JP7796516B2 - Asphalt Modifier - Google Patents

Description

The present invention relates to an asphalt modifier, an asphalt composition, an asphalt mixture, and a road paving method.

Asphalt pavement, which uses asphalt mixture, 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 is formed by an asphalt mixture in which aggregate is bound with asphalt, the paved road has good hardness and durability.
However, asphalt pavement surfaces deteriorate over time, requiring repairs, which increases maintenance costs and significantly impacts automobile traffic.

Patent Document 1 discloses an asphalt composition that provides excellent durability of pavement surfaces after construction, the asphalt composition containing asphalt, a thermoplastic elastomer, and a specific amount of polyester, the polyester having a specific softening point and glass transition point.
Patent Document 2 discloses an asphalt composition containing asphalt and a polyester polymer, which is suitable for road paving, as it can be applied even at low temperatures, maintains stability even at high temperatures, and is less likely to leave ruts on the road surface caused by traveling vehicles.

Japanese Patent Application Laid-Open No. 2019-19325 Japanese Patent Application Publication No. 04-8766

By modifying asphalt with polyester, it is possible to obtain asphalt pavement that has excellent strength and durability.
On the other hand, asphalt, which has excellent durability, also has high viscoelasticity, which can lead to insufficient packing of the asphalt mixture when compacted by a roller during asphalt pavement construction. Insufficient compaction can lead to problems such as reduced durability and a deterioration in the surface appearance, so it is necessary to increase the number of compactions to achieve sufficient packing. However, compaction work accounts for a large portion of the construction process, and increasing the number of compactions can lead to reduced construction efficiency and increased traffic congestion due to increased traffic control times.
In other words, there is a demand for technology that can achieve high-strength asphalt pavement with fewer compaction runs.
The present invention relates to an asphalt modifier, an asphalt composition, an asphalt mixture, and a road paving method for obtaining an asphalt mixture that can achieve both high filling efficiency of the asphalt mixture and high strength of the asphalt pavement.

The present invention relates to the following [1] to [4].
[1] An asphalt modifier containing a crystalline polyester (A),
The crystalline polyester (A) contains a structural unit derived from an alcohol component (a1) and a structural unit derived from a carboxylic acid component (a2),
An asphalt modifier that is a crystalline polyester that satisfies at least one of the following conditions (i) and (ii):
(i) The carboxylic acid component (a2) contains a monovalent aliphatic carboxylic acid; (ii) The alcohol component (a1) contains a monovalent aliphatic alcohol. [2] An asphalt composition containing asphalt and the asphalt modifier described in [1] above.
[3] An asphalt mixture comprising asphalt, aggregate, crystalline polyester (A) and polyester (B),
The crystalline polyester (A) contains a structural unit derived from an alcohol component (a1) and a structural unit derived from a carboxylic acid component (a2),
A crystalline polyester that satisfies at least one of the following conditions (i) and (ii):
The polyester (B) contains a structural unit derived from an alcohol component (b1) and a structural unit derived from a carboxylic acid (b2), and the content of alkylene oxide adducts of bisphenol A in the alcohol component (b1) is 40 mol% or more.
(i) the carboxylic acid component (a2) contains a monohydric aliphatic carboxylic acid; and (ii) the alcohol component (a1) contains a monohydric aliphatic alcohol. [4] A road paving method comprising the step of applying the asphalt mixture according to [3] above to a road to form an asphalt pavement layer.

The present invention provides an asphalt modifier, asphalt composition, asphalt mixture, and road paving method for obtaining an asphalt mixture that achieves both high filling efficiency of the asphalt mixture and high strength of the asphalt pavement.

[Asphalt modifier]
The asphalt modifier of the present invention is an asphalt modifier containing a crystalline polyester (A),
The crystalline polyester (A) contains a structural unit derived from an alcohol component (a1) and a structural unit derived from a carboxylic acid component (a2),
The crystalline polyester satisfies at least one of the following conditions (i) and (ii):
(i) the carboxylic acid component (a2) contains a monohydric aliphatic carboxylic acid; and (ii) the alcohol component (a1) contains a monohydric aliphatic alcohol.

The present inventors have discovered that by incorporating a specified polyester (A) into an asphalt mixture containing asphalt, it is possible to achieve both improved filling efficiency of the asphalt mixture and improved strength of the asphalt pavement.
Although the detailed mechanism by which the effects of the present invention are obtained is unknown, part of it is thought to be as follows.
In the prior art, it is believed that the polar groups, i.e., carboxyl and hydroxyl groups, at the ends of the polyester main chain cause interactions between polyester molecules, resulting in an increase in viscosity and a decrease in fluidity in the binder.
In contrast, in the present invention, it is believed that the monohydric aliphatic carboxylic acid and/or monohydric aliphatic alcohol binds to the molecular terminal of the polyester to hydrophobize it, thereby suppressing thickening due to intermolecular interactions. Furthermore, it is believed that the aliphatic portion of the monohydric aliphatic carboxylic acid and/or monohydric aliphatic alcohol has a high affinity with hydrophobic asphalt and can plasticize the asphalt. It is believed that these effects contribute synergistically to increase the fluidity of the binder and improve the filling efficiency of the asphalt mixture.
Furthermore, as a result of the increased affinity between polyester and asphalt, the adhesion between the aggregate and asphalt via the polyester becomes stronger, which is thought to improve the strength of the asphalt pavement.

The definitions of various terms used in this specification are shown 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 a thermoplastic elastomer, as described below (hereinafter also referred to as "modified asphalt").
In the polyester, a "structural unit derived from an alcohol component" means a structure in which a hydrogen atom is removed from a hydroxy group of an alcohol component, and a "structural unit derived from a carboxylic acid component" means a structure in which a hydroxy group is removed from a carboxy group of a carboxylic acid component.
The term "carboxylic acid component" is a concept that includes not only the carboxylic acid itself, but also anhydrides that decompose during the reaction to produce an acid, and alkyl esters of carboxylic acids (for example, alkyl groups having 1 to 3 carbon atoms). When the carboxylic acid component is an alkyl ester of carboxylic acid, the number of carbon atoms of the alkyl group that is the alcohol residue of the ester is not counted in the number of carbon atoms of the carboxylic acid.
Whether a resin is crystalline or amorphous is determined by its crystallinity index. The crystallinity index is defined as the ratio of the softening point of the resin to the temperature of the maximum endothermic peak (softening point (°C)/maximum endothermic peak temperature (°C)). A crystalline resin is one with a crystallinity index of 0.3 or more and 1.4 or less. An amorphous resin is one in which no endothermic peak is observed, or if an endothermic peak is observed, one with a crystallinity index of less than 0.3 or more than 1.4. The crystallinity index can be appropriately adjusted by adjusting the types and ratios of raw material monomers, as well as production conditions such as reaction temperature, reaction time, and cooling rate.

[Crystalline polyester (A)]
The crystalline polyester (A) contains a structural unit derived from the alcohol component (a1) and a structural unit derived from the carboxylic acid component (a2), and satisfies at least one of the following conditions (i) and (ii):
(i) The carboxylic acid component (a2) contains a monohydric aliphatic carboxylic acid. (ii) The alcohol component (a1) contains a monohydric aliphatic alcohol. Hereinafter, the alcohol component (a1), the carboxylic acid component (a2), and the physical properties of the polyester will be described.

(Alcohol component (a1))
In the case of the above (ii), the alcohol component (a1) contains a monohydric aliphatic alcohol.
The monohydric aliphatic alcohol may have a straight or branched main chain, and 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, and even more preferably 12 or more carbon atoms, and preferably has 100 or less carbon atoms, more preferably 50 or less carbon atoms, and even more preferably 20 or less carbon atoms.
Examples of monohydric aliphatic alcohols include decanol, lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, arachidyl alcohol, docosanol, etc. These alcohol components may be used alone or in combination of two or more.

When the alcohol component (a1) contains a monohydric aliphatic alcohol, the content thereof is preferably 5 mol% or more, more preferably 6 mol% or more, even more preferably 7 mol% or more, and preferably 25 mol% or less, more preferably 20 mol% or less, even more preferably 15 mol% or less, based on 100 mol% of the alcohol component (a1).
The content of the aliphatic alcohol having 6 to 100 carbon atoms in the monohydric aliphatic alcohol is preferably 60 mol% or more, more preferably 75 mol% or more, even more preferably 90 mol% or more, and preferably 100 mol% or less.

The alcohol component (a1) further contains a dihydric or higher alcohol component. Examples of such alcohol components include diols and trihydric or higher polyhydric alcohols. Examples of diols include aliphatic diols, alicyclic diols, and aromatic diols. These dihydric or higher alcohol components can be used alone or in combination of two or more.
The aliphatic diol is preferably a saturated aliphatic diol, more preferably an α,ω-straight chain saturated aliphatic diol.
The aliphatic diol preferably has 2 or more carbon atoms, more preferably 3 or more carbon atoms, and even more preferably 6 or more carbon atoms, and preferably has 100 or less carbon atoms, more preferably 50 or less carbon atoms, even more preferably 20 or less carbon atoms, and even more preferably 12 or less 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, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, 1,18-octadecanediol, 1,20-eicosanediol, and other saturated aliphatic diols having 100 or less carbon atoms. Of these, ethylene glycol, 1,4-butanediol, 1,6-hexanediol, and 1,9-nonanediol are preferred.
Examples of alicyclic diols include hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane), alkylene oxide adducts of hydrogenated bisphenol A, cyclohexanediol, and cyclohexanedimethanol.

Examples of aromatic diols include bisphenol A (2,2-bis(4-hydroxyphenyl)propane) and alkylene oxide adducts of bisphenol A. Examples of alkylene oxide adducts of bisphenol A include the alkylene oxide adducts of bisphenol A represented by the following 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 the alkylene oxide adduct of bisphenol A represented by 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.

Preferably, the trihydric or higher polyhydric alcohol is a trihydric alcohol. Examples of trihydric or higher polyhydric alcohols include glycerin, pentaerythritol, trimethylolpropane, and sorbitol.

The alcohol component (a1) preferably comprises an aliphatic diol, more preferably a saturated aliphatic diol.
From the viewpoint of the filling efficiency and pavement strength of the asphalt mixture, the content of the aliphatic diol is preferably 20 mol% or more, more preferably 40 mol% or more, and even more preferably 50 mol% or more, based on 100 mol% of the alcohol component, and is preferably 100 mol% or less.
Among these, the alcohol component (a1) more preferably contains 6 to 20 saturated aliphatic diols.
From the viewpoint of the filling efficiency and pavement strength of the asphalt mixture, the content of saturated aliphatic diols of 6 to 20 is preferably 60 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more, based on 100 mol% of the alcohol component, and is preferably 100 mol% or less.

(Carboxylic Acid Component (a2))
When the above condition (i) is satisfied, the carboxylic acid component (a2) contains a monovalent aliphatic carboxylic acid.
The monovalent aliphatic carboxylic acid may have a straight or branched main chain, and is preferably a monovalent saturated aliphatic carboxylic acid.
The number of monovalent aliphatic carboxylic acids is preferably 6 or more, more preferably 10 or more, even more preferably 12 or more, and is preferably 100 or less, more preferably 50 or less, even more preferably 20 or less.
Examples of the monovalent aliphatic carboxylic acid include saturated monovalent aliphatic carboxylic acids such as lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid, and examples of unsaturated monovalent aliphatic carboxylic acids include oleic acid, linoleic acid, and linolenic acid.

When the carboxylic acid component (a2) contains a monovalent aliphatic carboxylic acid, the content thereof is preferably 5 mol% or more, more preferably 6 mol% or more, even more preferably 7 mol% or more, and preferably 25 mol% or less, more preferably 20 mol% or less, even more preferably 15 mol% or less, based on 100 mol% of the carboxylic acid component (a2).
The content of the aliphatic carboxylic acid having 6 to 100 carbon atoms in the monovalent aliphatic carboxylic acid is preferably 60 mol % or more, more preferably 75 mol % or more, even more preferably 90 mol % or more, and preferably 100 mol % or less.

The carboxylic acid component (a2) further contains a divalent or higher carboxylic acid component. Examples of the divalent or higher carboxylic acid component include dicarboxylic acids and polycarboxylic acid compounds having a valence of 3 to 6. Examples of the dicarboxylic acid include aliphatic dicarboxylic acids and aromatic dicarboxylic acids. These carboxylic acid components can be used alone or in combination of two or more.
Examples of the aliphatic dicarboxylic acid include saturated aliphatic dicarboxylic acids and unsaturated aliphatic dicarboxylic acids.
The number of carbon atoms in the main chain of the aliphatic dicarboxylic acid is preferably 4 or more, and preferably 20 or less, more preferably 18 or less, and even more preferably 16 or less, from the viewpoint of the filling efficiency and pavement strength of the asphalt mixture.
Examples of the saturated aliphatic dicarboxylic acid include succinic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, and eicosanedioic acid, and examples of the unsaturated aliphatic dicarboxylic acid include fumaric acid.
The number of carbon atoms of the aromatic dicarboxylic acid is preferably 8 or more, and preferably 20 or less, more preferably 16 or less, and even more preferably 12 or less, from the viewpoint of the filling efficiency and pavement strength of the asphalt mixture.
Examples of aromatic dicarboxylic acids include isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, anthracenedicarboxylic acid, phenanthrenedicarboxylic acid, etc. Among these, terephthalic acid is preferred.

The carboxylic acid component (a2) preferably contains at least one selected from unsaturated aliphatic dicarboxylic acids and aromatic dicarboxylic acids.
From the viewpoint of the filling efficiency and pavement strength of the asphalt mixture, the total content of the unsaturated aliphatic dicarboxylic acid and the aromatic dicarboxylic acid is preferably 70 mol% or more, more preferably 75 mol% or more, even more preferably 80 mol% or more, and even more preferably 85 mol% or more, based on 100 mol% of the carboxylic acid component, and is 100 mol% or less.

(Mole ratio of carboxylic acid component (a2) to alcohol component (a1))
The molar ratio of the carboxylic acid component (a2) to the alcohol component (a1) [carboxylic acid component (a1)/alcohol component (a2)] is preferably 0.6 or more, more preferably 0.7 or more, even more preferably 0.8 or more, from the viewpoints of the filling efficiency of the asphalt mixture and the strength of the asphalt pavement, and is preferably 1.5 or less, more preferably 1.3 or less, even more preferably 1.1 or less.

(Physical Properties of Crystalline Polyester (A))
From the viewpoint of the filling efficiency and pavement strength of the asphalt mixture, the softening point of the crystalline polyester (A) is preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 70°C or higher, and is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower.
From the same viewpoint, the melting point of the crystalline polyester (A) is preferably 50°C or higher, preferably 60°C or higher, and 150°C or lower, preferably 140°C or lower, more preferably 130°C or lower.
When the crystalline polyester (A) contains a monovalent aliphatic carboxylic acid as the carboxylic acid component (a2), the hydroxyl value of the crystalline polyester (A) is, from the same viewpoint, preferably 0.1 mgKOH/g or more, more preferably 0.5 mgKOH/g or more, even more preferably 1 mgKOH/g or more, and preferably 5 mgKOH/g or less, more preferably 4.5 mgKOH/g or less, even more preferably 4 mgKOH/g or less.
When the crystalline polyester (A) contains a monohydric aliphatic alcohol as the alcohol component (a1), the acid value of the crystalline polyester (A) is, from the same viewpoint, preferably 0.1 mgKOH/g or more, more preferably 0.5 mgKOH/g or more, even more preferably 1 mgKOH/g or more, and preferably 5 mgKOH/g or less, more preferably 4.5 mgKOH/g or less, even more preferably 4 mgKOH/g or less.
From the same viewpoint, the weight average molecular weight Mw of the crystalline polyester (A) is preferably 1,000 or more, more preferably 2,000 or more, even more preferably 3,000 or more, and is preferably 80,000 or less, more preferably 40,000 or less, even more preferably 20,000 or less.

[Polyester (B)]
The asphalt modifier of the present invention may further contain a polyester resin (B).
The polyester (B) contains a structural unit derived from an alcohol component (b1) and a structural unit derived from a carboxylic acid component (b2), and the content of alkylene oxide adduct of bisphenol A in the alcohol component (b1) is 40 mol % or more.
The polyester (B) may be an amorphous polyester or a crystalline polyester, and is preferably an amorphous polyester.
The physical properties of the alcohol component (b1), the carboxylic acid component (b2), and the polyester (B) will be described below.

(Alcohol component (b1))
The alcohol component (b1) contains 40 mol % or more of an alkylene oxide adduct of bisphenol A.
The alkylene oxide adduct of bisphenol A is preferably represented by the following 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 the alkylene oxide adduct 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 the rutting resistance and surface appearance of the asphalt pavement, the content of the alkylene oxide adduct of bisphenol A is preferably 30 mol% or more, more preferably 40 mol% or more, and preferably 100 mol% or less, based on 100 mol% of the alcohol component (b1).

The alcohol component (b1) may contain an alcohol component other than an alkylene oxide adduct of bisphenol A. Examples of such alcohol components include aliphatic diols, alicyclic diols, aromatic diols other than alkylene oxide adducts of bisphenol A, and trihydric or higher polyhydric alcohols. These alcohol components may be used alone or in combination of two or more.

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.
Examples of alicyclic diols include hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane), alkylene oxide adducts of hydrogenated bisphenol A, cyclohexanediol, and cyclohexanedimethanol.
Examples of the trihydric or higher polyhydric alcohol include trihydric alcohol, etc. Examples of the trihydric or higher polyhydric alcohol include glycerin, etc.

(Carboxylic acid component (b2))
Examples of the carboxylic acid component (b2) include aliphatic dicarboxylic acid compounds, aromatic dicarboxylic acid compounds, and polycarboxylic acid compounds having a valence of 3 to 6. These carboxylic acid components can be used alone or in combination of two or more.

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 preferably 10 or less, more preferably 8 or less, from the viewpoint of rutting resistance and surface appearance of the asphalt pavement.
Examples of aliphatic dicarboxylic acid compounds 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, dodecanedioic acid, and succinic acid substituted with an alkyl group having from 1 to 20 carbon atoms or an alkenyl group having from 2 to 20 carbon atoms. Examples of substituted succinic acids include dodecylsuccinic acid, dodecenylsuccinic acid, and octenylsuccinic acid. Among the above aliphatic dicarboxylic acid compounds, succinic acid substituted with an alkenyl group having from 2 to 20 carbon atoms is preferred.

Examples of aromatic dicarboxylic acid compounds include phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, etc. Among these aromatic dicarboxylic acid compounds, isophthalic acid and terephthalic acid are preferred, and terephthalic acid is more preferred, from the viewpoints of rutting resistance and surface appearance of asphalt pavement.
The trivalent or greater hexavalent polycarboxylic acid compound is preferably a trivalent carboxylic acid. Examples of trivalent or greater hexavalent polycarboxylic acid compounds include trimellitic acid, 2,5,7-naphthalenetricarboxylic acid, and pyromellitic acid. When a polycarboxylic acid compound is contained, from the viewpoint of the rutting resistance and surface appearance of the asphalt pavement, the alcohol component may appropriately contain a monohydric alcohol, and the carboxylic acid component may appropriately contain a monocarboxylic acid compound.

From the viewpoint of the rutting resistance and surface appearance of the asphalt pavement, the content of the aliphatic dicarboxylic acid compound in the carboxylic acid component (a2) is preferably 1 mol% or more, more preferably 5 mol% or more, even more preferably 7 mol% or more, and is preferably 40 mol% or less, more preferably 30 mol% or more, even more preferably 25 mol% or less.
From the viewpoint of the rutting resistance and surface appearance of the asphalt pavement, the content of the aromatic dicarboxylic acid compound is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 75 mol%, and is 100 mol% or less, preferably 98 mol% or less, more preferably 95 mol% or less, even more preferably 90 mol% or less, based on 100 mol% of the carboxylic acid component.

In one preferred embodiment of the present invention, the carboxylic acid component (a2) contains a total of 40 mol% or more of one or more acids selected from the group consisting of terephthalic acid and isophthalic acid. From the viewpoint of the rutting resistance and surface appearance of the asphalt pavement, this is more preferably 75 mol% or more, even more preferably 90 mol% or more, and preferably 100 mol% or less.

(Molar ratio of carboxylic acid component (b2) to alcohol component (b1))
The molar ratio of the carboxylic acid component (b2) to the alcohol component (b1) [carboxylic acid component (b2)/alcohol component (b1)] is preferably 0.6 or more, more preferably 0.7 or more, even more preferably 0.8 or more, from the viewpoint of the rutting resistance and surface appearance of the asphalt pavement, and is preferably 1.5 or less, more preferably 1.3 or less, even more preferably 1.1 or less.

(Structural unit derived from polyethylene terephthalate)
The polyester (B) may contain ethylene glycol-derived structural units and terephthalic acid-derived structural units derived from polyethylene terephthalate. The polyethylene terephthalate may contain small amounts of components such as butanediol and isophthalic acid in addition to the ethylene glycol-derived and terephthalic acid-derived structural units. The polyethylene terephthalate is preferably recycled polyethylene terephthalate.
When the polyester (A) contains structural units derived from ethylene glycol and terephthalic acid derived from polyethylene terephthalate, the "structural units derived from the alcohol component (a1)" contain structural units derived from ethylene glycol derived from polyethylene terephthalate, and the "structural units derived from the carboxylic acid component (a2)" contain structural units derived from terephthalic acid derived from polyethylene terephthalate.

(Physical properties of polyester (B))
From the viewpoint of the rutting resistance and surface appearance of the asphalt pavement, the softening point of the polyester (B) 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 120°C or lower.
From the same viewpoint, the hydroxyl value of the polyester (B) is preferably 5 mgKOH/g or more, more preferably 10 mgKOH/g or more, and preferably 70 mgKOH/g or less, more preferably 60 mgKOH/g or less, even more preferably 40 mgKOH/g or less, and even more preferably 30 mgKOH/g or less.
From the same viewpoint, the weight average molecular weight Mw of the polyester (B) is preferably 5,000 or more, more preferably 7,000 or more, even more preferably 8,000 or more, and is preferably 70,000 or less, more preferably 40,000 or less, even more preferably 25,000 or less.

The softening point, hydroxyl value, and weight-average molecular weight Mw of polyester (B) can be measured by the methods described in the Examples. The softening point, hydroxyl value, and weight-average molecular weight Mw can be adjusted by the raw material monomer composition, molecular weight, catalyst amount, or reaction conditions.

Polyester (B) may be modified to an extent that does not substantially impair its properties. Specific examples of modified polyesters include polyesters grafted or blocked with phenol, urethane, epoxy, etc., using methods described in JP-A Nos. 11-133668, 10-239903, and 8-20636. A preferred modified polyester is a urethane-modified polyester in which polyester is urethane-extended with a polyisocyanate compound.

From the viewpoint of the filling efficiency of the asphalt mixture and pavement strength, the content ratio of crystalline polyester (A) to polyester (B) in the asphalt modifier is preferably polyester (B)/crystalline polyester (A) by mass ratio of 60/40 or more, more preferably 65/45 or more, even more preferably 70/30 or more, even more preferably 75/25 or more, and even more preferably 80/20 or less, and is preferably 99/1 or less, more preferably 98/2 or less, even more preferably 97/3 or less, even more preferably 95/5 or less, and even more preferably 90/10 or less.

(Method for producing polyester)
The method for producing the crystalline polyester (A) and polyester (B) constituting the asphalt modifier of the present invention is not particularly limited. For example, they can be produced by polycondensing the above-mentioned alcohol component (a1) and carboxylic acid component (a2), and the above-mentioned alcohol component (b1) and carboxylic acid component (b2).
The temperature of the polycondensation reaction is not particularly limited, but is preferably 160° C. or higher and 260° C. or lower in terms of adjusting the reactivity and improving the rutting resistance and surface appearance of the asphalt pavement.

When the polyester used in the present invention contains constitutional units derived from ethylene glycol derived from polyethylene terephthalate and constitutional units derived from terephthalic acid derived from polyethylene terephthalate, the amount of polyethylene terephthalate present in the raw material is preferably 5 to 80 mass%, more preferably 15 to 70 mass%, and even more preferably 25 to 60 mass%, of the total amount of polyethylene terephthalate, the alcohol component, and the carboxylic acid component.
By adding polyethylene terephthalate during the polycondensation reaction between the alcohol component and the carboxylic acid component, an ester exchange reaction occurs, and a polyester can be obtained in which the structural units of polyethylene terephthalate are incorporated into structural units derived from the alcohol component and structural units derived from the carboxylic acid component.
Polyethylene terephthalate may be present from the start of the polycondensation reaction or may be added to the reaction system during the polycondensation reaction. From the viewpoint of the rutting resistance and surface appearance of the asphalt pavement, the timing of adding polyethylene terephthalate is preferably when the reaction rate between the alcohol component and the carboxylic acid component is 10% or less, more preferably 5% or less. The reaction rate refers to the value of the amount of water produced by reaction (mol) / the theoretical amount of water produced (mol) × 100.

In view of the reaction rate, an esterification catalyst can be used in the polycondensation reaction. Examples of the esterification catalyst include tin(II) compounds that do not have a Sn—C bond, such as tin(II) di(2-ethylhexanoate). In view of the reaction rate, the amount of the esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.2 parts by mass or more, and is preferably 1.5 parts by mass or less, more preferably 1.0 part by mass or less, and even 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 addition to the esterification catalyst, a co-catalyst can be used in the polycondensation reaction. Examples of the co-catalyst include pyrogallol compounds such as gallic acid. The amount of the co-catalyst used is preferably 0.001 parts by mass or more, more preferably 0.005 parts by mass or more, and even more preferably 0.01 parts by mass or more, and preferably 0.15 parts by mass or less, more preferably 0.10 parts by mass or less, and even more preferably 0.05 parts by mass or less, per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.
In addition to the catalyst, a polymerization inhibitor such as tertiary butyl catechol can be used in the polycondensation reaction from the viewpoint of reaction rate. The amount of the polymerization inhibitor used is preferably 0.001 part by mass or more, more preferably 0.01 part by mass or more, and preferably 0.5 part by mass or less, more preferably 0.2 part by mass or less, per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

The asphalt modifier of the present invention can be used, for example, by mixing it with asphalt to obtain an asphalt composition.
Heated aggregate is added to the obtained asphalt composition to form an asphalt mixture, which can then be used for paving. The asphalt modifier of the present invention can be suitably used as an asphalt modifier to be blended into asphalt mixtures containing aggregate.

[Asphalt composition]
The asphalt composition of the present invention contains asphalt and the asphalt modifier, that is, the crystalline polyester (A) and, if necessary, the polyester (B).
<Asphalt>
Various types of asphalt can be used. Examples include straight asphalt, which is petroleum asphalt for paving, as well as modified asphalt. Examples of modified asphalt include blown asphalt and polymer-modified asphalt modified with polymeric materials such as thermoplastic elastomers and thermoplastic resins. Straight asphalt refers to the residual bituminous material obtained by subjecting crude oil to atmospheric distillation equipment, vacuum distillation equipment, etc. Blown asphalt refers to asphalt obtained by heating a mixture of straight asphalt and heavy oil and then blowing air into it to oxidize it. The asphalt is preferably selected from straight asphalt and polymer-modified asphalt, with polymer-modified asphalt being more preferred from the viewpoint of the durability of the asphalt pavement and straight asphalt being more preferred from the viewpoint of versatility. As polymer-modified asphalt, asphalt modified with a thermoplastic elastomer is more preferred.
The modified asphalt is preferably a polymer-modified asphalt, more preferably a polymer-modified asphalt modified with a thermoplastic elastomer.

(thermoplastic elastomer)
Examples of the thermoplastic elastomer in the polymer modified asphalt modified with a thermoplastic elastomer include styrene / butadiene block copolymer (hereinafter also referred to as "SB"), styrene / butadiene / styrene block copolymer (hereinafter also referred to as "SBS"), styrene / butadiene random copolymer (hereinafter also referred to as "SBR"), styrene / isoprene block copolymer (hereinafter also referred to as "SI"), styrene / isoprene / styrene block copolymer (hereinafter also referred to as "SIS"), styrene / isoprene random copolymer (hereinafter also referred to as "SIR"), ethylene / vinyl acetate copolymer, ethylene / acrylic acid ester copolymer, styrene / ethylene / butylene / styrene copolymer, styrene / ethylene / propylene / styrene copolymer, polyurethane-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, isobutylene / isoprene copolymer, polyisoprene, polychloroprene, synthetic rubber other than the above, and at least one selected from natural rubber. 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 acid ester copolymers.
Among these, from the viewpoint of rutting resistance of asphalt pavement, the thermoplastic elastomer is preferably at least one selected from SB, SBS, SBR, SI, SIS, SIR, and ethylene/acrylic acid ester copolymer, more preferably at least one selected from SB, SBS, SBR, SI, SIS, and SIR, and even more preferably at least one selected from SBR and SBS.
From the viewpoint of the filling efficiency of the asphalt mixture and the pavement strength, the content of the thermoplastic elastomer in the polymer modified asphalt is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less.

<Contents of Crystalline Polyester (A) and Polyester (B)>
In the asphalt composition of the present invention, the content of the crystalline polyester (A) is preferably at least 0.1 parts by mass, more preferably at least 0.5 parts by mass, and is preferably at most 2 parts by mass, more preferably at most 1.8 parts by mass, and even more preferably at most 1.5 parts by mass, per 100 parts by mass of asphalt, from the viewpoints of the filling efficiency of the asphalt mixture and the pavement strength.
The total content of the crystalline polyester (A) and the polyester (B) contained as needed in the asphalt composition of the present invention is preferably at least 1 part by mass, more preferably at least 5 parts by mass, and even more preferably at least 10 parts by mass, per 100 parts by mass of asphalt, from the viewpoint of the filling efficiency of the asphalt mixture and the pavement strength, and is preferably at most 40 parts by mass, more preferably at most 35 parts by mass, and more preferably at most 30 parts by mass, from the viewpoint of workability.

The asphalt composition of the present invention is a binder composition, and can be used for paving after, for example, adding aggregate to the asphalt composition to form an asphalt mixture. In other words, the asphalt composition of the present invention is suitable for paving, and is particularly suitable for road paving.

<Method for producing asphalt composition>
The method for producing the asphalt composition of the present invention preferably includes a step of mixing asphalt with the crystalline polyester (A) and, if necessary, the polyester (B).

The asphalt composition is obtained by heating and melting asphalt, adding crystalline polyester (A) and, if necessary, polyester (B), and stirring and mixing using a commonly used mixer until the components are uniformly dispersed. Commonly used mixers include homomixers, dissolvers, paddle mixers, ribbon mixers, screw mixers, planetary mixers, vacuum countercurrent mixers, roll mills, and twin-screw extruders.

From the viewpoint of uniformly dispersing the crystalline polyester (A) and polyester (B) in the asphalt, the mixing temperature of the asphalt with the crystalline polyester (A) and, if necessary, polyester (B) is preferably 100°C or higher, more preferably 130°C or higher, even more preferably 160°C or higher, still more preferably 170°C or higher, and preferably 230°C or lower, more preferably 210°C or lower, even more preferably 200°C or lower, and still more preferably 190°C or lower.

Furthermore, from the viewpoint of efficiently and uniformly dispersing the crystalline polyester (A) and, if necessary, the polyester (B) in the asphalt, the mixing time for mixing the asphalt with the crystalline polyester (A) and the polyester (B) is preferably 0.1 hour or more, more preferably 0.5 hour or more, even more preferably 1.0 hour or more, still more preferably 1.5 hour or more, and is preferably 10 hours or less, more preferably 7 hours or less, even more preferably 5 hours or less, and still more preferably 3 hours or less.

[Asphalt mixture]
The asphalt mixture of the present invention contains asphalt, aggregate, crystalline polyester (A), and optionally polyester (B). The asphalt mixture of the present invention is also formed by blending asphalt, aggregate, crystalline polyester (A), and optionally polyester (B). The asphalt mixture of the present invention is suitable for paving, and is particularly suitable for road paving.

<Aggregate>
The aggregate can be selected from crushed stone, boulders, gravel, sand, recycled aggregate, ceramics, etc. In addition, the aggregate can 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 or more and less than 4.75 mm, crushed stone with a particle size range of 4.75 mm or more and less than 12.5 mm, crushed stone with a particle size range of 12.5 mm or more and less than 19 mm, and crushed stone with a particle size range of 19 mm or more and less than 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 A5001:2008.
Among these, a combination of coarse aggregate and fine aggregate is preferred.

The fine aggregate may contain a filler with a particle size of less than 0.075 mm. Examples of fillers include sand, fly ash, calcium carbonate such as limestone powder, and slaked lime. Of these, calcium carbonate is preferred from the viewpoint of improving the strength of the asphalt pavement.
From the viewpoint of improving dry strength, the average particle size of the filler is preferably 0.001 mm or more, and preferably 0.06 mm or less, more preferably 0.04 mm or less, and even more preferably 0.03 mm or less. The average particle size of the filler can be measured using a laser diffraction particle size distribution analyzer. Here, the average particle size means the average particle size at 50% cumulative volume.

From the viewpoint of the rutting resistance of the asphalt pavement, 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 preferably 90/10 or less, more preferably 80/20 or less, even more preferably 70/30 or less.

Suitable examples of blending in asphalt mixtures include the following (1) to (3).
(1) For example, a fine-grained asphalt containing 30% by volume or more but less than 45% by volume of coarse aggregate, 30% by volume or more but less than 50% by volume of fine aggregate, and 5% by volume or more but less than 10% by volume of an asphalt composition.
(2) For example, a dense-graded asphalt containing 45% by volume or more but less than 70% by volume of coarse aggregate, 20% by volume or more but less than 45% by volume of fine aggregate, and 3% by volume or more but less than 10% by volume of an asphalt composition.
(3) For example, a 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.

The above porous asphalt can be suitably used for drainage pavement.

From the viewpoint of rutting resistance and surface appearance, the aggregate content in the asphalt mixture is preferably 50% by mass or more, more preferably 75% by mass or more, even more preferably 80% by mass or more, and preferably 99% by mass or less, more preferably 98% by mass or less, even more preferably 96% by mass or less.

The asphalt mixing ratio in conventional asphalt mixtures containing aggregate and asphalt is usually determined according to the optimal amount of asphalt determined from the "Mix Design of Asphalt Compositions" described in the "Guidelines for Pavement Design and Construction" published by the Japan Road Association, a public interest incorporated association.
In the present invention, the above-mentioned optimum amount of asphalt corresponds to the total amount of asphalt, the crystalline polyester (A), and the polyester (B) contained as needed. However, it is not necessary to be limited to the method described in the "Guidelines for Pavement Design and Construction," and it may be determined by other methods.

From the viewpoint of the rutting resistance of the asphalt pavement, the asphalt content in the asphalt mixture is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 4% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less.

(Polyester content)
The total content of the crystalline polyester (A) and the polyester (B) contained as needed in the asphalt mixture of the present invention is preferably at least 1 part by mass, more preferably at least 5 parts by mass, and even more preferably at least 10 parts by mass, per 100 parts by mass of asphalt, from the viewpoint of the filling efficiency of the asphalt mixture and the pavement strength, and from the viewpoint of workability, is preferably at most 40 parts by mass, more preferably at most 35 parts by mass, and more preferably at most 30 parts by mass.
From the viewpoint of the filling efficiency of the asphalt mixture and the pavement strength, the content ratio of the crystalline polyester (A) to the polyester (B) in the asphalt mixture is, in mass ratio, polyester (B)/polyester (A), preferably 60/40 or more, more preferably 65/45 or more, even more preferably 70/30 or more, even more preferably 75/25 or more, even more preferably 80/20 or more, and is preferably 99/1 or less, more preferably 98/2 or less, even more preferably 97/3 or less, even more preferably 95/5 or less.

The asphalt mixture may further contain other components as needed.

[Method for producing asphalt mixture]
The asphalt mixture of the present invention can be obtained by blending asphalt, heated aggregate, the crystalline polyester (A), and, if necessary, the polyester (B). The method for producing an asphalt mixture of the present invention includes a step of simultaneously mixing asphalt, heated aggregate, the crystalline polyester (A), and, if necessary, the polyester (B), either simultaneously or in any order.
Specific methods for producing asphalt mixtures include conventional methods known as the plant mix method and the premix method, both of which involve adding asphalt and polyester to heated aggregate.
The mixing step is preferably any one of the following steps (i) to (iii):
(i) adding and mixing asphalt to heated aggregate, and then adding and mixing the crystalline polyester (A) and, if necessary, the polyester (B);
(ii) Asphalt, crystalline polyester (A), and, if necessary, polyester (B) are simultaneously added to and mixed with the heated aggregate, or (iii) a mixture of asphalt, crystalline polyester (A), and, if necessary, polyester (B), which has been preheated and mixed, is added to and mixed with the heated aggregate.

When polyester (B) is used, crystalline polyester (A) and polyester (B) may be added simultaneously or separately. When added separately, polyester (B) may be added after crystalline polyester (A), or crystalline polyester (A) may be added after polyester (B).

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

The mixing temperature of the aggregate with asphalt and/or polyester is preferably 130°C or higher, more preferably 150°C or higher, and even more preferably 170°C or higher, from the viewpoint of rutting resistance of the asphalt pavement, and is preferably 230°C or lower, more preferably 210°C or lower, and even more preferably 200°C or lower, from the viewpoint of preventing thermal degradation of the asphalt.
The mixing time of the aggregate with the asphalt and/or polyester is not particularly limited, but is preferably 30 seconds or more, more preferably 1 minute or more, and even more preferably 2 minutes or more. The upper limit of the time is not particularly limited, but is preferably about 30 minutes.

From the viewpoint of the rutting resistance of the asphalt pavement, the method for producing an asphalt mixture preferably includes a step of holding the resulting mixture at the above-mentioned mixing temperature after the mixing step.
In the step of holding the asphalt mixture, the mixture may be further mixed.
The retention time is preferably 0.2 hours or more, more preferably 0.3 hours or more, and even more preferably 0.5 hours or more. The upper limit of the time is not particularly limited, but is, for example, about 5 hours.

[Road paving method]
The asphalt mixture of the present invention is suitable for road paving and is used for road paving.
The road paving method includes a step of applying the asphalt mixture to a road to form an asphalt pavement layer. Specifically, the road paving method includes a step (step 1) of mixing asphalt, the crystalline polyester (A) and, if necessary, polyester (B), and aggregate to obtain an asphalt mixture, 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 usually a base layer or a surface layer, and is preferably a surface layer from the viewpoint of exhibiting the effects of rut resistance and surface aesthetics.

From the viewpoint of rutting resistance and surface aesthetics, the thickness of the asphalt pavement layer is preferably 3 cm or more, more preferably 4 cm or more, even more preferably 4.5 cm or more, and preferably 7 cm or less, more preferably 6 cm or less, even more preferably 5.5 cm or less. In another aspect of the present invention, the asphalt pavement layer can be a thin-layer pavement, and the thickness of the surface layer is preferably 1 cm or more, more preferably 1.5 cm or more, even more preferably 2 cm or more, and preferably 4 cm or less, more preferably 3.5 cm or less, even more preferably 3 cm or less.
The asphalt mixture may be compacted and applied in the same manner using a known construction machine. When used as a heated asphalt mixture, the compaction temperature is preferably 100°C or higher, more preferably 120°C or higher, and even more preferably 130°C or higher, from the viewpoint of the rutting resistance of the asphalt pavement, and is preferably 200°C or lower, more preferably 180°C or lower.

Various physical properties were measured and evaluated by the following methods.
In the following examples and comparative examples, parts and percentages are by mass unless otherwise specified.

[Softening point (Ts) of polyester]
Using a flow tester "CFT-500D" (Shimadzu Corporation), 1 g of sample was heated at a temperature increase rate of 6°C/min, while a load of 1.96 MPa was applied by the plunger, and the sample was extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. The plunger depression distance 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.

[Crystallinity index]
Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan Co., Ltd.), 0.02 g of a sample was weighed into an aluminum pan and cooled from room temperature (20°C) at a rate of 10°C.
The sample was cooled to 0°C at a rate of °C/min. The sample was then maintained at that temperature for 1 minute, and then the heat quantity was measured while the temperature was increased to 180°C at a rate of 10°C/min. Among the endothermic peaks observed, the temperature of the peak with the largest peak area was taken as the maximum endothermic peak temperature (Tmax).
The crystallinity index was calculated from Ts/Tmax.
The crystalline polyester has a crystallinity index of 0.6 or more and 1.4 or less.

[Melting point (Tm) and glass transition point (Tg) of polyester]
Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan Co., Ltd.), 0.01 to 0.02 g of sample was weighed into an aluminum pan and heated to 200°C.
From that temperature, the temperature was lowered to 0°C at a rate of 10°C/min.
The temperature was measured while increasing the temperature to 0°C. The temperature of the peak with the largest peak area was measured at a temperature where the difference between the peak area and the softening point was 2.
If it was within 0°C, it was taken as the melting point.
The glass transition temperature 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 peak apex.

[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)).

Production Examples 1 and 4 to 6 (Polyesters A1 and A4 to A6)
The raw material monomers other than stearic acid shown in Table 1 and 2 g of tertiary butyl catechol were placed in a 10 L four-neck flask equipped with a thermometer, a stainless steel stirring rod, a dehydration tube, a nitrogen inlet tube, and a thermocouple. In a nitrogen atmosphere, the amount of tin(II) di(2-ethylhexanoate) shown in Table 2 was added, the mixture was maintained at 140°C for 6 hours, and then heated to 200°C over 6 hours. The mixture was then reacted at 200°C for 1 hour and then cooled to 180°C. Next, stearic acid was added, and the mixture was heated from 180°C to 210°C over 3 hours. After reaching 210°C, the mixture was reacted at 8.3 kPa for 1 hour to obtain polyesters A1, A4, and A6. The results are shown in Table 1.

Production Example 2 (Polyester A2)
The raw material monomers other than stearyl alcohol shown in Table 1 and 2 g of tertiary butyl catechol were placed in a 10 L four-neck flask equipped with a thermometer, a stainless steel stirring rod, a dehydration tube, a nitrogen inlet tube, and a thermocouple. In a nitrogen atmosphere, the amount of tin(II) di(2-ethylhexanoate) shown in Table 2 was added, the mixture was maintained at 140°C for 6 hours, and then heated to 200°C over 6 hours. The mixture was then reacted at 200°C for 1 hour and then cooled to 180°C. Next, stearyl alcohol was added, and the mixture was heated from 180°C to 210°C over 3 hours. After reaching 210°C, the mixture was reacted at 8.3 kPa for 1 hour to obtain Polyester A2. The results are shown in Table 1.

Production Example 3 (Polyester A3)
The raw material monomers other than lauric acid shown in Table 1 and 2 g of tertiary butyl catechol were placed in a 10 L four-neck flask equipped with a thermometer, a stainless steel stirring rod, a dehydration tube, a nitrogen inlet tube, and a thermocouple. In a nitrogen atmosphere, the amount of tin(II) di(2-ethylhexanoate) shown in Table 2 was added, the mixture was maintained at 140°C for 6 hours, and then heated to 200°C over 6 hours. The mixture was then reacted at 200°C for 1 hour and then cooled to 180°C. Lauric acid was then added, and the mixture was heated from 180°C to 210°C over 3 hours. After reaching 210°C, the mixture was reacted at 8.3 kPa for 1 hour to obtain Polyester A3. The results are shown in Table 1.

Production Example 7 (Polyester B1)
The raw material monomers shown in Table 2 were placed in a 10 L four-neck flask equipped with a thermometer, a stainless steel stirring rod, a dehydration tube, a nitrogen inlet tube, and a thermocouple, and tin(II) di(2-ethylhexanoate) and gallic acid were added in a nitrogen atmosphere, followed by heating to 235°C. The reaction was then carried out at 235°C for 8 hours, and then further carried out at 235°C under reduced pressure of 8.3 kPa until the softening point shown in Table 2 was reached, yielding Polyester B1. The results are shown in Table 2.

Production Example 8 (Polyester B2)
Among the raw material monomers shown in Table 2, the alcohol component, terephthalic acid, and PET (polyethylene terephthalate) were placed in a 10 L four-neck flask equipped with a thermometer, a stainless steel stirring rod, a dehydration tube, a downflow condenser, and a nitrogen inlet tube. The amount of tin(II) di(2-ethylhexanoate) shown in Table 1 was added under a nitrogen atmosphere. The mixture was heated to 235°C over 3 hours in a mantle heater, maintained at 235°C for 5 hours, and then reacted under reduced pressure at 8.0 kPa for 1 hour. After visually confirming the disappearance of PET particles from the reaction mixture, the mixture was cooled to 180°C and alkenylsuccinic anhydride was added. The mixture was heated to 210°C over 2 hours, maintained at 210°C for 1 hour, and then reacted under reduced pressure at 8.3 kPa. The reaction was continued until the softening point shown in Table 2 was reached, yielding Polyester B2. The results are shown in Table 2.
The alkenyl succinic anhydride used was dodecenyl succinic anhydride (average molecular weight 256).

Production Example 9 (Polyester B3)
The alcohol component, terephthalic acid, and PET (polyethylene terephthalate) from the raw material monomers shown in Table 2 were placed in a 10 L four-neck flask equipped with a thermometer, a stainless steel stirring rod, a dehydration tube, a downflow condenser, and a nitrogen inlet tube. The amount of tin(II) di(2-ethylhexanoate) shown in Table 1 was added under a nitrogen atmosphere. The mixture was heated to 235°C over 3 hours in a mantle heater and maintained at 235°C for 5 hours, after which a reaction was carried out under reduced pressure at 8.0 kPa for 1 hour. After visually confirming that the PET particles had disappeared from the reaction mixture, the mixture was cooled to 180°C. Next, adipic acid was added, and the mixture was heated from 180°C to 210°C over 3 hours. After reaching 210°C, the reaction was continued at 10 kPa until the softening point shown in Table 2 was reached, yielding Polyester B3. The results are shown in Table 2.

Production Example 10 (Polyester C1)
The raw material monomers shown in Table 2 and 2 g of tert-butylcatechol were placed in a 10 L four-neck flask equipped with a thermometer, a stainless steel stirring rod, a dehydration tube, a nitrogen inlet tube, and a thermocouple, and the flask was maintained at 140°C for 6 hours under a nitrogen atmosphere, and then heated to 200°C over 6 hours. After that, tin(II) di(2-ethylhexanoate) and gallic acid were added and reacted at 200°C for 1 hour, and then at 8.3 kPa for 1 hour to obtain polyester C1. The results are shown in Table 2.

Production Example 11 (Polyester C2)
The raw material monomers shown in Table 2 were placed in a 10 L four-neck flask equipped with a thermometer, a stainless steel stirring rod, a dehydration tube, a nitrogen inlet tube, and a thermocouple, and the amounts of di(tin 2-ethylhexanoate)(II) and gallic acid shown in Table 2 were added under a nitrogen atmosphere. The mixture was maintained at 180°C for 2 hours, heated to 210°C over 3 hours, and reacted at 210°C for 4 hours, followed by reacting at 8.3 kPa for 1 hour to obtain polyester C2. The results are shown in Table 2.

Example 1
15 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, 0.82 kg of modified type II asphalt (Epoch Falt D manufactured by Nisshin Seiki Co., Ltd.) heated to 180 ° C was added and mixed for 1 minute in the asphalt mixer. Then, 152.2 g of Polyester A1 obtained in Production Example 1 and 12.3 g of Polyester B1 obtained in Production Example 4 were simultaneously added and mixed for another 1 minute to obtain asphalt mixture AS-1.
1180 g of the resulting asphalt mixture AS-1 was filled into a formwork and compacted on both sides 20 times using an automatic asphalt compaction device (NA-507) manufactured by Nakajima Gihan Co., Ltd. After compacting 20 times on each side, the mixture was allowed to cool to room temperature for 15 hours to obtain asphalt specimen M-1. The filling efficiency of the asphalt mixture was evaluated by measuring the void ratio of this specimen, and the pavement strength was evaluated by measuring the Marshall stability. The results are shown in Table 3. The void ratio measurement was performed in accordance with "B008-1 Density Test Method for Dense-Grade Asphalt Mixtures, etc.", and the Marshall stability test was performed in accordance with "B001 Marshall Stability Test Method."

<Aggregate composition>
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 Passed mass %:
Sieve size 19.0 mm: 100% by mass
Sieve size 9.50 mm: 80.1% by mass
Sieve size 4.75 mm: 59.4% by mass
Sieve size 2.36 mm: 43.4% by mass
Sieve size 1.18 mm: 29.1% by mass
Sieve size 600 μm: 18.9% by mass
Sieve size 300 μm: 11.7 mass%
Sieve size 150 μm: 7.6 mass%

Examples 2 to 10, Comparative Examples 1 to 5
Asphalt specimens were prepared in the same manner as in Example 1, except that the formulation was changed to that shown in Table 3.

The results in Table 3 show that Examples 1 to 10, which contain specific asphalt modifiers, achieve good asphalt mixture filling efficiency and improve the strength of the asphalt pavement. This effect is also achieved in Examples 9 and 10, which do not contain polyester (B). Furthermore, Examples 1 to 8, which contain polyester (B), demonstrate an extremely high synergistic effect.
In Comparative Example 1, in which no polyester was added, both the filling efficiency of the asphalt mixture and the strength of the asphalt pavement were insufficient. In Comparative Examples 2 to 5, the filling efficiency of the asphalt mixture was inferior to that of Comparative Example 1. From Comparative Examples 2 and 3, it can be seen that increasing the amount of polyester other than that of the present invention reduces the filling efficiency of the asphalt mixture.

Claims (15)

An asphalt modifier comprising a crystalline polyester (A),
The crystalline polyester (A) contains a structural unit derived from an alcohol component (a1) and a structural unit derived from a carboxylic acid component (a2),
The crystalline polyester satisfies at least one of the following conditions (i) and (ii):
An asphalt modifier , wherein the crystalline polyester (A) has a hydroxyl value of 0.1 mgKOH/g or more and 5 mgKOH/g or less when the crystalline polyester (A) satisfies the following condition (i):
(i) the carboxylic acid component (a2) contains a monohydric aliphatic carboxylic acid; (ii) the alcohol component (a1) contains a monohydric aliphatic alcohol; The asphalt modifier according to claim 1, wherein the content of monovalent aliphatic carboxylic acid in the carboxylic acid component (a2) is 5 mol% or more and 25 mol% or less. The asphalt modifier according to claim 1 or 2, wherein the content of monovalent fatty acids having 6 to 100 carbon atoms in the monovalent aliphatic carboxylic acids is 60 mol% or more. The asphalt modifier according to any one of claims 1 to 3, wherein the content of monohydric aliphatic alcohol in the alcohol component (a1) is 5 mol% or more and 25 mol% or less. The asphalt modifier according to any one of claims 1 to 4, wherein the content of monohydric aliphatic alcohols having 6 to 100 carbon atoms is 60 mol% or more. The asphalt modifier according to any one of claims 1 to 5, wherein the content of saturated aliphatic diols having 6 to 20 carbon atoms in the alcohol component (a1) is 60 mol% or more. The asphalt modifier according to any one of claims 1 to 6, wherein the alcohol component (a1) contains a monohydric aliphatic alcohol, and the acid value of the crystalline polyester (A) is 0.1 mgKOH/g or more and 5 mgKOH/g or less. An asphalt modifier further comprising a polyester (B),
The asphalt modifier according to any one of claims 1 to 7, wherein the polyester (B) comprises a structural unit derived from an alcohol component (b1) and a structural unit derived from a carboxylic acid (b2), and the content of alkylene oxide adducts of bisphenol A in the alcohol component ( b1 ) is 40 mol% or more. The asphalt modifier according to claim 8 , wherein the total content of at least one selected from terephthalic acid and isophthalic acid in the carboxylic acid component (b2) is 40 mol% or more. The asphalt modifier according to claim 8 or 9 , wherein the mass ratio (B)/(A) of the polyester (B) to the polyester (A) is 60/40 or more and 99/1 or less. An asphalt composition comprising asphalt and the asphalt modifier according to any one of claims 1 to 10 . The asphalt composition according to claim 11 , wherein the content of the crystalline polyester (A) is 0.1 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the asphalt. An asphalt mixture comprising asphalt, aggregate, crystalline polyester (A) and polyester (B),
The crystalline polyester (A) contains a structural unit derived from an alcohol component (a1) and a structural unit derived from a carboxylic acid component (a2),
The crystalline polyester satisfies at least one of the following conditions (i) and (ii):
When the crystalline polyester (A) satisfies the following condition (i), the hydroxyl value of the crystalline polyester (A) is 0.1 mgKOH/g or more and 5 mgKOH/g or less,
The polyester (B) contains a structural unit derived from an alcohol component (b1) and a structural unit derived from a carboxylic acid (b2), and the content of alkylene oxide adducts of bisphenol A in the alcohol component (b1) is 40 mol% or more.
(i) the carboxylic acid component (a2) contains a monohydric aliphatic carboxylic acid; (ii) the alcohol component (a1) contains a monohydric aliphatic alcohol; The asphalt mixture according to claim 13 , wherein the total content of the crystalline polyester (A) and the polyester (B) is 1 part by mass or more and 40 parts by mass or less per 100 parts by mass of the asphalt. A road paving method, comprising the step of applying the asphalt mixture according to claim 13 or 14 to a road to form an asphalt pavement layer.