US1734437A - Production of aqueous dispersions - Google Patents

Description

Patented Nov. 5, 1929 UNITED STATES ATENT OFFICE PRODUCTION OF AQUEOUS DISPERSIONS No Drawing.

This application is a continuation in part of Serial No. 99,7 45, filed April th, 1926. the latter constituting a division of Serial No. 339,690, filed November 21st, 1919, and is 5 sued as Patent No. 1,615,303, dated January This invention relates to the production of dispersions more particularly to aqueous dispersions of heat-liquefiable bodies which are normally insoluble in, or immiscible with,

water.

Products of this nature have been indis criminately referred to as dispersions and as emulsions. Since, however, the latter term more technically and accurately speaking, comp'rehends suspensions of one liquid phase withinanother liquid phase immiscible with the first phase, and since, moreover, the product of the present invention in its most desirable embodiment, comprises in reality, substances which are commonly considered solid or semi-solid, but which may be dispersed in a fine state of subdivision in accordance with the principles herein to be set forth, I shall employ the term aqueous dispersion throughout the following description with the understanding that said term shall include suspensions within an aqueous vehicle, of substances normally solid or semi-solid, yet capable of movement at normal temperatures resembling glacial flow, and having a melting point ranging generally from 100 degrees F. to -200degrees more or less.

Briefly, dispersions such as are comprehended by the present invention are produced by agitating the substance tobe dispersed, brought to a more or less fluid and extensible condition by heat in the presence 0f.a colloid or other substance Orv-substances, which function,or which are capable of being modified so as to function in the capacity of dispersing media.

Thus, for example, asphalts, pitches and similar bases having a wide range of melting. points,:have been successfully dispersed with various types of dispersing media, and the products so obtained have been employed with some measure of success. These prodnets are generally miscible with water, and l in addition certain of these are more or less Application filed July 22,

1927. Serial No. 207,822.

resistant to the action of electrolytes while others are broken down in the presence of such substances.

The inability of the latter dispersions to resist the action of electrolytes has been one of the limitations upon the use of products of this nature, since by far the largest number of uses to which they could be put, involves the incorporationof other substances which are or contain electrolytes, such substances acting to either completely break down the dispersion or flocculate it to such an extent as to render it unfit for use. Viewed in one of its aspects therefore, the present invention is directed towards the production of dispersions which will not be broken down by the action of substantial quantities of electrolytes.

Again, an extensive field for these disper sions lies in the manufacture of waterproof paper products, the dispersion being utilized either by admixture with fibrous stock during thev process of formation of the paper, or as a film interposed between inner fibrous plies at the wet end of the paper-making machine. In either event, however, it is essential that the dispersion be characterized by a stability sufiicient to withstand the mechanical friction, the attrition, and the pressures. to which it is subjected during the felting operation, or during its application to the preformed web at the wet end.

Furthermore, these dispersions should be so stable that when they are mixed with, or there is incor orated therein, substantial quantities of pow ered pigments, mineral aggregate, hydr-aulic cement, or the like, they will not be deleteriously affected by such substances.

Viewed in another of its aspects, therefore,

this invention has, as an additional aim, the production of dispersions of the character described which will be sufliciently stable to resist the action of pressure, mechanical fric tion, attrition, and to be compatible wlth the introduction of electrolytes such as acids or salts, mineral aggregates, pigments finely d1- vided powders and substances of lilxe nature.

Further, where dispersions of the kind referred to are utilized immediately or within a short time after their production, it is not s essential that the dispersionbe one which is capable of remaining in suspension any great length of time, and as long as such dispersions are immune to the forces above men tioned which prevail during, or which are induced by such use, the disadvantages attending the'production of a relatively non-suspensible dispersion are not apparent. Where not used immediately, however, these products are generally barrelled and shipped long distances or they are stored in a quiescent state for considerable periods between the time they are. produced and the time they are actually put to use, and unless the dispersion is characterizedby a marked and well defined ability to remain in suspension for a sufficient length of time, it will be found-that the dispersed particles readily settle out of suspension and pack at the bottom of the container to a relatively stiff immobile cake, the aqueous content rising to the top, and in order to be restored to a suspendedcondition it is necessary to laboriously agitate the mass or subject it to some similar treatment whereby to re-suspend the dispersed particles. Tank car shipment of such product is obviously impossible.

The product is usually received at the place of application in barrels or drums where mechanical appliances cannot be made readily available and the-work of re-suspending such product must be done by hand. This is' obviously a troublesome procedure, involving great loss of time.

Viewed in another of its aspects, therefore, the present invention has for an object the production of dispersions which are suspensible to a high degree and which, in the presence of electrolytes, will remain unbroken, even though the electrolyte may be of such character and may be present in such quantity as to cause the dispersed particles to settle out of suspension.

The suspensibility of dispersions of the type referred to is dependent upon several factors,,each 0 which must be taken into consideration w 1811. it is desired to produce a product of this nature.

A prime consideration for producing this type of dispersion is to employ a dispersing agent, or combinations of such agents as are relatively chemically inert and not lilrelyto be altered by reacting with the specific electrolytes in a manner to cause them tocease to function and thereby cause the dispersion to break. Thus, alkali soaps and s9. onified oils which are frequently used to ma e bitumen-pitch type dispersions, are notoriously these dispersions.

unstable on account of the tendency of all salts of the heavy metals to produce the corresponding metallic soap, thereby destroying the capacity of the dispersing agent to vmaintain the system in the aqueous dispersed state. Lime and analogous substances 31501 break an the other hand certain types of dispersing agents such as organic and inorganic powders, are relatively inert I tallic'silicates, colloidal oxides, c'asein, other proteins, dextrine, etc., are examples although clays are generally preferred as possessing to the widest-extent,the inertness and other properties necessary to produce thedesired product. While mineralpowders of the type referred to have been used to disperse asphalts, and although they. possess the requisite resistance to electrolytes, they'are as stated before, incapable of-remaining in suspension.

It must be understood also, that the dispersing agent preferably may be of such nature and used in such quantity that the dispersion when once freed from water will not redisperse but will produce an irreversible. end product.-

For instance, when using relatively large quantities of bentonite alone as a. dispersing agent theresulting dispersion, although suspensible if prepared under properly controlled temperature conditions so as to get a fine particle size'will generally produce a water-free film which is not resistant to the continued action of Water to a sufficiently high degree if dried without agitation or application of heat. Where, however, such product is not intended for severe exposure to water persion here referred to, causin the dispersi0n to settle out despite the act that the particle size is of a rather fine order.

upon a careful control of the temperature maintained during the dispersing action, as hereinafter to be described. Hence, it is essential that optimum temperature conditions be maintained while carrying out the dis: persing operation and'that the dispersin agent be one that will not, in and of itsel give rise to this settling out in the finished dispersion, and where such'an a. nt; does take part in thedispersing action, it should, prior to the dispersing action, be mixedfor treated with another agent such that th final product will-be readily suspensible. Still another factor governing the suspensibility of dispersions of the type referred to,

is the'viscosity and bod ofthe finished'product. The viscosity an body are influenced,-

among other factors, by. the nat'ureof the I I particle size among other. factors, depends ature of the asphalt or the mass undergoing dispersion is too high, the material in the" dispersing apparatus must be cooled, or ad ditional water introduced, to avoid partial or complete coalescence of the particles. Therefore, high temperature operates to produce large particles and the body and viscositysulfer both from the large particle size and the increased amount of aqueous phase. As the, aqueous content of these dispersions is increased beyond a certain point, the suspensibility thereof is correspondingly endangered. It is essential therefore, with a critical balance of suspending factors, that the aqueous content of the product be maintained below the point where further dilution will substantially decrease the suspensibility. This is of special importance in those instances where electrolytes are to be incorporated with the dispersion.

In carrying out the present invention I may disperse any base normally immiscible with water. Such base may comprise for example, asphalt or other bituminous or hydrocarbon material, either of a solid or semi-solid consistency, and may be either native asphalt or asphalt of the so-called artificial variety such as is produced by air-blowin or steam refining asphaltic petroleum resi uums. In place, of asphalts, I may disperse materials of an analogous character, such as pitches of vegetable, animal or mineral origin, resins,

or resinous materials softened, if desired,

with suitable tempering or fluxmg oils. In order to effect the dispersing action for the purposes of the present invention, and as an illustration, I may use as the dispersing agent, clay containing a large proportion of colloidal matter. It should be apparent however, that other finely divided or colloidal-like substances such as those hereinbefore referred to may be used in place of the clay in carrying out the principles of this invention.

In certain cases it may be desirable to employ a mixture of dispersing agents, the separate constituents being mixed in such. quantities that the resultant combination possesses dispersive properties superior to those of either of the individual agents. Thus, by using 30% more or less, of bentonite and more or less, of ball clay, a dispersive medium is produced which will produce better dispersion than either alone, plus body and sus ensibility in the final product. Likewise en-tonite with upwardly of 5% casein relative to bentonite swollen .by the alkali and bentonite produces a media which disperses asphalt readily and gives a bodied end product and a much more water resistant dried film than either of these agents alone. Slate dust and bentonite suitably proportioned exemplifies another satisfactory starting medium.

As a specific illustration of a process by which the product of the present invention may be produced, I may disperse steam refined asphalt having a melting'po'iii't o'f'say, 100 to 200 degrees F., more or less, with colloidal clay as the dispersing agent.

This dispersion may be produced in batches or by a continuous process. If prepared as a batch, I first make a thick aqueous suspension of the collodial clay or prepared dispersion medium and heat it to a temperature approximating the melting point of the asphalt which is to be dispersed. The asphalt is also heated until it is fluid, the temperature varying with the viscosity of the asphalt and its melting point. Preferably, a temperature of 300 degrees to 400 degrees F., more or less, may be employed for the harder varieties of asphalt, while for the softer varieties a lower temperature affords the desired degree of fluidity. The aqueous suspension heretofore referred to may be produced in a vessel having means for rapidly agitating the contents thereof. Its consistency is such that it is too fluid to hold its form but sufiiciently viscous to flow slowly through a fair sized orifice. It is important that the consistency of this paste be regulated within more or less definite limits inasmuch as the degree of dispersion obtained during the dispersing operation depends largely upon the viscosity of the internal friction resulting in the agitation of the asphalt throughout the viscous clay suspension.

The molten asphalt is gradually added to the viscous suspension while the mass in the vessel is being subjected to rapid agitation. This is important in order to avoid inversion of phase. As the asphalt is introduced and continuously dispersed, the mass thickens, and it may become necessary to add water in order to maintain the desired viscosity of the contents of the vessel. The addition of asphalt is continued, alternating with the additions of water and in such quantities as to-maintain this desired consistency. If the vessel is sufiigiently large, water and asphalt may be add d simultaneously in the desired proportions. It is advantageous in some cases to introduce the asphalt at a temperature above the boiling point of water as the expansive force of the steam generated upon contact of the asphalt with the aqueous suspension produces more or less foaming, and extension of surface of the pitchy material during its incorporation; The mechanism of this dispersing operation is somewhat as follows: As the asphalt strikes thethick aqueous suspension it becomes immediately subjected to the agitating arms of the mixer. These arms produce rapid extension and subdivision of the stream of pitch into very fine threads throughout the mass of clay suspension. The viscosity of the thick suspension assists in the formation of these threads and their fine degree of attenuation. As these threads are being rapid-1y formed and rapidly attenuated, a point is reached depending upon the temperature of the mass, its viscosity and rapidity of agitation, at which the threads have become so fine and their surface so great that they become rap idly broken and subdivided into filaments which in turn become subjected to further subdivision until their length is such that their surface tension causes the minute threads thus formed to assume a globular or spherical form. This dispersion is produced notonly under the conditions and by the mechanical agency above referred to, but also through the presence of the colloid which in persion, the finer and hence more suspensible are the resulting particles. Their size varies, ranging from particles which are probably of colloidal dimensions to those which can be seen as individual particles with the naked eye. The average size of the particles is about .01 millimeter 10 mu). Some of the smaller particles exhibit distinctive Brownian movement. It should be noted that although the pitch is in liquid condition when introduced,

F the form of the particles or relation of phases ,does not change upon cooling and upon more or less hardening or solidification of the pitch in its subsequent reduction, to normal temperatures. The dispersion thus formed has the peculiar. characteristic of not being effected to the point of rupture by electrolytes.

It is important to note that a desirable feature in the preparation of this dispersion. resides in the degree of dispersion of the as phalt particles throughout the continuous phase. The fineness of dispersion is to a considerable extent regulated by the viscosity of the mass, which if it is desired to keep it fine,'sh0uld be relativelythick or paste-like during agitation and by its temperature. For example, if the clay suspension be too thin, and the necessary internal viscosity be lacking, the threads formed during the initial stages of dispersion are relatively coarseand the material thus comminuted may maintain various coarse stagesof subdivision ranging from relatively coarse threads dbwn to the finer particles. Likewise, if the temperature of either the asphaltor the suspension is too low, coarse particles are similarly formed. On the other hand should the temperature of the pitch or the partially formed material be too great, there is danger of partial or local coalescence of the previously formed material, due probably to the complete removal of water by'heat from around some of the asphalt particles at the point of confluence with the incoming hot liquid asphalt. Furthermore, care' should be taken to have sufficient Water present at all times as otherwise the asphalt will agglomerate producing complete inversion of the phase, wherein the water and clay would then constitute the internal phase with the asphalt the continuous medium.

I have found that when using asphalt of about 140 degrees F. melting point, a desirable temperature at which to maintain the clay suspension at the start is about 150 degrees F., more or less, this same "temperature being maintained as the batch is being increased during the continual addition of asphalt.

If desired, the maintenance of the proper temperature may be facilitated or assisted by employing a dispersing apparatus provided with external jackets, or even with internal conduits, throughwhich any suitable temperature regulating medium may be led.

The non-adhesive character of the emulsion and its desirable degree of dispersion may be roughly ascertained by manual manipulation. A-quantity. of material when worked between the fingers should feel smooth, plastic, slippery and free from grit particles and 'should exhibit no tendency for the particles 'of asphalt to agglomerate among themselves when pressed or rubbed between the fingers. In fact, the emulsion thus produced should feel substantially like the thick clay suspenion originally employed in its production. It should be readily washed from the hands with water and should be capable of dilution in all proportions with further quantities of water. If it should be desired to retain the asphalt particles in suspension to the best possible extent, a protective non-adhesive colloid may be added after the emulsification has been completed.

The foregoing description refers to a batch process for producing this dispersion, but I have found-where large quantities are required, that it ismost desirable to effect its manufacture as a continuous operation. For this purpose, I may provide a mixer or dispersing apparatus provided with blades mounted upon a rapidly revolving shaft. In an initial stage of producing the dispersion, this apparatus may be charged with the aqueous suspension or with finished product as before described for batch operation. The agitating blades are so disposed as to cause a rapid incorporation of liquids introduced at the top of the vessel with the bulk contents of the container.

After the. initial charge of suspension or dispersion has been prepared of the desired viscosity, asphalt in a heated liquid condition may be fed into the masspreferably as it circulates downward. Simultaneously there may be fed a thin aqueous suspension of the emulsifying agent in regulated and predetermined proportions corresponding to the proportions desired in the final dispersed composition. F or example, the aqueous suspen: sion may be made up in proportion of one part more or less by weight, of clay and four parts more or less by weight, of water. This suspension may be fed to the dispersing apparatus as previously described continuously and in predetermined quantities and simultaneously with the introduction of asphalt in like regulated quantities. By regulation of the volume of the incoming streams of asphalt and suspended' dispersing agent and by continuous withdrawal o f the finished product from the system a dispersed composition of the character above described will be produced. Where bentonite is used in whole or in part, a corresponding reduction can be made in the concentration of solids in the aqueous dispersion media.

In the production of dispersions by the continuous method, it is important to maintain substantially similar conditions of viscosity in the circulating mass of finished and surplus dispersion always contained in the system. The retention of this quantity of surplus dispersion in the system acts as a balance wheel against minor variations of vis cosity and temperature due to momentary introduction of excess of either asphalt or clay suspension. It will be evident that on account of such minor variations and the necessity for maintaining nearly constant conditions of proportions, temperature and viscosity, it-is advanta cons to maintain as large a bulk supply of finished dispersion in the system as is compatible with the rate of introduction of incoming ingredients and the Withdrawal of the finished product from the mixer.

The product of this continuous operation is in all respects'the same as that produced by batch operation previously described. As taken from the mixer, it is of viscid consistency but not so stiff as to prevent its ready egress from the orifice provided for its withdrawal. I

' The finished'dispersion may be withdrawn continuously from'the dispersing apparatus,

brought to the desired consistency and then transferred to suitable. receptacles for storage or delivery.

While the product produced by either of the methods above described, will be sufiiciently stable toward electrolytes, that is, it will not be broken down by substantial quantities thereof, and is, moreover, resistant to mechanical friction and similar agencies, and will in addition possess a sufiicient degree of suspensibility for certain purposes, nevertheless, l have found that I can produce a dispersion which. will to all intents and purposes be capable of remaining in suspension for an indefinite length of time so that the same may be stored or transported for long periods, without any fear that the dispersions will settle out before being put to its intended use.

In one embodiment of the invention, I may employ as the dispersing agent such material as bentonite, either alone, or admixed with other agents such as clays, or clay-like substances, as heretofore referred to. When admixing the bentonite with other agents, the proportions of the former may vary from 10% to more or less, on the basis of weight of the combined mixture,

1f the dispersing action is carried outwith bentonite or bentonite-like material in proper proportions and under suitably controlled temperature conditions, as above described, it will be found that larger quantities of asphalt or other basecan be dispersed with a given quantity of dispersing media, and with a much finer degree of dispersion than is attainable with clays, and that, in addition where sufficient quantities of bentonite are employed, the resultant dispersion will not settle out but Will remain substantially permanently in suspension.

This material may, therefore, be said to exercise a double function in that, in addition to serving as a very effective agent in increasing the dispersive properties of the media during the operation, it exerts, in the final product, the efiect of a positive suspending agent. In some instances, it may be desirable to take advantage of this last named function of bentonite without employing it in the capacity of a dispersing agent, and in such icases,'therefore, the dispersion may first be prepared in any desirable manner with a suitable dispersing agent and the resulting dispersion may then be treated with bentonite as a protective colloid to improve the qualities of suspensibility of said dispersion. Ins such case, bentonite may be added to the dispersion in proportions approximately one: half percent or more, by weight of the latter. a

As another illustration, I have found it possible to produce a product of the character described by dispersing asphalt with a mixture of caseln and a clay, such as New Jersey ball clay, which alone, would ordinarily produce a relatively non-suspensible dispersion.

In this procedure, a small amount of ammonium hydroxide or sodium borate is added to-the casein either before or after its admixture with the selected clay, so that the casein will assume a swollen, spongy-like condition, and the mass may then' be employed as the dispersing agentin quantities such that the' may in certain cases produce a relatively nonsuspensible dispersion and then treat the same with a protective colloid capable of increasing the suspensibility of the product or of rendering suspensible the relatively non-suspensible product. Thus, for example, I may first produce the dispersion with a clay such as New Jersey ball clay and then add to the dispersed mass a sufficient quantity of gelatin or tannic acid to thereby im prove the suspensibility of the product.

or a dispersion made with the aforenamed 'clay as the dispersing agent, about 1.5% of gelatin or 1% tannic acid, more or less, by

- Weight on the basis of the dispersion is generally sufficient to produce the suspensibility and body normally required in a product of this type.

As before stated, the product as it issues from the dispersing apparatus is of a viscid consistency, and while the fluidity thereof may be increased by the addition of water,

I prefer to reduce the viscosity by subjecting the sti1f, pasty product to a rapid beating .or whipping action as disclosed in my issue Patent No. 1,616,904. This'procedure not only eliminates the introduction of large quantities of water with its resultant decrease in the ability of the product to remain in suspension, but it imparts to the finished product a body which is longer than that which characterizes the same product where the reduction in viscosity is attained by dilution with water. This long body as will be understood, is one of the factors contributing to the suspensibility of the finished prod net. I

It is to be noted that while the product as herein described is ca able of remaining subr 'stantially permanent y in suspension, in the absence of electrolytes, the incorporation of such agents may cause a settling of the dis persed particles depending upon the nature and uantit of the electrolyte, it being evident t at di erent electrolytes will cause varying degrees of settling. At all events however, the relation of the phases of the product as here produced, is not destroyed, and the dispersion remains unbroken even though fiocculated in the presence of practically unlimited quantities of electrolytes.

If the proper type of dispersive media is employed, the dried film will posse a gel structure and will be. unaffected by ieat so that it will not flow at temperatures even one hundred degrees or more, in excess of the melting point of the asphalt dispersed. The

addition of bentonite in regulated quantities to the system, will insure this result with any clay or mineral powder-type of dispersive medium.

In referring to the suspensibility of dispersions of the type here described, it is apparent that any one of a number of standards by which to measure the relative suspensibility or non-suspensibility of these products, may suggest itself. Obviously, where a product of this nature is not at all suspensible, no severe test is necessary, for by merely setting a quantity thereof aside in a suitable vessel and permitting it to remain in a quiescent state for a period varying from two hours to ten days or so, the defect will generally exhibit itself, and be ascertainable by a simple examination, when it will be found that the dispersed particles have set-- tled and packed in the bottom of the containing receptacle, and that a large portion of the water has risen to the upper part of.

the vessel. The dispersions as producedby my present invention are, however, adapted to remain substantially permanently in suspension so that they may be safely shipped or stored over long periods of time, and accordingly they should withstandtests much more severe than the one outlined above. As one form of test which Ihave adopted as a convenient and rapid laboratory method, I use a centrifuge apparatus, in which ,glass tubes about one inch internal diameter and four inches in length are filled with about c. c. of the dispersion and rotated for, say, 15 minutes at a speed of from 2100 to 2200 R. P. M., the lever arm of the rotating tubes being about 6 inches. For a product such as contemplated by the, present invention, the foregoing test should show no perceptible .degree of settling of the dispersion, nor the presence of any substantial water layer upon the surface-of the test sample.

Manifestly, other tests, than the one described may be adopted, but whatever the standard may be, it should be capable of revealing whether or not in practical operation a given product will remain in sus ension over indefinite periods of time, wit out any noticeable settling out of the dispersed particles.

By the term the claims it is intended to comprehend such centrifugal action as used ire lent to that set forth herein. d

action as will exert a settling influence upon the dispersed particles substantially equiva I claim as my invention: 1. A dispersion of fluid consistency'of a bitumen-pitch-type base, solid or semi-solid ;at atmospheric temperatures and normally immiscible with water,comprising water as I the continuous phase, a dispersing-agent, and

finely divided particlesof the base as the dispersed phase, the particles of said base being of such size relative to the viscosity of the dispersion that the finely divided particles of the base remain in suspension when subjected to centrifugal action, the dispersing agent being of such degree of inertness to electrolytes that the dispersion remains unbroken in the presence of substantial quantities thereof, and of such character and amount as to produce in the dried product an irreversiblefilm.

2, A dispersion of fluid consistency of a bitumen-pitch-type base, solid or semi-solid at atmospheric temperatures and normally immiscible with water, comprising water as the continuous phase, a dispersing agent and finely divided particles of the base as the dispersed phase, said particles being of an' average size not substantially greater than ten mu, and some of the particles'approaching colloidal dimensions, the viscosity of the dispersion being such in relation to said size of the particles that said particles of the base remain in suspension when subjected to centritugal action, the dispersion agent being of such degree of inertnessto electrolytes that the dispersion remains unbroken in thepresence of substantial quantities thereof, and of such character and amount as toproduce in the dried product an irreversible film.

3. A dispersion of fluid consistency, of a bitumen-pitch-type base, solid or semi-solid at atmospheric temperatures and normally immiscible withwater, comprising Water as the continuous phase, bentonite-like material as'the dispersing agent, andfinely divided particles of the base as the dispersed phase, the particles of the base being of an average size not substantially greater than ten mu, and some of the particles approaching colloidal dimensions, the viscosity of the dispersion being such in'relation to said size of the particles that said particles of the base remain in suspension when subjected to centrifugal action, the dispersing agent being of such degree of inertness to electrolytes that the dispersion at atmospheric temperatures and normally immiscible with water, comprising water as the continuous phase, a-dispersing agent, and finely divided particles of the'base as the dispersed phase, the particles of said base being of an average size not substantially greater than ten mu, and some of the particles approaching colloidal dimensions, the viscosity of the dispersion bein such in relation to said size of the particles that the particles of the base remain in suspension when subjected to a centrifugal action, the dispersing agent being of such degree ofinertness to electrolytes that "as the dispersed-phase, the particles of said base being of such size relative to the viscosity of the dispersion that the finely divided particles of the baseremain in suspension when subjected to centrifugal action, the bentonite dispersing agent being of such degree of inertness to electrolytes that the dis persion remains unbroken in the presence of substantial quantities thereof, and of such character and amount as to produce in the dried product an irreversible film.

In testimony whereof I aflix my signature.

LESTER KIRSGHBRAUN remains unbroken inthe presence of substan- 4 tial quantities thereof, the dispersion comprising in excess-of five parts of dispersed phase to one part of the dispersing agent, and being capable of drying to a film characterizedby ability to resist'heat up to the temperititure of decomposition of the base without 4. The. dispersion of fluid consistencyof abitumen-pitc'h-type base, solid or semi-solid