Modified asphalt compositions

Abstract

A modified asphalt composition is provided comprising at least one plastomer, at least one elastomer, and asphalt. More specifically, a modified asphalt composition is provided comprising an oxidized polyethylene, a styrene-butadiene-styrene block copolymer, and asphalt. A hot mix asphalt composition is also provided comprising the modified asphalt composition and aggregate. Processes for producing the modified asphalt composition and the hot mix asphalt composition is also provided as well as articles produced from these inventive compositions.

Description

wherein each of R₁ and R₂ denotes a saturated or unsaturated, monovalent C₁-C₂₀ hydrocarbon radical or R₁ and R₂ are joined together to form a saturated or unsaturated, divalent C₂-C₂₀ hydrocarbon radical forming a ring with the other groups of atoms which are associated in the formula. R₃ is a saturated or unsaturated, divalent C₁-C₂₀ hydrocarbon radical. The —(S)_v—groups denote divalent groups each made up of v sulfur atoms. It is possible that the number of sulfur atoms, v, for each of these groups can differ. The number of sulfur atoms, v, denote integers ranging from about 1 to about 6. Preferably, at least one of the —(S)_v— groups has at least two or greater sulfur atoms. In the group —[R₃—(S_v)_w]—, w denotes an integer having values from 0 to about 10.

In the abovementioned formula, the monovalent C₁-C₂₀ hydrocarbon radicals, R₁ and R₂ and the divalent C₁-C₂₀ hydrocarbon radical, R₃, are chosen especially from aliphatic, alicyclic, or aromatic radicals. When the radicals R₁ and R₂ are joined together to constitute a divalent C₁-C₂₀ hydrocarbon radical forming a ring with the other groups of atoms associated in the formula, the divalent radical can be similar to the radical R₃ and may also be of the aliphatic, alicyclic or aromatic type. Preferably, R₁ and R₂ are identical and chosen from C₁ to C₂₀ alkyl radicals, such as, but not limited to, ethyl, propyl, hexyl, octyl, nonyl, decyl, linear dodecyl, tert-dodecyl, hexadecyl, octadecyl, and C₆-C₂₀ cycloalkene or arylene radicals, expecially phenylene, toluene, and cyclohexene.

Examples of polysulfides include, but are not limited to, dihexyl disulfide, dioctyl disulfide, didodecyl disulfide, di-tert-dodecyl disulfide, dihexadecyl disulfide, dihexyl trisulfide, dioctyl trisulfide, dinonyl trisulfide, di-tert-dodecyl trisulfide, dinonyl trisulfide, di-tert-dodecyl trisulfide, dihexadecyl trisulfide, dihexyl tetrasulfide, dioctyl tetrasulfide, dihexadecyl tetrasulfide, dioctyl tetrasulfide, dinonyl tetrasulfide, di-tert-dodecyl tetrasulfide, dihexadecyl tetrasulfide, dihexyl pentasulfide, dioctyl pentasulfide, dinonyl pentasulfide, di-tert-dodecyl pentasulfide, dihexadecyl pentasulfide, diphenyl trisulfide, dibenzyl trisulfide, diphenyl tetrasulfide, ortho-tolyl tetrasulfide, dibenzyl tetrasulfide, dibenzyl pentasulfide, diallyl pentasulfide, tetramethyltetrathiane, and mixtures thereof.

Any peroxide known in the art capable of crosslinking with the elastomer of this invention can be utilized. Examples of such peroxides include, but are not limited to, hydroperoxides, dialkyl peroxides, peroxydicarbonates, diacyl peroxides, peroxyesters, and others.

Any transition metal compound known in the art capable of crosslinking with the elastomer of this invention can be utilized. Examples of such transition metal compounds include, but are not limited to, zinc compounds, such as, zinc oxide; nickel compounds, such as nickel(II) chloride; and titanium compounds, such as, titanium halides and titanium hydroxides. Other active metal compounds known to react with unsaturation can be used.

Although not necessary in this invention, if desired, crosslinking accelerators can be utilized. Crosslinking accelerators are disclosed in U.S. Pat. No. 5,314,935, which is herein incorporated by reference beginning in column 7, line 5 through column 8, line 58.

The modified asphalt composition can also comprise other additives known to those skilled in the art. Additives include nitrogen compounds of amine or amide which are used as promoters of adhesion for the asphalt and the elastomer.

The modified asphalt compositions can be used to form any suitable articles. More particularly, the modified asphalt compositions are used to form road pavement surfaces. To form a road pavement, the modified asphalt composition is applied to a surface, such as earth that has preferably been leveled, using any method, including any method commonly used in the road paving industry. While the modified asphalt composition provides excellent physical characteristics for road paving applications, these mixtures may also be used for other construction purposes, such as roofing applications.

In another embodiment of this invention, a process is provided to produce the modified asphalt composition. The process comprises contacting at least one plastomer, at least one elastomer, asphalt, and optionally at least one crosslinking agent. The contacting can be conducted by any method known in the art. Generally, the asphalt is heated to its molten state and the plastomer, elastomer, and optionally the crosslinking agent are then added and mixed into the asphalt to produce the modified asphalt composition. Preferably, the plastomer and elastomer are added simultaneously. Most preferably, the elastomer, plastomer, and crosslinking agent are added simultaneously.

In another embodiment of this invention, a process for producing a hot mix asphalt composition is provided. The process comprises contacting at least one plastomer, at least one elastomer, asphalt, aggregate, and optionally at least one crosslinking agent.

The term “aggregate” is a collective term denoting any mixture of such materials including, but not limited to, sand, gravel, and crushed stone, and the like used with asphalt. The type of aggregate and the amounts used vary depending on the use of the hot mix asphalt composition.

In yet another embodiment, a process for producing a modified asphalt composition is provided. The process comprises: 1) contacting at least one plastomer and at least one elastomer in an extruder zone to produce a plastomer/elastomer pellet; 2) adding the plastomer/elastomer pellet and optionally at least one crosslinking agent to at least one molten asphalt to produce a modified asphalt mixture; and e) mixing the modified asphalt mixture in a mixing zone to distribute the plastomer, elastomer, and optionally the crosslinking agent to produce the modified asphalt composition. Preferably, the plastomer/elastomer pellet and crosslinking agent are added simultaneously.

In still another embodiment of this invention, a process for producing a modified asphalt composition is provided. The process comprises: 1) contacting at least one plastomer and at least one elastomer in an extruder zone to produce a plastomer/elastomer pellet; 2) contacting at least one plastomer and at least one crosslinking agent in an extruder zone to produce a plastomer/crosslinker pellet; 3) adding the plastomer/elastomer pellet and the plastomer/crosslinker pellet to at least one molten asphalt in a mixing zone to produce a polymer modified asphalt mixture; and 4) mixing the modified asphalt mixture in the mixing zone to distribute the plastomer, elastomer, and crosslinking agent to produce the modified asphalt composition. Preferably, the plastomer/elastomer pellet and the plastomer/crosslinker pellet are added simultaneously.

The extruder zone comprises at least one extruder. The plastomer and elastomer are heated in the extruder zone to a sufficient temperature so they can be adequately mixed.

The mixing zone comprises any equipment suitable for mixing the asphalt, plastomer, elastomer, and optionally the crosslinking agent. Suitable equipment includes, but are not limited to, low shear mixing equipment and high shear mixing equipment.

By adding the plastomer, elastomer, and crosslinking agent in pellet form to the molten asphalt, dust and fumes can be significantly reduced.

An advantage of the use of the plastomer is that when the polymers are added to asphalt, the viscosity of the mixture is only slightly increased over the viscosity of asphalt alone. By increasing the viscosity only slightly, the mixture exhibits good hot-mix workability and no observable separation. This aids also in the mixing of the elastomer, which is typically very difficult to mix. Furthermore, the plastomers exhibit dispersibility with a large number of asphalts, resulting in mixtures that are storage stable, with no polymer phase separation.

The present invention will be more readily understood by reference to the following examples. There are, of course, many other forms of the invention which will become obvious to one skilled in the art, once the invention has been fully disclosed, and it will accordingly be recognized that these examples are given for the purpose of illustration only and are not to be construed as limiting the scope of the invention in any way.

EXAMPLES

Table I lists the test methods used to characterize the modified asphalt compositions of the examples.

TABLE I

Test Name                        Test Method

Performance Graded Asphalt Binders AASHTO MP1
Kinematic Viscosity 135° C.      ASTM D 2170
Absolute Viscosity 60° C.        ASTM D2171
Toughness and Tenacity           ASTM D 5801
Ring and Ball Softening Point    ASTM D-36
Dynamic Shear Rheometer (DSR)    AASHTO TP5
Penetration                      ASTM D 5
Compatiblity/Separation          ASTM D 5976
Elastic Recovery                 ASTM D 6084
Rolling Thin Film Oven Test (RTFO) ASTM D 2872
Pressure Aging Vessel            ASTM D 6521
Bending Beam Rheometer (BBR)     ASTM D 6648
Force Ratio                      AASHTO T-300

One criterion for asphalt performance is the Superpave™ Performance Graded (PG) Binder Specification. These parameters, which indicate the visco-elastic and service performance related properties of asphalt compositions, were developed to classify materials based upon performance. The PG parameters measure the properties between the low temperature service rating for the material (generally based upon embrittlement cracking) and the high temperature service properties for the material (generally based upon heat softening) to determine a service temperature range. The greater the PG temperature range rating, the greater the service range for the material.

Another criterion to evaluate asphalt performance is a group of historical conventional protocols such as Softening Point, Penetration, Force Ratio, Elastic Recovery, Compatibility, Toughness, and Tenacity. These tests assess a variety of physical properties that through historical use and correlation to actual pavement performance are used to specify an asphalt by various agencies in addition to the Superpave criteria.

Inventive Examples 1-6, 8-14 and 16 and Comparative Examples 7 and 15 in Tables 2 and 3, a PG 64-22 asphalt was modified. The PG 64-22 was heated to about 370-380° F. to produce a molten asphalt. The Preblend Additives 1 and 2 and the Crosslinker Preblend Addtive were added in pellet form to the molten asphalt, and these additives were blended into the asphalt at high shear for about 1 hour followed by paddle agitation (stirring) for two hours at 370-380° F. This procedure was necessary to adequately blend the SBS block copolymer into the asphalt in Comparative Examples 7 and 15 and Inventive Examples 8 and 16. As can be seen from the data, this 3 hour period of mixing is not necessary when adding preblended elastomer and plastomer at the same time.

Preblend Additive 1 in Table 2 consisted of a 50/50 by weight blend of Wingflex® 411 SBS block copolymer commercially available from Goodyear and oxidized polyethylene available commercially as Epolene® E-20 wax from Eastman Chemical Company. Comparative Example 7 and Inventive Example 8 utilized Kraton® D1184 SBS block copolymer. The Crosslinker Preblend Additive 1 in Table 2 and Table 3 is 25% by weight sulfur in Epolene® E-20 oxidized polyethylene.

Preblend Additive 2 in Table 3 consisted of a 25/75 by weight blend of Wingflex® 400 SBS block copolymer commercially available from Goodyear and oxidized polyethylene available commercially as Epolene® E-20 wax from Eastman Chemical Company. Comparative Example 15 and Inventive Example 16 utilized Kraton® D1184 SBS block copolymer.

The PG Rating and conventional data displayed in Tables 2 and 3 indicates the inventive modified asphalt compositions have comparable performance grades and equivalent or improved conventional properties as compared to that of an asphalt containing a similar concentration of elastomer (e.g. SBS block copolymer).

The presence of the plastomer allows a more efficient use of the elastomer in the asphalt to achieve improved properties without detrimental effects such as incompatibility and high process viscosities associated with elastomer usage at equivalent dosages.

Comparative Examples 7 and 8

In Examples 7 and 8, modification of the PG 64-22 asphalt with 4% Kraton® D 1184 SBS block copolymer increased the PG grade by 2 grades to a PG 76-22 grade. In Example 8, the addition of a small amount of crosslinking agent only slightly increased the performance grade of the modified asphalt. However, the Crosslinker Preblend Additive 1 (Example 8) was not added with the Kraton® SBS rubber, but was added after the rubber had dissolved. It took the full three hours for the Kraton® SBS rubber to disperse in the PG 64-22 asphalt. It was only after the Kraton® SBS rubber had dispersed that the Crosslinker Preblend Additive 1 (oxidized polyethylene and sulfur) was added.

Example 7 shows that 4% Kraton® SBS rubber was not very compatible with asphalt in that the softening point after 48 hours at 163° F. was very different at the top (198° F.) and at the bottom (138° F.) of the aged sample. This was not the case for the inventive examples. This is a common problem with elastomer use and most host asphalts. Incompatibility, also referred to as separation, can typically be caused by a compositional deficiency in the asphalt for elastomer modification. When separation occurs, the ‘dissolved’ polymer phase can separate and rise to the surface of the blend and the asphalt's higher molecular weight component fractions, asphaltenes, can precipitate from the asphalt matrix and sink to the bottom of the blend. This often results in process difficulties at a modified asphalt producing facility. This can be followed by process problems at the hot asphalt mix manufacturing facility, and if incorporated into the pavement structure, pavements that under perform. Compatibility is a key property and is incorporated in nearly all specifications involving asphalt modifiers world wide.

Inventive Examples 1-6 and 9-14

Inventive Examples 1-6 of Table 2 and 9-14 of Table 3 depict the benefits of modification of asphalt with PreBlend Additives 1 and 2, which are further enhanced by co-use of Crosslinking Preblend Agent 1. These examples, inclusive, displayed separation values of<2° F., as determined by the Ring and Ball Softening Point. It should be noted the addition of Preblend Additives 1 and 2 in pellet form had a significant improved effect on separation, which may not be realized if the components of the Preblend Additives (oxidized polyethylene and SBS block copolymer) were added separately. When an asphalt and additive system are prone to separation, the asphalt may be remedied through the use of ancillary technologies such as aromatic oil addition, source asphalt blending, use of lower viscosity asphalt, which requires more elastomer to achieve the desired high temperature requirements. All of these processes are costly and time consuming.

Inventive Examples 3 and 5 of Table 1 indicate the benefit of inclusion of the proper dosage of Crosslinking Preblend Agent 1 with Preblend Additive 1 on Toughness and Tenacity, a measure of the strength under strain of the modified asphalt. These data are compared with Inventive Examples 1 and 2 where sulfur was not used for crosslinking. Toughness and Tenacity is a parameter used by various State DOTs in their modified asphalt specifications to assure the correct type and proper quantity of elastomer is used to meet the modified asphalt's specified requirements.

Similar improvements are witnessed in the Elastic Recovery properties of Inventive Examples 3 and 5. The elastic recovery (%) ranged from 66-83 for the examples involving crosslinking, while Examples 1 and 2 had a elastic recovery ranging from 41-44.

Inventive Examples 1-6 and 9-14 of Tables 2 and 3 display substantially reduced process viscosities when compared to Comparative Examples 7 and 15 using Kraton® D 1184 alone as a modifier. When using Preblend Additive 1 containing a 50/50 blend of SBS block copolymer and oxidized polyethylene, the viscosities (centistokes) at 135° C. for inventive examples 1-6 ranged from 648 to 1,150 centistokes compared to comparative example 7 where the viscosity was 1,256 centistokes. When using Preblend Additive 2 containing a 25/75 blend of SBS block copolymer and oxidized polyethylene, the viscosity of the Inventive Examples 9-14 ranged from 540 to 802 centistokes, while Comparative Example 15 using only SBS block copolymer as a modifier had a viscosity of 988 centistokes. High process viscosities present problems to the contractor during mixing of the modified asphalt composition with the aggregates and subsequent compaction of the modified asphalt composition with aggregate.

Inventive Examples 2 and 5

Examples 2 and 5 in Table 1 correspond to the Comparative Example 7 and Inventive Example 8 in that each contains 96% asphalt. Example 8 is an inventive example, but is used here for comparative purposes to show the advantage of addition of the elastomer in a pellet with the oxidized polyethylene. In addition, Inventive Example 5 and Comparative Example 7 both contain 0.5% of Crosslinker Preblend Additive 1. Both of the inventive modified asphalt compositions upgraded the asphalt to the same PG 76-22 grade as the Comparative Example 7 and Inventive Example 8, but at half of the SBS block copolymer level as the comparative modified asphalt compositions. In addition, in Inventive Example 5, the Preblend Additive 1 in pellet form and the Crosslinker Preblend Additive in pellet form were added at the same time as a single blend of pellets. These additives had completely dispersed into the asphalt in 1.5 hours which was approximately one half of the time it took the Kraton® SBS block copolymer to disperse. The compatibility of the modified asphalt composition was greatly improved when the inventive additives were used. The Ring and Ball softening point differential on the aged samples after 48 hours at 163° F. was only 1 or 2 degrees. Thus, the combination of a plastomer with the elastomer allowed a much more efficient usage of the elastomer in the asphalt matrix which resulted in the same degree of reinforcement of the asphalt but at half the level of elastomer.

Inventive Example 6

The asphalt was modified by simultaneously adding 4% by weight Preblend Additive 1 and 1% by weight Crosslinker Preblend Additive 1 with the weight percent based on the weight of the modified asphalt composition at 370-380° F. and stirring for 1.5 hours. As shown in Table 2, the asphalt PG grade increased by +3 grades to PG 82-22 without the loss of low temperature properties.

TABLE 2
Data for examples 1 to 8
	I-1	I-2	I-3	I-4	I-5	I-6	C-7	I-8
Ingredient	Specification	Weight Percent
Asphalt, West Coast			97	96	97	97	96	96	96	96
Blend PG 64-22,
Preblend Additive 1			3	4	3	3	4	4	—	—
Crosslinker Preblend			0	0	0.5	1	0.5	1	0	0.5
Additive 1
Kraton ® D 1184 SBS			—	—	—	—	—	—	4	4
PROPERTIES:
Original Blend
Viscosity @ 135° C.,	3,000	max.	648	709	721	928	890	1,150	1,256	1,574
cSt
Viscosity @ 60° C. P			6,920	10,046	13,409	19,010	33,518	54,703	20,164	29,805
DSR @ 88° C. kPa	1.0	min.	—	—	—	—	—	0.687	—	—
(G*/sin d)
DSR @ 82° C., kPa			—	0.621	—	0.986	0.829	1.117	0.764	0.932
(G*/sin d)
DSR @ 76° C., kPa			0.935	1.071	0.976	1.657	1.361	1.826	1.286	1.519
(G*/sin d)
DSR @ 70° C., kPa			1.716	1.777	1.655	2.823	2.25	2.768	2.34	2.729
(G*/sin d)
Penetration @ °25 C.			46	45	42	38	43	40	44	41
dmm
Softening Point, ° F.			134.3	137.3	151	162.5	170	184	153.5	164.5
Force Ratio @ °4 C.,	0.30	min.	0.175	0.194	0.252	0.147	0.337	0.283	0.25	0.418
f2/f1 (0.55 cm/min,
24 cm)
Toughness & Tenacity @ 25° C.
Toughness, in-lbs.	110	min.	117.8	140.8	190.3	135.6	232.3	164	199.3	133.8
Tenacity, in-lbs.	75	min.	53	68.7	116.8	49.2	168	97.7	128.9	172
Compatibility @
163° C./48 hrs
Top ⅓ Softening			136.5	143	142.5	155	164	178	198	167
Point, ° F.
Bottom ⅓ Softening			136	144	143	157	166	180.8	138	170
Point, ° F.
Difference, ° F.	4.0	max.	0.5	1	0.5	2	2	2.8	60	3
Elastic Recovery,	60	min.	41	44	74	66	83	82	82	90
% @ 25° C.
RTFOT Residue
Mass Loss, %	0.5	max.	0.229	0.229	0.199	0.142	0.144	0.114	0.171	0.142
DSR @ 88° C. kPa	2.2	min.	—	—	—	—	—	1.245	—	—
(G*/sin d)
DSR @ 82° C. kPa			—	—	—	1.488	1.371	2.289	1.341	1.547
(G*/sin d)
DSR @ 76° C. kPa			1.508	2.061	1.577	2.639	2.323	3.854	2.598	2.623
(G*/sin d)
DSR @ 70° C. kPa			2.592	3.851	2.904	4.847	4.287	6.05	5.01	4.798
(G*/sin d)
Elastic Recovery,	50	min.	54	57	63	53	70	70	73	84
% @ 25° C.
PAV Residue (100 C., 300 psi, 20 hours)
DSR @ 28° C.,	5,000		3,923	4,023	3,458	3,972	4,896	3,500	3,597	3,973
G*.sin d, kPa
DSR @ 25° C.,		max.	5,677	5,733	5,107	5,595	6,929	5,016	5,150	5,684
G*.sin d, kPa
BBR @ −12° C.,	300	max.	231	233	198	240	216	229	210	192
Stiffness, MPa
m value	0.300	min.	0.308	0.306	0.318	0.308	0.328	0.317	0.307	0.331
BBR @ −18° C.,	300	max.	441	457	415	485	419	421	401	374
Stiffness, MPa
m value	0.300	min.	0.235	0.235	0.242	0.235	0.251	0.244	0.236	0.256
Performance Grade			70-22	76-22	70-22	76-22	76-22	82-22	76-22	76-22
“True” Performance			75-22	76-22	75-23	81-22	80-24	83-23	79-22	81-24
Grade
Effective Temperature	MP	1	97	98	98	103	104	106	101	105
Range, ° C.
Grade Change			+1	+2	+1	+2	+2	+3	+2	+2
Note:
I-1 through I-6 and I-8 are inventive examples.
C-7 is a comparative example.

Inventive Examples 9-14, and 16

In Inventive examples 9-14 and 16 and Comparative Example 15 of Table 3, a PG 64-22 asphalt was modified by blending the components at high shear for 1 hour followed by paddle agitation (stirring) for two hours at 370-380° F. The procedure was necessary to adequately blend the SBS block copolymer into the asphalt in example numbers 15 and 16. Preblend Additive 1 in Table 3 consisted of a 25/75 blend of Wingflex® 400 SBS block copolymer (Goodyear) and Epolene® E-20 oxidized polyethylene from Eastman Chemical Company. The Comparative Example 15 and Inventive Example 16 utilized Kraton® D1184 SBS rubber. The Crosslinker Additive 1 in Table 3 is 25% sulfur in Epolene® E-20 oxidized polyethylene.

Inventive Example 9 and Comparative Example 15 both have 3% by weight modifier added to the asphalt. It is expected that Comparative Example 15 would have greater toughness and tenacity than Inventive Example 9 since it contains 3 times the quantity of elastomer. The Preblend Additive 2 contained a 25/75 blend of SBS block copolymer and oxidized polyethylene. It is not expected, however, that both modified asphalt compositions containing 3% modifier would have almost the exact PG grade for the modified asphalt composition. As shown in Table 3, the “True” Performance Grade for Inventive Example 9 was 74-21 compared to 75-22 for Comparative Example 15. These two examples suggest that the elastomer and plastomer combination allows much more effective use of the elastomer to upgrade the asphalt. The plastomer facilitates the dispersal and ordering of the asphalt matrix to more readily take advantage of the elastomeric properties imparted to the modified asphalt composition.

Inventive Examples 12 and 13 show that at either higher preblend additive levels or higher crosslinker preblend agent levels further improvement, as evidenced by a higher PG grade of the modified asphalt composition, is possible. However, SBS block copolymers tend to begin to have compatibility issues at these higher loadings

	Example #
	I-9	I-10	I-11	I-12	I-13	I-14	C-15	I-16
	Ingredient	Weight Percent
Asphalt, West Coast			97	96	97	97	96	96	97	97
Blend PG 64-22,
Preblend Additive 2			3	4	3	3	4	4	—	—
Crosslinker Preblend			—	—	0.5	1	0.5	1	—	0.5
Additive 1
Kraton ® D 1184 SBS			—	—	—	—	—	—	3	3
PROPERTIES:
Original Blend	Spec.
Viscosity @ 135° C.	3,000	max.	540	548	609	619	660	802	988	1,037
C cSt
Viscosity @ 60° C. P			7,027	10,596	10,083	11,048	24,556	27,005	6,225	19,905
DSR @ 88° C. kPa			—	—	—	—	0.441	0.755	—	—
(G*/sin d)
DSR @ 82° C., kPa			—	0.723	—	0.866	1.003	1.378	—	0.677
(G*/sin d)
DSR @ 76° C., kPa			0.845	1.159	0.983	1.449	1.757	2.113	0.946	1.125
(G*/sin d)
DSR @ 70° C., kPa	1.0	kPa	1.528	1.993	1.85	1.827	—	3.357	1.746	1.937
(G*/sin d)
Penetration @ °25 C.,			47.3	45.3	44.5	44.1	36	38	44	43
dmm
Softening Point, ° C.			134.5	143	140	143.5	160.3	170	132	148
Force Ratio @ °4 C.,	0.300	min	0.113	0.13	0.106	Broke	0.145	Broke	0.223	0.375
f2/f1 (5 cm/min,
24 cm)
Toughness & Tenacity @ 25° C.
Toughness, in-lbs.	110	min.	90.84	93.48	93.81	84.26	110.1	95.85	183.8	265.1
Tenacity, in-lbs.	75	min.	26.11	29.29	27.04	15.33	35.26	17.85	102.29	191.5
Compatibility @
163 C./48 hrs
Top ⅓ Softening			137	147	140	144.5	152.5	161	136	155.5
Point, ° F.
Bottom ⅓ Softening			136	147	140	144.5	152.5	161.8	135	155.8
Point, ° F.
Difference, ° F.	4.0	max	1.0	0.0	0.0	0.0	0.0	0.8	1.0	0.3
Elastic Recovery,	60	min.	33.5	41	47.3	29.2	57	43	47.3	80.5
% @ 25 C.
RTFOT Residue
Mass Loss, %	0.5	max.	0.057	0.086	0.057	0.085	0.072	0.086	0.076	0.056
DSR @ 82° C. kPa			—	1.332	—	1.418	1.347	1.482	—	—
(G*/sin d)
DSR @ 76° C.			1.601	2.415	2.054	2.517	2.576	2.175	1.919	1.901
kPa (G*/sin d)
DSR @ 70° C. kPa	2.2	min.	3.23	4.47	3.749	3.32	—	4.48	3.856	3.53
(G*/sin d)
Elastic Recovery,	50	min.	41.5	47.8	43.8	32	51	36	66	77
% @ 25° C.
PAV Residue (100 C., 300 psi, 20 hrs)
DSR @ 31° C.,			3,195	3,023	3,153	3,167	3,190	2,912	2,634	2,074
G*.sin d, kPa
DSR @ 28° C.,			4,447	4,392	4,661	4,605	4,598	4,214	3,817	3,104
G*.sin d, kPa
DSR @ 25° C.,	5,000	max.	5,983	6,260	6,562	6,504	6,492	5,946	5,554	4,509
G*.sin d, kPa
BBR @ −06° C.,	300	max.	117	124	117	128	—	—	—	—
Stiffness, MPa
m Value	0.300	min.	0.344	0.345	0.343	0.344	—	—	—	—
BBR @ −12° C.,	300	max.	260	272	254	274	249	244	211	188
Stiffness, MPa
m Value	0.300	min.	0.298	0.297	0.302	0.304	0.301	0.301	0.309	0.332
BBR @ −18° C.,	300	max.	13	—	413	464	413	423	386	381
Stiffness, MPa
m Value	0.300	min.	—	—	0.244	0.245	0.246	0.246	0.248	0.266
Performance Grade			70-16	76-16	70-22	76-22	76-22	70-22	70-22	70-22
“True” Performance	M	320	74-21	78-21	75-22	80-22	82-22	84-22	75-22	74-24
Grade
Effective Temperature			95	99	97	101	104	106	97	101
Range, ° C.

Blending Improvements of Inventive Modified Asphalt Compositions

Table 5 is a mixing time table and shows the progress of the modified asphalt compositions of Table 3 while they were blended. A PG 64-22 apshalt was modified by blending the components shown in Table 3 at high shear for 1 hour followed by paddle agitation for two hours at 370-380° F. The procedure was necessary to adequately blend the SBS block copolymer into the asphalt in Comparative Example 7 and Inventive Example 8. It is clearly shown in Table 5 that the blend times for the Preblend Additive 1 was significantly shortened compared to the SBS block copolymer addition in Comparative Example 7. The Preblend Additive 1 was dissolved in the asphalt in approximately 30 minutes while the SBS block copolymer took at least 120 minutes to dissolve. This reduced blend time translates into shorter batch times and increased production rates. Thus, the Preblend Additive of Table 3 is readily soluble in asphalts at useful levels. This solubility also results in reduced tendency for the modifiers to separate upon storage.

TABLE 5
Ingredient	−1	−2	−3	−4	−5	−6	−7	−8
Asphalt, West Coast Blend	97	96	97	97	96	96	96	96
PG 64-22,
Preblend Additive 1	3	4	3	3	4	4	—	—
Crosslinker Preblend	0	0	0.5	1	0.5	1	0	0.5
additive 1
Kraton SBS D 1184	—	—	—	—	—	—	4	4
Mix/blend: appearance and
texture
initial, after Crosslinker Pb
A1 addition	small Undissolved particles	particles present
15 minutes	nearly all dissolved and dispersed	particles present
30 minutes	smooth and homogeneous	nearly dissolved
60 minutes	smooth and homogeneous	and dispersed
120 minutes	smooth and homogeneous	smooth homogeneous
Ease of blending	excellent	excellent	excellent	excellent	excellent	excellent	Good	Good
Separation/Film formation	No Visual
Draw Down, undispersed	all blends were smooth and homogeneous
polymer?

Claims

1. A modified asphalt composition produced by the process comprising:

1) contacting at least one plastomer and at least one elastomer to produce a pellet; and

2) adding said pellet to asphalt in a mixing zone to produce said modified asphalt composition.

2. A modified asphalt composition according to claim 1 wherein said oxidized polyethylene has at least one property in the following ranges: an acid number from about 0.1 to about 50, a needle penetration hardness less than about 50 dmm at 25° C., and a viscosity from about 1 to about 100,000 cP at 135° C.

3. A modified asphalt composition according to claim 1 wherein said oxidized polyethylene is a homopolymer having at least one of the following properties: a density from about 0.92 to about 1.1 g/cm³, a hardness less than about 1.5 dmm at 25° C., an acid number from about 5 to about 41, and a viscosity from about 800 to about 8,000 cP at 125° C.

4. A modified asphalt composition according to claim 1 wherein said elastomer is a synthetic rubber produced from monomers obtained from the cracking and refining of petroleum.

5. A modified asphalt composition according to claim 4 wherein said monomers are selected from the group consisting of styrene, butadiene, carboxylated butadiene, isobutylene, isoprene, carboxylated isoprene, chloroprene, ethylene, propylene, acrylonitrile, and mixtures thereof.

6. A modified asphalt composition according to claim 1 wherein said elastomer is a block copolymer of at least one conjugated diene and at least one monoalkenyl aromatic hydrocarbon.

7. A modified asphalt composition according to claim 6 wherein said conjugated diene is at least one selected from the group consisting of butadiene, isoprene, chloroprene, carboxylated butadiene, and carboxylated isoprene.

8. A modified asphalt composition according to claim 7 wherein said conjugated diene is butadiene and isoprene.

9. A modified asphalt composition according to claim 6 wherein said monoalkyenyl aromatic hydrocarbon is styrene.

10. A modified asphalt composition according to claim 6 wherein said block copolymer has a general formula A-B-A or (A-B)_n X; wherein each A block is a monoalkyenyl aromatic hydrocarbon polymer block, each B block is a conjugated diolefin polymer block, X is a coupling agent and n is an integer from 2 to about 30.

11. A modified asphalt composition according to claim 6 wherein the configuration of said block copolymer is linear, radial, star, or tapered.

12. A modified asphalt composition according to claim 6 wherein said block copolymer has a number average molecular weight from about 30,000 to about 300,000.

13. A modified asphalt composition according to claim 10 wherein said conjugated diene is butadiene and said monoalkyenyl aromatic hydrocarbon is styrene and the amount of styrene repeating units in said block copolymer ranges from about 15% by weight to about 50% by weight based on the weight of said block copolymer with the remainder being repeating units derived from butadiene.

14. A modified asphalt composition according to claim 6 wherein said block copolymer is a styrene-butadiene block copolymer having a number average molecular weight ranging from about 50,000 to about 200,000.

15. A hot mix asphalt composition comprising said modified asphalt composition of claim 1 and aggregate.

16. A modified asphalt composition according to claim 1 wherein the amount of said elastomer and said plastomer is sufficient to increase the PG rating of the modified asphalt composition by +1 to +3 grades.

17. A modified asphalt composition according to claim 1 wherein said plastomer is present in said modified asphalt composition in an amount from about 0.1% by weight to about 10% by weight based on the weight of the modified asphalt composition.

18. A modified asphalt composition according to claim 1 wherein said elastomer is present in said modified asphalt composition in an amount from about 0.1% by weight to about 10% by weight based on the weight of the modified asphalt composition.

19. A modified asphalt composition according to claim 1 wherein said asphalt has a PEN value from about 40 to about 300 dmm.

20. A modified asphalt composition according to claim 1 wherein said asphalt has an AC value from about 2.5 to about 40 hundreds of poises.

21. A modified asphalt composition according to claim 1 wherein said asphalt has an AR value from about 1,000 to about 16,000 poises.

22. An article produced by the modified asphalt composition of claim 1.

23. An article produced by the hot mix asphalt composition of claim 15.

24. A modified asphalt composition comprising: at least one plastomer, at least one elastomer, and asphalt, wherein said plastomer is oxidized polyethylene and wherein said elastomer is a block copolymer of at least one conjugated diene and at least one monoalkenyl aromatic hydrocarbon.

25. A process for producing the modified asphalt composition of claim 24 comprising:

1) contacting at least one plastomer and at least one elastomer to produce a pellet; and

2) adding said pellet to asphalt in a mixing zone to produce said modified asphalt composition.

26. A modified asphalt composition according to claim 24 wherein said conjugated diene is at least one selected from the group consisting of butadiene, isoprene, chloroprene, carboxylated butadiene, and carboxylated isoprene.

27. A modified asphalt composition according to claim 26 wherein said conjugated diene is butadiene and isoprene.

28. A modified asphalt composition according to claim 24 wherein said monoalkyenyl aromatic hydrocarbon is styrene.

29. A modified asphalt composition according to claim 24 wherein said block copolymer has a general formula A-B-A or (A-B)_n X; wherein each A block is a monoalkyenyl aromatic hydrocarbon polymer block, each B block is a conjugated diolefin polymer block, X is a coupling agent and n is an integer from 2 to about 30.

30. A modified asphalt composition according to claim 24 wherein the configuration of said block copolymer is linear, radial, star, or tapered.

31. A modified asphalt composition according to claim 24 wherein said block copolymer has a number average molecular weight from about 30,000 to about 300,000.

32. A modified asphalt composition according to claim 29 wherein said conjugated diene is butadiene and said monoalkyenyl aromatic hydrocarbon is styrene and the amount of styrene repeating units in said block copolymer ranges from about 15% by weight to about 50% by weight based on the weight of said block copolymer with the remainder being repeating units derived from butadiene.

33. A modified asphalt composition according to claim 24 wherein said block copolymer is a styrene-butadiene block copolymer having a number average molecular weight ranging from about 50,000 to about 200,000.