US2375117A - Asphaltic compound - Google Patents

Description

Patented May 1, 1945 ASPHALTIC COMPOUND Alfred Lentz, Maywood, Calif., assignor to Richfield Oil Corporation, Los Angeles, Calif., a corporation of Delaware No Drawing. Application December 16, 1941,

Serial No. 423,186

. 2 Claims.- (cries-152) This invention relates to the treatment of bituminous materials uch as' asphalt. It relates more particularly to the preparation therefrom of improved coatins.,impregnating, binding or adhesive material useful in the manufacture of roofing paper, shingles, paving, flooring and the like. The invention includes the resulting asphaltic material having improved penetration-softening point relationship and weathering properties.

The terms asphalt or "asphaltic material as used herein are intended to mean a normally solid or semi-solid residual material of petroleum or coal tar origin.

One of the primary problems in the manufacture of this type of material for the purposes stated is the control of the penetration and softening point relationship of the product. This relationship to a considerable extent determines the serviceability of the product for a particular purpose.

The penetration value of asphaltic materials is a measure of its hardness under approximately normal temperature conditions. Its softening point is the temperature at which the material loses its solid characteristics and becomes relatively fiuid.

It is to be understood that the term "softening point, and values with respect thereto given herein, have refrenceto the standard ball and ring method for determining the softening point of asphaltic material prescribed b the American Society of Testing Materials. Also penetration values appearing herein are as determined by the standard method prescribed by the American Society of Testing Materials for determining the hardness of asphalt and the like, the temperature used in the penetration tests being 77 F. (25 C.)

For some purposes it is desirable that the asphalt have a relatively high softening point so that it is not greatlyaffected by moderate temperature changes. For these same purposes it is frequently desirable that the material not be hard and brittle at such moderate temperatures; in other words, that its penetration value. be relatively high.

The establishing of the desired relationship between softening point and penetration has been a major, difficulty in the manufacture of such materials and this difiiculty has usually been met by a compromise. The fact that the penetrationsoftening point relationship has been more or less fixed has prevented wider use of these-materials in the manufacture of finished articles of commerce.

Prior to the present invention attempts have been made to control the penetration-softening point relationship by oxidation, dry or steam di tillation, the addition of inert fillers or a combination of these devices.

By prolonged air blowing the penetration-softening point relationship has been somewhat improved. However, the weathering quality of the materials is influenced to a great extent by the severity of oxidation and such prolonged air blowing has had an adverse effect upon the useful life of the product. Likewise, neither distillation nor the addition of inert fillers has produced wholly satisfactory results.

I have discovered that asphaltic materials having greatly improved penetration-softening point relationship may be prepared by incorporating therein a relatively sm"ll proportion of boric acid. In addition to the improved penetration-softening point relationship, the resulting asphaltic material has superior weathering properties.

While I cannot state with certainty the reason for these improved results, it is my present belief that the boric acid reacts chemically with the asphaltic material. This belief is based upon the following observations:

g 1. The effect of the addition of the boric acid on the asphalt product is 'much greater than that where an equivalent amount of inert filler such as clay is added;

2. The proportion of insolubles in the asphaltic material to which the boric acid has been added is not greater than that of the asphaltic material not so treated: and

. 3. The boric acid is not recoverable from the asphalt by leaching.

The optimum amount of boric acid to be added to the asphalt in accordanc with my invention will vary somewhat depending upon the characteristics of the particular asphalt used and of the desiredcharacteristics of the resulting product. Beneficial results have been obtained by the addition of an amount of boric acid as small as 0.25% by weight. Proportions up to and even in excess of 3% may be used with advantage. Usually about 1% is suflicient for satisfactory results.

It is frequently desirable, though not essentialto the present invention, to partially oxidize the asphalt, for instance bylimited air blowing, before adding the boric acid.- The boric acid is preferably added to the asphalt while the latter is in a highly heated fluid condition, for instance at a temperature of about 350 F., and thoroughly dispersed therein by agitation.

The invention will be further described and illustrated by the following specific examples of the method employed in the preparation of the product using as a base material an asphalt from a heavy West Coast crude known as "Gato crude."

Asphalt obtained from this crude, is normally readily oxidized by air blowing and makesahigh gradematerial for roofing. shingles or other prod.- ucts where oxidized asphalt is used.

The crude petroleum is first distilled until the residue therefrom has a Saybolt Furol viscosity of approximately 450 seconds at 210 F. The residue from this distillation may,;then..-be blended.

jresulting product has therefore been unsuitable 210 F. This blend is then partially oxidized by blowing with air or a mixture of air and steam until a softening point of about"200 F;,by the ball and ring" method is obtained The tem perature of the blend is then adjusted to about 360 F. and the borlc acid added and thoroughly admixed therewith.

'As previously stated, the proportion of boric acid to be added may vary over a considerable range. The results obtained by adding to the particular asphalt just identified various proportions of boric acid ranging from 0.25% to 3.0% by weight are recorded in the following table. For comparison, the pentrations and softening points of the identical asphalt without the addition of boric acid are also included.

Still larger proportions of boric acid may be added with advantage, where-desirable. It will be observed that as the softening point increases the penetration decreases somewhat. However, the relationship of penetration to softening point is much more favorable than is obtainable by oxidation alone. Also, the product of this invention has the added advantage of superior resistance to weathering.

By a favorable choice of asphalt and the addition of an optimum proportion of boric acid, asphalt products have been prepared in accordance with the present invention having softening points in excess of 450 F. and with superior resistance to oxidation in a standard weatherometer apparatus. The resistance of such products to weathering has been found in some cases to be over twice that of the unborated product. For example, one'such product was found to show a life of 130 cycles as compared to a life of 63,

tical conditions. The softening point of coating asphalts, normally about 215 F., may readily be raised to ashigh as 300 F., in accordance with this invention. Furthermore, this increase in softening point is effected with a much smaller decrease in penetration than hasheretofore been obtainable tomy knowledge by distillation or oxidation alone. The product has the added advantage of superior weathering properties. It has heretofore been known that the softening point'of .asph'alts could be increased within limits by incorporating therewith relatively large proportions ofinert fillers. However, such increase-in softeningpoint has been accompanied by a decided decrease in penetration value. .The

for many purposes. The penetration-softening point relationship of asphaltic materials of this character is illustrated by the following tabulated results of tests wherein various proportions of a 200 mesh bleaching clay obtained from Death Valley, California, was incorporated in the identical asphalt used in the foregoing specific example.

Penetration Softening Asphalt Clay point Per cent Per cent F.

100 None 16 219 99 1 i6 219 98 2 lo 220 Q0 l0 12 239 255 From the results of these tests herein related, it appears that, whereas the compounded asphalt of the present invention to which 1% boric acid had been added had a softening point of 253 F., and a penetration of 14, the asphalt oompounded with 25% inert filler, which had a comparable softening point, had a penetration of only 9.

I claim:

1. An asphaltic composition in which the normal penetration-softening point relationship of the asphalt constituent has been altered without adversely affecting its weathering characteristics comprising an asphalt with which there has been admixed, at atemperature at which the asphalt is substantially fluid, about'0.25%

' out adversely afl'ecting its weathering charcycles for the unborated product under iden- I acteristics comprising an asphalt with which there has been admixed, at a temperature at which the asphalt is substantially fluid, about 1%. by weight of boric acid without material subsequent oxidation of the composition;

' ALFRED P. LENTZ.