US2080690A - Filled asphalt and method for producing same - Google Patents

Description

Patented May 18, 1937 UNlTED STATES FILLED ASPHALT AND METHOD FOR PRODUCING SAME Ulric B. Bray, Palos Verdes Estates, and Lawton B. Beckwith, San Pedro, Calif., assignors to Union Oil Company of California, Los Angeles, Calif., a corporation of California No Drawing. Application April 30, 1934, Serial No. 723,166

8 Claims.

The present invention relates to a filled asphalt and to a method for producing the same. More particularly, it relates to an asphalt in which a finely divided mineral filler, such as diatomaceous earth, has been incorporated and which is particularly adapted to be used for Water proofing metallic surfaces such as for coating pipes or other metallic materials, for roofing purposes and as adhesive or binding material of high tensile strength in breakwater and revetment construction.

It is an object of our invention to provide a method for incorporating finely divided mineral fillers such as diatomaceous earth into bituminous substances such as asphalt to produce what is known as a filled asphalt.

It is another object of our invention to produce filled asphalts having greatly improved surface appearances over filled asphalts heretofore produced. Another object is to produce a filled asphalt having a smooth, glossy surface and which has a high density and the least possible porosity and therefore a minimum tendency to absorb water over filled asphalts heretofore produced.

Another object of our invention resides in producing filled asphalts which are particularly adapted to be used for coating pipes or other metal surfaces, to provide a water proofing coating on roofs, to fill the voids presented by irregularly disposed rocks in breakwater construction and which may be employed as the binding agent for aggregate in revetment construction. Pipes may be coated with the asphalt composition either by dipping the pipe in a bath of the asphalt composition which is maintained at a temperature above its melting point, or the asphalt composition may be sprayed onto the pipe or it may be applied by means of a brush. Such methods are well known to those skilled in this art and need not be described herein in detail.

Various other objects and features of our invention will be apparent to those skilled in the art from the following description of our product and from the method for incorporating finely divided mineral fillers into asphalt or other bituminous materials.

Stated broadly, our invention resides in a process for incorporating finely divided mineral fillers, specifically diatomaceous earth, into asphalt or other bituminous materials which comprises mixing melted bitumen with a finely divided mineral filler and in removing substantially all moisture and air from the mixture.

As a feature of the invention, we prefer to accomplish the removal of substantially all air and moisture from the mixture by subjecting the mixture to steam agitation for a period of time sufiicient to accomplish the desired results;

More specifically, our method for incorporating finely divided mineral fillers into asphalt com: prises in melting the asphalt or bitumen employed, mixing the melted asphalt with a finely divided mineral filler such as diatomaceous earth to produce a rough filled asphalt and subjecting the rough filled asphalt to agitation with steam at a temperature of approximately 400 to 600 F. for a suificient period of time, say 1 to 2 hours, to remove substantially all of the air and moisture from the rough filled asphalt whereby a filled asphalt is produced having a smooth, glossy surface, a high density and a minimum porosity. Our invention also includes the product produced by the aforesaid process.

We have observed that when finely divided mineral fillers are mixed with melted asphalt to produce a filled asphalt by merely mechanically stirring the mineral filler into the asphalt, such as by means of a propeller agitator that the product produced had a rather rough surface and was characterized by many minute bubbles, pin holes and craters. The rough surface apparently resulted from the bursting of air or moisture bubbles on the surface to leave craters. An asphalt of this character is entirely unsuitable for purposes where the material is to be used to protect surfaces against the corrosive action of moisture or water, as, for example, when employed to coat pipe lines. The low density of the filled asphalt which results from the presence of the large number of minute bubbles and pin holes in the asphalt is entirely unsuitable to protect the surface since the material will absorb a considerable amount of water and work through the voids in the asphalt to the metal surface.

We have discovered that if the aforeseaid filled asphalt is subjected in a steam still to a gentle steaming operation, for approximately one hour, that the filled asphalt thus produced will have an improved appearance, and will be characterized by a rather smooth, glossy surface, a high density and a low porosity and thus, a minimum tendency to absorb Water.

It is believed that the steaming operation was responsible for the greatly improved appearance of the surface of the filled asphalt, for the high density, for the less porosity and for the elimination of all bubbles, foaming and sponge formation of the product. Furthermore, it is possible to obtain a more thorough incorporation of the finely divided mineral filler in the asphalt, a more even distribution of the filler in the asphalt and a more complete wetting of the mineral filler by'the asphalt by subjecting the mixture to the steaming operation, than can be accomplished by mechanical agitation alone. In conjunction with the steaming operation which removes moisture and absorbed air from the filler particles, we prefer to also employ a grinding type of agitation for incorporating the filler into the asphalt.

desirable moisture and air from the surface of the filler particles, it facilitates the removal of the moisture and air by steaming.

In the place of using superheated steam (temperature 400 to 600 F.) as the agent to remove moisture and air from the mixture, we may use air, nitrogen, fiue gas, carbon dioxide, CO2, or

During the steam or air-' other inert gases. blowing after incorporation of the filler, the final tests on the mixture can be brought to definite specifications by controlling the air or steamas is well known to those skilled in the art.

From a standpoint of operation, it is preferable to manufacture the filled asphalt in a still to which steam and/or air are accessible so that a closer control over the usual physical properties of the final products, such as melting point, penetration and flash point, may be had. To incorporate the finely divided mineral filler into the asphalt, it is preferable to first melt the charge of asphalt in a shell still to which steam and/or air are accessible. The charge is maintained at a temperature of say 400 to 600 F. Then the desired amount of filler is incorporated into the charge. Preferably, this is accomplished by circulating the contents of the still through an intermediate mixing vessel equipped with propeller agitator in which the filler is introduced continuously and gradually through a hopper. The circulation from the still to the mixer and back to the still is continued until the desired amount of filler has been incorporated into the still charge. 7 A gear pump, Kinner pump or a Waterous pump is used for circulating the rough mixture to and .from the still during the incorporation of-the filler. These pumps are chosen to exert a grinding actionon the roughly dispersed mixture from the propeller agitator. During this time of addition of the filler, steam and/or air is employed in the body of the still and continued after the incorporation of filler is complete until the characteristics of the stillcharge are brought to the required specification limits.

While I have disclosed that diatomaceous earth may be employed to fill the asphalt, it will be observedthat other types of fillers for the asphalt l-may beemployed such as clay, infusorial earths,

Y pact.

;voids in the asphalt and this phenomenon aids in the production of a bituminous composition of a greater tensile strength and resistance to im- The diatomaceous earth which we prefer to use is one of sufiicient lightness as to remain in suspension during the process of incorporation into the asphalt. Diatomaceous earths lighter While efiicient grinding to obtain good distribution of the filler into the asphalt will not remove the-uni than 12 lbs. per cubic foot are suitable. If desired, other finely divided mineral fillers such as those mentioned above may be employed in conjunction with the diatomaceous earth in any desired proportion.

The'percentage of diatomaceous earth or other mineral filler to be incorporated into'the asphalt will depend upon the characteristics of the asphalt or bitumen employed and the uses to which the final product may be put and also upon the characteristics of the mineral filler. However, it is believed that the following specific examples will illustratesome of the various uses of filled asphalt and the characteristics and method for producing the filled asphalt for the purposes employed;

. Example 1 To produce a filled asphalt adapted to be employed in filling the voids in breakwater construction and for revetment lining, a steam blown asphalt having a melting point of approximately F. and a penetration of about 50 at 77 F. and which is produced by distilling'an asphaltic oil such as Poso Creek crude oil until the residue has the above melting point and penetration is placed in a still to which steam and air are accessible and is heated to a temperature of approximately 400 to 600 F. 7 Then acteristics of the still charge are brought to the required specification limits. The filled asphalt thus produced will have a melting point of about F. and a penetration of 20 at 77 F., and may be employed for use in construction of revetments and breakwaters in accordance to the methods disclosed in the copending application by L. R.,Mason, Serial No. 647,849 (Patent No.

1,987,150) and 647,850 (PatentNo. 1,987,151), respectively, filed Dec. 19th, 1932. 7

Example 2 A dipping enamel adapted for coating pipes by dipping the pipe in a vat containing the prod uct to be described is produced by mixing in a steam still an air blown asphalt having a melting point of to 200 F. and a penetration of .20-25 at 77 F. with approximately 11 to 13% by weight of diatomaceous earth. The admixture is effected at a temperature of approximately 450 F. and in the manner disclosed in Example 1. The mixture ot diatomaceous earth and air blown asphalt is then subjected to a gentle steam agitation for approximately one hour. The finished product will then have a melting point of 205 to 215 F. and a penetration of 16 to 22 at 7'l.F.

Example 3 To produce an asphaltic composition which is hard and tough and which is particularly adapted as an outer coating in pipe line protection, we employ an air blown asphalt having a melting point of 215 F. and a penetration of 6 to 10 at 77 F. and incorporate approximately 11 to 15% of diatomaceous earth into the air blown asphalt in the manner disclosed in Example 1, after which the mixture is subjected to gentle agitation for approximately one hour. The product thus produced has a melting point of 235 F. a penetration of 2 to 4 at 77 F. and is characterized by a smooth, glossy appearance, a high density and a low porosity. As stated above, it is particularly adapted as the outer coating of pipe lines where a number of asphaltic coatings are given to the pipe. When applied to pipes, the coating is rigid and has a great resistance to mechanical action of the soil and will not be stretched nor distorted by the mechanical action of drying mud. The coating also has a high electrical resistance, that is, it prevents corrosion of the pipe from electrolysis operating through pin holes or minute air bubbles which are present in filled asphalts which have not been subjected to the steaming operation heretofore described. The coating is also characterized by great beam and tensile strengths so that it will not be cracked or easily punctured. It also is inert to chemical action, particularly the action of alkalies and acids and has a great resistance to wide ranges of temperature. Due to the absence of air bubbles in the filled asphalt and its high density, there is less tendency for the asphalt to absorb water and consequently when filled asphalts, as produced by our method are employed as waterproofing coatings, a structure is presented which efiectively seals off the part to be protected from the corrosive action of the water.

It will be observed that all mention herein of melting point and penetration are according to the methods outlined by the American Society of TestingMaterials as follows:

Penetration Method D-- 525 Melting point (ball and ring) -Method D-3626 It is to be understood that the above description is merely illustrative of preferred embodiments of our invention of which many variations may be made within the scope of the following claims by those skilled in the art without departing from the spirit thereof.

We claim:

1. A method for producing filled asphalt which consists in mixing melted asphalt with a finely divided mineral filler and subjecting said mixture to agitation in an inert gaseous fluid to remove substantially all of the moisture and air present in said mixture.

2. A method as in claim 1 in which the gaseous fluid comprises steam.

3. A method as in claim 1 in which the gaseous fluid comprises air.

4. A method as in claim 1 in which the mixture of asphalt and finely divided mineral filler is subjected to agitation in an inert gaseous fluid at a temperature of 400 to 600 F. for approximately one hour.

5. A method as in claim 1 in which the finely divided mineral filler comprises diatomaceous earth.

6. A method for producing a filled asphalt which comprises melting asphalt, gradually incorporating into said melted asphalt a finely divided mineral filler and during said incorporation of finely divided mineral filler maintaining said asphalt at an elevated temperature until completion of said incorporation and thereafter gently agitating said mixture at an elevated temperature with steam until substantially all of the air and moisture occluded in the mixture is removed whereby a filled asphalt is produced characterized by a smooth glossy surface, a high density and a low porosity.

7. An asphaltic enamel adapted for coating pipes which comprises a mixture of air-blown asphalt having a melting point of approximately 215 F. and a penetration of 6 to 10 at 77 F. and approximately 11 to 15% by weight of a finely divided mineral filler, said mixture having a penetration of 2 to 4 at 77 F. and a melting point of approximately 235 F. and is characterized by a smooth glossy surface, a low porosity and a high density.

8. An asphaltic enamel as in claim '7 in which the finely divided mineral filler comprises diatomaceous earth.

ULRIC B. BRAY. LAWTON B. BECKWITH.