increases, the effectiveness Polymer Concn., Viscosity, Cs. Viscosity A.S.T.M. as a viscosity improver beoomes greater, followPolymer Wt. % 210' F. 100O F. -40° F. Index Slope None ,.. 3.350 12.90 1450 152 0.706 ing exactly the trends noted in polymer-thickened Butyl methacrylate 4.9 10.05 36.18 .,.. .. 172 0.464 petroleum oils. In addition to the acrylic poly6.2 13.26 45.89 168 0.415 Octyl methacrylatea 6.7 6.160 23.08 . . 182 0.569 mers, some work has been done on the use of 13.8 16.21 70.22 ... 156 0.454 polyesters of high molecular weight as viscosity Oct 1 methacrylateb 6.6 10.92 40.03 ... 169 0.461 Doakqyl methacrylate 5.3 8.660 31.21 . . . 175 0.490 and viscosity index improvers for di-2ethylhexyl 6.5 10.11 36.00 172 0.463 Paraplex G25hv 0.5 3 848 14.32 iiao 0.652 sebacate. These polyesters have been prepared 0.638 1.0 4.028 14.89 1980 192 from aliphatic dibasic acids and aliphatic glycols 2.5 4.656 17.33 3680 195 0.611 to a selected moleculrtr weight range. Paraplex a Viscosity of 30% toluene solution approximately 40 os. a t 100' F. G25hv (produced on an experimental scale by b Viscosity of a 30% toluene solution approximately 100 os. at 100' F. Rohm & Haas) ie the polyester used. It is obvious that the compound is functionally capalde of many changes to give altered solubility and viscosity-temperature characteristics required by the base fluid in type, regardless of the alkyl and acyl groups used. Data are question. Polyester additives give effective improvement in visgiven here only for the Zethylhexyl ester of Zethylbutyryl ricinocosity index for low increments of viscosity increase. Data w e leic acid, which has been selected as giving a good compromise of given in Table X. volatility, freezing point, lubricity, and the like. POLYESTERS The acrylic. polymers give both viscosity increase and viscosity index improvement to this compound, although the visTriesters such as glycerol tri-2ethylbutyrate and castor oil cosity index is already high in the base fluid. This is one case undergo viscosity index improvement when blended with acrylic where viscosity increase would be the main goal rather than vispolymers. The base fluid viscosity in the latter case is already cosity index improvement. The data for the acrylic polymer sufficiently high so that viscosity increase is not necessarily wanted. blends are given in Table VIII.
Table IX. Polymer Blends in Phthalate Eden
.
-
ESTERS OF DIBASIC ACIDS
'
These esters represent the third type of diester to be considered, and these have been recognized (1, 8, 10) as having a very good combination of properties for use as synthetic lubricants. One group of these diesters consists of esters of phthalic acid. Such fluids are generally thick and exhibit rather high viscous pour points or freezing points. Therefore, maximum viscosity index improvement with minimum viscosity increase is the goal for the polymerthickened blends. The improvement in viscosity index through the use of modified acrylic polymers is given in Table IX; a marked viscosity index improvement is achieved. Therefore, for cases where low pour point is not necessary, these polymer-thickened blends offer good viscosity index fluids of low volatility. As
Table XI. Fluid Triisobutyrin
Polymez None Acryloid €IFa BMA b
Castor oil
None
BCMAC
Polymer Blends in Polyerterr
Polymer Concn., Wt. %
...
12.0 10.0 15.0
... 0.5
Viscosity, Cs. 210' F. 100' F. -40' F. 1.71 5.69 ... 10.43 32.33 12.15 47.82 23'80 106.7
1.5 3.0
FIiiid AP-52d
AP-52
None -4cryloid 710
Paraplex G25hv
... 0.5
1.0 2.5 5.0 10.0
,
23.14 25.40 31.08 39.99
365.1 382.6 444.8 526.4
9.072 10.26 1.1.47 16.00 25.04 55.94
53.25 59.48 66.19 91.86 143.4 382.2
... ... ... .. . ...
... ...
23,900 24,720 27,860 47,000
...
...
1.0 10.74 61.87 49,900 2.5 13.55 75.05 5.0 19.35 103.6 147bO 7.5 29.21 161.6 Inheter. * Another in series of acrylic polymers available from Rohm & Haas. b Butyl methacrylate. Butyl Carbitol methacrylate. d Polyester prepared from glycols and dibssic acids.
Viscosity Index 178 164 160
...
A.S.T.M. Slope 0.872 0.374 0.466 0.390
85 95 105 115
0.628 0.609 0.581 0.562
140 142 144 145 143 135
0.623 0.594 0.584 0.525 0.428 0.393
143 147 143 142
0.582 0.544 0.442 0.420
2446
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Polyesters of low molecular weight, such as that supplied by Rohm & Haas as experimental fluid AP-52, represent a n estertype base fluid which has been prepared from dibasic acids and glycols to the desired molecular weight range. These fluids, although they often possess excellent viscosity-temperature properties b y themselves, are susceptible to visccsity increase and viscosity index improvement by means of both acrylic and higher molecular weight polyester additives. The effects of adding these polymers to a polyester lubricant are given in Table XI. The main effect to be desired here is viscosity increase, as the viscosity index for this particular polyester is already excellent. CONCLUSIONS
The general effects on viscosity and viscosity index of blends of polymeric additives and synthetic ester-type lubricants have been presented. I n general, improvement in both properties is obtained where the polymeric additive is soluble in the particular ester involved. These polymers have also been used with lower boiling synthetics which are adaptable to use in hydraulic fluid mechanisms, but these hydraulic fluids, although requiring some lubricity, do not seem to fall within the scope of this paper. It is hoped that this work will serve as a basis for further applications for polymer-thickened synthetics. ACKNOWLEDGMENT
The writer wishes to arknowledge the able assistance of Elsie E. Becker. LITERATURE CITED
(1) Adkins, D. C., Jr., Baker, H. R., Murphy, C. M., and Zisman,
w. A., IND.ENG.CHEM.,39,491 (1947). (2) Ballard, S. A., Morris, R., and Van Winkle, J. L. (to Shell Development Co.), U. S. Patent 2,481,278 (Sept. 6, 1949). (3) Bried, E. M., Kidder, H. F., Murphy, C. M., and Zisman, W. A., IND. ENG.CHEY., 39,484 (1947).
Vol. 42, No. 12
Bruson, H. A., U. S . Patent 2,901,627 (Aug. 31, 1937); 2,100,993 (Nov. 30,1937). Byers, J. H., Natl. Petroleum News, 28, No. 49, 83-9 (1936). Evans. H. C.. and Young. ENQ.CHEM..39, 1676 - D. W.. IND. (1947).
Fenske, M. R., Office of Scientific Research and Development, O.S.R.D. Rept. 1894 (Oct. 6,1943). Fife, H. (to Carbide & Carbon Chemicals Corp.), U. S. Patent 2,457,139 (Dec. 28, 1948); Brit. Patent 606,407 (Jan. 15, 1946).
Gisser, H., Lubrication Eng., 5, No. 4, 176 (1949). Glavis, F. J., and Stringer, H. R., Am. Soo. Testing Materials, “Symposium on Synthetic Lubricants,” 1947. Hain, G. M., Jones, D. T., Merker, R. L., and Zisman, W. A., IND. ENG.CHEM.,39,500 (1947). Hamilton, W. (to Lockheed Aircraft Corp.), U. S. Patent 2,392,530 (Jan. 8, 1946). Hardiman, E. W., and Nissan, A. H., J. Inst. Petroleum, 31, 225 (1945).
Merker, R. (to U. S. Navy), U. S. Patent 2.456.642 (Dec. 21, ENQ.CHEM.,41,2546 (1949). 1948); IND. Morgan, J . D., and Loew, R. E. (to Cities Service Oil Co.), U. 9. Patent 2,396,191 (March 6 , 1946). Morway, A. J., and Zimmer, J. C. (to Standard Oil Development Co.),Ibid., 2,467,147 (April 12, 1949). Otto, M., Blackwood, A. J., and Davis, G. H. B., Refiner Natural Gasoline M f r . , 13, 411-22, 426 (1934); Oil Gas J . , 33, NO.26,98-106 (1934). Otto, M., and Mueller-Cunardi, M., U. S. Patent 2,130,507 (Sept. 20, 1938). Penzig, F. G., Tech. Rept. GS USAF, Wright-Patterson FTR 2206 ND, “Extrapolation of Viscosity Index,” Project DP-151, Supt. Documents, Washington 26, D. C. (May 1948). Ramser, J. H., IND.ENG.CHEM.,41,2053 (1949). Sanderson, R. T., Ibid., 41,368, 375 (1949). Standard Oil Development Co., Brit. Patent 692,214 (July 16, 1943). Thomas, R. N., Zimmer, S. C., Turner, C. B., Rosen, R., and Frolich, P. K., IND.ENG.CHEM.,32,299 (1940). Van Horne, W. L., Ibid., 41, 952 (1949); Petroleum Refiner, 27, NO.3, 90-5 (1948). Zisman, W . A., and Hain, G. M., U.S. Patent 2,448,557 (Sept. 7, 1948). RECEIVED June 23, 1950.
NONCATALYTIC POLYME OLEFINS TO LU F. M. SEGER, H. G. DOHERTY,
ILS AND
A. N. SACHANEN N. J.
Socony-Vacuum Leboratorisr, Paulsboro,
Excellent lubricating oils have been prepared by the noncatalytic polymerization of normal 1-olefink. The variables investigated in this study were: temperature, time, pressure, and olefin chain length and structure. Optimum results were obtained at 650’ F., 10 hours reaction time, and 250 pounds per square inch gage. From 1-decene the yield of synthetic lubrieant was 64.3 weight 70 of the olefin charged. Inspection data were as follows: viscosity, 5.79 cs. at 210’ F.; viscosity index, 142; pour test, -5. Cracked paraffin wax and Fischer-Tropsch product have also been used successfully as charge stocks. The synthetic oils were considered as potentia1 replacements for premium grade motor oils.
ATALYTIC polymerization of olefins or, in general, of unsaturated hydrocarbons has been discussed in numerous artid e s and patents. Production of polymer gasolinefromgaseous olefins and synthesis of plastics or rubber from isobutene, butadiene, and other unsaturates are well known and widely used comniercial processes. Synthetic lubricating oils were produced b y catalytic polymerization of olefins in Germany during World War
C
11. In conbrast, noncatalytic polymetization of unsaturated hydrocarbons has not attracted much interest. The activation energy of noncatalytic polymerization of unsaturated hydrocarbons is usually fairly high, and, a8 a result, relatively high temperatures are necessary to effect the polymerization. Hence various side reactions may occw, simultaneously affecting the yield and properties of polymerized products. The use of proper
