US2392813A - Asphaltic compound - Google Patents

Description

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ASPHALTIC COWQUND No Drawing. Application January 22, 1942, Serial No. 427,818

4 Claims.

This invention relates to the preparation of an asphaltic compound and more particularly to the product and the preparation of an air-blown petroleum asphaltic compound especially adapted for use as a saturant for imp ti fe ted or woven fabrics to form prepared roofing material, or as a coating for surfacing saturated or other fabrics and also for cementing together two or more layers thereof.

Blown petroleum asphalts are manufactured from residual oils derived from asphaltic, semiasphaltic or non-asphaltic petroleums by blowing with air at elevated temperatures. These residual oils are generally termed charging stock" and will be so referred to herein. The air may either be blown through a still under pressure, or else sucked through the till by subjecting its contents to a partial vacuum (up to approximately twenty inches of mercury).

The more asphaltic the crude from which the residual oil was derived, the better will be the quality of the blown product and the shorter the duration of the blowing process. The amount of heat used and the time of blowing will depend upon the nature of the charging stock and upon the specifications desired for the finished product.

Among the more important specifications to which the finished product is subject are those for ductility and penetration. These specifications indicate the ability of the material to retain its elasticity. Tests for ductility and for penetration are conducted at both high and low temperatures and it is extremely desirable that the results at both high and low temperatures be as close together as possible.

An object of this invention is to obtain a finished product from the charging stock which will have ductility characteristics determined by test at high and low temperatures which are more nearly identical than is possible of attainment with a product obtained in the usual manner. It has been found that the penetration characteristic of a product obtained in the manner to be described hereinafter is also substantially improved in many, if not all, cases.

I have found that intimately mixing with blown asphalt a relatively small proportion of oxidized drying or semi-drying oil, such as soya bean or linseed oil, improves substantially the ductility of the product and, to a lesser degree, its penetration characteristic. These improved characteristics are believed to be due to a physical mixture of the two substances rather than to any chemical reaction between the two, although it proximity, the invention will be described in greater detail with specific reference to that particular drying oil. However, as stated, linseed oil has been found to produce equally satisfactory results and it is believed that this is true of most, if not all, of the so-called drying and semi-drying oils. Soya bean 011 if oxidized, either by exposure to the air at normal temperature or by accelerated oxidation through use of an air stream at normal or elevated temperatures, forms a very dense elastic mass similar in its physical characteristics to soft rubber. This oxidized material is quite tough and elastic, 0r ductile. When th asphalt and oxidized oil are intimately mixed, the latter imparts to the asphalt some of its elasticity, causing a substantial increase in its duetility.

However, I have found it difficult to mix the rubbery oxidized oil with the asphalt to obtain a mixture sufiiciently intimate to provide the desired optimum results. Thorough mixture of the oxidized oil and the asphalt requires extreme temperatures and this tends to have an undesirable effect on the asphalt itself. In order to obtain the desired intimate mixture without affect- "ing the asphalt in any harmful way, yet atthe same time obtain the maximum of advantageous results contemplated, the oil in its raw state is mixed with the charging stock before blowing. In its raw state the oil is a thin liquid and the mixture may be accomplished in any way that is most convenient. A preferred procedure is to add the oil to the charging stock as the latter is being run into the blowing still. The turbulent action in the still during the blowing thoroughly mixes the oil and asphalt.

Blowing is then continued just as it would be without the oil and both the asphalt and the oil thus intimately mixed therewith are oxidized simultaneously. The temperature and duration of blowing will vary, depending upon the type of crude from which the charging stock was derived and the desired characteristics of the finished product. The temperature may range from 300 to 600 F. and the duration of blowing from five to eighteen hours. Normally the temperature is held in the neighborhood of 400 F. and the blowing time is about eight hours. However, as already stated, this may vary greatly, depending on the results desired.

It has been found that, when carrying out the process described on charging stock derived from East Texas crude oil, the ductility characteristic oi the product is approximately.18% better than that characteristic of a product obtained by carrying out the same procedure with the same charging stock but omitting the addition 01 oil in the manner heretofore described. While the comparative results obtained were based on the use of charging stock obtained from so-called East Texas crude, the improved process is equally applicable to charging stock derived from any naphthenic, asphaltic or mixed base crude.

As with the temperature and duration of blowing, theamount of oil added to the asphalt may vary in accordance with the nature of the charging stock and in accordance with the particular characteristics desired for the finished product. However, I have found that the addition of from 1% to 10% of the oil covers a wide range of such variable factors and that the more intimate the mixture ,of oxidized oil and asphalt, the more marked is the improvement in ductility and penetration characteristics.

While I have described herein an improved asphaltic compound having certain desirable characteristics, together with a preferred method of obtaining the same, it should be understood that other procedures for performing the same steps and accomplishing the same objectives may be apparent to those skilled in the art, and for that reason the invention should be limited only within the scope of the appended claims.

What I claim is:

1. That method of producing in a blowing still an asphaltic compound adapted for use as a roofing material and possessing relatively constant ductility characteristics throughout the range of normal Weather temperatures which includes the steps of adding from 1-10% raw oil of the group consisting of drying and semi-drying oils to a suitable petroleum residual oil as the latter is introduced into the still, and subjecting the still contents to a temperature oi between 300 F. and 600 F. while simultaneously directing a current of air .through the still contents for a period of between five and eighteen hours.

2. That method of producing an asphaltic composition adapted for use as a roofing compound and possessing relatively constant ductility characteristics throughout the range of normal weather temperatures which comprises the steps of intimately mixing from 1-10% of a raw n of the group consisting of drying and semi-drying oils with a suitable petroleum residual oil, and subjecting the mixture to a temperature varying between 300 F. and 600 F. while simultaneously directing a current of air therethrough for a period varying between five and eighteen hours.

3. An asphaltic composition adapted for use as a roofing compound and possessing relatively constant ductility characteristics throughout the range of normal weather temperatures, said compound comprislng an intimate mixture of a suitable petroleum residual oil and from l-10% of a raw oil of the group consisting of drying and semi-drying oils, said intimate mixture having been subjected for a period varying between five and eighteen hours to a temperature of between 300 F. and 600 F. while being simultaneously subjected to a current of air directed therethrough.

4. That method of producing in a blowing still an asphaltic compound adapted for use as a roofing material and possessing relatively constant ductility characteristics throughout the range of normal weather temperatures which comprises the steps of adding from 1-10% raw oil of the group consisting of drying and semi-drying oils to a suitable petroleum residual oil as the latter is introduced into the still, and subjecting the still contents to a temperature of approximately 400 F. while simultaneously directing a current ofair therethrough for a period approximating eight hours.

ALEXANDER G. FEWSMITH.