US2974107A - Preparation of quick-breaking bituminous emulsions characterized by improved demulsibility - Google Patents

Description

2,074,107 Patented Mar. 7, 196] PREPARATION OF QUICK-BREAKING BITUMI- NOUS EMULSIONS CHARACTERIZED BY M- PROVED DEMULSIBILITY Edward W. Mertens and James R. Wright, El Cerrito,

Callfi, assignors to California Research Corporation,

The present invention concerns a new method of preventing impairment of certain critical properties of quick-breaking oil-in-water type bituminous emulsions prior to their actual use in road work and the like. More particularly, it relates to a method of preparing quick-breaking bituminous emulsions from readily emulsifiable asphalts, in such a way that the demulsibility of the finished emulsion is either enhanced, held constant, or at least maintained within the limits set up in the specifications of the trade.

The term readily emulsifiable asphalts as employed herein refers to asphalts with acid numbers equal to at least 2.0 and higher, and particularly to asphalts rich in emulsifying acids (naphthenic and/or asphaltic) and characterized by acid numbers in the range from about 3.0 to about 4.0. These asphalts are available on the market in substantial volumes, and since they readily lend themselves for the emulsification in situ with conventional emulsifying bases, such as NaOH or KOH, they could have been regarded as a very attractive source material for the preparation of quick-breaking asphalt-inwater road emulsions. However,-in actual practice it has been noted that the emulsions prepared from these asphalts tend to undergo a rapid reduction in demulsibility. In fact, this reduction is often so severe that the emulsified material does not conform to the specifications of the trade, and, being too stable, becomes useless when actually applied to the aggregate. Furthermore, emulsions prepared from these asphalts display poor adhesion property, while their viscosity often undergoes a substantial drop prior to the actualuse.

Substitution of neutral electrolytes for a portion of the alkali metal hydroxide base, for instance, substitution of an alkali metal chloride, chromate or the like, does not remedy the situation: true, adhesion may be improved thereby, particularly when using chromates, but demulsibility and viscosity continue to suffer Significant drops, particularly if stored for any appreciable length of time at tank temperatures from about 150 to about 170 F., normally maintained in storing asphalt emulsion. In all cases, the higher the proportion of the neutral electrolyte replacing the emulsifying base, the lower is the emulsion viscosity.

The exact causes of the drop of demulsibility and other undesirable fluctuations of emulsion properties are not completely understood, although it is believed that under the warm alkaline conditions obtainable in a storage tank, additional acids are formed in the emulsified asphalt by the hydrolysis of various materials present therein, such as anhydrides, esters, lactones, etc., which could not be saponified, or did not get saponified readily, by the conventional emulsifying base, such as NaOH, in the original emulsification step. These newly formed acids react with the alkaline base remaining in the emulsified asphalts and thus may occasion the drops in demulsibility and viscosity of the emulsion.

It has now been found that the demulsibility of quickbreaking emulsions prepared from readily emulsifiable asphalts, particularly from those characterized by acid numbers from about 3.0 to about 4.0, can be effectively and significantly improved so as to prevent adverse fluctuations thereof below the acceptable limits set in the specifications of the trade, such as ASTM Specification for Emulsified Asphalt D97753, which calls for a minimum demulsibility of 60% for Type RS-l and RS-2 emulsions. This stabilization of demulsibility is achieved by pretreating the asphalt, at temperatures from about 250 to about 325 F. and prior to the emulsification, with a nitrogen-containing material which reacts at these temperatures with carboxylic acids of the asphalt to form amides, for a sufficiently long period of time to cause the lowering of the acid number of the asphalt to at least 1.8 or lower, but not lower than about 0.8, and preferably to a figure in the range from about 1.5 to about 1.0.

Primary and secondary amines, ammonia and any other nitrogen-containing material reacting with a car-' in water with the aid of conventional emulsifying bases,

suchas NaOH or KOI-I.

The amidation treatment can be carried out in any convenient manner. Generally, the amidizing agent is stirred into the asphalt in the storage tank at a temperture within the range from about 250' to about 325 F. With thorough mixing, the reaction is completed within 30 to 60 minutes, as indicated by the measurement of the acid number which now falls within the range from 1.8 to about 0.8. Thereupon the treated material is either stored, or is immediately emulsified in a known manner (employing conventional emulsifying bases), and then may be stored for several days, usually without displaying any inordinately large reduction of demulsibility and viscosity characteristics. Upon prolonged storage (a week or longer) these properties may decrease somewhat but in most cases will remain within the limits of the specifications of the trade, such as ASTM D977-53.

As mentioned above, the amidizing agent (amines, ammonia, and the like) may be admixed to the asphalt in the storage tank; or it may be introduced into the asphalt asit flows from the reduction column at the refinery to the storage tank; or it may be injected into the asphalt while this latter is passed through a recirculation system provided in the storage tank; or yet it may be added to the asphalt-containing crude oil before reduction of this latter. In all instances, the asphalt so treated, after its emulsification with the aid of conventional emulsifying bases (with and without neutral electrolytes), yields satisfactory, storable quick-breaking emulsions whose demulsibility and other properties conform to the specifications of the trade.

Suitable amidizing agents are: (1) primary and secondary aliphatic amines having as many as 18 alkyl carbon atoms, the low molecular weight ones being preferred because of their solubility in water; (2) alkanolamines, e.g., diethanolamine, and the like; (3) primary and secondary mononuclear aromatic amines, e.g., aniline, N- methyl aniline; (4) polyalkylene polyamines, e.g., tetraethylene pentamine; (5) polyalkanol polyamines, e.g., a material known in the trade under the name of Polyamine T, manufactured by Union Carbide Corp. as a bottoms product of triethanolamine manufacture; (6) other nitrogen-containing materials which at temperatures from about 250 to about 325 F. react with carboxylic acids of the asphalt to form amides, bringing the acid number of the asphalt to 1.8 and lower, for instance, a diisocyanate known in the trade under the name of Nacconate-300 and manufactured by National Aniline Division of Allied Chemical Corporation.

Quick-breaking emulsions prepared from readily emulsifiable asphalts which underwent the afore-described amidation treatment in order to reduce the acidity of these asphalts to 1.8 and lower, but not lower than about 0.8, and preferably between about 1.5 and 1.0, and thus to stabilize or at least to minimize the drop in demulsibility of the emulsions, may contain conventional additives which in their turn tend to enhance different emulsion properties, without impairing the benefits obtained in accordance with the present invention. Among these additives,there, may be mentioned neutral electrolytes, such as chlorides, phosphates, chromates, sulfates, nitrates, and the like; likewise, there may be added adhesion promoters, stabilizers, thickeners, dispersingagents, clay, etc.

The improvement of the emulsion properties brought about by thepretreatment of. asphalt in; accordance with the invention has been demonstrated and confirmed in a large number of tests. In each testseries asphalts with acidnumbers of 2.0 and higher were pretreated inaccordance with the invention prior to the emulsification which thereafter yielded quick-breaking emulsions'of an asphalt content between about .50 and 75 and preferably from about 55 to about 70% by weight; in other words, it gave emulsions coming within the purview of the ASTM Standard Specification D997-5 3 for Emulsified Asphalt of Type RS-l and RS- 2.

The results of several representative tests of one of said test series are given in Table I below to illustrate the practice and the various advantages of the invention.

A number of amidizing agents were used in these tests in amounts which ranged from 0.06% upwards by weight, based on the asphalt, and preferably from 0.125 to 0.25% by weight. Expressed in percent by weight of the ultimately formed quick-breaking emulsion, these percentages were 0.025% and upwards, and preferably from 0.20 to 0.40%.

The asphalt selected for the tests illustrated in Table I as being typical of those with acid numbers of 2.0 or higher, was a California 200-300 penetration-grade asphalt from San Ardo Field (the acid number of this asphalt lies between 3.0 and 3.8). The amidizing agents were thoroughly mixed with the asphalt for 30 minutes at 250 F., and the resulting mixture was emulsified, either immediately or following storage (as indicated in the table). When ammonia was used to amidize the asphalt, shorter treating periods than 30 minutes were required. The emulsions were prepared using 63% of the pretreated asphalt, distilled water and NaOH (0.07%) as the emulsifying base. Conventional neutral electrolytes, namely sodium chloride and sodium chromate, have been employed to replace a portion of the emulsifying base which was NaOH (0.07% by weight of the finalemulsion). When not immediately emulsified, the pretreated asphalt was stored at 250 F.

After emulsification, the emulsions were stored overnight for 18 hours at 120" F., and then their demulsibility and viscosity were determined in accordance with the recommended ASTM practice for testing emulsified asphalt (ASTM Standard Method D244-49). In the following table, viscosityis accordingly given in seconds (Saybol-t- Fnrol) at 122 F., and demulsibility in percent (as-determined with a 0.02 N calcium chloride solution).

Adhesion was also determined after overnight storage using a sample of 100 g. of dry Massachusetts rhyolitepassing all through a /8" sieve and retained all on a No. 4 sieve. An 8 g. sample of the emulsion, preheated to 120 F., is added to the stone with stirring to insure a good coating. The vessel containing this mixture is placed in an oven for 24 hours at 200 F. and then-stirred again to provide a complete coating of the aggregate. A 50 g. sample of the so cured mixture is dropped into a beaker containing 400 cc. of boiling distilled water for onerninute, again with stirring ata rate of rpm. The beaker is then withdrawn from the hot plate, any fioatingasphalt film removed, and the rhyolite sample withdrawn and dried, whereupon the area of the stone still coated with asphalt is estimated (in :percent, average).

Adhesion is considered to be satisfactory when at least of all aggregate surface remains coated by asphalt.

TABLE I breaking emulsions Amidizing Agent Neutral Electrolyte Properties Determined After 18 Hours at 120 F.

Run No. Percent Percent In Percent Adhesion Name by Wt. Name by Wt. Viscosity, Demulsi- 111 of Emulof Emul- SSF/122 F. bility (0.02 Percent sion sion N CaClz) 155 48 0. 16 337 75 20 0. l6 99 70 0. 22 70 65 (L 22 206 00 0. 20 247 67 65 Aniline 0. 16 307 87 30 8-- Armeen HTD L. 0,16 97 0 9 Polyamine T 0.25 NazCIO4 0.20 235 98 85 do 3 0.10 N32Ci0l..- 0.20 441 04 00 Polyamine T NaQCrO4 0.20 496 88 5 .do.-. Na2CrO4 0. 20 433 71 7 0. 20 2 (0 0. 20 107 61 7 0. 20 308 7 1 70 d 0.20 97 Ammonia.-- NazCrOn--. 0.20 157 68 do NagCrO4- 0. 20 202 of; 75 Diethylenc Triamine t 0. 05 NazOrO4- 0. 20 428 74 7o 1 Following the amidation treatment, asphalt was stored 64 hours at 250 F. 2 High molecular weight fatty amine material derived from hydrogenated tallow. manufactured and sold by Armour & Co.

* Bottoms product from the manufacture of triethanolamine, sold byUnion Carbide Corporation. 4 Diphenyl methane-4,4-diisocyanate, manufactured and sold by National Aniline Division of Allied Chemical Corporation.

5 Ammonia treatment lasted 5 and 15 minutes, respectively. Expressed as active material. Emulsion broke during the 18 hours of storage.

6 been used as neutral electrolytes, replacing a portion of the sodium hydroxide emulsifying base. Emulsification was carried out with distilled water as the external phase. After the emulsification, the emulsions were left to stand and their properties (viscosity, demulsibility and adhesion) determined upon 18 hours of overnight storage.

Followingadditional storage which lasted from 8 to 12 days, demulsibility and viscosity determinations were repeated. All of these determinations were carried out in the same manner as described in connection with the data in Table .I.

TABLE II Efiect of conditions of amidation on demulsibility and storage stability of emulsions Neutral Electrolytes Conditions of After 18 Hours at 120 F. n Further Storage Percent by Amidation at 120 F. Run Wt. of N o. Amidizing Agent 1 Percent Temp, Time 111 Vlscosity, Demulsi- Adhesion, Demulsi- Kind by Wt. F.' Minutes SSF/122 F. bility, Percent Days Viscosity bility Percent 0. 16 255 78 12 284 Na2OrO4. 0.16 250 30 172 99 12 160 90 Nazcrornn 0. 16 250 30 381 90 65 12 486 93 NazCrO4. 0.16 250 5 30 365 90 70 7 Na2C1O4 0.22 220 10 14 98 35 7 NaC 0. 22 250 30 206 85 7 307 97 N e01 0.22 70 65 10 56 B Emulsion broke on overnight storage. 1 Emulsion broken.

providing the same concentration of sodium ions, although it raised demulsibility somewhat (runs 2, 4, 6 and 15), could never raise it above about 75% (run No. 2). Furthermore, the application of chlorides, as contrasted With chromates, not only had little effect on, but, in fact, appeared to depress the adhesion property (run No. 2).

Contrasted with these unsatisfactory data, the amidalion treatment significantly improved the demulsibility, raising it as much as 100% (e.g., runs 8, 9, 10 and 17), and in all instances by not less than 25%, provided the amidizing agent was being employed in a sufficient concentration to bring the acid number down to 1.8 and lower, but, in all events, not lower than about 0.8, and preferably between about 1.5 and 1.0. When an insufiicient quantity of the amidizing agent was employed (as in runs 12, 16, 18 and 19), so that the acid number of the asphalt remained above 2.0, demulsibility barely conformed with the specifications and tended to drop down upon extended storage beyond the specified minimum of 60%. When asphalt treated in accordance with the invention was stored, the demulsibility of the emulsions eventually prepared therefrom rose apparently due to the completeness of the amidation treatment. However, when too high a concentration of the amidizing agent was employed (e.g., in runs :13 and 14), storage stability was adversely affected and the emulsion collapsed.

The effect of the conditions of amidation, namely, the temperature and the duration of amidation treatment, on the stability of the final asphalt emulsion is made apparent by the data shown in next Table II.

The emulsions which provided the data for this table have been prepared from the same San Ardo type asphalt pretreated at 220 F. for 5, l0 and -15 minutes with diethylenetriamine selected as an exemplary amidizing agent. Sodium chloride and sodium chromate have again The data in Table II clearly show that at temperatures outside the operative range from about 250 to about 325 F. the emulsions lack storage stability and break down, either overnight or in less than one'week (runs 1, 2, '3, 4, 5, 6, 7 and 12). On the contrary, when the asphalt is amidized within the operative range of temperatures, its emulsions display satisfactory demulsibility and viscosity, and, consequently, an adequate stability in storage. The test results also show that the longer the asphalt is stored following the amidation treatment, the

higher is the demulsibility of the emulsions preparedtherefrom.

The beneficial elfects of the amidation treatment on the demulsibility and viscosity of quick-breaking emulsions prepared from asphalts characterized by acid numerals equal to at least 2.0, and the reduced tendency of these two properties to deteriorate upon storage are additionally illustrated by the data in Table III, obtained in a series of test runs for which the same San Ardo type asphalt was described in connection with the data of Tables I and II. Viscosity and demulsibility determinations were repeatedafter further storage of the emulsions at F. for diiferent periods of time. The results of these determinations are all tabulated in the following Table III and point out that the amidation treatment in accordance withthe invention: prevents a runaway deterioration of these important emulsion characteristics.

a an acid number of at least 2.0, which comprises intimately contacting said asphaltat a temperature from about. 250 to about 325 F. with a nitrogen-containing material TABLE III Effect of prolonged'storage on emulsion properties Properties after Storage for Properties after Extended Storage at 160 F.

18 Hours at 160 F. Polyamine in Run No. Percent Demulsi- Viscosity, Days Demulsibility, Days by Wt. Viscosity bility in Adhesion in SSF/ Percent in 122 F. (0.02 N Percent 2 3 6 8 13 2 3 6 8 13 l Emulsion broken.

employed in an amount sufiicient to lower the acid num- 7 her of asphalt to 1.8 and lower, but not lower than about 0.8. Viscosity likewise remains high after 1 to 2 weeks of storage, and if too high (higher than 400 SSF/ 122 F. may be reduced to the specified limits by conventional methods.

The results of Table III unambiguously indicate that demulsibility is enhanced and does not drop significantly after a whole week of storage at temperatures in the range of from 150 to 170 F. conventionally employed by the trade in storing emulsified asphalt. Furthermore, even upon longer storage, demulsibility in many an instance remains within the minimum prescribed in the specifications.

The aforegiven description of the invention clearly indicates the several advantages in using the amidizing treatment for asphalts with acid numbers of 2.0 and higher. This treatment permits production of quickbreakingemulsions of improved demulsibility, viscosity and adhesion, capable of being stored without significant impairment of these properties, which could not be done in the past. By thus remaining within thelimits set forth for these properties in the existing specifications for quickbreaking paving and like emulsions, these materials are made acceptable to the trade.

Provided that the amidation treatment is applied at temperaturesfrom about 250 to about 325 F., and for.

a period of time from 30 to 60 minutes, it maybe immediately followed by the preparation of the emulsion in conventional fashion, and thus becomes a part of a continuous process which does not involve an unnecesary loss of time or require special aging in storage before the emulsification to insure that suflicient amidation and, consequently, sufiicient reduction of the acid number occurred.

Of course, it is to be understood that the invention as set'forth in the aforegiven description is not to be limited to any specific amidation agent, or any particular neutral electrolyte, whether employed in the examples or mentioned elsewhere in the description hereinabove. The examples merely serving to illustrate the operativeness. Thus; the invention is limited only by the definitions of the following claims.

What is claimed is: V

1; Axmeth'odof treating-an asphalt chaiacterizedbycapable to form amides with the carboxylic acids present in the asphalt at these temperatures, said nitrogen-containing material being contacted with the asphalt in an amount and for a period of: time sufiicient to reduce the acid number of said asphalt to a figure within the range from 1.8 to not lower thanabout 0.8..

2. A method of treating an asphalt characterized by an acid number of at least 2.0, which comprises intimately contacting said asphalt at a temperature from about 250 to about 325 F. with a nitrogen-containing material capable to form amides with the carboxylic acids present in the asphalt at these temperatures, said nitrogen-containing material being contacted with the asphalt in an amount and for a period of time sufficient to reduce the acid number of said asphalt to a figure within the range from about 1.5 to about 1.0.

3. A method as defined in claim 1, wherein the mac tion between the nitrogen-containing material and the carboxylic acids present in the asphalt is carried out at :a temperature from about 250 F. to about 325 F. for

at least 30 minutes.

4. A method of treating. an. asphalt characterized by an acid number of at least 2.0, which comprises intimately contacting said asphalt at a temperature from about 250 to about 325 F. with an amino-nitrogencontaining material capable to form amides with the carboxylic acids present in the asphalt at these temperatures, said amino-nitrogen-containing material being contacted with asphalt in an amount and for a period of time suificient to reduce the acid number of said asphalt to a figure within the range from 1.8 to not lower than 0.8.

5. A method of treating an asphalt characterized by an acid number of at least 2.0, which comprises intimately contacting said asphalt at a temperature from 250 to about 325 F. with an amino-nitrogen-containmg material capable to form amides with the carb-oxylic acids present in the asphalt at these temperatures, said ammo-nitrogen-containing material being contacted with the asphalt in an amount and for a period of time sufiicient to reduce the acid number of said asphalt to a figure within the range from about 1.5 to about 1.0.

6. A method as defined in claim 4, wherein the reac tron between the amino-nitrogen-containing material and the carboxylic acids present in the asphalt is carried out at a temperature from about 250 F. to 325 F. for at least 30 minutes.

7. A process for the production of quick-breaking asphalt emulsions, which comprises intimately contacting at a-tempertaure from about 250 to*325''F. for at least minutes an asphalt characterized by an acid number of at least 2.0 with an amino-nitrogen-containing material which reacts at these temperatures with the carboxylic acids in said asphalt to form amides, said material being added to the asphalt in a sufiicient amount to reduce the acid number thereof to a figure in the range from 1.8 to not lower than about 0.8, and emulsifying from about to about 75% by weight of the resultant product mixture in Water with an alkali metalemulsifying base to produce an asphalt-in-water emulsion characterized by viscosity which conforms with ASTM Specification D977-53 for rapid-setting emulsified asphalt, and has a minimum demulsibility of 8. A process for the production of quick-breaking asphalt emulsions, which comprises intimately contacting at a temperature from about 250 to 325 F. for at least 30 minutes an asphalt characterized by an acid number of at least 2.0 with an amino-nitrogen-contaiuing material which reacts at these temperatures with the carboxylic acids in said asphalt to form amides, said material being added to the asphalt in a sufiicient amount to reduce the acid number thereof to a figure in the range from 1.8 to not lower than about 0.8, and emulsifying from about 50 to about by weight of the resultant product mixture in Water with an alkali metal-emulsifying base to produce an asphalt-in-water emulsion which, after having been stored for one week at F., conforms with respect to its viscosity to ASTM Specification D-977-53 for rapid-setting emulsified asphalt, and has a minimum demulsibility of 60%.

References Cited in the file of this patent UNITED STATES PATENTS 2,317,959 Johnson et a1. Apr. 27, 1943 2,585,336 McCoy Feb. 12, 1952 2,652,341 Craig Sept. 15, 1953 2,819,228 Dell Jan. 7, 1958

Claims (2)

1. A METHOD OF TREATING AN ASPHALT CHARACTERIZED BY AN ACID NUMBER OF AT LEAST 2.0, WHICH COMPRISES INTIMATELY CONTACTING SAID ASPHALT AT A TEMPERATURE FROM ABOUT 250 TO ABOUT 325*F. WITH A NITROGEN-CONTAINING MATERIAL CAPABLE TO FORM AMIDES WITH THE CARBOXYLIC ACIDS PRESENT IN THE ASPHALT AT THESE TEMPERATURES, SAID NITROGEN-CONTAINING MATERIAL BEING CONTACTED WITH THE ASPHALT IN AN AMOUNT AND FOR A PERIOD OF TIME SUFFICIENT TO REDUCE THE ACID NUMBER OF SAID ASPHALT TO A FIGURE WITHIN THE RANGE FROM 1.8 TO NOT LOWER THAN ABOUT 0.8.

7. A PROCESS FOR THE PRODUCTION OF QUICK-BREAKING ASPHALT EMULSIONS, WHICH COMPRISES INTIMATELY CONTACTING AT A TEMPERATURE FROM ABOUT 250* TO 325*F. FOR AT LEAST 30 MINUTES AN ASPHALT CHARACTERIZED BY AN ACID NUMBER OF AT LEAST 2.0 WITH AN AMINO-NITROGEN-CONTAINING MATERIAL WHICH REACTS AT THESE TEMPERATURES WITH THE CARBOXYLIC ACIDS IN SAID ASPHALT TO FORM AMIDES, SAID MATERIAL BEING ADDED TO THE ASPHALT IN A SUFFICIENT AMOUNT TO REDUCE THE ACID NUMBER THEREOF TO A FIGURE IN THE RANGE FROM 1.8 TO NOT LOWER THAN ABOUT 0.8, AND EMULSIFYING FROM ABOUT 50 TO ABOUT 75% BY WEIGHT OF THE RESULTANT PRODUCT MIXTURE IN WATER WITH AN ALKALI METALEMULSIFYING BASE TO PRODUCE AN ASPHALT-IN-WATER EMULSION CHARACTERIZED BY VISCOSITY WHICH CONFORMS WITH ASTM SPECIFICATION D-977-53 FOR RAPID-SETTING EMULSIFIED ASPHALT, AND HAS A MINIMUM DEMULSIBILITY OF 60%.