WO2019172888A1

WO2019172888A1 - Process for producing a performance grade asphalt composition

Info

Publication number: WO2019172888A1
Application number: PCT/US2018/021120
Authority: WO
Inventors: Joana PERALTA; Ranjini MURTHY; Tyler Scot DOLLY
Original assignee: Wacker Chemie Ag
Priority date: 2018-03-06
Filing date: 2018-03-06
Publication date: 2019-09-12

Abstract

The useful temperature interval ("UTI") of a performance grade asphalt composition, when used in conjunction with an "S"-polymer, can be broadened by the addition of a VAE polymer to such an extent that the high end temperature increases by at least one grade and the low end temperature obtained as a result of the addition of the S-polymer is reduced.

Description

PROCESS FOR PRODUCING A PERFORMANCE GRADE ASPHALT COMPOSITION

BACKGROUND OF THE INVENTION

1 Field of the Invention

[0001] Asphalt or bitumen (called“asphalt” herein), are terms used to describe the residue left over from the petrochemical refining process. Asphalt is used in a variety of applications, for uses such as, but not limited to, paving, sealing, coating, roofing, waterproofing, crack propagation prevention and draining, and as weather barriers.

2. Description of the Related Art

[0002] Asphalt without polymer modification is typically soft at room temperature, and tends to be brittle at lower temperatures, therefore lacking properties for use on its own in some of the applications mentioned above. A general strategy is to modify the asphalt with a variety of property enhancing polymers and/or additives.

[0003] Polymer modification, depending on the application, is generally intended to provide many benefits, such as, but not limited to, improvements in viscosity, softening point, ductility, resiliency, penetration, elastic recovery, tensile strength, tack, flow or creep resistance, adhesion, flexibility, and low and high temperature performance. Most polymer modifications of asphalt in non-aqueous systems are accomplished with styrene butadiene styrene (SBS), styrene butadiene rubber (SBR), styrene ethylene butylene styrene (SEBS), styrene isoprene butadiene styrene (SIBS), styrene isoprene styrene (SIS), which are called "S-polymers," herein, and ground tire rubber (GTR) containing the S-polymers mentioned above. In some cases, polymer modification of non-aqueous asphalt may be accomplished by using other polymers, such as, but not limited to, ethylene-vinyl acetate (EVA), polyethylene (PE), high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), atactic polypropylene (APP), recycled APP, etc. [0004] In the U.S.A. the commonly used system to grade asphalt is the Performance Grade

System. This system was established by the U.S. Department of Transportation which conducted the Strategic Highway Research Program (SHRP) to develop new ways to specify, test and design asphalt. The final product from SHRP is referred to as“Superpave” or Super Performing Asphalt Grade, which is abbreviated as Performance Grade Asphalt (PG asphalt). For additional explanations of these terms, as well as the test equipment, and rheological tests, reference may be made to SUPERPAVE Series No. 1 (SP-l), (1997 printing), published by the Asphalt Institute (Research Park Drive, P.O. Box 14052, Lexington, Ky. 40512-4052) (hereinafter, "SUPERPAVE booklet"), which is hereby incorporated by reference in its entirety. Rolling Thin Film Ovens (RTFO) and Pressure Aging Vessels (PAV) are used to simulate binder aging (hardening) characteristics. Dynamic Shear Rheometers (DSR) are used to measure rheological properties of asphalt at high and intermediate temperatures. This, in turn, is used to predict permanent deformation or rutting and fatigue cracking of road material. Bending Beam Rheometers (BBR) are used to measure binder properties at low temperatures. These values predict thermal or low temperature cracking and or low temperature performance.

[0005] The performance grading system is applied to asphalt binders, which are defined as asphalt based cements that are produced by petroleum distillation residue either with or without the addition of modifiers. The requirements for Performing Grade asphalt are defined based on several tests: flash point (ASTM D92), viscosity at 135 °C or 275 °F (ASTM D4402), dynamic shear (ASTM D7175), rolling thin-film oven (ASTM D2872), pressure aging vessel (ASTM D6521), flexural creep stiffness (ASTM D6648), and direct tension (ASTM D6723). With these tests asphalt compositions are assigned certain performance grades, for example, PG 64-22. The designation of PG 64-22, means that the high temperature PG test was passed at 64°C, and the low temperature PG tests were passed at -22°C. The difference between the high temperature and low temperature value is called the Useful Temperature Interval, or (“UTI”). Performance Grades (“PG”s) are defined in ASTM D-6373-16.

[0006] Polymers, especially the "S-polymers" influence the working range of asphalt. For example, addition of an SBS-modifier to asphalt cement binder can change the PG from 64-22 to 70-16 or 76-10, etc. depending on the dosage levels. However, these polymers increase not only the high PG temperature but also, inadvertently, increase the low PG temperature. Thus, the UTI is diminished.

[0007] U.S. 6,203,606 Bl relates to performance grade asphalt comprising asphalt, aggregates and a performance grade modifier, and to a process for producing performance grade asphalt (PG asphalt). The process includes the blending of a performance grade modifier with the asphalt prior to mixing with aggregate. The performance grade modifier is a vacuum distilled component of recycled (used) lubricating oil. However, this PG modifier simultaneously reduces the high temperature limit and the low temperature limit of the PG asphalt in a ratio of about 1 : 1.

[0008] In U.S. published patent application U.S. 2006/0122292 Al improved PG asphalt is obtained by blending a polymer-modified asphalt with a water-insoluble heavy metal soap.

[0009] U.S. 8,206,500 Bl describes a PG asphalt mix which comprises an asphalt extender obtained as residue in the refining of waste lubricating oil. It has been found that the addition of this modifier decreases both the lower and upper ends of the temperature range of the performance grade asphalt in a ratio of about 1 : 1.

[0010] WO 2016/183144 Al describes the use of vinyl acetate/ethylene polymer powders for the modification of asphalt. Penetration values, mechanical properties and workability of the asphalt composition were improved with this modifier.

[0011] There has been a long felt need in the asphalt industry to provide a method for modifying performance grade asphalt compositions to obtain a composition which is effective over a wider range of temperatures, in other words has a larger UTI.

SUMMARY OF THE INVENTION

[0012] It has now been surprisingly discovered the usable temperature range of performance grade asphalt composition, as reflected by its UTI, can be increased by incorporating into the asphalt a vinyl acetate / ethylene copolymer containing more than 50 weight percent vinyl acetate-derived moieties along with an“S-polymer.” DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The subject of the invention is thus a process for the broadening of the temperature range of a performance grade asphalt composition by adding both at least one vinyl acetate- ethylene (VAE) polymer or copolymer and an“S” polymer to asphalt in combination. When using a VAE/“S-polymer” combination to modify a PG asphalt binder, the effect is an increase in the upper end temperature and, surprisingly, either a reduced or unaltered lower end temperature. Typically, modification of asphalt with an“S” polymer increases both the upper and lower end temperatures, thus compromising low temperature performance.

[0014] The asphalt used in the present invention also includes, but is not limited to, natural products such as lake asphalt, gilsonite, and natural rock asphalt. Further, it includes crude petroleum residues, such as, but not limited to, paraffin base, mixed base, and asphalt base. The asphalt base further includes, for example, asphalt flux, asphalt cements, distillation tower bottoms and oxidized asphalts, or any of the above combinations thereof. Still further, the bituminous materials used in the present invention include, tars, for example, from a coal destructive distillation and cracking of petroleum vapors or any combinations thereof. Even further, the bituminous materials used in the present invention may include asphalt emulsions, cutbacks and road oils, wherein the binder is PG graded after extraction processes, such as, distillation, low temperature evaporation, etc.

[0015] By the term“non-aqueous asphalt” is meant that the asphalt used in preparing the inventive composition is used in substantially non-aqueous form. The resulting product is also substantially non-aqueous, and is preferably used in this form. However, following the blending operation, the non-aqueous polymer-modified composition can be emulsified to form an aqueous polymer-modified asphalt emulsion, or diluted with solvents to obtain modified asphalt emulsions.

[0016] While the composition of the polymer modified asphalt composition depends on the end-use application and the required properties, it generally comprises 60 to 99 % by weight, preferably 70 to 98 % by weight of the asphalt component, and more preferably 80 to 95% by weight of asphalt component, in each case based on the total weight of the polymer-modified asphalt composition. [0017] In a preferred embodiment, 0.1 to < 6% by weight of the performance grade asphalt composition comprises one or more styrene polymers (S-polymers) from the group comprising styrene butadiene styrene (SBS), styrene butadiene rubber (SBR), styrene ethylene butylene styrene (SEBS), styrene isoprene butadiene styrene (SIBS), styrene isoprene styrene (SIS) and ground tire rubber (GTR). These modifiers are preferably present in amounts of less than 6 % by weight, more preferably less than 5 %, and yet more preferably less than 4%, relative to the total of asphalt plus all polymer modifiers.

[0018] In general, 0.1 to 40 % by weight, preferably 1 to 30 % by weight, and more preferably 1 to 10 % by weight of a vinyl acetate / ethylene copolymer containing more than 50 weight percent vinyl acetate-derived moieties is added, in each case based on the total weight of the performance grade asphalt composition, based on the amount of asphalt and polymer modifiers, e.g. not including fillers or aggregate.

[0019] In general, the vinyl acetate/ethylene (VAE) copolymers have a vinyl acetate content of more than 50 % by weight, preferably > 52% by weight, more preferably > 55% by weight, and an ethylene content of less than 50% by weight, preferably 1 to 45 % by weight, and optionally contain residues further monomers copolymerizable therewith, in each case based on the total weight of the monomer mixture, wherein the figures in % by weight totaling 100 %.

[0020] Suitable further vinyl ester monomers copolymerizable with ethylene and vinyl acetate include vinyl higher esters, for example those of carboxylic acids having 3 to 15 C atoms. Suitable further monomers from the group of acrylic esters or methacrylic esters include, for example, esters of unbranched or branched alcohols having 1 to 15 C atoms. Preferred vinylaromatic further monomers are styrene, methylstyrene, and vinyltoluene. A preferred vinyl halide further monomer is vinyl chloride. The preferred olefin further monomers are propylene and butylene, and the preferred dienes are 1,3 -butadiene and isoprene.

[0021] Optionally, it is also possible for 0.1 to 10 % by weight of auxiliary monomers to be copolymerized, based on the total weight of the monomer mixture. Preference is given to using 0.1 to 5 % by weight of optional auxiliary monomers. Examples of optional auxiliary monomers are ethylenically unsaturated monocarboxylic and dicarboxylic acids, ethylenically unsaturated carboxamides and carbonitriles, and also maleic anhydride, and ethylenically unsaturated sulfonic acids and their salts. Other examples of optional auxiliary monomers are precrosslinking comonomers such as polyethylenically unsaturated comonomers, or post crosslinking comonomers, examples being N-methylolacrylamide (NMA), and N-methylolmethacrylamide (NMMA). Also suitable are epoxide-functional comonomers such as glycidyl methacrylate and silicon-functional comonomers, such methacryloyloxypropyltrialkoxysilanes, and vinyltrialkoxysilanes.

[0022] Preference is given to copolymers of 60 to 99 % by weight of vinyl acetate with 1 to 40 % by weight of ethylene; copolymers of more than 50 % by weight of vinyl acetate with 1 to 40 % by weight of ethylene and one or more further comonomers from the group of the vinyl esters having 1 to 12 carbon atoms in the carboxyl radical, such as vinyl propionate, vinyl laurate, and vinyl esters of alpha-branched carboxylic acids having 5 to 12 carbon atoms, such as VeoVa9^R and VeoVal0^R; copolymers of more than 50 % by weight of vinyl acetate, 1 to 40 % by weight of ethylene and one or more further comonomers from the group of (meth)acrylic esters of unbranched or branched alcohols having 1 to 15 carbon atoms, especially methyl methacrylate, methyl acrylate, n-butyl acrylate and 2-ethylhexyl acrylate; where the copolymers may each also contain the auxiliary monomers mentioned in the amounts mentioned, and the figures in % by weight total 100 %.

[0023] The monomer selection and the selection of the weight fractions of the comonomers are preferably performed so as to result in glass transition temperatures, T_g, ranging from -20°C to +40°C, more preferably -20°C to +30°C, and most preferably -l0°C to +20°C. The T_g of the polymers can be determined in a known way by means of Differential Scanning Calorimetry (DSC, DIN EN ISO 11357-1/2), for example determined with a calorimeter DSC from Mettler-Toledo, with a heating rate of 10 K/min as midpoint temperature. The T_g may also be calculated approximately in advance using the Fox equation. According to Fox T. G., Bull. Am. Physics Soc. 1, 3, page 123 (1956) the following is the case: l/T_g = xi/T_gi + x₂/T_g2 + ... + Xn/Tgn, where x_n stands for the mass fraction (wt.%/l00) of the monomer n, and T_gn is the glass transition temperature, in degrees Kelvin, of the homopolymer of the monomer n. T_g values for homopolymers are listed in Polymer Handbook 2nd Edition, J. Wiley & Sons, New York (1975). [0024] The polymers are generally prepared in an aqueous medium and preferably by the emulsion or suspension polymerization process, as described for example in WO 2010/057888 Al. The polymers in that case are obtained in the form of aqueous dispersions. In the polymerization, it is possible to use the customary protective colloids and/or emulsifiers, as described in WO 2010/057888 Al. The polymers in the form of aqueous dispersions will be dried in a conventional manner. In a preferred embodiment the polymers may be converted to water- dispersible polymer powders by the spray-drying process, as described in WO 2010/057888 Al, for example. In that case it is usual to add a drying aid in a total amount of 3 to 30 % by weight, based on the polymeric constituents of the dispersion.

[0025] The vinyl acetate/ethylene polymers may also be prepared by other methods, including solution polymerization, or bulk (neat) polymerization. Polymers prepared by solution or bulk polymerization are preferably supplied in a form having a relatively high surface area. For this purpose, for example, the polymers may be extruded into pellets or granules by conventional processes or otherwise prepared in small particle sizes.

[0026] The use of water-dispersible vinyl acetate / ethylene polymer powders is highly preferred. Water-dispersible polymer powders are generally obtained by drying the corresponding aqueous polymer dispersions in the presence of a drying aid (generally a protective colloid) and an antiblocking agent. The protective colloid serves as an encasing for the polymer and functions to prevent irreversible aggregation or coalescence of the polymer particles during the course of the drying operation. The protective colloid redissolves when the polymer powder is dispersed in water, and it has the effect that the polymer particles are again present in the aqueous redispersion with the particle size of the starting dispersion. (TIZ-Fachberichte, 1985, Vol. 109 (9), 698).

[0027] The polymer powders are commercially available, for example as Vinnapas^® and

ETONIS^® dispersion powders of Wacker Chemie AG.

[0028] The total of all polymer modifiers is preferably less than 10 weight percent, based on the total weight of unmodified asphalt and all polymer modifiers, more preferably less than 7 weight percent, yet more preferably less than 6 weight percent, and most preferably less than 5 weight percent, each of these also complying with the weight ratios of vinyl acetate/ethylene copolymer and S-polymer discussed previously. Through judicious use of the amounts of these two polymers, optionally in conjunction with further polymers or modifying oils, the UTI is preferably increased by at least two performance grades, for example one performance grade on the high end of the performance grade, and one on the low end. An example would be the modification of an asphalt with a PG 64-22, which, after modification, has a PG 70-16 (one performance grade limit improvement of UTI) or PG 76-10 (two performance grade limit improvement).

[0029] The selection of other additives and the proportion thereof is state of the art and is well-known to the skilled worker. These additives, include, but not limited to, hydrocarbon resins, pitch pine, rosin esters, extender oils, naphthalenic or paraffinic oils, acids such as phosphoric or polyphosphoric acid, polyamines, stabilizers, solvents, waxes, etc., or combinations thereof. Further, additives which may be added are fillers like limestone, chalk, graphite, talc, fly ash, quartz powder, glass fiber or cellulose fiber. The selection of filler and the amount of filler used in the polymer-modified asphalt composition depends on the intended use of the polymer-modified asphalt composition and is well known to the skilled worker.

[0030] Further examples of conventional additives may include anti-aging agents, corrosion inhibitors, biocides, pigments or processing aids, such as, for example, lubricants. The general amount is defined by both the application and the use of other polymers, including but not limited to S-polymers, and is well known to the skilled worker.

[0031] The preparation of the performance grade asphalt composition has no special limitations and is carried out in the manner known from the prior art. Usually, all components are intensively mixed in an agitated vessel at elevated temperatures of 175 °C to l95°C. The material obtained is then further processed depending on the intended use. The blend may be processed, for example by calendaring or other suitable technologies such as coating, grinding, lubricating, spreading, laminating, extrusion etc.

[0032] The performance grade asphalt composition can be used for the production of asphalt for paving, waterproofing sheets, sealing, drainage, roofing, crack propagation prevention, etc. [0033] The upper and lower Performance Grade Temperatures of the unmodified asphalt is known or can easily be measured. Following addition of S-polymer modifier, these temperatures can be remeasured, and an amount of VAE copolymer added to lower the lower performance grade temperature. The amount may vary from case to case, and generally cannot be predicted beforehand, for example, due to differences in asphalt composition, the nature and amount of S- polymer, and the presence or absence of other modifiers, but once established, can be used without further measurements, if desired. The amount of VAE polymer added to improve the EGTI, relative to the amount of S-polymer added, may advantageously range on a weight basis, from 0.5: 10 to 10: 1, more preferably 1 : 10 to 5: 1, and yet more preferably 2:10 to 1 : 1. Amounts in a ratio of 2: 10 to 6: 10 have proven to be particularly useful. An amount of VAE polymer which is sufficient to increase the EGTI may be termed an“effective amount” herein.

[0034] The process of the invention has the advantage that it is easily implemented, with readily available materials. It has the further advantage of maintaining a higher PG upper limit due to the addition of an S-polymer to the asphalt, while lowering the PG lower limit, thus increasing the UTI. Asphalt-bound products prepared from such modified asphalt, e.g. roads, roofing membranes and shingles, and other products, have a higher use temperature, but are also more resistant to cracking at low temperatures. The process has the further advantage that low amounts of polymer modifier are effective, increasing the cost-effectiveness of polymer modification.

[0035] Thus, the invention also pertains to a method of increasing the useful temperature interval (“UTF) of asphalt, the method comprising establishing the PG of the asphalt, as defined by the upper and lower temperature ratings; adding S-polymer to the asphalt to increase the upper PG temperature; measuring the new PG upper temperature and new PG lower temperature; adding an amount of VAE polymer to the S-polymer modified asphalt and measuring at least the lower PG temperature rating, and if the amount of VAE polymer added is insufficient to lower the lower PG temperature to a value lower than that achieved by addition of the S-polymer, to further lower the lower PG temperature value by adding further VAE copolymer. The PG of the unmodified asphalt may be established by requiring a supplier to furnish asphalt of a defined PG grade, or by measurement prior to modification. Examples and Comparison Examples

[0036] An asphalt cement PG64-22 was used and modified with polymer, wherein the total polymer modification was 4.5 % by weight, based on the total weight of the polymer- modified asphalt composition (Table 3). The VAE polymer powders were used in combination with a standard linear SBS (tradename, provider Calprene 501), wherein the linear SBS and a polymer powder (polyvinyl alcohol stabilized vinyl acetate/ethylene copolymer of Wacker Chemie AG) was used at three different proportions by weight, based on the total weight of the VAE polymer and S-polymer in the polymer-modified asphalt. The grading parameters from tests, such as G*/sin5 on the original and RTFO aged asphalt blends, G*.sin5 after PAV, and BBR Stiffness and m-value after PAV were evaluated per ASTM test methods described above, and properties of the inventive polymer powder modified blends were compared to the SBS linear and neat asphalt.

[0037] Table 1 : Asphalt Blends of Example 1

11

[0038] Table 2: Properties of Asphalt Blends of Example 1

[0039] As can be seen, addition of S-polymer alone is useful to raise the upper PG temperature, but also raises the lower PG temperature. An amount of VAE polymer which constitutes only 25 wt. % of total polymer modifier lowers the lower PG value to that of unmodified asphalt, without affecting the upper PG limit. Larger relative amounts of VAE polymer are also useful, and may be effective to decrease the lower PG value to below that of unmodified asphalt.

[0040] While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.

Claims

WHAT IS CLAIMED IS:

1. A process for the production of a polymer modified asphalt binder with a broadened useful temperature interval (“UTF), comprising: a) providing an unmodified asphalt having a first performance grade upper limit and a first performance grade lower limit as defined by ASTM-D 6373-16, the difference between the first performance grade upper limit and the first performance grade lower limit defining the UTI; b) adding a sufficient quantity of an S-polymer as a first polymer modifier, but in an amount less than 6 weight percent based on the total weight of the asphalt and the S polymer, to increase the first performance grade upper limit to a second performance grade upper limit which is at least one grade higher than the first performance grade upper limit, and which raises the first performance grade lower limit; c) adding a quantity of a vinyl acetate/ethylene copolymer containing more than 50 weight percent vinyl acetate-derived moieties which does not lower the second performance grade upper limit to an extent that the second performance grade upper limit falls in a lower performance grade class than the second performance grade upper limit, and is sufficient to lower the second performance grade lower limit by at least one performance grade to form a polymer modified asphalt having a performance grade upper limit higher than said first performance grade upper limit, and a performance grade lower limit lower than said second performance grade lower limit, the weight ratio of said vinyl acetate/ethylene copolymer to S-polymer being in a weight ratio of from 0.5: 10 to 10: 1; and d) adding a sufficient quantity of VAE wherein the lower grade is unaltered.

2. The process of claim 1, wherein the weight percentage of the total of S- polymer and vinyl acetate/ethylene copolymer is less than 6 weight percent based on the total weight of asphalt, S-polymer, and vinyl acetate/ethylene copolymer.

3. The process of claims 1 or 2, wherein the weight percentage of the total of S-polymer and vinyl acetate/ethylene copolymer is less than or equal to 5 weight percent based on the total weight of asphalt, S-polymer, and vinyl acetate/ethylene copolymer.

4. The process of any of claims 1-3, wherein the amount of S-polymer added is 4 weight percent or less based on the weight of S-polymer plus unmodified asphalt.

5. The process of any of claims 1-4, wherein the vinyl acetate/ethylene copolymer contains > 55 wt. % vinyl acetate and from 1 to 45 weight percent ethylene.

6. The process of any of claims 1-5, wherein the vinyl acetate/ethylene copolymer comprises a water-dispersible polymer powder.

7. The process of claim 6, wherein the water-redispersible polymer powder comprises polyvinyl alcohol as a drying aid.

8. The process of any of claims 1-7, wherein the vinyl acetate/ethylene copolymer is present in a weight ratio with respect to the S-polymer of 2: 10 to 6: 10.

9. The process of any of claims 1-7, wherein the amount of vinylacetate/ethylene copolymer added is sufficient to reduce the second performance grade lower limit to below the first performance grade lower limit.

10. The process of any of claims 1-9, wherein the UTI is increased by at least two performance grades as compared to the unmodified asphalt.

11. The process of any of claims 1-10, wherein the UTI is increased by at least three performance grades as compared to the unmodified asphalt.

12. A method for formulating an asphalt composition to extend the UTI for the composition as compared to unmodified asphalt, comprising: establishing the PG of the unmodified asphalt, as defined by the upper and lower PG temperature ratings; adding S-polymer to the asphalt to increase the upper PG temperature; measuring the new PG upper temperature rating and new PG lower temperature rating in accordance with ASTM-D; adding an amount of VAE polymer to the S-polymer modified asphalt and measuring at least the lower PG temperature rating, and if the amount of VAE polymer added is insufficient to lower the lower PG temperature to a value lower than that of the S-polymer to further lower the lower PG temperature rating by adding further vinyl acetate/ethylene copolymer.

13. The method of claim 13, wherein the EGTI is broadened by more than two performance grades.