US1948881A - Bituminous emulsion - Google Patents

Description

Patented Feb. 27, 134

BIT Kl Lester Kirschbraun, Leonie, N. 3., asslgnor, by mesne assignments, to The Patent and Licensing Corporation, New York, N. Y.,

Massachusetts a corporation of No Drawing. Application May 26, 1928 a Serial No. 280,964

6 Claims.

This invention relates to bituminous compositions and more particularly to watery emulsions of asphalt and similar or analogous bitumens in which the water constitutes the external phase.

Aqueous emulsions or dispersions of various materials of a bituminous nature are well known, the production thereof being achieved by numerous methods more or less distinct, and with 10 the aid of various types of emulsifying agents.

Depending upon the emulsifying media employed, I

the process by which the emulsifioation is carried on, and certain other factors, the resultant emulsion products possess certain properties in common, and other properties which are quite marked and sufficiently distinctive to enable one skilled in the art to readily distinguish the one type from the other.

Among the latter properties which may to a certain extentbe resorted to as a guide in classlfying these emulsion products, is the stability of the emulsion under certain definite influences. Thus, certain emulsions begin to set or break, that is, the dispersed particles begin to coalesce with one another, very shortly after the emulsion is exposed to the air, the coalescence of the particles proceeding even in the presence of a considerable proportion of the water content of the emulsion. In other words, in this general class of emulsion, dehydration follows coalescence. The coalescence or breaking of the emulsion under these conditions proceeds of course from those portions thereof that are in more active contact with air, or exposed thereto. Thus, when an emulsion of this type is spread as a layer of considerable thickness, the foregoing action results in the formation of a skin or scum on the ex- -posed surface of the layer and a more or less sealing in by this scum or skin of the portions of the layer not in direct contact with air. Accordingly, while certain portions of a layer of emulsion of this type may be readily broken, yet other portions thereof remain unbroken. Apparently there is a more or less segregation of the phases, with expulsion of water by the breaking action.

Emulsions of this class that are thus readily susceptible to being broken on exposure to air, are in general, relatively unstable and when subjected to certain influences, as for example when spread with a brush, or by the action of electrolytes, or when mixed with'finely divided powders or with mineral aggregate, they break down immediately.

To the foregoing general type, belong emulsaponify the fatty acid sions that are produced by the aid of emulsifying agents such as soaps and sulphonated oils. In producing such soap emulsion, the bituminous material, of whatever character it may be, may be mixed with asuitable quantity of the soap so in a water suspension. If desired, the soap may be formed in situ' during the process, by first mixing the bitumen with a saponifiable material, preferably a higher fatty acid of the saturated series, such as oleic acid, and thereafter adding to the mixture sufficient quantities of alkali to f and form therewith the requisite amount of soap to emulsify the bitumen. This latter procedure is particular advantageous for the 'emulsification of theharder varieties of o bitumen inasmuch as the saponiflable substance may be selected so as to flux with the base and reduce the hardness of the latter in order to facilitate the 'emulsification thereof.

'Still another class of emulsions that fall within the general group of relatively unstable emulsions, as already noted, are those made with substances such as sodium silicate as the emulsifying media.

Now, as opposed to this general type of relatively unstable emulsions, there stands another type, the members of which are relatively stable under influences which readily break emulsions of the first group, and as a matter of fact, certain emulsions belonging to this class are easily recognized by their extreme stability. In this class of emulsions, coalescence follows dehydration, the coalescence of emulsions of this type being dependent upon substantially complete removal of the water phase thereof, by evaporation, and such emulsions are not broken or coalesced to any extent upon mere contact with the air. The water phase evaporates uniformly from all portions of a layer of such emulsion, no skin or scum being formed on the surface 95 thereof as is generally the case with emulsions of the unstable type. Hence, these so-called stable emulsions are characterized by a delayed initial set but the setting when it does occur is uniform throughout the depth of the layers. Representative of this general type are emulsions produced with clay or other analogous finely divided or colloidal mineral powders.

Other emulsions that may be said to belong to this type are those that are made with gelatin as the emulsifying agent. Emulsions in which starch combined with say 2 to 10% by weight thereof of tannic acid or its equivalent in tannin such use, from this standpoint.

hand, if any attempt is made to substitute under ally possess a sufficient degree of stability to be also grouped in this class.

In the specification and claims the term "unstable emulsion is intended to have reference to emulsions of the first class above referred to, namely, those wherein dehydration follows coalescence, while the term "stable emulsion i's'intended to apply to the second class described, namely, those emulsions wherein coalescence follows dehydration.

In the commercial application of these bituminous compositions it is found that while the ability of the emulsions of the first class to set rapidly is advantageous for certain uses, still the general instability of such emulsions, in the presence of electrolytes, mineral aggregate, or the like, renders such emulsion objectionable for On the other such conditions-of use, an emulsion of the second general class above mentioned, it is found that while the diiliculties attendant upon the admixture of the emulsion with finely divided powders, mineral aggregate, electrolytes, etc. arelargely overcome, yet the necessity for substantially complete removal. of water from such emulsion before it will set, introduces the compensating disadvantage of delayed setting. Thus, for road building purposes, where large quantities of emulsion are used in accordance with well established practice, it is essential that the road ma terial be capable of bonding rapidly in damp or cold weather or whenever drying conditions are unfavorable. Soap emulsions, for example, furnish the requirement of rapid initial set, as already pointed out, but the relatively instability thereof, makes it exceedingly difficult to properly mix certain types of mineral aggregate with the soap emulsion, (and as a matter of fact, special precautions are generally-adapted in order to avoid, so far as possible, the breaking down of the emulsion while it is being mixed with any aggregate and before the latter is applied to the road foundation). On the other hand, emulsions of the type of which clay emulsions are representative,'while sufficiently stable to permit admixture thereof with mineral aggregate, are objectionable for this use because of the delay incident to the initial setting thereof.

In accordance with my present invention, I arrive at optimum conditions by combining an emulsion of a generally stable character, with one which is relatively unstable, to produce a compound system of an intermediate degree of stability which may be more or less predetermined, depending upon the relative quantities of the separate emulsions thus combined.

The invention may be utilized for example, in connection with road work, in which case the proportions of the separate emulsions may be regulatedto such a point as will provide the system with the requisite degree of stability to enable the same to be mixed with the desired min-.

eral aggregate and yet sufficient instabilityv to result in a rapid initial set thereof, or at least such an acceleration of the setting time above that which would be required for the uncombined stable emulsion, as will aiford the proper bonding of the road metal under practically any weather conditions that may prevail at the time the roadis being built. Thus, with sufficiently rapid skimming over of the emulsion film, the road could withstand action of rain soon after construction.

As a specific illustration of one embodiment of my invention, 1 may combine an asphalt=clay emulsion with a soap emulsion of asphalt. The

asphalt forming the base of these separate emulusing soap or equivalent material as the emulsifying agent, the higher the melting point of the base being dispersed, the more difficult it is to effect dispersion, whereas, on the other hand, when clay or similar material is used in producing a stable-emulsion, the emulsification is more diflicult to carry out with bases of lowermelting point than with those of relatively high melting point, and the products with harder bitumen are the more stable. The asphalt-soap emulsion may be formed by any of the recognized methods of producing this type of emulsion. In general, the asphalt clay emulsion may be composed of -60% asphalt, 40% water,-and a small amount of clay. The soap emulsion will ordinarily contain about asphalt, 30% water, and a small amount of soap.

Depending upon the character of the clay emulsion the alkalinity of the soap emulsion, and other factors, more or less treatment of one of the emulsions may be necessary inorder to facilitate the mixing of the two emulsions without causing the relatively unstable soap emulsion to break down during the mixing procedure. can best comprise an adjustment of the hydrogen ion concentration, preferably by adding in the specific example cited, alkali to the clay emulsion to bring it to a pH value approximating the pH value of the soap'emulsion. With the hydrogen ion concentrations of the separate emulsions thus adjusted to substantially equal values, the emulsions are rendered more compatible and may then be readily mixed with one another in substantially all proportions.

Thus, an emulsion having a hydrogen ion concentration on the acid side, as for example, a pH of 4.5 to 5.0, may be treated with about 2% by weight thereof of trisodium phosphate to thereby bring it to a pH value of say 8.0 to 8.5, at which point -it maybe readily mixed in all proportions with the soap emulsion, having a pH value of above 9.0.

It will be understood that the feature of adlusting the hydrogen ion concentration of the separate emulsions may be resorted to in other instances when mixing a stable emulsion with one relatively unstable, and is not confined necessarily to the procedure wherein a clay emulsion is mixed with a soap emulsion.

It will be understood, however, that in many instances the adjusting treatment may not be necessary at all, since certain emulsions without treatment may be entirely compatible to permit the mixing thereof. I

I have heretofore saidthat the separate emulsions, adjusted, if necessary, may be mixed in substantially all proportions. emulsion made with a mixture of several. different types of clays as the emulsifying media, and having a pH value of above 6.5, can be mixed in widely varying proportions with an emulsion of asphalt, soap and water.

This treatment Thus, an asphalt misses;

Where the separate emulsions are combined in about equal parts by weight, the stability of the soap emulsion is enhanced to the point that the compound emulsion may be mixed with electrolytes, finely divided mineral powders, etc., and may be spread with a brush without breaking down. The greater. the proportion of stable emulsion in the system, the more stable will the latter be, and conversely, with smaller proportions of the stable emulsion, the compound system iscorrespondingly less stable and more rapidly undergoes its initial or superficial setting.

That the soap emulsion functions to decrease the time required for the compound system to set can be readily recognized by the appearance of a skin or scum upon the surface of a layer of the mixed emulsion spread upon a plate and left in the open air. This skin or sc'um resembles closely the skin which forms on the exposed surface of a layer of soap emulsion. The time that elapses before this scum definitely appears is, roughly speaking, a measure of the stability of the system, and the greater the proportion of the unstable soap emulsion present in the system, the more rapidly does this scum form, thus indicating decreased stability of the system. Whereas, for example, approximately 24 hours are generally required for a relatively thick layer of clay emulsion to set, a layer of similar thickness of soap emulsion, which ordinarily begins to set and skin over within about ten minutes after exposure to air, when mixed with the clay emulsion in the proportion of about by weight of soap emulsion on the basis of the clay emulsion, induces an initial setting of the system within a half to three-quarters of an hour, as evidenced by the appearance of the aforesaid skin or scum on the exposed surface thereof. Conversely, of course, the clay emulsion increases the stability of the soap emulsion, the extent of such increase depending upon the. relative amount of clay emulsion present.

Similarly a stable emulsion of asphalt, made with gelatine as the emulsifying agent and containing about asphalt, about 25% water and a small amountof gelatine, may be used to stabilize a soap emulsion of asphalt. The gelatine emulsion andsoap emulsion are not miscible in all proportions unless the gelatine emulsion has been treated with a sufficient amount of alkali to bring it within a compatible range of pH value. The resulting system, with suilicient gelatine emulsion present is stable to substances such as Portland cement, although it is unstable to relatively large quantities of acidic electrolytes.

It will thus be seen that by regulating the proportions of the stable and unstable emulsions, the stability and time and extent of coalescence of the compound system may be thereby regulated. A further feature of my invention resides in the production of a compound system characterized as aforesaid. but which, in addition, is of lesser degree of viscosity comprising the compound system. It will be appreciated, of course, that while some of these emulsions wherein water constitutes the con tinuous phase are unstable to dilution, the ma- 1 jority of them, particularly those that are relatively stable, may be thinned to almost any desired extent by dilution with water. However, it is generally desirable to keep the water content of the emulsions as low as possiblenot only from the standpoint of the additional shipping cost entailed, but also because of the increase in the tendency of the dispersed particles to than either of the emulsions settle out of suspension upon increased dilution of the emulsion.v Hence, in road work, the emulsion must be comparatively thin in order to provide an efficient and economic material for coating or penetrating the road metal and yet contain a maximum bitumen content.

I have found, in accordance with my invention,

that when a clay emulsion, which, as ordinarily produced, is of comparatively viscid consistency, is mixed with a soap emulsion of about the same consistency, the resultant comp JllIld system when suitably proportioned, is of much thinner consistency than that of either of the component emulsions, and the suspendability of the system is improved, while at the same time the asphalt content is increased relative to the clay emulsion despite the increased fluidity. In fact, with certain types of relatively non-suspendable stable emulsions of the mineral powder type, the resultant system is completely suspendable.

The variations in consistency and fluidity of the mixture may be readily dbserved, and the proportions at which any desired fluidity can be secured. may be thus predetermined by adding to a given amount of clay emulsion, variable quantities of the soap emulsion. It will be observed that the initial additions of soap emulsion up to about 30 parts of the soap emulsion to 100 parts clay emulsion, serve to thicken the mixture and beyond this proportion the fluidity of the mixture increases progressively. At about equal parts of the separate emulsions, the mixture becomes very fluid as. compared to either of the separate emulsions. A desirable range of fluidity extends from about 40 parts to upwards of 200 parts of soap emulsion to 100 parts of clay emulsion, after which the fluidity of the mixture begins to'approach that of the soap emulsion.

A similar phenomenon is observed when mixing gelatin emulsions with soap emulsions, although the critical changes in consistency manifest themselves at somewhat different proportions.

By the use of the terms stable" and unstable in the claims I intend to limit the invention to one wherein the stable emulsion is of a type which is normally miscible in all proportions with an electrolyte, and wherein the unstable emulsion is one which normally is not miscible with all proportions of the same electrolyte.

I claim as my invention:

1. The process which comprises mixing an emulsion comprising bitumen of heat liquefiable character, water and clay, with an emulsion of bitumen of substantially the same melting point as the first claimed bitumen, water and soap, to produce the combined emulsion system having a consistency thinner than either of the original emulsions comprising the combined system and a bitumen content higher than either of said original emulsions at the same consistency.

2. A combined emulsion system of substantially predetermined abilltyto set, consisting of a mixture of an aqueous emulsion of clay, bitumen of heat liqueflable character and water, with an aqueous emulsion of bitumen of substan-. tially the same melting bitumen, soap and water, the combined system having a consistency thinner than either of the original emulsions comprising the combined system and a bitumen content higher than either of said original emulsions at the same consistency.

3. The process which comprises mixing an aqueous emulsion of bitumen which normally is point as the first named capable of admixture with fine mineral powders or electrolytes without breaking and at the same time capable of a substantial degree of coalescence without complete dehydration the bitumen content in the 'two dispersions before their admixture being of heat liqueflable character and of similar melting points and said combined system being of lower viscosity than either of the original emulsions comprising it and having a higher asphalt content than either of said emulsions at the same viscosity. V 1

4. The process which comprises mixing an aqueous emulsion of bitumen which normallyis miscible in all proportions with an electrolyte, with an aqueous emulsion of bitumen which normally is not miscible in all proportions with such electrolyte, to produce an emulsion capable of admixture with fine mineral powders or electrolytes without breaking, and at the same time capable of coalescence in a period of time less than one third of the time required for the first named emulsion to set the bitumen content in the two dispersions before their admixture being of heat liquefiable character and of similar melting points and said combined system being characterized by a lower viscosity than either of the emulsions comprised by it and having a higher bitumen content than either of said emulsions at the same viscosity.

5. The process which comprises mixing an aqueous emulsion of bitumen which normally is miscible in all proportions with an electrolyte, with an aqueous emulsion of bitumen which normally is not miscible in all proportions with such electrolyte, to produce an emulsion capable f admixture with fine mineral powders or electrolytes without breaking, and at the sane time capable of coalescence 'in a period 0 ine substantially less than the time required for the first named emulsion to set the bitumen content 8' in the two dispersions before their admixture being of heat liquefiable character and of similar melting points and said combined system being characterized by a lower viscosity than either of the emulsions comprised by it and having a higher bitumen content than either of said emulsions at the same viscosity.

6. A combined emulsion system capable of admixture with fine mineral powders or electrolytes without breaking and capable of a substantial degree o1 coalescence without complete dehydra-= tion, comprising a mixture of a relatively stable emulsion comprising bitumen, water and a stable emulsifying agent and an aqueous emulsion of relativelyunstable character comprising bitumen,

i an unstable emulsifying agent and water, with the. bitumens of the said emulsion being of heat liquefiable charac er and of substantially the same melting point, said compound system being characterized by a lower viscosity than either of the original emulsions comprising it and a higher bitumen content than either of said emulsionsat the same viscosity.

' LESTER KIRSCHBRAUN.