US2137975A - Process for producing asphalt emulsions - Google Patents

Description

Patented Nov. 22, 1938 UNITED STATES search Roor PATENT OFFICE PROCESS FOR PRODUCING ASPHALT EMULSIONS No Drawing. Application March 31, 1936, Serial No. 71,924

8 Claims.

The present invention relates to aqueous emulsions of bitumen or asphalt, pitches and the like and to a process for producing the same. Such emulsions may be suitably employed as binders, adhesives and coating compositions but are more particularly employed in road building. The invention relates particularly to the emulsification of asphalt separated from oils containing the same by means of solvents.

Heretofore, it has been proposed to produce the bituminous emulsions for use in road construction or for other commercial purposes by heating the bituminous substance, such as asphalt, to a temperature above its melting point and then adding a saponifiable material to the melted asphalt, such as, for example, a fatty acid, rosin or rosin oil. This mixture is then agitated with an aqueous solution of alkali such as, for example, caustic soda or potash or sodium or potassium carbonate, in order to effect the emulsification of the asphalt, or the asphalt may be emulsified by mixing it with a solution containing soap.

In recent years, another method has been proposed for producing aqueous bituminous emulsions. This method includes the steps of melting the asphalt and then agitating the melted asphalt with a dilute aqueous alkaline solution in order to effect the emulsification. In this process, no fatty acid or rosin or rosin oil or other saponifiable materials are added to the asphalt. The emulsification is aided by the saponification of the natural saponifiable materials which are present in the asphalt itself. It has been known to produce an asphalt of the quick-breaking type by this method, that is, one which will break rapidly when spread upon the surface or is brought into contact with the mineral aggregate. Such emulsions are suitably employed for road building by the so-called penetration method which consists essentially in spraying, pouring or pumping the asphalt emulsion upon the road bed. However, when it is desired to increase the permanency of the emulsion so as to permit it to be mixed with the aggregate without breaking rapidly, a small amount of casein or other stabilizing agent is incorporated into the emulsion. Such stabilized emulsions are suitably employed for road building by premixing the emulsion with the aggregrate and then spreading the mixture on the road bed which is followed by tamping and rolling, or the emulsion may be blade-mixed with the aggregate on the road bed.

However, it has been discovered that not all asphalts may be emulsified by direct admixture with an aqueous solution containing the alkali only to produce satisfactory commercial asphalt emulsions of the quick-breaking type. There are certain asphalts, among which may be mentioned certain asphalts produced from such California crude oils as Orcutt, Santa Maria, Santa Fe Springs, Torrance, Cat Canyon, Summerland, Carpenteria and Playa del Rey which will not emulsify with a solution of caustic alkali to give satisfactory commercial emulsions. For example, it has been found that substantially all grades regarding penetration and melting point of Santa Fe Springs, Playa del Rey, Summerland and Carpenteria asphalts produced by distillation are impossible to emulsify. Even the softer grades of asphalt, for example, 200 penetration at 77 F. will not emulsify with alkali alone. Some of the softer asphalts produced by distillation from the Orcutt, Torrance, Santa Maria and Cat Canyon crudes emulsify with caustic alkali alone to produce satisfactory emulsions of the quick-breaking type but the emulsification of such asphalts is not entirely dependable. In some instances, these asphalts fail to produce satisfactory commercial emulsions and, therefore, refineries do not recommend their use for the emulsification with caustic alkali alone. The harder grades of asphalt, for example, 60 penetration at 77 F., are entirely unsuitable for emulsification purposes with caustic alkali alone. The softer grades of the asphalts produced by distillation of such California crude oils as Poso Creek, Coalinga and McKittrick invariably produce satisfactory emulsions of the quick-breaking type with caustic alkali alone. However, the harder grades, for example, 30 penetration at 77 F. produced by distillation from such crude oils do not produce satisfactory commercial quick-breaking emulsions. Even with the softer grades of asphalt produced from the Poso Creek, Coalinga and McKittrick crude oils, I have found that not all of these always produce satisfactory commercial emulsions with caustic alkali alone. For example, the asphalts produced for the Coalinga and McKittrick crudes emulsify with caustic alkali alone into very viscous emulsions.

It will be understood that when I state herein that the asphalt will not emulsify or emulsifies imperfectly, I means that either the asphalt will not emulsify at all or it will not emulsify to produce a satisfactory commercial emulsion, that is, one which is reasonably useful for commercial purposes. Some asphalts which I do not consider suitable will emulsify to produce an emulsion or a dispersion but such does not possess the desirable characteristics regarding settlement,

demulsibility, stability and viscosity and thus does not meet the specifications set by the industry for good emulsions. For example, a satisfactory emulsion, according to present day specifications of some State authorities, is one which is a dispersion of asphalt as the discontinuous phase in water as the continuous phase. Such an emulsion should have a Saybolt Furol viscosity at 77 F. of not over 55 seconds, should contain no less than 55% of asphalt, should be sufficiently fine so that upon making a ten day settlement test, the asphalt content between the top 10% and bottom 10% should not differ by more than 6%. The emulsion should not get an increase appreciably in viscosity upon long storage, should be miscible in all proportions with water and should not reemulsify after the emulsion is broken.

I have discovered that it is possible to emulsify asphalts contained in such crude oils from which asphalts heretofore produced were difficult or impossible to emulsify with caustic alkali alone as the emulsifying agent. I have discovered that if the asphalt is separated from such crude oils by means of solvents capable of precipitating the asphalt or bitumen from the oil, the precipitated asphalt can be emulsified with a solution containing caustic alkali alone. In other words, where such asphalt produced by the ordinary distillation of a crude oil containing asphalt so as to remove petroleum oil fractions, such as gasoline, kerosene, gas oil and lubricating oils, were difficult to emulsify to produce emulsions of the quick breaking type, I have found that when the asphalt fraction is separated from such crude oils, or topped crude oils by means of a solvent, the resulting precipitated asphalt may be emulsified with the dilute aqueous solution of caustic alkali.

As has been stated heretofore, the asphalts separated by distillation from such California crude oils as Poso Creek, Coalinga and McKittrick produce satisfactory commercial emulsions but even such asphalts from Coalinga and McKittrick result in the production of high viscosity emulsions. Poso Creek asphalt appears to be a satisfactory asphalt for the production of emulsions with caustic alkali alone, except as to the harder grades It is believed that my invention has a broader aspect, i. e. that of the emulsification of an asphalt separated from an oil by means of a solvent and the invention has a number of advantages which are not obtainable by the emulsification of an asphalt produced by distillation.

It is, therefore, an object of my invention to separate asphalt from an oil containing the same by precipitation with a solvent and then emulsify the asphalt thus precipitated with a dilute aqueous alkaline solution.

Many other objects, features and advantages of my invention will become apparent to those skilled in the art from the following description which is not to be taken as limiting my invention.

As asphalt precipitating solvents, I prefer to use a liquefied normally gaseous hydrocarbon, such as ethane, ethylene, propane, propylene, butane, butylene and iso-butane or mixtures thereof. I prefer to use ethane or propane or mixtures of these hydrocarbons, or mixtures of these hydrocarbons with other hydrocarbons. However, I may employ such other asphalt precipitating solvents as pentane, hexane, gasoline,

solving oil but not the asphalt. Solvents for the precipitating asphalt and a method of precipitating asphalt for petroleum residues have been disclosed in the Bray Patent 1,944,491.

In order to effect the precipitation and separation of the asphalt from the asphalt-containing oil, the latter is mixed with an appropriate quantity of the asphalt precipitating solvent and the mixture is allowed to settle into two layers, i. e. an upper layer of oil dissolved in the solvent and a lower layer of the asphalt containing some oil and solvent. The upper layer is decanted from the alsphalt layer and the latter is then heated to a temperature sufficient to distill the solvent contained therein. When a liquefied normally gaseous hydrocarbon, such as liquid propane, is employed as the asphalt precipitating solvent, the latter may be removed from the precipitated asphalt by mere exposure to the atmosphere.

When liquid propane is employed as the asphalt precipitating solvent, the latter is commingled with the asphalt-containing oil under superatmospheric pressure sufficient to maintain the propane in the liquid state. Propane is liquil at ordinary temperatures of about 70 F. and at a pressure of about 125 lbs. per square inch. The amount of propane mixed with the asphaltcontaining oil will depend upon whether it is desired to remove the asphalt at the bottom of the settler or decanter employed as a slurry of asphalt and propane, i. e. as a mixture of substantially pure bitumen and propane, or as a liquid fraction containing asphalt and propane with some oil. If it is desired to separate the asphalt in the decanter as a liquid fraction, the volumetric ratio of propane to oil should be within the range of 0.6 to 6 to one volume of the oil depending upon the character of the residuum and the degree to which it has been topped. Higher volumetric ratios will effect precipitation of the asphalt as a slurry of substantially pure bitumen and propane. The propane may then be distilled from the asphalt slurry or liquid asphalt separated from the solution of oil and propane. The depropanized asphalt may then be emulsified in accordance with my invention.

One of the advantages of operating the asphalt precipitating process at ordinary temperatures or at elevated temperatures resides in the fact that the precipitated asphalt when separated from oils containing wax, will be reasonably free from wax, the presence of which in the asphalt is detrimental for some uses. By operating at such temperatures, the wax will be dissolved in the solvent and oil and may be decanted from the precipitated asphalt. However, it is also Within the scope of my invention to effect the precipitation of the asphalt at lower temperatures suflicient to also precipitate the wax and then emulsify the mixture of asphalt and wax. In some cases, it may be desirable to separate the greater portion of the asphalt at ordinary or elevated temperatures in one stage and then chill the decantate to a lower temperature sufiicient to precipitate the remaining asphalt and wax in a second stage. The asphalt in the wax, will, for the most part, be of a soft character and often emulsification of the mixture may be employed for waterproofing purposes when the dark character of the wax is not detrimental to the appearance of the material to be waterproofed.

In some instances, it is desirable to separate the asphalt as a substantially pure bitumen, that is, it is desirable to remove as much of the oil fractions from the asphalt as possible and replace the 252. QQMPOSlllONS.

oil fractions with oils from some other source. The removal of the oil fractions from the bitumen will result in the removal of a considerable amount of the naphthenic acids from the asphalt which are not of the proper kind to promote emulsification with caustic alkali. The bitumen substantially free from oil fractions may then be mixed with oil fractions from some other source to produce an asphalt of desired characteristics regarding melting point and penetration. This asphalt-oil mixture may then be emulsified in accordance with my invention. By replacing the oil fractions normally present in the asphalt with oils of a different character, such as oils separated from asphalts which readily emulsify with caustic alkali or oils containing the proper kind of asphaltic acids to promote emulsification, it is possible to emulsify the blended asphalt with such caustic alkali. For the purpose of blending the precipitated asphalt with an extraneous oil, I may employ lubricating oil distillates obtained from asphaltic crude oils, the residuums of which emulsify readily with caustic alkali such as those obtained from Poso Creek crude oils or I may blend the precipitated asphalt with all or a portion of the propane or other solvent soluble oils obtained from residuums of such crude oils. If desired, I may blend the precipitated asphalt with a neutral lubricating oil, i. e. one treated with acid and alkali, and this mixture may then be emulsified either with caustic alkali solution or with a soap solution or other solution containing saponifiable ingredients such as rosin, rosin oil or fatty acids.

It may also be desirable, in some instances, to blend the precipitated asphalt with asphalt produced by distillation and emulsify the mixture. Thus, by the addition of precipitated asphalt to asphalts produced by distillation and which are difficult to emulsify with an alkali, it is possible to emulsify such diflicultly emulsifiable asphalts. If desired, the precipitated asphalt may be emulsified separately and the distillation asphalt may then be gradually incorporated into the emulsified precipitated asphalt. In blending such asphalts with the precipitated asphalt, care should be exercised in not adding too much of the distillation asphalt so as to prevent emulsification of the admixture. It is possible to emulsify blends of equal quantities of the precipitated asphalt and the distillation reduced asphalt of the character which will not readily emulsify.

Emulsification of the precipitated asphalt may be accomplished by heating approximately 60% by weight of the precipitated asphalt to a temperature above its melting point, say 300 to 400 F., after which the melted asphalt is passed through a mixing device in which an aqueous solution of sodium hydroxide is mixed with the melted asphalt. The amount of sodium hydroxide contained in the solution should be sufiicient to provide approximately 0.08 to 0.18% by weight in the finished emulsion although this amount may vary with certain asphalts. The agitation by circulating the emulsion through the mixing device is continued until the asphalt is finely dispersed in the caustic soda solution. The emulsion as produced by the aforesaid process comprises one containing a fine particle size and is of the quick-breaking type. It may be passed to storage and used as a quick breaking emulsion without further treatment or addition of stabilizers. However, if it is desired to convert the quick breaking emulsion into one of the slow breaking type, a small amount, say 0.5 to 2.0% by weight of a stabilizing agent is incorporated into the quick breaking emulsion after the emulsion has been cooled to a temperature below approximately 100 F. As stabilizing agents, I may employ casein, glue, blood albumin, starch, gum acacia, agar agar, algin, gum tragacanth, pectin, Irish moss and other agents of the protein and carbohydrate type.

While the present invention is particularly directed to the emulsification of precipitated asphalt with a dilute aqueous solution of a caustic alkali, such as sodium or potassium hydroxide and thus produces the use of these alkalies for the emulsification of other asphalts, i. e. asphalts produced from crudes by distillation which heretofore could not be emulsified with alkali alone, it will be understood that it is within the scope of my invention to emulsify precipitated asphalts produced from any crude oil or residuum with other emulsifiers such as soaps of which may be mentioned sodium and potassium oleate, resinate, stearate and palmitate. The precipitation by means of a solvent process has the advantage over the distillation method for producing asphalts to be emulsified in that a cleaner asphalt is produced, that is, one which may be free from wax and which is free from cracked products, coke and coke-like materials.

The foregoing description of my invention is not to be considered as limited since many variations may be made by those skilled in the art within the scope of the following claims.

I claim:

1. A process for the production of an asphalt emulsion of the oil-in-water type by the use of an aqueous solution containing an alkali only as the emulsifying agent which comprises emulsifyan oil containing the same by precipitation with an asphalt precipitating agent, which oil is incapable of yielding an asphalt of the same grade by distillation which is capable of being emulsified with an aqueous solution containing alkali only.

2. A process as in claim 1 in which the emulsifying agent comprises sodium hydroxide.

3. A process for the production of an asphalt emulsion of the oil-in-water type by the use of an aqueous solution containing caustic alkali only as the emulsifying agent which comprises emulsifying with an aqueous solution containing only caustic alkali, an asphalt which has been separated from an oil containing the same by precipitationwith an asphalt precipitating agent, which oil is incapable of yielding an asphalt of the same grade by distillation which is capable of being emulsified with an aqueous solution containing caustic alkali only.

4. A process as in claim 1 in which the asphalt precipitating agent comprises a hydrocarbon solvent.

5. A process as in claim 1 in which the asphalt precipitating agent comprises a liquefied normally gaseous hydrocarbon.

6. A process as in claim 1 in which the solvent comprises liquid propane.

7. A process as in claim 1 in which the precipitated asphalt is blended with a hydrocarbon oil before being emulsified.

8. A process as in claim 1 in which the precipitated asphalt is first blended with an asphalt produced by distillation to produce a blended asphalt before being emulsified.