KR101667430B1 - Composition for Warm-Mix Asphalt Pavements - Google Patents

Abstract

According to an embodiment of the present invention, a composition for middle-temperature asphalt pavement is provided which can simultaneously satisfy the plastic deformation resistance at a high temperature and the crack resistance at a low temperature.

Description

Composition for Warm-Mix Asphalt Pavements [0002]

The present invention relates to a composition for medium temperature asphalt pavement. More specifically, the present invention relates to a composition for medium temperature asphalt pavement, which simultaneously has improved plastic deformation resistance at high temperature and crack resistance at low temperature.

Due to rapid industrialization and economic development, rapid energy consumption has caused global warming and global weather changes, and oil spikes have had a significant impact on global economic activity. Thus, in recent years, fuel-consuming products have emerged as important issues not only from the environmental point of view but also from the economic point of view. In particular, the Kyoto Protocol adopted in 1997 introduced the emission trading system, the common implementation system and the clean development system to reduce carbon dioxide efficiently. Thus, efforts to develop low-carbon technologies to reduce energy consumption in each country are actively conducted have.

The above-mentioned demand for low-carbon technology is not an exception in the field of road pavement. When the low-carbon technology is applied to the asphalt road pavement which is widely applied worldwide, considering the scale of its application, .

Currently hot asphalt pavement, which is widely applied for road pavement, is manufactured by manufacturing a hot asphalt composition having a high temperature of about 160 to 170 캜. This method emits a large amount of carbon dioxide at the road pavement site, and thus the generation of greenhouse gas is a factor. That is, asphalt materials for road pavement are mixed and mixed at high temperature. In this process, nitrogen oxides and sulfur oxides, which are harmful gases, are generated together with carbon dioxide.

Asphalt pavement has been proposed as an alternative to the above-mentioned problems of the hot (high temperature) asphalt pavement method. Unlike high temperature asphalt construction, the medium temperature asphalt packaging method is a technique for manufacturing and packaging an asphalt composition at about 110 to 140 캜. At present, the mesophase asphalt pavement technology is in the early stage of development internationally, and related research is being carried out mainly in Europe, USA and Japan, and partly applied in the field. In particular, since 2008, standardization of related technologies has been attempted by the federal government in the United States.

In the case of the mid-temperature type asphalt composition, it is possible to add a modifier or binder which softens the asphalt easily at the middle temperature or foam the asphalt using a chemical modifier or moisture to easily mix with the aggregate even at the middle temperature.

This mesophase-applied asphalt composition has the advantages of reducing the energy required for heating the aggregate and the asphalt (for example, by about 25%) compared with the conventional high-temperature heating type, and decreasing the emission of harmful gas during production and application Respectively. It is known that when the actual installation temperature is lowered by 10 ° C, the amount of harmful gas emission is reduced by about half. In addition, the petroleum-based raw material is reduced by about 30% during the process of manufacturing the asphalt composition, the curing time can be reduced even after the construction, and the generation of noxious gas or dust can be suppressed to secure the safety of the worker at the construction site .

Currently, the following techniques are known for the production of mesophilic asphalt.

First, after the zeolite synthetic material is hydrated with water, as a powdered material, the foaming action is induced in the production of the asphalt composition, so that the viscosity of the asphalt is reduced and the workability required for production and construction at low temperature can be obtained.

Second, the soft binder is mixed with the aggregate and then coated with a hard binder. Through these processes, the asphalt viscosity can be reduced and the workability necessary for production and construction at a low temperature can be secured.

Third, paraffin wax having a low melting point is added and added to asphalt to lower the viscosity.

As described above, the principle of the atmospheric-type asphalt composition known in the art is to mix the aggregate with the aggregate even at a low temperature, thereby lowering the viscosity of the asphalt binder which can be applied in the field. In particular, a technique of lowering the asphalt viscosity by adding a wax having a melting point of about 70 to 120 DEG C to the asphalt is widely used.

In this connection, there is also known a technique of lowering viscosity by adding petroleum-based polyethylene (PE) -based wax and micro-wax to asphalt (U.S. Patent Application Publication No. 2010/0227954, etc.) A technique using a combination of viscosity softening components such as wax, micro wax, carnauba wax, polyethylene wax and EVA wax is also known (Korean Patent Laid-open No. 2009-129546, etc.).

However, the wax-based modified component used in the prior art is a crystalline solid at a temperature of 80 캜 or lower, and exhibits brittleness with almost shrinkage. Therefore, if the proper amount is not maintained, cracking can easily occur at low temperatures. That is, if the content of the modified component of the wax system is increased to lower the viscosity, crack resistance at low temperature is weakened and the low temperature common grade (for example, PG-22) of the modified asphalt is not satisfied. Further, although a technique of mixing powdered rubber vulcanizate (for example, U.S. Patent No. 5,959,007) is known, increasing the content of such a rubber or polymer component will lower the viscosity property of the wax-based modifying component There is a problem that it is difficult to implement.

As described above, since there are difficulties in simultaneously satisfying the plastic deformation resistance at a high temperature and the crack resistance at a low temperature in the production of a mid-temperature type asphalt composition, research and development thereof have been continuously carried out.

In the concrete example of the present invention, it is intended to provide a composition for middle-temperature asphalt paving which can simultaneously satisfy the plastic deformation resistance at a high temperature and the crack resistance at a low temperature.

According to embodiments of the present invention,

(i) 91 to 94 wt% of asphalt;

(ii) 3 to 5% by weight of a thermoplastic elastomer;

(iii) 2 to 4% by weight maleic anhydride grafted polyethylene (MA-g-PE) wax having a grafting rate of 4 to 10%; And

(iv) 0.1 to 1% by weight of process oil;

/ RTI >

There is provided a composition for medium temperature asphalt pavement exhibiting a viscosity of about 700 cP or less at 135 캜.

According to a preferred embodiment, the asphalt composition may meet the PG76-22 standard.

According to a preferred embodiment, the thermoplastic elastomer may be styrene-butadiene-styrene (SBS), styrene butadiene copolymer rubber (SBR), natural rubber latex or a combination thereof.

According to a preferred embodiment, the molecular weight (M _w ) of the maleic anhydride grafted polyethylene wax may range from about 3,000 to 5,000.

According to a preferred embodiment, the process oil may be an aromatic hydrocarbon, naphthenic hydrocarbon, paraffinic hydrocarbon or a combination thereof having a viscosity index in the range of 50 to 200.

According to another embodiment of the present invention,

a) heating 91 to 94% by weight of asphalt to 130 to 200 캜;

b) adding and mixing to the heated asphalt 2 to 4% by weight of grafted maleic anhydride grafted maleic anhydride having a grafting rate of 4 to 10% and 0.1 to 1% by weight of process oil; And

c) adding 3 to 5% by weight of a thermoplastic elastomer to the mixture of step b) and mixing at 150 to 200 캜;

/ RTI >

There is provided a method for producing a medium temperature asphalt paving composition exhibiting a viscosity of about 700 cP or less at 135 캜.

Since the composition for medium temperature asphalt pavement according to the embodiment of the present invention can simultaneously satisfy the resistance against plastic deformation at high temperature and the resistance against crack at low temperature, it is expected to be widely commercialized as an energy saving and low carbon technology in the future.

The embodiments provided in accordance with the present invention can be all achieved by the following description. It is to be understood that the following description is of a preferred embodiment of the present invention and that the present invention is not necessarily limited thereto.

According to an embodiment of the present invention, a wax component, that is, a maleic anhydride grafted polyethylene (MA-g-PE) in which a block copolymer is formed with maleic anhydride, is added so that the process oil stream and the thermoplastic elastomer are homogeneous among the asphalt (For example, 110 to 140 DEG C), and it is also possible to improve the properties at low temperature, for example, crack resistance and the like, so that it can be effectively used as a medium temperature asphalt pavement There is provided an asphalt composition capable of securing the specifications.

Particularly, the above-mentioned asphalt composition is effective for mid-temperature construction since it can meet the PG 76-22 standard.

The PG standard referred to in the present specification is a new standard presented in the SHRP (Strategic Highway Research Program, USA) project, which studies roads in general for the purpose of improving existing roads and improving the common use of roads. It corresponds to the asphalt standard. Unlike existing penetration and viscosity standards, the five basic performances of asphalt, namely aging, plastic deformation, fatigue cracking, resistance to low temperature cracking and ease of operation, are evaluated in a comprehensive and scientific way, And asphalt grade according to traffic conditions.

As an example, in the case of PG 76-22, the first numeral "76" indicates the grade at high temperature. The meaning of the figure is that it has the physical property to maintain durability and bearing capacity as asphalt up to at least 76 ° C it means. On the other hand, the second numeral "-22" indicates the grade at low temperature, and this figure also indicates that the resin has a low temperature resistance as a binder (binder) when packed up to -22 ° C.

For example, in the case of PG 76-22, the initial asphalt dynamic shear stress (G * / sin δ @ 76 ° C, kPa) is higher than 1 kPa, the shear stress after thin film heating (TFO or RTFOT) is higher than 2.2 kPa, Creep stiffness (CS (S) @ - 12 캜, MPa) of 300 MPa or less and a slope (m-value @ - 28 ° C, kPa) 12 ° C) of 0.3 or more.

The composition of the mesophase-type asphalt paving composition according to this specific example is as follows.

asphalt

In the embodiment of the present invention, asphalt is also referred to as asphalt concrete (or ascon) or bitumen, and widely exists as a solid or semi-solid at room temperature and gradually liquefies upon heating, It may be natural bitumen or a material obtained as a residue of a petroleum refining process and may in the narrow sense mean a high viscosity black liquid or semi-solid component present in crude oil or the like. Typically, it may include straight asphalt, semi-blown asphalt, natural asphalt, tar, pitch, or a combination thereof, which is, by way of example, not necessarily to the kind listed above.

For example, the asphalt may typically have an intrusion (25 ° C) as measured by ASTM D5 of typically about 5 to 400 dm (1/10 mm), specifically about 60 to 80 dm. In addition, a typical viscosity (60 DEG C) may range from about 1,000 to 10,000,000 cP, more specifically about 150,000 to 180,000 cP.

According to embodiments of the present invention, the asphalt component may be contained in the range of about 91 to 94 wt%, specifically about 92 to 93 wt%, based on the total asphalt composition.

Thermoplastic elastomer

In the embodiment of the present invention, the thermoplastic elastomer is a component which improves the viscosity property at high temperature while enhancing the elasticity at low temperature. Examples of the thermoplastic elastomer suitable for the embodiment of the present invention include styrene copolymers (more specifically, styrene-butadiene rubber (SBR), styrene-butadiene-styrene block copolymer styrene block copolymer (SBS), styrene-ethylene-butadiene-styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS), etc.); Olefin copolymers (more specifically, ethylene-vinyl acetate copolymers (EVA), ethylene methacylate copolymers (EMA), ethylene propylene diene polymers (EPDM), etc.); Other polymers (more specifically, nitrile-butadiene rubber (NBR), polyvinyl chloride (PVC), polyisobutene, and polybutadiene (PB)

Preferably the styrene polymer, for example, solid form: Specifically, the molecular weight (M _w) or more than about 100,000 bar to use the styrene-based polymer (particle size range from about 500 to 2,000㎛), (more specifically, about 150,000 to about 250,000), and a styrene content from about 20 to 50% by weight of a styrene-butadiene block copolymer (SBS), and the molecular weight (M _w) is more than 50,000 (more specifically, from about 60,000 to about 150,000), and Styrene butadiene copolymer (SBR) having a styrene content of about 5 to 20% by weight may be used, and these may be used singly or in combination.

According to an embodiment of the present invention, the thermoplastic elastomer may be contained in an amount of about 3 to 5% by weight, specifically about 3.5 to 4.5% by weight, more specifically about 4% by weight, based on the entire asphalt composition. When the thermoplastic elastomer is present in an amount of less than a certain amount, it may not satisfy the required property at high temperature, specifically, the PG 76 requirement, while if it is contained in an excessive amount, it may cause an inhibiting effect in lowering the viscosity of the whole composition. Therefore, it may be desirable to adjust to the above-mentioned range.

Maleic anhydride Grafted  Polyethylene ( MA -g- PE ) Wax

According to an embodiment of the present invention, a maleic anhydride grafted polyethylene wax component is used. The wax component serves to soften the asphalt when mixed with the asphalt to reduce the viscosity, and when the melting point is below the melting point, , Whereas it exists as a liquid phase having a low viscosity at a melting point or higher. The melting point of the maleic anhydride grafted polyethylene wax may be, for example, in the range of about 70 to 120 캜, specifically about 90 to 115 캜.

Particularly, since the maleic anhydride grafted polyethylene wax (MA-g-PE wax) forms a copolymer while grafting maleic anhydride onto the PE wax, when it is added to the asphalt, the polyethylene wax In combination with asphalt, process oil, and thermoplastic elastomer as compared with the case where the component is used, it is possible to provide a property resistant to brittle fracture even at a low temperature.

The polyethylene wax is typically a polymer having an intermediate molecular weight (M _w : about 1,000 to 6,000) of paraffin and polyethylene, and the grafting conditions with maleic anhydride include a type of initiator And a content of less than about 20% by weight, depending on the content, the reaction temperature, and the reaction time. When the reaction temperature is low (for example, 130 ° C), the grafting rate is relatively low, while at a high temperature (for example, 150 ° C or more), the grafting rate is increased in a short time. According to this embodiment, an exemplary maleic anhydride grafted polyethylene wax may have a molecular weight (M _w ) ranging from about 1,500 to 12,000, more specifically from about 2,000 to 9,000.

On the other hand, the grafting rate of the maleic anhydride grafted polyethylene wax may be in the range of, for example, about 4 to 10%, specifically about 6 to 9%. The above-mentioned grafting rate is a factor affecting the low-temperature characteristics, and when it is less than a certain level, the crack resistance at low temperature is low, whereas when the grafting rate is too high, the effect of lowering the viscosity at low temperature can be suppressed. Therefore, it may be desirable to adjust to the aforementioned range.

According to this embodiment, the maleic anhydride grafted polyethylene wax may be used in an amount of about 2 to 4% by weight, specifically about 2.5 to 3.5% by weight, based on the entire asphalt composition. When the content of the wax component is too low, it is difficult to lower the viscosity at low temperatures. On the other hand, when the content of the wax component is too high, it may not satisfy the high temperature standard, that is, the PG 76 standard.

Process oil

According to this specific example, not only does it serve to improve workability, but also process oil is used to suppress embrittlement at low temperature. Such process oil is a petroleum-based or vegetable hydrocarbon-based oil and can be roughly classified into paraffinic oil, naphthenic oil, aromatic oil, and the like depending on its chemical composition. It is preferable that the process oil does not evaporate in the middle temperature range as much as possible and does not ignite during the mixing process of asphalt. For example, the process oil has a flash point of about 200 to 350 DEG C as measured by AASHTO TP5, Lt; RTI ID = 0.0 > 220-260 C. < / RTI > In addition, the viscosity (kinematic viscosity) may be in the range of about 50 to 300 cSt, specifically about 150 to 200 cSt.

According to one embodiment, a paraffinic oil or a naphthenic oil may be used in combination with an aromatic oil having a viscosity index of about 50 to 200. At this time, it may be preferable to control the content of saturated hydrocarbons (saturates) to about 10% by weight or less in order to suppress embrittlement at low temperatures.

The properties and compositions of exemplary process oils are shown in Table 1 below.

importance Kinematic viscosity
60 C (cSt) flash point
(° C) Component (wt.%) Saturated hydrocarbons Aromatic Resin Aspalten 1.0051 174 250 6.8 90 3.2 0

According to this embodiment, the process oil may be present in the range of about 0.1 to 1% by weight, specifically about 0.3 to 0.7% by weight, based on the total asphalt composition. As described above, the process oil improves the low-temperature embrittlement property. When used below a certain level, the crack resistance at low temperature is reduced, but when it is used in an excessively large amount, it may be difficult to meet the specification at high temperature have. Therefore, it may be desirable to adjust appropriately to the above-mentioned range.

In addition to the above-mentioned components, as optional components, free sulfur, sulfur compounds, sulfur donors and the like may be further included singly or in combination. The sulfur component is added to prevent the phase-separation stability of the thermoplastic elastomer and the asphalt to prevent long-term storage stability, that is, it may contain up to about 0.05 to 2.5% by weight based on the thermoplastic elastomer.

According to another embodiment of the present invention, the above-mentioned components can be prepared in an asphalt composition by blending in an appropriate manner. For example, when the asphalt is first heated to a temperature of about 130 to 200 ° C, specifically about 150 to 170 ° C, and MA-g-PE wax and process oil are added to the heated asphalt and preferably exhibit a uniform phase . At this time, it is preferable to carry out the mixing process under stirring and preferably while maintaining the temperature of the heated asphalt. The thermoplastic elastomer is then added and mixed, for example, at about 150 to 200 占 폚, specifically about 160 to 180 占 폚, preferably until a homogeneous phase is exhibited. At this time, the mixing process is preferably carried out under stirring.

The composition for asphalt pavement according to the embodiment of the present invention preferably exhibits a viscosity of about 700 cP or less, more specifically about 450 to 650 cP at 135 ° C to ensure mid-temperature serviceability. Furthermore, it would be desirable to meet the PG 76-22 standard, as described above.

The present invention can be more clearly understood by the following examples, and the following examples are merely illustrative of the present invention and are not intended to limit the scope of the invention.

The components used in this example and the comparative example are as follows.

(1) Asphalt: obtained from SK Energy, penetration and viscosity were 72 and 186,000 cP, respectively.

(2) Thermoplastic elastomer

- SBS: KUMHO product names KTR101 (molecular weight (M _w): 209,200, styrene content: 30.5% by weight)

- SBR: KUMHO product names 1500S (molecular weight (M _w): 57,000, styrene content: 13.1% by weight)

(3) Maleic anhydride grafted polyethylene wax

- grafting rate 2% MA-g-PE wax

PE wax of 150g in a nitrogen atmosphere (molecular weight (M _w): 3,000) and a monomer of maleic anhydride (molecular weight: 98.06, specific gravity: 1.509, and the melting point: 53.0 ℃) as the initiator were mixed with the organic peroxide (product name Zhenzhou's Dicumylperoxide (0.6 g) was added and benzene was added thereto, and the grafting reaction was carried out at 150 ° C for 0.5 hour. As a result of analysis, the molecular weight was 3,300.

- grafting rate 3.5% MA-g-PE wax

The grafting reaction was carried out under the same conditions except that the monomer content was changed. As a result, the molecular weight was 3,500.

- Grafting rate 8% MA-g-PE wax

The grafting reaction was carried out under the same conditions except that the monomer content was changed. As a result, the molecular weight was 4,200.

- Grefting rate 10.5% MA-g-PE wax

The grafting reaction was carried out under the same conditions except that the monomer content was changed. As a result, the molecular weight was 4,500.

(4) General PE wax: Product name of Polyethylene-Wax (molecular weight: 3,000)

(5) process oil

SK Aromatic Materials (viscosity index: 100, saturated hydrocarbon content: 9.8%) was used.

Example 1

Asphalt compositions were prepared according to Table 2 below. 92.5 parts by weight of asphalt were heated to 163 DEG C, and 0.5 part by weight of process oil and 3 parts by weight of MA-g-PE wax (grafting ratio 8%) having a molecular weight of 4200 were added and stirred at 2,000 rpm for 0.2 hour while maintaining the temperature. Lt; / RTI > Subsequently, 4 parts by weight of a styrene-butadiene block copolymer (SBS) having a styrene content of 30.5% was added thereto, and the mixture was completely melted at 2,200 rpm for 2 hours while being heated at 175 DEG C, Respectively.

Example 2 and Comparative Examples 1 to 7

An asphalt composition was prepared in the same manner as in Example 1, except that the composition was changed as shown in Table 2 below.

Unit: parts by weight
asphalt Thermoplastic elastomer
MA-g-PE wax (graft ratio)
process
oil SBS SBR 2% 3.5% 8% 10.5% Example 1 92.5 4 3 0.5 Example 2 92.5 4 3 0.5 Comparative Example 1 93 4 3 - Comparative Example 2 91.8 4 3 1.2 Comparative Example 3 92.5 4 3 0.5 Comparative Example 4 92.5 4 3 0.5 Comparative Example 5 92.5 4 3 0.5 Comparative Example 6 93 4 1.5 0.5 Comparative Example 7 91 4 4.5 0.5

Comparative Example 8

An asphalt composition was prepared in the same manner as in Example 1, except that the usual PE wax was used instead of the MA-g-PE wax.

Specification Test

The PG76-22 standard tests for Examples 1 and 2 and Comparative Examples 1 to 8 were performed, and the results are shown in Table 3 below.

PG76-22
standard The viscosity is 135 DEG C, cP G * / sin?
@ 76 ° C, kPa TFO or RTFOT Residue (AASHTO T240) weight
Loss, % G * / sin?
@ 76 ° C, kPa Pressure Aging Vessel Residue G * x Sin?
@ 28 ° C, kPa CS (S)
@ -12 ° C, MPa m-value
@ -12 ° C <3,000 > 1.0 <0.8 > 2.2 <5000 <300 > 0.3 Example 1 675 1.41 0.1 2.26 1450 112 0.33 Example 2 690 1.42 0.1 2.28 1460 117 0.31 Comparative Example 1 800 1.51 0.1 2.35 1650 140 0.28 Comparative Example 2 640 1.17 0.2 2.13 1350 115 0.32 Comparative Example 3 585 1.44 0.1 2.32 1850 165 0.27 Comparative Example 4 620 1.42 0.1 2.28 1550 126 0.29 Comparative Example 5 1850 2.1 0.1 2.77 1850 110 0.33 Comparative Example 6 2150 2.7 0.2 3.14 1950 111 0.33 Comparative Example 7 420 1.2 0.1 2.16 1550 129 0.28 Comparative Example 8 560 1.44 0.1 2.33 1920 175 0.27

- In Examples 1 and 2, not only the viscosity can be lowered in the mid-temperature zone (135 ° C), but the m-value, which means crack resistance at low temperature, exceeds the required level. Respectively.

- In the case of not adding the process oil (Comparative Example 1), the crack resistance at low temperature did not meet the specification, and when the process oil was contained in a level exceeding a certain level (Comparative Example 2) Crack resistance is high and it satisfies PG-22 but it does not satisfy the high temperature standard.

When the grafting ratio of the MA-g-PE wax was adjusted to be less than a certain level (Comparative Examples 3 and 4), the crack resistance at low temperature was low and the specifications were not satisfied. On the other hand, when the grafting ratio exceeded the required level (Comparative Example 5), the high temperature and low temperature standards were satisfied, but the viscosity in the middle temperature range was markedly increased as compared with the examples, .

When the content of the MA-g-PE wax was too low (Comparative Example 6), the high temperature and low temperature standards were satisfied, but the viscosity in the middle temperature range was markedly increased as compared with the Examples, Example 7) shows not only low crack resistance at low temperatures, but also high temperature standards.

As described above, the specific example according to the present invention has properties suitable for the mid-temperature type asphalt pavement standard such as PG76-22 by specifying the contents and properties of constituents of the asphalt composition.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (11)

(i) 91 to 94 wt% of asphalt;
(ii) 3 to 5% by weight of a thermoplastic elastomer;
(iii) 2-4% by weight maleic anhydride grafted polyethylene (MA-g-PE) wax having a grafting rate of 6-9% by weight; And
(iv) 0.1 to 1% by weight of process oil;
/ RTI &gt;
Exhibits a viscosity of less than 700 cP at 135 DEG C,
Wherein the process oil comprises a paraffinic oil or a naphthenic oil in combination with an aromatic oil having a viscosity index of 50 to 200. The composition according to claim 1, wherein the composition is a PG76-22 standard. [3] The composition according to claim 1, wherein the thermoplastic elastomer is styrene-butadiene-styrene block copolymer (SBS), styrene butadiene rubber (SBR), natural rubber latex or a combination thereof. 4. The method of claim 3 wherein the thermoplastic elastomer has a molecular weight of more than 100,000 and a styrene content of 20 to 50% by weight of styrene-butadiene and copolymers (SBS) styrene blocks, the molecular weight (M _w) is more than 50,000 styrene content Styrene-butadiene rubber (SBR) of 5 to 20% by weight or a combination thereof. The composition according to claim 1, wherein the maleic anhydride grafted polyethylene wax has a melting point of 70 to 120 캜. The composition according to claim 1, wherein the maleic anhydride grafted polyethylene wax has a molecular weight (M _w ) of 2,000 to 9,000. delete delete 2. The composition according to claim 1, wherein the process oil has a saturated hydrocarbon content of 10 wt% or less. The composition according to claim 1, wherein the asphalt is straight asphalt, semi-blown asphalt, natural asphalt, tar, pitch or a combination thereof. a) heating 91 to 94% by weight of asphalt to 130 to 200 캜;
b) adding and mixing 2 to 4% by weight maleic anhydride grafted polyethylene wax having a grafting rate of 6 to 9% by weight to the heated asphalt and 0.1 to 1% by weight of a process oil; And
c) adding 3 to 5% by weight of a thermoplastic elastomer to the mixture of step b) and mixing at 150 to 200 캜;
/ RTI &gt;
Exhibits a viscosity of less than 700 cP at 135 DEG C,
Wherein the process oil comprises a paraffinic oil or a naphthenic oil in combination with an aromatic oil having a viscosity index of 50 to 200.