Manufacturing method of asphalt for road paving

Abstract

To provide a method for producing asphalt for road paving in which, by electron beam irradiation to an asphalt composition in an open atmosphere, an asphalt for road paving having improved pavement durability and resistance to deformation can be produced.SOLUTION: Provided is a method for producing asphalt for road paving, which is a method for producing asphalt for road paving that comprises a step (SA) of irradiating electron beam to an asphalt composition in an open atmosphere, and, in the step (SA), an asphalt composition (X) before being irradiated with electron beam is irradiated with the electron beam having an energy of 1 keV or more and 200 MeV or less and an irradiation dose of 100 kGy or more and 1 MGy or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a method for producing asphalt for road paving. [Background technology]

[0002] Roads on which vehicles travel are paved to enhance convenience and safety. In particular, asphalt mixtures used in asphalt paving are readily available nationwide, making construction easy. Furthermore, from the perspective of being recyclable, asphalt paving is widely used as a general type of pavement and has become an essential social infrastructure in modern society.

[0003] Asphalt pavements are constantly exposed to traffic loads and environmental stressors, and over time, they suffer damage such as rutting, cracking, and loss of flatness. Therefore, there is a need to improve the durability of asphalt pavements.

[0004] One known method for improving the durability of asphalt pavement from a chemical perspective is to improve the thermal properties of the asphalt composition by mixing in polymer materials, which are modifiers. Furthermore, as a method for modifying asphalt compositions based on their physical properties, research is underway to accelerate polymerization reactions in asphalt compositions using electron beam processing systems (EPS) (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] U.S. Patent No. 9,186,645 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In the technology described in Patent Document 1, in a closed system, the asphalt composition is modified by irradiating the asphalt composition with an electron beam. In the case of a closed system, since it is possible to block outside air, there is an advantage that the influence of oxygen can be eliminated. However, a closed system such as a vacuum has a problem that the heat generated during electron beam irradiation accumulates and the temperature easily rises. In addition, since a closed system requires a complicated structure such as a sealing structure, there is a problem that electron beam irradiation cannot be easily performed. Therefore, it is desired to establish an electron beam irradiation technique for an asphalt composition under an open atmosphere that is easy to avoid the problem of temperature rise and has high simplicity.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide a method for producing asphalt for road paving that can produce asphalt for road paving with improved durability and less deformation by irradiating an asphalt composition with an electron beam under an open atmosphere.

Means for Solving the Problems

[0008] As a result of intensive studies, the present inventors have found that the above problems can be solved by irradiating an asphalt composition with an electron beam under specific conditions in an open atmosphere in the manufacturing process of asphalt for road paving, and have completed the present invention.

[0009] That is, the present invention provides the following [1]. [1] A method for producing asphalt for road paving, comprising a step (S A ) of irradiating an asphalt composition with an electron beam under an open atmosphere, in the step (S A ), the asphalt composition (X) before being irradiated with the electron beam is irradiated with the electron beam having an energy of 1 keV or more and 200 MeV or less and an irradiation dose of 100 kGy or more and 1 MGy or less.

Effects of the Invention

[0010] According to the present invention, it is possible to provide a method for producing asphalt for road paving, which can improve the durability of paving and produce road paving asphalt that is difficult to deform by irradiating an asphalt composition with an electron beam under atmospheric release.

Brief Description of Drawings

[0011] [Figure 1] It is a schematic diagram showing a method of irradiating an electron beam to a solid asphalt composition (X). [Figure 2] It is an infrared absorption spectrum in the angular vibration region of alkane in the examples. [Figure 3] It is an infrared absorption spectrum in the stretching vibration region of carboxylic acid in the examples.

Mode for Carrying Out the Invention

[0012] In this specification, for preferred numerical ranges (for example, ranges such as content), the lower limit value and the upper limit value described step by step can be combined independently. For example, from the description of the lower limit value such as "preferably 10 or more, more preferably 30 or more, still more preferably 40 or more" and the description of the upper limit value such as "preferably 90 or less, more preferably 80 or less, still more preferably 70 or less", as a preferred range, for example, "10 or more and 70 or less", "30 or more and 70 or less", "40 or more and 80 or less", etc., ranges obtained by independently combining the selected lower limit value and the upper limit value can also be selected. Also, from the same description, for example, it is also possible to select a range defined by only one of the lower limit value or the upper limit value such as "40 or more" or "70 or less". In addition, in this specification, in the description of numerical ranges, for example, the description "10 to 90" is synonymous with "10 or more and 90 or less". In addition, the numerical values of "or more", "or less", "less than", and "more than" regarding the description of numerical ranges can also be arbitrarily combined.

[0013] [Method for Producing Asphalt for Road Paving] The method for manufacturing road paving asphalt according to this embodiment involves a step of irradiating the asphalt composition with an electron beam in an open atmosphere (S A A method for manufacturing asphalt for road paving, including the step (S A The method for producing asphalt for road paving involves irradiating an asphalt composition (X) before it is irradiated with an electron beam having an energy of 1 keV to 200 MeV and an irradiation dose of 100 kGy to 1 MGy.

[0014] The asphalt for road paving obtained by the manufacturing method of this embodiment may be referred to as "the asphalt for road paving of this embodiment."

[0015] In order to solve the above problems, the inventors conducted diligent research and found that, in the process of irradiating an asphalt composition with an electron beam under open atmospheric conditions, irradiating the asphalt composition (X) before irradiation with an electron beam having an energy of 1 keV to 200 MeV and an irradiation dose of 100 kGy to 1 MGy can improve the durability of road pavement asphalt by irradiating the asphalt composition with an electron beam under open atmospheric conditions.

[0016] Generally, when an electron beam with high energy is struck against a substance, the interaction between the electrons and the substance causes ionization and excited states, resulting in chemical reactions. This can lead to the generation of low-molecular-weight gases, cross-linking reactions, main chain severance, and double bond formation. These reactions depend on the electron beam irradiation conditions and the structure of the irradiated object. Asphalt, in particular, has a very complex molecular structure. The inventors of this invention surmise that the deformation-suppressing effect of road pavement asphalt and the effect of improving the durability of the pavement are due to crosslinking reactions and the formation of double bonds occurring in the asphalt composition.

[0017] Furthermore, electron beam irradiation in an open atmosphere generally raises concerns about the deterioration of the asphalt composition due to the presence of oxygen. However, as a result of diligent research by the inventors, it was found that, surprisingly, the asphalt composition is less affected by oxygen when electron beam irradiation is performed under the irradiation conditions of the present invention. In other words, it was found that the durability of the asphalt composition can be improved without deterioration after electron beam irradiation. Based on these findings, the inventors conducted further intensive studies and completed the present invention.

[0018] <Process(S A )> In the manufacturing method of this embodiment, step (S A This process involves irradiating asphalt with an electron beam while open to the atmosphere. In the method for manufacturing road pavement asphalt according to this embodiment, the asphalt composition (X) is irradiated with an electron beam in an open atmosphere, making it easier to avoid the problem of temperature rise due to heat generated during electron beam irradiation. Furthermore, the electron beam irradiation equipment can be made simpler than in a closed system.

[0019] Process (S A The method of irradiating asphalt with an electron beam is not particularly limited, and any known method can be used. For example, one method is to pave the road with an asphalt composition (X) before it is irradiated with an electron beam, and then irradiate the road with an electron beam to produce an asphalt composition (Y), or to irradiate the asphalt composition (X) with an electron beam inside a factory or the like to produce an asphalt composition (Y), and then pave the road with the asphalt composition (Y). Among these methods, the method of irradiating an asphalt composition (X) with an electron beam inside a factory or similar facility to produce an asphalt composition (Y), and then paving the road with the asphalt composition (Y), is preferred because it does not require road restrictions for electron beam irradiation after the pavement has been constructed.

[0020] Examples of the aforementioned electron beam include electron beams irradiated from an electron accelerator. In addition, as the electron accelerator, for example, a stationary electron accelerator or the like can be used. As a device capable of irradiating a large amount of samples under atmospheric open conditions, for example, a device named Electron Accelerator Loadtron TT200 (manufactured by IBA, Belgium) can be used.

[0021] In the step (S A ), the energy of the electron beam irradiated is 1 keV or more from the viewpoint of the physical modification effect of the asphalt composition (Y). Further, from the viewpoints that the electron beam can penetrate deeper into the asphalt composition (X) and physically modify the inside of the asphalt composition (X), and that the asphalt composition (X) can be uniformly modified, it is preferably 1 MeV or more, more preferably 10 MeV or more. In the step (S A ), the energy of the electron beam irradiated is 200 MeV or less from the viewpoint of the ease of irradiation of the equipment, preferably 100 MeV or less, more preferably 50 MeV or less. By irradiating the electron beam under the above irradiation conditions, the asphalt for road paving produced by electron beam irradiation has an increased complex shear modulus compared to the asphalt composition (X) before electron beam irradiation, so that the durability of the paving can be improved.

[0022] Regarding the energy and penetration power of the electron beam, when considering water as a reference, the maximum depth of the electron beam is said to be approximately expressed by the following formula (1). However, the maximum penetration depth is affected by the dose-depth energy distribution. Therefore, this distribution of energy impartation will correspond to the magnitude of chemical and physical actions. In the present invention, the electron beam energy is adjusted to be capable of uniformly irradiating in the depth direction of the irradiated object. Maximum penetration depth d = E / 2 ··· Formula (1) d: Maximum penetration depth (cm) E: Electron beam energy (MeV) As represented by the above formula (1), in the step (S AThe irradiation dose of the electron beam used in the irradiation can be adjusted by the electron beam energy, irradiation time, number of irradiations, etc., but from the viewpoint of the physical modification effect of the asphalt composition (Y) by promoting the chemical reaction and the practicality of electron beam irradiation under open atmospheric conditions, it is 100 kGy or more, preferably 200 kGy or more, and more preferably 300 kGy or more. Also, the above step (S A The irradiation dose of the electron beam used in the irradiation is 1 MGy or less, preferably 700 kGy or less, and more preferably 500 kGy or less, from the viewpoint of practicality of electron beam irradiation under open atmospheric conditions and improvement of irradiation efficiency (reduction of the number of irradiations). The electron beam irradiation dose can be confirmed, for example, using a device named CTA Dosimeter FTR-125 (manufactured by Fujifilm Corporation). By irradiating with an electron beam under the aforementioned irradiation conditions, the complex shear modulus of road pavement asphalt produced by electron beam irradiation increases compared to the asphalt composition (X) before electron beam irradiation, thereby improving the durability of the pavement.

[0023] The above step (S A In this case, it is preferable to irradiate the asphalt composition (X) with the electron beam such that the complex shear modulus of the asphalt composition (Y) after irradiation with the electron beam at 60°C, 1% strain, and a loading rate of 10 rad / s is 1.05 times or more than the complex shear modulus of the asphalt composition (X) before irradiation with the electron beam. The ratio of the complex shear modulus of the asphalt composition (Y) after electron beam irradiation to the complex shear modulus of the asphalt composition (X) before irradiation with the electron beam can be adjusted by the electron dose, but is preferably 1.05 times or more, more preferably 1.5 times or more, even more preferably 2.0 times or more, and even more preferably 5.0 times or more.

[0024] When irradiating an asphalt composition (X) with an electron beam, the electron beam irradiation can be performed independently of the state and temperature of the asphalt composition (X), the environment in which the asphalt composition (X) is placed, and other factors. Specifically, electron beam irradiation may be carried out at room temperature, or the asphalt composition (X) may be heated and in a fluid state. It may also be mixed with crushed stone or the like. Examples of conditions under which electron beam irradiation is performed on the asphalt composition (X) include before paving the asphalt pavement, simultaneously with paving the asphalt pavement, after paving the asphalt pavement, before manufacturing the asphalt composition, during manufacturing the asphalt composition, and after manufacturing the asphalt composition. As will be described later, in the manufacturing stage of the asphalt composition (Y), examples include before the step of mixing the modifier having a chemical modification effect, simultaneously with the step of mixing the modifier, and after the step of mixing the modifier. Examples of the form of the asphalt composition (X) to be irradiated with an electron beam include a solid state and a molten state.

[0025] If the asphalt composition (X) is in a solid state before electron beam irradiation, the above step (S A The energy of the electron beam irradiated in the ) is preferably 1 keV to 200 MeV, more preferably 1 keV to 100 MeV, and even more preferably 1 keV to 50 MeV, from the viewpoint of versatility. If the asphalt composition (X) is in a solid state before electron beam irradiation, the above step (S A The irradiation dose of the electron beam used in the irradiation facility is preferably 100 kGy or more and 1 MGy or less, more preferably 100 kGy or more and 500 kGy or less, and even more preferably 100 kGy or more and 200 kGy or less, from the viewpoint of the practicality of electron beam irradiation under open atmospheric conditions.

[0026] If the asphalt composition (X) is in a molten state before electron beam irradiation, the above step (S A The irradiation dose of the electron beam used in the irradiation device is preferably 100 kGy or more and 1 MGy or less, more preferably 100 kGy or more and 500 kGy or less, and even more preferably 100 kGy or more and 200 kGy or less, from the viewpoint of the practicality and versatility of electron beam irradiation under open atmospheric conditions.

[0027] This section describes a specific method for irradiating the asphalt composition (X) with an electron beam in the method for manufacturing asphalt for road paving according to this embodiment.

[0028] This section describes a method for irradiating an asphalt composition (X) with an electron beam when the asphalt composition (X) is in a solid state before electron beam irradiation. Figure 1 is a schematic diagram showing the method for irradiating a solid asphalt composition (X) with an electron beam. First, an asphalt composition (X) in a solid state at room temperature is prepared, and an asphalt composition (X) 1 is made with a uniform thickness to ensure uniform irradiation by electron beam. Next, the asphalt composition (X) 1 is placed on the surface of a support 2. Then, by irradiating the entire support 2 with an electron beam 3 from an electron beam irradiation device positioned above the support 2 under the irradiation conditions specified in this invention, the asphalt composition (X) 1 can be irradiated with electron beam. The support 2 may be movable. By placing a dosimeter 4 on the support 2 and checking the irradiation dose of the irradiated electron beam, it is possible to confirm whether the entire upper surface of the asphalt composition (X) 1 is irradiated with the electron beam.

[0029] When an asphalt composition (X) is irradiated with an electron beam of a specified dose, the temperature of the irradiated asphalt composition (Y) increases. Therefore, when an asphalt composition (X) in a solid state is irradiated with an electron beam of a specified dose, the asphalt composition (Y) may be cooled as necessary to maintain its solid state.

[0030] When the asphalt composition (X) is in a molten state before electron beam irradiation, one method of irradiating the asphalt composition (X) with an electron beam is, for example, to irradiate it with an electron beam inside a pipe used to transport the asphalt composition (X) or inside an asphalt mixture manufacturing mixer. When irradiating a molten asphalt composition (X) with an electron beam at a specified dose, the asphalt composition (Y) may be stirred as needed to promote the reaction. Because the molten asphalt composition (X) can be mixed with the electron-beam-irradiated asphalt composition (Y), the reaction of the asphalt by electron beam irradiation is more easily promoted than in the solid asphalt composition (X).

[0031] [Asphalt composition (X)] The asphalt composition (X) can be either unused straight asphalt that has not been used for road paving, or used deteriorated asphalt (recycled aggregate) that has been used for road paving. The asphalt composition (X) used in the method for producing asphalt for road paving according to this embodiment may or may not contain a modifier described later. The following describes embodiments of the asphalt composition (X) that include unused straight asphalt, used deteriorated asphalt, and a modifier.

[0032] -Unused straight asphalt- As the asphalt composition (X), unused straight asphalt that has not been used for road paving can be used. For example, product name: Straight Asphalt 60-80, manufactured by ENEOS Corporation.

[0033] Examples of the aforementioned straight asphalt include those conforming to the quality standards for petroleum asphalt for paving (JIS K2207-1996) as shown in Appendix 8.1.9 on page 222 of the Pavement Design and Construction Guidelines (2006 edition). Straight asphalt may be used alone or mixed with two or more other types.

[0034] If the asphalt composition (X) before electron beam irradiation is unused straight asphalt, then step (S A The energy of the electron beam irradiated in the facility is preferably 1 keV to 200 MeV, more preferably 1 keV to 100 MeV, and even more preferably 1 keV to 50 MeV, from the viewpoint of ease of irradiation of the equipment. If the asphalt composition (X) before electron beam irradiation is unused straight asphalt, then step (S A The irradiation dose of the electron beam used in the irradiation facility is preferably 100 kGy or more and 1 MGy or less, more preferably 100 kGy or more and 500 kGy or less, and even more preferably 100 kGy or more and 200 kGy or less, from the viewpoint of the practicality of electron beam irradiation under open atmospheric conditions.

[0035] ~Complex elastic modulus~ When the asphalt composition (X) before electron beam irradiation is unused straight asphalt, the ratio of the complex shear modulus of the straight asphalt after electron beam irradiation to the complex shear modulus of the straight asphalt before electron beam irradiation is preferably 1.05 times or more, more preferably 1.5 times or more, even more preferably 2.0 times or more, and even more preferably 5.0 times or more, from the viewpoint of improving the durability of the pavement. Furthermore, the ratio of the complex shear modulus of the unused straight asphalt (Y) after electron beam irradiation to the complex shear modulus of the unused straight asphalt (X) before electron beam irradiation is preferably as high as possible, and more preferably in a range where the elongation does not decrease. The complex modulus of elasticity at 60°C of the road paving asphalt (asphalt composition (X)) obtained by the manufacturing method of this embodiment can be measured by the method described in the example.

[0036] ~Softening point~ When the asphalt composition (X) before electron beam irradiation is unused straight asphalt, the softening point of the road pavement asphalt (asphalt composition (Y)) obtained by the manufacturing method of this embodiment is preferably 40°C or higher, more preferably 43°C or higher, and even more preferably 45°C or higher, from the viewpoint of improving the durability of the pavement. Furthermore, the softening point of the asphalt composition (Y) obtained by electron beam irradiation of the asphalt composition (X) is preferably as high as possible, and more preferably within a range where the elongation of the asphalt composition (Y) does not decrease. The softening point of the aforementioned road paving asphalt (asphalt composition (Y)) can be measured by the method described in the examples.

[0037] ~Elongation~ When the asphalt composition (X) before electron beam irradiation is unused straight asphalt, the elongation at 15°C of the road pavement asphalt (asphalt composition (Y)) obtained by the manufacturing method of this embodiment is preferably 30 or more, more preferably 50 or more, and even more preferably 100 or more, from the viewpoint of improving the durability of the pavement. Furthermore, from the viewpoint of physical modification effect, a higher elongation of the asphalt composition (Y) obtained by electron beam irradiation of the asphalt composition (X) is preferable, and a range that allows the complex modulus of elasticity of the asphalt composition (Y) to be as high as possible is even more preferable. The elongation of the aforementioned road paving asphalt (asphalt composition (Y)) at 15°C can be measured by the method described in the examples.

[0038] -Used, deteriorated asphalt- As the asphalt composition (X), used deteriorated straight asphalt (recycled aggregate) that has been used for road paving can be used. Examples include asphalt adhering to crushed stone already used in road paving. Furthermore, used, deteriorated asphalt may contain modifiers.

[0039] As a result of diligent research by the inventors, it has been discovered that even when used asphalt compositions used in road paving are irradiated with electron beams, the durability of pavements using used asphalt compositions can be improved. Generally, the molecular weight of straight asphalt tends to increase with age-related deterioration, but the inventors have found that when accelerated deterioration of asphalt is irradiated with an electron beam, the molecular weight of the deteriorated asphalt decreases. The inventors speculate that, in response to this, the aged asphalt undergoes a breakdown reaction through main chain severance upon electron beam irradiation, resulting in improved physical performance and regeneration.

[0040] If the asphalt composition (X) before electron beam irradiation is used deteriorated asphalt, then step (S) A The energy of the electron beam irradiated in the facility is preferably 1 keV to 200 MeV, more preferably 1 keV to 100 MeV, and even more preferably 1 keV to 50 MeV, from the viewpoint of ease of irradiation of the equipment. If the asphalt composition (X) before electron beam irradiation is used deteriorated asphalt, then step (S) A The irradiation dose of the electron beam used in the irradiation facility is preferably 100 kGy or more and 1 MGy or less, more preferably 100 kGy or more and 500 kGy or less, and even more preferably 100 kGy or more and 200 kGy or less, from the viewpoint of the practicality of electron beam irradiation under open atmospheric conditions.

[0041] ~Complex elastic modulus~ When the asphalt composition (X) before electron beam irradiation is used deteriorated asphalt, the ratio of the complex shear modulus of the asphalt composition (Y) after electron beam irradiation to the complex shear modulus of the asphalt composition (X) before electron beam irradiation is preferably 1.04 times or more, more preferably 1.05 times or more, and even more preferably 1.06 times or more, from the viewpoint of improving the durability of the pavement. Furthermore, the ratio of the complex shear modulus of the used deteriorated straight asphalt (Y) after electron beam irradiation to the complex shear modulus of the used deteriorated straight asphalt (X) before electron beam irradiation is preferably higher, and more preferably within a range where the elongation does not decrease. The complex modulus of elasticity at 60°C of the road paving asphalt (asphalt composition (X)) obtained by the manufacturing method of this embodiment can be measured by the method described in the example.

[0042] ~Softening point~ If the asphalt composition (X) before electron beam irradiation is used, deteriorated asphalt, the softening point of the road pavement asphalt (asphalt composition (Y)) obtained by the manufacturing method of this embodiment is preferably 48°C or higher, more preferably 50°C or higher, and even more preferably 53°C or higher, from the viewpoint of improving the durability of the pavement. Furthermore, the softening point of the asphalt composition (Y) obtained by electron beam irradiation of the asphalt composition (X) is preferably as high as possible, and more preferably in a range where the elongation of the asphalt composition (Y) does not decrease. The softening point of the aforementioned road paving asphalt (asphalt composition (Y)) can be measured by the method described in the examples.

[0043] ~Elongation~ If the asphalt composition (X) before electron beam irradiation is used, deteriorated asphalt, the elongation at 15°C of the road pavement asphalt (asphalt composition (Y)) obtained by the manufacturing method of this embodiment is preferably 3 or higher, more preferably 5 or higher, and even more preferably 7 or higher, from the viewpoint of improving the durability of the pavement. Furthermore, from the viewpoint of physical modification effect, a higher elongation of the asphalt composition (Y) obtained by electron beam irradiation of the asphalt composition (X) is preferable, and a range that allows the complex modulus of elasticity of the asphalt composition (Y) to be as high as possible is even more preferable. The elongation of the aforementioned road paving asphalt (asphalt composition (Y)) at 15°C can be measured by the method described in the examples.

[0044] <Process(S B )> The asphalt composition (X) may include straight asphalt and a modifier. In the manufacturing method of this embodiment, the step of mixing straight asphalt and a modifier (S B ) can include The above step (S B ) is the aforementioned step (S A ) may be carried out before the aforementioned step (S A ) may be carried out simultaneously with the above step (S A) may be carried out after this. Among these, modifiers are also used from the viewpoint of enhancing the modifying effect through crosslinking reactions, as described above (S B ) is the aforementioned step (S A It is preferable that this be carried out before ).

[0045] From the viewpoint of improving durability, the softening point of the asphalt after irradiation with the electron beam is preferably 1.05 times or more than the softening point of the asphalt before irradiation with the electron beam.

[0046] -Modifier- The asphalt composition (X) may contain, in addition to straight asphalt, a polymer polymer as a modifier having a chemical modification effect. It may also be blown asphalt that has been oxidatively modified by blowing at a high temperature of 200°C or higher. As the modifier, for example, polymer materials such as styrene-butadiene block copolymer (SBS), styrene-isoprene block copolymer (SIS), ethylene-vinyl acetate copolymer (EVA), polyethylene, polyester, polyamide resin, urethane resin, and epoxy resin can be used. Furthermore, the modifier may be recycled asphalt obtained by recycling paving binders and aggregates contained in existing asphalt pavements. The polymer-modified asphalt containing the aforementioned modifier conforms to the standard properties of polymer-modified asphalt as shown in Appendix 8.1.11 on page 223 of the Pavement Design and Construction Guidelines (2006 edition), but modified asphalt that does not conform to the standard properties can also be used. The modifier may be used alone or in combination of two or more types.

[0047] If the asphalt composition (X) before electron beam irradiation contains a modifier, the above step (S A The energy of the electron beam irradiated in the facility is preferably 1 keV to 200 MeV, more preferably 1 keV to 100 MeV, and even more preferably 1 keV to 50 MeV, from the viewpoint of ease of irradiation of the equipment. If the asphalt composition (X) before electron beam irradiation contains a modifier, the above step (S A The irradiation dose of the electron beam used in the irradiation facility is preferably 100 kGy or more and 1 MGy or less, more preferably 100 kGy or more and 500 kGy or less, and even more preferably 100 kGy or more and 200 kGy or less, from the viewpoint of the practicality of electron beam irradiation under open atmospheric conditions.

[0048] ~Complex elastic modulus~ From the viewpoint of improving the durability of the pavement, the ratio of the complex shear modulus of the asphalt composition (Y) after electron beam irradiation to the complex shear modulus of the asphalt composition (X) before electron beam irradiation is preferably 1.05 times or more, more preferably 1.1 times or more, and even more preferably 1.3 times or more. The complex modulus of elasticity at 60°C of the road paving asphalt (asphalt composition (X)) obtained by the manufacturing method of this embodiment can be measured by the method described in the example.

[0049] ~Softening point~ The softening point of the road pavement asphalt (asphalt composition (Y)) obtained by the manufacturing method of this embodiment is preferably 55°C or higher, more preferably 60°C or higher, and even more preferably 70°C or higher, from the viewpoint of improving the durability of the pavement. Furthermore, the softening point of the asphalt composition (Y) obtained by irradiating the asphalt composition (X) with an electron beam is preferably as high as possible, and more preferably in a range where the elongation of the asphalt composition (Y) does not decrease. The softening point of the aforementioned road paving asphalt (asphalt composition (Y)) can be measured by the method described in the examples.

[0050] ~Elongation~ The elongation of the road pavement asphalt (asphalt composition (Y)) obtained by the manufacturing method of this embodiment at 15°C is preferably 30 or more, more preferably 50 or more, from the viewpoint of improving the durability of the pavement. Furthermore, the elongation of the asphalt composition (Y) obtained by electron beam irradiation of the asphalt composition (X) is preferably as high as possible from the viewpoint of physical modification effect, and is more preferably in a range that allows the complex modulus of elasticity of the asphalt composition (Y) to be as high as possible. The elongation of the aforementioned road paving asphalt (asphalt composition (Y)) at 15°C can be measured by the method described in the examples.

[0051] -Other ingredients- The manufacturing method of this embodiment may further include a step of adding other components. The asphalt composition may, if necessary, contain other components besides those mentioned above, as long as they do not impair the effects of the present invention. Other components include, for example, lubricants such as surfactants to prevent peeling or water to improve workability. These may be used individually or in combination of two or more types.

[0052] [Durability of the pavement] The road paving asphalt (asphalt composition (Y)) obtained by the manufacturing method of this embodiment can be evaluated for its pavement durability by its rutting resistance, as described in the examples below.

[0053] According to one aspect of the present invention, the following [1] to [9] are provided. [1] A step of irradiating an asphalt composition with an electron beam in an open atmosphere (S A A method for manufacturing asphalt for road paving, including ) The above step (S A A method for producing asphalt for road paving, comprising irradiating an asphalt composition (X) before irradiation with an electron beam with an electron beam having an energy of 1 keV or more and 200 MeV or less, and an irradiation dose of 100 kGy or more and 1 MGy or less. [2] The above step (S A A method for producing asphalt for road paving according to [1], wherein the asphalt composition (Y) after irradiation with the electron beam is irradiated with the electron beam such that the complex shear modulus of the asphalt composition (Y) at 60°C, a strain of 1%, and a loading rate of 10 rad / s is 1.05 times or more than the complex shear modulus of the asphalt composition (X) before irradiation with the electron beam. [3] The method for producing road paving asphalt according to [1] or [2], wherein the asphalt composition (X) is an unused product that has not been used for road paving. [4] The method for producing asphalt for road paving according to [1] or [2], wherein the asphalt composition (X) is a used product that has been used for road paving. [5] A method for producing road pavement asphalt according to any one of [1] to [4], wherein the asphalt composition (X) includes straight asphalt and does not contain a modifier. [6] The asphalt composition (X) comprises straight asphalt and a modifier, The process of mixing the straight asphalt and the modifier (S B A method for producing asphalt for road paving according to any one of the above [1] to [4], including ) [7] The above step (S B ) is the aforementioned step (S A A method for manufacturing road paving asphalt as described in [6] above, which is carried out before ) [8] A method for producing asphalt for road paving according to any one of [1] to [7], wherein the electron beam is an electron beam irradiated from an electron accelerator. [9] The method for manufacturing road pavement asphalt according to [8], wherein the electron accelerator is a stationary electron accelerator. [Examples]

[0054] The present invention will be specifically described by the following examples, but the present invention is not limited to the following examples.

[0055] The physical properties of each type of asphalt for road paving (asphalt composition after electron beam irradiation), as described below, were measured by the following method.

[0056] [Complex modulus of elasticity] The complex modulus was measured using a Dynamic Shear Rheometer (DSR) test under the following conditions. The ratio of the complex modulus after electron beam irradiation (Example) to the complex modulus before electron beam irradiation (Comparative Example) was also calculated. Examples 1-3 are ratios relative to Comparative Example 1. Example 4 is a ratio relative to Comparative Example 2. Example 5 is a ratio relative to Comparative Example 3. • Device name: MCR 102 (manufactured by Anton-Paar) ·Loading speed: 10rad / s • Strain: 1% • Test temperature: 60℃ • Test fixture: Inner diameter 8mm Thickness: 1mm

[0057] [Softening point] The softening point was measured in accordance with the softening point test method (ring-ball method) described in A042 of the Pavement Survey and Testing Methods Handbook (2019 edition, published by the Japan Road Association).

[0058] [Elongation] The elongation at 15°C was measured in accordance with the A043 elongation test method in the Pavement Survey and Testing Methods Handbook (2019 edition, published by the Japan Road Association).

[0059] [Asphalt composition] The asphalt composition used in the manufacture of road paving asphalt is as follows:

[0060] • Unused straight asphalt (X1) (Product name: Straight Asphalt 60-80, manufactured by ENEOS Corporation, sample shape: solid, size: 300mm x 300mm x 10mm)

[0061] • Used, deteriorated straight asphalt (X2) (Sample shape: solid, size: 300mm x 300mm x 10mm) Used, deteriorated straight asphalt (X2) was subjected to a rotary thin film heating test (RTFOT) followed by an accelerated pressure degradation test (PAV) for 20 hours, compared to unused straight asphalt (X1), to accelerate its degradation.

[0062] • Modifier-containing asphalt composition: Polymer-modified asphalt (polymer: styrene-butadiene block copolymer, polymer content relative to the total amount of asphalt composition: 5.0% by mass, size: 300mm x 300mm x 10mm) The modifier-containing asphalt composition is manufactured by mixing unused straight asphalt (X1) with a polymer.

[0063] [Manufacturing of asphalt for road paving] Next, using the compositions described above, road paving asphalts for Examples 1-5 and Comparative Examples 1-3 were manufactured. The details of the components and electron beam irradiation conditions used in Examples 1-5 and Comparative Examples 1-3 are described below.

[0064] <Example 1> As shown in Figure 1, in order to suppress changes in properties due to heat treatment during physical property evaluation, a test specimen was prepared by molding unused solid straight asphalt (X1) 1 inside a test mold (size: 300 mm × 300 mm × 10 mm). Next, the test specimen was placed on a support 2. Then, under open air at room temperature (17.0°C to 22.8°C), the entire upper surface of the test specimen was directly irradiated from above with an electron beam 3 having an energy of 10 MeV and an electron dose of 20 kGy per irradiation, for 10 irradiations to achieve an irradiation dose of 200 kGy, using a device name: electron accelerator Rhodetron TT200 (manufactured by IBA, Belgium), to produce the road paving asphalt of Example 1. Furthermore, the irradiation dose of the irradiated electron beam was confirmed using a dosimeter 4 (device name: CTA Dosimeter FTR-125, manufactured by Fujifilm Corporation) placed on the support 2, and it was confirmed that the electron beam irradiated the entire upper surface of the test specimen.

[0065] <Example 2> The road paving asphalt of Example 2 was manufactured in the same manner as in Example 1, except that the electron beam irradiation dose was changed to 700 kGy (number of irradiations: 35 times) compared to the road paving asphalt of Example 1.

[0066] <Example 3> The road paving asphalt of Example 3 was manufactured in the same manner as in Example 1, except that the electron beam irradiation dose was changed to 1,000 kGy (number of irradiations: 50 times) compared to the road paving asphalt of Example 1.

[0067] <Example 4> Asphalt for road paving of Example 4 was produced in the same manner as in Example 1, except that the modifier-containing asphalt composition was exposed to air at room temperature (17.0°C to 22.8°C) with an electron beam intensity of 10 MeV and an irradiation dose of 500 kGy (number of irradiations: 25 times).

[0068] <Example 5> Asphalt for road paving, as described in Example 5, was manufactured in the same manner as in Example 1, except that used deteriorated straight asphalt (X2) was exposed to the atmosphere at room temperature (17.0℃~22.8℃), the electron beam intensity was set to 10 MeV, and the irradiation dose was 500 kGy (number of irradiations: 25 times).

[0069] <Comparative Example 1> Unused straight asphalt (X1) itself was used as the road paving asphalt in Comparative Example 1. That is, the road paving asphalt in Example 1 was not irradiated with an electron beam.

[0070] <Comparative Example 2> The modifier-containing asphalt composition itself was used as the road paving asphalt of Comparative Example 2. That is, the road paving asphalt of Example 4 was not irradiated with an electron beam.

[0071] <Comparative Example 3> Used, deteriorated straight asphalt (X2) itself was used as the road paving asphalt in Comparative Example 3. In other words, the road paving asphalt in Example 5 was not irradiated with an electron beam.

[0072] The following evaluations were performed on each of the obtained road paving asphalt samples. The results are shown in Table 1.

[0073] [Evaluation of pavement durability] For each of the road pavement asphalt samples in Examples 1-5 and Comparative Examples 1-3, rutting resistance was evaluated as an assessment of pavement durability. Specifically, the dynamic stability at 60°C and the final deformation at 60°C were measured in accordance with the "B003 Wheel Tracking Test Method" of the Pavement Survey and Testing Methods Handbook. Dynamic stability is an evaluation of the number of tire passes required for road pavement asphalt to deform by 1 mm. A higher dynamic stability value indicates that the road pavement asphalt is less prone to deformation. The ratio of the dynamic stability after electron beam irradiation (Example) to the dynamic stability before electron beam irradiation (Comparative Example) was also calculated. Examples 1-3 are ratios to Comparative Example 1. Example 4 is a ratio to Comparative Example 2. Example 5 is a ratio to Comparative Example 3. The smaller the final deformation value, the less the road paving asphalt deforms.

[0074] [Table 1]

[0075] As can be seen from Table 1, compared to the road pavement asphalt of Comparative Examples 1-3, which were not irradiated with electron beams, the road pavement asphalt of Examples 1-5 showed higher dynamic stability values ​​and lower final deformation values. In other words, its resistance to rutting improved. This confirmed that asphalt for road paving treated with electron beams is less prone to deformation, resulting in improved pavement durability.

[0076] [Infrared spectroscopy] Next, infrared spectroscopy was performed to analyze the changes in the characteristic groups, substructures, and compounds of the asphalt composition. An infrared spectrophotometer (model name: FT-IR8400S, manufactured by Shimadzu Corporation) was used for the analysis. The results are shown in Figure 2.

[0077] Infrared spectroscopy analysis of electron beam-irradiated asphalt composition (Y) revealed no significant changes in the functional group region in any of the samples. In the fingerprint region of undegraded straight asphalt and modifier-containing asphalt shown in Figure 2, the angular vibration of alkanes (1,380 cm) is observed. -1 ~1,365cm -1 1,470cm -1 ~1,430cm -1 A slight change was observed in ). No changes in the characteristic groups, substructures, or compounds of asphalt were observed by infrared spectroscopy. While there were concerns that electron beam irradiation in an open-air environment would accelerate the oxidative degradation of the asphalt composition, as shown in Figure 3, with the energy and irradiation dose used in this study, the stretching vibration of the carboxylic acid associated with oxidative degradation (1,700 cm) was not accelerated. -1 ~1,725cm -1 No changes were observed, and no acceleration of oxidation by radicals presumed to be generated by electron beam irradiation was observed.

Claims

1. A step of irradiating an asphalt composition with an electron beam inside a factory while open to the atmosphere (S Ａ A method for manufacturing asphalt for road paving, including ) The step (S Ａ A method for producing asphalt for road paving, comprising irradiating an asphalt composition (X) before irradiation with an electron beam with an electron beam having an energy of 1 keV or more and 200 MeV or less, and an irradiation dose of 100 kGy or more and 1 MGy or less.

2. The step (S Ａ A method for producing asphalt for road paving according to claim 1, wherein the asphalt composition (Y) is irradiated with the electron beam such that the complex shear modulus of the asphalt composition (Y) after irradiation with the electron beam at 60°C, a strain of 1%, and a loading speed of 10 rad / s is 1.05 times or more than the complex shear modulus of the asphalt composition (X) before irradiation with the electron beam.

3. The method for producing asphalt for road paving according to claim 1 or 2, wherein the asphalt composition (X) is an unused product that has not been used for road paving.

4. The method for producing asphalt for road paving according to claim 1 or 2, wherein the asphalt composition (X) is a used product that has been used for road paving.

5. A method for producing asphalt for road paving according to any one of claims 1 to 4, wherein the asphalt composition (X) includes straight asphalt and does not contain a modifier.

6. The aforementioned asphalt composition (X) comprises straight asphalt and a modifier, A step of mixing the straight asphalt and the modifier (S Ｂ A method for producing asphalt for road paving according to any one of claims 1 to 4, including )

7. The step (S Ｂ ) is the aforementioned step (S Ａ A method for manufacturing asphalt for road paving according to claim 6, which is carried out before )

8. The method for manufacturing asphalt for road pavement according to any one of claims 1 to 7, wherein the electron beam is an electron beam irradiated from an electron accelerator.

9. The method for manufacturing asphalt for road paving according to claim 8, wherein the electron accelerator is a stationary electron accelerator.

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