US2053099A - Method of producing bituminous dispersions - Google Patents

Description

are used as the Patented Sept. 1, 1936 PATENT oFFicE METHOD OF PRODUCING BITULIINOUS DISPERSIONS Jack Miscall, Rutherford, N. J., assignor, by mesne assignments, to The Patent and Licensing Corporation, New tion of Massachusetts N Drawing.

York, N. Y., a corpora- Application July 26, 1932,

Serial No. 624,911

8 Claims.

This invention relates to the production of dis persions of thermoplastic materials, and is particularly concerned with the production of soaptype dispersions by means of a colloid mill.

When a colloid mill is in operation, a great amount of air is sucked into the apparatus by reason of the vacuum created within the mill by the rapidly rotating parts. The air enters through the packing glands, bearing surfaces, and through loosely connected joints.

In the production of soap-type dispersions of thermoplastic material such as asphalt in an aqueous medium, the presence of air is detrimental to the success of the operation. The air causes a creaming efiect with the result that a scum, containing a large proportion of poorly dispersed particles of asphalt, is formed. Additionally, when certain soaps, such as rosin soap,

emulsifying agent, a chemical reaction occurs between the soap and the carbon dioxide contained in the air. Rosin is composed chiefly of abietic acids which are weaker than carbonic acid and therefore displaced by the latter. The action of the carbonic acid on the soap is accelerated at elevated temperatures and hence at the temperature at which the emulsion emerges from the colloid mill the reaction proceeds fairly rapidly with the result that rosin is precipitated and the soap destroyed. As long as the soap is present it acts as a protective colloid to maintain the large particles in suspension, but when it is precipitatedthe particles agglomerate into pellets which form a solid asphalt blanket on the emulsion. In addition, the incorporation of air in the ingredients to be emulsified reduces the friction in the mill with the result that dispersion to the required degree is not effected. Furthermore, the incorporation of air greatly increases the volume of the ingredients passing through the milk-sometimes as much as 40%,-- so that the capacity of the mill is materially reduced and the storage facilities must be greatly increased to handle the product.

The object of my invention is to provide means whereby to exclude air from the colloid mill during the emulsifying process.

Another object of my invention is to provide a method of producing soap-type emulsions of difficultly emulsifiable asphalts.

In accordance with my invention the colloid mill is immersed in a viscous liquid bath in order to prevent intake of air. A suitable liquid to be used as a bath is a heavy petroleum oil such as fuel oil or cylinder oil, but any other material that has sufiicient viscosity so that it is not easily sucked into the mill and at the same time is of such nature that it is not injurious to the emulsion when mixed therewith in small quantities, may be used as the bath.

In practicing my invention the materials to be dispersed are run into a colloid mill of the usual type such as a Hurrell mill and subjected to the emulsifying action of the mill. The feed to the mill is entirely closed and the mill itself is immersed in a receptacle filled with viscous oil or 10 other viscous material, to a sufiicient depth so that air cannot enter through the packing glands, bearing surfaces or through joints which ordinarily allow air to filter through. The dispersion then passes from the mill to a receptacle where it may be tested and if found suitable, it is pumped to a storage tank, If the emulsion is unsatisfactory it may be recycled through the mill.

I have found that by using an oil bath for the olloid mill it is possible to satisfactorily emulsify certain types of asphalt which it has heretofore been difiicult or impossible to emulsify in the mill which was exposed to the air, or which produced poor emulsions when so emulsifled. Not only has the quality of the dispersion been greatly improved but the volume of the emulsion has also been reduced more than below that which is obtained when operating with the mill exposed to the air. 30

To illustrate my invention an emulsion was prepared with a Mexican type asphalt having the following specifications:

Specific gravity 1.01 to 1.03 Softening point (B. a R.) 102 to 109 F. Penetration (100 gr., 5 sec., 77 F.) 180 to 210 Ductility (77 F.) 100 Flash point Over 450 F. Solubility in carbon bisulphide 99.8%

The asphalt was heated to 230F. and proportioned through a colloid mill submerged in an oil bath, together with a rosin soap solution containing 25% excess potassium hydroxide over the amount necessary for saponification. The soap solution was heated to F. The outlet temperature of the emulsion ranged between F. and F. The resulting emulsion contained 2.5% of soap and 42.5% of water. The emulsion was passed through a 28 mesh screen and showed 50 a screen deposit of only 016%. No scum was formed on the emulsion. An examination of the particles showed that none greater than 16 mu in size were present, while 70% were 4 mu or less 55 1 due to the character of the asphalt. I

showed 11.8% greater The same asphalt heated to 240 F. was proportioned through a colloid mill, which was exposed to the air, together with a rosin soap solution containing 22% excess potassium hydroxide. The emulsion issued from the outlet of the mill at a temperature ranging between 170 F;- and 180 The watercontent was-43%and the proportion of soap present was 2.2%.. The emulsion contained 25% to 35% of air by volume, gaveiai very high screen deposit, and formed. 2.2% .ofv scum. An examination of" "the particle size than 16 mu and 58% of 4muorless.

The emulsion prepared byusling 'th'e oil immers'ed mill contained abodt"% of air by volume, the source of which is not certain. However, the small amount of air present did-not ma.-,;.. "terially impair the quality of the emulsion.

With other types'of asphalt than effect of aeration is much more serious." With certain asphalts derived from Mid-Continent or Texasoils of semi-asphaltic nature,z-.far greater liability to foaming or aeration is encountered. Apparently the surface tension relationship-s of such asphalts vary .greatly and-a m0repermanentfoam'may result fromaeration in themill With certain asphalts derivedf om such oils andhaving the same general melting point, pene- 3D.

tration, and ductility characteristics as the Mexican asphalt referr'ed to, the'aeration-is; so severe 'that it becomes.practicallyimpossible to make "a satisfactory emulsion atall in the ordinary inches thick on an; ordinary '55 gallon barrel and 7 completely is aipasty,foamy mixture of air bubbles, aqueous phase, and agglomerated particles of asphalt, all in a condition which will;not readily-disperse into the better part ofthe. emulsion, orifredistributed, re-collects- Thisjfoamy ,material breaksdown within; a short time and the emulsion contained in this is, from a practical standinpt'unusabla, Q V

It is difilcult to determine exactly why, under such conditions and with specific .asphalts of this kind, the effect of aeratiorijshouldfbe so seriously destructive; One reasonable explanatiomho wever, does reside in the fact that with .asphalts having low surface tension relationship to air the foam produced inthe severe action of the mill is quite permanent. The air bubbles which are .surrounded by the aqueousphasefitwith its the asphalt, is this .kin d, it. will be seen that any preferential dispersed asphalt) being relatively permanent, may have the property of concentrating, on the surface or at the interface, by preferential adsorption, the soap which normally would be distributable about the asphalt particles. It is well knownthat'in thefinterfa'cial films of dispersions of this kind there is a concentration of the emulsifying media. Inasmuch as the air, as well as the dispersed phase in a system of :rladsor-ption of the'emulsifying agent at the airwater interface would result in diminishing the -stability of the dispersed asphalt while increasing the stability of the; foam. The chemical effect 0f; the carbon dioxide in the aerated emulsion uphereinabove described, doubtless onthe soap, as also contributes to the harmful results that en- =sue'when emulsification is accompanied by aera- Mexican, the

tionand the formation of foam. In running the sameMid CQntinent asphalt as referred to above in 'the mill, in which the feed is closed and in which'the glands are" sealed in a bath of oil, this aeration is practicallyieliminated and the emergent emulsion issub'stantially free from foam or scum formation, being of normal particle size and free from coarse particles which. produce screen residues, andv is in everyrespect commercially usable. i f

.I claim as my invention:

1. The process of' emulsifying asphalt which comprises ipassingthe molten asphalt through a colloid millutogether with water and dispersing agent whilesaid colloid mill is immersed in a liquid bath. 3 I a 2. .Theprocessof emulsifying asphalt which comprises passing molten asphalt together with water and..a dispersing agent through a colloid mill and preventing aeration during the emulsification,.;by thefl actiongof asliquid seal around the bearings of. the mill; -i 3..ln; the process of producing 'soap type asphalt emulsions by colloid mill actions the step whichjcomprises producing the emulsion in the substantial-absence 0f--air by theagency of a liquid-seal, around thebearings-of the colloid mill.

4. The process iof producing soap type asphalt .emulsions'which: comprises passing asphalt in liquidv state {together with water and a. soaplike,..dispersin'gagentthrough a colloid mill while saidm-ill. is immersedin a. liquid bath.

5.. Process in-accordance with claim 4 in which the bathcomprisespa viscous oil.

6. Inthe production of asphalt emulsions by means of a colloid mill,lthe step .of preventing access of air tosaid mill .byimmersing the mill in a liquid bath. L

'7. -Method according to claim 6 in which the bath is composed of a viscous liquid.

8. Method according to claim 6 in which the liquid .bathis aheavy hydrocarbon oil.

- JACK MISCALL.