US2406823A - Bituminous emulsions - Google Patents

Description

Patented Sept. 3, 1946 rssr BITUMINOUS EMULSIONS Joseph E. Fratis,-Berkeley, and Eugene H. Oakley, assignors to American Bitumuls Company, San Francisco, Calif., a

El Cerrito, Califi,

corporation of Delaware 6 Claims.

The present invention pertains to aqueous bituminous emulsions and more particularly to emulsions of the fluid, quick-breaking penetration type.

It has previously been disclosed by Montgomerie, United States Patent No. 1,643,675, and by Eraun, United States Patent No. 1,73'7/i9l, that asphaltic residues derived from certain petroleum crude oils, such for instance as those from Mexico, contain. a proportion of saponifiable material which when the molten asphalt is dispersed hot dilute aqueous caustic alkali solution reacts with the caustic to form an emulsifier in situ that is effective to produce an emulsion of unique and highly desirable characteristics. Such emulsions, which are generally referred to as quick-breaking or penetrating emulsions are now widely used in the construction and repair of roads and in various other important industrial operations. They are perfectly stable for long periods in storage but have a high and substantially instantaneous demulsibility when contacted with rock aggregates or other mineral or solid surfaces. They usually contain from 50 to 60% of dispersed. bitumen and yet they are surprisingly fluid, having at ordinary temperatures a fluidity comparable to that of a light lubricating oil.

It is, however, now widely recognized that not all petroleum asphalts as regularly produced will emulsify by the simpl method of dispersion in hot dilute alkaline solutions. This has usually men assumed to be due to a deficiency of acids or, more broadly, saponifiable ingredients in the asphalt. We have found that while this is probably the correct explanation in some cases it is not generally applicable since ther are many asp-halts having a relatively high content of free natural acids or saponifiable material which are nevertheless not emulsifdable by the Montgomerie method. On further studying these asphalts we have discovered that in order to produce a quick breaking emulsion of the lliontgomeri type it is not only necessary that the asphalt contain a certain minimum quantity of acids but also that the acids shall bear a certain molecular relation to the asphalt. On the basis of this discovery we have found it possible, as will be hereinafter fully explained, to so adjust and regulate the quantity and nature of the saponifiable petroleum ingredients in an asphalt that substantially all of those which do not, as ordinarily produced, emulsify or which form only poor emulsions by the Montgomerie method may be made to give quickbreaking emulsions that are entirely satisfactory for the usual commercial uses.

It is the broad object of this invention to so adjust the acid content of a petroleum asphalt that it will readily emulsify when dispersed in molten condition in a hot dilute aqueous solution of caustic alkali and will thereby produce a quickbreaking emulsion of the oil-in-water type that is stable in storage, of high bitumen content, high fluidity and high demulsibility on contact with mineral or other solid surfaces.

It is a more specific object of our invention to adjust the saponifiable ingredients of a petroleum asphalt both as to quantity and character for optimum emulsification when th asphalt is dispersed in a hot dilute alkaline solution.

It is a specific object of our invention to add to a petroleum asphalt organic acids, derived from petroleum, in quantity and character to cooperate with the acids naturally occurring in the asphalt in producing an emulsion of the quickbreaking type.

Another object of our invention is to make available for the production of quick-breaking emulsions large quantities of asphalts which have hitherto been unsuited for such use.

Other objects of our invention will be obvious from the description and discussion which follows.

The presence of organic acids in petroleum distillates and of both free acids and saponifiable substances such as acid anhydrides and possibly lactones in petroleum residue has long been known. The lower molecular weight acids occurring in the readily distillable fractions of crude petroleum are usually referred to as naphthenic acids While the acids of high molecularweight that are retained in the residual portion of the oil have been referred to by various writers as asphaltous or asphaltic acids. Very little, however, is actually known concerning these heavier acids and While there are some who believe that they differ only in degree from th naphthenic acids, the majority opinion appears to be that they dilier in kind as Well. Assuming that there is a difference in molecular structure between the acids of low and of high molecular weight, naturally occurring in petroleum as it comes from the earth, the transition is probably through several stages for molecular series resulting in a range of overlapping types which would preclude the possibility of any simple method of separation or any definite point of division for classification. From a pratical standpoint it is thus expedient'to identify the natural petroleum acids With respect to their average molecular or equivalent weight and in the present connection that practice will be adhered to except insofar as it may occasionally be convenient to refer more broadly to the acids below a somewhat arbitrarily chosen average equiv. ntweight of about 400 erably, also, they should. have a. molecular structure that is in general similar to the asphalt. In other words, salts of the acids occurring in or derived from a California Midway crude are more as naphthenic and these above as fasphaltic? 5 efiective in emplsifying a Midway asphalt It is generally understood that in the preparathan are the same salts of acids from a totally diftion of an emulsion by the Montgomerie method ferent crude such as that from Michigan or Pennthe alkali metal salts of the acids occurring natsylvania. For petroleum asphalts in general we urally in the asphalt are formed when the molten have found that acids having an average equivasphalt is dispersed in the hot aqueous alkaline soalent weight between about 500 and 900 are usulution and that these salts, produced as they are at aliy most effective in the production of stable, the interface between the asphalt particles and the fluid, quick-breaking emulsions by the Montwater continuous phase, serve as the emulsifiers gomerie method and further that such acids must which convert the dispersion into a true emule present to the extent of at least 1.00 to 1.50% sion. In attempting to determine wh asphalts by weightof the asphalt but should of course not that have a, relatively high content of natural 'be present insuch large quantity as to result in acids or saponifiable ingredients are, as above an emulsion of low demulsibility and/or high setpointed out, nevertheless not satisfactorily emultlement. sifiable by this method, we have found that the An investigation of aspl'ialts from widely difalkali metal salts of th natural petroleum acids ferent sources has revealed a wide variation not of low molecular weight are quite soluble in water only in the quantity but also in the character 01" and relatively insoluble in oil and that as the 1110- the acids naturally present or available on saponilecular weight of the acid increases this preferfication. The quantity may be from a few tenths ential solubility shifts from the water side to the of 1% to as much as 5% or more of the asphalt oil side so that the salts of acids in the asphaltic and the average equivalent weight from about 200 group are substantially insoluble in water and apto well over 2,000. Pertinent analyses'on a mum-- preciably soluble in oil. We then found that in her of commercial asphalts from different localiorder to produce a. satisfactory quick 'breaking ties are recorded in Table I.

Table I Aver Pene- Melting Sapomfi- Per-cent Emulsifiable Source of asphalt samople tration at point cation total f g gg Montgomerie 77F. BdzRF. number acids acids method California (Midway) 1024 124 108 1.4.0 2. 334 785 Yes. Do 1023 317 93.5 1.45 2. 528 590 Yes. D0 2214 2200 101.5 1.56 2.742 600 Yes. Mexico 2216 168 105.5 1.30 1. 298 535 Yes. Wyoming. 2166 185 104. 5 0.44 1. 236 1708 Oklahoma 2217 173 107 0. 40 0. 553 510 Arkansas 2219 230 101. 5 0. 54 1. 520 475 Mid-OontinenL. 2215 225 105 0. 56 0. 638 524 Texas 2218 09' 115.5 0. 42 0.556 533 Montana 2325 142 107 0.36 0. 925 1250 Bermudez Lake 2326 164 106.5 6.20 2. 377 585 Yes. Cal1fornia(Kern) 2149 108 102 2.49 3. 338 672 Yes. California (Mt. Vie 2027 182 113 0. 41 1.744 1586. California ('Gasmalia) 1928 126 111 2.75 3.155 708 Yes. Mexico 2.33s 77 124 1.02 1.077 637 Yes. D 2237 70 124.5 0. 1.062 878 Yes.

2340 0.70 0. 844 1413 Almost. '2171 23s 95. 5 0. 44 2. 320 1560 Mexico 2357 157 110 1.15 1.062 800 Yes emulsion the acids present or liberated in an as- It will be observed that all of the asphalts, rephalt on saponification must form alkali salts 55 corded in the above Table I, that contain acids of that have the proper solubility relation in water an average equivalent weight between 500 and 900 and oil. If these salts are too water soluble they in an amount above about 1% were found to be are withdrawn completely into the aqueous phase emulsifiable by the Montgomerie method. The and such emulsionas may be formed will tend to asphalts recorded which were not emulsiiiable have the characteristics of a conventional soap by this method deviate in one or more of three type emulsion, in which a common fatty acid ways from these limits as follows: soap such .as sodium oleate is employed as the Samples Nos. 2027, 2166 and 2171 contain more emulsifier, rather than the high fluidity and than the minimum 1% of acids but they are subquick-breaking characteristics necessary in a stantially above the optimum average equivalent penetrating emulsion. On-the other hand, if they Weight; sample No. 2219 contains more than 1% are too insolublein water they tend to be held in of acids but they are below the optimum average the oil phase and are not drawn into the interface equivalent weight; samples Nos. 2215, 2217 and to an extent or in a manner to effect emulsifica- 2218 contain acids of the optimum average equivtion. alent weight but in amount less than 1%; and While it is b no means easy to say spec fically sample No. 2325 contains less than 1% of acids what the character of the acids must be in order having an average equivalent weight above the that their alkali salts will have the propersoluoptimum range. We have found that when the bility relations to function as efiective in situ average equivalent weight of the acids in samples emulsifiers, it has been found that in general they Nos. 2027, .2166, 2171 and 2325 is adjusted downshould be of about the same average molecular ward by the addition of acids of substantially weight as the asphalt the are to emulsify. Preflower equivalent weight than those naturally occurring, as for instance through the addition of acids having an average equivalent weight from about 400 to 700, the asphalts are rendered readily emulsifiable. Likewise, when the acid content of samples Nos. 2215, 2217 and 2218 is brought above the minimum 1% by the addition of acids having an average equivalent weight within the optimum range from 500 to 900 and when the average equivalent weight of the acids in sample No. 2219 is raised by the addition of similar acids, all of these samples are easily emulsified when dispersed in hot alkali solution.

While, as hereinabove indicated, the average equivalent weight of the naturally occurring acids in a petroleum asphalt for its optimum emulsification lies between about 500 and 900, we have found that it is not always necessary when adjusting a very high average equivalent weight downward through the addition of substantially lighter acids to come within this range since a reduction to about 1200 or below is frequently adequate to give an asphalt of satisfactory emulsifying characteristics.

It would thus appear that the optimum average weight of asphaltic acids for the production of a satisfactory emulsions by the Montgomerie method depends somewhat upon the distance apart of the extremes comprehended by the average. When that distance is relatively great, as for instance from 400 to 1800 or above, satisfactory emulsions are produced when the weighted average equivalent weight is reduced to only about 1200, whereas when the acids cover a narrower range a weighted average between about 500 and 900 will usually be more desirable.

The foregoing principles may be further illustrated by the following examples:

Example No. 1

Wyoming asphalt, sample No. 2166, which will be seen by reference to Table I to contain 1.236% of acids of 1708 average equivalent weight, was found not to give an emulsion when dispersed in hot aqueous 0.05% normal sodium hydroxide solution. When 0.28% of acids from a California Midway crude having an average equivalent weight of 666 was added, giving a product con taining 1.516% of acids having a weighted average equivalent weight of 1510, more tendency toward emulsification was shown but still no satisfactory emulsion could be produced. When, however, 1.27% of these same acids was added to the asphalt, giving a product containing 2.506% of acids having a weighted average equivalent weight of 1177, a stable fluid emulsion of high demulsibility was produced on dispersion in dilute caustic solution. When a still greater amount. 5.3%, of the same acids was added to the same asphalt, giving a product containing 6.536% of total acids having a weighted average aquivalent weight of 863, its emulsibility was still further enhanced but the emulsion formed showed excessive settlement on standing and a low demulsibility.

Example No. 2

To California asphalt sample No. 2027, which contained 1.744% of acids having an average equivalent weight of 1586 and which was not emulsible by the Montgomerie method, was added 0.1% of acids from Midway crude having an average equivalent weight of 357. The total acids in the asphalt then amounted to 1.844% having an average equivalent weight of 1535. While the product showed some tendency to emulsify, it

6 still would not produce a satisfactory emulsion. When, however, 1.0% of the same acids was added, giving a product having 2.744% of acids of average equivalent weight 1140, an entirely satisfactory emulsion could be produced.

Example No. 3

2.0% by weight of acids from California crude having an average equivalent weight between 406 and 460 when added to Texas asphalt sample 2218 gave a product of good emulsibility. When, however, acids having an average equivalent weight of 273 were added to this same asphalt in quantities from 1.0% to 10.0%, no satisfactory emulsion could be produced.

For determining the acid content of an asphalt we have found the following simple method entirely satisfactory: 30 grams of asphalt are dissolved in 60 cc. of a light petroleum thinner. known in the trade as IO-P thinner, 300 cc. of 95% ethyl alcohol and 5 cc. of Water containing 2.4 grams of pure sodium hydroxide are added. and the mixture then boiled under a reflux condenser for one hour, after which water sufficient to reduce the alcohol concentration to is added through the condenser, the mixture cooled and transferred to a separatory funnel wherein it is allowed to stand in a warm place over night. The two layers are separated and the asphaltpetroleum thinner layer washed with 80 cc. of alcohol. The main alcoholic extract is washed with three successive cc. portions .of petroleum ether, the petroleum ether washes are combined in a separatory funnel, the 80 cc. portion of alcohol previously used to wash the asphalt layer is added thereto together with. 20 cc. of water and the mixture vigorously shaken. On separation the alcoholic layer is united with the main body of alcoholic extract. The petroleum acids may then be separated from this extract by acidifying with hydrochloric acid and dilution with water, their quantity determined by Weighing and their average equivalent weight determined by titration or they may be separated roughly into groups by successively extracting the alcoholic solution with appropriate solvents of progressively varying solvent power.

Acids which may be used for adjusting the acid content of asphalts in accordance with the principles of our invention, as hereinabove set forth. may be derived from petroleum in a number of ways. One readily available source of such acids is from the still bottoms produced when a heavy lubricating oil fraction is distilled over caustic soda for the reduction of organic acidity. Such still bottoms contain the sodium salts of the petroleum acids which may be liberated by acidification with a mineral acid, collected and redistilled if necessary to segregate the acids of higher equivalent weight useful in the practice of our invention.

Another source of almost unlimited quantities of natural petroleum acids for use in adjusting the acid content of asphalts is through the simple caustic alkali or alcoholic caustic alkali extraction of petroleum residua, road oils, fuel oils and asphalts which are not intended for emulsification. The acids are. of course, liberated by acidification and collected in any appropriate manner.

Satisfactory acids for our purpose may also be derived from various heavy petroleum fractions that have been subjected to very mild oxidation such that the acids produced are largely simple carboxylic acids rather than the acids of hig er oxygen content which are usually referred to as sauce,

7 OXy-flCidS. For instance, it has been found that the acids which may be recovered from a sample of heavy lubricating after use in regular service in an automobile en. tirely satisfacof an asphalt tory for adjusting the CClItc; as hereinabove described. The carbcxylic acids produced by air blowing a heavy cylinder stock at about to 400 F. for several hours have also found effective in this connection.

While the adjust. .ent of the acid content f asphalt as contemplated by our invention w .i usually be by the addition of petroleum. acids from an external source, it is ccnceiva'ble'that it might under certain circumstances be mor desirable to arrive at the desired adjustment by extracting either the very heavy or the very light acids or by the extraction of all the acids with the subsent return of the portions thereof. Any such operation will be readily seen to be consist t with the principle hereinabove set forth. 3 another method of arriving at our ultimate result may be possible with an asphalt which found to be unsatisiactorily emulsible, due to an ass of low equivalent weight acids, since we have found that on moderate heating for considerable periods or" time the acidic constituents of an asphalt are quite readily polymerized without, however, having their acidic nature appre" ciably altered. This fact is illustrated by a comparison of samples Nos. 1024 and 2171 of Table I. Sample No. 2171 was prepared by moderately hea ng an asphalt which was originally comparable to that of sample No. 102%. It will be noted that while the total acid content remained substantially the same, the average equivalent weight of the acids was increased from about 8% to 1569, and while specific instance the asphalt was rcnc l the i crease in equivalent weight, a similar doubling of the equivalent weight of acids in the range or" 360 or below would throw them into the range of 500 to etc which has been found to give desirable emulsi- Iication.

Throughout the foregoing discussion we have referred to the caustic solutions suitable for producing quick-breaking emulsions of the Ivi'ontgomcrie type only as dilute aqueous solutions. it will he understood that the several caustic alkalies are substantial equivalents in this use. The concentration may vary somewhat depending on the u icular asphalt to be emulsified and the s ec conditions under which emulsification is to be eff cted but will usually be within the c u 0.05 and 0.19 normal.

the foregoing discussion and in the as the acid content of an asphalt is refer ed to without further characterization, it will he understood to mean the total available acid whether in the form of free acid or whether a combination from which it may be liberated on contact with hot caustic solution.

This application is a continuation of application Serial No. 262,566, filed March 17, 1939.

Having now fully described our invention which consists in adjusting the acid content or an for optimum emulsification, to give a stable, n

i'lC alkali solu soda it so emulsifile, which comprises adjusting the petroleum acid content of the asphalt not so emulsifiable,

without otherwise substantially changing the composition of the asphalt, so as to produce an asphalt having at least about 1% and not more than about 3% by weight, based on the asphalt, of petroleum acids having an molecular weight of about 550 to 1200, said petroleum acid content being adjusted to an amount sufficient only to produce an asphalt which is emulsifiable in hot, dilute aqueous caustic soda solution to form an emulsion which breaks quickly on contact with aggregate.

2'. In a process wherein asphalt which is not eniulsinable in hot, dilute aqueous caustic soda solution is rendered emulsifiable in hot, dilute aqueous caustic soda solution by incorporating in the asphalt a saponifiable material, the improvement which comprises adding to the asphalt cu c-ient substantially unadulterated petroleum acids to cause the asphalt to contain at least about 1% and not more than about 3% by weight, on the asphalt, of petroleum acids having an average molecular weight of about 560 to 1208,

t to produce an asphalt having about 1% to 3% by weight based on th asphalt of acids having an average molecular weight between about too and 280, the amount of petroleum acids so removed being sufficient only to produce an asphalt which is emulsifiable in hot, dilute aqueous caustic soda! solution to produce an emulsion which breaks quickly on contact with aggregate.

4. A method of producing an asphalt which is emulsifiable in hot, dilute aqueous caustic soda solution from an asphalt which is not so emulsiiiablc and which has a petroleum acid content above 1% by weight based on the asphalt and or average molecular weight below see, which comprise subjecting he to heat treatment sufficient to produce an asphalt having about 1% to 3% by weight based on the asphalt of petroleum acids having an average molecular weight of about 5% to 1268, said heat treatment being su icient only to produce an asphalt which is emulsifiable in hot, dilute aqueous caustic soda solution to produce an emulsion which breaks quickly on contact with aggregate.

5. lhe method of claim 1, which the petroieum acid content of the asphalt is adjusted so as to produce an asphalt having at least about 1% and not more than about 3% by weight, based on the asphalt, of petroleum acids having an average molecular weight of about too to 9%.

6. The improvement of claim 2, in which there is added to the asphalt sufiicient substantially unadulterated petroleum acids to cause the asphalt to contain at least about 1% and not more than about 3% by weight, based on the asphalt, of petroleum acids caving an average molecular weight of about 590 to 900.

JOSEPH E. FRATIS. EUGENE I-I. OAKLEY.