Asphalt modifier

Abstract

To provide an asphalt modifier for obtaining an asphalt mixture capable of producing an asphalt pavement excellent in durability, and maintaining workability even when producing an asphalt mixture at a low temperature, and an asphalt mixture and a production method of the same.SOLUTION: An asphalt modifier includes a polyester, where the polyester is a polycondensation product of polyethylene terephthalate, an alcohol constituent, and a carboxylic acid constituent, and satisfies at least one of the following condition (i), and condition (ii), and a content of a constitutional unit derived from the univalent carboxylic acid in the polyester and / or a constitutional unit derived from the univalent alcohol to 100 mol% of a total content of a constitutional unit derived from the alcohol constituent, and a constitutional unit derived from the ethylene glycol derived from the polyethylene terephthalate is 5 mol% or more and 20 mol% or less. (i) The carboxylic acid constituent includes a univalent carboxylic acid. (ii) The alcohol constituent includes a univalent alcohol.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an asphalt modifier, an asphalt mixture, and a method for producing the same.

Background Art

[0002] For paving roads such as motorways, parking lots, freight yards, and sidewalks, asphalt paving using an asphalt mixture is carried out because it is relatively easy to lay and the time from the start of paving work to the start of traffic can be shortened. In this asphalt paving, since the road surface is formed by an asphalt mixture in which aggregates are bonded with asphalt, the paved road has good hardness and durability.

[0003] Patent Document 1 discloses an asphalt modifier capable of achieving both a deep texture on the surface of the constructed paving body and high density inside the paving body, which contains a structural unit derived from an alcohol component and a structural unit derived from a carboxylic acid component, the alcohol component contains an alcohol having a bisphenol structure, and the carboxylic acid component contains a polyester containing a monovalent carboxylic acid. Patent Document 2 discloses an asphalt modifier for obtaining an asphalt mixture capable of achieving both the filling efficiency of an asphalt binder and the strength of asphalt paving, which contains a structural unit derived from a monovalent aliphatic carboxylic acid and / or a structural unit derived from a monovalent aliphatic alcohol crystalline polyester (A). Patent Document 3 discloses an asphalt modifier for obtaining an asphalt composition excellent in storage stability in which polyester is uniformly dispersed in asphalt even after being stored at a high temperature for a long time, which is composed of a polyester containing a structural unit derived from an alcohol component containing a predetermined amount of an aliphatic diol having a predetermined number of carbon atoms and an alkylene oxide adduct of bisphenol A, respectively, and a structural unit derived from a carboxylic acid component.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] From the viewpoints of recent environmental load reduction and soaring crude oil prices, efforts have been made to reduce fuel during the production of heated asphalt mixtures and to carry out medium-temperature mixing at a lower temperature compared to the conventional method. On the other hand, in the production of asphalt added with polymers such as thermoplastic resins and elastomers, thickening or elasticization of these polymers may induce construction defects and insufficient strength. According to the technique described in Patent Document 1, an asphalt pavement with excellent durability can be obtained. However, when the heated asphalt mixture is produced at a low temperature, the modification effect may decrease, and sufficient durability of the asphalt pavement may not be obtained.

[0006] The present invention relates to an asphalt modifier for obtaining an asphalt mixture capable of producing an asphalt pavement with excellent durability while maintaining workability even when the asphalt mixture is produced at a low temperature, and an asphalt mixture and a method for producing the same.

Means for Solving the Problems

[0007] The present invention relates to the following [1] to [3]. [1] An asphalt modifier containing polyester, The polyester is a polycondensate of polyethylene terephthalate, an alcohol component, and a carboxylic acid component, and satisfies at least one of the following conditions (i) and (ii). (i) The carboxylic acid component contains a monovalent carboxylic acid. (ii) The alcohol component contains a monohydric alcohol The content of the structural unit derived from the monobasic carboxylic acid and / or the structural unit derived from the monohydric alcohol in the polyester is 5 mol% or more and 20 mol% or less with respect to the total content of 100 mol% of the structural unit derived from the alcohol component and the structural unit derived from ethylene glycol of polyethylene terephthalate, an asphalt modifier. 〔2〕 An asphalt mixture containing the asphalt modifier according to 〔1〕, asphalt, and aggregate. 〔3〕 A method for producing an asphalt mixture, comprising a step of mixing the asphalt modifier according to 〔1〕, asphalt, and aggregate at 160°C or lower.

Advantages of the Invention

[0008] According to the present invention, an asphalt modifier for obtaining an asphalt mixture capable of producing an asphalt pavement excellent in durability while maintaining workability even when an asphalt mixture is produced at a low temperature, and an asphalt mixture and a method for producing the same can be provided.

Embodiments for Carrying Out the Invention

[0009] [Asphalt Modifier] The asphalt modifier of the present invention is an asphalt modifier containing polyester, The polyester is a polycondensate of polyethylene terephthalate, an alcohol component, and a carboxylic acid component, and satisfies at least one of the following conditions (i) and (ii), (i) The carboxylic acid component contains a monobasic carboxylic acid (ii) The alcohol component contains a monohydric alcohol The content of the structural unit derived from the monobasic carboxylic acid and / or the structural unit derived from the monohydric alcohol in the polyester is 5 mol% or more and 20 mol% or less with respect to the total content of 100 mol% of the structural unit derived from the alcohol component and the structural unit derived from ethylene glycol of polyethylene terephthalate.

[0010] The inventors have found that an asphalt mixture capable of producing an asphalt pavement excellent in durability while maintaining workability even when an asphalt mixture is produced at a low temperature can be obtained if an asphalt modifier containing a specific polyester is used. An asphalt pavement excellent in durability has, for example, a small rut depth measured by a wheel tracking test. An asphalt mixture excellent in workability has a small air void ratio of the resulting asphalt pavement.

[0011] Although the detailed mechanism by which the effects of the present invention are obtained is unclear, it is partly considered as follows. The effect of modifying asphalt with polyester is considered to be exerted in cooperation with the interaction between asphalt and polyester and the interaction between aggregate and polyester. When an asphalt mixture is produced at a low temperature, it is considered that the hydrogen bond, which is the interaction between aggregate and polyester, becomes stronger, and the interaction between asphalt and polyester becomes relatively weaker. As a result, it is presumed that the balance of the interaction between polyester and each component is lost, and a sufficient asphalt modification effect cannot be exhibited. The asphalt modifier of the present invention is considered to allow the interaction between asphalt and polyester to proceed sufficiently even at a low temperature by using a polyester having a specific structure. As a result, the interaction between polyester and each component is controlled, and it is considered that an excellent asphalt modification effect by polyester is exhibited.

[0012] <Polyester> The polyester contained in the asphalt modifier of the present invention is a polycondensate of polyethylene terephthalate, an alcohol component, and a carboxylic acid component, and satisfies at least one of the following conditions (i) and (ii): (i) The carboxylic acid component contains a monovalent carboxylic acid. (ii) The alcohol component contains a monovalent alcohol. The content of the structural unit derived from the monobasic carboxylic acid and / or the structural unit derived from the monobasic alcohol in the polyester is 5 mol% or more and 20 mol% or less with respect to the total content of 100 mol% of the structural unit derived from the alcohol component and the structural unit derived from ethylene glycol in polyethylene terephthalate. Hereinafter, the alcohol component, the carboxylic acid component, and polyethylene terephthalate will be described.

[0013] (Alcohol component) Examples of the alcohol component include aliphatic diols, alicyclic diols, aromatic diols, polyhydric alcohols having a valence of 3 or more, and the like. These alcohol components can be used alone or in combination of two or more.

[0014] The aliphatic diol is preferably a linear or branched aliphatic diol having 2 to 12 carbon atoms in the main chain, and more preferably a linear or branched aliphatic diol having 2 to 8 carbon atoms in the main chain. The aliphatic diol is preferably a saturated aliphatic diol. Specific examples of the aliphatic diol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,10-decanediol, and 1,12-dodecanediol.

[0015] Examples of the alicyclic diol include hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane), an alkylene oxide adduct of hydrogenated bisphenol A, cyclohexanediol, and cyclohexanedimethanol.

[0016] Examples of the aromatic diol include bisphenol A (2,2-bis(4-hydroxyphenyl)propane) and an alkylene oxide adduct of bisphenol A. Examples of the alkylene oxide adduct of bisphenol A include an alkylene oxide adduct of bisphenol A represented by the following formula (I).

[0017] [Chemical formula]

[0018] [In the formula, OR 1 and R 1 O is an alkylene oxide, R 1 is an alkylene group having 2 or 3 carbon atoms, x and y represent positive numbers indicating the average number of moles of alkylene oxide added, the sum of x and y is preferably 1 or more, more preferably 1.5 or more, and preferably 16 or less, more preferably 8 or less, still more preferably 4 or less. ]

[0019] Examples of the alkylene oxide adduct of bisphenol A represented by the formula (I) include a propylene oxide adduct of bisphenol A and an ethylene oxide adduct of bisphenol A. These alkylene oxide adducts of bisphenol A can be used alone or in combination of two or more.

[0020] The polyhydric alcohol having a valence of 3 or more is preferably a trihydric alcohol. Examples of the polyhydric alcohol having a valence of 3 or more include glycerin, pentaerythritol, trimethylolpropane, and sorbitol.

[0021] When the alcohol component satisfies the above (ii), it contains a monohydric alcohol. Examples of the monohydric alcohol include monohydric aliphatic alcohols. These monohydric alcohols can be used alone or in combination of two or more. The monohydric aliphatic alcohol may have either a straight-chain or branched-chain main chain. Also, the monohydric aliphatic alcohol is preferably a monohydric saturated aliphatic alcohol. The monohydric aliphatic alcohol preferably has 6 or more carbon atoms, more preferably 10 or more carbon atoms, still more preferably 12 or more carbon atoms, and preferably 100 or less carbon atoms, more preferably 50 or less, and still more preferably 20 or less. Examples of the monohydric alcohol include monohydric aliphatic alcohols such as decanol, lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, arachidyl alcohol, docosanol, etc. These monohydric alcohol components can be used alone or in combination of two or more.

[0022] (Carboxylic acid component) Examples of the carboxylic acid component include aliphatic dicarboxylic acids, aromatic dicarboxylic acids, and polycarboxylic acids having 3 to 6 valences. These carboxylic acid components can be used alone or in combination of two or more.

[0023] Examples of the aliphatic dicarboxylic acid include aliphatic dicarboxylic acids having a main chain with preferably 4 or more carbon atoms and preferably 10 or less carbon atoms, more preferably 8 or less carbon atoms, still more preferably 6 or less carbon atoms, such as fumaric acid, maleic acid, oxalic acid, malonic acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, succinic acid substituted with an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms, or anhydrides thereof, alkyl esters thereof (for example, the alkyl group has 1 to 3 carbon atoms). Examples of the substituted succinic acid include dodecyl succinic acid, dodecenyl succinic acid, and octenyl succinic acid.

[0024] Examples of the aromatic dicarboxylic acid include phthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, or their anhydrides and their alkyl esters (for example, the alkyl group has 1 to 3 carbon atoms). Among the above aromatic dicarboxylic acids, isophthalic acid and terephthalic acid are preferred, and terephthalic acid is more preferred, from the viewpoints of suppressing aggregate scattering and water resistance.

[0025] The polyvalent carboxylic acid having a valence of 3 or more and 6 or less is preferably a trivalent carboxylic acid. Examples of the polyvalent carboxylic acid having a valence of 3 or more and 6 or less include trimellitic acid, 2,5,7-naphthalenetricarboxylic acid, pyromellitic acid, or their acid anhydrides and the like.

[0026] When the carboxylic acid component satisfies the above condition (i), it contains a monovalent carboxylic acid. Examples of the monovalent carboxylic acid include monovalent aliphatic carboxylic acids and monovalent aromatic carboxylic acids. These monovalent carboxylic acids can be used alone or in combination of two or more. Examples of the monovalent aliphatic carboxylic acid include monovalent saturated aliphatic carboxylic acids such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, arachidic acid, and behenic acid; and monovalent unsaturated aliphatic carboxylic acids such as oleic acid, linoleic acid, and linolenic acid. Examples of the monovalent aromatic carboxylic acid include benzoic acid, phenylacetic acid, phenylpropionic acid, cinnamic acid, and naphthoic acid. The monovalent carboxylic acid is preferably a monovalent aromatic carboxylic acid, more preferably benzoic acid.

[0027] (Constituent unit derived from polyethylene terephthalate) The polyester contains polyethylene terephthalate (which may be referred to as "PET" in this specification) as its raw material. That is, the polyester contains a constituent unit derived from ethylene glycol and a constituent unit derived from terephthalic acid, both of which are derived from polyethylene terephthalate. In addition to the structural units derived from ethylene glycol and the structural units derived from terephthalic acid, polyethylene terephthalate may contain a small amount of structural units of components such as butanediol and isophthalic acid. The polyethylene terephthalate is preferably recycled polyethylene terephthalate. In the polyester, the structural units derived from ethylene glycol derived from polyethylene terephthalate and the structural units derived from terephthalic acid derived from polyethylene terephthalate are alternately bonded via ester bonds.

[0028] The content of polyethylene terephthalate in the raw material of the polyester is preferably 5% by mass or more and 80% by mass or less, more preferably 15% by mass or more, still more preferably 25% by mass or more, and more preferably 70% by mass or less, still more preferably 60% by mass or less, based on the total amount of polyethylene terephthalate, the alcohol component and the carboxylic acid component.

[0029] (Molar ratio of the structural units derived from the carboxylic acid component to the structural units derived from the alcohol component) The molar ratio of the structural units derived from the carboxylic acid component to the structural units derived from the alcohol component [carboxylic acid component / alcohol component] is preferably 0.7 or more and 1.5 or less, more preferably 0.8 or more, still more preferably 0.9 or more, and more preferably 1.3 or less, still more preferably 1.1 or less.

[0030] (Content of each preferred structural unit) In a preferred embodiment of the polyester, from the viewpoint of durability, the alcohol component as the raw material of the polyester contains structural units derived from an alkylene oxide adduct of bisphenol A. The alkylene oxide adduct of bisphenol A in the above alcohol component is preferably 60 mol% or more and 100 mol% or less, more preferably 75 mol% or more, still more preferably 90 mol% or more, based on 100 mol% of the alcohol component. The content of the structural unit derived from the alkylene oxide adduct of bisphenol A in the polyester is preferably 10 mol% or more and 70 mol% or less, more preferably 20 mol% or more, still more preferably 30 mol% or more, and more preferably 60 mol% or less, still more preferably 50 mol% or less, based on 100 mol% of the total content of the structural unit derived from the alcohol component and the structural unit derived from ethylene glycol derived from polyethylene terephthalate.

[0031] The polyester contains a structural unit derived from ethylene glycol derived from polyethylene terephthalate. The content of the structural unit derived from ethylene glycol derived from polyethylene terephthalate in the polyester is preferably 50 mol% or more and 80 mol% or less, more preferably 55 mol% or more, and more preferably 70 mol% or less, still more preferably 65 mol% or less, based on 100 mol% of the total content of the structural unit derived from the alcohol component and the structural unit derived from ethylene glycol derived from polyethylene terephthalate.

[0032] The carboxylic acid component as a raw material of the polyester preferably contains an aromatic dicarboxylic acid. The aromatic dicarboxylic acid is preferably terephthalic acid and isophthalic acid, and more preferably terephthalic acid. The polyester contains a structural unit derived from terephthalic acid. The structural unit derived from terephthalic acid may be derived only from the raw material polyethylene terephthalate or may be the case where the raw material carboxylic acid component contains terephthalic acid. The content of the structural unit derived from terephthalic acid in the polyester is preferably 50 mol% or more and 100 mol% or less, more preferably 60 mol% or more, still more preferably 70 mol% or more, and more preferably 95 mol% or less, based on 100 mol% of the total content of the structural unit derived from the alcohol component and the structural unit derived from ethylene glycol derived from polyethylene terephthalate, from the viewpoint of ensuring compatibility with asphaltenes in the asphalt. Also, from the same perspective, the content of the structural unit derived from terephthalic acid in the polyester is preferably 50 mol% or more and 100 mol% or less, more preferably 60 mol% or more, still more preferably 70 mol% or more, and more preferably 95 mol% or less with respect to the total content of 100 mol% of the structural unit derived from the carboxylic acid component and the structural unit derived from terephthalic acid in polyethylene terephthalate.

[0033] The content of the structural unit derived from terephthalic acid in polyethylene terephthalate in the polyester is preferably 50 mol% or more and 80 mol% or less, more preferably 55 mol% or more, and more preferably 70 mol% or less, still more preferably 65 mol% or less with respect to the total content of 100 mol% of the structural unit derived from the alcohol component and the structural unit derived from ethylene glycol in polyethylene terephthalate.

[0034] The raw material of the polyester contains a monovalent carboxylic acid as the carboxylic acid component and / or a monovalent alcohol as the alcohol component. The raw material of the polyester may contain both the monovalent carboxylic acid and the alcohol component or only one of them. Preferably, it contains a monovalent carboxylic acid or an alcohol component, more preferably a monovalent carboxylic acid. The content of the structural unit derived from the monovalent carboxylic acid and / or the structural unit derived from the monovalent alcohol in the polyester is 5 mol% or more and 20 mol% or less, preferably 6 mol% or more, more preferably 7 mol% or more, and preferably 18 mol% or less, more preferably 15 mol% or less with respect to the total content of 100 mol% of the structural unit derived from the alcohol component and the structural unit derived from ethylene glycol in polyethylene terephthalate. When the alcohol component contains a monohydric alcohol, the content of the structural unit derived from the monohydric alcohol in the polyester is preferably 5 mol% or more and 20 mol% or less, more preferably 6 mol% or more, still more preferably 7 mol% or more, and more preferably 18 mol% or less, still more preferably 15 mol% or less, based on 100 mol% of the total content of the structural unit derived from the alcohol component and the structural unit derived from ethylene glycol derived from polyethylene terephthalate. When the carboxylic acid component contains a monohydric carboxylic acid, the content of the structural unit derived from the monohydric carboxylic acid in the polyester is preferably 0.1 mol% or more and 20 mol% or less, more preferably 1 mol% or more, still more preferably 3 mol% or more, and more preferably 15 mol% or less, still more preferably 12 mol% or less, based on 100 mol% of the total content of the structural unit derived from the alcohol component and the structural unit derived from terephthalic acid derived from polyethylene terephthalate.

[0035] (Physical properties of the polyester) From the viewpoint of the durability of asphalt pavement, the softening point of the polyester is preferably 60°C or more and 120°C or less, more preferably 60°C or more, still more preferably 70°C or more, and more preferably 115°C or less, still more preferably 110°C or less, still more preferably 100°C or less. From the same viewpoint, the weight-average molecular weight Mw of the polyester is preferably 3,000 or more and 25,000 or less, more preferably 4,000 or more, still more preferably 5,000 or more, and more preferably 10,000 or less, still more preferably 8,000 or less.

[0036] The softening point, weight-average molecular weight Mw, acid value, and hydroxyl value of the polyester resin can be measured by the methods described in the examples. The softening point, weight-average molecular weight Mw, acid value, and hydroxyl value can be adjusted by the raw material monomer composition, molecular weight, catalyst amount, or reaction conditions.

[0037] The polyester may be a polyester modified to such an extent that its properties are not substantially impaired. Specifically, examples of the modified polyester include polyesters grafted or blocked with phenol, urethane, epoxy, etc. by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, etc. Preferred modified polyester resins include urethane-modified polyesters obtained by extending a polyester with a polyisocyanate compound.

[0038] (Method for producing polyester) The method for producing the polyester is not particularly limited. For example, it can be produced by polycondensing the above-mentioned polyethylene terephthalate, alcohol component, and carboxylic acid component.

[0039] The blending amounts of polyethylene terephthalate, the alcohol component, and the carboxylic acid are such that the molar ratio of the structural unit derived from the carboxylic acid component to the structural unit derived from the alcohol component [carboxylic acid component / alcohol component] is within the above-mentioned numerical range. The content of polyethylene terephthalate in the raw materials of polyethylene terephthalate, the alcohol component, and the carboxylic acid is preferably 5% by mass or more and 80% by mass or less, more preferably 15% by mass or more, still more preferably 25% by mass or more, and more preferably 70% by mass or less, still more preferably 60% by mass or less, based on the total amount of the raw materials.

[0040] By adding polyethylene terephthalate during the polycondensation reaction between the alcohol component and the carboxylic acid component, a transesterification reaction occurs, and a polyester in which the structural units of polyethylene terephthalate are incorporated into the structural units derived from the alcohol component and the structural units derived from the carboxylic acid component can be obtained. Polyethylene terephthalate may be present from the start of the polycondensation reaction or added to the reaction system during the polycondensation reaction. From the perspective of the durability of asphalt pavement, the addition time of polyethylene terephthalate is preferably at a stage where the reaction rate between the alcohol component and the carboxylic acid component is 10% or less, and more preferably 5% or less. The reaction rate refers to the value of (moles of generated reaction water / moles of theoretically generated water) × 100.

[0041] The temperature of the polycondensation reaction is not particularly limited, but from the perspective of reactivity, it is preferably 160 °C or higher and 260 °C or lower, more preferably 190 °C or higher, still more preferably 200 °C or higher, and more preferably 250 °C or lower, still more preferably 240 °C or lower. The polycondensation may be carried out in an inert gas atmosphere.

[0042] For the polycondensation reaction, from the perspective of the reaction rate, a tin (II) compound having no Sn-C bond such as tin (II) bis(2-ethylhexanoate) can be used as an esterification catalyst. The amount of the esterification catalyst used is preferably 0.01 part by mass or more and 1.5 parts by mass or less, more preferably 0.1 part by mass or more, still more preferably 0.2 part by mass or more, and more preferably 1.0 part by mass or less, still more preferably 0.6 part by mass or less, based on 100 parts by mass of the total amount of the raw materials. For the polycondensation reaction, in addition to the esterification catalyst, a pyrogallol compound such as gallic acid can be used as a co-catalyst from the perspective of the reaction rate. The amount of the co-catalyst used is preferably 0.001 part by mass or more and 0.15 part by mass or less, more preferably 0.005 part by mass or more, still more preferably 0.01 part by mass or more, and more preferably 0.10 part by mass or less, still more preferably 0.08 part by mass or less, based on 100 parts by mass of the total amount of the raw materials. For the polycondensation reaction, in addition to the catalyst, a polymerization inhibitor such as 4-tert-butylcatechol can be used. The amount of the polymerization inhibitor used is preferably 0.001 part by mass or more and 0.10 part by mass or less, more preferably 0.01 part by mass or more, and more preferably 0.05 part by mass or less, based on 100 parts by mass of the total amount of the raw materials.

[0043] (Content of polyester in asphalt modifier) The asphalt modifier may consist only of polyester or may contain polyester and other components. The content of polyester in the asphalt modifier is preferably 50% by mass or more and 100% by mass or less, more preferably 70% by mass or more, and still more preferably 85% by mass or more in the total mass of the asphalt modifier.

[0044] The asphalt modifier of the present invention can be used, for example, to be mixed with asphalt to obtain an asphalt composition. After adding heated aggregates to the obtained asphalt composition to form an asphalt mixture, it can be used for paving. The asphalt modifier of the present invention can be suitably used as an asphalt modifier for blending into an asphalt mixture containing aggregates.

[0045] [Asphalt mixture] The asphalt mixture of the present invention contains the above asphalt modifier, asphalt, and aggregates. The asphalt mixture of the present invention may be formed by blending the above asphalt modifier, asphalt, and aggregates.

[0046] [Asphalt]< As asphalt, various types of asphalt can be used. For example, in addition to straight asphalt which is paving petroleum asphalt, modified asphalt can be mentioned. Examples of modified asphalt include blown asphalt; polymer-modified asphalt modified with polymer materials such as thermoplastic elastomers and thermoplastic resins. Straight asphalt refers to the residual asphalt substance obtained by subjecting crude oil to an atmospheric distillation unit, a vacuum distillation unit, etc. Also, blown asphalt means asphalt obtained by heating a mixture of straight asphalt and heavy oil and then blowing air into it for oxidation. The asphalt is preferably selected from straight asphalt and polymer-modified asphalt. From the perspective of the durability of asphalt pavement, polymer-modified asphalt is more preferable, and from the perspective of versatility, straight asphalt is more preferable. As polymer-modified asphalt, asphalt modified with a thermoplastic elastomer is more preferable. The modified asphalt is preferably polymer-modified asphalt, and more preferably polymer-modified asphalt modified with a thermoplastic elastomer.

[0047] (thermoplastic elastomer) Examples of the thermoplastic elastomer in the polymer-modified asphalt modified with a thermoplastic elastomer include at least one selected from styrene / butadiene block copolymers, styrene / butadiene / styrene block copolymers, styrene / butadiene random copolymers, styrene / isoprene block copolymers, styrene / isoprene / styrene block copolymers, styrene / isoprene random copolymers, ethylene / vinyl acetate copolymers, ethylene / acrylic ester copolymers, styrene / ethylene / butylene / styrene copolymers, styrene / ethylene / propylene / styrene copolymers, polyurethane-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers, isobutylene / isoprene copolymers, polyisoprene, polychloroprene, synthetic rubbers other than the above, and natural rubbers. The thermoplastic elastomer in the modified asphalt is preferably at least one selected from styrene / butadiene block copolymers, styrene / butadiene / styrene block copolymers, styrene / butadiene random copolymers, styrene / isoprene block copolymers, styrene / isoprene / styrene block copolymers, styrene / isoprene random copolymers, ethylene / vinyl acetate copolymers, and ethylene / acrylic ester copolymers. Among these, as the thermoplastic elastomer, from the viewpoint of the durability of asphalt pavement, preferably at least one selected from styrene / butadiene block copolymers, styrene / butadiene / styrene block copolymers, styrene / butadiene random copolymers, styrene / isoprene block copolymers, styrene / isoprene / styrene block copolymers, styrene / isoprene random copolymers, and ethylene / acrylic ester copolymers; more preferably at least one selected from styrene / butadiene block copolymers, styrene / butadiene / styrene block copolymers, styrene / butadiene random copolymers, styrene / isoprene block copolymers, and styrene / isoprene random copolymers; still more preferably at least one selected from styrene / butadiene random copolymers and styrene / butadiene / styrene block copolymers. The content of the thermoplastic elastomer in the polymer-modified asphalt is preferably 0.1% by mass or more and 30% by mass or less, more preferably 0.5% by mass or more, still more preferably 1% by mass or more, and more preferably 20% by mass or less, still more preferably 10% by mass or less, from the viewpoints of the durability and surface appearance of the asphalt pavement.

[0048] [Aggregate] The asphalt mixture of the present invention may contain aggregate. As specific aggregates, for example, crushed stone, cobblestone, gravel, sand, ceramics, etc. can be arbitrarily selected and used. Further, as the aggregate, coarse aggregate having a particle size of 2.36 mm or more, fine aggregate having a particle size of 0.075 mm or more and less than 2.36 mm, and filler having a particle size of less than 0.075 mm can be used.

[0049] Examples of the coarse aggregate include crushed stone having a particle size range of 2.36 mm or more and less than 4.75 mm, crushed stone having a particle size range of 4.75 mm or more and less than 12.5 mm, crushed stone having a particle size range of 12.5 mm or more and less than 19 mm, and crushed stone having a particle size range of 19 mm or more and less than 31.5 mm. Examples of the fine aggregate include river sand, hill sand, mountain sand, sea sand, crushed sand, fine sand, screenings, crushed stone dust, silica sand, artificial sand, glass cullet, and foundry sand. The particle sizes of the coarse aggregate and the fine aggregate are values based on the sieving test method defined in JIS A5001:2008. Examples of the filler include sand, fly ash, calcium carbonate powder such as limestone powder, and slaked lime. Among these, calcium carbonate powder is preferable from the viewpoint of improving the strength of the asphalt pavement. The average particle size of the filler is preferably 0.001 mm or more, and preferably 0.05 mm or less, more preferably 0.03 mm or less, still more preferably 0.02 mm or less, from the viewpoint of improving the strength of the asphalt pavement. Here, the average particle size means the average particle size (D 50 ) at 50% volume cumulative, and can be measured by a laser diffraction particle size distribution measuring device.

[0050] As aggregates, it is preferable to use coarse aggregates and fine aggregates in combination. In this case, the mass ratio of the coarse aggregate to the fine aggregate (coarse aggregate / fine aggregate) is preferably 10 / 90 or more and 90 / 10 or less, more preferably 15 / 85 or more, still more preferably 20 / 80 or more, and more preferably 80 / 20 or less, still more preferably 70 / 30 or less, from the viewpoint of the durability of the asphalt pavement.

[0051] The asphalt mixture of the present invention can contain asphalt recycled aggregates as aggregates. The aggregates may not contain fresh aggregates and may be composed only of asphalt recycled aggregates. Asphalt recycled aggregates are those obtained by collecting used asphalt pavement bodies, crushing and classifying them. The used asphalt pavement body from which the asphalt recycled aggregates are derived contains asphalt and aggregates, and can contain other additives as necessary.

[0052] The asphalt contained in the asphalt recycled aggregates has deteriorated physical and chemical properties compared to fresh asphalt due to the influence of environmental factors such as heat and light. The physical and chemical properties of asphalt can be evaluated by measuring the penetration, softening point, bending strength, strain at break, asphalt composition, etc. of the asphalt. Generally, asphalt in which the maltene fraction in the asphalt has migrated to asphaltene and the penetration has decreased is often called deteriorated asphalt. However, even if the penetration of the recycled asphalt is equivalent to that of the fresh asphalt, there are cases where the performance equivalent to that of the fresh asphalt cannot be exhibited due to changes in other properties.

[0053] The asphalt mixture derived from the used asphalt pavement body contains aggregates. Examples of such aggregates include aggregates generally used in asphalt mixtures for road pavement such as crushed stone, cobblestone, gravel, sand, and ceramics. Further, the asphalt mixture itself derived from the used asphalt pavement body may use asphalt recycled aggregates as aggregates.

[0054] <Content of each component> From the viewpoint of achieving both durability and flexibility, the content of asphalt in the asphalt mixture is preferably 1% by mass or more and 20% by mass or less, more preferably 3% by mass or more, still more preferably 4% by mass or more, and further preferably 15% by mass or less, still more preferably 10% by mass or less.

[0055] In the present invention, when the aggregate contains asphalt recycled aggregate, the content of asphalt means the total content of fresh asphalt, which is asphalt having no history of being used in asphalt pavement, and the asphalt contained in the asphalt recycled aggregate. In the present invention, the asphalt contained in the asphalt recycled aggregate is also referred to as asphalt derived from recycled aggregate in order to distinguish it from fresh asphalt. Asphalt derived from recycled aggregate is sometimes referred to as deteriorated asphalt. From the viewpoint of achieving both durability and flexibility, the content of fresh asphalt in the asphalt is preferably 50% by mass or more and 80% by mass or less, more preferably 60% by mass or more, and further preferably 70% by mass or less. The content of asphalt derived from recycled aggregate in the asphalt is preferably 20% by mass or more and 50% by mass or less, more preferably 30% by mass or more, and further preferably 40% by mass or less from the viewpoint of achieving both durability and flexibility. The content of asphalt derived from recycled aggregate in the asphalt recycled aggregate can be measured by a solvent extraction method or a loss on ignition method. Usually, the content of asphalt contained in asphalt recycled aggregate derived from used asphalt pavement is approximately 5.5% by mass. In the present invention, the content of asphalt derived from recycled aggregate is determined according to the method specified in AASHTO (American Association of State Highway and Transportation Officials) T 308-10 (2015), which is a loss on ignition measurement. Since the aggregate contains asphalt recycled aggregate, the amount of asphalt is determined from the loss on ignition of the asphalt recycled aggregate and used in the formulation calculation.

[0056] The content of the asphalt modifier in the asphalt mixture is preferably 3 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of asphalt. From the viewpoint of durability, it is more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, and from the viewpoint of maintaining flexibility, it is more preferably 20 parts by mass or less, still more preferably 15 parts by mass or less.

[0057] The content of the aggregate in the asphalt mixture is preferably 50% by mass or more and 99% by mass or less, more preferably 75% by mass or more, still more preferably 80% by mass or more, and from the viewpoint of achieving both durability and flexibility, it is more preferably 98% by mass or less, still more preferably 96% by mass or less.

[0058] In the present invention, when the aggregate includes recycled asphalt aggregate, the content of the aggregate means the total content of the new aggregate and the recycled asphalt aggregate. Note that the content of the asphalt derived from the recycled aggregate is included in the content of the aggregate. When the aggregate includes a new aggregate and a recycled asphalt aggregate, the content of the new aggregate is preferably 40 parts by mass or more and 80 parts by mass or less in 100 parts by mass of the total content of the new aggregate and the recycled asphalt aggregate from the viewpoint of achieving both the use of the recycled asphalt aggregate and excellent pavement physical properties, more preferably 50 parts by mass or more, and from the viewpoint of achieving both the use of the recycled asphalt aggregate and excellent pavement physical properties, more preferably 75 parts by mass or less. The content of the recycled asphalt aggregate is preferably 15 parts by mass or more and 60 parts by mass or less in 100 parts by mass of the total content of the new aggregate and the recycled asphalt aggregate from the viewpoint of reusing waste materials of asphalt pavement, more preferably 25 parts by mass or more, and from the viewpoint of achieving both the use of the recycled asphalt aggregate and excellent pavement physical properties, more preferably 50 parts by mass or less.

[0059] Examples of suitable aggregate blends in asphalt mixtures include the following (1) to (3). (1) Fine-grained asphalt containing 30% by volume or more and less than 45% by volume of coarse aggregate, 30% by volume or more and 50% by volume or less of fine aggregate, and 5% by volume or more and 10% by volume or less of an asphalt composition. (2) An example of an asphalt mixture is, for example, dense-grained asphalt containing 45% by volume or more and less than 70% by volume of coarse aggregate, 20% by volume or more and 45% by volume or less of fine aggregate, and 3% by volume or more and 10% by volume or less of an asphalt composition. (3) Porous asphalt containing 70% by volume or more and 80% by volume or less of coarse aggregate, 10% by volume or more and 20% by volume or less of fine aggregate, and 3% by volume or more and 10% by volume or less of an asphalt composition. Regarding the blending ratio of asphalt in a conventional asphalt mixture containing aggregate and asphalt, it is usually used in accordance with the optimum asphalt amount determined from the "Blending Design of Asphalt Composition" described in the "Pavement Design and Construction Guidelines" issued by the Japan Road Association, a public interest incorporated association. In the present invention, the above optimum asphalt amount corresponds to the total amount of asphalt and asphalt modifier. However, it is not necessary to be limited to the method described in the "Pavement Design and Construction Guidelines", and it may be determined by other methods.

[0060] [Method for producing asphalt mixture] The method for producing the asphalt mixture of the present invention includes a step of mixing the above asphalt modifier, asphalt, and aggregate under heating conditions. In the mixing step, the asphalt modifier, asphalt, and aggregate can be mixed simultaneously or in any order. From the viewpoints of the durability and flexibility of asphalt pavement, preferably, the above asphalt modifier is mixed with the aggregate simultaneously with or after the asphalt. The mixing under heating conditions is preferably in a mode using heated aggregate. When the asphalt mixture contains new aggregate and asphalt recycled aggregate, the new aggregate and the asphalt recycled aggregate can be mixed and used, for example, so as to have the above contents. Specific production methods of asphalt mixtures include conventional production methods of asphalt mixtures such as the plant mix method and the premix method. All of them are methods of adding asphalt and asphalt modifiers to heated aggregates. The premix method is an addition method in which asphalt and asphalt modifiers are dissolved in advance. The plant mix method is an addition method in which asphalt is added to heated aggregates, and then the above asphalt modifiers are added simultaneously or in any order. Among these, from the viewpoint of exerting asphalt performance, the plant mix method is preferable. More specifically, the production method of the asphalt mixture preferably includes, in the mixing step, (i) After adding and mixing asphalt to heated aggregates to obtain a mixture, adding and mixing the above asphalt modifier, (ii) Simultaneously adding and mixing asphalt and the above asphalt modifier to heated aggregates, or (iii) Adding and mixing pre-heated and mixed asphalt and the above asphalt modifier to heated aggregates. Among these, the mixing step preferably uses the method of (i).

[0061] From the viewpoint of improving durability by sufficient mixing, the heating temperature is preferably 130°C or higher and 350°C or lower, more preferably 140°C or higher, and still more preferably 145°C or higher. And from the viewpoint of performance stability, it is preferably 350°C or lower, more preferably 250°C or lower, and still more preferably 200°C or lower. Even when the asphalt mixture of the present invention is mixed in the so-called medium temperature range, an asphalt pavement having excellent durability can be obtained. The mixing conditions in the medium temperature range are preferably 160°C or lower. In addition, the mixing time is not particularly limited. From the viewpoint of efficiently and uniformly dispersing the asphalt modifier in asphalt and exerting asphalt performance, it is preferably 30 seconds or more, more preferably 1 minute or more, still more preferably 2 minutes or more, and even more preferably 5 minutes or more. The upper limit of the time is not particularly limited and is preferably about 30 minutes.

[0062] The method for preparing the mixture is not particularly limited, but it is preferable to include a step of heating and melting asphalt, adding the above asphalt modifier and, if necessary, other additives, and stirring and mixing with a commonly used mixer until each component is uniformly dispersed. Examples of commonly used mixers include a homomixer, a dissolver, a paddle mixer, a ribbon mixer, a screw mixer, a planetary mixer, a drum mixer, a twin-screw forced mixer, a pugmill mixer, a vacuum countercurrent mixer, a roll mill, a twin-screw extruder, and the like.

[0063] The asphalt mixture of the present invention may be used as a heated asphalt mixture substantially free of water. Alternatively, an emulsifier or water may be blended into the above asphalt mixture to form an asphalt emulsion, and aggregate or the like may be blended therewith to be used as a normal-temperature asphalt mixture. The asphalt mixture of the present invention is preferably used as heated asphalt. From the viewpoint of exhibiting asphalt performance, the asphalt mixture preferably contains substantially no water.

[0064] There is no particular limitation on the method for producing the asphalt mixture when it is used as a heated asphalt mixture, and it may be produced by any method. Usually, it may be carried out according to the method for producing an asphalt mixture containing aggregate and an asphalt composition.

[0065] [Pavement construction method] The asphalt mixture of the present invention is suitable for paving. The pavement construction method of the present invention preferably has a step of constructing the asphalt mixture of the present invention on a paving target such as a road or a parking lot to form an asphalt paving material layer. The asphalt paving material layer is usually a base layer or a surface layer, and is preferably a surface layer from the viewpoint of exhibiting the effect of durability.

[0066] In the road paving method, the asphalt mixture may be compacted by the same method with the same construction machinery composition as that of a normal asphalt mixture. When used as a heated asphalt mixture, the compaction temperature of the asphalt mixture is preferably 100 °C or higher, more preferably 120 °C or higher, still more preferably 130 °C or higher, and preferably 200 °C or lower, more preferably 180 °C or lower, still more preferably 170 °C or lower, from the viewpoint of exhibiting asphalt performance.

Example

[0067] Regarding various physical properties, measurement and evaluation were performed by the following methods. In the following examples and comparative examples, parts and % are based on mass unless otherwise specified.

[0068] (1) Softening point (Ts) of polyester Using a flow tester "CFT-500D" (manufactured by Shimadzu Corporation), while heating 1 g of the sample at a heating rate of 6 °C / min, a load of 1.96 MPa was applied by a plunger, and it was extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. The plunger drop amount of the flow tester was plotted against the temperature, and the temperature at which half of the sample flowed out was taken as the softening point.

[0069] (2) Molecular weight of polyester The weight average molecular weight was determined by gel permeation chromatography (GPC) method by the following method. (i) Preparation of sample solution The sample was dissolved in chloroform at 40 °C so that the concentration became 0.5 g / 100 mL. Then, this solution was filtered using a PTFE type membrane filter "DISMIC-25JP" (manufactured by Toyo Roshi Kaisha, Ltd.) with a pore size of 0.20 μm to remove insoluble components, and a sample solution was obtained. (ii) Molecular weight measurement Using the following measuring device and analytical column, chloroform was used as the eluent and flowed at a flow rate of 1 mL per minute to stabilize the column in a constant temperature bath at 40°C. 200 μL of the sample solution was injected therein for measurement. The molecular weight of the sample was calculated based on a calibration curve prepared in advance. For the calibration curve at this time, several types of monodisperse polystyrenes (A-500 (5.0×10 2 ), A-1000 (1.01×10 3 ), A-2500 (2.63×10 3 ), A-5000 (5.97×10 3 ), F-1 (1.02×10 4 ), F-2 (1.81×10 4 ), F-4 (3.97×10 4 ), F-10 (9.64×10 4 ), F-20 (1.90×10 5 ), F-40 (4.27×10 5 ), F-80 (7.06×10 5 ), F-128 (1.09×10 6 )) manufactured by Tosoh Corporation were used as standard samples. The values in parentheses indicate the molecular weights. Measuring device: "HLC-8320GPC" (manufactured by Tosoh Corporation) Analytical column: "TSKgel Super HZM" + "TSKgel Super H-RC" × 2 (manufactured by Tosoh Corporation)

[0070] Production Examples 1 to 4, 9 to 10 (Polyester A1 to A4, B2 to B3) Raw materials other than the alkenyl succinic anhydride shown in Table 1 were placed in a 10-liter four-necked flask equipped with a thermometer, a stainless steel stirring rod, a reflux condenser, and a nitrogen inlet tube. Under a nitrogen atmosphere, the amount of tin(II) bis(2-ethylhexanoate) shown in Table 1 was added, and the temperature was raised to 235°C over 6 hours in a mantle heater. After reaching 235°C, it was held for 5 hours. After visually confirming that the PET pellets had disappeared from the reaction product, it was cooled to 180°C. After cooling to 180°C, alkenyl succinic anhydride was added, the temperature was raised to 210°C over 2 hours, held at 210°C for 1 hour, and after carrying out a reaction under reduced pressure at 8.3 kPa, the reaction was carried out until the softening point shown in Table 1 was reached, and the target polyesters A1 to A4, B2 to B3 were obtained.

[0071] Production Examples 5 to 6 (Polyesters A5 to A6) Raw materials other than the alkenyl succinic anhydride shown in Table 1 were placed in a 10-liter four-necked flask equipped with a thermometer, a stainless steel stirring rod, a reflux condenser, and a nitrogen inlet tube. Under a nitrogen atmosphere, the amount of tin(II) bis(2-ethylhexanoate) shown in Table 1 was added, and the temperature was raised to 235°C over 4 hours in a mantle heater. After reaching 235°C, it was held for 5 hours. After visually confirming that the PET pellets had disappeared from the reaction product, it was cooled to 180°C. After cooling to 180°C, alkenyl succinic anhydride was added, the temperature was raised to 210°C over 2 hours, held at 210°C for 1 hour, and after carrying out a reaction under reduced pressure at 8.3 kPa, the reaction was carried out until the softening point shown in Table 1 was reached, and the target polyesters A5 to A6 were obtained.

[0072] Production Example 7 (Polyester A7) Raw materials other than the alkenyl succinic anhydride shown in Table 1 were placed in a 10-liter four-necked flask equipped with a thermometer, a stainless steel stirring rod, a reflux condenser, and a nitrogen inlet tube. Under a nitrogen atmosphere, the amount of tin(II) bis(2-ethylhexanoate) shown in Table 1 was added, and the temperature was raised to 235°C over 6 hours in a mantle heater. After reaching 235°C, it was held for 5 hours. After visually confirming that the PET pellets had disappeared from the reaction product, it was cooled to 180°C. After cooling to 180°C, alkenyl succinic anhydride was added, the temperature was raised to 210°C over 2 hours, held at 210°C for 1 hour, and after carrying out a reaction under reduced pressure at 8.3 kPa, the reaction was carried out until the softening point shown in Table 1 was reached, and the target polyester A7 was obtained.

[0073] Production Example 8 (Polyester B1) Raw materials other than the alkenyl succinic anhydride shown in Table 1 were placed in a 10-liter four-necked flask equipped with a thermometer, a stainless steel stirring rod, a reflux condenser, and a nitrogen inlet tube. Under a nitrogen atmosphere, the amount of tin(II) bis(2-ethylhexanoate) shown in Table 1 was added, and the temperature was raised to 235°C over 3 hours in a mantle heater. After reaching 235°C, it was held for 5 hours. After visually confirming that the PET pellets had disappeared from the reaction product, it was cooled to 180°C. After cooling to 180°C, alkenyl succinic anhydride was added, the temperature was raised to 210°C over 2 hours, held at 210°C for 1 hour, and after carrying out a reaction under reduced pressure at 8.3 kPa, the reaction was carried out until the softening point shown in Table 1 was reached, and the target polyester B1 was obtained.

[0074] Production Example 11 (Polyester B4) Among the raw material monomers shown in Table 1, the alcohol component, terephthalic acid, and stearic acid were placed in a 10-L four-necked flask equipped with a thermometer, a stainless-steel stirring rod, a dehydration tube, a down-flow condenser, and a nitrogen inlet tube. Tin(II) bis(2-ethylhexanoate) and gallic acid were added, and the temperature was raised to 235°C over 4 hours under a nitrogen atmosphere and held at 235°C for 5 hours. Then, a vacuum reaction was carried out at 8.0 kPa for 1 hour. After cooling to 180°C, alkenyl succinic anhydride was added, the temperature was raised to 210°C over 2 hours, held at 210°C for 1 hour, depressurized to 8.3 kPa, and the reaction was carried out until the softening point shown in Table 1 was reached to obtain the target polyester B4.

[0075]

Table 1

[0076] Example 1-1 15 kg of aggregate heated to 150°C (for the composition of the aggregate, see below) was placed in an asphalt mixer and mixed at 150°C for 60 seconds. Next, 820 g of straight asphalt (60 - 80) (manufactured by Mitsubishi Corporation Energy Co., Ltd.) was added and mixed in the asphalt mixer for 1 minute. Then, 82 g of polyester A1 was added and mixed in the asphalt mixer for 2 minutes. The obtained asphalt mixture was quickly filled into a mold of 300 mm × 300 mm × 50 mm, and using a roller compactor (manufactured by Iwata Kogyosho Co., Ltd.), a compaction treatment was carried out at a temperature of 150°C and a load of 0.44 kPa for 25 rotations, and heat curing was carried out at 150°C for 1 hour to prepare an asphalt specimen. Also, 1.2 kg of asphalt mixture was weighed, and a cylindrical specimen was prepared with a Marshall test equipped compactor (manufactured by Nakajima Gihann Co., Ltd., "Automatic Asphalt Compactor"). The specimen was slowly cooled to room temperature and demolded by a demolding machine.

[0077] <Composition of Aggregate> No. 6 crushed stone 40.0 parts by mass No. 7 crushed stone 13.0 parts by mass Crushed sand 10.0 parts by mass River sand: 22.0 parts by mass Mountain sand: 10.0 parts by mass Stone powder (calcium carbonate): 5.0 parts by mass Passing mass percentage: Sieve size 15 mm: 100% by mass Sieve size 10 mm: 88.7% by mass Sieve size 5 mm: 60.5% by mass Sieve size 2.5 mm: 42.6% by mass Sieve size 1.2 mm: 29.9% by mass Sieve size 0.6 mm: 19.8% by mass Sieve size 0.3 mm: 11.5% by mass Sieve size 0.15 mm: 6.2% by mass

[0078] [Evaluation] The asphalt specimen was subjected to the following evaluation tests. <Measurement of rut depth (wheel tracking test)> The asphalt specimen kept warm in a 60°C constant temperature chamber for 5 hours was used with a wheel tracking tester (manufactured by Iwata Kogyosho Co., Ltd., load 1716 N, iron wheel width 47 mm, linear pressure 291.5 N / cm) to reciprocate the wheel on the specimen at a speed of 15 reciprocations / min, and the displacement amount at 800 reciprocation times of passing was measured. Other measurement conditions were in accordance with the "B003 Wheel Tracking Test" described in the "Pavement Survey and Test Method Handbook" published by the Japan Road Association, a public interest incorporated foundation. Note that the rut depth in the wheel tracking test is an index of the durability of asphalt pavement. The results are shown in Table 2.

[0079] <Measurement of void ratio> The void ratio of the demolded cylindrical specimen was measured in accordance with the "B008-1 Density Test Method for Dense-Graded Asphalt Mixtures, etc." described in the "Pavement Survey and Test Method Handbook" published by the Japan Road Association, a public interest incorporated foundation. Note that the void ratio is an index of workability. When the void ratio is 6.0% or more, it is out of specification. The results are shown in Table 2.

[0080] Examples 1-2 to 1-7, Comparative Examples 1-1 to 1-5 An asphalt specimen was prepared in the same manner as in Example 1-1, except that the formulation shown in Table 2 was changed, and the rut depth and void ratio were measured. The results are shown in Table 2.

[0081]

Table 2

[0082] Example 2-1 15 kg of aggregate heated to 150°C (see the following for the aggregate composition) was placed in an asphalt mixer and mixed at 150°C for 60 seconds. Then, 378 g of straight asphalt (80-100) (manufactured by Mitsubishi Corporation Energy Co., Ltd.) was added and mixed in the asphalt mixer for 1 minute. Then, 79 g of polyester A2 was added and mixed in the asphalt mixer for 2 minutes. The obtained asphalt mixture was quickly filled into a mold of 300×300×50 mm, and using a roller compactor (manufactured by Iwata Kogyosho Co., Ltd.), 25 rotations of compaction treatment were performed at a temperature of 150°C and a load of 0.44 kPa, and heat curing was carried out at 150°C for 1 hour to prepare an asphalt specimen. Also, 1.2 kg of asphalt mixture was weighed, and a cylindrical specimen was prepared with a Marshall test compactor (manufactured by Nakajima Gihankai Co., Ltd., "Asphalt Automatic Compactor"). The specimen was gradually cooled to room temperature and demolded using a demolding machine.

[0083] <Composition of Aggregate> No. 6 crushed stone: 30.0 parts by mass No. 7 crushed stone: 8.0 parts by mass Crushed sand: 3.0 parts by mass River sand: 6.0 parts by mass Mountain sand: 3.0 parts by mass Asphalt recycled aggregate: 50.0 parts by mass

[0084] Passing mass %: Sieve size 15 mm: 100 mass % Sieve size 10 mm: 82.9 mass % Sieve size 5 mm: 58.1 mass% Sieve size 2.5 mm: 39.8 mass% Sieve size 1.2 mm: 28.4 mass% Sieve size 0.6 mm: 15.9 mass% Sieve size 0.3 mm: 8.4 mass% Sieve size 0.15 mm: 2.6 mass%

[0085] The asphalt content in 7.5 kg of the asphalt recycled aggregate was 411 g. The asphalt content contained in the asphalt recycled aggregate was determined according to the method specified in AASHTO T 308-10 (2015). Therefore, the total content of the new asphalt and the asphalt derived from the recycled aggregate in the asphalt mixture was 789 g, and the total amount of the new asphalt and the asphalt derived from the recycled aggregate in the asphalt mixture was 5.0 mass%. The content of polyester resin A2 in the asphalt mixture was 10 parts by mass with respect to 100 parts by mass of the total content of the new asphalt and the asphalt derived from the recycled aggregate.

[0086] [Evaluation] The asphalt specimen was measured for rutting excavation amount and porosity in the same manner as in Example 1-1. The results are shown in Table 3.

[0087] Examples 2-2 to 2-3, Comparative Examples 2-1 to 1-3 An asphalt specimen was prepared in the same manner as in Example 2-1 except that the formulation shown in Table 2 was changed, and the rutting excavation amount and porosity were measured. The results are shown in Table 3.

[0088]

Table 3

[0089] Examples 1-1 to 1-7 show that the amount of rutting is significantly reduced compared to Comparative Examples 1-1 to 1-5, and excellent durability is exhibited even in the medium temperature range. Also, when comparing Comparative Example 1-2 with Comparative Example 1-1, although the amount of rutting is reduced, the porosity is significantly improved, and the workability is significantly deteriorated. In contrast, Examples 1-1 to 1-7 show a trend similar to that of Comparative Example 1-1, indicating good workability. From the above, it is possible to achieve both excellent durability and workability even in the medium temperature range according to the present invention. Similar tendencies were also observed for Examples 2-1 to 2-3 which were formulations using asphalt recycled aggregates.

Claims

1. An asphalt modifier containing polyester, wherein the polyester is a polycondensate of polyethylene terephthalate, an alcohol component, and a carboxylic acid component, and satisfies at least one of the following conditions (i) and (ii): (i) The carboxylic acid component contains a monovalent carboxylic acid (ii) The alcohol component contains a monovalent alcohol An asphalt modifier, wherein the content of the structural unit derived from the monovalent carboxylic acid and / or the structural unit derived from the monovalent alcohol in the polyester is 5 mol% or more and 20 mol% or less with respect to the total content of 100 mol% of the structural unit derived from the alcohol component and the structural unit derived from ethylene glycol derived from polyethylene terephthalate.

2. The asphalt modifier according to claim 1, wherein the content of the structural unit derived from ethylene glycol derived from polyethylene terephthalate in the polyester is 50 mol% or more and 80 mol% or less with respect to the total content of 100 mol% of the structural unit derived from the alcohol component and the structural unit derived from ethylene glycol derived from polyethylene terephthalate.

3. The asphalt modifier according to claim 1 or 2, wherein the carboxylic acid component contains an aromatic dicarboxylic acid.

4. The asphalt modifier according to any one of claims 1 to 3, wherein the monovalent carboxylic acid is a monovalent aromatic carboxylic acid.

5. The asphalt modifier according to any one of claims 1 to 4, wherein the softening point of the polyester is 100°C or lower.

6. An asphalt mixture containing the asphalt modifier according to any one of claims 1 to 5, asphalt, and aggregates.

7. The asphalt mixture according to claim 6, wherein the asphalt is straight asphalt or modified asphalt.

8. The asphalt mixture according to claim 7, wherein the modified asphalt is a polymer-modified asphalt modified with a thermoplastic elastomer.

9. The asphalt mixture according to claim 8, wherein the thermoplastic elastomer is at least one selected from the group consisting of a styrene / butadiene block copolymer, a styrene / butadiene / styrene block copolymer, a styrene / butadiene random copolymer, a styrene / isoprene block copolymer, a styrene / isoprene / styrene block copolymer, a styrene / isoprene random copolymer, an ethylene / vinyl acetate copolymer, and an ethylene / acrylic acid ester copolymer.

10. A method for producing an asphalt mixture, comprising a step of mixing the asphalt modifier according to any one of claims 1 to 5, asphalt, and aggregates at 160 °C or lower.

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