Asphalt Modifier

Abstract

To provide an asphalt modifier that has excellent mixability and can achieve excellent rutting resistance of asphalt pavement regardless of pre-addition or post-addition of polyester, an asphalt composition, an asphalt mixture and a method for producing the same, and a method for paving a road.SOLUTION: An asphalt modifier comprises a constitutional unit derived from an alcohol component (a1) and a constitutional unit derived from a carboxylic acid component (a2). The carboxylic acid component (a2) comprises a crystalline polyester (A) comprising a C2-6 linear saturated aliphatic dicarboxylic acid.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] 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.

[0003] Patent Document 1 discloses an asphalt composition for road paving that has excellent dry strength, water immersion strength, and petroleum immersion strength. The asphalt composition contains asphalt, a specific amount of polyester resin, and aggregate, where the polyester resin is a polyester having structural units derived from an alcohol component including a specific amount of an alkylene oxide adduct of bisphenol A and structural units derived from a carboxylic acid component including a specific amount of one or more acids selected from terephthalic acid and isophthalic acid, and has a specific softening point and hydroxyl value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 125421 Summary of the Invention [Problem to be solved by the invention]

[0005] In the technology for modifying asphalt with polyester disclosed in Patent Document 1 and elsewhere, when aggregate and polyester are mixed in advance and then mixed with asphalt (pre-addition), the effect of modifying asphalt with polyester to improve rutting resistance and the like is sometimes not fully achieved compared to when the asphalt and aggregate are mixed and then the polyester is added (post-addition). However, post-addition of polyester can be difficult in terms of the manufacturing process, and it is desirable to also achieve the effect when the polyester is pre-added, in which aggregate and polyester are mixed in advance and then mixed with asphalt. The present invention relates to an asphalt modifier, an asphalt composition, an asphalt mixture, a method for producing the same, and a road paving method, which have excellent mixability and can achieve excellent rutting resistance in asphalt pavement whether the polyester is added first or later.In this specification, the aspect in which the effect is exhibited whether the polyester is added first or later is referred to as "mixability."

[0006] The present invention relates to the following [1] to [5]. [1] A copolymer containing a structural unit derived from an alcohol component (a1) and a structural unit derived from a carboxylic acid component (a2), The asphalt modifier comprises a crystalline polyester (A) in which the carboxylic acid component (a2) comprises a linear saturated aliphatic dicarboxylic acid having from 2 to 6 carbon atoms. [2] An asphalt composition containing asphalt and 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), and the carboxylic acid component (a2) contains a linear saturated aliphatic dicarboxylic acid having from 2 to 6 carbon atoms, An asphalt composition, wherein the content of the crystalline polyester (A) is 0.1 parts by mass or more and 1.5 parts by mass or less per 100 parts by mass of the asphalt. [3] An asphalt mixture obtained by blending asphalt, aggregate, crystalline polyester (A), and polyester (B), wherein 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), and the carboxylic acid component (a2) contains a linear saturated aliphatic dicarboxylic acid having from 2 to 6 carbon atoms, The asphalt mixture, wherein the polyester (B) contains structural units derived from an alcohol component and structural units derived from a carboxylic acid component, and the content of alkylene oxide adducts of bisphenol A in the alcohol component is 20 mol % or more. [4] A method for producing an asphalt mixture by mixing asphalt, heated aggregate, a crystalline polyester (A), and a polyester (B), wherein 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), and the carboxylic acid component (a2) contains a linear saturated aliphatic dicarboxylic acid having from 2 to 6 carbon atoms, The method for producing an asphalt mixture, wherein 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 adducts of bisphenol A in the alcohol component (b1) is 20 mol% or more. [5] 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. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an asphalt modifier, an asphalt composition, an asphalt mixture and a method for producing the same, and a road paving method, which have excellent mixability and can achieve excellent rutting resistance in asphalt pavement whether the polyester is added first or after the addition. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Asphalt modifier] The asphalt modifier of the present invention comprises a crystalline polyester (A) that contains structural units derived from an alcohol component (a1) and structural units derived from a carboxylic acid component (a2), wherein the carboxylic acid component contains a linear saturated aliphatic dicarboxylic acid having from 2 to 6 carbon atoms.

[0009] The present inventors have discovered that an asphalt modifier containing a specific crystalline polyester (A) has excellent mixability, and can achieve excellent rutting resistance in asphalt pavement whether the polyester is added first or after the asphalt modifier is added. 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. By using saturated aliphatic carboxylic acids, rather than aromatic or alkenyl carboxylic acids, as the carboxylic acid component that makes up the polyester, excessive interaction with the aggregate is suppressed, and even when asphalt is added later, the polyester is more likely to blend into the asphalt, promoting the asphalt modification reaction. Furthermore, by using saturated aliphatic carboxylic acids with a short main chain of 2 to 6 carbon atoms as the carboxylic acid component, crystallization of the polyester in the asphalt is promoted when the asphalt mixture cools, and the filler effect is thought to improve durability and achieve excellent rut resistance.

[0010] 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 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 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 adjusted appropriately by adjusting the types and ratios of raw material monomers, as well as production conditions such as reaction temperature, reaction time, and cooling rate.

[0011] <Crystalline polyester (A)> The crystalline polyester (A) contained in the asphalt modifier of the present invention contains a structural unit derived from an alcohol component (a1) and a structural unit derived from a carboxylic acid component (a2). From the viewpoint of rutting resistance and mixability of the asphalt pavement, the carboxylic acid component (a2) contains a linear saturated aliphatic dicarboxylic acid having from 2 to 6 carbon atoms. The physical properties of the alcohol component (a1), the carboxylic acid component (a2) and the crystalline polyester (A) will be described below.

[0012] (Alcohol component (a1)) Examples of the alcohol component (a1) include aliphatic diols, alicyclic diols, aromatic diols, trihydric or higher polyhydric alcohols, etc. These alcohol components can be used alone or in combination of two or more.

[0013] The aliphatic diol is preferably a linear or branched aliphatic diol having 2 to 12 carbon atoms in the main chain, more preferably a linear or branched aliphatic diol having 2 to 8 carbon atoms in the main chain. The aliphatic diol is preferably a saturated aliphatic diol. Specific examples of aliphatic diols 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.

[0014] Examples of alicyclic diols include hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane), alkylene oxide adducts of hydrogenated bisphenol A, cyclohexanediol, and cyclohexanedimethanol.

[0015] 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 alkylene oxide adducts of bisphenol A represented by the following formula (I):

[0016] [ka]

[0017] [In the formula, OR 1 and R 1 O is alkylene oxide and R 1 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.

[0018] 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.

[0019] The trihydric or higher polyhydric alcohol is preferably a trihydric alcohol, and examples of the trihydric or higher polyhydric alcohol include glycerin, pentaerythritol, trimethylolpropane, and sorbitol.

[0020] The alcohol component (a1) may further contain a monohydric aliphatic alcohol from the viewpoint of adjusting the physical properties. Examples of the monohydric aliphatic alcohol include lauryl alcohol, myristyl alcohol, palmityl alcohol, and stearyl alcohol. These monohydric aliphatic alcohols may be used alone or in combination of two or more.

[0021] From the viewpoint of rutting resistance, the alcohol component (a1) preferably contains a straight-chain aliphatic diol, more preferably an α,ω-straight-chain aliphatic diol. The linear aliphatic diol preferably has 2 or more carbon atoms, more preferably 3 or more carbon atoms, and even more preferably 4 or more carbon atoms, and preferably has 18 or less carbon atoms, more preferably 12 or less carbon atoms, and even more preferably 6 or less carbon atoms. Examples of linear aliphatic diols include ethylene glycol, 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, and 1,20-eicosanediol. Among these, ethylene glycol, 1,4-butanediol, and 1,6-hexanediol are preferred. These linear aliphatic diols can be used alone or in combination of two or more. From the viewpoint of rutting resistance, the content of the linear aliphatic diol is preferably 20 mol% or more, more preferably 40 mol% or more, and even more preferably 60 mol% or more, and is preferably 100 mol% or less, based on 100 mol% of the alcohol component (a1).

[0022] (Carboxylic acid component (a2)) From the viewpoint of rutting resistance and miscibility, the carboxylic acid component (a2) is required to contain a linear saturated aliphatic dicarboxylic acid having from 2 to 6 carbon atoms. Examples of linear saturated aliphatic dicarboxylic acids having from 2 to 6 carbon atoms include oxalic acid, malonic acid, succinic acid, and adipic acid. Of these, succinic acid and adipic acid are preferred. The content of the linear saturated aliphatic dicarboxylic acid having from 2 to 6 carbon atoms in the carboxylic acid component (b2) is preferably 40 mol % or more, more preferably 50 mol % or more, and even more preferably 60 mol % or more, and is 100 mol % or less.

[0023] The carboxylic acid component (a2) may contain another carboxylic acid component different from the linear saturated aliphatic dicarboxylic acid having from 2 to 6 carbon atoms. Examples of the other carboxylic acid component include aliphatic dicarboxylic acids other than linear saturated aliphatic dicarboxylic acids having from 2 to 6 carbon atoms, aromatic dicarboxylic acids, and polycarboxylic acid compounds having from 3 to 6 valences. Other aliphatic dicarboxylic acids include, for example, fumaric acid, adipic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, and eicosanedioic acid. Examples of aromatic dicarboxylic acids include isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, anthracenedicarboxylic acid, and phenanthrenedicarboxylic acid. The trivalent or more and hexavalent polycarboxylic acid is preferably a trivalent carboxylic acid. Examples of the trivalent or more and hexavalent polycarboxylic acid include trimellitic acid, 2,5,7-naphthalenetricarboxylic acid, pyromellitic acid, and acid anhydrides thereof.

[0024] The carboxylic acid component (a2) may further contain a monovalent aliphatic carboxylic acid from the viewpoint of adjusting the physical properties. Examples of the monovalent aliphatic carboxylic acid include monovalent aliphatic carboxylic acids having from 12 to 20 carbon atoms, such as lauric acid, myristic acid, palmitic acid, stearic acid, and alkyl (having from 1 to 3 carbon atoms) esters of these acids. These monovalent aliphatic carboxylic acids may be used alone or in combination of two or more.

[0025] (Molar ratio of structural units derived from carboxylic acid component (a2) to structural units derived from alcohol component (a1)) The equivalent ratio of the carboxyl groups of the carboxylic acid component (a2) to the hydroxyl groups of the alcohol component (a1) (COOH groups / OH groups) is preferably 0.7 or more, more preferably 0.8 or more, and is preferably 1.3 or less, more preferably 1.2 or less.

[0026] (Physical properties of crystalline polyester (A)) From the viewpoints of rutting resistance and mixability, the softening point of the crystalline polyester (A) is preferably 45°C or higher, more preferably 50°C or higher, even more preferably 55°C or higher, and is preferably 150°C or lower, more preferably 140°C or lower, even more preferably 130°C or lower. From the same viewpoint, the melting point of the crystalline polyester (A) is 45°C or higher, preferably 50°C or higher, and 150°C or lower, preferably 140°C or lower, more preferably 130°C or lower. From the viewpoint of enhancing affinity with asphalt, the acid value of the crystalline polyester (A) is preferably 1 mgKOH / g or more, more preferably 3 mgKOH / g or more, even more preferably 4 mgKOH / g or more, and is preferably 70 mgKOH / g or less, more preferably 60 mgKOH / g or less, even more preferably 50 mgKOH / g or less. From the viewpoint of rutting resistance, 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.

[0027] The softening point, melting point, acid value, and weight average molecular weight Mw of the crystalline polyester (A) can be measured by the methods described in the Examples. The softening point, melting point, acid value, and weight average molecular weight Mw can be adjusted by the raw material monomer composition, molecular weight, catalyst amount, or reaction conditions.

[0028] [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 adducts of bisphenol A in the alcohol component (b1) is 20 mol % or more. The physical properties of the alcohol component (b1), the carboxylic acid component (b2), and the polyester (B) will be described below.

[0029] <Alcohol component (b1)> The alcohol component (b1) contains 20 mol % or more of an alkylene oxide adduct of bisphenol A. Examples of the alkylene oxide adduct of bisphenol A include alkylene oxide adducts of bisphenol A represented by the following formula (I).

[0030] [ka]

[0031] [In the formula, OR 1 and R 1 O is alkylene oxide and R 1 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.

[0032] 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. The content of the alkylene oxide adduct of bisphenol A must be 20 mol% or more, preferably 25 mol% or more, more preferably 30 mol% or more, even more preferably 35 mol% or more, and is preferably 100 mol% or less, based on 100 mol% of the alcohol component.

[0033] The alcohol component (b1) may contain other alcohol components different from the alkylene oxide adduct of bisphenol A. Examples of other alcohol components include aromatic diols, aliphatic diols, alicyclic diols, and trihydric or higher polyhydric alcohols other than the alkylene oxide adduct of bisphenol A. These alcohol components may be used alone or in combination of two or more.

[0034] The aliphatic diol is preferably a linear or branched aliphatic diol having 2 to 12 carbon atoms in the main chain, more preferably a linear or branched aliphatic diol having 2 to 8 carbon atoms in the main chain. The aliphatic diol is preferably a saturated aliphatic diol. Specific examples of aliphatic diols 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.

[0035] Examples of alicyclic diols include hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane), alkylene oxide adducts of hydrogenated bisphenol A, cyclohexanediol, and cyclohexanedimethanol.

[0036] The trihydric or higher polyhydric alcohol is preferably a trihydric alcohol, and examples of the trihydric or higher polyhydric alcohol include glycerin, pentaerythritol, trimethylolpropane, and sorbitol.

[0037] The alcohol component may further contain a monohydric aliphatic alcohol from the viewpoint of adjusting physical properties. Examples of the monohydric aliphatic alcohol include lauryl alcohol, myristyl alcohol, palmityl alcohol, and stearyl alcohol. These monohydric aliphatic alcohols may be used alone or in combination of two or more.

[0038] <Carboxylic acid component (b2)> Examples of the carboxylic acid component (b2) include aliphatic dicarboxylic acids, aromatic dicarboxylic acids, and polycarboxylic acids having a valence of 3 to 6. These carboxylic acid components can be used alone or in combination of two or more.

[0039] The aliphatic dicarboxylic acid preferably has 4 or more carbon atoms in the main chain and 10 or less, more preferably 8 or less, and more preferably 6 or less, such as fumaric acid, maleic acid, oxalic acid, malonic acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, succinic acid substituted with an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms, or anhydrides or alkyl esters thereof (e.g., alkyl groups having 1 to 3 carbon atoms). Examples of substituted succinic acids include dodecylsuccinic acid, dodecenylsuccinic acid, and octenylsuccinic acid. Examples of aromatic dicarboxylic acids include phthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, or anhydrides thereof, and alkyl esters thereof (for example, alkyl groups having 1 to 3 carbon atoms). Of the above aromatic dicarboxylic acids, isophthalic acid and terephthalic acid are preferred, with terephthalic acid being more preferred, from the viewpoint of durability of asphalt pavement. The trivalent or more and hexavalent polycarboxylic acid is preferably a trivalent carboxylic acid. Examples of the trivalent or more and hexavalent polycarboxylic acid include trimellitic acid, 2,5,7-naphthalenetricarboxylic acid, pyromellitic acid, and acid anhydrides thereof.

[0040] The carboxylic acid component may further contain a monovalent aliphatic carboxylic acid from the viewpoint of adjusting physical properties. Examples of the monovalent aliphatic carboxylic acid include monovalent aliphatic carboxylic acids having from 12 to 20 carbon atoms, such as lauric acid, myristic acid, palmitic acid, stearic acid, and alkyl (having from 1 to 3 carbon atoms) esters of these acids. These monovalent aliphatic carboxylic acids may be used alone or in combination of two or more.

[0041] From the viewpoint of rutting resistance, the carboxylic acid component (b2) preferably contains at least one selected from terephthalic acid and isophthalic acid. From the viewpoint of rutting resistance, the total content of terephthalic acid and isophthalic acid in the carboxylic acid component is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, and preferably 100 mol% or less.

[0042] <Structural units 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 polyester (B) contains structural units consisting of ethylene glycol and terephthalic acid derived from polyethylene terephthalate, the "structural units derived from alcohol components" contain structural units derived from ethylene glycol derived from polyethylene terephthalate, and the "structural units derived from carboxylic acid components" contain structural units derived from terephthalic acid derived from polyethylene terephthalate.

[0043] <Molar ratio of structural units derived from the carboxylic acid component (b2) to structural units derived from the alcohol component (b1)> The molar ratio of the structural units derived from the carboxylic acid component (b2) to the structural units derived from 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, and is preferably 1.5 or less, more preferably 1.3 or less, even more preferably 1.0 or less.

[0044] <Physical properties of polyester (B)> From the viewpoint of rutting resistance of the asphalt pavement, the softening point or melting 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 preferably 140°C or lower, more preferably 130°C or lower, even more preferably 120°C or lower. The melting point (the temperature of the maximum endothermic peak) is generally observed when the polyester (B) is a crystalline polyester resin. From the viewpoint of rutting resistance of asphalt pavement, the hydroxyl value of the polyester (B) is preferably 10 mgKOH / g or more, more preferably 15 mgKOH / g or more, and preferably 60 mgKOH / g or less, more preferably 50 mgKOH / g or less, even more preferably 40 mgKOH / g or less, and even more preferably 30 mgKOH / g or less. 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, from the viewpoint of the rutting resistance and surface appearance of the asphalt pavement, and is preferably 70,000 or less, more preferably 40,000 or less, even more preferably 25,000 or less. From the viewpoint of durability of the asphalt pavement, the softening point or melting point of the polyester (B) is preferably 60°C or higher, more preferably 70°C or higher, even more preferably 90°C or higher, even more preferably 100°C or higher, and preferably 150°C or lower, more preferably 145°C or lower, even more preferably 140°C or lower. The softening point or melting point, hydroxyl value, and weight average molecular weight Mw of the polyester resin (B) can be measured by the methods described in the Examples. The softening point or melting 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.

[0045] The crystalline polyester (A) and the polyester (B) may be modified to such an extent that their properties are not substantially impaired. Specific examples of modified polyesters include polyesters grafted or blocked with phenol, urethane, epoxy, or the like, by methods described in JP-A Nos. 11-133668, 10-239903, and 8-20636. A preferred modified polyester is a urethane-modified polyester obtained by urethane-extending a polyester with a polyisocyanate compound.

[0046] When the asphalt modifier further contains a polyester (B), from the viewpoint of the rutting resistance of the asphalt pavement, the content ratio of the crystalline polyester (A) and the polyester (B) in the asphalt modifier is, in mass ratio, polyester (B) / crystalline 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.

[0047] (Polyester manufacturing method) 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.

[0048] When the polyester (B) used in the present invention contains structural units derived from ethylene glycol derived from polyethylene terephthalate and structural 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 aesthetics 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, and more preferably 5% or less. The reaction rate refers to the value of the amount of water produced by reaction (moles) / the theoretical amount of water produced (moles) × 100.

[0049] 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). From the viewpoint 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, relative to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component, 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. 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.

[0050] 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.

[0051] [Asphalt composition] The asphalt composition of the present invention comprises asphalt, a crystalline polyester (A), and optionally a polyester (B), and the content of the crystalline polyester (A) is 0.1 to 1.5 parts by mass per 100 parts by mass of the asphalt.

[0052] <Asphalt> Various types of asphalt can be used. Examples include straight asphalt, which is petroleum asphalt for paving, as well as modified asphalt. Modified asphalts include blown asphalt and polymer-modified asphalt modified with polymeric materials such as thermoplastic elastomers and thermoplastic resins. Straight asphalt refers to the residual bitumen 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 oxidizing it by blowing air into 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.

[0053] (thermoplastic elastomer) Examples of the thermoplastic elastomer in asphalt modified with a thermoplastic elastomer include styrene / butadiene block copolymers (hereinafter also referred to as "SB"), styrene / butadiene / styrene block copolymers (hereinafter also referred to as "SBS"), styrene / butadiene random copolymers (hereinafter also referred to as "SBR"), styrene / isoprene block copolymers (hereinafter also referred to as "SI"), styrene / isoprene / styrene block copolymers (hereinafter also referred to as "SIS"), styrene / isoprene random copolymers (hereinafter also referred to as "SIR"), ethylene / vinyl acetate copolymers, ethylene / acrylic acid ester copolymers, styrene / ethylene / butylene / styrene copolymers, styrene / ethylene / propylene / styrene copolymers, polyurethane-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers, isobutylene / isoprene copolymers, polyisoprene, polychloroprene, synthetic rubbers other than those mentioned above, and at least one selected from natural rubber.

[0054] Among these, from the viewpoint of durability 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 durability of the asphalt pavement, the content of 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 15% by mass or less, even more preferably 5% by mass or less.

[0055] <Content of crystalline polyester (A) and polyester (B)> In the asphalt composition of the present invention, the content of the crystalline polyester (A) is, from the viewpoint of durability of the asphalt pavement, 0.1 to 1.5 parts by mass per 100 parts by mass of asphalt, preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, even more preferably 0.4 parts by mass or more, and preferably 1.3 parts by mass or less, more preferably 1.1 parts by mass or less, even more preferably 1 part by mass or less. In the asphalt composition of the present invention, the total content of the crystalline polyester (A) and the polyester (B) contained as needed is, from the viewpoint of the durability of the asphalt pavement, preferably 1 part by mass, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, per 100 parts by mass of asphalt, and is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less.

[0056] 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 particularly suitable for road paving.

[0057] [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).

[0058] The asphalt composition can be obtained by heating and melting asphalt, adding the crystalline polyester (A) and, if necessary, the polyester (B), and stirring and mixing the components until they are uniformly dispersed using a commonly used mixer. Commonly used mixers include homomixers, dissolvers, paddle mixers, ribbon mixers, screw mixers, planetary mixers, vacuum countercurrent mixers, roll mills, and twin-screw extruders.

[0059] The mixing temperature of the asphalt with the crystalline polyester (A) and optionally the polyester (B), from the viewpoint of uniformly dispersing the crystalline polyester (A) and polyester (B) in the asphalt, 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 is 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.

[0060] Furthermore, from the viewpoint of efficiently dispersing the crystalline polyester (A) and polyester (B) uniformly in the asphalt, the mixing time of the asphalt with the crystalline polyester (A) and the polyester (B) is preferably 0.1 hour or longer, more preferably 0.5 hour or longer, even more preferably 1.0 hour or longer, still more preferably 1.5 hour or longer, and is preferably 10 hours or shorter, more preferably 7 hours or shorter, even more preferably 5 hours or shorter, and still more preferably 3 hours or shorter.

[0061] [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.

[0062] <Aggregate> Aggregates can be selected from crushed stone, boulders, gravel, sand, recycled aggregate, ceramics, etc. In addition, both coarse aggregate with a particle size of 2.36 mm or more and fine aggregate with a particle size of less than 2.36 mm can be used. 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.

[0063] 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.

[0064] 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 is preferably 90 / 10 or less, more preferably 80 / 20 or less, even more preferably 70 / 30 or less.

[0065] Suitable examples of blending in asphalt mixtures include the following (1) to (3). (1) For example, 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, 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, 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.

[0066] The porous asphalt can be suitably used for drainage pavement.

[0067] From the viewpoints of rutting resistance and surface aesthetics, 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.

[0068] 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, crystalline polyester (A) and polyester (B). 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 amount.

[0069] 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.

[0070] <Content of crystalline polyester (A) and polyester (B)> 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 rutting resistance of the asphalt pavement, 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.

[0071] The asphalt mixture may further contain other components as required.

[0072] [Asphalt mixture manufacturing method] The asphalt mixture of the present invention can be obtained by blending asphalt, heated aggregate, crystalline polyester (A), and, if necessary, polyester (B). The method for producing the asphalt mixture of the present invention includes a step of mixing asphalt, heated aggregate, crystalline polyester (A), and, if necessary, polyester (B), 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 (iv). (i) adding and mixing asphalt to heated aggregate, and then adding and mixing crystalline polyester (A) and, if necessary, polyester (B); (ii) adding and mixing asphalt, crystalline polyester (A) and, if necessary, polyester (B) simultaneously to the heated aggregate; or (iii) The crystalline polyester (A) and, if necessary, the polyester (B) are added to and mixed with the heated aggregate, and then asphalt is added and mixed. (iv) A mixture of asphalt, crystalline polyester (A) and, if necessary, polyester (B), which has been pre-heat mixed, is added to the heated aggregate and mixed.

[0073] The crystalline polyester (A) and the polyester (B) may be added simultaneously or separately in a sequential order. When they are added separately in a sequential order, the polyester (B) may be added after the crystalline polyester (A), or the crystalline polyester (A) may be added after the polyester (B).

[0074] 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 the 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 modified asphalt.

[0075] 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 modified 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.

[0076] 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.

[0077] [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), with heated 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.

[0078] 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 embodiment 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. [Example]

[0079] 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.

[0080] [Softening point of polyester (Ts)] Using a flow tester "CFT-500D" (Shimadzu Corporation), 1 g of sample was heated at a temperature increase rate of 6°C / min, while applying a load of 1.96 MPa with the plunger, and extruded from a nozzle 1 mm in diameter and 1 mm in length. 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.

[0081] [Crystallinity index] Using a differential scanning calorimeter "Q-100" (TA Instruments Japan Co., Ltd.), 0.02 g of sample was weighed into an aluminum pan and cooled from room temperature (20°C) to 0°C at a rate of 10°C / min. The sample was then maintained at that temperature for 1 minute, and then heated to 180°C at a rate of 10°C / min while measuring the calorific value. The temperature of the peak with the largest peak area among the observed endothermic peaks 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.

[0082] [Polyester melting point (Tm) and glass transition point (Tg)] 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, heated to 200°C, and cooled to 0°C at a rate of 10°C / min. Measurements were then taken while the temperature was increased to 150°C at a rate of 10°C / min. The melting point was determined when the temperature of the peak with the largest peak area was within 20°C of the softening 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.

[0083] [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)).

[0084] Production Examples 1 to 6 and 11 (Polyesters A1 to A6 and C2) The raw material monomers shown in Table 1 or 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 mixture was maintained at 140°C for 6 hours under a nitrogen atmosphere. The temperature was then raised from 140°C to 200°C at a rate of 10°C / hour, after which tin(II) di(2-ethylhexanoate) was added and the mixture was reacted at 200°C for 1 hour, and then at 8.3 kPa for 1 hour to obtain polyesters A1 to A6 and C2. The polyesters A1 to A6 and C2 were crystalline polyesters. The results are shown in Tables 1 and 2.

[0085] [Table 1]

[0086] Manufacturing Example 7 (Polyester B1) The raw material monomers shown in Table 2, alcohol component, terephthalic acid, and polyethylene terephthalate (PET), were placed in a 10-L four-neck flask equipped with a thermometer, stainless steel stirrer, dehydration tube, downflow condenser, and nitrogen inlet tube. The amount of tin(II) di(2-ethylhexanoate) shown in Table 2 was added under a nitrogen atmosphere. The mixture was heated to 235°C over 3 hours in a mantle heater, held 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 alkenyl succinic anhydride was added. The mixture was heated to 210°C over 2 hours, held 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 B1. The alkenyl succinic anhydride used was dodecenyl succinic anhydride (average molecular weight 256). The results are shown in Table 2.

[0087] Manufacturing Example 8 (Polyester B2) The alcohol component and terephthalic acid, among the raw material monomers listed in Table 2, were placed in a 10-L four-neck flask equipped with a thermometer, stainless steel stirrer, dehydration tube, downflow condenser, and nitrogen inlet tube. Under a nitrogen atmosphere, the amounts of tin(II) di(2-ethylhexanoate) and gallic acid listed in Table 2 were added. The mixture was heated to 235°C over 3 hours in a mantle heater, held at 235°C for 5 hours, and then reacted under reduced pressure at 8.0 kPa for 1 hour. After cooling to 180°C, alkenylsuccinic anhydride was added. The mixture was heated to 210°C over 2 hours, held at 210°C for 1 hour, and then reacted under reduced pressure at 8.3 kPa. The reaction was continued until the softening point listed in Table 2 was reached, yielding Polyester B2. The results are shown in Table 2.

[0088] Manufacturing Examples 9 and 12 (Polyester B3 and C3) 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 amount of di(tin 2-ethylhexanoate)(II) shown in Table 2 was added under a nitrogen atmosphere. The mixture was maintained at 180°C for 2 hours and then heated to 210°C over 3 hours. The mixture was reacted at 210°C for 4 hours and then at 8.3 kPa for 1 hour to obtain polyester B3. The results are shown in Table 2.

[0089] Manufacturing Example 10 (Polyester C1) The raw material monomers and 2 g of tertiary butyl catechol 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. 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) was added and reacted at 200°C for 1 hour, followed by another 1 hour at 8.3 kPa to obtain crystalline polyester C1. The results are shown in Table 2.

[0090] [Table 2]

[0091] Example 1 15 kg of aggregate preheated to 180°C (see below for aggregate composition) was placed in an asphalt mixer and mixed at 180°C for 30 seconds. Next, 4.1 g of Polyester A1 obtained in Production Example 1 and 37.0 g of Polyester B1 obtained in Production Example 7 were added simultaneously and mixed for 60 seconds. After that, 0.82 kg of asphalt (PG64-22, manufactured by Associated Asphalt) was added and mixed for an additional 60 seconds to obtain asphalt mixture AS-1. The resulting asphalt mixture AS-1 was stored at 180°C for 1 hour, after which approximately 10.7 kg of the asphalt mixture was filled into a metal formwork (300 x 300 x 50 mm) and compacted at a temperature of 150°C, a load of 0.44 kPa, and 25 rotations using an air-operated roller compactor (manufactured by Iwata Kogyosho Co., Ltd.) to prepare a wheel tracking specimen (T-1a). Separately, an asphalt specimen (T-1b) was prepared in the same manner as described above, except that the order of addition was changed to (1) aggregate-mixed asphalt addition and (2) polyester addition.

[0092] <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 19.0mm: 100% by mass Sieve size 9.50mm: 80.1% by mass Sieve size 4.75mm: 59.4% by mass Sieve size 2.36mm: 43.4% by mass Sieve size 1.18mm: 29.1% by mass Sieve size 600 μm: 18.9 mass% Sieve size 300 μm: 11.7 mass% Sieve size 150μm: 7.6% by mass

[0093] [evaluation] The asphalt specimens (T-1a) and (T-1b) were subjected to the following evaluation tests. By comparing the evaluation results of asphalt specimen (T-1a) (polyester first added) and asphalt specimen (T-1b) (polyester later added), the difference in performance when polyester was mixed with aggregate before asphalt was evaluated. <Amount of rutting> An asphalt specimen was immersed in warm water set to 50°C in a 50°C thermostatic chamber for one hour, and a water-immersion wheel tracking test was performed using a wheel tracking tester (Iwata Kogyosho Co., Ltd., "AI-1100-S") under the following conditions: temperature 50°C, running speed 15 round trips / min, load 175 kgf, and steel wheels (47 mm wide). The amount of rutting was measured by measuring the displacement of the specimen after 1,200 wheel trips. Other measurement conditions followed the "B003 Wheel Tracking Test" described in the "Pavement Survey and Testing Methods Handbook" published by the Japan Road Association. The results are shown in Table 3.

[0094] Examples 2 to 10, Comparative Examples 1 to 5 Asphalt specimens were prepared and the amount of rutting was measured in the same manner as in Example 1, except that the blending was changed to that shown in Table 3. The results are shown in Table 3.

[0095] [Table 3]

[0096] The results in Table 3 show that the present invention provides excellent rutting resistance not only when the polyester is added later but also when it is added first.

Claims

1. Contains a structural unit derived from an alcohol component (a1) and a structural unit derived from a carboxylic acid component (a2), the alcohol component (a1) contains an α,ω-linear aliphatic diol, The asphalt modifier comprises a crystalline polyester (A) in which the carboxylic acid component (a2) contains a linear saturated aliphatic dicarboxylic acid having from 2 to 6 carbon atoms.

2. The asphalt modifier according to claim 1, wherein the content of linear saturated aliphatic dicarboxylic acids having 2 to 6 carbon atoms in the carboxylic acid component (a2) is 40 mol% or more.

3. The asphalt modifier according to claim 1 or 2, wherein the alcohol component (a1) comprises an α,ω-linear aliphatic diol having 2 to 6 carbon atoms.

4. The asphalt modifier according to claim 3, wherein the content of the α,ω-linear aliphatic diol having 2 to 6 carbon atoms in the alcohol component (a1) is 40 mol% or more.

5. The asphalt modifier according to any one of claims 1 to 4, further comprising a polyester (B), The asphalt modifier, wherein 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 an alkylene oxide adduct of bisphenol A in the alcohol component (b1) is 20 mol% or more.

6. The asphalt modifier according to claim 5, wherein the mass ratio of the polyester (B) to the crystalline polyester (A) [polyester (B) / crystalline polyester (A)] is 60 / 40 or more and 99 / 1 or less.

7. The asphalt modifier according to claim 5 or 6, wherein the total content of one or more selected from terephthalic acid and isophthalic acid in the carboxylic acid component (b1) of the polyester (B) is 40 mol% or more.

8. The asphalt modifier according to any one of claims 5 to 7, wherein the hydroxyl value of the polyester (B) is 10 mg KOH / g or more and 60 mg KOH / g or less.

9. An asphalt composition containing asphalt and 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 alcohol component (a1) contains an α,ω-linear aliphatic diol, The carboxylic acid component (a2) contains a linear saturated aliphatic dicarboxylic acid having from 2 to 6 carbon atoms, The asphalt composition, wherein the content of the crystalline polyester (A) is 0.1 parts by mass or more and 1.5 parts by mass or less per 100 parts by mass of the asphalt.

10. 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 alcohol component (a1) contains an α,ω-linear aliphatic diol, The carboxylic acid component (a2) contains a linear saturated aliphatic dicarboxylic acid having from 2 to 6 carbon atoms, 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 adducts of bisphenol A in the alcohol component (b1) is 20 mol% or more.

11. The asphalt mixture according to claim 10, 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 asphalt.

12. 12. The asphalt mixture of claim 10 or 11, wherein the asphalt is a polymer-modified asphalt or a straight asphalt.

13. A method for producing an asphalt mixture by mixing asphalt, heated aggregate, a crystalline polyester (A), and a 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 alcohol component (a1) contains an α,ω-linear aliphatic diol, The carboxylic acid component (a2) contains a linear saturated aliphatic dicarboxylic acid having from 2 to 6 carbon atoms, The polyester (B) contains a structural unit derived from an alcohol component (b1) and a structural unit derived from a carboxylic acid component (b2), The content of alkylene oxide adduct of bisphenol A in the alcohol component (b1) is 20 mol % or more.

14. A road paving method comprising the step of applying the asphalt mixture according to any one of claims 10 to 12 to a road to form an asphalt pavement layer.

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