JP7542402B2 - Asphalt Composition - Google Patents

Description

The present invention relates to an asphalt composition used for road paving, an asphalt mixture and its manufacturing method, a pavement, and a road paving method.

2. Description of the Related Art Asphalt pavement using an asphalt composition is used for paving roads, parking lots, freight yards, sidewalks, etc. because it is relatively easy to lay and the time from the start of paving work to the start of traffic is short.
Asphalt pavement has a road surface formed from an asphalt mixture in which aggregate is bound with asphalt, so the paved road has good hardness and durability.
However, asphalt pavement surfaces develop ruts and cracks over time, making it necessary to repair the pavement, which increases maintenance costs and has a significant impact on automobile traffic.

Patent Document 1 discloses an asphalt composition containing asphalt, a thermoplastic elastomer, and a polyester, the polyester having a softening point of 90° C. or higher and 140° C. or lower and a glass transition point of 40° C. or higher and 80° C. or lower, and the ratio of the polyester is 1 part by mass or higher and 17 parts by mass or lower per 100 parts by mass of asphalt, for the purpose of providing an asphalt composition that provides excellent durability of pavement surfaces after construction.
Patent Document 2 discloses a road paving composition that contains an aqueous dispersion of a resin (A) having an acid value of 3 to 100 KOHmg/g neutralized with a basic compound, and a silane coupling agent having an alkoxy group having 1 to 5 carbon atoms and an amino group, and that constitutes a binder for aggregates in road paving or a surface layer of a pavement, with the aim of providing a road paving composition that can be applied at room temperature, develops sufficient strength soon after application, and enables efficient formation or repair of a pavement.
Patent Document 3 discloses a highly durable additive for heated bitumen, which is made of a specific divalent carboxylic acid or its anhydride, for the purpose of strengthening the adhesion between bitumen and aggregate, thereby exerting an extremely excellent anti-stripping effect on the bitumen.

JP 2019-019325 A JP 2005-126998 A Japanese Patent Application Publication No. 07-278439

Conventionally, when a composition containing asphalt and polyester is used, an asphalt composition with high dry strength is obtained, but there is a demand for an asphalt composition that can form a pavement surface that is more resistant to ruts and has excellent rut resistance and high resistance to peeling.
In addition, calcium chloride, which is often used as a snow-melting agent on roads in snowy regions, is a cause of deterioration of asphalt pavement because its aqueous solution is alkaline. However, conventional techniques tend to have insufficient resistance to peeling under alkaline conditions, so there is a particular demand for asphalt compositions that can form pavement surfaces that are highly resistant to peeling even under alkaline conditions.
The present invention relates to an asphalt composition having excellent rut resistance and high resistance to peeling, particularly under alkaline conditions, on the pavement surface after construction, an asphalt mixture and a method for producing the same, a pavement, and a method for paving a road.

The present invention relates to the following [1] to [5].
[1] An asphalt composition containing asphalt and polyester,
The asphalt composition, wherein the polyester contains structural units derived from a carboxylic acid component containing at least one selected from alkyl succinic acids and alkenyl succinic acids.
[2] An asphalt mixture comprising the asphalt composition according to [1] above and aggregate.
[3] A pavement paved with the asphalt mixture described in [2] above.
[4] A method for paving a road, comprising the step of applying the asphalt mixture according to [2] above to a road to form an asphalt pavement layer.
[5] A method for producing an asphalt mixture, comprising a step of mixing heated aggregate, asphalt, and a polyester, wherein the polyester comprises a constituent unit derived from a carboxylic acid component containing at least one selected from an alkyl succinic acid and an alkenyl succinic acid.

The present invention provides an asphalt composition, an asphalt mixture and a method for producing the same, a pavement, and a road paving method that provide excellent rut resistance on the pavement surface after construction and high resistance to peeling even under alkaline conditions.

[Asphalt composition]
The asphalt composition of the present invention (hereinafter also simply referred to as "asphalt composition") contains asphalt and a polyester. The polyester contains structural units derived from a carboxylic acid component containing at least one selected from an alkylsuccinic acid and an alkenylsuccinic acid.
According to the above, an asphalt composition having excellent rut resistance of the pavement surface after construction (hereinafter, simply referred to as "rut resistance") can be obtained. Furthermore, by applying this technology, it is possible to provide an asphalt mixture and a manufacturing method thereof, a pavement, and a road paving method.

The reason why the present invention has an advantageous effect is not clear, but is thought to be as follows.
It is presumed that in asphalt compositions containing polyester, asphaltene and polyester are compatible with each other, strengthening the adhesion at the aggregate interface. However, polyester has a carboxylic acid end that is highly hydrophilic and neutralizes under alkaline conditions, so there is a problem that the stability under alkaline conditions is insufficient. In the present invention, by using a polyester containing a structural unit derived from a carboxylic acid component containing at least one selected from alkylsuccinic acid and alkenylsuccinic acid in an asphalt mixture, alkyl or alkenyl groups that are highly hydrophobic and have a high degree of freedom can be localized to cover the asphaltene or polyester hydrophilic part. As a result, it is presumed that alkali infiltration into the aggregate interface can be suppressed, and as a result, a highly stable and strong aggregate interface can be maintained even under alkaline conditions.

The definitions of various terms used in this specification are given below.
The term "binder mixture" refers to a mixture containing asphalt and a thermoplastic elastomer, and is a concept that includes, for example, asphalt modified with the thermoplastic elastomer described below (hereinafter also referred to as "modified asphalt").
In the polyester, a "structural unit derived from an alcohol component" means a structure obtained by removing a hydrogen atom from a hydroxyl group of an alcohol component, and a "structural unit derived from a carboxylic acid component" means a structure obtained by removing a hydroxyl group from a carboxyl group of a carboxylic acid component.
The term "carboxylic acid compound" is a concept that includes not only the carboxylic acid itself, but also anhydrides that decompose during a reaction to generate an acid, and alkyl esters of carboxylic acids (for example, alkyl groups having 1 to 3 carbon atoms). When the carboxylic acid compound is an alkyl ester of a carboxylic acid, the number of carbon atoms of the alkyl group that is the alcohol residue of the ester is not included in the number of carbon atoms of the carboxylic acid compound.

〔asphalt〕
As the asphalt, for example, various asphalts can be used. For example, in addition to straight asphalt, which is petroleum asphalt for paving, modified asphalt can be mentioned. Modified asphalts include blown asphalt; asphalt modified with polymeric materials such as thermoplastic elastomers and thermoplastic resins. Straight asphalt means residual bituminous material obtained by treating crude oil with an atmospheric distillation unit, a vacuum distillation unit, etc. In addition, blown asphalt means asphalt obtained by heating a mixture of straight asphalt and heavy oil, and then blowing air into it to oxidize it. From the viewpoint of rut resistance, modified asphalt is preferred.

The asphalt has an asphaltene content of preferably 15 mass% or more, more preferably 18 mass% or more, and even more preferably 22 mass% or more, per 100 mass% of asphalt, from the viewpoint of improving the durability of the pavement surface after construction, i.e., rut resistance, and from the viewpoint of crack resistance, the asphalt is preferably 40 mass% or less, more preferably 38 mass% or less, and even more preferably 36 mass% or less.
The asphaltene content in asphalt is a value measured in accordance with Japan Petroleum Institute standard JPI-5S-22-83 "Asphaltene Composition Analysis Method by Column Chromatography."

From the viewpoint of improving rut resistance, the content of asphalt in the asphalt composition is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 75% by mass or more, even more preferably 80% by mass or more, and is preferably 98% by mass or less, more preferably 96% by mass or less, even more preferably 95% by mass or less, based on 100% by mass of the asphalt composition.

[Thermoplastic elastomer]
From the viewpoint of improving rut resistance, the asphalt composition preferably contains a thermoplastic elastomer. The asphalt and the thermoplastic elastomer are preferably used as a binder mixture, which is a mixture of these. Examples of the binder mixture include straight asphalt (modified asphalt) modified with a thermoplastic elastomer.

Examples of the thermoplastic elastomer include at least one selected from the group consisting of styrene/butadiene block copolymers (hereinafter, also referred to simply as "SB"), styrene/butadiene/styrene block copolymers (hereinafter, also referred to simply as "SBS"), styrene/butadiene random copolymers (hereinafter, also referred to simply as "SBR"), styrene/isoprene block copolymers (hereinafter, also referred to simply as "SI"), styrene/isoprene/styrene block copolymers (hereinafter, also referred to simply as "SIS"), styrene/isoprene random copolymers (hereinafter, also referred to simply as "SIR"), ethylene/vinyl acetate copolymers, and ethylene/acrylic acid ester copolymers.
An example of a commercially available ethylene/acrylic acid ester copolymer is "Elvaroy" (manufactured by DuPont).

Among these thermoplastic elastomers, from the viewpoint of further improving rut resistance, at least one selected from the group consisting of styrene/butadiene block copolymers, styrene/butadiene/styrene block copolymers, styrene/butadiene random copolymers, styrene/isoprene block copolymers, styrene/isoprene/styrene block copolymers, and styrene/isoprene random copolymers is preferred, and at least one selected from the group consisting of styrene/butadiene random copolymers and styrene/butadiene/styrene block copolymers is more preferred.

From the viewpoint of further improving rut resistance, the content of the thermoplastic elastomer in the asphalt composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, even more preferably 2% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, even more preferably 5% by mass or less, based on 100% by mass of the asphalt composition.

In the asphalt composition, the ratio of the thermoplastic elastomer is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, per 100 parts by mass of asphalt, from the viewpoint of further improving rut resistance.

〔polyester〕
The asphalt composition of the present invention contains a polyester containing a structural unit derived from an alcohol component and a structural unit derived from a carboxylic acid component. From the viewpoint of further improving the rut resistance of the pavement surface after construction, the polyester contains a structural unit derived from a carboxylic acid component containing at least one selected from an alkyl succinic acid and an alkenyl succinic acid. The polyester can be used alone or in combination of two or more kinds.

<Alcohol content>
Examples of the alcohol component include diols and polyhydric alcohols having a valence of 3 to 8. Examples of the diol include aliphatic diols and aromatic diols. These alcohol components can be used alone or in combination of two or more.

The aliphatic diol is, for example, an aliphatic diol having from 2 to 20 carbon atoms. Examples of the aliphatic diol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-butenediol, 1,3-butanediol, neopentyl glycol, 1,10-decanediol, and 1,12-dodecanediol.
The polyhydric alcohol having a valence of three or more is, for example, a trihydric alcohol. An example of the polyhydric alcohol having a valence of three or more is glycerin.

From the viewpoint of further improving the rut resistance of the pavement surface after construction, the alcohol component preferably contains an alkylene oxide adduct of bisphenol A, and more preferably contains an alkylene oxide adduct of bisphenol A represented by formula (I).

[In the formula, ^OR1 and ^R1O are alkylene oxides, ^R1 is an alkylene group having 2 or 3 carbon atoms, x and y are positive numbers indicating the average number of moles of alkylene oxide added, and the sum of x and y is preferably 1 or more, more preferably 1.5 or more, and is preferably 16 or less, more preferably 8 or less, and even more preferably 4 or less.]

Examples of alkylene oxide adducts of bisphenol A represented by formula (I) include a propylene oxide adduct of bisphenol A [2,2-bis(4-hydroxyphenyl)propane] 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.

From the viewpoint of improving melt dispersion in asphalt and obtaining excellent rut resistance, the amount of alkylene oxide adduct of bisphenol A in the alcohol component is preferably 60 mol% or more, more preferably 65 mol% or more, and even more preferably 80 mol% or more, and 100 mol% or less, out of 100 mol% of the alcohol component. When the asphalt is asphalt modified with a thermoplastic elastomer, polyesters containing structural units derived from the alcohol component containing 60 mol% or more of alkylene oxide adduct of bisphenol A can further improve the rut resistance of the pavement surface after construction, and are therefore preferred. Among thermoplastic elastomers, the aforementioned SBS and SBR are particularly likely to exhibit this effect.

The molar ratio of propylene oxide adduct of bisphenol A to ethylene oxide adduct of bisphenol A in the alcohol component is preferably 5/95 or more, more preferably 10/90 or more, even more preferably 15/85 or more, even more preferably 20/80 or more, and from the viewpoint of further improving melt dispersibility in asphalt and obtaining excellent rut resistance, it is preferably 90/10 or less, more preferably 60/40 or less, even more preferably 40/60 or less, even more preferably 30/70 or less.

<Carboxylic Acid Component>
From the viewpoint of further improving the rut resistance of the pavement surface after construction, the carboxylic acid component contains at least one selected from alkylsuccinic acid and alkenylsuccinic acid, and preferably contains alkenylsuccinic acid.

From the viewpoint of further improving the rut resistance of the pavement surface after construction, the number of carbon atoms in the alkyl group and alkenyl group in the alkylsuccinic acid and alkenylsuccinic acid is preferably 9 or more, more preferably 10 or more, and is preferably 18 or less, more preferably 14 or less, and even more preferably 12 or less.
The alkyl and alkenyl groups may be linear or branched, but are preferably branched from the viewpoint of further improving the rut resistance of the pavement surface after construction. The branched structure may be present in any part of the alkyl and alkenyl groups.
Therefore, the polyester preferably contains constitutional units derived from a branched alkenyl succinic acid.
From the viewpoint of further improving the rut resistance of the pavement surface after construction, it is preferable that the alkyl succinic acid and the alkenyl succinic acid are each a mixture containing two or more types. The "type" here refers to an alkyl or alkenyl group, and those having different chain lengths of the carbon number of the alkyl or alkenyl group or structural isomers are treated as different types of alkyl succinic acid or alkenyl succinic acid.

Therefore, from the viewpoint of further improving the rut resistance of the pavement surface after construction, it is preferable that the alkyl succinic acid is a mixture containing two or more kinds of alkyl succinic acid having a branched chain alkyl group with a carbon number of preferably 9 or more, more preferably 10 or more, and preferably 18 or less, more preferably 14 or less, and even more preferably 12 or less. Also, from the viewpoint of further improving the rut resistance of the pavement surface after construction, it is preferable that the alkenyl succinic acid is a mixture containing two or more kinds of alkenyl succinic acid having a branched chain alkenyl group with a carbon number of preferably 9 or more, more preferably 10 or more, and preferably 18 or less, more preferably 14 or less, and even more preferably 12 or less.

The alkylsuccinic acid and alkenylsuccinic acid are preferably obtained from a compound having an alkylene group (alkylene compound) and at least one selected from maleic acid, fumaric acid, and their acid anhydrides.

The alkylene compound is a compound having a carbon number of preferably 9 or more, more preferably 10 or more, and preferably 18 or less, more preferably 14 or less, and even more preferably 12 or less. Specifically, compounds obtained from ethylene, propylene, isobutylene, normal butylene, etc., such as trimers and tetramers thereof, are preferably used. As a suitable raw material used in the synthesis of alkylene compounds, propylene having a small molecular weight is preferable from the viewpoint of increasing the number of structural isomers.

Alkyl succinic acid and alkenyl succinic acid can be obtained by any manufacturing method, for example, by mixing an alkylene compound with at least one selected from maleic acid, fumaric acid, and their acid anhydrides, heating, and utilizing the ene reaction (see JP-A-48-23405, JP-A-48-23404, U.S. Pat. No. 3,374,285, etc.). Among maleic acid, fumaric acid, and their acid anhydrides, maleic anhydride is preferred from the viewpoint of reactivity. Suitable catalysts used in the synthesis of alkylene compounds include liquid phosphoric acid, solid phosphoric acid, tungsten, boron trifluoride complex, etc. Note that, from the viewpoint of facilitating control of the number of structural isomers and improving rut resistance, a method of adjusting by distillation after random polymerization is preferred.

The total amount of alkylsuccinic acid and alkenylsuccinic acid in the carboxylic acid component is, from the viewpoint of improving melt dispersibility in asphalt and obtaining excellent rut resistance, preferably 3 mol% or more, more preferably 8 mol% or more, even more preferably 15 mol% or more, and preferably 50 mol% or less, more preferably 40 mol% or less, even more preferably 30 mol% or less, out of 100 mol% of the carboxylic acid component.

Acid components that can be used other than alkylsuccinic acid and alkenylsuccinic acid include aliphatic dicarboxylic acids other than alkylsuccinic acid and alkenylsuccinic acid, aromatic dicarboxylic acids, and polyvalent carboxylic acids having three or more carboxylic acids. These carboxylic acid components can be used alone or in combination of two or more kinds.

From the viewpoint of further improving the rut resistance of the pavement surface after construction, the number of carbon atoms in the main chain of the aliphatic dicarboxylic acid is preferably 3 or more, more preferably 4 or more, and is preferably 10 or less, more preferably 8 or less.
Examples of the aliphatic dicarboxylic acid include fumaric acid, maleic acid, oxalic acid, malonic acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid. Among them, at least one selected from the group consisting of fumaric acid, maleic acid, and adipic acid is preferred, and adipic acid is more preferred.

Examples of aromatic dicarboxylic acids include phthalic acid, isophthalic acid, and terephthalic acid. From the viewpoint of further improving the rut resistance of the pavement surface after construction, isophthalic acid and terephthalic acid are preferred, and terephthalic acid is more preferred.

Examples of trivalent or higher polyvalent carboxylic acids include trimellitic acid, 2,5,7-naphthalenetricarboxylic acid, and pyromellitic acid.

From the viewpoint of further improving the rut resistance of the pavement surface after construction, the content of aromatic dicarboxylic acid in the carboxylic acid component is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, and preferably 97 mol% or less, more preferably 92 mol% or less, even more preferably 85 mol% or less, out of 100 mol% of the carboxylic acid component.

(Molar ratio of structural units derived from carboxylic acid component to structural units derived from alcohol component)
The molar ratio of the constituent units derived from the carboxylic acid component to the constituent units derived from the alcohol component [carboxylic acid component/alcohol component] is, from the viewpoint of adjusting the acid value and improving the rut resistance, preferably 0.7 or more, more preferably 0.8 or more, and is preferably 1.5 or less, more preferably 1.3 or less, and even more preferably 1.1 or less.

The polyester of the present invention may be a polyester that has been modified to such an extent that its properties are not substantially impaired. Specific examples of modified polyesters include polyesters that have been grafted or blocked with phenol, urethane, epoxy, or the like, by methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, and the like. Preferred modified polyesters include urethane-modified polyesters in which polyesters have been urethane-extended with a polyisocyanate compound.

(Physical properties of polyester)
From the viewpoint of obtaining rut resistance, the softening point of the polyester is preferably 90° C. or higher, more preferably 95° C. or higher, even more preferably 100° C. or higher, and is preferably 140° C. or lower, more preferably 130° C. or lower, even more preferably 125° C. or lower, even more preferably 120° C. or lower, even more preferably 115° C. or lower.

The acid value of the polyester is preferably 1 mgKOH/g or more, more preferably 3 mgKOH/g or more, and even more preferably 5 mgKOH/g or more, from the viewpoint of promoting the adsorption of the polyester to the aggregate and further improving rut resistance, and is preferably 60 mgKOH/g or less, more preferably 40 mgKOH/g or less, and even more preferably 30 mgKOH/g or less, from the viewpoint of improving the water resistance of the pavement surface.

From the viewpoint of further improving rut resistance, the hydroxyl value of the polyester is preferably 1 mgKOH/g or more, more preferably 2 mgKOH/g or more, even more preferably 5 mgKOH/g or more, and preferably 33 mgKOH/g or less, more preferably 30 mgKOH/g or less, even more preferably 25 mgKOH/g or less, even more preferably 20 mgKOH/g or less.

From the viewpoint of obtaining rut resistance, the glass transition point of the polyester is preferably 30°C or higher, more preferably 40°C or higher, even more preferably 50°C or higher, even more preferably 53°C or higher, and preferably 80°C or lower, more preferably 70°C or lower, even more preferably 65°C or lower, even more preferably 60°C or lower.

The softening point, acid value, hydroxyl value, and glass transition point can be measured by the method described in the Examples. The softening point, acid value, hydroxyl value, and glass transition point can be adjusted by the raw material monomer composition, molecular weight, catalyst amount, or reaction conditions.

(Production method of polyester)
The method for producing the polyester is not particularly limited, but the polyester can be produced, for example, by polycondensing the above-mentioned alcohol component and carboxylic acid component.
The temperature of the polycondensation reaction is not particularly limited, but is preferably 160° C. or higher and 260° C. or lower from the viewpoint of controlling the reactivity and monomer decomposition temperature and improving the rut resistance.

In the polycondensation reaction, from the viewpoint of controlling the reactivity to improve rut resistance and from the viewpoint of cost, a tin (II) compound not having a Sn—C bond, such as tin (II) di(2-ethylhexanoate), may be used as a catalyst in an amount of preferably 0.01 part by mass or more, more preferably 0.2 part by mass or more, and preferably 1.5 parts by mass or less, more preferably 0.6 parts by mass or less, per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.
In the polycondensation reaction, from the viewpoint of controlling the reactivity to improve rut resistance and from the viewpoint of costs, in addition to the catalyst, a pyrogallol compound such as gallic acid may be used as a co-catalyst in an amount of preferably 0.001 part by mass or more, more preferably 0.005 part by mass or more, even more preferably 0.01 part by mass or more, and preferably 0.15 part by mass or less, more preferably 0.10 part by mass or less, and even more preferably 0.05 part by mass or less, per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

(Polyester content)
From the standpoint of achieving both cost and rut resistance, the content of polyester in the asphalt composition is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of asphalt.

[Dispersant]
The asphalt composition may include a dispersant.
The dispersant is preferably one which dissolves in asphalt and has affinity with polyester.
Examples of the dispersant include polymer dispersants, and surfactants such as polyoxyethylene alkylamines and alkanolamines.
Examples of polymer dispersants include polyamidoamines and their salts, polycarboxylic acids and their salts, high molecular weight unsaturated acid esters, modified polyurethanes, modified polyesters, modified poly(meth)acrylates, (meth)acrylic copolymers, naphthalenesulfonic acid-formalin condensates, etc. These dispersants may be used alone or in combination of two or more.
The dispersant is preferably a polymer dispersant from the viewpoint of improving high-temperature storage stability and rut resistance. In the present invention, the "polymer dispersant" means a dispersant having a weight-average molecular weight of 1,000 or more. Although it depends on the type of polymer, the weight-average molecular weight is preferably 2,000 or more, more preferably 4,000 or more, and preferably 80,000 or less, more preferably 40,000 or less.

From the viewpoint of improving rut resistance, the dispersant preferably has a basic functional group. The basic functional group means a group whose conjugate acid has a pKa of -3 or more. Examples of the basic functional group include an amino group, an imino group, and a quaternary ammonium group.
From the viewpoint of improving high-temperature storage stability and rut resistance, the base number of the dispersant is preferably 10 mgKOH/g or more, more preferably 20 mgKOH/g or more, even more preferably 30 mgKOH/g or more, and is preferably 150 mgKOH/g or less, more preferably 120 mgKOH/g or less, even more preferably 100 mgKOH/g or less. The base number is measured by the method specified in JIS K7237:1995.

Commercially available dispersants include, for example, the "Disper" series of "byk-101", "byk-130", "byk-161", "byk-162", "byk-170", "byk-2020", "byk-2164", and "byk-LPN21324" (all manufactured by BYK); the "Solsperse" series of "9000", "11200", "13240", "13650", "13940", "17000", "18000", "24000", "28000", "32000", 38500, 71000 (all manufactured by Lubrizol); Ajisper series PB821, PB822, PB880, PB881 (all manufactured by Ajinomoto Fine-Techno Co., Ltd.); Efka series 46, 47, 48, 49, 4010, 4047, 4050, 4165, 5010 (all manufactured by BASF); FLOWLEN TG-710 (manufactured by Kyoeisha Chemical Co., Ltd.); and TAMN-15 (manufactured by Nikko Chemicals Co., Ltd.).

From the viewpoint of improving rut resistance, the content of the dispersant is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 4 parts by mass or more, per 100 parts by mass of polyester, and is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less.

[Asphalt mixture]
The asphalt mixture according to the embodiment of the present invention contains the asphalt composition described above and aggregate. That is, the asphalt mixture contains asphalt, polyester, and aggregate, and preferably contains asphalt, thermoplastic elastomer, polyester, and aggregate. Furthermore, the pavement according to the embodiment of the present invention is paved with the asphalt mixture.
From the viewpoint of further improving rut resistance, the content of the asphalt composition in the asphalt mixture is preferably 2 mass% or more, more preferably 3 mass% or more, even more preferably 4 mass% or more, and preferably 15 mass% or less, more preferably 10 mass% or less, even more preferably 8 mass% or less, based on 100 mass% of the asphalt mixture.

〔aggregate〕
The aggregate may be any material selected from crushed stone, boulders, gravel, sand, recycled aggregate, ceramics, etc. In addition, the aggregate may be either coarse aggregate with a particle size of 2.36 mm or more, or fine aggregate with a particle size of less than 2.36 mm.
Examples of coarse aggregate include crushed stone with a particle size range of 2.36 mm to 4.75 mm, crushed stone with a particle size range of 4.75 mm to 12.5 mm, crushed stone with a particle size range of 12.5 mm to 19 mm, and crushed stone with a particle size range of 19 mm to 31.5 mm.
The fine aggregate preferably has a particle size of 0.075 mm or more and less than 2.36 mm. Examples of fine aggregate include river sand, dune sand, mountain sand, sea sand, crushed sand, fine sand, screenings, crushed stone dust, silica sand, artificial sand, glass cullet, foundry sand, and recycled crushed aggregate sand.
The above particle size is a value specified in JIS A5001:1995.
Among these, a combination of coarse aggregate and fine aggregate is preferable.

The fine aggregate may contain a filler (e.g., sand) with a particle size of less than 0.075 mm. Examples of fillers include sand, fly ash, calcium carbonate, and hydrated lime. Of these, calcium carbonate is preferred from the viewpoint of improving dry strength and rut resistance.

From the viewpoint of improving dry strength and rut resistance, 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, and even more preferably 0.02 mm or less. The average particle size of the filler can be measured with a laser diffraction particle size distribution measuring device. Here, the average particle size means the average particle size at 50% cumulative volume.

(Method of measuring average particle size of filler)
The average particle size of the filler is a value measured using a laser diffraction particle size distribution measuring device "LA-950" (manufactured by Horiba, Ltd.) under the conditions shown below.
Measurement method: flow method Dispersion medium: ethanol Sample preparation: 2 mg/100 mL
Dispersion method: Stirring, built-in ultrasonic for 1 minute

From the viewpoint of further improving rut resistance, the mass ratio of coarse aggregate to fine aggregate is preferably 10/90 or more, more preferably 20/80 or more, even more preferably 30/70 or more, and is preferably 90/10 or less, more preferably 80/20 or less, even more preferably 70/30 or less.

From the viewpoint of further improving rut resistance, the aggregate content is preferably 1,000 parts by mass or more, more preferably 1,200 parts by mass or more, and even more preferably 1,400 parts by mass or more, per 100 parts by mass of the total of asphalt, thermoplastic elastomer, and polyester, and is preferably 3,000 parts by mass or less, more preferably 2,500 parts by mass or less, and even more preferably 2,000 parts by mass or less.

A suitable example of the blend for the asphalt mixture is as follows:
(1) An example asphalt mixture includes, for example, 30% to less than 45% by volume of coarse aggregate, 30% to 50% by volume of fine aggregate, and 5% to 10% by volume of an asphalt composition (fine-grained asphalt).
(2) An example asphalt mixture includes, for example, 45% to less than 70% by volume of coarse aggregate, 20% to 45% by volume of fine aggregate, and 3% to 10% by volume of an asphalt composition (dense-graded asphalt).
(3) An example of an asphalt mixture includes, for example, 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 (porous asphalt).

The asphalt mixture may further contain other components as required.
The proportion of asphalt in conventional asphalt mixtures containing aggregate and asphalt is usually determined based on the optimal amount of asphalt obtained from the "Mix Design of Asphalt Composition" described in the "Guidelines for Pavement Design and Construction" issued by the Japan Road Association.
In the present invention, the above-mentioned optimum asphalt amount corresponds to the total amount of asphalt, thermoplastic elastomer and polyester. Therefore, it is usually preferable that the optimum asphalt amount is the total amount of asphalt, thermoplastic elastomer and polyester.
However, it is not necessary to be limited to the method described in the "Guidelines for Pavement Design and Construction" and other methods may be used to determine the method.

[Method of manufacturing asphalt mixture]
The method for producing the asphalt mixture of the present invention is not particularly limited, but from the viewpoint of improving rut resistance, a method including a step of mixing heated aggregate, asphalt, and the above-mentioned polyester is preferred, and a method including a step of mixing heated aggregate, asphalt, a thermoplastic elastomer, and the above-mentioned polyester is more preferred.

Specific methods for producing asphalt mixtures include conventional methods for producing asphalt mixtures called the plant mix method and the premix method. All of these methods involve adding asphalt (and thermoplastic elastomer, if necessary) and polyester to heated aggregate. Examples of the addition method include the premix method in which asphalt (and thermoplastic elastomer, if necessary) and polyester are dissolved in advance, or the plant mix method in which modified asphalt in which thermoplastic elastomer is dissolved in asphalt is added, and then polyester is added. Among these, the premix method is preferred from the viewpoint of rut resistance.
More specifically, in the method for producing an asphalt mixture, in the mixing step, preferably,
(i) adding and mixing asphalt (and optionally thermoplastic elastomer) to the heated aggregate, followed by adding and mixing polyester;
(ii) Adding and mixing the asphalt (and optionally a thermoplastic elastomer) and polyester simultaneously to the heated aggregate, or (iii) Adding and mixing a pre-heated mixture of the asphalt (and optionally a thermoplastic elastomer) and polyester to the heated aggregate.
Among these, method (iii) is preferred from the viewpoint of rut resistance.

In the method (iii), the mixing temperature when the asphalt and polyester are mixed in advance is preferably a temperature higher than the softening point of the polyester from the viewpoint of rut resistance, and is preferably 130°C or higher, more preferably 150°C or higher, even more preferably 170°C or higher, and even more preferably 180°C or higher. From the viewpoint of preventing thermal deterioration of the asphalt, the mixing temperature is preferably 230°C or lower, more preferably 210°C or lower, and even more preferably 200°C or lower. From the viewpoint of improving rut resistance, the mixing time is, for example, 10 minutes or more, preferably 30 minutes or more, more preferably 1 hour or more, and even more preferably 2 hours or more. The upper limit of the time is not particularly limited, but is, for example, about 5 hours.

The temperature of the heated aggregate in methods (i) to (iii) is preferably higher than the softening point of the polyester from the viewpoint of rut resistance, and is preferably 130°C or higher, more preferably 150°C or higher, even more preferably 170°C or higher, and even more preferably 180°C or higher, and from the viewpoint of preventing thermal degradation of the asphalt, is preferably 230°C or lower, more preferably 210°C or lower, and even more preferably 200°C or lower.

In the mixing process, from the viewpoint of improving rut resistance, the mixing temperature is preferably higher than the softening point of the polyester, and is preferably 130°C or higher, more preferably 150°C or higher, even more preferably 170°C or higher, and even more preferably 180°C or higher. From the viewpoint of preventing thermal deterioration of the asphalt and improving rut resistance, the mixing temperature is preferably 230°C or lower, more preferably 210°C or lower, and even more preferably 200°C or lower. The mixing time in the mixing process is, for example, 30 seconds or more, preferably 1 minute or more, more preferably 2 minutes or more, and even more preferably 5 minutes or more. The upper limit of the time is not particularly limited, but is, for example, about 30 minutes.

From the viewpoint of further improving rut resistance, the method for producing an asphalt mixture preferably includes, after the mixing step, a step of holding the resulting mixture at a temperature higher than the softening point of the polyester or higher.
In the holding step, the mixture may be further mixed, but it is sufficient that the mixture is held at the aforementioned temperature or higher.
In the holding step, the mixing temperature is preferably higher than the softening point of the polyester, and is preferably 130° C. or higher, more preferably 150° C. or higher, even more preferably 170° C. or higher, and even more preferably 180° C. or higher, and from the viewpoint of preventing thermal deterioration of the asphalt composition, is preferably 230° C. or lower, more preferably 210° C. or lower, and even more preferably 200° C. or lower. The holding time in the holding step is preferably 0.5 hours or longer, more preferably 1 hour or longer, and even more preferably 1.5 hours or longer, and the upper limit of the time is not particularly limited, but is, for example, about 5 hours.

[Road paving method]
The asphalt mixture is used for road paving.
The road paving method preferably includes a step of applying the asphalt mixture to a road to form an asphalt pavement layer. Specifically, the road paving method preferably includes a step (step 1) of obtaining an asphalt mixture by mixing asphalt, the polyester, and heated aggregate, and a step (step 2) of applying the asphalt mixture obtained in step 1 to a road to form an asphalt pavement layer. The asphalt pavement layer is preferably a base layer or a surface layer.

The asphalt mixture may be compacted and applied in a similar manner using known construction machinery. From the viewpoint of rut resistance, the compaction temperature when used as a heated asphalt mixture is preferably higher than the softening point of polyester, preferably 100°C or higher, more preferably 120°C or higher, even more preferably 130°C or higher, and preferably 200°C or lower, more preferably 180°C or lower.

The physical properties of the resin and the like were measured and evaluated by the following methods.
[Measurement method]
[Acid value and hydroxyl value of polyester]
The acid value and hydroxyl value of the polyester were measured according to the method of JIS K0070: 1992. However, the measurement solvent was changed from the mixed solvent of ethanol and ether specified in JIS K0070: 1992 to a mixed solvent of acetone and toluene (acetone:toluene=1:1 (volume ratio)).

[Softening point and glass transition point of polyester]
(1) Softening point Using a flow tester "CFT-500D" (manufactured by Shimadzu Corporation), 1 g of a sample was extruded from a nozzle having a diameter of 1 mm and a length of 1 mm under a load of 1.96 MPa applied by a plunger while heating the sample at a temperature increase rate of 6°C/min. The plunger descent 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.
(2) Glass transition point Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan Co., Ltd.), 0.01 to 0.02 g of a sample was weighed into an aluminum pan, heated to 200°C, and cooled from that temperature to 0°C at a rate of 10°C/min. Next, measurements were taken while heating to 150°C at a rate of 10°C/min. The glass transition point was determined as the temperature at the intersection of an extension of the baseline below the maximum endothermic peak temperature and a tangent line showing the maximum slope from the rising part of the peak to the apex of the peak.

Manufacturing Example A
[Production of branched alkenyl succinic anhydride]
(1) Production of alkene mixture (a) An alkene mixture (a) was obtained by fractional distillation using a propylene tetramer "Light Tetramer" (manufactured by JXTG Nippon Oil & Energy Corporation) under heating conditions of 183 to 208° C. The obtained alkene mixture (a) had 40 peaks in gas chromatography mass spectrometry.
The distribution of the alkene mixture was measured _according to the analysis by gas chromatography/mass spectrometry of alkylene compound A described in JP 2014-013384 A. The results were: _C9H18 : 0.5% by mass, _{C10H20 : 4% by mass, C11H22: 20% by mass, C12H24 : 66} % _by mass, _C13H26 : ₉ % by mass, _{C14H28 :} 0.5% _by mass (6 peaks corresponding to alkenes having 9 to 14 carbon atoms).

(2) Production of branched alkenyl succinic anhydride Into a 1L autoclave (manufactured by Nitto Koatsu Co., Ltd.), 542.4 g of alkene mixture (a), 157.2 g of maleic anhydride, 0.4 g of antioxidant "Chelex-O" (manufactured by SC Organic Chemical Co., Ltd., triisooctyl phosphite), and 0.1 g of butyl hydroquinone as a polymerization inhibitor were charged, and pressurized nitrogen replacement (0.2 MPaG) was repeated three times. After stirring was started at 60°C, the temperature was raised to 230°C over 1 hour and the reaction was carried out for 6 hours. The pressure when the reaction temperature was reached was 0.3 MPaG. After the reaction was completed, the mixture was cooled to 80°C, returned to normal pressure (101.3 kPa), and transferred to a 1L four-neck flask. The temperature was raised to 180°C with stirring, and the remaining alkylene compound was distilled off at 1.3 kPa for 1 hour. The mixture was cooled to room temperature (25° C.) and then returned to normal pressure (101.3 kPa) to obtain 406.1 g of the target branched alkenyl succinic anhydride. The average molecular weight of the branched alkenyl succinic anhydride calculated from the acid value was 256.

Production Examples 1 to 8
(Production of Polyester Resins (A1) to (A8))
The polyester alcohol components and terephthalic acid shown in Tables 1 and 2 were placed in a 5-liter four-neck flask equipped with a thermometer, a stainless steel stirring rod, a downflow condenser, and a nitrogen inlet tube, and 20 g of tin(II) di(2-ethylhexanoate) and 2 g of gallic acid were added in a nitrogen atmosphere, and the mixture was heated to 235° C. over 3 hours in a mantle heater, maintained at 235° C. for 5 hours after reaching 235° C., and then cooled to 180° C. After cooling to 180° C., the branched alkenyl succinic anhydride obtained in Production Example A above or the linear alkenyl succinic anhydride described below was added, the mixture was heated to 210° C. over 2 hours, maintained at 210° C. for 1 hour, and reacted under reduced pressure at 8.0 kPa, and then reacted until the softening points shown in Tables 1 and 2 were reached, to obtain the target polyester resins (A1) to (A8).
As the linear alkenyl succinic anhydride, dodecenyl succinic anhydride (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., molecular weight = 266) was used.

Production Example 9
(Production of Polyester Resin (B1))
The polyester alcohol components and terephthalic acid shown in Table 2 were placed in a 5-liter four-neck flask equipped with a thermometer, a stainless steel stirring rod, a downflow condenser, and a nitrogen inlet tube, and 20 g of tin(II) di(2-ethylhexanoate) and 2 g of gallic acid were added in a nitrogen atmosphere. The temperature was raised to 235°C over 3 hours in a mantle heater, and the mixture was maintained for 5 hours after reaching 235°C, and then a reaction was carried out under reduced pressure at 8.0 kPa. The reaction was continued until the softening point shown in Table 2 was reached, thereby obtaining the target polyester resin (B1).

Example 1
As a binder mixture, 2200 g of modified asphalt containing 3 mass% SBS (manufactured by Texas Ergon, asphalt concentration in asphalt: 24 mass%) heated to 180°C was placed in a 3 L stainless steel container and stirred at 100 rpm, and 66 g of polyester resin (A1) (3 parts by mass per 100 parts by mass of asphalt) was gradually added and stirred at 300 rpm for 2 hours to prepare an asphalt composition (AS-1).

Next, 11 kg of aggregate heated to 180° C. (see below for the composition of the aggregate) was placed in an asphalt mixer and mixed at 180° C. for 60 seconds.
Next, 621 g of the asphalt composition (AS-1) was added and mixed for 2 minutes with an asphalt mixer. The resulting asphalt mixture was stored at 180°C for 2 hours, then filled into a 300 x 300 x 50 cm formwork and subjected to 25 rotations of pressure treatment at 150°C and a load of 0.44 kPa using a roller compactor (manufactured by Iwata Kogyosho Co., Ltd.) to prepare a test specimen.

<Composition of aggregate>
No. 6 crushed stone 50.9 parts by mass Crushed sand 1 10.4 parts by mass Crushed sand 2 22.1 parts by mass Fine sand 10.4 parts by mass Stone powder 6.2 parts by mass Passed mass%:
Sieve size 15 mm: 100% by mass
Sieve size 10 mm: 85.6% by mass
Sieve size 5 mm: 49.7% by mass
Sieve size 2.5 mm: 44.6% by mass
Sieve size 1.2 mm: 31.6% by mass
Sieve size 0.6 mm: 21.3% by mass
Sieve size 0.3 mm: 12.7% by mass
Sieve size 0.15 mm: 7.1% by mass

Examples 2 to 8
Asphalt compositions (AS-2) to (AS-8) were prepared in the same manner as in Example 1, except that the polyester resin (A1) in Example 1 was changed to the polyester resins (A2) to (A8), respectively.
Test specimens were obtained in the same manner as in Example 1, except that the asphalt composition (AS-1) in Example 1 was changed to the asphalt compositions (AS-2) to (AS-8), respectively.

Example 9
An asphalt composition (AS-9) was obtained in the same manner as in Example 1, except that the amount of polyester resin (A1) added was changed to 176 g (8 parts by mass per 100 parts by mass of asphalt).
A specimen was obtained in the same manner as in Example 1, except that 621 g of the asphalt composition (AS-1) was changed to 652 g of the asphalt composition (AS-9).

Example 10
An asphalt composition (AS-10) was obtained in the same manner as in Example 1, except that the amount of polyester resin (A1) added was changed to 330 g (15 parts by mass per 100 parts by mass of asphalt).
A specimen was obtained in the same manner as in Example 1, except that 621 g of the asphalt composition (AS-1) was changed to 694 g of the asphalt composition (AS-10).

Comparative Example 1
An asphalt composition (AS-C1) was prepared in the same manner as in Example 1, except that the polyester resin (A1) in Example 1 was changed to the polyester resin (B1).
A specimen was obtained in the same manner as in Example 1, except that the asphalt composition (AS-1) in Example 1 was changed to the asphalt composition (AS-C1).

Comparative Example 2
An asphalt composition (AS-C2) was prepared in the same manner as in Example 1, except that the polyester resin (A1) was not added.
A specimen was obtained in the same manner as in Example 1, except that 621 g of the asphalt composition (AS-1) was changed to 603 g of the asphalt composition (AS-C2).

Example 11
As a binder mixture, 2200 g of modified asphalt containing 3% by mass of SBS (manufactured by Toa Road Industrial Co., Ltd., Japan, asphaltene concentration in asphalt: 15% by mass) heated to 180°C was placed in a 3 L stainless steel container and stirred at 100 rpm, and 440 g of polyester resin (A1) (20 parts by mass per 100 parts by mass of asphalt) was gradually added and stirred at 300 rpm for 2 hours to prepare an asphalt composition (AS-11).
A test specimen was obtained in the same manner as in Example 1, except that 621 g of the asphalt composition (AS-1) was changed to 724 g of the asphalt composition (AS-11).

Comparative Example 3
An asphalt composition (AS-C3) was prepared in the same manner as in Example 11, except that the polyester resin (A1) in Example 11 was changed to the polyester resin (B1).
A specimen was obtained in the same manner as in Example 1, except that 621 g of the asphalt composition (AS-1) was changed to 724 g of the asphalt composition (AS-C3).

Comparative Example 4
An asphalt composition (AS-C4) was prepared in the same manner as in Example 11, except that the polyester resin (A1) was not added.
A specimen was obtained in the same manner as in Example 1, except that 621 g of the asphalt composition (AS-1) was changed to 603 g of the asphalt composition (AS-C4).

Example 12
As a binder mixture, 2,200 g of straight asphalt (manufactured by Showa Shell Sekiyu K.K., asphaltene concentration in asphalt: 16% by mass) heated to 180°C was placed in a 3 L stainless steel container and stirred at 100 rpm, and 66 g of polyester resin (A1) (3 parts by mass per 100 parts by mass of asphalt) was gradually added and stirred at 300 rpm for 2 hours to prepare an asphalt composition (AS-12).
A specimen was obtained in the same manner as in Example 1, except that the asphalt composition (AS-1) in Example 1 was changed to the asphalt composition (AS-12).

Comparative Example 5
An asphalt composition (AS-C5) was prepared in the same manner as in Example 12, except that the polyester resin (A1) in Example 12 was changed to the polyester resin (B1).
A specimen was obtained in the same manner as in Example 1, except that the asphalt composition (AS-1) in Example 1 was changed to the asphalt composition (AS-C5).

Comparative Example 6
An asphalt composition (AS-C6) was prepared in the same manner as in Example 12, except that the polyester resin (A1) was not added.
A specimen was obtained in the same manner as in Example 1, except that the asphalt composition (AS-1) in Example 1 was changed to the asphalt composition (AS-C6).

[evaluation]
[Rut resistance]
(Examples 1 to 11 and Comparative Examples 1 to 4)
The specimen was immersed in hot water set at 60°C in a 60°C thermostatic chamber, and a wheel tracking tester (manufactured by Iwata Kogyosho Co., Ltd., load 1370N, iron wheel width 47mm, linear pressure 291.5N/cm) was used to move the wheel back and forth over the specimen at a speed of 15 times/min, and the amount of displacement after 2,500 passes was measured. Other measurement conditions were in accordance with the "B003 Wheel Tracking Test" described in the "Pavement Survey and Testing Method Handbook" published by the Japan Road Association.
(Example 12 and Comparative Examples 5 to 6)
The test specimen was immersed in hot water set at 50° C. in a thermostatic chamber at 50° C., and the amount of displacement was measured after the tire had passed over the test specimen 2,500 times in the same manner as above.
The results are shown in Tables 3 to 5.

[Peeling resistance]
(Examples 1 to 11 and Comparative Examples 1 to 4)
Glass marbles (diameter 17 mm) manufactured by Artec Co., Ltd. were used as aggregates. The marbles were dried for about 1 hour in a hot air dryer set at 180°C. The asphalt composition heated to 180°C was added to the dried marbles and stirred and mixed with a metal spatula for about 1 minute to completely cover the surface of the aggregates with the asphalt composition. The ratio of the asphalt composition to 100 g of marbles was 5.5±0.2 g. The obtained asphalt-coated sample was left to stand in a 180°C thermostatic chamber for 45 minutes and then cooled to room temperature. The asphalt-coated sample was spread on a mesh with 1 mm openings and immersed in a 1.0 mol/L sodium carbonate aqueous solution (pH 11.0) at 85°C for 3 minutes. After immersion, the proportion of the area of the part where the asphalt composition was not peeled off was measured.
(Example 12 and Comparative Examples 5 to 6)
The measurement was carried out in the same manner as above, except that the temperature of the aqueous sodium carbonate solution was changed to 70°C.
The results are shown in Tables 3 to 5.

Comparisons between Examples 1 to 10 and Comparative Examples 1 and 2, between Example 11 and Comparative Examples 3 and 4, and between Example 12 and Comparative Examples 5 and 6 show that the inclusion of a specific polyester in an asphalt composition improves the durability of the pavement surface after construction and suppresses rutting. It is also clear that the higher the polyester content in the asphalt composition, the better the durability of the pavement surface after construction and the more rutting can be suppressed.
Furthermore, in Comparative Examples 1 to 6, the residual area of the asphalt composition on the marble surface after immersion in the sodium carbonate aqueous solution was low at 10 to 20%, whereas it was very high at 60 to 91% in Examples 1 to 12. Therefore, it is clear that the asphalt composition of the present invention can maintain a strong aggregate interface even under alkaline conditions, and as a result, the pavement surface after construction is excellent in durability and rutting can be suppressed.

Claims (11)

An asphalt composition comprising asphalt and a polyester,
the polyester contains a structural unit derived from an alcohol component and a structural unit derived from a carboxylic acid component,
The structural unit derived from an alcohol component includes a structural unit derived from an alcohol component containing at least one selected from an aliphatic diol and an aromatic diol,
An asphalt composition , wherein the structural units derived from a carboxylic acid component include structural units derived from a carboxylic acid component that contain at least one selected from a branched alkyl succinic acid and a branched alkenyl succinic acid. The asphalt composition according to claim 1, wherein the total amount of the branched alkyl succinic acid and the branched alkenyl succinic acid in the carboxylic acid component is 3 mol % or more and 50 mol % or less based on 100 mol % of the carboxylic acid component. The asphalt composition according to claim 1 or 2, wherein the structural units derived from the carboxylic acid component include structural units derived from a branched alkenyl succinic acid. The asphalt composition according to any one of claims 1 to 3, wherein the content of the polyester is 1 part by mass or more and 25 parts by mass or less per 100 parts by mass of asphalt. The asphalt composition according to any one of claims 1 to 4, further comprising a thermoplastic elastomer. The asphalt composition according to claim 5, wherein the thermoplastic elastomer is 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 acid ester copolymers. An asphalt mixture comprising the asphalt composition according to any one of claims 1 to 6 and aggregate. A pavement paved with the asphalt mixture according to claim 7. A method for paving a road, comprising the step of applying the asphalt mixture according to claim 7 to a road to form an asphalt pavement layer. A method for producing an asphalt mixture, comprising a step of mixing heated aggregate, asphalt, and polyester,
the polyester contains a structural unit derived from an alcohol component and a structural unit derived from a carboxylic acid component,
The structural unit derived from an alcohol component includes a structural unit derived from an alcohol component containing at least one selected from an aliphatic diol and an aromatic diol,
A method for producing an asphalt mixture , wherein the structural units derived from a carboxylic acid component include structural units derived from a carboxylic acid component that contain at least one selected from a branched alkyl succinic acid and a branched alkenyl succinic acid. In the mixing step,
(i) adding and mixing asphalt to the heated aggregate, and then adding and mixing polyester;
(ii) adding and mixing the asphalt and polyester simultaneously to the heated aggregate; or (iii) adding and mixing a pre-heated mixture of asphalt and polyester to the heated aggregate.
The method for producing an asphalt mixture according to claim 10.