Neutral and Basic Sulfonates CORROSION-INHIBITING AND ACJD-DEACTIVATING PROPERTIES HAYWARD R. BAKER, CURTIS R. SINGLETERRY, AKD EDWIN M. SOLOMOR’ Kava1 Research Laboratory, Washington, D .
0
IL-soluble naphthenates and sulfonates derived from the refining of petroleum products have been extensively used as additives for lubricating oils to secure rust inhibition, detergency, or increased load-carrying capacity. The petroleum sulfonates, or mahogany soaps, began to be used as oil additives in the 1930’s, and during World War I1 their use for rust inhibition and as detergent additives expanded manyfold. The most effective sulfonates available were byproducts of the chemical refining of white oils, and the wartime demand quicli!y exceeded the total supply. This supply was supplemented by recovery of oil-soluble petroleum sulfonates from other refining operations, but the effort to recover the largest possible amount of oil-soluble soaps led to the marketing of products of lower molecular weight and diminished stability and effectiveness. Recovery from a wider range of crudes contributed further to variability in the product. In consequence, field experience with such additives was sometimes disappointing, because the sulfonate used for production did not correspond to the laboratory sample on which the formulation was based. Not only was the rust-inhibiting action erratic, but some or all of the additive sometimes separated from the oil during storage, possibly because of the inclusion of low molecular weight sulfonates of limited oil solubility, possibly because of the presence of several per cent of carboxylic acid soaps. Certain otherwise stable carboxylate soaps have been shown (13) to precipitate when the oil-soap system is saturated with water or exposed to high relative humidities. This same variability made i t exceedingly difficult to do significant research on the mechanism of inhibition or of detergency or on the factors controlling the stability of dispersions of petroleum sulfonates in oil. I t was therefore apparent that if a synthetic oil-dispersible sulfonate of definite and reproducible structure could be prepared, that wab comparable with the best oil-soluble petroleum sulfonates in rust inhibition or detergency, the road would be open for definitive basic research on the mechanism of sulfonate action. Studies of the general constitution of the oil-soluble sulfonates (1, 5, 6, 8, 17-19) have indicated that they are characteristically fused-ring polycyclic compounds with aliphatic side chains of considerable size. At least one of the rings is aromatic, and this ring is the most probable point of attachment for the sulfonate group. Practical experience indicates that the acids whose alkali or alkaline earth soaps are most effective in rust inhibition have molecular weights between 400 and 500. Baker and Zisman (6) established that barium octadecyl benzene sulfonate was an effective rust inhibitor. Their octadecylbenzenesulfonic acid, containing a branched octadecyl radical, was synthesized by the Eastern Regional Research Laboratory of the Department of Agriculture a t the suggestion of the Naval Research Laboratory, but by a method which was not suitable tor large scale production. This laboratory then investigated the sulfonation of alkyl-substituted naphthalenes. Monononylnaphthalenesulfonic acid was prepared; its salts were found to be oilsoluble and to have definite though not outstanding rust-inhibiting properties. Later, i t was learned that an industrial concern was synthesizing dinonylnaphthalenesulfonic acid for use as a rubber plasticizer and the company was invited to submit samples of the acid and of the sodium salt for study. The sodium
C.
salt was found to have definite though not unusual rust-inhibib ing power, but a barium soap prepared from it a t this laboratory was found to be comparable in effectiveness with the best barium petroleum sulfonates commercially available (4). The sodium and barium salts of dinonylnaphthalenesulfonic acid (DNNS) are, in the pure state, nearly colorless, brittle solide which can be obtained either as a glassy residue by the evaporation of a volatile solvent or as a friable porous mass by the e v a p oration of frozen benzene solutions in vacuo. The dinonylnaphthalenesulfonic acid is probably a rather complex mixture of isomers; the soaps are amorphous rather than crystalline in structure. The sodium soap is soluble in water, acetone, alcohol, carbon tetrachloride, petroleum ether, cyclohexane, and benzene, as well as in petroleum, diester, and polyalkylene oxide oils. I t is also soluble in polymethylphenylsiloxanes carrying either a moderate or high proportion of phenyl groups, but it is not soluble in polymethylsiloxanes. The barium dinonylnaphthalene sulfonate differs in solubility from sodium dinonylnaphthalene sulfonate chiefly in being insoluble in water. The “solutions” in nonpolar solvents and in water are micellar in nature; (14) the state of dispersion in such intermediate solvents as alcohol or acetone has not been established. The dispersions of barium dinonylnaphthalene sulfonate in petroleum and diester oils are completely stable, the oils remaining clear even when exposed to relative humidities of 80% or higher. Such humidities cause the precipitation of oil-soluble carboxylate soaps such as the calcium aryl stearates and the partial or complete separation of the majority of the petroleum sulfonates from oils. Sodium dinonylnaphthalene sulfonate in benzene solution is not precipitated even by contact with small amounts of free water for periods of 2 months. It also mas found easy to prepare basic soaps of dinonylnaphthalenesulfonic acid by overneutralization with barium hydroxide. These soaps, which give clear and stable dispersions in petroleum oils, are of especial interest because they may supply an alkaline reserve in the oil for the neutralization of corrosive organic or sulfur acids formed as a result of fuel combustion or oil oxidation, or of halogen acids arising from the antiknock additives in motor fuels (9, 10, 16, 60-22). This report presents the results of an evaluation of the neutral dinonylnaphthalene sulfonates as rust inhibitors in petroleum and in diester oils, and of an exploratory investigation of special properties of the basic barium soap as a rust inhibitor in acid environments. MATERIALS AND EXPERIiMENTAL TECHNIQUES
The inhibitor materials used in this investigation were ag follows: 1. Sodium (mahogany) petroleum sulfonate H, a commercial product. This was a highly refined material with an average molecular weight of about 450. The petroleum sulfonate selected as a reference was one whose barium salt had been found to give the best inhibition of any commercially available petroleum sulfonate preparation which this laboratory has had an opportunity to examine. It was used in the form of a 62% dispersion in a mineral oil. 2. Barium (mahogany) petroleum sulfonate was prepared
1035
Vol. 46, No. 5
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
1036
prepared by this method was inthstinWishab1e in rust inhibition from thdt T ~ B L EI. RUST-~XHIBITING PROPERTIES OF SYXTHCTIC BARIUM DINOVYLN ~PHTHALESE Prepared according to ( 5 ) . SCLFON ITE AND BARIUM (MAHOGLNY) PETROLEUM SULFOSATE IN VARIOCSL U B R I C A ~ T S (Static mater-diop test method, distilled water a t 140' F All soap concentrations are repoi ted Corrosion Rating on a dry soap basis. after Exposure Sctive The lubricant bases utilized included 24 48 96 168 Teat Ingredient, TO. Rust Inhibitor Wt. w Lubricant Base hr. *r. ilr. Detroleum oil grade 2135. the synthetic 1 Sone ,.. 2133 petroleum oil 10 ,, , . ... diester bis(2-ethylhexyl) sebacate con0 0 0 0 taining 0.25% ~-tert-butyl(2-plienyl2 Barium mahogany sulfonate 0.025 2135 petroleum oil 0 1:92 I/,# 1/4 3 Barium mahogany sulfonate 0.012 2135 petroleum oil phenol) as antioxidant, a polgalkyierl? 0.05 2135 petroleum oil 4 Barium DSXS o o 0 11s oxide (water-immiscible, Type 250) con0.023 2135 petroleum oil 3 Barium D S N S 0.0123 2138 petroleum011 0 Barium D N N S ' " ''' "' taining 2.0% phenyl-1-naphthylamirie Yone 10 ,.. . . ... as antioxidant, and t x o commercially available polgmethglphenyl siloxanes, Bis(2-ethylhexyl) 0.1 Baiium mahogany sulfonate sebacate" 0 0 0 0 Type 550 (100 cs.) of medium phenyl Bis (2-ethylhexyl) 0 05 Barium mahogany sulfonate o 0 0 o content and Type 710 (500 cs.) of high sebacatea Bis (2-ethylhexyl) 0.023 Barium mahogany sulfonate 0 0 I;* l/'a phenyl content (6, 6, 16). sebacatea Bie (2-ethylhexyl) 0 1 Barium D N N S Special care m s taken to prevent 0 0 0 0 sebacateQ accidental Contamination of all appa0.0: Bis(2-ethylhexyl) 1 2 Barium DNNS ratus and materials, as ever1 minute sebacate" 0.025 Bis(2-ethylhexyl) 13 Barium DWKS traces of impurity can obscure corrosion sebacatea 0.012.5 Bis(2-ethylhexyl) 14 Barium D N N S results in working with fiurfacc-active 0 0 l/'a sebacateQ materials. ,,, Polyalkylene oxide6 IO ... . . IS Sone The effectiveness of the synthet,ic 16 Barium mahogany sulfonate 0.5 Polyalkylene oxideb 0 0 0 0 o .id I 3 arid of the petroleum sulfonates was li Barium mahogany sulfonace 0.25 Polyalkylene oxide& o 0 0 0 evaluat,ed by the use of three previously 18 Barium DKXS 0.5 Polyalkylene o x i d d 19 Barium D S N S 0,2: Polyalkylene oxideh standardized techniques: the s t a t i c ,, , Polymethylphenylsiloxane 20 h'one (medium phenylation) 10 ., . . , ,.. mater-drop test (6) 1 1 ) , the NRL fog 21 Barinm mahogany sulfonate 0.2 Polymethylphenylsiloxane cabinet test (5, l a ) , and the galvanic (medium phenylation) c .. , .. , ,, , corrosion test employing a brass-steel 22 Barium mahogany sulfonate 0,l Polymethylphenylsiloxane (medium phenylation) c .,. , . . ,.. couple (5). These tests p re re supple0 2 Polymethylphenylsiloxane "3 Barium D N N S mented either by modifications or by (medium phenylacion) 0 1 Polymeth ylphenylsiloxane 24 Barium D N N S special tests d e s i g n e d t o m e a s u r e (medium phenylation) 0 0 0 0 specific properties of the sulfonates 0 05 Polymethylphenylsiloxane 2.5 Barium D S N S (medium phenylation) O more precisely.
-
'
, ,
'
20
Sone
2;
Baiium mahogany sulfonate
Polymethylphenylsiloxane (high phenylation)
.. .
..
For the study of rust inhibition a l k a l i n e barium dinonylnaphthalene c ... . . . sulfonate the static water-drop test was 28 Barium mahogany su1fona:e 0 1 .. . , modified by substituting dilute solutions of organic or inorganic acids, or of synthetic sea water, for the distillcd water drop of the standard method. 0 0 0 0 Acid vapor exposure tests were con0 ducted by preparing steel coupons 5 s for the fog cabinet test, and suspenda Contains 0,25% 4-lert butyl(2-phenylphenol) as antioxidant. ing them by glass hooks in a desiccator. b Water-immiscible t y p e containing 2.070 phenyl-1-naphthylamine as antioi[idant. over aqueous solutions containing from C Insoluble in lubricant base. 0.1 to 1.0% glacial acetic acid. T h e tests were conducted a t 80" i 2" F. The possible corrosive effect of thest, addit'ives on nonferrous metals K : I ~ from the sodium salt by double decomposition using barium studied by exposing them to an assembly of coupons 1 inch chloride. The sodium soap was equilibrated repeatedly with square by */a2 inch thick of a magnesium alloy, an aluminum an excess of barium chloride solution and the resulting dispersion alloy, copper, cadmium-plated steel, and steel in series electrical of the barium soap in oil was washed with water until it was free contact in the order named. The specimens, tied together nitli of chloride. It was used in the form of a 38y0 dispersion in a a previously boiled and dried cott,on cord, were immersed in the test fluids for 30 days a t 170" F. mineral oil. 3. Synthetic dinonylnaphthalenesulfonie acid was received The storage stability of the inhibited oils (6, 7 , 13) was inveyand used as a 45% solution in petroleum naphtha (equivalent tigated in an accelerated test which this laboratory had found m eight found 463; theory 460.4). to correlate well with field experience. Approximately 20 grams of the inhibited fluid composition was placed in a low-form 1004. Sodium dinonglnaphthalene sulfonatewaspreparedfrom the acid by reaction with sodium hydroxide. It was prepared in the ml. borosilicate glass beaker and stored in a desiccator over a solid state by freeze-drying from benzene solution and drying saturated solution of ammonium sulfate a t room temperature. under 0.1-mm. vacuum a t 70" C. It did not contain titratable This solution maintains a relative humidity of about 81%. Obamounts of free acid or base. This lyophilized form of the solid servations were made daily for the first 10 days and then at 10-day was almost instantly soluble in all common solvents as m l l as in intervals for another 50 days. The results n-ere recorded as the petroleum or in diester oils. day on which a sediment or precipitak was first detected. 5 . Barium dinonylnaphthalene sulfonate (neutral) was prepared from the sodium salt by double decomposition with barium chloride, as for (2). It did not contain titratable amounts of free acid or free alkali. It was stored and used as the lyophilized solid. The rust inhibition by neutral dinonylnaphthalene sulfonates 6, Barium dinonylnaphthalene sulfonates (neutraland basic) was investigated by comparing the performance of the reference were prepared from the sulfonic acid by reaction with barium hypetroleum sulfonate v i t h that of the corresponding dinonyldroxide. They were used in the form of a 50% solution in a mineral oil. The neutral barium dinonj-lnaphthalene sulfonate naphthalene sulfonate in thr static water-drop test, the KRL 0 2
Polymethylphenylsiloxane (high phenylation) Polymethylphenylsiloxane (high phenylation)
10
,
.
,
May 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
1037
on the other hand, dissolves freely in
TABLE11. RUST-INHIBITIKG PROPERTIES O F BARIUM AND SODIUM (MAHOGANY) either the medium or highly phenylated PETROLEUM SULFONATES ARD SYNTHETIC BARIUM AND SODIUM DINONYLNAPHTHALENE polyphenylmethyl siloxanes, and gives SULFONATES I N PETROLEUM OIL AND I N BIS(2-ETHYLHEXYL) SEBACATE
complete protection against rusting when present in concentrations of 0.1% or higher (Table I, tests 20 to 25). Active Using both diester and petroleum oils, Ingredient, Test Lubricant Base s o Rust Inhibitor Wt. % the relative effectiveness of the sodium 2135 petroleum oil 32 Sone 1 1 1 as well as the barium salts of the 2135 petroleum oil 48 40 54 2 33 Sodium mahogany sulfonate synthetic and the petroleum sulfonic 48 48 60 3 Sodium mahogany Bulfonate 34 acids were evaluated in the leaching en24 32 28 2135 petroleum oil 2 Sodium D N N S 3: 32 40 32 3 Sodium DA-NS 36 vironment of the NRL fog cabinet. As 120 144 144 2135 petroleum oil 2 Barium mahogany sulfonate 37 was to be expected, the sodium salts of 168 192 168 3 38 Barium mahogany sulfonate both types of acid were much less satis168 192 168 2 2135 petroleum oil Barium D N N S 39 factory than the corresponding barium 216 240 240 3 40 Barium D N N S 1 1 1 salts in either oil (tests 32 to 36 and Bis(2-ethylhexyl) sebacatea None 41 Bis(2-ethylhexyl) sebacateO 24 36 24 41 to 45, Table 11). Sodium dinonyl2 42 Sodium mahogany sulfonate 36 36 48 3 Sodium mahogany sulfonate 43 naphthalene sulfonate, because of its 16 16 Bis(2-ethylhexyl) sebacate4 2 16 Sodium D N l i S 44 good water solubility, gave even shorter 23 24 24 3 Sodium D N N S 45 protection than the reference sodium 96 72 72 Bis(2-ethylhexyl) sebacatea 2 Barium mahogany sulfonate 46 144 120 120 3 Barium mahogany sulfonate 47 petroleum sulfonate. When the barium 120 120 120 Bis(2-ethylhexyl) sebaoatea 2 Barium DNNS 48 salts were examined, however, barium 168 192 216 3 Barium D N X S 49 dinonylnaphthalene sulfonate showed a 1 1 1 Bis(3-methylbutyl) adipateb 50 None clear-cut superiority over the barium 48 48 48 2 Bis(3-methylbutyl) adipateb Barium mahogany sulfonate 51 petroleum sulfonate in both the petro96 72 72 3 52 Barium mahogany sulfonate leum oil and the bis(2-ethylhexyl) 96 72 72 Bis(3-metbylbutyl) adipateb 2 53 Barium D N N S 120 144 120 3 Barium D S N S 54 sebacate (Table 11, tests 37 to 40 and 46 to 49). The same relative effectiveness was noted in the extreme low temperature diester oil, bis(3-methylbutyl) adipate, although both the spnthetic and the petroleum soaps gave shorter lived protection in fog cabinet test, and the brass-steel galvanic corrosion test. The this low-viscosity fluid (Table 11, tests 50 to 54). tests explore distinct aspects of the inhibitory process and so A brass-steel galvanic corrosion test was developed (3) in supplement each other for the purposes of a general evaluation. connection with the study of an unusual corrosion phenomenon The static water-drop test simulates those conditions in which noted in lubricated bearings during storage at moderate or lo^ minor volumes of condensate adhere to the steel in the presence humidities. It was concluded that a hygroscopic impurity was of excess oil. The fog cabinet, on the other hand, exposes a suroriginally present in the oil or additive, or was formed by reaction face coated with a thin layer of oil to continuous leaching action with the metals present. During storage this impurity accumuby the fog droplets that impinge upon it. The performance in lated enough moisture at the oil-metal interface to set up localthe fog cabinet therefore reflects the relative solubility of the ized galvanic corrosion. The effect was more marked in the presadditive in water as well as its inherent rust inhibiting qualities. ence of petroleum sulfonate rust inhibitors than in their absence, When compared by the static water drop test, barium dinonyland was tentatively attributed to some constituent of these addinaphthalene sulfonate was found slightly less effective a t very tives. low concentrations in petroleum oil than the reference barium When submitted to the galvanic corrosion test, none of the petroleum sulfonate (Table I, tests 2, 3, 5, and 6. A corrosion series of dinonylnaphthalenesulfonic acid inhibitors showed any rating of 0 indicates no rusting and a rating of 10 corresponds to corrosive effect, while the steel specimen was found to corrode in a complete rusting of the surface tested. Because the more the presence of the barium petroleum sulfonate. This result effective rust inhibitors usually fall between 1 and 0 in rating, supports the earlier conclusion that an impurity in the barium further differentiation in performance is obtained by subdividing pelxoleum sulfonate may have been responsible for the difficulties this interval into fractional ratings of 1 1 2 , I/&, l/16, and I/$*; that had been encountered in storage. the last of these designations corresponds t u the smallest detectable amount of rusting.) However, concentrations of inhibitoi below 0.05% are rarely used in practice because of the need foi RUST INHIBITION BY BASIC SOAPS IN ACID ENVIRONMENTS an adequate reserve supply of inhibitor; at higher concentraThe possible usefulness of basic barium salts formed by overtions either the reference petroleum sulfonate or the barium neutralization of dinonyluaphthalenesulfonic acid with barium dinonylnaphthalene sulfonate gives complete protection under hydroxide was investigated by a study of the preparations whose the conditions of the test. I n the diester oil, bis(2-ethylhexyl) compositions are given in Table 111. This is a graded series of sebacate, the synthetic sulfonate appears slightly better than soaps, in the most basic of which (No. 5) the proportion the reference soap (tests 9, 10, 12, and 13), although the differof Ba(0H) (DNNS) reaches 89 mole %, the remainder ence is comparable with the experimental error of the method being taken as Ba(DNNS)z. (This method of describing the In the case of the polyalkylene oxide (water-immiscible type), composition should not be understood to imply that the actual much higher concentrations of either type of inhibitor are reorganization of anions and cations in the micelle has been dequired for effective protection; the reference petroleum sulfonate termined; it merely expresses the stoichiometric relations.) has a slight but definite advantage over the barium dinonylI n some practical situations the hydroxyl ion of the basic soap naphthalene sulfonate when used a t marginal concentrations. might be expected to react with carbon dioxide. This possibility, The two types of sulfonate cannot be compared in silicone as well as some storage problems encountered with the alkaline fluids, because the reference petroleum sulfonate is not soluble soaps in diester oils, led to the inclusion in the series of one soap enough in any of the commercially available silicones to give detectable rust inhibition. Barium dinonylnaphthalene sulfonate, (No. 6 ) which had reacted with an excess of moist carbon dioxide. (Fog cabinet corrosion test method a t 120° F.)
Specimen 1 2 3 Hours before iirst r u t
I . .
INDUSTRIAL AND ENGINEERING CHEMISTRY
1038 TABLE111. SaFple
ho.
a
Vol. 46, No. 5
inhibitor (tests 118 to 124 of Table VI). Samples 4 and 5 , which allowed no rusting in any of the tests presented, were also DINOSYLNAPHTHALENE SULFONATE SAMPLES tested in the presence of 0.054N and 0.0i2N acetic acid; the
COMPOSITION O F BARIUM
Base B a ( 0 H ) D N N S in Soap, xo. Mole %
Treated with moist COS
Sample Present as Ba(DSXS)z, Wt. % 100.0 98.4 95.3 91 .o 87.1 93.6
latter concentration caused immediate reaction, indicating the practical limit of acidity above which this type of protection ie ineffective under the conditions of the test. When 0.012N hydrochloric acid was used in the static waterdrop test, the order of inhibition again paralleled acid neutralizing capacity, although the test in this case is very severe. Static water-drop tests with synthetic sea water 3-ere less severe than those with hydrochloric acid solutions, but again showed a close correlation of protective power with the base reserve of the additive present (tests 139 to 144 of Table 1711). Since synthetic sea water is made up with a p H of 8.2, the mechanism by which a basic sulfonate gives increased protection is not obvious, and deserves further study.
It will be noted from column 4 of Table I11 that because of the great disparity in the equivalent weight of the hydroxyl and the dinonylnaphthalene sulfonate radicals, the actual amount of dinonylnaphthalene sulfonate radical per gram of soap is decreased by only 13% in the most basic sample studied, 80 that MECHANISM INVOLVED I S RUST INHIBITION IN PRESENCE O F equal weights of any of the additives listed will introduce closely CORROSIVE ACIDS comparable amounts of the sulfonic acid component. The performance of this series of soaps was studied in static The mechanism of operation of these basic inhibitors was inwater-drop tests utilizing distilled water, dilute aqueous acetic vestigated in a qualitative way by including a variety of pH indiacid, very dilute hydrochloric acid, or synthetic sea water as the cators in the water drops of the static test. The drop used for aqueous phase. These inhibitors were evaluated in the NRL fog this test has a volume of 0.2 ml.; it is supported on the triangular cabinet, and also by a static exposure to acetic acid vapors. test piece a t such a level that approximately 10 ml. of oil are diTheir tendency to attack nonferrous metals or to promote galrectly available to it by diffusion or by simple convective movevanic corrosion with the brass-steel test couple was also studied. The rust-inhibitory properties of the TABLEIV, EFFECTOF BASICITYOF B.kRIu\f DINOSYLN.4PHTHALCK.E SULFOX.4TE soaps listed in Table I11 were first O N ISHIBITION OF RUSTISGBY DISTILLED WATERIS STATICWATER-DROP TEST observed in the standard static water(Tests run in triplicate a t 1-1-0'F.) drop test in the absence of added acid. Corrosion Rating a f t e r Exposure Inhib. B a ( 0 H ) D N N S Indicated The results recorded in Table IT', tests itor Test in Soap, 48 98 168 Inhibitor, 24 55 to 98, show that the alkaline soaps NO. UsedU Test Oil Iir. hr. br. hr. Mole % wt. r/o containing more than 10% of their 55 None None 10 0.0 2133 petroleum oil . . . ~. barium combined with hydroxyl ion 56 1 0 0.0 0.1 2135 petroleum oil 0 0 0 67 1 0.0 0 0 0.05 2135 petroleum oil 0 0 are effective a t lower concentrations 1 58 0.0 0.025 2138 petroleum oil 0 0 0 '18 0 1 59 0.0 0.0125 2135 petroleum oil 0 than the neutral soap. The enhanced '/B '/Z 60 2 17.4 0 0 0.1 2135 petroleum oil 0 0 protection in this case may well be a 17.4 61 0 2 2135 petroleum oil 0 0.05 0 0 result of the higher p H imparted to the 62 2 17.4 0.025 2135 petroleum oil 0 0 0 '/a 63 2 17.4 0.0125 2135 petroleum oil 0 0 '/a 1/4 water drop by the basic soaps. The 64 3 2135 petroleum oil 4 5 . 2 0 . 1 0 0 0 0 carbonated sample (No. 6) is less effec3 0 65 45.2 0.05 2136 petroleum oil 0 0 0 66 3 45.2 0,025 2135 petroleum oil 0 0 0 0 tive than the comparable alkaline sam0.0125 2135 petroleum oil 0 0 67 45.2 3 0 0 ple (So. 3) but slightly better than 4 68 73.4 0.1 2135 petroleum oil 0 0 n o the neutral control sample (No. 1). 2135 petroleum oil 4 69 0.05 0 0 73.4 0 0 70 2135 petroleum oil 0 0 4 73.4 0.025 0 0 The results in the diester oil are not 4 2135 petroleum oil 0 0.0125 71 0 73.4 0 0 significantly different f r o m t h o s e in 72 5 89.2 2135 petroleum oil 0 0 0 .I 0 0 5 0 0 73 89.2 0.05 2136 petroleum oil 0 0 petroleum. 5 0 0,025 2135 petroleum oil 0 0 0 74 89.2 When the static water-drop test is 0 0 75 5 0.0125 2135 petroleum oil 0 0 89.2 conducted with 0.1% (or O.Ol%V) acetic 6 0 0 76 67.4b 0.1 2135 petroleum oil 0 0 6 0 0.05 2135 petroleum oil 0 0 0 77 57.45 acid in the test drops (tests 99 to 117 6 0 0.026 2135 petroleum oil 0 0 0 78 57.45 6 57.4b 0 0 0.0125 2135 petroleum oil 79 of Table V) the protective qualities of '/a '/d 10 80 None Tone 0.0 Bis(2-ethylhexyl) sebacatec . . . . ... the basic soaps are more clearly differ1 0 81 0.0 0.1 Bis(2-ethylhexyl) sebacatec 0 0 0 entiated. Even 3y0 of the neutral con82 1 0.025 Ris (2-ethylhexyl) sehacatec 0 0 0.0 0 I/# trol soap (No. I) does not prevent 1 0.0 0 0 Bis(2-ethylhexylj sebacateo 83 0.0125 '18 '12 rusting within 16 hours, xhereas corre2 84 17.4 0.1 0 0 0 0 0 0 2 17.4 85 0.025 0 0 sponding concentrations of the strongly 2 17.4 86 0 0 0.0126 1/a '/I 45.2 3 0 0 0.1 87 o n alkaline samples (?;os. 4 and 5 ) allowed 3 0 0 88 45.2 0,025 Bis(2-ethylhexyl) sebacate 0 0 no attack in 7 2 hours, and the less 48.2 0 0 3 89 0 0 0.0125 Bis(2-ethylhexyl) eebacate alkaline samples (Nos. 2 and 3) gave 4 0 90 73.4 0.1 Bis(2-ethvlhexyl) sebacate 0 0 0 complete protection for 24 and 16 n 4 0.025 0 0 0 91 73.4 Bis(2-ethGlhexyl) sebacate 4 0 0 0 0 92 0.0125 7 3 . 4 Bis(2-ethslhexyl) sebacate hours, respectively. The carbonated 93 5 89.2 Bis (2-ethylhexyl) sebacate 0 0 0 0 0.1 sample (No. 6) is as effective in this 5 0 0 0 0 0.028 94 89.2 Bis(2-ethylhexyl) sebacate 0 0 95 5 0 0 89.2 Bis(2-ethylhexyl) sebacate 0.0125 series as the alkaline samples of com6 Bis(2-ethylhexyl) sebacate 0 0 0 0 96 57.4b 0.1 parable acid neutralizing potential. 0 0 0 0 97 6 Bis(2-ethylhexyl) sebacate 57.4b 0.025 0 0 Bis(2-ethylhexylj sebacate 57.45 98 6 0.0126 0 1/8 When the water drop was 0.36N in a For compositions see Table 111. acetic acid, the degree of protection b See Q , Table 111. was again found to parallel the acid C Contains 0.25y0 4-tert-butyl(Z-phenyiphenol) as antioxidant. neutralizing capacity of the added . I
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
May 1954
1039
contact with a 3% solution of a neutral sulfonate in grade 1005 petroleum oil. The data show that such a solution inOF B.4RITM DINONYLNAPHTHATABLE v. EFFECTOF BASICITY LENE SULFONATE ON IRHIBITION OF RUSTING BY 0.018N ACETIC creases the pH of the acid drop from 3.2 to 6 within 2 or .kCID I N STATIC
WATER-DROP TEST
(Additive in grade 2135 petroleum oil run Indi-
in
triplicate a t 25' C.)
r_aI. t e.d-
Test
KO.
Inhibitor Useda
InhibB a ( 0 H ) D N N S itor, in Boap, Mole % Wt. "70
99 100 101 102 103 104 105
Kone 1 1 1 2 2 2
0.0 17.4 17.4 17.4
106 107 108 109 110 111
3 3 3 4 4 4
45.2 45.2 45.2 73.4 73.4 73.4
0.1 0.5 3.0 0.1
0
0
3
7
o3 . 50
0
112 113 114 115 116 117
5 5 5 6 6 6
89.2 89.2 89.2 57.4b 57.46 57.4'~
0.1 0.5 3.0 0.1 0.5 3.0
2 0 0 4
None 0.0
0.0
0.0 0.1 0.5 3.0 0.1 0.5 3.0
Corrosion Rating after Exposure 1 8 16 24 48 7i hr. hr. hr. hr. hr. hr
10 8 118
.., 10 10 0
0 6 1 0 0 5
0
5 0
0 0
0 8
1
'2 5
'/P 0 8 2 0
.. ......... .........
1//4
112
2
..
5
............ 10 0 10 6 0 10 2
0 10 1
0 10 8 0
......... 1/1
1
3
3 hours, in spite of the fact that the neutral barium dinonylnaphthalene sulfonate has no measurable alkalinity. (The pH of distilled water in contact with the soap-oil system showed an equilibrium value of 7.2 to 7.5.) Since only trace amounts of barium ion appear in the aqueous phase during this rise in pH, the disappearance of the acid from the drop must result from solubilization of the acid in the soap micelles in the oil phase, for in the absence of barium dinonylnaphthalene sulfonate the acid drop in contact with petroleum oil does not change in p H (curve VI, Figure 1). The migration of the acidity from the water drop to the soap-oil phase was substantiated when the yel-
......... 10 0
1)'~
3
........ 8 0
10 0
...
0
......... 5 0
10
0
,..
0
......... 10 0
...... 1/2
1
For compositions see Table I11 b See a , Table 111.
a
ments in the liquid above the table provided by the test coupon. fikl I Y Such a drop of 0.018N acetic acid contains 0.36 X 10-2 millimole of acid. The least basic of the alkaline soap solutions (KO,2) I IW' will provide 11.1 X milliequivalent of barium hydroxide in the 20 ml. of oil taken for the test, or about 30 times the amount needed to neutralize the acid in the test drop. Expressed in another way, a sheath of oil 2.2 mm. thick about the water drop I I I I I 1 1 I 2 I 4 5 6 contains sufficient alkalinity to neutralize its acid content. I n TIWE'OF CCNTACT (HOURS) the much more alkaline sample (Yo. 5) the neutralizing sheath Figure 1. Rates of pH Change of Dilute Acetic Acid would be only 0.3 mm. thick. The actual rates of neutralization In p r e s e n c e of 3 % s o l u t i o n s of basic or n e u t r a l b a r i u m DNNS under in oils containing 3% of various soaps were followed by adding c o n d i t i o n s of s t a t i c w a t e r - d r o p t e s t at 25' C.. 1005 p e t r o l e u m oil Clark and Lubs indicators with overlapping pH ranges to separate used portions of 0,OlS.V acetic acid, from which test drops were formed as for the standard static drop test. The results TABLEVI. EFFECT OF BASICITY O F BARIUM DINONYLNAPHTHALENE SULFONATE ON for acetic acid and for distilled water INHIBITION O F RUSTIXG BY DILUTE ACIDSOLUTIONS I N STATIC WATER-DROP TEST are presented graphically in Figure 1. (Additive in grade 2135 petroleum oil was run in triplicate a t 25' C.) The data points are plotted as vertical InhibB%(OH)DNNS Indicated Corrosion Rating Exposure bars corresponding to 0.5 pH unit in 1 8 16 24 28 72 in Soap, Inhibitor, itor Test Composition of hr. hr. hr. hr. hr. Wt. Yo hr. No. Used" Water Drop Mole % recognition of the difficulty of inter0.0 10 .. None 118 0.036h'acetic acid None preting indicator colors in small drops 0.0 3.0 0 5 io :: 119 0.036N acetic acid 1 '/2 0 0 17.4 3.0 120 0.036N acetic acid 2 '/2 5 10 . . lying against a metal background and 0 3.0 0 1 2 0 121 5 45.2 0 . 0 3 6 N acetic acid 3 covered with an amber-colored oil. In 0 0 3.0 122 0 0 0 0 73.4 0,036iV acetic acid 4 3 . 0 0 0 0 0 0 8 9 . 2 0.036N acetic acid 5 123 0 this figure curves I, 11, and I11 show 124 0.036Nacetic acid 6 57.46 3.0 0 0 1 6 10 . . approximately the relations expected 1 5 10 15 20 between the most and least basic and d a y days days days days 125 0.036Nacetic acid 2 17.4 3 . 0 % in the carbonated soap, r e s p e c t i vely . 120 g. Curve V shows the much slower rate oil 0 0 0 0 0 126 0.036N acetic acid 2 1 7 . 4 1 8 . 0 % in of pH increase when three times a8 2 0 g . oil 0 0 0 0 0 much acetic acid is present in the drop 127 0.054N acetic acid 4 73.4 3.0 0 0 0 0 0 128 0 . 0 5 4 N acetic acid 5 89.2 3.0 0 0 0 0 0 (0.054X). For comparison, the almost 129 O . O i 2 N acetic acid 4 73.4 3.0 1/2 8c instantaneous jump in pH in a drop of 130 0.072Nacetic acid 5 89.2 3.0 1/8 5C distilled water exposed to similar oil 0.0 10 . . . . . . . . 131 0.012;v"CI None None sulfonate samples is shown by the dotted curves, A , B, and C, while line V I represents the complete stability of pH in 0.018N acetic acid exposed to the 137 0.012N HCl 6 57.4b 3.0 0 3 8 10 base oil containing no sulfonate. a For compositions see Table 111. The most surprising curve of this b See 5 Table 111. c Reachon, liberation of gas bubbles. series, however, is curve IV for the change in pH of 0.018N acetic acid in E
INDUSTRIAL AND ENGINEERING CHEMISTRY
1040
Vol. 46, NO. S
the order of 0.05N acetic acid, and indicates that the acid was preferentially concentrated in the aqueous phase. The water in TABLEYII. RUST-IhHIBITING PROPERTIES O F BASICB-ARIr\.i DI\O~YLNAPTHTHALESE SULFONATES A A D NEUTRAL BARILW contact with the 3% soap dispersion, on the other hand, showed a DINONYL~APHTHALELE SVLFOKATES ~h GRADE 2135 PETROpH of 4.4, which is substantially less acid t'han the 3.7 shown by LEUM OIL 0.018N acetic acid in water. Even a t this relat'ively high total (Static n a t e r drop test a t 25' C usings>nthetic sea-nater, tests i u n in acid concentration the acid level in the water phase rises t,o only triplicate) about one fifth that to be expected from equiparthion of acid bcCorrosion Rating a f t e r B a r O H > D S S S Indicated Sxposure tween the phases, and to less than one tenth that actually resulting 96 168 Inhibitor, 24 48 In Soap, Test Inhibitor m-hen water is equilibrated with 0.018N acid in sulfonate-free oil. hr. hr. hr. 1ir. W t . 4", Useda Mole % So. When two acid-bearing oil samples similar to those just dis138 Blank Kone 0.0 10 ... . cussed were used in static water-drop tests (with distilled water), 3.0 0 1 2 3 139 1 0.0 17.4 3.0 0 I/* 1 2 140 2 the differences were again pronounced. Rusting began under the 45.2 141 3 3.0 0 '/a 112 1 3.0 0 0 0 0 142 4 73.4 sulfonate-free oil within 10 minutes and spread rapidly under the 3.0 0 0 0 0 143 89.2 oil layer in all directions from the drop. The oil containing 3y0 144 8 57.4b 3.0 0 0 '/z 1 of neutral barium dinonylnapht'halene sulfonate and 0.0181V acea For composition see Table I11 tic acid, on the other hand, showed no signs of rusting aft,er 24 b See a , Table 111. hours. When 0.012N hydrochloric acid \?-as substituted for acetic TABLET'III. RVST-IKHIBITISG PROPERTIES OF BASICBARIUM DISOKYLNAPHTHALENE SULFONATESASD NEUTRALBARIUM acid in the experiments with neutral sulfonates described above, t,hc results obtained were qualitatively similar; hydrochloric acid DIKOSYLNAPTHALEKE SULFONATES IS GRADE2135 PETROLEVM \vas definitely removed from the aqueous phase by solubilization OIL in the soap micelles. and yater made only an incomplet,e extraction (3.0% by weight of inhibitor used. Acetic acid vapor test method a t 26' C , tests run in triplicate) of hydrochloric acid from the solubilized state in an oil-soap sysCorrosion Rating a f t e r tem. When a sulfonate-containing oil 0.012AVwith hydrochloric B a ( 0 H ) D S K S .icetic Acid Exposure acid was equilibrated with one tenth its volume of distilled water, Teat Inhibitor in Soap, in Water, 2 24 48 '26 168 KO, Vseda l l o l e yo V-t. % hr. hr. h r . lir, h r . the p H of the latter fell t o 4 instead of the 2.1 expected from equi150 Blank oil S o inhibitor 0.5 1 10 .. .. . . partition. Equilibrat'ion was slower in all cases v i t h hydrochloric acid than with acetic acid (see Figure 2). It is believed that this 0n n n n n x slowness results because H30+C1- has less true solubility in oil than has acetic acid, and depends more on the extremely slow diffusion of thc soap micelles t,o thr oil-water interface for the es0 5 0 0 0 0 5 156 6 57.4b tablishment of equilibrium. The acetic acid, on the other hand, 1. o 5 10 .. .. . 157 Blank oil K O inhibitor may diffuse through the oil in molecular form,. going out to seek micelles instead of wailing for their slow diffusion to the oil-water interface. Given an acid of the strength of hydrochloric acid and neutral barium dinonylnaphthnlene sulfonate micelles near the 163 6 57.4b 1. o 0 6 8 1 0 interface, there are two processes by which the acidity of the a For compositions see Table I11 aqueous phase can be reduced. One is the straightforward solub See Table 111. bilization of hydrochloric acid in the neutral soap micelles, or solubilization followed by metathesis within t,he micelle. G,
low, or basic, form of methyl red mas dissolved in the oil. The characteristic red color of the acidified indicator became visible near the oil-.ivater interface within a few minutes, and spread eventually throughout the whole oil phase. This sequestration of a corrosive acid by soap micelles in oil constitutes an important and hitherto unnoted mechanism of rust inhibition by oil-soluble soaps j it eupplement,s the adsorption niechanisni studied for a a-ide variety of amphipathic molecules by Baker and Zisman ( 6 ) . I t offers an explanation for the fact that such soaps as calcium phenyl stearate provide better rust inhibition, a t a given concentration in oil, than the acids from which t,hey mere prepared, although the acids form close-packed monolayers on metal from very dilute solutions. The acids dissolve in oils in the dimeric or monomeric form and have little or no solubilizing and sequestering poxver for short-chain acids. If the micelle contains hydroxyl or bicarbonate ions, the acid \vi11 be permanently neutralized with the formation of less corrosive reaction products. If the micelle contains a carboxylate soap, strong acids such as hydrochloric acid will he converted to their nietal salts, with the formation of an organic acid of high inolecular weight having rust-inhibiting propert,irs. The ability of micelles to sequester acetic acid was evaluated in another way by preparing a 0.018A' solution of acetic acid in untreated grade 1005 petroleum oil and in a Pimilar oil containing 3% of neutral barium dinonylnaphthalene sulfonate and equilibrating each sample with one tenth it,s voluine of distilled water (see Table IX). The pH of the wat,cr in contact with the sulfonate-free oil fell t o 3 I which corresponde t o a concentration of
Ba(D_1'YS)2
+ HC1*
Ba(DKX3)Cl
+ HDXXS
This was demonstrated qualitatively by the appearance of a suhstantial chloride concent'ration in the oil phase. The second mechanism involve3 the reaction! Ba(DNNS)2
+ 2HCl+
BaC12 (in aqueous phase) 4SHDNNS (in oil)
The displaccmcnt of an acid as strong as dinonylnapht'halene
Initial Composition Oil Phase Acetic acid (O.OlS.\-) 1005 petroleum oil Neutral barium D N S S Acetic acid (0.018.?7j 1005 petroleum oil Neutral barium D N N 3 HC1 ( 0 012.1') I005 petroleuin oil 17 45% basic barium DNKS (san1plc 1 ) 1003 petroleuin oil 89.2% basic barium D S N S (sainple 5) 1005 petroleum oil
Wt. % 0.1 99 9 3.0 0 1 96.9 3 0 0 05 9 6 95
Final pTI of W a t e r 3 1
4 4 5.0
3 0
11.5
97.0 3.0
12.6
97.0
May 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
sulfonic acid by hydrochloric acid would ordinarily stop far short of completion, but in this case the acid produced is oil-soluble while the salt is water-soluble, so that the reaction is not readily reversed. The occurrence of this second reaction for reducing the acidity of the water layer was demonstrated by the appearance of significant amounts of barium ion in the aqueous phase.
1041
it carries a strong base reserve, may allow large drops or trapped accumulations of acid water to persist unneutralized for days or weeks in a stagnant system. The effects of drop size on the rate of neutralization, while predictable, were nevertheless striking enough to deserve mention. A standard 0.2-ml. drop of 0.0121V hydrochloric acid stood for 4 days in contact with a 3% solution of basic sulfonate (No. 2) in a heavy oil without being neutralized to a pH of 5 . When the test drop was shaken with a similar oil sample to form a fine emulsion, the indicator changed color to show a pH of 8 within 10 seconds. This suggests that in active equipment, where emulsification of water occurs, the neutralization of acid in the water phase will be practically instantaneous if an adequate base reserve is present. PERFORMANCE O F SULFONATES BY METHODS OTHER THAK STATIC WATER-DROP TEST
Figure 2. Rates of pH Change for 0.012N Hydrochloric Acid In contact with 3 70solutions of basic or neutral barium DNNS under conditions of static water-drop test at 2S0 C.. 1005 petroleum oil used
The conditions established for the static water-drop test are, of course, arbitrary ones chosen for test purposes. It is of interest to consider some of the variables that will affect rust inhibition in acid environments under service conditions, I t is apparent from a comparison of the curves of Figures 1 and 2 with the data presented in Tables V and VI that rust prevention in the presence of a corrosive acid depends primarily upon neutralization or sequestration of the acid from water drops before these drops have a chance to establish intimate contact with the metal surface. The rate of neutralization will depend upon a t least the following variables: 1. 2. 3. 4. 5. 6.
Initial concentration of acid in the aqueous phase Concentration of base reserve in the oil phase Total stoichiometric excess of base available Relative solubility of acid constituent in water and in oil Viscosity of the oil phase Size of water drops (ratio of surface to volume)
The effects of items 1 to 4 are so obvious as to require no discussion, but the experimental observations on the two remaining variables are worth reporting. When the viscosity of the oil phase is as much as five times that of the water phase, convection and diffusion in the latter were found to keep the bulk of the 0.2-ml. water drop very close to equilibrium with the oil-water interface, so that the factor controlling the rate of neutralization was the viscosity of the oil phase. This determined the rate of transport of base reserve material to the interface, and of micelle-solubilized acid away from it. When an oil having a viscosity of 35 cs. was substituted for the 5-cs. material used for most of the observations, it was found that, in the presence of 3% of basic barium dinonylnaphthalene sulfonate (No. 2) (17.4 mole % of basic soap) a standard drop of acetic acid was brought to a pH of 5.0 in 7.5 hours, instead of in the 1 hour required to reach the same pH in the 5-cs. system. A speedup in the rate of neutralization was obtained when the heavy oil was warmed from 77" t o 140" F.; in this case the effect of the viscosity reduction was supplemented by a slight increase in the diffusion rates of the reactants. It is important to realize that an oil with a viscosity of 100 cs. or more, even though
When this series of basic inhibitors mas tested in the NRL fog cabinet, no significant difference was observed between the protection afforded by the neutral and basic soaps. This result was to have been expected, because there was no acid in the test environment and the leaching action of the fog droplets would tend to level any differences attributable to the basicity of the inhibitors. When, however, test coupons prepared as for the fog cabinet test were exposed to high humidity (but not leaching action) in the presence of acetic acid vapor (Table VIII, tests 150 to 163), the protection was again found to parallel acid neutralizing capacity of the soaps. The degree of increased protection is not so great as in the static water-drop tests because the total alkaline reserve that can be held by the thin film left after drainage of the test coupons is so much less than that present in the 20-ml. oil sample of the static drop test. It may be expected that alkaline reserve oils will exhibit maximum effectiveness in those practical situations where bulk oil is present, or oil is being continuously circulated past the surface to be protected, and will be least effective when fully drained vertical surfaces are exposed t o acid vapor, or to condensate from an acid atmosphere. In the brass-steel couple galvanic corrosion test, the alkaline barium dinonylnaphthalene sulfonate inhibitors showed the same inertness as the neutral synthetic product. The alkaline reserve inhibitors were also found noncorrosive to the nonferrous metals included in the static corrosion tests. One limitation of alkaline reserve sulfonate inhibitors prepared by simple overneutralization with barium hydroxide became apparent when a study was made of the storage stability of oils inhibited with such materials. The neutral barium dinonylnaphthalene sulfonate was found to give solutions in either petroleum or diester oil that were stable for a t least 90 days in contact with an atmosphere having a relative humidity of 80%. In contrast was the behavior of barium petroleum sulfonate, which under the test conditions, gave a precipitate from petroleum oil within 30 days, and from a diester oil within 10 days. The barium dinonylnaphthalene sulfonate preparations carrying excess hydroxyl alkalinity were also found to give stable solutions in petroleum oil, but their solutions in bis(2-ethylhexyl) sebacate threw down substantial precipitates under the conditions specified. These precipitates are believed to result from the hydrolvsis of the diester by the hydroxyl content of the basic additives. This hydrolysis would lead to the production of compounds in which barium was associated with sebacic acid as the soap of either the half ester or the dibasic acid. As carboxylate soaps, either would be likely to precipitate a t high relative humidities; and the full barium sebacate would be oil-insoluble under all conditions, except to the extent that small amounts might be retained in the micelles formed by the barium dinonylnaphthalene sulfonate. This explanation of the storage instability of the straight hydroxy soaps in diester oils is supported by the results obtained when such a soap was treated with moist carbon dioxide (8). It is assumed that this treatment replaces the free hydroxyl content
INDUSTRIAL AND ENGINEERING CHEMISTRY
1042
with bicarbonate (or possibly carbonate) radicals. The resulting product was fully oil-soluble and, as is shown in Tables V to VIII, it retains substantial acid neutralizing power, although it is possibly less vigorous in its reaction than a hydroxy soap of equivalent acid neutralizing capacity. The neutralizing action is assumed to be of the type Ba(DNNS)HCO$
+ HCL
Ba(DSNS)Cl
4- HzO
+ CO,
The bicarbonate half soap has the great advantage of complete Etorage stability in diester as well as in petroleum oils. Under crankcase conditions the hydroxyl-containing soaps would be expected to revert rapidly to the carbonated form. It is reasmring to ncte that such carbonated inhibitors will retain substantial acid-getting properties, particularly for traces of strong acids such as hydrochloric or hydrobromic. ACKNOWLEDGMENT
The authors acknowledge with pleasure the cooperation of King Organic Chemicals, Inc., Nor--alk, Conn., in making available a supply of purified dinonylnaphthalenesulfonic acid, and in preparing certain research samples of the sodium and barium soaps of this acid in conformity v i t h the suggestions of this laboratory. Lyophilized preparations of sodium and barium dinonylnaphthalene sulfonates mere prepared by John G. Honig of this laboratory, whom the authors wish to thank. LITERATURE CITED
(1) Archibald, hI. A,, in “Science of Petroleum,” Vol. IV, p. 2840, London, Oxford University Press, 1938. (2) Aseeff, P. A , Mastin. T. If7., and Rhodes, A., U. 8. Patents 2,616,904,2,616,905,2,616.906 (1952).
Vol. 46,No. 5
(3) Baker, H. R., “Corrosion of Brass-Retainer Ball Bearings,” Naval Research Laboratory, NRL Rept. 3918 (December 1951). (4) Baker, H. R., “Synthetic Oil-Soluble Sulfonate Rust Inhibitor,” Naval Research Laboratory, NRL Letter R e p t . 3270-308,Sl (Aun. 7. 1951). (5) Baker7H. R., Jhnes, D. T., and Zisman, W. A , , IKD.ENG.CHEM. 41,137 (1949). (6) Baker, H. R., and Zisman, W. A., Ibzd., 40 2338 (1948). (7) Baker, H. R., and Zisman, W. $., Lubrzeation Eng., 7, 117 (1951). (8) David, 1%’. W., J . Inst. Petroleum,35, 563 (1949). (9) Eckert, G . W., U. S. Patent’2,610,946(1952). (10) Edgar, J. A., Plantfeber, J. M.,and Bergstrom, R. F., S B E Quart.Trans., 3,381 (1949). (11) Federal Specification VV-L-791, Method 531.1. (12) Ibid., Method 532.1. (13) Honig, J. G., and Singleterry, C. R., “Physical-Chemical Properties of Oil-Soluble Soaps. I. Sodium Phenylstearate in Benzene,” accepted for publication in J . Phgls. Chem. (14) Kaufman, S., and Singleterry, C. R., “Micelle Formation by Sulfonates in Non-polar Solvents,” Naval Research Laboratory Report, to be published. (15) Mertes, R. W., U. S. Patent 2,501,731 (1947). (16) RIurphy, C. XI., Saunders, C.E., and Smith, D. C., IND.ENG. CHEM.,42,2462 (1950). (17) Pilot, S. v., Sereda, J., and Saankowski, W., Petroleum Z., 29, l(1933). (18) Pritsker, G. G., A-atZ. Petroleum A’ews, 37, R-793 (1945). (19) Sperling, R., IND.ERG.CHEM.,40, 890 (1948). (20) Van Ess, R. P., and Sipple, H. E., U. 9. Patent 2,585,520 (1952). (21) Williams, C. G., Inetitute of Automobile Engineers, “Collected Researches on Cylinder Wear,” 1940. (22) Zuidema, H. H., “Performance of Lubricating Oils,” ACS Monograph 113, pp. 144-53, Kew Yoyk, Reinhold Publishing Corp., 1952. RECEIVED for review September 8, 1953.
BCCEPTED February 2, 1954.
Cation Exchange Materials from Cotton and Polyvinyl Phosphate GEORGE C. DAULI, J. DAVID REID, AND ROBERT RI. REINIPARDT Southern Regional Research Laboratory, New Orleans, Las
T
HE production of ion exchange fabrics by chemical modifica-
tion of cotton cellulose has been reported by several B-orkers ( 9 , 7 , 11, 16, I“), and the ion exchange characteristics of these fabrics have been studied a t this laboratory by Hoffpauir and Guthrie (9). An ion exchanger in the form of fabric is convenient €or laboratory use; no special apparatus is necessary, a piece of cloth being merely stirred with the liquid for a time and removed. Phosphorylated cotton is more promising than other ion exchange fabrics with respect to its cation exchange capacity and p H range (11). This modified cotton v a s used by Hoffpauir and Guthrie (8) as a cation exchanger in the laboratory preparation of highly purified oilseed proteins. Coppick ( 2 ) phosphorylated cotton cloth by padding with an aqueous solution of phosphoric acid containing urea, then drying and curing a t around 140” C. The product has been characterized as a dibasic acid phosphate of cellulose (17 ) . Korever, phosphorylation of cotton cellulose hss been limited t o about one acid group per three anhydroglucose units because of the attendant excessive degradation of the cloth. As the phosphorylation reaction causes the degradation, a previously highly phosphorylated material might be used to react with cotton t o give a product with equivalent cation exchange capacity and reduced degradation. I n the present work it was postulated that excessive degrada1
Present address, Courtaulds (Alabama), Ioc., Mobile, Ala.
tion and strength loss might be overcome by first phosphorylating a polyhydric alcohol and then making this product react with cotton to give a cation exchanger of higher capacity. PREPARATION OF POLYVINYL PHOSPHATES
Polyvinyl alcohol was selected ae being a representative poiyhydric alcohol which also possessed the capacity of further condensation by cross-linking m ith itself. This reaction is catalyzed by phosphoric acid and heat (IO) and yields a product which is insoluble in water. Since this work started, Ferrel, Olcott, and Fraenkel-Conrat (6)have reported the phosphorylation of polyvinyl alcohol in 3 days at room temperature with phosphorus pentoxide and phoephoric acid. The product contained 20% phosphorus; of this orthophosphate residues were attached to about one fourth of the vinyl units, metaphosphates to about one third, and no phoephorup was contained in the remainder. Using the same method, Katohalfiky and Eisenberg (12) have phosphorylated polyvinyl alcohol fibers. Kosolapoff ( I S ) has patented a method of preparing polyvinyl arylphosphates by reaction of polyvinyl alcohol with an arylphosphoryl halide such as diphenylphosphoryl chloride or phenylphosphoryi dichloride. Several known methods of phosphorylating alcohols were adapted to the phosphorylation of polyvinyl alcohol to obtain
