US2521542A

US2521542A - Bituminous emulsions

Info

Publication number: US2521542A
Application number: US736111A
Authority: US
Inventors: Walter J Schwarz
Original assignee: Patent and Licensing Corp
Current assignee: Patent and Licensing Corp
Priority date: 1947-03-20
Filing date: 1947-03-20
Publication date: 1950-09-05
Anticipated expiration: 1967-09-05

Description

Patented Sept. 5, 1950 UNITED STATES PATEN BITUMINOUS aMonslons Walter J Schwarz, New Orleans, La., assignor to The Patent and Licensing Corporation, New York, N. Y., a corporation of Massachusetts No Drawing. Application March 20, 1947,

' Serial No. 736,111

7 Claimss (01.252-3115) V This invention relates to aqueous emulsions: of bituminous substances, such as asphalts, pitches, waxes and the like, and more particularly to emulsions of such substances made by the use of water swellable clays such as bentonite, as the emulsifying agent.

Bituminous emulsions of the type above referred to are well knownand have been employed for various industrial purposes. These emulsions, as normally manufactured, are composed, for example, in the case of asphalt emul-'- sions, of from approximately 45 to 60 of asphalt,

2 to 3% of bentonite as the emulsifying agent and 38 to 52% of water, depending upon the softening point and other physical properties of the asphalt and upon the technique employed to bring about emulsification thereof. Generally speaking, the asphalt is emulsified by heating the same to a temperature substantially above its softening point and feeding it while in moltenv state and at a, predetermined temperature to suitable emulsifying apparatus, concurrently with the feeding thereto of an aqueous suspension or slip of the bentonite. The emulsifying apparatus is provided with agitating blades of suitable design so that in the operation the liquefied asphalt becomes dispersed or emulsified in the aqueous phase by forces of attenuation and interfacial trituration, the emulsified particles being held in suspension in the aqueous phase and prevented from coalescing therein by the adsorbedfilms of water and bentonite. 5

Depending mainly upon the'character .of the asphalt and the amount of water employed in the manufacture, asphalt emulsions of the type:

above described are of rather viscous, sometimes pasty, consistency when discharged from the Since the water is in the external phase, these emulsions can be thinemulsifying apparatus.

ned by dilution with water but this means of reducing the viscosity of the emulsions is undesirable, especially where the emulsions are to be shipped over any considerable distance from the point of their manufacture to the point of their use. It is known that the fluidity of these emulsions may be increased withoutincreasing the water content thereof, by subjecting the emulsion to a beating action, as described, for example, in the patent to Kirschbraun No. 1,616,904. The amount of thinning action that may be effected by such beating treatment however, of a limited order. Furthermore, even when thus ,thlnned, these emulsions. exhibit a strong tendency.

the material at the point of use. Frequently, the

emulsions became gelled to an extent such that allic acid, when employed j 1 m d salts are employed insuitableproportio they donot have sufiicient fluidity to enable themto be discharged from bung-type drums orother; containers in which theyareshipped. i-; 1' The principal object ofthe invention isto pro,-, vide emulsions of the general characterabove indicated, having, however, considerably higher fluidity than is normally characteristic thereof without materially increasing the water content-i More specifically, it is an object of theinvention to provide emulsions of this character, which}, will retain the higher degree of fluidity, over-rel-f atively long periods of time during which the, product may be in storage or shipment; V .1 In thepatent to- KirschbraunNo. 1,918,759, it..- is proposed to convert the relatively thick short-g bodied consistency of bituminous emulsions madej with bentonite as the emulsifying agentinto-a; relatively thin long-bodied consistency, by treats; ing them with small quantities of certain g-or-z ganic acids. Although certain of the acidsregi ferred to in that patent have been found to be eifective for that purpose, the viscosity depressgj ing effect thereof in most instances isiprimarilya an initial effect which doesnot endure'for a substantial period oftime, the emulsion revertinggto'i a substantiallythickened or non-fluid condition;' within relatively: short periods. of time, especially relatively'small quantities. of water soluble; all-4.:

kaline sal-ts'of certain organic acids, :ashereina after to be more particularly set forth,'the amount of the salt employed for this purpose being gov I erned largely by the initial viscositycof theemule 3;; sion, and the degree and permanence of viscosity depressing effect desired. I

More specifically 1 have found, that th kaline salts, and preferably the sodium salts, such acids as tannic acid, gallic acid and, pyro amounts, of the order of from 0.05% .to 0,,5 by weight of the emulsion,- are effectivefor-bring-s; ing about-a very marked reduction inthe; viscosity ofthe emulsion... Moreover, when'these;

viscosity of the emulsion ;will not. materially in crease over considerable periods of time, say o;- the orderof30 to daysfl 1- In the .case of sodium tannateQthefam n thereof may, vary from 0,06%to .0,2%iby:we ghts, of the emulsion; with sodium gallate the amount 9 employed may vary from 0.05% to 0.5% by weight of the emulsion; and when employing sodium pyrogallate, the amount may vary from 0.05% to 0.30% by weight of the emulsion.

Thus by my invention it becomes possible, for example, to produce bituminous emulsions containing as high as 57% to 60% of dispersed bitumen, but having a fluidity comparable to or higher than that of an emulsion containing 45% to 58% of the same bitumen, as normally made without the treatment embodying the invention.

Preferably, the treatment of the emulsion with the selected salt is effected in the presence of a small excess of free alkali, as may be obtained by reacting sodium hydroxide with the corresponding organic acid in an amount in excess of that required to react with all the available carboxyl and hydroxyl groups of the acid. I have found that the provision of such excess alkali inhibits progressive gelation and consequent thickening of the emulsion which might otherwise result from electrolytic action when the emulsion is stored or shipped in metal containers. The amount of excess alkali for this purpose is such as to impart to the treated emulsion a pH value within the range of approximately 7.8 to 12.0.

In terms of actual measurement, the fluidity of the emulsions herein referred to is reflected by the readings in centipoises taken on a Brookfleld viscosimeter at temperatures of 77-85 F. From the practical standpoint, the emulsions are considered to possess a fluidity satisfactory for handling if Brookfield viscosity value thereof is less than about 7000 centipoises. Preferably, however, the viscosity should not exceed 4500 centipoises. These values are the average of the centipoise readings taken with the spindle of the Brookfield viscosimeter rotating at speeds of 6, 12, 30 and 60 R. P. M., and when the readings have come to equilibrium (usually after about five minutes) In referring to the fact that the emulsions produced in accordance with the invention do not undergo material increase of viscosity during storage for a stated period of time, it is meant that the viscosity at the end of the -period of storage will nevertheless be within the range of values above indicated, though the viscosity may be higher than when measured at the beginning of the storage period. In this sense, the fluidity of the emulsion may be considered as virtually unchanged, for although the numerical rise in ccntipoise viscosity reading may be higher at the end of the storage period than at its beginning, the product is as fluid for handling after the storage period as at its outset. In other instances, the viscosity at the end of the storage period may be even lower than at the outset.

The treatment of the emulsion according to the invention is preferably performed by incorporating the selected treating salt in the emulsion when the latter is at a substantialiy lower temperature than that at which it is discharged from the emulsifying apparatus. The temperature of the emulsion at the time of treatment may be from normal atmospheric to about 135 F.

Preferably, the required amount of the selected salt is added to the emulsion in the form of a concentrated solution thereof in water, usually not-less than a 10% solution, in order that the amount of additional water thereby added to the emulsion shall be as little as possible. The solution of the salt is preferably incorporated in the emulsion in successive increments while the 4 emulsion is stirred or agitated, although in certain instances it may be desirable to incorporate a portion of the solution, constituting in some cases only a minor portion thereof, in the manner above indicated, the balance being added to the thus treated emulsion after it has been delivered to a storage tank.

The following are specific examples, illustrating the practice of the invention:

Example I This example illustrates the invention as applied for the treatment of an emulsion of asphalt of relatively high softening point asphalt, say to F., and having relatively high solids content. (i. e., relatively low water content). Asphalt having a softening point of approximately 185 F., and 0 penetration (at 77 F.), is emulsified in water, with bentonite clay as the emulsifying agent. The emulsification is carried on -so as to produce a base emulsion having substantially the following composition, in parts by weight:

Asphalt 54.5 Bentom'te 2.5 Water 43 As normally produced, this emulsion is of a heavy paste consistency (far too heavy to permit of taking a viscosity reading on the Brookfield, the maximum reading on which is 100,000 centipoises) and its pH value is approximately 6.5.

In 99.8 parts of the above emulsion there is incorporated 0.2 part of sodium tannate (solids, by weight, based on the total emulsion) composed of equal parts by weight (solid basis) of sodium hydroxide and tannic acid in a 10% aqueous solution. This solution is added to the emulsion in successive increments, the emulsion being preferably agitated during the addition of at least the first several increments of the treating solution. By this treatment, although the water content has been increased only to approximately 43.6% from the. original water content of 43.0%, the heavy paste or buttery consistency of the base emulsionis transformed to a fluidity of the order reflected by a viscosity of approrimateiy 1820 centipoises. After a storage period of fifty days, the emulsion thus treated retained its fluid ity, exhibiting, if any change in this respect, a thinner: consistency than at the beginning of the storage period, as reflected by a viscosity of the order of '860 centipoises.

It will be noted that in this example, sodium tannate was made .up of equal par-ts by weight of sodium hydroxide and tannnic acid. Tannic acid having a molecular weight of 322.2..and sodium hydroxide having a molecular weightof 40.,

it will be seen that equal parts :by weight is equivalent to 8 moles of sodium hydroxide to 1 mole of tannic acid, or an excess :of 2 moles :of

sodium hydroxideover the alkali required to react with all the available (six). hydroxyl groups of the tannic acid. In terms .of excess .alkali, this amounts to 0.026% freealkali, based on the total weight of the emulsion, resulting in a .pH value of 1.1.6.

Example If In this example, a similar base emulsion as referred to in Example I is treated with the same quantity of sodium tannate' as in Example I,. but in this instance the sodium tanna'te was made up of 1 part of tannic acid and 0.75 part of so-, dium hydroxide (solids weight basis), in solution in 2 parts water. It will be seen, therefore, that 75 in this example, the sodium tannate is made up of one mole of the acid and six moles orthe alkali, i. e., the amount of alkali used was the amount required to react with all the available (six) hydroxyl groups of the tannic acid, and no free alkali was, therefore, present. The thus treated emulsion had a pH of 8.9.

The result of this treatment upon the base emulsion was to transform its initial heavy paste consistency into a fluid condition of the order indicated by a viscosity of approximately 19,000 oentipoises. Although the viscosity depressing efiect was thus less than in the treatment in accordance with Example I, the treated emulsion of this example exhibited a suflicient thinning out trend, so that at the end of a storage period of approximately seventy days, the viscosity was approximately 4300 centipoises. From a practical point of view, the emulsion thus treated is fluid enough to be discharged from a bungtype drum, though not as fluid as is usually desirable for shipment in this type of container.

Example III In this example, 99.8 parts, by weight, of the same base emulsion as referred to in Example II, is treated with 0.2 part (by weight solids based on the total emulsion) of sodium tannate composed of 3 parts of sodium hydroxide (solid basis) and 1 part tannic acid (solid basis), in a 20% aqueous solution. It will be noted that the sodium tannate used in this example contained 18 moles of excess sodium hydroxide; in terms of free alkali, this amounts to 0.112% free sodium hydroxide by weight, based on the total emulsion. The pH value of the treated emulsion was 11.6. With the sodium tannate of this example, the heavy paste condition of the base emulsion was transformed to a fluid condition reflected by viscosity reading of 1720 centipoises. The fluidity remained substantially unaltered during a storage period of ninety-five days, at which time it exhibited, if any change in this respect, a slight decrease in viscosity, via, to .1620 centipoises.

Example IV In this example, the invention is illustrated with reference to an emulsion of an asphalt of substantially the same softening point as that in the previous examples, but the base emulsion as initially produced having a substantially higher water content than the base emulsion of the previous examples.

The base emulsion was made so as to have substantially the following composition, in parts by weight:

Asphalt (softening point 185 F.; penetra- The emulsion thus produced possesses a fluidity reflected by a viscosity of approximately 17,000 centipoises, and exhibits a tendency to gel to somewhat non-fluid condition in storage.

99.94% parts by weight of the emulsion was treated with 0.06 part by weight of sodium tannate made up of equal parts. by weight .(solid basis) of tannic acid and sodium hydroxide. This is equivalent, as in the case of Example I, to a ratio of 1 mole tannic acid to 8 moles sodium hydroxide. The sodium tannate was employed in a 20% aqueous solution. This treatment re sulted in a sizeable initial reduction in viscosity (to approximately 2000 centipoises) with a slight trend to thinning out during storage, so that at the end of a; Period of twenty-two days-storage, the viscosity of the emulsionwas approximately 1450 centipoises. p 4 f Example V In this instance, the treatment in accordance with the invention was appliedto'a'n- 'e'mulsionof an asphalt having a softening point of 110*to 120 F., i. e., a considerably lower softening point than that referred to in the previous. examples, the emulsion, however, having .a water content approximately the same as the base emulsions .in Example I, II and III. Steam refined asphalt havinga softening point of approximately 112 F., and a penetration of 85 to 100 at 77 emulsified with bentonite. as the emulsifying-agent, to producea-base. emulsionhaving substantially the following composi- This base emulsion has a pH value of approximately 7.2 and a fluidity such as reflected by a viscosityof' 23,000 centipoises. I weight of this base emulsion'was treated "with 0.1 part by weight of'sodium tannate composed of 1 part tannic acidand 0.75 part sodium hy-g droxide (solids basis). In other words, the so dium' tannate was made up of one'mole of the tannic acid and six moles of sodium hydroxide. The pH of the treated emulsion was 9.5. The effect of this treatment was to 'depress the visf-Q cosity to a value of approximately 3500 new tipoises, this viscosity remaining substantially.

unaltered during a storageperiod of thirty-two days. Example VI 99.94 parts by weight of the same baseemul-vv sion as referred to in Example V, was treated with 0.06 part by weightof sodium tannate composed of equal parts by weight of sodium hydroxide and tannic acid.- Thus, in-this instance,

the sodium tannate was made up in a molar ratio of 8 moles of sodium hydroxide to1i=1 mole-of tannic acid, or an excess of 2 moles of sodium hydroxide over the alkali needed to react with the available hydroxyl groups.

Under these conditions, the. treatment of the. emulsion with the sodiumtannate depressedtheg viscosity of the emulsion to substantially the;

same extent, namely, to a-viscosity of aboute3500 centipoises, as.in the case of the sodium tannate employed inExampleV. However, whereas in. thecase of Example V there was no material; change of a viscosity after' a storage period .01; thirty-two days, the viscosity of the emulsion,

treated according to this example increasedsome what, viz., to approximately 6700 -centip0ises, whenstoredfor thirty-twd days. 1 From this. standpoint, therefore, the treatment according to Example V may be considered asproviding a better over-all effect for thisbaseemuleion than does the treatment of this example,

Erample j l I resulted in depressing the viscosity of the base 99.9 partsfby 7 amal am emulsion toa viscosity of the-order: of 1 200 centipoises. After a thirty-two day storage period, the viscosity increased only slightly. Thus, the treatment according to thisexample may be considered more efiective for this base emulsion than either of thetreatments described in Examples V and Example VIII ,In this example, there-is illustrated the use of sodium pyrogallateas the viscosity depressing agent.

In this instance, 99.8 parts of a base emulsion of 185 Fymelt point asphalt having a water content of'46;0% were-treated with 0.2% part 1 by weight of sodium pyrogallate made by-reacting sodium hydroxide with pyrogallic acid in proportions toprovide a mole ratio of 1 mole ofthe acid to 3 moles of the hydroxide. This treatment resulted in depressing the viscosity of the base emulsion from a paste consistency to approximately '11'00 centipoises. The pH of this emulsion was 10.1.

Example IX In this example, there is illustrated the use of sodium .gallate as the viscosity depressant.

"In this instance 99.94 parts of a base emulsion of 185 F. melt point asphalt having a water content of 500% were treated with 0.06 part by weight of sodium gallate, made by reacting 1 mole gallic acid with'4 moles sodium hydroxide. (Thebase emulsionhad been stored for a considerable'time and in spite of the high water content had gelled to paste consistency.) The treatnient resulted'in depressing the viscosity from a p,

paste consistency to approximately 1200 centipoises. The pH of this emulsion was'7.8.

I claim:

1. A bituminous emulsion consisting essentially of approximatelyato 60% .bitumen-asthe'disperse phase, approximately 1.5 to 3% bentonite as theemulsifying agent and water :as thecontinuousphase, and containing approximately 0.95 to :0.5%mby:weight-of analkali-metal salt of n organicacid selected-from the group consisting of tannic acid, =.gallic. acid and :pyrogallic acid, the amount of said salt being sufiicientflto impart to the qemulsionua viscosity.substantiallyclower than it normally possessesinxthe absence of said salt.

2. A bituminous :emulsion consisting essentiallyof approximately 45.to60% bitumen as the disperse phase,.approximately 1.5 to 3 %bentonite as theemulsifying agent and water as-the'continuouslphase, and: containing approximately 0.05

to- 0.5% by weighto'f an alkali metal salt of 'an organic acid selected I from the group consisting of tannic acid, gallic acid and pyrogallic acid, theam'ount-of said salt beingsufiicient to impart to -'the emulsion a viscosity substantially lowerthan it normally possesses in'the absence of said-salt, and a-n amount of free alkali to impart to the emulsion'a pI-I valuewithin'the range of 758 to 12.0.

3. A bituminous emulsion consisting essentially of approximately 45m 60% of bitumen as the disperse phase, approximately 1.5 to 3% bentonite as the emulsifying agent and water as the continuous phase, and containing approximately 0.05 to 0.5% by weight of an alkali metal salt of an organicacid selected 'from the group consisting of tannic acid, gallic acidand pyrogallic acid, said emulsion being characterized by an initial viscosity and a viscosity after storage for -'a period of notless thandays,substantiallylower'than 8 thein-itial viscosity and the;Viscosityaftersuch storage period,of-saidemulsion in the absence of said salt.

4. A bituminous emulsion consisting essentially of approximately to --%-bitumen as'the disperse phase, approximately 1.5 to 3% bentonite as the-emulsifying agent and water as the continuous phase, and-"containing0.06% 110-0.2% of sodium tannate, said-emulsion being characterized by an initial viscosity-and a viscosity after storage for a period ofnot lessthan 20"days,'substantially lower than the-initial viscosity and the viscosity after such storage period, of said'emulsion in the absence of said sodium tannate.

5. A bituminous emulsion consisting-essentially of 'approximately45to 60% of bitumen as-the disperse phase, approximately 1 .5 to 3% bentonite as theemulsifying agent-and -water as the continuous phase, said' bitumen having a softening point of approximately 1 to 185F., said emulsion containing 0.06 to 0.2% by weightof sodium tannate, said emulsion being characterized by an initial viscosity and a viscosity after storage fora periodpfnot less'than'20days, substantially lower than the initial viscosity and'the' viscosity after such storage-period, of'said'emulsion in the absenceof said sodium tann'ate.

6. A bituminous emulsionconsisting essentially of approximately '45-to 60% of bitumen as the disperse phase approximately 1.5 to' 3 bentonite as the emulsifying'agent and wateras the continuous pliase,said bitumen having a softening-point of approximately to "F., said emulsion containing-0.05m 0.5% by weight of sodium gallate, said emulsion being characterized by an initial viscosity and a "viscosity after storage fora period of not less than 20 days,'substantially lower than-the initial viscosity and the viscosity aftersuch storage period, of said emulsion in the absence of said sodium gallate. 7

1. A bituminous-emulsion consisting essentially of approximately 45 to 60% of bitumen asthe disperse phase, approximately 1.5to 3% ofbentonite as the emulsifying agent and water as the continuous phase, and containing 0.05 to 0.3% by weight of sodium pyrogallate, said emulsion being characterized by an initial viscosity anda viscosity after storage for a period of not less than 20 days, substantially lower than the initial viscosity and the viscosity after :such storage period, of said emulsion in the absence of .said sodium pyrogallate.

WALTERJ. SCHWARZ.

REFERENCES CITED The following references are of .record in the,

file of this patent:

UNITED STATES .I-ZATENTS .Number Name Date 1,918,759 Kirschbraun July 18, 1933 1,963,231 Fain June 19, 193.4 1,995,346 Halvorsen Mar..26, 1935 2,380,156 Dobson JulyllO, 1945 FOREIGN PATENTS Number Country Date 246,907 Great Britain Feb. 3, 1926 350,744 Great Britain June 18, 1931 OTHER REFERENCES Role of Clay and Other ,Minerals in Oil Well Drilling Fluids. Report of Investigation by.

Bureau of Mines. .Feb. 1941; R. I. 3556, p. '68.

(Copyin Division 64.)

Claims

1. A BITUMINOUS EMULSION CONSISTING ESSENTIALLY OF APPROXIMATELY 45 TO 60% BITUMEN AS THE DISPERSE PHASE, APPROXIMATELY 1.5 TO 3% BENTONITE AS THE EMULSIFYING AGENT AND WATER AS THE CONTINUOUS PHASE, AND CONTAINING APPROXIMATELY 0.05 TO 0.5% BY WEIGHT OF AN ALKALI METAL SALT OF AN ORGANIC ACID SELECTED FROM THE GROUP CONSISTING OF TANNIC ACID, GALLIC ACID AND PYROGALLIC ACID, THE AMOUNT OF SAID SALT BEING SUFFICIENT TO IMPART TO THE EMULSION A VISCOSITY SUBSTANTIALLY LOWER THAN IT NORMALLY POSESSES IN THE ABSENCE OF SAID SALT.