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
September 1950
1841
tions by metd interehange to yield a film of metsl which tends to prevent aeizure and which acta 89 an impmved d a c e far the adsorption of the soap film which is responsible for a lower 00efficient of friction. In the p-nee of sulfur, lead snd copper s o a p give sulfide film which lower the tendency of aeisure and reduce wear; friction is reduced by the adsorbed map. The remlta obtained largely confirm the mechanism pm-d by T h o r p aod Larsen (#O) to explain the action of acids snd esters 8 8 antiseizure compounds. ACKNOWLEDGMENT
Thanks nre due Frederick Boehm, Ltd., for furnishing some of the metal naphthenetes and the She11 Refining and Marketing Company, Ltd.,for the uee of facilities to oamy out tests on the four-ball machine.
n
d.
(1)
nmuoeRArm Beeok. 0..Givens, J. W., and WiUiams. E. C.. Prac. Rou. Sac.
(London).A177, 103 (1940). ( 2 ) Biadgett, J . A r n . C h . S o c . . 5 7 , 1W7 (1935). (3) Bowden. F.P., J.h t . Petmroleum, 34,654(1948). (4) Bowden. F. P.. Gregory, J. N.. and Tsbor, D.. Notwe, 155, 9 7 (1945). (5) Bowden. F. P.. and Isben, L., Pmc. Roy. SOC.(Lmdm),A169, .,v*
,rnnm
"'I \""'I.
Bowden, F.P., and Moore. A. J. W., Nature, 155,461 (1945). (7) Bowden. F. P.. and Ridler. K.E.W., Pmc. Roy. Soo. (Londrm). (6)
AIM. 640 (1936).
Figure 14.
and Tabor, D., Ann. Repa. m P~ogmwC h . ( C h .Soo. Londrmt. 42.20 (1945). (9) Churchill. J. R.. Hunter, M. 8..and M-. R. B..Metal Proo(8) Bowden. F.P.,
W e a r Spots
show anomlous behavior on steel, and stthough some chemical reaction is po%sible between the eeter and Bteel, under extreme conditions, to form ~n imn msp, this factor is unlikely to play a major part in lubrication by blends of esters under ordinary eonditions. In the presence of sulfur, B sulfide film is formed, which facilitates adsorption of the polar compolmda, giving B lower 00 efficient of friction and lower wear. Under heavy landing conditions breakdown of the film occur8 with increased wear or even welding of the surfaces. Certain m a p appear to effect lubriestion under Sewre candi-
re*. 42. 1010 (1942). Devqr. W., J . Inst. Pdmlcun. 31, 154 (1845) Zbid.. 33, 574 (1947). Devey. W.. Sci. Lu(rrimtion.lI (Sept. 7.1949). Frewing. J. 3.. P m . Roy. Sm. (Ladon),6181, z( (1942); A182 270 (1942). (14) Greenbill, E.B.. J.Znat. Peholnrm,34,659(1948). (15) Hardy. "Collected Worka," London, Cambridge Univ-$y Press, 1938. (16) Hughes, T. P., end Wbittingham. G.. TIOM. Far&# Sm.,38, 9 (ls4a). (17) Masters. D.L . , M d d l u ~ , 2 9 , 1 0 1(1943). (18) Prutton. C. F..Turnbull. D., and Dlouhu. G., J. h t . Pslroroleu~ 32, 80 (1946). (19) Sirnard, G. L., Ruasell. H. W.. and Nelmn, H.R., IND. Em. C~rnw.,33, 1352 (1941). (20) Thorpe. R. E., and Laraen, R. G.. Ibid., 41,938 (1948). (10) (11) (12) (13)
RWCEIV ~ ~ ~~
~za, ~ 1848.~
b
s
r
EXTREME PRESSURE LUBRICANTS Phosphorus Compounds as Additives WILLIAM DAVEY Aeton TerhnicoI College, London, EngIond
The extreme pressure properties of wnie phosphorus compounds, blended in mineral oil, alone, and i n t h e pnsenee of fatty acids, or esters, or sulfur, have been assewed by the four-ball maohine. Phosphites are superior to phospbatee as extreme pressure additives a n d alkyl estere are superior to aryl esters. T h e addition of fatty acids, esters, or sulfur improves the extreme pressure properties of blends of phosphites and phospbatee. Some thiopbosphitee and thiophospbatea have been found to poesees good extreme pressure prowrties. The extreme pressure properties of =me chlarinated phosphites and
pbwphetsa have hen studied, and mmpounda containing
a C l r C - group were found to pas-s excellent lubriolting properties and to be active a t low concentrations.
The rnechaniem by which phosphoms oompounds redua friction and wear hae been studied.
B
EECK snd hrs owworkera (I,#)first studied the lubricating properties . of' blends of tricresyl phosphate in mineral oil by means of the four-ball machine, m d ahowed that this compound was most effective in wear reduetian in 1.5% oonwtration; higher proportions of the additive gave inoreased wear of steel teat balls. This result, together with studips ming metsls which were unlikely to react chemienlly with the phosphate additive,
INDUSTRIAL AND ENGINEERING CHEMISTRY
1842
Vol. 42, No. 9
Since esters can also hprove the lubricating properMelting Phosphorua Content, ties of blends of phosphorus Point Boiling Wt. %esters, it appears unlikely that Compound" Appearance C. ' Point, C. Found Calcd. iron soaps will be formed exTri( cresy1)phoaphite White needles 52 8.75 8.80 .. 220/ii'mm. 10.0 10.0 Tricyrlohexyl Triptkyl phosp%osphite hite } Colorless oil cept under very extreme con.. 180/10 mm. 9.40 9.46 Trioctyl phosphite Pale yellow liquid .. ZOO/lO mm. 7.41 7.40 ditions, and, in addition, the Triaetyl phosphite ' 67 ... 4.10 4.11 T+aetyl phosphatr I chemical attack of the acid to 70 ... 4.00 4.04 'holey1 phosphite 40 ... 3.75 3.72 form a soap would tend to inTrioley1 phosphate 1 White waxy solid 48 ... 3.60 3.65 Tristearyl phasphi t c 68 3.70 ... 3.65 crease rather than decrease 72 Tristearyl phosphate 1 3.60 3.63 Triethyl thiophosphite go/ii 'llllll. .. wear. 14.5 14.5 Triamyl thiophosphite Colorless liquid 125/12 iniii. ... . 9.05 9.12 The addition of free sulfur Trioctyl thiophosphite J 150/10 mm. 6.60 6.65 Triphenyl thiophosphite White needles 64 8.65 8.65 improves the extreme pressure Triahloroethyl phos hite 2501 i3 '111111. 11.50 11.50 Tri(trichloroethy1 pfkphite Colorlevs liquid properties of blends of phos.. 263 6.45 6.50 Tri tnchloroethyl~phospliste I 73 ... 6.30 6.30 phites and phosphates, just Tri~tnchloro-lerf-butyl)pliosphit e 44 ... 5.53 5.50 Tri(trich1oro-tert-but 1)phoRphate White needles 83 ... 5.35 6.37 as with chlorinated compounds Tri Tri[pchlorophenyl)phosphite o-chloropheny1)pxosphite 50 ... 7.51 7.46 56 (6, 7) or acids, esters, and 7.50 ... 7.51 Other additives tested were carefully purified speaiinens from ooinmercial products. soaps (3,d), whereas certain From trichloroethyl alcohol. thiophosphitea and thiophosFrom t,richloro-frrt-butylalcohol. phates show marked extreme pressure activity when blended in mineral oil. led to the con(-lusion that tricresyl phosphate reacts chemically The German workers attempted to explain the enhanced estreme pressure activity shown by chlorinated phosphorus comwith steel to form a film, believed to be a phosphide; friction and pounds on a basis of increased acidity or improved adsorption, but wear are reduced by chemical polishing. This conclusion was it appears probable, in view of the behavior of combined sulfurconfirmed by the formation of iron phosphide in static heating chlorine additives (8, 7), that such compounds form a chloride tests. Addition of oleic acid markedly improved the lubricating phosphide film, which is readily sheared giving decreased friction properties of tricresyl phosphate blends, and it was suggested that the phosphate additive will not be particularly effective unless a and wear. This idea was confirmed in this work, and the relations between the structure of chlorinated compounds and exfatty acid is also present, since it is probably incapable of reacting treme pressure activity, established by the present author (6), chemically with the steel surface at low temperatures. apply to chlorinated phosphites and phosphates, a Cla-Cgroup Thew results led the Germans to prepare and test a number of phosphorus compounds for use as extreme pressure additives and being particularly effective in conferring such activity. The their work has been reviewed by Tingle ( I d ) and West (It?). addition of sulfur has been found to improve the performance of blends of chlorinated phosphites and phosphates. Thorpe and Larsen (11) have carried out tests on blends of 1 weight % of tricresyl phosphate in white oil and they suggest that The mechanism of action of phosphorus compounds as e11renie this compound reacts rapidly with steel to form a thin, solid, nonpressure additives has been studied and the phosphide film theory conduct,ing film, which prevents seimre by shearing in preference confirmed. Thiophosphites and thiophosphates form sulfidephosphide films whereas chlorinated phosphorus compounds form to metal-trrmetal contacts. The improved lubrication shown by chloride-phosphide films. The types of wear produced by differfatty acid-phosphate blends is explained by Thorpe and Larsen ent additives are illustrated by photographs of typical wear spots 89 being due to improved adsorption of the polar fatty acid on the produced. surface of the chemically formed film. In the present work the following aspects were studied :
TABLE I. PROPERTIES OF PHOSPHITES AND PHOSPHATES 0
0
I
1
A. The extreme pressure properties of alkyl and aryl phosphites and phosphates in mineral oil. B. The effect of the addition of acids, esters, or sulfur on the extreme ressure properties of phosphite and phosphate blends. C. TBe extreme pressure properties of thiophosphite and thiophos hate blends. D. T i e extreme pressure properties of some chlorinated phosphites and phosphates, the effect of added sulfur, and the effect of a C&-C- $roup on the lubricating properties of chlorinated phosphite an phosphate blends. E. The mode of action of phosphorus compounds as extreme pressure additives. Phosphites have been found to be superior in extreme pressure properties to phosphates, this difference being most marked with the tributyl, tricresyl, and tricyclohexyl compounds. Tributyl and trixylenyl phosphates have been found to show an optimum concentration for effective wear reduction, analogous to that shown by trirresyl phosphate. The lower friction and wear shown by blends containing a fatty acid and a phosphite or phosphate may be due t o two possible mechanisms: Improved adsorption of the acid on the film formed by the chemical reaction of the phosphite or phosphate with the steel surface. The formation of an iron soap by chemical reaction of the acid and the steel and im roved adsor tion of this soap at the surface; lubrication is effectei by the comgined soap-phosphide film.
1.o
2.0 3.0 ADDITIVE, %
40
5.0
Figure 1. Wear-Additive Concentration Curves 1
2 3 4 5 6 7 8 9
=
Tributyl phoephate 120-kg. load
= Tnicremyl pbosphatd 120-kg. load
---
= Tricrnyl phosphate: 100-kg. load = Tdbutylphosphete 100-k load Trixylenyl phoephde l20-&. load Trixylen 1 hoa hate'100-k load Tributyrpgoepkte, h k g . % a d = %butyl phosphite, 120-kg. load Tributyl phosphite, 100-kg. load
-
September 1950
INDUSTRIAL AND ENGINEERING CHEMISTRY
1843
PREPARATION AND TESTING OF ADDITIVES
Redistilled phosphorus trichloride (13.8 grams, 0.1 gram mole) or o x y c h l o r i d e (15.3 grams, 0.1 gram mole) was added slowly, with shaking, to a solution of the alcohol or phenol (0.3 gram mole) in dry pyridine (26 grams, 0.33 gram mole) and dry benzene (40 5.0 30 < 130 200 D‘ Tricetyl phosphite grams, 0.5 gram mole); the 150> 180 5.0 25 < 120 200 D temperature was kept belpw Tricetyl phosphate 120 > 120 IOo C. during the addition of 200 D Trioleyl phosphite 5.0 30 < 150 140 > 150 the halide. After addition of High, good recovery 200 D ‘ Instant Trioleyl phosphate 5.0 30 < 150 120 > 150 t8hehalide the product was reTristearyl phosphite 5.0 30 < 150 200 D fluxed for 2 hours, cooled, 140> 150 Triatearyl phosphate 5 . 0 30 < 160 200 D poured into water (100 ml.), and the benzene layer separated. After repeated washing with water to remove pyridine, the benzene extract waa dried over ignited sodium sulfate and the benzene distilled a Some of the additivea had low solubilities in the oil, and this preoluded kats at higher concentrations. , off. T h e p r o d u c t s w e r e purified by distillation under reduced pressure or recrystallized from a suitable solC. Sulfur type shows no seizure, even at high loads, and the vent,. Certain thiophosphites were prepared from the approfrictional torque is uniform for the test period. priate mercaptans by this method. Thie method is essentially D. Chlorine type, characterized by rapid seizure and equally as described (8); trichloroethyl alcohol was prepared by the rapid recovery from seizure, with a low frictional torque after seizure. method aa described (9). Blends of the additives in high viscosity index solvent refined In addition to referring any friction-time curve to its standard oil of 65 seconds (Redwood) viscosity (Duo-Sol 65) were prepared type a brief description of its main characteristics is given. This and subjected to the standard short duration test in the four-ball method of presentation is preferred as it gives an over-all picture machine. of the friction-time relation, rather than consideration to the preseizure or postseizure regions alone. EFFECT OF ADDITIVE CONCENTRATION ON WEAR Measurements of the mean wear diameter of the roughly circuBlends of 0.5 to 5 weight % ’ of tributyl phosphite, tributyl lar wear spots produced on the test balls are also made during the phosphate, tricresyl phosphate, and trixylenyl phosphate were tests. These values, plotted against applied load, give an a p tested and the results obtained, under comparable loadings, are proximately linear relationship, which shows one or more sharp shown in Figure 1, in the form of wear-additive concentration breaks, with a change in slope, when extreme pressure lubricants CUNes. are tested. The slope of the curve is reported as a wear-load The results, illustrated in Figure 1, show that tributyl, tricresyl, ratio-that is, the load in kilograms required to produce a mean and trixylenyl phosphates in mineral oil give decreasing wear wear of 1 mm.; breaks in the curve are shown as a change in this with increasing additive concentration up to a certain value, and ratio, the load at which the change occurs being specified. A at higher concentrations show increased wear, whereas tributyl higher ratio refers to a lower wear so that improved performance phosphite shows a sharp decrease in wear up to a concentration of of the lubricant is indicated by a high value. 1.5 weight yo,with little increase in wear at higher concentrations. In rating extreme pressure lubricanta on their performance in These results confirm the findings of Beeck et al. (1, I) for trithe four-ball machine it is necessary to consider the occurrence cresyl phosphate and suggest that an optimum concentration exand duration of seizure, the frictional torque before, during, and ists for most effective wear reduction with phosphate blends. The after seizure, and the extent of the wear produced in relation to higher wear shown a t the higher concentrations by these phosthe applied load. As none of the data obtained are absolute the phate additives is due to the excessive chemical attack of the results only give a comparison of performance under the test additive, but with tributyl phosphite such attack is not excessive conditions and are not an absolute assessment of the extreme presat the higher concentrations; thus a higher proportion of this sure properties of any lubricant. I n the present work the over-all additive may be used with consequent increased load-carrying performance of the lubricant is considered for purpows of comcapacity of the blend. parison of the test results obtained. The results of the tests on the four-ball machine are reported in The results of Table I1 show that phosphites are superior te the tabular form; this method of reporting the tests waa described by corresponding phosphates as extreme pressure additives at the the author (7). Extended experiments on this apparatus showed same concentration under the test conditions employed. Alkyl that lubricants give friction-time curves of characteristic shape, esters are clearly superior to aryl esters and the long chain esters and these curves, for a series of 1-minute tests, can be referred to appear to be particularly effective. It is probable that, after four main types. reaction with the surface to form a film, the fatty residue funcA. Straight mineral oil type, showing delayed seizure at low tions to some extent like an added fatty acid or ester, giving reloads with a high frictional torque and almost instantaneous seizduction of friction and wear as suggested by Thorpe and Larsen ure at loads above 100 kg. (11). The results obtained for the long chain esters illustrate the B. Oleic acid type, showing almost instantaneous seizure, even value of combining two types of additive in the form of a single at low loads, with considerable variations in the frictional torque.
1844
TABLE 111. EFFECT OF ACIDOR ESTERADDITION ON EXTREME PRESSUREI PROPERTIES OF PHOSPHITE AND PHOSPHATE BLENDS Concn. of Wear-Load Maximum Additive Ratio Load, Type Additive Wt. 5%' Kg./Mk. Kg. curve Tributyl phosphite (5.0 wt. plua 220 Oleic acid (redistilled, setting 5.O 200 point 14' C.) Oleic acid 1.0 200 < 140 200 8 0 > 140 Stearic acid (m.p. 69' C.) 1 .o 200 < 120 170
v)
Palmitic acid (m.p. 6 3 4 ' C.)
1 .O
Naphthenic acids (neutral 1 .O value 230 mg. KOH/gram) Triolein b.p. 2aSo/18 mm., 1.0 0.05% 6 e acid) Ethyl palmitate (m.p. 24' C.. 1 .O 0.01% free acid) Tributyl phosphite (1.5 wt. %) plus Oleic acid 5.0 Oleic acid
Vol. 42, No. 9
INDUSTRIAL AND ENGINEERING CHEMISTRY
1.0
Naphthenic acids 1 .o Tributyl phosphate (5.0 wt. %) plus Oleic acid 5.0 Oleic aoid
1 .o
Stearic acid
1 .o
Palmitic acid
1 .o
Naphthenic acida
1.0
Triolein
1 .o
Ethyl palmitate
1.0
Tributyl phosphate (1.5 W. %) plus Oleic acid 1.0 Oleia acid
1 .o
Naphthenic acids
1 .o
Tricresyl phosphate (5.0 wt. 7%) plus Oleic acid 5.0 Oleic acid
1 .o
Stearic acid
1.0
Palmitic acid
1.o
Naphthenic acida
1.0
Triolein
1 .o
Ethyl palmitate
1.0
Tricresyl phosphate (1.5 wt. %) plus Oleic acid 5.0 Oleic acid
1.0
Naphthenic acids
1.0
Riction-Time Curve8 Frictional torque
Seiiure
None
Low. smooth wear
150
Instant
High, good recovery
170
None
Low, smooth wear
170
Instant
Low, good recovery
170
None
Low, emooth wear
150
< 100 < 100 50 > 100 30 < 100 70 > 100 30 < 100 7 5 > 100 30 < 100 7 0 > 100 30 < 100 4 0 > 100 30 < 100 8 5 > 100 25 < 100
150
Instant
High, recovery delayed
30
150
Instalit
High, irregular wear
Instant
High, good reeovery
Instant
High, prolonged seirure
< 100 eo > 100 25 < 100 6 5 > 100 25 < 100
150
Instant
High, irregular wear
80> 200 < 75 > 200 < 50> 200 < 75>
I20 120 120 100 100 120
120
< 120 70 > 120 150 < I20 75 > 120 150 < 120 eo > 120
200
8 0 > 100 25
4 0 > 100
25 < 100 55 > 100 25 < 100 75 > 100 25 < 100 7 5 > 100 25 < 100 7 0 > 100 25 < 100 5 0 > 100 25 < 100 7 0 > 100 25 < 100 70 100
> 20 < 100 2 0 > loo 20 < 100 5 5 > 100 20 < 100 3 0 > 100
170
200
150
D
150
D
150
D
150
A'
150
A,
150
A I
150
B
150
A
150
B
150
A
100
A
150
A
150
A
150
A
'150
A
150
A
i
150
None
High, smooth wear
150
Instant
High, irregular wear
compound, since they are superior as extreme pressure additives to blendscontainingaphosphiteorphosphateandafattyacidor ester. The results given in Table I11 show that although the addition of fatty acids or esters effects some improvement in the lubricab ing properties of tributyl and tricresyl phosphate blends, the improvement shown by blends of tributyl phosphite, to which acids or esters are added, is considerable. The high wear shown by blends containing 5 weight % of oleic acid is probably due to excessive chemical attack by this acid. Blends containing naphthenic acids give high wear indicating that such blends are highly corrosive and that the iron soaps formed fail to effect wear reduction. The results of Table I11 confirm that acids and esters improve the lubricating properties of blends of phosphites and phosphates by being strongly absorbed a t the surface of the phosphide film, formed by reaction of the additive and the steel surface, giving lower friction and wear. The effect of sulfur on the lubricating properties of phosphorus asters was studied by preparing blends containing 0.6 weight ?6 of free sulfur and various phosphites and phosphates and subjecting these blends to tests in the four-ball machine. The resulta of Table IV prove that the addition of sulfur greatly improves t,he extreme pressure lubricating properties of blends
of both phosphites and p h 0 5 phates. The sulfur functions by reacting to give a sulfide film which has such good antiseizure properties that seizure does n o t occur even under t h e heaviest loads. The high wear shown by 5 weight % blends of tributyl and tricresyl phosphates is probably due to the excessive chemical attack of the additive at the surface. Since chlorine and sulfur, combined in the form of a single additive, show enhanced e x t r e m e p r e s s u r e activity, it was decided to investigate the extreme pressure properties of some thiophosphites and thiophosphates. The reaults given in Table V show clearly the enhanced lubricating properties shown by sulfur and phosphorus suitably combined in the form of a single additive. In general, thiophosphites are somewhat superior additives to thiophosphates, but the difference in extreme pressure activity is lese clearly marked than in the cases of phosphites and phosphates. I n view of the findings of the German workers it was decided to test a few chlorinated phosphitea and phosphates. Previous work (6, 6, 10)has shown the importance of chlorine atoms attached to aliphatic carbon atoms in conferring extreme pressure activity and alkyl esters were therefore tested aa well as aryl wtem. The results shown in Table VI show that chlorinated aliphatic
OF ADDEDSULFUR TABLE IV. EFFECT
(All blends Containing 0.6 wt. % sulfur) Phosphorus Additive Trimethyl phosphate
Concn. of Additive, Wt. %
Wear-Load Ratio
1.0
60 < 150 350> 150
Kg./Mk.
60 < 150 340> 150 400 290
Triethyl phosphate
1.0
Tributyl phosphite Tributyl phosphite Tributyl phosphate Trioctyl phosphite
5.0
Trioctyl phosphate Tricetyl phosphite
5.0 5.0
300 < 150 300 90< > 150
Tricetyl phosphate
5.0
300
Trioleyl phosphate
5.0
Trioleyl phosphate
5.0
Tristearyl phosphite
5.0
Tristearyl phosphate
5.0
1.5 5.0 5.0
85
< 150 9 5 > 150
360
120 > 150 < 150 110 > 150 300 < 150 130> 150 3CO < 150 120> 150 300 < 150 130 > 150 300 < 150 120> 150
Maximum Load, Kg.
Type FnctionTime
200
Curve" C
200
C
250
200 200 200
C C C C
200
200
C C
200
C
200
C
200
C
200
C
200
C
Triaresyl phosphate 1.5 300 200 C Tricresyl phoaphate 5.0 125 200 C Triphenyl phosphite 1.0 330 200 C 200 C Triphenyl phosphate 1.0 320 a There wag no seizure: frictional torque was high with smooth wear.
Saptember 1960
Additive (Wt. % Blends)
INDUSTRIAL A N D ENGINEERING CHEMISTRY
WsrrLoad Ratio. Kg./Mm.
Maximum
125 115 140
2W
170 170 160 I50 120
1x5
Lord.
K8.
'Type
Motlon-
Time
C"W*'
m m
2W
2W ZW
ZW
m
uxl
A
B
phosphites and phosphates, particularly those compounds oontsining B C 1 r - C group, are useful extreme pressure additives and me somewhat superior to aromstic compounds. The chlorinated sliphatie compounds are partieularly effective at low conoentrations. Addition of sulfur to ohlorinsted phosphite and phosphate blends improves the lubricating properties and has the effect of preventing seizure. M ~ A N I S M O F A ~ I O N O F P H O S ~ O R U S E S T EAR SS EXTREME PRESSURE ADDITEYES
C D Beeek and his =*workers ( 1 , 8 ) have shown the formstion of imn phosphide when iron, carbon, and trieresyl phosphate w e Figwe 2. Wear Spots of Mineral Oil, Phosphite, and heated together and have suggested that lubricants containing Phosphate Blends thin ester react with steel aurfnces to give a phosphide film, which A mio-ekl65 oil W - 4 . L0.d R 2 rt. % Ui-yl pho.ph.to t6X-b. lord ahesm 88 a liquid imn-phosphorua eutectic. The German workC 1 R. % cribufy1 phowh.to'lOm3-b. load D 2 Xt. % Itibufil pho(lphlte,'%b. load ers have ahown that test balls, preheated in blends of phosphorus compounds in mineral ail. gave an improved perforrnsnoe in the four-ball machine, wing straight mineral ail as lubricant. This blends, using test batla mated with iron BOBPS. The results of finding has been confirmed: test bells, preheated in the neat such teats are given in Tsble VIII. edditives, showed blaekened surfaoes and these surfaoe films were Tests an bslls coated with B ferrous wlfid.de film show that the smoothly worn EWSY on test, exposing bright metel at the wear improved extreme p r w w e properties shown by blends containing mte.. The results ofsuch tests are given in Table VII, sulfur and a phosphite or phosphate are due to the formstion of B T h e similarity of the results of Table VI1 shorn that the fdms sulfide-phosphide fdm and the results obtained, shown in Tsble produced by various additives are dike in oomposition since all IX, suggest that sulfide film may facilitate the sttaek of phoe the filmsshow almost identical wesr and friction eharacteriatica. phorus additives to form 8 phosphide film. The black film, produced on teat balls by hating with the neat additives, were readily soluble m dilute nitric acid, sod the solution obtained, after filtration, gave B positive teat for phosphorus in all e-. All the phosphite and phoe phates tested were found to m o t vigorously with iron Triehlomth 1 p h e hate 1.0 2W 250 D cCi.cH,.c~,.o)..50 powder st temperatures below Tri tr,ehlorwthyl) phaaphite 1.0 500 300 D (bk!H,.O)..P Zoo' C., and the residues, d t e r Tri tnnohloroethyi) PhosDhsta 1.0 450 3W D removal of the additive by excb.'.C.Clr..O),.PO 175 3W D traction with ben~ene, conInstant Nigh. repid recovsly 200 250 D > I d 0 kz. tained phosphorus. In certein caeee the presenoe of a p h w 420 3W D phide in the residue w s estsblished by the liberation of phosphine with dilute hydroehlorio acid. Since the improved lubrieatTtiablorosthyl phepbata 1.0 250 250 c ing properties shown by blends S40 300 C m m c of phosphite0 and phosphates 0.25 450 250 C in the presence of added fatty 0.25 400 250 C. Nons Bmoolh "ear thrwghout sei& might be due to the forphe. 1.0 280 230 c mation of imn BOSpa, formed 270 250 C hy the reaction of the acid with the surface, it waa decided to test phmphite. and phosphste
---
INDUSTRIAL A N D ENGINEERING CHEMISTRY
1846
"
Y
A B C
D
---
Figure 3.
~~~
Wear Spots
S wr. % mhtxtyl phaph-to pllrs 5 R. % oldo arid blend,
lmq.
load T-f hU.mated4 t h iron ol-to uul ldti-tal 4 t h 5 m. % t b b v n l phaph.t. blood lmq. load I XI % .uiphemrl thioph'oe hit= blond 2W-La. l a d Sq6 UiolorB phosphite pllu 8.6 m. .$fur hlcnd. 2ackc. 10.d
The results given in Table I X confirm the improved adsorption meohanism proposed hy Thorpe and h n ( I I ) . I t hsa been found that the addition of sulfur to blenda of tributyl phosphite, tributyl phosphate, aod tricreayl phosphrtte decresaes the liberation of wid by these additives in heating tests,and this effect is of obvious in the meohanism ,f actionof blends of these compounds in presence of sulfur. ~l~~~ of these (5 weight %)were heated to 2 0 0 O C. with 10 weight %of iron powder, alone and in presence of o,6 weight % of sdfur *). Neutralisation values were determind at the beginning and at the end of the tests.
TABLE VII. T E BON~ B A LPREHEATED ~ FOR 30 MINCTBSIN NEATA~ornvnsAT 200" C . (D~o.SolS5oil ee 1ubtio.x.t)
Wesr-Load
Maximum
Additive Trimethylpbwn&t, pbas h ~ t r Tributyl Tribntyl phosDhh.te Triaresyl phosphite Trioray1 p h a p b i t s
Kg./Mm.
Xg.
20 25 20
I20 120
* Thsra w- w #ais-:
TYOC
Friction. Time
Loed.
Rstio,
C",,* C C
120 120 120
22 20
frictiond tarpue
WM
C C
C
hieh Mith rmooth wwr.
TABLE VIIJ. TEST^ ON BALLS COATED WITH ( 5 rt. %
blends of additive)
We*,-
arrp
Additive
Imn ots.ta Imn oluits Iron a h n i t s Iron ps1mit.b Imn olphtheolits Ima naphthsnsta
Tributui pharphite Tributyl phaapbits Tt3ianayl &aPbts T r i a ~p~h le ~ b t e Tributyl phaaphiits Trimyl pbaphsb
Load Madmum XRstitio. ~ . l M r n . Load, Kg. ZW 150 85
en
150
150
150
KI
120
85
Vol. 42, No. 9
~~
~
~
~
~
Ad&tive, Ratio. Lad, Time Additive Wt. ?& KdMm. Ks. Curve Cbloriositsd -u 1.0 r(.% Trimethyl h& b i t s 1 .o ZW D D Trib"tY1 .L,&ta 1.6 250 250 ZMI D Tributyl pbaspbcs 1.5 Tricrssyl pbmphita 250 1.5 230 D D Ttioresyl pbwphata 1.6 180 250 Chloride film on h t bdla 180 Trimethyl p h a p b t s 1.0 D D Tributul phosphiits 1.5 170 2w 200 D Tribvtyl ~ b a r ~ b t a 1.5 Trioreall pbosplmts 1.5 1m 110 2w D a 8eirure ~ i n a t a n t a n s o u asbove 1 w kp.: f ~ i a t i e d ww high *ch
rspidreaove~~
Thiophosphites and thiophowhates, done or in oil, react vigorously with iron powder at 200' C., and the residue, after heating for 2 hours, in all ewes contains sulfide and phosphide; ohtorinated phowhorus &era, hested under similar conditions with iron powder, give residues containing chloride and phosphide. T-tz on blends of chlorinated par& wax and phosphite or phosphate gave results similar to those obtained with blends of chlorinated phoaphow estara. Test balls, coated with a preformed ferrous chloride a m , gave similsr results with B phosphite or phosphate
lubricant' re8u'ts' *Own in Table that chlorinatedphosphorus e4ters effectlubrication by mews of a ohloride-phosphidefilm. Photogrsphs of typioal wear spots obtained on test balls have been obtained, aod examples of these &reshown in Figures 2 and 3. Such photogrsphs provide useful information 88 to the type of wesr produced in tests using various additives. Figure 2 shows olearly that blends of qhoiphates fail to protect the surfaoe against wear and the surface damage is e h i l a r to that &own by a straight minersf oil, whertrihutyl phosphite blends give much lower wear at higher IRON SOAPS loads with far less damage to the surisee. Mation-Time Curvea
%$ c
C
Frictions1 tOn9"B
Seizure None
Low, smooth wear
irons
High, smooth weir
CONCLUSIONS
The conclusions to be drawfrom the present work may b summarized 89 follows: A. Phosphites and p h w phates show extmrne p m s 8 u ~
September 1950
INDUSTRIAL AND ENGINEERING CHEMISTRY
a d v i t y when blended in mineral oil; phosphites are superior to phosphates, and long chain aliphatic esters are superior to aryl esters. B. The addition of fatty acids esters, or sulfur improves the extreme pressure properties of bfends of both phosphites and phosphates. C. Chlorinated phosphorus esters, thiophosphites, and thiophosphates are useful extreme pressure additives. D. Phosphorus esters effect lubrication of steel by reacting chemical1 to form phosphide films which are smooth1 worn a r a y . dters containing chlorine form chloride-phos hi& films, but those containin sulfur form a sulfide-phosphide E. I n eneral t t e extreme remure activity shown by phoshites an{phos$ates is of ayower order than that shown by h o g e n - s u ur a itives but is of the same order as the lead soapsulfur type additive.
fik.
ACKNOWLEDGMENT
The author wishes to express his thanks to Albright and Wilson, Ltd,, for gifts of chemicals and to Shell Refining and Marketing Company, Ltd., for the use of facilities to carry out teats on the four-ball machine,
1847
LITERATURE CITED (1) Beeck, O., Givens, J. W., and Smith, A. E., Proc. Roy. SOC. (London),A177, 90 (1940). (2) Beeck, O., Givens, J. W., and Williams, E. C., Ibid., A177, 10a (1940). (3) Bowden, F. P., and Tabor, D., Ann. Repla. on Progrees Cham. (Chem. Soc. London), 42,20 (1945). (4) Davey, W., END. ENQ.CEEM.,42, 1837 (1950). (6) Davey, W., J.Inst. Petroleum, 31,73 (1945). (6) I W . , 32, 575 (1946). (7) Ibid., 33, 574 (1947). (8) "Organic Syntheses," Collective Vol. 11, p. 109, New York. John W h y & Sons, 1943. (9) Ibid., p. 598. (LO) Prutton, C. F., Turnbull, D., and Dlouhy, G., J . Inat. Petroleum. 32, 90 (1946). (11) Thorp, R. E., and Larren, R. G., IND.Em. CHEY.,41, 958 (1949). (12) Tingle, E. D., J. Inat. Petroleum, 34, 743 (1948). (13) West, H. L..Zbid., 34,774 (1948). RH~CEIVED November 23, 1949.
Amine Activation of 41' F. Butadiene-Styrene Copolymerization ROMAN SPOLSKY AND H. LEVERNE WILLIAMS Polymer Corporation Limited, Sarnia, Ontario, Canada
The use of polyamines with or without heavy metal salts or digested dextrose as activator for the polymerization of butadiene and styrene in emulsion at 41' F. has been investigated. The purified metal complexes with (ethylenedinitri1o)tetraacetic acid were not superior to the impure materials. A number of polyamines were found to be suitable activators in the absence of ferrous sulfate but were generally better when some ferrous iron was present. However, the effectiveness of the polyamines dropped rapidly in the absence of sugar. By adjustment of the concentrations a suitable recipe was developed using tetraethylenepentamine as sole activator. Its effectiveness was enhanced by sugar but diminished by ferrous iron under these experimental conditions. No suitable sugar-free recipe activated with (ethylenedinitri1o)tetraacetic acid alone was evolved in contrast with the results obtained at lower polymerizationtemperatures.
T
H E essential change in the polymerization recipes required for the production of cold rubber was the replacenient of the potassium persulfate initiator used in the production of GR-S by a more complicated redox initiatory system. The new systems are usually composed of cumene hydroperoxide (CHP), ferrous pyrophosphate, and often digested dextrose. Many variations of this initiatory system have been studied. Although improved hydroperoxides are a suitable means of advancing cold rubber technology there has also been some interest in new activators for the decomposition of hydroperoxides (7, 8). The earlier paper in this series (7) described the use, in conjunction with alkali and dextrose, of a number of heavy nietals complexed with various chelating agents. In the course of this work it wee observed that the chelating agent (ethylenedinitri1o)tetraacetic acid was an activator. in the absence of heavy metal ion. Horner (6, 8 ) subsequently reported that
tertiary amines such as dimethylaniline activated the bulk polymerization of styrene using benzoyl peroxide, and that primary and secondary amines were inhibitors of such polymerization. W'hitby (IS) showed that in the emulsion polymerization of styrene and of styrene and butadiene a t 10" C. polyalkylene polyamines were highly effective activators of polymerization without heavy metal salts or sugar. The data below extend t h e polyamine activation to a commercially used 41' F. recipe and clarify some of the interrelationships between the heavy metal, polyamine, and sugar. EXPERIMENTAL
The techniques were essentially the same as those in the earlier report (7). The recipe used approximates type X-478. I n general the aotive ingredients were as follows: Butadiene Styrene Water MTM-4 Dresinate 214 Daxsd 11 KCl
Parts 72 28 180
0.24
4.7 0.1 0.6 0.09
0.1
1 .o
0.10
0.028
The only change was to replace the ferrous complex by the appropriate experimental activator. Other changes will be noted below. Materials, from the sources indicated, were used am received but concentrations refer to pure active ingredients. The effect of metal salts in the presence of Kalex K [%yoaqueous solution of potassium (ethylenedinitri1o)tetraacetate from Hart Products Company of Canada Limited] on the p o l y m e h tion rate was reported earlier (7). Since the preparation of the complexes by mixing Kalex K and metal salt solutions waB not uniform it was felt that the use of pure complexes would give more reliable results. One-half millimole of metal complexes
