US1981522A - Dispersion of mineral matter - Google Patents

Description

Patented Nov; 20,

DISPERSION or mar-41m MATTER Oscar Frederick Nitzke, Belmont, Mass.

No Drawing. Application March 18, 1932,

- l Serial No. 599,850

scams. (01. 134-1) This invention relates to the production of dispersions of thermo-plas'tic hydrocarbon materials, such as petroleum asphalt, mineral asphalt and the like, in an aqueous medium.

The main purpose of the invention relates to the production of dispersions of asphaltic material in an aqueous medium, which, dispersion will be of relative high stability and which may be diluted sufficiently with water to have high penetration qualities, e. g., when applied in penetration type of road" work.

It is of importance in emulsions'of the type disclosed that the saponifiable material employed can be readily obtained 'in' quantity and at a fair price in this country and that the material Will'not unduly detract from the quality of the asphalt after the emulsion has been applied a Q It has been found that vegetable pitches, such as stearin pitch, whichfis a fatty'acid pitch constituting the still residi'um' resulting from the distillation and" purificationof vegetable oils, such .as cottonseed oil, can be used to furnish the" pr'otectiVeCdlloid or stabilizer in emulsions of mineral asphalts and pitches. This residuum is available at cottonseed oil refineries, for example, substantially as a waste product, since it has only limited applications commercially, due to its relatively poor weathering qualities when used alone. As available on the market the preferred form has a dark pitch-like body having approximately the following characteristics,- specific gravity of 1.01, melting. point of 100 F. to 153 F. (Ball and Ring),-an acid numberGO,

and a low unsaponifiable content, some .examples being as low as approximately 5% to 8%. This material, known as stearin pitch in commerce, is completely miscible in any proportion with mineral asphalts, e. g; those derived from the distillation of crude petroleum.

In forming the emulsion, the asphalt and vegetable pitch are brought to a temperature sufficiently high to liquefy them and they are completely mixed as by being boiled with steam or by having air passed upwardly through the same to produce a homogeneous mixture of the mineral asphalt and vegetable pitch.

Since there is no tendency in the mixed materials to separate out on solidification, the mixed materials may be permitted to return to a solid state thereafter and then reheated to a fluid state, at the time of the formation of the dispersions. The dispersion may, however, be formed .,while the materials are heated, as soon as they have been mixed, and without permitting them to cool.

The dispersion is formed by introducing the melt, comprising the asphalt and vegetable pitch, with agitation into a body' of water con taining a small quantity of caustic soda or other alkali capable of serving as a saponifying agent for the saponifiable content of the melt. Thef caustic soda ih solution apparently reacts with such free fatty acidor fatty acid glycerides'as are present in -the stearin pitch to generate soaps insitu' throughout the heat liquefied mix-i ture, these soaps serving to stabilize the parsc'les of bitumen reduced to small part'icle size by thea gitation when the melt is introduced-into the aqueous medium. In the present instance,- in addition to the'br'eaking up of the' materials into microscopic particles in the aqueous medium by the agitation which accompanies mixing the particles, I believe there is also a leaching out of the soluble soap produced inthe mass with the resultant release of fine particles of re leased bitumen broken up by thele'aching ac can. I'n'anyevent I have foundthat the pa r'ti ole size of the resulting dispersion is very small.

While difierent vegetable pitches differ considerably in their characteristics, it has been found that usually there is about 15% to 40% or higher by weight of the material which is saponifiable and which may be converted into soap functioning to stabilize the dispersion. In practice it is desirable to use as large a proportion of asphalt as possible inthe' procurement of a stable dispersion. This is true because of the fact that as a rule asphalts are far more stable when subjected to weathering than the vegetable pitches and most other stabilizing agents. If too small an amount of the vegetable pitch is used, there results a dispersion in which the particles tend to separate out and coalesce so that the dispersion does not have the necessary stability, for example, for storage or transportation thereof.

It has been found that about 2 of stearin pitch based on the weight of the mineral asphalt 10c, dispersed affords a dispersion of relatively poor stability, even though the materials are thoroughly saponified. As the ratio of the stearin sions containing from 2 to 10% by weight, based on the mineral asphalt, provides a sufiicient range of stability in the final product for all usual purposes. The products formed within this range have sufficiently satisfactory bonding and weathering qualities for most purposes and particularly for road building and maintenance work.

Within the above range an emulsion formed with 5% stearin pitch, based on the quantity of mineral asphalt employed, affords a highly stable emulsion of excellent weather-proofing qualities and the finished product can be diluted with water to as low as 50% to 60% solids content without any marked tendency to coalescence or settling out of the particles. An emulsion of this type can readily be mixed with road building materials, such as sand and crushed stone, and when applied to the roadway the asphalt is found to have the bonding qualities required for this type of work.

The following is an example of the formation and use of the emulsion for road building purposes. A mixture of parts of mineral asphalt of approximately F. melting point and 150- 200 penetration value is melted and thoroughly mixed with 5 parts of vegetable pitch, the mixture being heated to approximately 300 F. The melt so prepared is then mixed with an equal volume of to /2% alkali metal hydroxide or carbonate water solution heated to F. to F., forming an emulsion of 50% solids content with a temperature of approximately 195 F. The water content may be as low as 30% of the final dispersion. The particles of an emulsion so formed are uniformly small, being ap roximately one ten-thousandths of an inch in diameter.

The emulsion disclosed herein is particularly useful for penetration type of road work, wherein the materials are laid in place and the asphalt poured over, into and through the crushed stone and other materials. The emulsion has a propconditions, but in general the emulsion disclosed herein will break within about two hours after it has been applied.

While the examples given have been relatively specific as required by the statutes for a complete disclosure of the invention, it will be understood that they are intended as examples only, and that the invention is to be limited only as set forthin the appended claims.

What I claim is:

1. The process of forming an aqueous dispersion of asphalt comprising intimately mixing therewith from. 2% to 5% of stearin pitch having a relatively high saponification value and thereafter dispersing said mixture, while heated, in a dilute aqueous solution of a non-stabilizing alkali, and forming through the reaction of said pitch and alkali reaction products constituting I.

the essential stabilizing elements of the dispersion.

2. A dispersion whose solids content consists of from 95% to 98% mineral asphalt and from 2% to 5% stearin pitch, of the nature of cotton seed oil foots pitch, dispersed in an alkaline aqueous medium, the alkalinity of which is supplied by less than 1%, based on the water content, of a substantially non-stabilizing alkali of the nature of caustic soda, the dispersion being IL),-

stabilized essentially by the reaction products of said pitch and said alkali.

OSCAR FREDERICK NEITZKE.