US3322706A - Asphalt compositions and method of improving spot testing to select asphalts - Google Patents

Description

3,322,706 Patented May 30, 1967 Okla, assignor to Con- Ponca City, Okla., a corporation This invention relates to methods of improving the response of certain bituminous material to a testing procedure commonly known as the Oliensis spot test. More particularly, the invention relates to a method of treating asphaltic materials which have not been cracked during refining so as to render these asphalts negative in their response to Oliensis spot testing.

The Oliensis spot test is widely used to determine the state of homogeneity of asphaltic materials. At the time the spot test was first introduced, residua from the thermal cracking of paraffiuic crudes were reduced to asphalt by some refiners and sold for use in paving. These cracked asphalts performed poorly as paving materials because of heterogeneity resulting from the presence of high molecular weight bodies produced as a result of cracking conditions. The heterogeneity-producing high molecular weight bodies resulting from cracking caused the cracked asphalts to change sharply in viscosity with relatively slight changes in temperature and to have low resistance to oxidation, iboth properties unacceptable in paving materials. The lack of homogeneity in such asphalts was indicated by a positive Oliensis spot test, so this test then served the useful purpose of enabling such cracked, inferior asphalts to be justifiably rejected as paving materials. In current asphalt refining technology, however, some straight run, virgin, uncracked asphalts contain certain crude materials, which, though they do not adversely affect the properties and performance of such asphalts as paving materials, do result in a positive response to the Oliensis spot test, causing the unjustified rejection of these asphalts for use as paving materials and substantially lowering their value. It is these materials with Which the present invention is concerned, and it is to be understood that these terms with regard to the asphalts have significance as understood by those skilled in the asphalt art. That is, for example, an uncracked asphalt may have been subjected to very brief or mild cracking conditions but where the degree of cracking from such is so little that the materials are still substantially uncracked or are regarded as uncracked, virgin or straight run asphalts by those skilled in the asphalt art are asphalts included within such terminology.

It is an object of the present invention to provide methods of treating certain asphaltic materials so that these materials, when uncracked in preparation thereof, will respond negatively to an Oliensis spot test.

An additional object of the invention is to provide apparently more homogeneous asphaltic blends which may then be subjected to the Oliensis spot test with desirous negative results of said test being obtained whereby said asphalt will, if it meets other standards, be accepted for paving rather than rejected on the basis of the test as possessing properties of a cracked asphalt.

A further object of the invention is to provide new additives for asphaltic materials for increasing the peptization of asphaltenes in the asphaltic materials, thus increasing the spot test negativity of the asphaltic materials, insofar as spot testing is a measure of homogeneity.

Another object of the invention is to provide an economical procedure for upgrading straight run, virgin, uncracked asphalts to improve the road surfacing properties of these materials.

Other objects and advantages of the invention will become apparent from the following detailed disclosure thereof.

A spot test Which is generally made a part of the specifications for paving asphalt by state highway departments and other groups is the Oliensis spot test. Although, subject to some modifications and variations from group to group, as those skilled in the art are aware, this test, in general, is that described in ASTM proceedings, Part II, Volume 39 (1936). The test is carried out by placing two grams of the bituminous or asphaltic materials to be tested in a flask and dissolving them in a specified quantity of a special naphtha, termed Spot Test Naphtha. The flask and its contents are then warmed to a specified temperature, the solution is thoroughly stirred, and a drop of the solution placed on a piece of clean filter paper. After five minutes, the spot is examined. If the drop forms a dark brown to pale yellowish-brown circular stain with a darker solid or annular nucleus in the center, the spot is termed a positive test, whereas if the spot does not contain such a darker portion or ring and on the contrary is uniform in color, the spot test is reported as negative. An important modified version of this test is included in the procedure which is prescribed by the American Association of State Highway Officials and is designated as test T-102. This test is described in detail hereinafter.

The spot test is indicative of the degree of homogeneity of the bituminous material to which it is applied. In many instances it may be used to indicate accurately the presence or absence of products of cracking in the material. In order to meet the specifications, the bituminous material being tested must show a negative spot test. As sometimes used, however, this test may reject uncracked asphalts which actually are of good quality. For example, some straight run, virgin, vacuum tower bottom asphaltic materials meet all the specifications for paving asphalt and related uses except for their positive reaction to the spot test. These materials react positively, not because of cracking, but because of heterogeneity induced by the presence of certain materials( possibly asphaltenes) derived from the particular crude from which they are refined which do not adversely affect their performance as paving materials. In other words, the inherent characteristics of a particular crude oil may result in asphaltic materials derived therefrom reacting positively to the spot test even though they have not been cracked in the refining process. For example, there is usually no problem in this respect with Mexican crude oils, but a number of crudes from other areas, such as some California and mid-continent crudes, yield asphalts which fail to meet spot test specifications.

It is proposed by the present invention to add to such asphaltic materials certain polar resinous peptizing agents which effectively disperse the asphaltenes in the materials and increase the homogeneity of the materials so that they react negatively to Oliensis spot testing. In this manner, the value of many asphaltic materials may be substantially increased and their usefulness expanded.

A number of potential additive materials have been tested by me, and, of these, four types were found to be effective when added in small quantities to straight run, virgin, uncracked asphalts to change the spot test response of such materials from positive to negative. These types may be broadly categorized as (a) copolymers of ethylene v and vinyl acetate having a comonomer ratio of between 60:40 (ethylene to vinyl acetate) and :10 (ethylene to vinyl acetate), a melt index of between 3 and 200 and a molecular weight of between 200,000 and 600,000, (b) copolymers of ethylene and ethyl acrylate having a comonomer ratio of between 70:30 (ethylene to ethyl amine soap of the general formula in which RC and RCOO represent residues of higher fatty acids after the loss of OH and acid hydrogen respectively and NRN is an alkylene polyamine residue representing the polyamine less the hydrogens normally present on the nitrogens shown. For the preparation of such compounds and further properties see US. Patent No. 2,426,220. At this Writing an acceptable product is sold by the patentee under the trademark Acra 500.

Within these broad definitions of the materials which constitute effective additives to the asphaltic materials, certain species have been found to perform superiorly and are therefore preferred. This functional preference is subject to economic qualifications as more fully described hereinafter. Of the ethylene ethylene-vinyl acetate copolymers, those having the following properties are preferred from the standpoint of efficiency in promoting negative reactivity to the spot test:

Melt Index 12 to 28 Vinyl acetate, weight percent 20 to 35 Tensile strength, p.s.i. 1000 to 2000 Elongation at break, percent 650 to 850 Density at 30 C., grams/cc. About 0.95 Molecular weight 300,000 to 400,000 Brittle point, F. 70

1 Grams of the copolymer which may be pressed .through a standard orifice in ten minutes at 190 F, with a piston weighing 2,160 grams. (ASTM designation D1238-57T.)

2 Using a sample length of l-ineh and a erosshead speed of /g-IDCII per minute. (ASTM D88256l.)

Of the ethylene-ethyl acrylate copolymers, the preferred species are characterized by the following properties:

Melt Index 1 2.5 to 20.1 Ethyl acrylate, weight percent 15 to 20 Tensile strength, p.s.i. 1100 to 2000 Elongation atbreak, percent 2 670 to 810 Softening point, ring and ball, C. 95 to 139 Acid number 143 to 148 Saponification number 145 to 160 Unsaponifiable material, wt. percent 7 to 8 Specific rotation, degrees 3 to -25 Density at 20 C., grams/cc. 1.069 to 1.072 Flash point (COC), C. 218 to 253 The amounts of the described materials which are added to the bituminous base material in order to produce a negative reaction to the spot test are subject to wide variation. Some of the additives are considerably more effective in this respect than others. For example, the most effective of the materials tested were the copolymers of ethylene and vinyl acetate. In the case of this copolymeric material, as little as 0.01 percent by weight was effective to convert certain straight run, virgin, uncracked asphaltic materials which were tested from a positive to a negative spot test. Using the same asphaltic material, it was necessary to add about five times this amount of the Wood rosin derivative in order to achieve the same degree of spot test negativity. The ethyleneethyl acrylate copolymers are intermediate to the wood rosin derivatives and the ethylene-vinyl acetate copolymers in effectiveness.

It should be pointed out that the term effectiveness, as hereinbefore utilized, refers simply to the minimum concentration of a given additive which is required to cause spot test negativity in an uncracked asphaltic material which, except for the incorporation of the additive therein, would react positively to the spot test. The materials which I have found to be most effective in this respect are not necessarily the most desirable from an economic standpoint. For example, the average costs of the wood rosin derivatives are approximately one-fourth that of the ethylene-vinyl acetate copolymers. Thus, in some instances it may be more economical to use higher concentrations of the former materials, rather than lower concentrations of the copolymers in order to achieve spot test negativity in a given asphalt. This is particularly true in view of the fact that asphaltic materials exhibit varying degrees of positivity and negativity and thus vary in their respective additive requirements. In other words, one asphaltic material may be only very slightly positive and require very little additive to upgrade it to spot test negativity. Another asphalt may require more of an additive than the first in order to react negatively to the spot test. In any event, the relatively low current market price of asphalt makes material cost a primary consideration in selection of one of the described additives.

It should further be recalled, as pointed out hereinbefore, that both effectiveness (in terms of concentration required) and material costs vary to some extent within the broad categories of effective additives described above. Thus, a lower ethylene content in the ethylenevinyl acetate copolymer appears to have the effect of improving the ability of the additive to increase the spot test negativity of the asphalt. For example, a copolymer of this type having a monomer ratio of about 67:33 (ethylene to vinyl acetate) and a melt index of about 25 must be added to the ahphaltic material in only about one-fourth the minimum concentration which is required when using a 71:29 monomer ratio species of the same polymer having a melt index of about 15. In view of this manifest difference in effectiveness, I prefer to employ ethylene-ethyl acrylate copolymers having a monomer ratio of between 65:35 and 70:30 (ethylene to vinyl acetate).

The upper limits of the amounts of the additives which should be incorporated in the asphalt are, in general, determined economically, since the relation between the market value of even the upgraded asphalts and the cost of the additives is such that it becomes uneconomical to use the additives for upgrading even in concentrations which are far below the operative maximum concentrations which may be utilized without altering the properties of the asphalt to the extent that it fails to meet other specifications than that of spot test negativiy. In general, the upper limits of operable concentrations of the additive materials is believed to be somewhere between 15 percent and 30 percent by weight, but, under current market and manufacturing cost conditions, the economically feasible concentrations which may be used are considerably below this range, and, as pointed out above, vary from additive type to additive type. In any event, it will rarely be necessary to incorporate more than about 1 percent by weight of the most effective of the additives in order to achieve a negative spot test reaction. A sufficient amount of the particular additive is to be used to enable the asphalt to exhibit a negative Oliensis spot test but in any case the amount should be kept below about 2 percent because of cost considerations.

No special conditions are required for blending the additives with the straight run, virgin, uncracked bituminous material. The additive materials may be finely ground and stirred into the asphalt over a period of time. Preferably, the asphalt is heated, but to a temperature well below the point at which cracking of the asphalt or decomposition of the additive will occur. In the case of the additives of the present invention, a temperature of around 200 F. may generally be safely used. With the preferred ethylene-vinyl acetate copolymeric materials, temperatures in the vicinity of 300 F. may be employed to advantage. During heating of the blend, the mixture is agitated, and such agitation is continued for a sulficient period of time to assure thorough distribution of the additive throughout the asphaltic base material.

As previously indicated, a number of materials were tested to evaluate their effectiveness in improving the response of asphaltic materials to spot testing. In such tests, the modified Oliensis test prescribed by the American Association of State Highway Officials Was utilized. In this test, the basic test hereinbefore described is modified slightly in that, instead of using a pure naphtha solvent of specified quality alone, a percentage of such naphtha is used and the balance of the solvent employed is xylene. Each of these two materials is present in a percent by volume which is a multiple of five. For example, a typical solvent used initially in the test might consist of percent by volume xylene and 85 percent by volume naphtha, or, 25 percent by volume xylene and 75 percent by volume naphtha, etc.

The portion of these two materials present is then varied in 5 percent by volume increments until two difierent solvent mixtures are found which differ only by 5 percent in the quantity of xylene present, and, in one of which, the asphaltic material gives a positive spot test, and in the other, a negative spot test. Since the asphaltic material is more soluble in the xylene than in the naphtha, the solvent mixture of these two which contains the higher xylene content will be the one which yields the negative spot test. The results of this type of modified spot test are reported in terms of the naphtha-Xylene equivalent which is indicative of the degree of spot-forming tendency possessed by the asphaltic material. For ex ample, an asphaltic material which gave a positive test when using a 15 percent xylene-85 percent naphtha test solution, but which gave a negative test When using a percent xylene-80 percent naphtha solution would be said to have a naphtha-xylene equivalent of 15/20. Since a certain naphtha-xylene equivalent value is made a part of the specifications prescribed by many states for asphaltic paving materials, this value was used in all tests performed for evaluating the additives and the blend compositions of the present invention and in testing and comparing other materials which were determined to be ineffective as additives.

In commencing the test, a sample of the asphalt to be tested weighing 2:0.02 grams is placed in a 50 milliliter flask and spread in a thin film. 10.2 milliliters of the specified solvent (naphtha and xylene) are added to the flask. A stopper provided with an 8-inch length of glass tubing is inserted and the flask is swirled for five secon'ds. If necessary in order to disperse the asphalt, the flask is immersed in boiling water for one minute and then again swirled for five seconds. The heating and swirling are repeated until complete dispersion has taken place.

After complete dispersion, the end of the glass tube is lowered below the level of the solution and the flask cooled for thirty minutes at room temperature. The flask is then warmed for fifteen minutes in a water bath held at 89.6:10" F. The solution is thoroughly stirred and a clean stirring rod used to place a drop of solution on a piece of Whatman No. 50 filter paper. After five minutes, the spot is examined by holding the paper at arms length with the plane of the paper approximately at right angles to the line of vision with a good light source at the observers back. If the drop forms a brown to pale yellowish-brown circular stain with a darker solid or annular nucleus in the center, the spot is reported as positive. If the dark nucleus is absent, the spot is reported as negative.

As indicated above, the tests are repeated with incremental 5 percent changes in the ratio of naphtha to xylene until two consecutive solutions are found which respectively give a positive and a negative spot test.

The asphaltic materials which were employed in the tests were, in each case, straight run, vacuum reduced, virgin, uncracked asphalts obtained from the Denver refinery of Continental Oil Company. These asphaltic materials meet all of the specifications for pacing asphalt except for their positive reaction or excessively high naphthaxylene equivalent in the Oliensis spot test and in spite of the test results actually appears to be a satisfactory paving material. It wa calculated that upgrading of this material so as to give it a substantially lower naphthaxylene equivalent and thereby make it acceptable (by Oliensis test standards as well as others) for paving purposes would increase its value by a factor of between 50 percent and percent.

Initially, a vacuum reduced, uncracked asphalt having a naphtha-xylene equivalent of 5/ 10, and therefore being classed as borderline or off-specification under those state specifications requiring a negative test when a maximum xylene concentration of 10 percent by volume or less is used, was blended with small amounts of a number of materials and the blends tested for improvement in the naphtha-xylene equivalent. Examples of the results of these tests are reported in Tables 1, 2, and 3 below. Trade names are given for all additives reported in these eX- amples, since absolutely pure compounds were sometimes not used, and since the specific chemical character of all the materials which failed to give effective results when tested was not known to me at the time of the test. Examples of the tested materials as they may be identified by their trade names are broadly defined as follows:

Ethylene-vinyl acetate copolymers Elvax 25 0molecular weight 400,000-E. I. du Pont de Nemours.

Elvax 15 0molecular weight 300,000-E. I. du Pont de Nemours.

DXQD .O042N.5Uni0n Carbide.

Ethylene-ethyl acrylate copolymers Zetafin 70A1-Dow Chemical Company.

Wood rosin derivative REDUCED, UNORACKED ASPHALT, NAPH'lHA-XYLENE EQUIVALENT OF UNTREAIED ASPHALT=5/l0 Effective Additive Percent Used Naphtha-Xylene Used Equivalent Elvax 250 0. 2 0/5 Elvax 0. 05 0/5 Table 1 indicates that the two ethylene-vinyl acetate copolymers (Elvax 250 and Elvax 150) effectively lower the naphtha-xylene equivalent of the asphaltic material in which they are incorporated. Other materials which were tested in blends with the 5/10 asphalt were found ineffective in this respect and, in fact, tend to increase the naphtha-xylene equivalent. The lower molecular weight copolymer (Elvax 150) was the most elfective of the two species of the copolymer which functioned to increase the spot test negativity of the asphalt, requiring only one-fourth as large concentration to lower the naphtha-xylene equivalent from 5/10 to 0/5, as was required in the case of the Elvax 25 0.

Copolyrner Elvax 150 Elvax 250 Oomonomer Ratio, Wt. Percent (eth ylene-vinyl acetate) Melt Index (ASTM D-l238-57T) 66:34 to 68:32 73:27 to 71:29 22 to 28 12 to 18 Refractive Index, ND 1. 485 1. 482 Density at 30 0., grams/cc-. 0.95 0. 95 Softening Point (Ring and Ball), F 243 276 Inherent Viscosity, cp. at 30 C. 0. 77 0.85 Molecular Weight 300,000 400, 000 Tensile Strength, p.s.i. 1, 000 2,000 Elongation at Break, Percent 2 700 750 1 Determined using a solution of 0.25 percent by weight of the copolymer in toluene.

2 Orosshead speed of %'inch per minute and a sample length of l-inch (ASTM D88256T).

A Denver refinery, vacuum reduced, uncracked asphalt derived from a different crude oil than that from which the 10/ 15 naphtha-xylene equivalent asphalt described above was derived was used for testing additional additive materials. The naphtha-xylene equivalent of this asphalt was 15/ 20 and it was therefore sub-specification under the specifications of the state of Colorado requiring a naphtha- Xylene equivalent of 5/10 or less. The results of tests of blends of this asphalt with the several additional additive materials (other than those types tested, and the results tabulated in Table 1 above) are set forth in Table 2.

TABLE 2.ADDITIVES EFFECT ON SPOT TEST OF VACUUM REDUCED, UNCRACKED ASPHALT, NAPHTHA-XYLENE EQUIVALENT OF UNTREATED ASPHALT=l5/20 Effective Additive Used Percent Used Naphtha Xylene Equivalent DXQD .0042N.5 0.5 Zetalin 70A1 0.5 0 Poly Pale Resin 0. 0/5

As indicated by the trade name key set forth above, the DXQD .0042N.5 is another ethylene-vinyl acetate copolymer. In DXQD .0042N.5, the ethylene to vinyl acetate ratio is 77:23, and the material is characterized by a melt index of about 200. The Zetafin 7OA1 ethyleneethyl acrylate copolymer is characterized by the following properties:

Ethyl acrylate content, Wt. percent 16 to 24.

Elongation at break, percent 1 675 to 725. Low temperature brittleness, C.

(ASTM D-746-57T) Molecular weight 1 Test specimens strained at -2 inches per minute crosshead speed.

8 The wood rosin derivative employed in the examples of the tests set forth in Table 2 comprised about 40 percent stabilized, dimerized pine wood rosin acids with the balance being predominantly monomeric wood rosin acids. Additional typical properties of this material are:

Softening point, ring and ball, C. 95 Acid number 148 Saponification number 160 Flash point (COC), C. 218

Density at 20 C., grams/cc 1.0719

It is apparent from Table 2 that the two copolymcric materials which proved to be effective additives in the tests of the asphalt having a naphtha-Xylene equivalent of 15/20 were slightly more effective than the wood rosin derivatives which were tested since less was required.

A third vacuum-reduced, uncracked asphaltic material which was derived from yet a different type of crude oil than that from which the 10/ 15 and 15/ 20 asphalts used in the previous tests were derived was used in comparing some of the additives found effective in the initial tests with yet other materials which had not been subjected to previous testing. The results of these tests are reported in Table 3.

Effective Additive Used Percent Used Naphtha-Xylcne Equivalent 1 Zctafin Al 1 The results in Table 3 also indicate that the ethylenevinyl acetate copolymer (Elvax 150) of about 300,000 molecular weight and having an ethylene-vinyl acetate monomer ratio of about 67:33 again was the best material of those tested in improving the spot test negativity of the asphalts to which it is added.

As has been previously indicated, it is essential that the additives which are incorporated in the asphaltic materials for the purpose of causing them to react negatively to the spot test not interfere with the positive reaction of such asphalts to the spot test as a result of any deleterious cracking which may have occurred therein. In other words, to .be suitable for the use proposed herein, additive materials which are blended with asphalts must not interfere with the ability of the Oliensis spot test to indicate the occurrence of deleterious cracking in the asphaltic material by yielding a positive result. In order to evaluate the acceptability of the additives of the invention in this respect, tests were conducted with cracked and uncracked asphalt to determine their reaction to the Oliensis spot test when blended with the additives found effective in the hereinbefore described tests. As an example of the results of such tests, Table 4 below illustrates the results which were obtained when varying concentrations of Elvax 150 were blended with a number of asphaltic materials, one

0 of which was inherently cracked and one of which was TABLE 4.RESIONSE OF FIVE DENVER ASPHALT SAMPLES TO ELVAX 150 Asphalt I (prc- II III III IV V cracked) Treatment *IIcatOd Naphtha/Xylene Equivalent 100 00/65 /85 0 85+ Wlth 0.05%E1VQ42K 150. 30+ 0 0 30+ 0 0 With 0.10% Elvax 30+ 0 0 30+ 0 0 With 0.3% Elvax 150. 30+ 0 0 30+ 0 0 With 0.5% Elvax 150 20/30 0 0 30+ 0 0 It will be noted from the results tabulated in Table 4 that the Elvax 150 was ineffective to increase the spot test negativity of the deleteriously cracked asphalt by a degree sufiicient to meet the usual naphtha-xylene equivalent specification. On the other hand, the copolymeric additive was effective to render negative to the spot test all of the uncracked asphalts which were tested, despite a relatively high degree of positivity to the spot test prior to addition of the additives. The effect of inducing deleterious cracking in a previously uncracked asphalt is clearly indicated by the results obtained when Asphalt III in the table was initially made negative by the addition of small amounts of Elvax thereto, but subsequently, and after heating to 700 F. for one hour, was not rendered sufficiently negative to pass the spot test despite the addition of as much as 0.5% of the additive thereto.

The additives of the invention do not appear to adversely affect other properties of the asphalts with which they are blended, and which are critical in the specifications which are generally employed for asphaltic paving materials. As an example of the manner in which the addition of Elvax 150 (ethylene-vinyl acetate copolymer) affected the properties of asphalt to which it was added, the results obtained in measuring these properties are tabulated in Table 5 hereinafter. The asphalt employed in the test was that designated Asphalt IV in Table 4, and was characterized by a natural or untreated naphtha-xylene equipvalent of 85+ (that is, in excess of 85 percent xylene was required to render the asphaltic material negative to the spot test). To this asphalt was added 0.05 percent by weight of Elvax 150.

Chemistry, American Chemical Society, suggested a procedure for measuring the state of peptization of asphalts. Heithaus suggested that the degree of peptization could be represented by the equation o 1P,, where P represents the state of peptization of the asphalt, P the peptizability of the asphaltenes in the asphalt, and P the peptizing power of the maltenes (petrolenes). Using the procedure prescribed by Heithaus for determining these parameters, it was found that the addition of 0.08 percent of Elvax 150 to the asphalt used in Table 1 above had the eiTect of increasing P from 0.713 to 0.816 while only slightly affecting P (this parameter was lowered from 0.67 to 0.66). The state of peptization P was thus increased from 2.16 to 2.40.

Although certain exemplary embodiments of the invention have been hereinbefore set forth, it is expected that a number of minor modifications and changes in the concentrations of additives utilized, conditions of blending employed, and molecular constitution of the additives within the broad definitions hereinbefore prescribed will be resorted to by those skilled in the art to meet the needs of a particular asphaltic or bituminous material, or particular conditions of use of such material. However, insofar as such modifications and changes continue to rely upon the basic inventive principles herein disclosed, it is intended that such innovations be circumscribed by the spirit and scope of the present invention, except as the same may be necessarily limited by the appended claims.

TABLE 5.-EFFECT OF ELVAX 150 ON ASPEALT PROPERTIES Specifications Asphalt N 0. IV

AASHO Colorado Untreated +05% Elvax Penetration, 77 F., 100 g., 5 Sec 85-100 85-100 99 101 Penetration, 39.2" F., 200 g., 60 sec 19 18 Penetration Ratio 19 18 Flash Point, 0.0.0., F 600 650 Flash Point, P-M, F 600+ 600+ Ductility, 77 F., 5 crn./miu., ems 121 132 Heat Loss, 325 F., 5 hrs., wt. Percent 0.0 0.0

Pen. Res, Percent of Original. 78 80 Thin Film Loss, Wt. Percent..- 0.0 0.0

Pen. Res, Percent of Origin 48 Duet. Res, 77 Fr, cms 126 150+ Solubility in CC14, Wt. PereenL- 99. 95 99. 93 N aphtha-Xylene Equivalent 85+ 0 The results obtained in the tests of the properties of I claim:

both the additive-containing asphalt and the asphalt prior to addition of the additive show that, in both cases, the asphalt meets all of the specifications, except for the spot test. Addition of the ethylene-vinyl acetate copolymer causes no significant change in the properties of the asphalt, except for rendering it negative to the spot test and slightly improving the ductility of the thin film residue.

From the foregoing discussion, it will be apparent that several highly effective additive materials have been identified which may be easily incorporated in bituminous materials and which function to cause these materials, when they have not been cracked in the process of refining, to react negatively to spot testing. The mechanism by which these materials function is not well understood, but it is believed that the polarity of the peptizing materials (petrolenes) normally present in such bituminous materials is increased by the addition of the additives, and that such increase in polarity in turn increases the peptizing power of such petrolenes. J. I. Heithaus, in a paper entitled Measurement and Significance of Asphaltene Peptization, presented in 1960 at the Symposium of Fundamental Nature of Asphalt, Division of Petroleum Comonomer ratio, weight percent ethylene to ethyl acetate 66:34 to 68:32

Melt index 22 to 28 Refractive index, 21 1.485 Density at 30 C., grams/cc. 0.95 Softening point (ring and ball), F 243 Inherent viscosity, cp. at 30 C. 0.77 Molecular weight 300,000 Tensile strength, p.s.i 1,000 Elongation at break, percent 700 3. The method of improving the response of uncracked bituminous material which exhibits a positive test when subjected to Oliensis spot testing whereby the bituminous material exhibits a negative test which comprises adding to said materials in an amount between about 0.01 and about 15.0 percent by weight a resinous material in which the resinous material is an ethylene-vinyl acetate copolymer having the following properties:

Melt index 12 to 28 Vinyl acetate, weight percent 20 to 35 Tensile strength, p.s.i 1,000 to 2,000 Elongation at break, percent 650 to 850 Density at 30 C., grams/cc. about 0.95 Molecular weight 300,000 to 400,000

References Cited UNITED STATES PATENTS 2,426,220 8/ 1947 Johnson 106123 2,514,954 7/1950 Johnson 106232 2,658,026 11/1953 MacLaren et al. 196--22 2,687,989 8/1954 Goodwin 196-74 2,691,621 10/1954 Gagle 196-22 2,822,282 2/1958 Garwin 106-232 2,836,507 5/1958 Barth 106-232 2,891,873 6/1959 Falken'berg et al. 106273 3,249,567 5/ 1966 Vigneault.

OTHER REFERENCES Hercules Powder Co., Naval Stores Dept., Poly-Pale Resin, 1946, p. 4.

Zimmerman et al., Handbook of Material Trade Names, Industrial Research Service, Dover, N.I-I., 1946, p. 353.

MORRIS LIEBMAN, Primary Examiner.

ALEXANDER H. BRODMERKEL, Examiner.

J. E. CARSON, J. A. GAZEWOOD, B. A. AMERNICK,

Assistant Examiners.

Claims (1)

1. A PAVING COMPOSITION COMPRISING STRAIGHT RUN, UNCRACKED ASPHALT WHICH EXHIBITS A POSITIVE TEST WHEN SUBJECTED TO OLIENSIS SPOT TESTING AND AN ETHYLENE-VINYL ACETATE COPOLYMER HAVING AN ETHYLENE TO VINYL ACETATE RATION OF FROM ABOUT 60:40 TO ABOUT 90:10. A MELT INDEX OF BETWEEN 3 AND 200, AND A MOLECULAR WEIGHT OF BETWEEN ABOUT 200,000 AND ABOUT 600,000, THE COPOLYMER BEING DISPERSED IN THE ASPHALT IN AN AMOUNT BETWEEN ABOUT 0.01 AND 15.0 PERCENT BY WEIGHT.