Asphalt modifier

Abstract

To provide an asphalt modifier and a production method for an asphalt mixture, enabling the production of an asphalt mixture that excels in both adhesion and water resistance and permits stable construction of highly durable asphalt pavement.SOLUTION: An asphalt modifier comprises a thermoplastic elastomer (A) and polyester (B).SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] For the paving of roads, parking lots, freight yards, sidewalks, etc., asphalt paving using an asphalt mixture is carried out because it is relatively easy to lay and the time from the start of paving work to the start of traffic can be shortened. Since this asphalt paving forms a paving surface with an asphalt mixture in which aggregates are bound with asphalt, the paving material has good hardness and durability. However, the asphalt paving surface deteriorates due to long-term use, and it becomes necessary to repair the paving. By repairing the paving, the maintenance cost increases and it has a great impact on automobile traffic.

[0003] Patent Document 1 discloses an asphalt composition excellent in durability after drying, which contains a predetermined amount of asphalt, a thermoplastic elastomer, and a polyester, and the polyester has a predetermined softening point and a predetermined glass transition point. Patent Document 2 discloses an asphalt composition and a method for producing the same, in which the binder properties of a premix type modified asphalt, a high-viscosity modified asphalt, etc. are further improved, and a vinyl aromatic hydrocarbon-conjugated diene block copolymer in a predetermined amount is used. An asphalt modifier obtained by subjecting a product obtained by treating a product with a predetermined amount of heavy oil and a product with a predetermined amount of aromatic hydrocarbon resin to a certain treatment is added to an existing modified asphalt and a high-viscosity modified asphalt.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] It is known that when asphalt is modified with polyester, excellent water resistance of asphalt pavement can be achieved. However, it has been difficult to achieve both excellent water resistance and excellent adhesion. In the process of constructing asphalt pavement, especially the asphalt mixture on the pavement surface and at the ends in contact with the outside air is likely to cool down, resulting in a decrease in adhesion, and aggregate scattering (stone flying) is likely to occur at these parts. Water easily penetrates into the areas where aggregate scattering has occurred, and further aggregate scattering will spread. Even in the asphalt mixture added with polyester, when the paving work does not proceed smoothly and the temperature of the mixture drops significantly, the adhesiveness tends to decrease. Such a lack of adhesion can cause initial defects and a decrease in water resistance of asphalt pavement. Therefore, in order to enable stable construction regardless of temperature drops due to climate, setup, etc. during paving construction, a technology that can impart both excellent water resistance and excellent adhesiveness to asphalt mixtures has been desired.

[0006] In the technology described in Cited Document 1, by applying a polyester having a predetermined softening point, an asphalt pavement with extremely excellent water resistance can be provided. However, during the working process, the temperature of the asphalt mixture may drop significantly, and there is room for improvement regarding the adhesion between asphalt mixtures. In the technology described in Cited Document 2, by applying a composition obtained by treating a vinyl aromatic hydrocarbon-conjugated diene block copolymer with heavy oil and an aromatic hydrocarbon resin, it is possible to improve the tackiness of the asphalt mixture and suppress aggregate scattering. On the other hand, the water resistance as a pavement body is not sufficient, and further improvement is required.

[0007] The present invention relates to an asphalt modifier and a method for producing an asphalt mixture for obtaining an asphalt mixture that is excellent in both adhesiveness and water resistance and enables the construction of a stable and highly durable asphalt pavement.

Means for Solving the Problems

[0008] The present invention relates to the following [1] to [2]. [1] An asphalt modifier containing a thermoplastic elastomer (A) and a polyester (B). [2] A step (1a) of mixing heated aggregates and asphalt to obtain a mixture (M1) containing the aggregates and the asphalt, and A method for producing an asphalt mixture, comprising a step (2) of mixing the mixture (M1), the thermoplastic elastomer (A), and the polyester (B).

Effects of the Invention

[0009] According to the present invention, it is possible to provide an asphalt modifier and a method for producing an asphalt mixture for obtaining an asphalt mixture that is excellent in both adhesiveness and water resistance and enables the construction of a stable and highly durable asphalt pavement.

Modes for Carrying Out the Invention

[0010] [Asphalt Modifier] The asphalt modifier of the present invention contains a thermoplastic elastomer (A) and a polyester (B).

[0011] The inventors have found that by incorporating an asphalt modifier, which is a mixture of a thermoplastic elastomer (A) and a polyester (B), into an asphalt mixture, an asphalt pavement excellent in both adhesiveness and water resistance can be formed. In this specification, the adhesiveness of the asphalt pavement means the strength of adhesion between coarse aggregates in the asphalt mixture, the strength of adhesion between coarse aggregates and fine aggregates, and the strength of adhesion between fine aggregates, and particularly means the strength of adhesion between the above materials when the temperature of the combined materials drops to 130°C or lower during the construction work. In addition, the water resistance of asphalt pavement refers to the resistance to pavement defects such as graveling and potholes, which occur due to the peeling of the asphalt coating from the aggregates caused by the erosion of moisture such as rainwater.

[0012] Although the detailed mechanism by which the effects of the present invention are obtained is unclear, part of it can be considered as follows. In the asphalt modifier, which is a mixture of a thermoplastic elastomer and polyester, it is considered that the thermoplastic elastomer and polyester interact with each other in advance to form a complex thereof, and then the complex of the thermoplastic elastomer and polyester modifies the asphalt. Therefore, the asphalt modifier, which is a mixture of a thermoplastic elastomer and polyester, is considered to have the characteristics of both the thermoplastic elastomer and polyester. Specifically, it is considered that the flexibility at low temperatures of the thermoplastic elastomer and the high affinity with aggregates of polyester can be synergistically exerted. As a result, it is considered that the asphalt mixture has dramatic effects of improving adhesiveness and water resistance. When polyester is added after mixing asphalt and a thermoplastic elastomer, and when an asphalt modifier, which is a mixture of a thermoplastic elastomer and polyester, is not used, such as when using asphalt to which a thermoplastic elastomer such as polymer-modified asphalt has been previously added, the thermoplastic elastomer and asphalt are already in a state of highly interacting with each other, and the polyester added later does not sufficiently interact with the thermoplastic elastomer, and it is considered that the above effects are not exhibited.

[0013] In addition, usually, a thermoplastic elastomer has high viscoelasticity and is difficult to dissolve in asphalt alone. Therefore, pretreatment is required to uniformly disperse the thermoplastic elastomer in the asphalt mixture in a short time. However, in the present invention, the complex of the thermoplastic elastomer and polyester also has the property of polyester with a high heating and melting rate, so it is considered that the modifier is uniformly dispersed in the asphalt mixture in a short time.

[0014] <Thermoplastic elastomer (A)> The thermoplastic elastomer (A) may be either a block copolymer or a random copolymer.

[0015] The block copolymer is a copolymer having two types of polymer blocks, a block a which is a hard segment and a block b which is a soft segment. As the block a, a block mainly composed of structural units derived from vinyl aromatic compounds is preferable. Here, "mainly composed of" means that the content of the structural units derived from vinyl aromatic compounds in the block A is preferably 90% by mass or more, more preferably 95% by mass or more, and still more preferably 100% by mass based on all the structural units of the block a. Examples of the vinyl aromatic compound include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, p-t-butylstyrene, 2,4-dimethylstyrene, vinylnaphthalene, vinylanthracene, etc. Among these, styrene is preferable. The vinyl aromatic hydrocarbons can be used singly or in combination of two or more.

[0016] As the block b, it is preferable that the structural units derived from conjugated diene compounds be the main component. Here, "mainly composed of" means that the content of the structural units derived from conjugated diene compounds in the block b is preferably 90% by mass or more, more preferably 95% by mass or more based on all the structural units of the block b. Examples of the conjugated diene compound include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 1,3-hexadiene, etc. Among these, 1,3-butadiene and isoprene are preferable, and 1,3-butadiene is more preferable. The conjugated diene compounds can be used singly or in combination of two or more.

[0017] The content of the structural units contained in the block copolymer can be identified by using nuclear magnetic resonance (NMR) or infrared spectroscopic analysis (IR), and the ratio can be determined from the peak integration value of NMR.

[0018] Specific examples of the thermoplastic elastomer include styrene / butadiene block copolymer, styrene / butadiene / styrene block copolymer, styrene / butadiene random copolymer, styrene / isoprene block copolymer, styrene / isoprene / styrene block copolymer, styrene / isoprene random copolymer, and the like. Among them, the thermoplastic elastomer is preferably a vinyl aromatic compound-conjugated diene block copolymer. Examples of the vinyl aromatic compound-conjugated diene block copolymer include a triblock copolymer of the above block a and the above block b in an a-b-a type, and a diblock copolymer of the above block a and the above block b in an a-b type. Among them, a triblock copolymer is preferred.

[0019] Examples of the vinyl aromatic compound-conjugated diene block copolymer include styrene / butadiene block copolymer, styrene / butadiene / styrene block copolymer, styrene / isoprene block copolymer, styrene / isoprene / styrene block copolymer, and the like, and preferably a styrene / butadiene / styrene block copolymer.

[0020] <Polyester (B)> The asphalt modifier of the present invention contains polyester (B). Polyester (B) is a polycondensate of an alcohol component and a carboxylic acid component, containing a structural unit derived from the alcohol component and a structural unit derived from the carboxylic acid component. The "structural unit derived from the alcohol component" means a structure obtained by removing a hydrogen atom from the hydroxy group of the alcohol component, and the "structural unit derived from the carboxylic acid component" means a structure obtained by removing a hydroxy group from the carboxy group of the carboxylic acid component. The term "carboxylic acid component" 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, the alkyl group has 1 to 3 carbon atoms). When the carboxylic acid component is an alkyl ester of a carboxylic acid, the number of carbon atoms of the carboxylic acid does not include the number of carbon atoms of the alkyl group that is the alcohol residue of the ester. Examples of the polyester (B) include an amorphous polyester resin and a crystalline polyester resin, and an amorphous polyester resin is preferred. Whether the resin is crystalline or amorphous is determined by the crystallinity index. The crystallinity index is defined as the ratio of the softening point of the resin to the maximum peak temperature of endotherm in the measurement method described in the examples below (softening point (°C) / maximum peak temperature of endotherm (°C)). A crystalline resin is one with a crystallinity index of 0.6 or more and 1.4 or less. An amorphous resin is one in which no endothermic peak is observed, or if observed, the crystallinity index is less than 0.6 or more than 1.4. Hereinafter, the alcohol component and the carboxylic acid component will be described.

[0021] (Alcohol component) Examples of the alcohol component include aliphatic diols, alicyclic diols, aromatic diols, polyhydric alcohols having a trivalent or higher valence, and the like. These alcohol components can be used alone or in combination of two or more.

[0022] The aliphatic diol is preferably a linear or branched aliphatic diol having 2 to 12 carbon atoms in the main chain, and more preferably a linear or branched aliphatic diol having 2 to 8 carbon atoms in the main chain. Also, the aliphatic diol is preferably a saturated aliphatic diol. Specific examples of the aliphatic diol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,10-decanediol, and 1,12-dodecanediol.

[0023] Examples of the alicyclic diol include hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane), an alkylene oxide adduct of hydrogenated bisphenol A, cyclohexanediol, and cyclohexanedimethanol.

[0024] Examples of the aromatic diol include bisphenol A [2,2-bis(4-hydroxyphenyl)propane] and an alkylene oxide adduct of bisphenol A. Examples of the alkylene oxide adduct of bisphenol A include the alkylene oxide adduct of bisphenol A represented by the following formula (I).

[0025] [Chemical formula]

[0026] [In the formula, OR 1 and R 1 O is an alkylene oxide, R 1 is an alkylene group having 2 or 3 carbon atoms, x and y represent positive numbers indicating the average number of moles of alkylene oxide added, the sum of x and y is preferably 1 or more, more preferably 1.5 or more, and preferably 16 or less, more preferably 8 or less, still more preferably 4 or less. ]

[0027] Examples of the alkylene oxide adduct of bisphenol A represented by the formula (I) include a propylene oxide adduct of bisphenol A and an ethylene oxide adduct of bisphenol A. These alkylene oxide adducts of bisphenol A can be used alone or in combination of two or more.

[0028] The polyhydric alcohol having a valence of 3 or more is preferably a trihydric alcohol. Examples of the polyhydric alcohol having a valence of 3 or more include glycerin, pentaerythritol, trimethylolpropane, and sorbitol.

[0029] From the perspective of physical property adjustment, the alcohol component can further contain a monohydric aliphatic alcohol. Examples of the monohydric aliphatic alcohol include lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, etc. These monohydric aliphatic alcohols can be used alone or in combination of two or more.

[0030] (Carboxylic acid component) Examples of the carboxylic acid component include aliphatic dicarboxylic acids, aromatic dicarboxylic acids, and polycarboxylic acids with a valence of 3 or more and 6 or less. These carboxylic acid components can be used alone or in combination of two or more.

[0031] Examples of the aliphatic dicarboxylic acid include aliphatic dicarboxylic acids having a main chain carbon number of preferably 4 or more, and preferably 10 or less, more preferably 8 or less, and even 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 thereof, and alkyl esters thereof (for example, the alkyl group has 1 to 3 carbon atoms). Examples of the substituted succinic acid include dodecyl succinic acid, dodecenyl succinic acid, and octenyl succinic acid.

[0032] Examples of the aromatic dicarboxylic acid include phthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, or anhydrides thereof, and alkyl esters thereof (for example, the alkyl group has 1 to 3 carbon atoms). Among the above aromatic dicarboxylic acids, from the perspective of the durability of asphalt pavement, isophthalic acid and terephthalic acid are preferred, and terephthalic acid is more preferred.

[0033] The polyvalent carboxylic acid having a valence of 3 or more and 6 or less is preferably a trivalent carboxylic acid. Examples of the polyvalent carboxylic acid having a valence of 3 or more and 6 or less include trimellitic acid, 2,5,7-naphthalenetricarboxylic acid, pyromellitic acid, or acid anhydrides thereof.

[0034] From the viewpoint of physical property adjustment, the carboxylic acid component may further contain a monovalent aliphatic carboxylic acid. Examples of the monovalent aliphatic carboxylic acid include monovalent aliphatic carboxylic acids having 12 to 20 carbon atoms such as lauric acid, myristic acid, palmitic acid, stearic acid, and alkyl (having 1 to 3 carbon atoms) esters of these acids. These monovalent aliphatic carboxylic acids can be used alone or in combination of two or more.

[0035] (Constituent unit derived from polyethylene terephthalate) Polyester (B) can contain a constituent unit derived from ethylene glycol and a constituent unit derived from terephthalic acid, which are derived from polyethylene terephthalate. Polyethylene terephthalate may contain a small amount of components such as butanediol and isophthalic acid in addition to the constituent units derived from ethylene glycol and terephthalic acid. Polyethylene terephthalate is preferably recycled polyethylene terephthalate. When polyester (B) contains a constituent unit composed of ethylene glycol and terephthalic acid derived from polyethylene terephthalate, the "constituent unit derived from the alcohol component" includes the constituent unit derived from ethylene glycol derived from polyethylene terephthalate, and the "constituent unit derived from the carboxylic acid component" includes the constituent unit derived from terephthalic acid derived from polyethylene terephthalate.

[0036] (Preferred embodiment of polyester (B)) In a preferred embodiment of the polyester resin, from the viewpoint of further improving adhesiveness, the alcohol component preferably contains an alkylene oxide adduct of bisphenol A, and its content is preferably 20 mol% or more, more preferably 40 mol% or more, and preferably 100 mol% or less in 100 mol% of the alcohol component.

[0037] (Molar ratio of the structural unit derived from the carboxylic acid component to the structural unit derived from the alcohol component) The molar ratio of the structural unit derived from the carboxylic acid component to the structural unit derived from the alcohol component [carboxylic acid component / alcohol component] is preferably 0.6 or more, more preferably 0.7 or more, still more preferably 0.8 or more, and is preferably 1.5 or less, more preferably 1.3 or less, still more preferably 1.1 or less.

[0038] Polyester (B) may be a polyester modified to such an extent that its properties are not substantially impaired. Specifically, examples of the modified polyester include polyesters grafted or blocked with phenol, urethane, epoxy, etc. by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, etc. Preferred modified polyester resins include urethane-modified polyesters obtained by extending a polyester with a polyisocyanate compound.

[0039] (Physical properties of polyester (B)) From the viewpoint of improving the durability of the asphalt mixture, the softening point of polyester (B) is preferably 50°C or higher, more preferably 70°C or higher, still more preferably 90°C or higher, and is preferably 160°C or lower, more preferably 140°C or lower, still more preferably 120°C or lower.

[0040] From the same viewpoint as above, the glass transition point of polyester (B) is preferably 40°C or higher, more preferably 45°C or higher, still more preferably 50°C or higher, and is preferably 100°C or lower, more preferably 90°C or lower, still more preferably 80°C or lower.

[0041] From the same perspective as above, the melt viscosity of polyester (B) at 180°C is preferably 0.5 Pa·s or more, more preferably 1.0 Pa·s or more, still more preferably 1.5 Pa·s or more, and preferably 10 Pa·s or less, more preferably 8.0 Pa·s or less, still more preferably 6.0 Pa·s or less.

[0042] The softening point, glass transition point, melt viscosity at 180°C, acid value, and hydroxyl value of polyester (B) can be measured by the methods described in the examples. The softening point, glass transition point, melt viscosity at 180°C, acid value, and hydroxyl value can be adjusted by the raw material monomer composition, molecular weight, catalyst amount, or reaction conditions.

[0043] (Method for producing polyester (B)) The method for producing polyester (B) constituting the asphalt modifier of the present invention is not particularly limited, and for example, it can be produced by polycondensing the above-described alcohol component and carboxylic acid component. The temperature of the polycondensation reaction is not particularly limited, but from the perspective of adjusting the reactivity, it is preferably 160°C or higher and 260°C or lower.

[0044] When the polyester (B) used in the present invention contains a structural unit derived from ethylene glycol derived from polyethylene terephthalate and a structural unit derived from terephthalic acid derived from polyethylene terephthalate, the abundance of polyethylene terephthalate in the raw material is preferably 5% by mass or more, more preferably 15% by mass or more, still more preferably 25% by mass or more, and preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less in the total amount of polyethylene terephthalate, alcohol component, and carboxylic acid component. By adding polyethylene terephthalate during the polycondensation reaction of the alcohol component and the carboxylic acid component, a transesterification reaction occurs, and a polyester in which the structural units of polyethylene terephthalate are incorporated into the structural units derived from the alcohol component and the structural units derived from the carboxylic acid component can be obtained. Polyethylene terephthalate may be present from the start of the polycondensation reaction or added to the reaction system during the polycondensation reaction. From the perspective of the rutting resistance of asphalt pavement, the addition timing of polyethylene terephthalate is preferably at a stage where the reaction rate between the alcohol component and the carboxylic acid component is 10% or less, and more preferably 5% or less. The reaction rate refers to the value of (moles of generated reaction water / moles of theoretically generated water) × 100.

[0045] For the polycondensation reaction, from the perspective of reaction rate, a tin(II) compound having no Sn-C bond, such as tin(II) bis(2-ethylhexanoate), can be used as an esterification catalyst. The usage amount of the esterification catalyst is preferably 0.01 part by mass or more, more preferably 0.1 part by mass or more, still more preferably 0.2 part by mass or more, and preferably 1.5 parts by mass or less, more preferably 0.6 part by mass or less, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. For the polycondensation reaction, in addition to the esterification catalyst, from the perspective of reaction rate, a pyrogallol compound such as gallic acid can be used as a co-catalyst. The usage amount of the co-catalyst is preferably 0.001 part by mass or more, more preferably 0.005 part by mass or more, still more preferably 0.01 part by mass or more, and preferably 0.15 part by mass or less, more preferably 0.10 part by mass or less, still more preferably 0.05 part by mass or less, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. For the polycondensation reaction, in addition to the catalyst, from the perspective of reaction rate, a polymerization inhibitor such as tertiary butyl catechol can be used in an amount of 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, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

[0046] (Asphalt modifier) The asphalt modifier contains a thermoplastic elastomer (A) and a polyester (B). That is, the asphalt modifier is a mixture containing a thermoplastic elastomer (A) and a polyester (B). An asphalt modifier is used by adding it to an asphalt mixture to improve the physical properties of the resulting asphalt pavement. Therefore, the asphalt modifier is an additive for use in an asphalt mixture.

[0047] In a first aspect, the asphalt modifier of the present invention is a solid mixture. The solid mixture is, for example, a mixture of solids such as powdery solids, crumbly solids, and pelletized solids. In the solid mixture, the thermoplastic elastomer (A) and the polyester (B) are uniformly mixed. As used herein, "powder" means that the average particle size is preferably 1 μm or more, more preferably 10 μm or more, still more preferably 100 μm or more, and 5 mm or less, more preferably 3 mm or less, still more preferably 1 mm or less. Examples of the method for obtaining a powdery solid include a method of pulverizing a non-powdery solid into a powder. As used herein, "crumb" means that the average particle size is preferably 5 mm or more, more preferably 6 mm or more, still more preferably 7 mm or more, and 30 mm or less, more preferably 20 mm or less, still more preferably 10 mm or less. As used herein, "pellet" means that the average particle size is preferably 5 mm or more, more preferably 6 mm or more, still more preferably 7 mm or more, and 30 mm or less, more preferably 20 mm or less, still more preferably 10 mm or less. The average particle size can be measured by sieving. Here, the average particle size means the average particle size at a cumulative weight of 50%. The solid mixture can be produced, for example, by mixing the thermoplastic elastomer (A) and the polyester (B) using a known powder stirring device such as a Henschel mixer.

[0048] In a second aspect, the asphalt modifier of the present invention is a molten mixture. The molten mixture can be produced, for example, by melt-kneading the thermoplastic elastomer (A) and the polyester (B) at a predetermined temperature. The molten mixture can be produced by mixing, for example, a thermoplastic elastomer (A) and a polyester (B) using a known powder stirring device such as a Henschel mixer. The temperature of melt-kneading is preferably 100 °C or higher, more preferably 110 °C or higher, still more preferably 120 °C or higher, and is preferably 200 °C or lower, more preferably 190 °C or lower. The melt-kneading can be carried out using a known kneader such as a closed kneader, a single-screw extruder, a twin-screw extruder, or an open roll kneader.

[0049] (Content of the thermoplastic elastomer (A)) In the asphalt modifier of the present invention, from the viewpoint of improving the adhesiveness of the asphalt mixture, the content of the thermoplastic elastomer (A) with respect to the total content of 100% by mass of the thermoplastic elastomer (A) and the polyester (B) is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and is preferably 40% by mass or less, more preferably 35% by mass or less, still more preferably 30% by mass or less.

[0050] The asphalt modifier of the present invention can be used, for example, by mixing it with asphalt to obtain an asphalt composition. After adding heated aggregates to the obtained asphalt composition to form an asphalt mixture, it can be used for paving. The asphalt modifier of the present invention can be suitably used as an asphalt modifier for blending into an asphalt mixture containing aggregates.

[0051] [Method for producing an asphalt mixture] The method for producing an asphalt mixture of the present invention includes a step (1a) of mixing heated aggregates and asphalt to obtain a mixture (M1) containing the aggregates and the asphalt, and a step (2) of mixing the mixture (M1), the thermoplastic elastomer (A), and the polyester (B).

[0052] <Step 1a> Step 1a is a step of mixing heated aggregates and asphalt to obtain a mixture (M1) containing the aggregates and the asphalt.

[0053] (Asphalt) As the asphalt, various asphalts can be used. For example, in addition to straight asphalt which is paving petroleum asphalt, modified asphalt can be mentioned. Examples of the modified asphalt include blown asphalt; polymer-modified asphalt modified with polymer materials such as thermoplastic elastomers and thermoplastic resins. Straight asphalt is a residual asphalt substance obtained by subjecting crude oil to an atmospheric distillation unit, a vacuum distillation unit, etc. Also, blown asphalt means asphalt obtained by heating a mixture of straight asphalt and heavy oil and then blowing air into it for oxidation. The asphalt is preferably selected from straight asphalt and polymer-modified asphalt, more preferably polymer-modified asphalt from the viewpoint of the durability of asphalt pavement, and more preferably straight asphalt from the viewpoint of versatility. As the polymer-modified asphalt, asphalt modified with a thermoplastic elastomer is more preferable. The modified asphalt is preferably polymer-modified asphalt, and more preferably polymer-modified asphalt modified with a thermoplastic elastomer.

[0054] · Thermoplastic elastomer Examples of the thermoplastic elastomer in the polymer-modified asphalt modified with a thermoplastic elastomer include at least one selected from styrene / butadiene block copolymers, styrene / butadiene / styrene block copolymers, styrene / butadiene random copolymers, styrene / isoprene block copolymers, styrene / isoprene / styrene block copolymers, styrene / isoprene random copolymers, ethylene / vinyl acetate copolymers, ethylene / acrylic ester copolymers, styrene / ethylene / butylene / styrene copolymers, styrene / ethylene / propylene / styrene copolymers, polyurethane-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers, isobutylene / isoprene copolymers, polyisoprene, polychloroprene, synthetic rubbers other than the above, and natural rubbers. The thermoplastic elastomer in the modified asphalt is preferably at least one selected from styrene / butadiene block copolymers, styrene / butadiene / styrene block copolymers, styrene / butadiene random copolymers, styrene / isoprene block copolymers, styrene / isoprene / styrene block copolymers, styrene / isoprene random copolymers, ethylene / vinyl acetate copolymers, and ethylene / acrylic ester copolymers. Among these, from the viewpoint of the durability of asphalt pavement, the thermoplastic elastomer 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, and ethylene / acrylic ester copolymers; more preferably at least one selected from styrene / butadiene block copolymers, styrene / butadiene / styrene block copolymers, styrene / butadiene random copolymers, styrene / isoprene block copolymers, and styrene / isoprene random copolymers; and still more preferably at least one selected from styrene / butadiene random copolymers and styrene / butadiene / styrene block copolymers. From the viewpoints of the durability and surface appearance of the asphalt pavement, 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, still more preferably 1% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less.

[0055] Incidentally, the thermoplastic elastomer in the polymer-modified asphalt may be the same as or different from the above thermoplastic elastomer (A).

[0056] (Aggregate) As the aggregate, for example, crushed stone, cobblestone, gravel, sand, ceramics, etc. can be arbitrarily selected and used. Further, as the aggregate, coarse aggregate having a particle size of 2.36 mm or more, fine aggregate having a particle size of 0.075 mm or more and less than 2.36 mm, and filler having a particle size of less than 0.075 mm can be used. Examples of the coarse aggregate include crushed stone having a particle size range of 2.36 mm or more and less than 4.75 mm, crushed stone having a particle size range of 4.75 mm or more and less than 12.5 mm, crushed stone having a particle size range of 12.5 mm or more and less than 19 mm, and crushed stone having a particle size range of 19 mm or more and less than 31.5 mm. Examples of the fine aggregate include river sand, hill sand, mountain sand, sea sand, crushed sand, fine sand, screenings, crushed stone dust, silica sand, artificial sand, glass cullet, and foundry sand. The particle sizes of the coarse aggregate and the fine aggregate are values based on the sieving test method defined in JIS A5001:2008.

[0057] Examples of the filler include sand, fly ash, calcium carbonate powder such as limestone powder, and slaked lime. Among these, calcium carbonate powder is preferable from the viewpoint of improving the strength of the asphalt pavement. From the viewpoint of improving the strength of the asphalt pavement, the average particle size of the filler is preferably 0.001 mm or more, and preferably 0.05 mm or less, more preferably 0.03 mm or less, still more preferably 0.02 mm or less. Here, the average particle size means the average particle size (D at 50% volume cumulative 50) and can be measured by a laser diffraction particle size distribution measuring device.

[0058] As the aggregate, it is preferable to use coarse aggregate and fine aggregate in combination. In this case, from the viewpoint of the durability of asphalt pavement, the mass ratio of the coarse aggregate to the fine aggregate is preferably 10 / 90 or more, more preferably 15 / 85 or more, still more preferably 20 / 80 or more, and preferably 90 / 10 or less, more preferably 80 / 20 or less, still more preferably 70 / 30 or less.

[0059] Preferable blending examples of the coarse aggregate and the fine aggregate in the asphalt mixture include the following (1) to (3). (1) For example, fine-grained asphalt containing 30% by volume or more and less than 45% by volume of coarse aggregate, 30% by volume or more and 50% by volume or less of fine aggregate, and 5% by volume or more and 10% by volume or less of asphalt composition. (2) For example, dense-grained asphalt containing 45% by volume or more and less than 70% by volume of coarse aggregate, 20% by volume or more and 45% by volume or less of fine aggregate, and 3% by volume or more and 10% by volume or less of 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 asphalt composition.

[0060] Regarding the blending ratio of asphalt in the asphalt mixture containing aggregate and asphalt, usually, it is used according to the optimum asphalt amount obtained from the "Mix Design of Asphalt Composition" described in the "Pavement Design and Construction Guidelines" issued by the Japan Road Association, a public interest incorporated association.

[0061] From the viewpoint of pavement durability, the content of asphalt in the mixture (M1) is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 4% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, still more preferably 10% by mass or less.

[0062] The mixing in Step 1a is obtained by stirring and mixing with a commonly used mixer until each component is uniformly dispersed. Examples of commonly used mixers include a homomixer, a dissolver, a paddle mixer, a ribbon mixer, a screw mixer, a planetary mixer, a vacuum countercurrent mixer, a roll mill, a twin-screw extruder, and the like. In Step 1a, from the viewpoint of mixability, the temperature of the heated aggregate is preferably 130°C or higher, more preferably 150°C or higher, still more preferably 170°C or higher, and from the viewpoint of preventing thermal degradation of asphalt, it is preferably 230°C or lower, more preferably 210°C or lower, still more preferably 200°C or lower. From the viewpoint of mixability, the mixing temperature of the aggregate and asphalt is preferably 130°C or higher, more preferably 150°C or higher, still more preferably 170°C or higher, and from the viewpoint of preventing thermal degradation of asphalt, it is preferably 230°C or lower, more preferably 210°C or lower, still more preferably 200°C or lower. The mixing time of the aggregate and asphalt is not particularly limited, preferably 10 seconds or longer, more preferably 20 seconds or longer, still more preferably 30 seconds or longer, and the upper limit of the time is not particularly limited, preferably about 5 minutes.

[0063] <Step 2> Step 2 is a step of mixing the mixture (M1), the thermoplastic elastomer (A), and the polyester (B). As the thermoplastic elastomer (A) and the polyester (B), those constituting the above asphalt modifier are respectively used, and preferably the above asphalt modifier is used as the thermoplastic elastomer (A) and the polyester (B). In Step 2, from the viewpoint of improving the adhesiveness of the asphalt mixture, the blending amount of the thermoplastic elastomer (A) with respect to 100% by mass of the total blending amounts of the thermoplastic elastomer (A) and the polyester (B) is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and preferably 40% by mass or less, more preferably 35% by mass or less, still more preferably 30% by mass or less. In Step 2, from the viewpoint of improving the water resistance of the asphalt pavement, the total blending amount of the thermoplastic elastomer (A) and the polyester (B) is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, based on 100 parts by mass of the asphalt, and is preferably 35 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 25 parts by mass or less.

[0064] The mixing in Step 2 can be obtained by stirring and mixing with a commonly used mixer until each component is uniformly dispersed. Examples of commonly used mixers include a homomixer, a dissolver, a paddle mixer, a ribbon mixer, a screw mixer, a planetary mixer, a vacuum countercurrent mixer, a roll mill, a twin-screw extruder, and the like. In Step 2, from the viewpoint of the durability of the asphalt pavement, the mixing temperature is preferably 130°C or higher, more preferably 150°C or higher, still more preferably 170°C or higher, and from the viewpoint of preventing thermal degradation of the asphalt, it is preferably 230°C or lower, more preferably 210°C or lower, still more preferably 200°C or lower. The mixing time of the aggregate, calcium carbonate powder, asphalt, thermoplastic elastomer, and polyester is not particularly limited, and is preferably 20 seconds or longer, more preferably 40 seconds or longer, still more preferably 1 minute or longer. The upper limit of the time is not particularly limited and is preferably about 5 minutes.

[0065] <Step 1b> The method for producing the asphalt mixture of the present invention preferably further includes Step 1b of mixing the thermoplastic elastomer (A) and the polyester (B) to obtain a mixture (M2). The mixture (M2) is the aforementioned asphalt modifier. When the mixture (M2) is a powder mixture, for example, it can be produced by mixing the thermoplastic elastomer (A) and the polyester (B) using a known powder stirring device such as a Henschel mixer. When the mixture (M2) is a molten mixture, for example, it can be produced by mixing a thermoplastic elastomer (A) and a polyester (B) using a known powder stirring device such as a Henschel mixer. The temperature of the melt-kneading is preferably 100 °C or higher, more preferably 110 °C or higher, still more preferably 120 °C or higher, and is preferably 200 °C or lower, more preferably 190 °C or lower. The melt-kneading can be carried out using a known kneader such as a closed kneader, a single-screw extruder, a twin-screw extruder, or an open roll kneader.

[0066] When the method for producing the asphalt mixture of the present invention includes step 1b, the step (2) is a step (2') of mixing the mixture (M1) and the mixture (M2).

[0067] [Paving method] The asphalt mixture of the present invention is suitable for paving and is used for paving. The paving method includes a step of constructing the above-mentioned asphalt mixture on a paving target to form an asphalt paving material layer. Examples of the paving target include roads and parking lots. Specifically, the paving method includes a step (step 1) of obtaining an asphalt mixture by mixing asphalt, the above-mentioned polyesters (A) and (B), and aggregates, and a step (step 2) of constructing the asphalt mixture obtained in step 1 on a paving target to form an asphalt paving material layer. The asphalt paving material layer is usually a base layer or a surface layer, and from the viewpoint of exerting the effect of durability, it is preferably a surface layer.

[0068] From the viewpoint of resistance to fluidity, the thickness of the asphalt paving material layer is preferably 3 cm or more, more preferably 4 cm or more, still more preferably 4.5 cm or more, and is preferably 7 cm or less, more preferably 6 cm or less, still more preferably 5.5 cm or less. In another aspect of the present invention, the asphalt paving material layer can be a thin-layer paving, and the thickness of the surface layer is preferably 1 cm or more, more preferably 1.5 cm or more, still more preferably 2 cm or more, and is preferably 4 cm or less, more preferably 3.5 cm or less, still more preferably 3 cm or less. The asphalt mixture may be compacted by a known construction machine formation in a similar manner. When used as a heated asphalt mixture, the compaction temperature is preferably 100 °C or higher, more preferably 120 °C or higher, still more preferably 130 °C or higher, and preferably 200 °C or lower, more preferably 180 °C or lower, from the viewpoints of the flow resistance and water resistance of the asphalt pavement.

Examples

[0069] Regarding various physical properties, measurement and evaluation were performed by the following methods. In the following examples and comparative examples, unless otherwise specified, parts and % are based on mass.

[0070] 〔Softening point (Ts) of resin〕 Using a flow tester "CFT-500D" (manufactured by Shimadzu Corporation), while heating 1 g of the sample at a heating rate of 6 °C / min, a load of 1.96 MPa was applied by a plunger and extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. The plunger drop amount of the flow tester was plotted against the temperature, and the temperature at which half of the sample flowed out was taken as the softening point.

[0071] 〔Melting point (Tm) and glass transition point (Tg) of resin〕 Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan Co., Ltd.), 0.01 - 0.02 g of the sample was weighed into an aluminum pan, heated to 200 °C, and then cooled from that temperature to 0 °C at a cooling rate of 10 °C / min. Next, it was measured while heating from 0 °C to 150 °C at a heating rate of 10 °C / min. The temperature at the intersection of the extension line of the baseline below the maximum peak temperature of the endotherm and the tangent line showing the maximum slope from the rising part of the peak to the apex of the peak was taken as the glass transition point.

[0072] 〔Measurement of the melt viscosity of polyester〕 The melt viscosity of the polyester was measured at a test temperature of 180 °C in accordance with "Japan Petroleum Institute Standard JPI-5s-54-99: Asphalt - Viscosity test method by rotational viscometer". Specifically, 50 g of polyester was weighed into a measuring cell, and a molten sample heated in an oven for 30 minutes was obtained. Then, it was stirred at 180°C for 2 hours. The measurement was carried out using a B-type viscometer (manufactured by Brookfield, "DV1 VISCOMETER"; spindle: SC4-27, chamber: SC4-13R) under the condition of 50 rpm (upper limit value 5,000 mPa·s). However, for samples exceeding the upper limit, the measurement was carried out under the condition of 5 rpm (upper limit value 50,000 mPa·s).

[0073] [Measurement of Particle Size of Polyester Resin] 300 g of the modifier was subjected to a dry sieving test in accordance with JIS Z 8815 using a test sieve with a diameter of 200 mm and the following mesh openings, and the average particle size was measured. Mesh openings of 4000 μm, 2000 μm, 1000 μm, 850 μm, 500 μm, 355 μm, 250 μm, 150 μm, and 106 μm were used.

[0074] Production Example 1 (Polyester P1) Among the raw material monomers shown in Table 1, the alcohol component, terephthalic acid, and polyethylene terephthalate (PET) were placed in a 10 L four-necked flask equipped with a thermometer, a stainless steel stirring rod, a dehydration tube, a down-flow condenser, and a nitrogen inlet tube. Under a nitrogen atmosphere, the amount of tin(II) bis(2-ethylhexanoate) shown in Table 1 was added, and the temperature was raised to 235°C over 3 hours in a mantle heater and held at 235°C for 5 hours. Then, a vacuum reaction was carried out at 8.0 kPa for 1 hour. After visually confirming that the PET particles had disappeared from the reaction product, it was cooled to 180°C, and alkenyl succinic anhydride was added. After raising the temperature to 210°C over 2 hours, it was held at 210°C for 1 hour, and a vacuum reaction was carried out at 8.3 kPa. Then, the reaction was continued until the softening point shown in Table 1 was reached, and it was taken out into a stainless steel vat and solidified at room temperature to obtain polyester P1. Then, the solidified polyester P1 was crushed and pulverized using a screen with a mesh opening of 2 mm in NEW ROTOPLEX manufactured by Hosokawa Micron Corporation to obtain powdery polyester P1. The results are shown in Table 1. The alkenyl succinic anhydride used was dodecenyl succinic anhydride (average molecular weight 256).

[0075] Production Example 2 (Polyester P2) The raw material monomers shown in Table 1 were placed in a 10 L four-necked flask equipped with a thermometer, a stainless steel stirring rod, a dehydration tube, a nitrogen introduction tube, and a thermocouple. Tin(II) bis(2-ethylhexanoate) was added under a nitrogen atmosphere, and the temperature was raised to 235°C. Then, the reaction was carried out at 235°C for 8 hours, and further the reaction was carried out to the described softening point under reduced pressure conditions of 235°C and 8.3 kPa, and then taken out into a stainless steel vat and solidified at room temperature. The solidified block was coarsely crushed and then crushed using a pulverizer (trade name: NEW ROTOPLEX, manufactured by Hosokawa Micron Corporation) with a 2 mm opening screen to obtain powdery polyester P2. The results are shown in Table 1.

[0076]

Table 1

[0077] Production Example 3 (Asphalt Modifier BL-1: Powder Blend) 400 g of powdery styrene / butadiene / styrene block copolymer (molecular weight 130,000) and 1600 g of powdery polyester P1 were weighed and mixed at room temperature for 1 to 2 minutes so that the appearance became uniform, and asphalt modifier BL-1 (average particle size 288 μm) of the powder mixture was obtained.

[0078] Production Example 4 (Asphalt Modifier BL-2: Powder Blend) 400 g of powdery styrene / butadiene / styrene block copolymer (molecular weight 130,000) and 2000 g of powdery polyester P1 were weighed and mixed at room temperature for 1 to 2 minutes so that the appearance became uniform, and asphalt modifier BL-2 (average particle size 260 μm) of the powder mixture was obtained.

[0079] Production Example 5 (Asphalt Modifier BL-3: Powder Blend) Weighed 150 g of a powdery styrene-butadiene-styrene block copolymer (molecular weight 130,000) and 1850 g of powdery polyester P1, and mixed them at room temperature for 1 to 2 minutes so that the appearance was uniform, obtaining an asphalt modifier BL-3 (average particle size 240 μm) of a powder mixture.

[0080] Production Example 6 (Asphalt Modifier BL-4: Melt Blend) Put 6400 g of polyester P1 into a 10 L four-necked flask equipped with a thermometer, a stainless steel stirring rod, and a nitrogen inlet tube, heated and melted it at 180 °C in a nitrogen atmosphere, and added 1600 g of a room temperature styrene-butadiene-styrene block copolymer (molecular weight 130,000). Stirred at 180 °C for 5 minutes, cooled the obtained mixture to room temperature and then pulverized it to obtain an asphalt modifier BL-4 (average particle size 345 μm) of a melt mixture.

[0081] Production Example 7 (Asphalt Modifier BL-5: Powder Blend) Weighed 400 g of a powdery styrene-butadiene-styrene block copolymer (molecular weight 130,000) and 1600 g of powdery polyester P2, and mixed them at room temperature for 1 to 2 minutes so that the appearance was uniform, obtaining an asphalt modifier BL-5 (average particle size 295 μm) of a powder mixture.

[0082] Production Example 8 (Asphalt Modifier BL-6) Weighed 400 g of a lump-shaped styrene / butadiene / styrene block copolymer (molecular weight 130,000) and 1600 g of powdery polyester P1, and mixed them at room temperature for 1 to 2 minutes to obtain an asphalt modifier BL-6 of a granular mixture. The appearance of the obtained granular mixture was that powder adhered to the surface of the lump shape.

[0083] Production Example 9 (Asphalt Modifier BL-7: Powder Blend) Weighed 100 g of a powdery styrene-butadiene-styrene block copolymer (molecular weight 130,000) and 1900 g of powdery polyester P1, and mixed them at room temperature for 1 to 2 minutes so that the appearance was uniform, obtaining an asphalt modifier BL-7 (average particle size 231 μm) of a powder mixture.

[0084] Production Example 10 (Asphalt Modifier BL-8: Powder Blend) 700 g of powdery styrene-butadiene-styrene block copolymer (molecular weight 130,000) and 1300 g of powdery polyester P1 were weighed, mixed at room temperature for 1 to 2 minutes so that the appearance became uniform, and asphalt modifier BL-8 (average particle size 450 μm) of the powder mixture was obtained.

[0085] Example 1 15 kg of aggregates preheated to 180°C (for the aggregate composition, refer to the following) were put into an asphalt mixer and mixed at 180°C for 15 seconds. Next, 0.82 kg of polymer-modified asphalt type II was added and mixed for another 60 seconds, and then 123.4 g of asphalt modifier BL-1 obtained in Production Example 3 was added and mixed for another 90 seconds to obtain asphalt mixture AS-1. The obtained asphalt mixture AS-1 was filled into a room-temperature metal mold (300 mm × 300 mm × 50 mm) at about 10.4 kg, and using a pneumatic roller compactor (manufactured by Iwata Kogyosho Co., Ltd.), it was compacted by 25 rotations at a temperature of 160°C and a load of 0.44 kPa to produce a wheel tracking specimen (T-1a). After the specimen was left standing at room temperature for 12 hours or more, a performance evaluation test was carried out. The above wheel tracking specimen is a specimen for evaluating, by an accelerated test, the decrease in adhesiveness and water resistance accompanying the decrease in temperature at the end near the mold of the asphalt mixture, especially the obtained specimen. Usually, the metal mold is heated to about 180°C for use, but a room-temperature metal mold was used to reproduce the situation during on-site construction where the asphalt mixture near the mold is rapidly cooled.

[0086] <Composition of Aggregates> No. 6 crushed stone 40.0 parts by mass No. 7 crushed stone 13.0 parts by mass Crushed sand 10.0 parts by mass River sand 22.0 parts by mass Mountain sand 10.0 parts by mass Stone powder (calcium carbonate) 5.0 parts by mass Passing mass %: Sieve size 19.0 mm: 100 mass% Sieve size 9.50 mm: 80.1 mass% Sieve size 4.75 mm: 59.4 mass% Sieve size 2.36 mm: 43.4 mass% Sieve size 1.18 mm: 29.1 mass% Sieve size 600 μm: 18.9 mass% Sieve size 300 μm: 11.7 mass% Sieve size 150 μm: 7.6 mass%

[0087] [Performance Evaluation] [Adhesion of Asphalt Mixture] After demolding the above-mentioned asphalt specimen (T-1a) from the mold, the four sides of the specimen (the four sides with dimensions of 300 mm × 50 mm) were strongly rubbed 10 reciprocations on each side by hand, and the amount of asphalt mixture that fell off during this process was measured (falling amount (g)). Note that the rubbing was carried out while wearing rubber gloves (New Vinylon Gloves with wrist covers, manufactured by Showa Gloves Co., Ltd.), and the magnitude of the force applied was unified to 0.25 kN ± 0.02 kN to ensure that there was no difference in force for each specimen. The less the falling amount, the better the adhesion of the mixture can be said to be. The results are shown in Table 2.

[0088] [Water Resistance] The above asphalt specimen (T-1a) was immersed in warm water set at 60°C in a 60°C constant temperature chamber for 1 hour. Using a wheel tracking tester ("AI-1100-S" manufactured by Iwata Kogyosho Co., Ltd.), a water immersion wheel tracking test was conducted under the conditions of a temperature of 60°C, a traveling speed of 15 reciprocations / minute, a load of 1716 N, and using an iron wheel (width 47 mm) to determine the stripping inflection point (SIP). SIP is defined by the number of wheel rotations, and the calculation method of SIP followed AASHTO T324: Standard Method of Test for Hamburg Wheel-Track Testing of Compacted Asphalt Mixtures. Generally, the larger the value of SIP, the higher the stripping resistance of the asphalt mixture to water, that is, the higher the water resistance. The results are shown in Table 2.

[0089] Example 2 An asphalt mixture AS-2 was obtained under the same conditions as in Example 1, except that the addition amount of the asphalt modifier BL-1 obtained in Production Example 3 was 164.6 g. Performance evaluation was carried out in the same manner as in Example 1. Example 3 An asphalt mixture AS-3 was obtained under the same conditions as in Example 1, except that the asphalt modifier BL-2 obtained in Production Example 4 was used and the addition amount of BL-2 was 197.5 g. Performance evaluation was carried out in the same manner as in Example 1. Example 4 An asphalt mixture AS-4 was obtained under the same conditions as in Example 1, except that the asphalt modifier BL-3 obtained in Production Example 5 was used. Performance evaluation was carried out in the same manner as in Example 1. Example 5 An asphalt mixture AS-5 was obtained under the same conditions as in Example 1, except that the asphalt modifier BL-3 obtained in Production Example 5 was used and the addition amount of BL-3 was 164.6 g. Performance evaluation was carried out in the same manner as in Example 1. Example 6 An asphalt mixture AS-6 was obtained under the same conditions as in Example 1, except that the asphalt modifier BL-4 obtained in Production Example 6 was used and the addition amount of BL-4 was 164.6 g. Performance evaluation was carried out in the same manner as in Example 1. Example 7 An asphalt mixture AS-7 was obtained under the same conditions as in Example 1, except that the asphalt modifier BL-5 obtained in Production Example 7 was used. Performance evaluation was carried out in the same manner as in Example 1. Example 8 An asphalt mixture AS-8 was obtained under the same conditions as in Example 1, except that the asphalt modifier BL-6 obtained in Production Example 8 was used. Performance evaluation was carried out in the same manner as in Example 1. Example 9 An asphalt mixture AS-9 was obtained under the same conditions as in Example 1, except that the asphalt was straight asphalt 60 / 80 and the addition amount of the asphalt modifier BL-1 was 164.6 g. Performance evaluation was carried out in the same manner as in Example 1. Example 10 An asphalt mixture AS-10 was obtained under the same conditions as in Example 1, except that the asphalt modifier BL-7 obtained in Production Example 9 was used and the addition amount of BL-7 was 164.6 g. Performance evaluation was carried out in the same manner as in Example 1. Example 11 An asphalt mixture AS-11 was obtained under the same conditions as in Example 1, except that the asphalt modifier BL-8 obtained in Production Example 10 was used and the addition amount of BL-8 was 164.6 g. Performance evaluation was carried out in the same manner as in Example 1.

[0090] Comparative Example 1 15 kg of aggregates (the aggregate composition was the same as in Example 1) preheated to 180°C were put into an asphalt mixer and mixed at 180°C for 15 seconds. Then, 0.82 kg of polymer-modified asphalt type II was added and mixed for another 60 seconds to obtain an asphalt mixture as-1. Filling into the mold and performance evaluation were carried out in the same manner as in Example 1. Comparative Example 2 15 kg of the aggregate preheated to 180°C (the aggregate composition is the same as in Example 1) was put into an asphalt mixer and mixed at 180°C for 15 seconds. Next, 0.82 kg of polymer-modified asphalt type II was added and further mixed for 60 seconds. Then, 32.9 g of powdered styrene-butadiene-styrene block copolymer (molecular weight 130,000) was added and further mixed for 90 seconds to obtain asphalt mixture as-2. Filling into the mold and performance evaluation were carried out in the same manner as in Example 1. Comparative Example 3 15 kg of the aggregate preheated to 180°C (the aggregate composition is the same as in Example 1) was put into an asphalt mixer and mixed at 180°C for 15 seconds. Next, 0.82 kg of polymer-modified asphalt type II was added and further mixed for 60 seconds. Then, 123.4 g of the powdered polyester P1 obtained in Production Example 1 was added and further mixed for 90 seconds to obtain asphalt mixture as-3. Comparative Example 4 An asphalt mixture as-4 was obtained under the same conditions as in Comparative Example 3, except that the addition amount of polyester P1 was 164.6 g. Comparative Example 5 15 kg of the aggregate preheated to 180°C (the aggregate composition is the same as in Example 1) was put into an asphalt mixer and mixed at 180°C for 15 seconds. Next, 0.82 kg of polymer-modified asphalt type II was added and further mixed for 60 seconds. Then, 49.3 g of powdered styrene-butadiene-styrene block copolymer (molecular weight 130,000), 12.3 g of heavy oil, and 20.7 g of C9 petroleum resin were added and further mixed for 90 seconds to obtain asphalt mixture as-5.

[0091]

Table 2

[0092] From the results in Table 2, according to the present invention, it is possible to provide an asphalt mixture that can ensure good adhesiveness even when the temperature of the asphalt mixture drops during construction and has water resistance superior to that of the prior art. Therefore, it is expected to realize the construction of stable and highly durable asphalt pavement that is less affected by site and climate conditions. In Comparative Example 2, when the content of SBS is increased, the elasticity and viscosity of the asphalt mixture increase, so that the operations such as compacting the asphalt mixture tend to become difficult. And when the mixture cannot be properly compacted, it is considered that the pavement durability such as water resistance deteriorates.

Claims

1. An asphalt modifier comprising a thermoplastic elastomer (A) and a polyester (B).

2. The asphalt modifier according to Claim 1, wherein the content of the thermoplastic elastomer (A) is 5% by mass or more and 40% by mass or less based on 100% by mass of the total content of the thermoplastic elastomer (A) and the polyester (B).

3. The asphalt modifier according to Claim 1 or 2, which is a solid mixture.

4. The asphalt modifier according to Claim 1 or 2, which is a molten mixture.

5. The asphalt modifier according to any one of Claims 1 to 4, wherein the thermoplastic elastomer (A) is a vinyl aromatic compound-conjugated diene block copolymer.

6. Step (1a) of mixing heated aggregates and asphalt to obtain a mixture (M1) containing the aggregates and the asphalt, and A method for producing an asphalt mixture, comprising step (2) of mixing the mixture (M1), the thermoplastic elastomer (A), and the polyester (B).

7. The method for producing an asphalt mixture according to Claim 6, wherein the blending amount of the thermoplastic elastomer (A) is 5% by mass or more and 40% by mass or less based on 100% by mass of the total blending amount of the thermoplastic elastomer (A) and the polyester (B).

8. The method for producing an asphalt mixture according to Claim 6 or 7, further comprising step (1b) of mixing the thermoplastic elastomer (A) and the polyester (B) to obtain a mixture (M2) containing the thermoplastic elastomer (A) and the polyester (B), and wherein step (2) is step (2') of mixing the mixture (M1) and the mixture (M2).

9. The method for producing an asphalt mixture according to any one of Claims 6 to 8, wherein the thermoplastic elastomer (A) is a vinyl aromatic compound-conjugated diene block copolymer.

10. The method for producing an asphalt mixture according to any one of Claims 6 to 9, wherein the asphalt is a polymer-modified asphalt containing a thermoplastic elastomer.

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