US3453226A

US3453226A - Petrolene composition containing atactic polyolefin

Info

Publication number: US3453226A
Application number: US453187A
Authority: US
Inventors: Luke W Corbett
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1965-05-04
Filing date: 1965-05-04
Publication date: 1969-07-01
Anticipated expiration: 1986-07-01
Also published as: GB1247247A

Description

United States Patent U.S. Cl. 26028.5 4 Claims ABSTRACT OF THE DISCLOSURE This invention is concerned with an asphaltene-free composition suitable for paving or similar uses comprising a major amount of petrolene and a minor proportion of atactic polymers or copolymers of C to C olefins. Such compositions have properties superior to those compositions of asphalt and atactic polypropylene.

The present invention relates to petrolene, i.e. deasphaltened asphalt, compositions containing atactic polyolefin. In particular, it concerns compositions suitable for paving and other related uses of decreased temperature susceptibility and improved ductility and viscosity characteristics, which compositions comprise a major proportion of a petrolene and a minor proportion of atactic polymers or copolymers of C to C olefins.

Paving grade asphalts are made from residuum stocks derived from various crudes. In the past, one of two methods has been generally employed to produce high quality asphalts suitable for road paving. One method involves straight vacuum deduction, while the other method involves air blowing of pipe still residuum. Both these methods have significant drawbacks. One of the major problems inherent in both these methods is the difficulty. of meeting paving asphalt specifications prescribed by state and federal governments. It is usually necessary to exercise careful selection of crude and very careful control in said reduction or in said air blowing to meet these paving asphalt specifications, namely, in such properties as penetration, temperature susceptibility, viscosity and ductility.

Recently, it has been suggested in U.S. Patent 3,144,423 that paving grade asphalts which meet state and federal government specifications may be provided by adding small amounts of atactic polypropylene with asphalt, thus providing a simple method of meeting specifications. The asphalt paving compositions described in U.S. 3,144,423 consist of a mixture of asphalt and a small amount of atactic polypropylene. It has now been found and forms a basis of the present invention that superior paving compositions can be obtained by first deasphaltening an asphalt to make etrolenes and then incorporating a small amount of atactic polypropylene or similar atactic polyolefin into the petrolenes.

Asphalt is a thermo plastic mixture of high molecular weight hydrocarbons plus a small amount of sulfur, nitrogen, and oxygen derivatives. Due to the complexity of the large number of hydrocarbons in asphalt, the exact chemical identity has not been established too well. However, a large portion of asphalt has been identified as polycyclic aromatics, some being substituted with aliphatic side chains. Asphalt is considered to be a colloidal suspension in which very high molecular weight hydrocarbons called asphaltenes are suspended in a matrix of lower molecular weight hydrocarbons called petrolenes. The petrolenes are soluble in a certain class of petroleum solvents whereas the asphaltenes are insoluble in said solvents. Therefore, solvent precipitation can be used to separate asphaltenes and petrolenes.

Asphaltenes are solid infusible brown-black material having a specific gravity of about 1.15 to 1.25 at 77/77 F. and may be defined as that portion of asphalt which is insoluble in petroleum solvents composed entirely of aliphatic open chain hydrocarbons, i.e. paraffinic solvents, having a gravity of 86 to 88 Baum being evuivalent to a specific gravity of 0.638 at 60/60 F.) and at least of whose constituents boil between and 150 F. Pure paraffinic solvents such as n-pentane, n-hexane, n-heptane and iso-octane accomplish essentially the same separation of asphaltenes and petrolenes and have the advantage of uniformity of solvent composition.

Petrolenes may be defined as that portion of an asphalt, or crude oil residuum, from which the asphaltenes have been removed. The process of removing the asphaltenes is termed deasphaltening and one such method is described in U.S. Patent 3,087,887. Various other methods of deasphaltening are well known in the art.

The data in Table I illustrate the composition and properties of typical asphaltenes and petrolenes.

According to the present invention, superior paving grade compositions are prepared by blending petrolenes with atactic polyolefins.

Atactic, i.e. substantially non-crystalline or substantially amorphous, polyolefins suitable for use in the present invention may be made by polymerization of ethylene, or propylene, or by copolymerization of mixtures of ethylene and propylene. Although it is desirable insofar as is practical to employ polyolefins that are entirely atactic and devoid of crystalline structure, it is not always possible to secure such purities, particularly in commercial operations. Thus, for the purpose of the present invention the term atactic polyolefin includes, in addition to polyolefins which are entirely atactic, polyolefins which are substantially non-crystalline, i.e. polyolefins which contain no more than about 20 wt. percent, preferably less than 10 wt. percent, crystalline polymer. Crystalline polymer is that polymer which is insoluble in normal heptane when subjected to Soxhlet extraction for 24 hours. The molecular weight of the atactic polyolefin can vary depending upon the particular polymer or copolymer employed but in general will range from about 10,000 to about 200,000 and is preferably about 10,000 to about 100,000, and most preferably about 25,000 to 60,000. The molecular weight ranges are based upon viscosity weight average data using the Kinsinger correlation as determined at a temperature of C. and a concentration ratio of 1 mg. polymer/1 ml. of Decalin. Atactic polypropylene is preferred.

An inexpensive source of atactic polyproplene is the xylene slurry of reject or off specification polypropylene from a commercial polymerization process using a metal alkyl-metal halide catalyst system, the so called Ziegler type of catalyst. The slurry is freed from its xylene by distillation to give a dry mixture of both atactic and isotactic polypropylene. To this dry mixture is added any suitable aliphatic hydrocarbon solvent or mixture of aliphatic hydrocarbons, for example, a C to C naphtha cut, or normal heptane, or normal hexane. These solvents selectively dissolve out the atactic polypropylene while leaving the bulk of the crystalline polypropylene in the insoluble state, yielding a solution, which after filtering out the insoluble crystalline polypropylene can be blended with the above-described petrolenes. On the other hand,

if a solution blending method is not desired all of the aliphatic hydrocarbon solvent can be removed, for example by simple heating, leaving atactic polypropylene.

In another method for isolating atactic polypropylene from reject polypropylene of a commercial polypropylene plant the xylene filtrate stream may be blended directly, with or without a partial removal of some of the xylene, with the above-described petrolenes. The xylene filtrate stream may constitute xylene and about 2 to 50 wt. percent total polypropylene of which up to about 40 wt. percent of the polypropylene is in the isotactic (i.e. crystalline) form. After the solution blending has been completed, the mixture is passed through a heater under pressure and flash evaporated under vacuum to remove some or all of the xylene.

The amount of atactic polyolefin, preferably atactic polypropylene, which is mixed with the petrolene may vary depending upon the final properties to be achieved in the paving composition. In general, the composition of the present invention will comprise a major amount of petrolenes and about 1 to 30 wt. percent, preferably about 3 to 20 wt. percent, atactic polyolefin. The composition will be substantially asphaltene-free, i.e. containing less than 1.0 wt. percent and preferably less than 0.5 wt. percent asphaltene. All of said weight percents are based upon the weight of the total composition. In a most preferred composition about 3 to 20 wt. percent atactic polypropylene is incorporated into the petrolenes.

Obvious modifications such as blending of the asphalt composition of the invention with mineral aggregates, cement, sand, asbestos, vermiculite, Fiberglas and the like are included in the scope of this invention.

The composition of the present invention can be prepared by simple fluxing (i.e., simple mixing) of the atactic polyolefin and the petrolenes. In general, temperatures in the range of about 200 F. to about 450 F. are suitable.

Some of the improvements attained by combining atactic polyolefin, particularly atactic polypropylene, with petrolene are illlustrated by the following examples. In the examples the physical property data shown were obtained by the procedures indicated below:

Softening point was determined by the ring and ball method provided by ASTM D3662T. Penetration was determined by the procedure of ASTM D561. Penetration ratio was calculated by multiplying by 100, the ratio of the penetration at 39.2 F. to the penetration at 77 F. Ductility was determined by the procedure of ASTM D11344. Thin film test residue was determined by the procedure of ASTM D1754-63T. Aging index was determined by the procedure described in ASTM STP No. 309, p. 133 (1961). Viscosities were determined by the Furol viscosity procedure and by the micro method for determining viscosity Which is described in the Procedings of typical properties shown above in Table I. The atactic polypropylene employed was recovered from the xylene slurry of reject polypropylene (mixture of atactic and crystalline) from a commercial polypropylene plant. The reject polymer was dried (i.e., freed from xylene) and extracted with normal heptane. The normal heptane selectively dissolved the atactic polypropylene while leaving the crystalline polypropylene in the insoluble state. The resulting solution was filtered to remove insoluble crystalline polypropylene and the n-heptane was evaporated to yield water white atactic polypropylene having a molecular weight of about 39,500, an intrinsic viscosity of .533 at 135 C., a density of .861, a crystalline polymer content of 8.9 wt. percent (infrared), and insolubles (in n-heptane) content of 2.9 wt. percent. The physical properties of the resulting pavings compositions were compared with the physical properties of the straight reduced asphalt from which the petrolene was derived. The results are shown in Table II.

TABLE II Composition (wt. percent):

Straight reduced asphalt 100 Petrolene 80 Ataetie polypropylene 20 Properties:

Softening point, F 112 170 Penetration at 77 F. (100 gins/5 185 158 Penetration at 39 sec.) 60 97 Pen-ratio 30. 2 52. 5 Ductility at 392 F. (1 cm./min.). 50+ Furol vis. at 275 F. SFS 116 530 The results in Table II illustrate how temperature susceptibility as measured by penetration-ratio and Furol viscosity at 275 F., of an asphalt can be greatly improved by deasphaltening said asphalt and adding atactic polypropylene.

EXAMPLE 2 Asphalt Petrolene Softening point, F 112 111 Penetration at 392 F. (200 gins/ see.) 38 40 Penetration at 77 F. (100 gms./5 see)... 108 112 Ductility at 392 F. (5 cmJmin.) 50+ 50+ Furol vis. at 275 F., SFS 160 171 TABLE IIL-COMPARISON OF ASPHALT VERSUS PETROLENE IN ATACTIC POLYPROPYLENE COMPOSITIONS Composition, percent by wt. Thin film test residue Atactic poly- Pen. at 77, Vise. at 77. Percent Visc. at 77, Aging Asphalt Petroleno propylene 100 g./5 see. poise 10 ret. pen. poi5e 10 index 5 74 2 50 71 6. 70 2. 74 5 74 1. 52 84 2. 80 1. 78 3 81 1. 85 64 5.02 2. 85 3 81 1. 51 76 2. 45 1. 63

the Association of Alphalt Paving Technologists, 24, 31 The data in Table III establish a superiority of petrolene- EXAMPLE 1 A paving composition of improved physical properties was prepared by blending =80 wt. percent petrolenes with 20 wt. percent atactic polypropylene by simple mixing at about 250 F. The petrolene was that portion of a straight reduced asphalt from a Lagunillas crude which remained after said asphalt was deasphaltened (using n-hexane in a atactic polypropylene compositions over asphalt-atactic polypropylene compositions. For example, comparing compositions A and B, which have the same penetration at 77 F., it was unexpectedly found in the Thin Film Test that the percentage of retained penetration was notably higher, indicating less hardening in the case of the petrolene-atactic polypropylene blend, i.e., composition B. This superior resistance to hardening is also shown by the lower Aging Index. Compositions C and D provide a one-stage extraction at 77 B). These petrolenes had the comparison, again at the same penetration levels, and,

again, the results show the superiority of the petroleneatactic polypropylene blend as compared to the asphaltatactic polypropylene blend.

Table IV shows the penetration and ductility characteristics of blends F, G, H and J.

The data in Table IV was used to compare the ductility of a petrolene-atactic polypropylene composition of 50 penetration at a temperature of 39.2 F. with the ductility of an asphalt-atactic polypropylene composition of 50 penetration also at a temperature of 392 F. Based upon this data at 50 penetration and at 392 F. the petrolene composition would have a ductility of 74 cm. while the asphalt composition'would have a ductility of 15 cm. Thus, it is apparent that the petrolene compositions of the present invention possess superior ductility as compared to compositions employing asphalt.

While the invention has been described primarily with reference to compositions for use in paving, the compositions of the present invention may find equal utility where compositions having similar physical properties are required. For example, soil stabilization and protection of banks and canals by coating, pipe coating, coating of metals which are to be buried in soil and molding articles such as battery boxes and tiles, and the like, are all contemplated.

What is claimed is:

1. A substantially asphaltene-free composition suitable for use as a paving or coating composition comprising a major amount of petrolene and about 1 to 30 wt. percent, based on the total composition, atactic polymer of C to C monoolefin.

2. A substantially asphaltene-free composition comprising a major amount of petrolene and about 1 to 30 wt. percent atactic polypropylene.

3. A substantially asphaltene-free composition according to claim 2 wherein the molecular weight of said atactic polypropylene is in the range of about 25,000 to 60,000.

4. A composition comprising a major amount of petrolene and about 3 to 20 wt. percent atactic polypropylene, said composition being substantially asphaltene-free.

US. Cl. X.R.