Asphalt composition

Abstract

To provide an asphalt composition, an asphalt mixture, and a road pavement method which enable formation of a paved surface having excellent durability and flexibility.SOLUTION: An asphalt composition contains asphalt, a polyester resin, and crosslinked rubber.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to asphalt compositions, asphalt mixtures, methods for producing the same, and road paving methods. [Background technology]

[0002] Asphalt paving is used for roads, parking lots, freight yards, and sidewalks because it is relatively easy to lay and the time from the start of paving work to the start of traffic is short. Asphalt paving is formed by an asphalt mixture in which aggregates are bound together with asphalt, so the paved road has good hardness and durability. However, asphalt pavements deteriorate with long-term use, necessitating repairs. These repairs increase maintenance costs and significantly impact automobile traffic.

[0003] Furthermore, automobile tires require regular replacement, resulting in a large amount of waste tires. These waste tires are recycled by being used as fuel for thermal recycling as tire chips and cut tires, or as materials such as rubber powder, rubber chips, and elastic materials. However, the demand for these tires as fuel is rapidly declining, making it difficult to maintain resource recycling.

[0004] It is known that, conventionally, asphalt is mixed with rubber powder derived from waste tires to create asphalt rubber, which is then used as an asphalt binder for paving. Furthermore, from the perspective of effective waste utilization, it is also known that asphalt is mixed with rubber and / or thermoplastic elastomers, rubber waste, waste tires, sulfur-containing resins, etc., and then mixed with aggregates such as gravel and crushed stone for paving work.

[0005] Patent Document 1 discloses an asphalt composition that has excellent storage stability and can suppress rutting of the pavement surface after construction, which contains asphalt and polyester, a polycondensate of polyethylene terephthalate, a specific alcohol, and a carboxylic acid compound. Patent Document 2 discloses an asphalt composition using a high-performance asphalt additive that provides asphalt with excellent mixability between asphalt and aggregate, improved compaction and water resistance of the asphalt mixture, and excellent mechanical properties such as Marshall stability and dynamic stability. The composition comprises an additive containing repeating units of a specific structure, with at least one of the terminal groups having a specific structure, and asphalt. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2021 / 177443 [Patent Document 2] Japanese Patent Publication No. 2017-155233 [Overview of the project] [Problems that the invention aims to solve]

[0007] The technology described in Patent Document 1 provides an asphalt pavement with excellent durability. However, it sometimes lacks flexibility and crack resistance, leaving room for further improvement. Patent Document 2 discloses polymer modifiers such as recycled rubber from waste tires, but asphalt pavements containing rubber components tend to have poor durability. Patent Document 2 also discloses polyester fibers as a type of filler. However, polyester fibers are generally stretched and oriented, and although they have a good effect as fillers due to their high softening point, their asphalt modification effect may be insufficient. The present invention relates to an asphalt composition, an asphalt mixture, a method for producing the same, and a road paving method, which can maximize the modifying effect of polyester resin and form a paved surface with excellent durability and flexibility. [Means for solving the problem]

[0008] The present invention relates to the following [1] to [4]. [1] An asphalt composition containing asphalt, polyester resin, and crosslinked rubber. [2] An asphalt mixture containing asphalt, polyester resin, crosslinked rubber, and aggregate. [3] A method for producing an asphalt mixture, comprising the step of mixing asphalt, polyester resin, heated aggregate and crosslinked rubber. [4] A road paving method comprising the step of applying the asphalt mixture described in [2] above or the asphalt mixture obtained by the method described in [3] above to a road to form an asphalt pavement layer. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an asphalt composition, an asphalt mixture, a method for producing the same, and a road paving method that can form a paved surface having excellent durability and flexibility. In particular, if the cross-linked rubber is derived from waste tires, it can provide a new technology that complements the resource recycling of tires. [Modes for carrying out the invention]

[0010] [Asphalt composition] The asphalt composition contains asphalt, polyester resin, and crosslinked rubber.

[0011] The inventors have discovered that by mixing crosslinked rubber in combination with polyester resin into an asphalt composition, an asphalt composition can be obtained that can form a pavement surface with excellent durability and flexibility. Although the detailed mechanism by which the effects of the present invention are obtained is unknown, part of it can be considered as follows. It is considered that when a polyester resin and a crosslinked rubber are combined, viscoelasticity that cannot be exhibited by the crosslinked rubber alone in asphalt is expressed, and thereby durability and flexibility can be simultaneously imparted to an asphalt pavement.

[0012] The definitions of various terms in this specification are shown below. The "binder mixture" means a mixture containing asphalt and a thermoplastic elastomer, and is a concept including, for example, asphalt modified with a thermoplastic elastomer described later (hereinafter also referred to as "modified asphalt"). In the polyester resin, 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 "carboxylic acid component" is a concept including not only the carboxylic acid but also an anhydride that decomposes during the reaction to generate an acid, and an alkyl ester of the carboxylic acid (for example, having 1 to 3 carbon atoms in the alkyl group). When the carboxylic acid component is an alkyl ester of the 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.

[0013] <Asphalt> As asphalt, various types of asphalt can be used. For example, in addition to straight asphalt, which is petroleum asphalt for paving, modified asphalt can be mentioned. Examples of modified asphalt include blown asphalt; polymer-modified asphalt modified with polymer materials such as thermoplastic elastomers and thermoplastic resins. Straight asphalt refers to the residual asphalt substance obtained by subjecting crude oil to an atmospheric distillation unit, a vacuum distillation unit, etc. Also, blown asphalt means asphalt obtained by heating a mixture of straight asphalt and heavy oil and then blowing air into it for oxidation. Asphalt is preferably selected from straight asphalt and polymer-modified asphalt. From the perspective of the durability of asphalt pavement, polymer-modified asphalt is more preferable, and from the perspective of versatility, straight asphalt is more preferable. As polymer-modified asphalt, asphalt modified with a thermoplastic elastomer is more preferable. The modified asphalt is preferably polymer-modified asphalt, and more preferably polymer-modified asphalt modified with a thermoplastic elastomer.

[0014] (Thermoplastic elastomer) Examples of thermoplastic elastomers used in polymer-modified asphalt modified with thermoplastic elastomers include at least one selected from 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, ethylene / vinyl acetate copolymer, ethylene / acrylic acid ester copolymer, styrene / ethylene / butylene / styrene copolymer, styrene / ethylene / propylene / styrene copolymer, polyurethane-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, isobutylene / isoprene copolymer, polyisoprene, polychloroprene, synthetic rubber other than those listed above, and natural rubber. The thermoplastic elastomer in the modified asphalt is preferably at least one selected from 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, ethylene / vinyl acetate copolymer, and ethylene / acrylic acid ester copolymer. Among these, the thermoplastic elastomer is preferably at least one selected from 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 ethylene / acrylic acid ester copolymer, more preferably at least one selected from styrene / butadiene block copolymer, styrene / butadiene / styrene block copolymer, styrene / butadiene random copolymer, styrene / isoprene block copolymer, styrene / isoprene / styrene block copolymer, and styrene / isoprene random copolymer, and even more preferably at least one selected from styrene / butadiene random copolymer and styrene / butadiene / styrene block copolymer. The content of thermoplastic elastomer in polymer-modified asphalt is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, from the viewpoint of rutting resistance and surface aesthetics of the asphalt pavement.

[0015] <Polyester resin> The polyester resin contained in the asphalt composition of the present invention is a polycondensate of an alcohol component and a carboxylic acid component, comprising structural units derived from an alcohol component and structural units derived from a carboxylic acid component. Examples of polyester resins include amorphous polyester resins and crystalline polyester resins, with amorphous polyester resins being preferred. The following describes the properties of the alcohol component, carboxylic acid component, and polyester resin.

[0016] (Alcohol content) Examples of alcohol components include chain-type aliphatic diols, alicyclic diols, aromatic diols, and polyhydric alcohols with a hydride of three or more. These alcohol components can be used individually or in combination of two or more.

[0017] Preferably, the chain-like aliphatic diol is a linear or branched chain-like aliphatic diol with 2 to 12 carbon atoms in the main chain, and more preferably a linear or branched chain-like aliphatic diol with 2 to 8 carbon atoms in the main chain. Furthermore, the chain-type aliphatic diol is preferably a saturated chain-type aliphatic diol. Specific examples of chain-type 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.

[0018] Examples of alicyclic diols include hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane), alkylene oxide adducts of hydrogenated bisphenol A, cyclohexanediol, and cyclohexanedimethanol.

[0019] 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 those represented by the following formula (I).

[0020] [ka]

[0021] [In the formula, OR 1 and R 1 O is an alkylene oxide, and R 1x is an alkylene group having 2 or 3 carbon atoms, x and y are positive numbers representing the average number of added moles of alkylene oxide, and 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, and even more preferably 4 or less.

[0022] Examples of alkylene oxide adducts of bisphenol A represented by formula (I) include propylene oxide adducts of bisphenol A and ethylene oxide adducts of bisphenol A. These alkylene oxide adducts of bisphenol A can be used individually or in combination of two or more.

[0023] The polyhydric alcohol with a valency of three or higher is preferably a trihydric alcohol. Examples of polyhydric alcohols with a valency of three or higher include glycerin, pentaerythritol, trimethylolpropane, and sorbitol.

[0024] The alcohol component may further contain monohydric aliphatic alcohols from the viewpoint of adjusting physical properties. Examples of monohydric aliphatic alcohols include lauryl alcohol, myristyl alcohol, palmityl alcohol, and stearyl alcohol. These monohydric aliphatic alcohols can be used individually or in combination of two or more.

[0025] (Carboxylic acid component) Examples of carboxylic acid components include aliphatic dicarboxylic acids, aromatic dicarboxylic acids, and polycarboxylic acids with a valency of 3 to 6. These carboxylic acid components can be used individually or in combination of two or more.

[0026] Examples of aliphatic dicarboxylic acids include those having a main chain with four or more carbon atoms, preferably 10 or fewer, more preferably 8 or fewer, and more preferably 6 or fewer carbon atoms, such as fumaric acid, maleic acid, oxalic acid, malonic acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanediic 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 their anhydrides, or their alkyl esters (for example, alkyl groups with 1 to 3 carbon atoms). Examples of substituted succinic acids include dodecyl succinic acid, dodecenyl succinic acid, and octenyl succinic 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 their anhydrides, can be manufactured, for example, in accordance with the description in Japanese Patent Publication No. 2008-145712. Commercially available products can also be used.

[0027] Examples of aromatic dicarboxylic acids include phthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, or their anhydrides, or their alkyl esters (for example, alkyl groups with 1 to 3 carbon atoms). Among these aromatic dicarboxylic acids, isophthalic acid and terephthalic acid are preferred from the viewpoint of suppressing aggregate scattering and water resistance, and terephthalic acid is more preferred.

[0028] The polycarboxylic acid with a valency of 3 to 6 is preferably a tricarboxylic acid. Examples of polycarboxylic acids with a valency of 3 to 6 include trimellitic acid, 2,5,7-naphthalentricarboxylic acid, pyromellitic acid, or their acid anhydrides.

[0029] From the viewpoint of adjusting physical properties, the carboxylic acid component may further contain monovalent aliphatic carboxylic acids. Examples of monovalent aliphatic carboxylic acids include lauric acid, myristic acid, palmitic acid, stearic acid, and monovalent aliphatic carboxylic acids with 12 to 20 carbon atoms, such as alkyl (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.

[0030] (Constituent units derived from polyethylene terephthalate) The polyester resin may contain constituent units derived from polyethylene terephthalate, ethylene glycol, and terephthalic acid. In addition to the ethylene glycol and terephthalic acid-derived constituent units, the polyethylene terephthalate may also contain small amounts of other components such as butanediol and isophthalic acid. The polyethylene terephthalate is preferably recovered polyethylene terephthalate. When a polyester resin contains constituent units consisting of ethylene glycol and terephthalic acid derived from polyethylene terephthalate, the "constituent units derived from alcohol components" include constituent units derived from ethylene glycol derived from polyethylene terephthalate, and the "constituent units derived from carboxylic acid components" include constituent units derived from terephthalic acid derived from polyethylene terephthalate.

[0031] (Preferred embodiment of polyester resin) In a preferred embodiment of the polyester resin, from the viewpoint of ensuring compatibility with asphaltene in asphalt, the content of terephthalic acid in 100 mol% of the carboxylic acid component is preferably 20 mol% or more, more preferably 40 mol% or more, even more preferably 60 mol% or more, and preferably 100 mol% or less. Furthermore, in a preferred embodiment of the polyester resin, from the viewpoint of further improving durability by interacting with asphaltene in asphalt, the content of bisphenol A derivative in 100 mol% of the alcohol component is preferably 10 mol% or more, more preferably 20 mol% or more, even more preferably 30 mol% or more, and preferably 100 mol% or less.

[0032] Bisphenol A derivatives are alcohol components containing, for example, a structure represented by formula (i) or formula (ii) below.

[0033] [ka]

[0034] The phenylene group in formula (i) and the cyclohexylene group in formula (ii) may have substituents such as halogen atoms and C1-C3 alkyl groups. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms. Examples of C1-C3 alkyl groups include methyl, ethyl, n-propyl, and i-propyl groups.

[0035] Examples of bisphenol A derivatives include bisphenol A, alkylene oxide adducts of bisphenol A, hydrogenated bisphenol A, and alkylene oxide adducts of hydrogenated bisphenol A. Among these, alkylene oxide adducts of bisphenol A and hydrogenated bisphenol A are preferred.

[0036] (Physical properties of polyester resin) The softening point of the polyester resin is preferably 80°C or higher, more preferably 85°C or higher, even more preferably 90°C or higher, and preferably 140°C or lower, more preferably 130°C or lower, even more preferably 120°C or lower, and even more preferably 115°C or lower, from the viewpoint of durability and flexibility of asphalt pavement. From a similar viewpoint, the weight-average molecular weight Mw of the polyester resin is preferably 5000 or more, more preferably 7000 or more, even more preferably 8000 or more, and preferably 70000 or less, more preferably 40000 or less, and even more preferably 25000 or less. The acid value of polyester is preferably 1 mg KOH / g or more, more preferably 3 mg KOH / g or more, and even more preferably 5 mg KOH / g or more, from the viewpoint of durability and flexibility of asphalt pavement, and from the viewpoint of improving the water resistance of the pavement surface, it is preferably 60 mg KOH / g or less, more preferably 30 mg KOH / g or less, and even more preferably 10 mg KOH / g or less. The hydroxyl value of polyester is preferably 1 mg KOH / g or more, more preferably 10 mg KOH / g or more, even more preferably 20 mg KOH / g or more, and preferably 50 mg KOH / g or less, more preferably 45 mg KOH / g or less, and even more preferably 40 mg KOH / g or less, from the viewpoint of durability and flexibility of asphalt pavement.

[0037] The softening point, weight-average molecular weight (Mw), acid value, and hydroxyl value of the polyester resin can be measured by the method described in the examples. Note that the softening point, weight-average molecular weight (Mw), acid value, and hydroxyl value can be adjusted by the raw material monomer composition, molecular weight, catalyst amount, or reaction conditions.

[0038] The polyester resin may be a modified polyester resin to the extent that its properties are not substantially impaired. Specifically, modified polyester resins include polyester resins that have been grafted or blocked with phenol, urethane, epoxy, etc., by methods described in Japanese Patent Publication No. 11-133668, Japanese Patent Publication No. 10-239903, Japanese Patent Publication No. 8-20636, etc. A preferred modified polyester resin is a urethane-modified polyester resin obtained by urethane elongation of a polyester resin with a polyisocyanate compound.

[0039] (Polyester resin content) From the viewpoint of improving durability, the polyester resin content is preferably 1.5 parts by mass or more, more preferably 2.5 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of asphalt, and from the viewpoint of maintaining flexibility, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less.

[0040] (Method of manufacturing polyester resin) The polyester resin contained in the modified asphalt composition of the present invention can be produced, for example, by polycondensation of the alcohol component and carboxylic acid component described above. The temperature of the polycondensation reaction is preferably 160°C or higher, more preferably 190°C or higher, even more preferably 200°C or higher, and preferably 260°C or lower, more preferably 250°C or lower, and even more preferably 240°C or lower, from the viewpoint of adjusting the reactivity and the durability and flexibility of the asphalt pavement.

[0041] When the polyester resin used in the present invention contains constituent units derived from polyethylene terephthalate and constituent units derived from polyethylene terephthalate and polyethylene terephthalic acid, the amount of polyethylene terephthalate present in the raw material is preferably 5% by mass or more, more preferably 15% by mass or more, even more preferably 25% by mass or more, and preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less, based on the total amount of polyethylene terephthalate, alcohol component and carboxylic acid component. By adding polyethylene terephthalate during the polycondensation reaction between the alcohol component and the carboxylic acid component, a transesterification reaction occurs, resulting in a polyester resin in which the constituent units of polyethylene terephthalate are incorporated into the constituent units derived from the alcohol component and the constituent units derived from the carboxylic acid component. Polyethylene terephthalate may be present from the start of the polycondensation reaction or added to the reaction system during the reaction. From the viewpoint of durability and flexibility 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 when it is 5% or less. The reaction rate is defined as the value of (moles) of the amount of reaction water produced / (moles) of theoretical amount of reaction water produced × 100.

[0042] From the viewpoint of reaction rate, an esterification catalyst can be used in the polycondensation reaction. Examples of esterification catalysts include tin(II) compounds that do not have a Sn-C bond, such as di(2-ethylhexanoic acid)tin(II). From the viewpoint of reaction rate, the amount of esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.2 parts by mass or more, and preferably 1.5 parts by mass or less, more preferably 1.0 part by mass or less, and even more preferably 0.6 parts by mass or less, per 100 parts by mass of the total amount of alcohol and carboxylic acid components. In addition to the esterification catalyst, a co-catalyst can be used in the polycondensation reaction. Examples of co-catalysts include pyrogallol compounds such as gallic acid. The amount of co-catalyst used is preferably 0.001 parts by mass or more, more preferably 0.005 parts by mass or more, 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, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

[0043] <Cross-linked rubber> The asphalt composition of the present invention contains crosslinked rubber. The type of cross-linked rubber is not particularly limited and may be natural rubber, synthetic rubber, or a combination thereof. Examples of synthetic rubbers include diene-based synthetic rubbers, specifically styrene-butadiene copolymer, polybutadiene, polyisoprene, styrene-isoprene copolymer, butadiene-isoprene copolymer, butadiene-styrene-isoprene copolymer, acrylonitrile-butadiene copolymer, chloroprene rubber, butyl rubber, halogenated butyl rubber, etc. Furthermore, some of these may have a branched structure due to the use of a polyfunctional modifier, such as tin tetrachloride. The diene-based synthetic rubber may be used alone or in combination of two or more types. The crosslinked rubber is preferably a vulcanized rubber that is crosslinked with sulfur, other sulfur-containing compounds, peroxides, etc., and more preferably with sulfur, other sulfur-containing compounds. Cross-linked rubber is preferably derived from rubber products, and more preferably from used rubber products. Examples of rubber products include tires, and examples of used rubber products include discarded tires. The tires are automobile tires, industrial vehicle tires and construction vehicle tires, and among these, passenger car tires (PC) or truck and bus tires (TB) from the automobile tire category, or construction vehicle tires (OR) from the industrial vehicle and construction vehicle tire category, more preferably truck and bus tires (TB). Tires typically contain rubber components; compounding agents such as carbon black and sulfur; and structural material components. The crosslinked rubber contained in the asphalt composition of the present invention is preferably derived from tires, from the viewpoint of exhibiting a reinforcing effect due to carbon black.

[0044] From the viewpoint of durability, the cross-linked rubber is in the form of chips or powder, and more preferably in powder form. Furthermore, if the cross-linked rubber is derived from tires, it is preferably obtained by crushing tires. When the crosslinked rubber is in powder form, from the viewpoint of durability, its particle size is preferably 10 μm or more, more preferably 50 μm or more, even more preferably 100 μm or more, and 20 mm or less, more preferably 10 mm or less, even more preferably 5 mm or less, and even more preferably 3 mm or less. The particle size of powdered cross-linked rubber can be measured using a test sieve conforming to JIS Z 8801:2019. In this specification, "particle size" and "grain size" are used interchangeably. Examples of commercially available cross-linked rubber include powdered rubber manufactured by Shinsei Rubber Co., Ltd. (granule sizes #16, #30, #50, etc.).

[0045] The crosslinked rubber is preferably dispersed in the asphalt composition, and more preferably dispersed in the asphalt composition in a solid state.

[0046] (Cross-linked rubber content) From the viewpoint of improving durability, the cross-linked rubber content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of asphalt, and from the viewpoint of maintaining workability, it is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less. Note that when using waste tires, the cross-linked rubber content also includes the weight of components other than rubber, such as carbon black. The mass ratio of the crosslinked rubber in the asphalt composition to the polyester resin [(polyester resin) / (crosslinked rubber)] is preferably 1 / 9 or more, more preferably 2 / 8 or more, even more preferably 3 / 7 or more, and preferably 9 / 1 or less, more preferably 7 / 3 or less, and even more preferably 5 / 5 or less, from the viewpoint of achieving both durability and flexibility.

[0047] The asphalt composition of the present invention is a binder composition, and for example, by adding aggregate to the asphalt composition to make an asphalt mixture, it can be used for paving. In other words, the asphalt composition of the present invention is suitable for paving, and is particularly suitable for road paving. Furthermore, in an asphalt mixture that can be produced by mixing polyester resin and crosslinked rubber with a mixture containing asphalt and aggregate, the asphalt binder that constitutes the layer covering the aggregate is also an asphalt composition of the present invention.

[0048] [Method for producing asphalt composition] The method for producing the asphalt composition of the present invention preferably includes a step of mixing asphalt, the polyester resin, and the crosslinked rubber. It is preferable that the above-mentioned polyester resin and crosslinked rubber be added to the asphalt in the same process. That is, it is preferable that the crosslinked rubber be added together with the polyester resin and dispersed in the asphalt, rather than being pre-mixed into the asphalt as a modifier for modified asphalt. Furthermore, the asphalt composition can be manufactured, for example, by mixing polyester resin and crosslinked rubber with a mixture containing asphalt and aggregate. The resulting mixture will have the aggregate covered with a layer of the asphalt composition.

[0049] The asphalt composition is obtained by heating and melting asphalt, adding polyester resin and crosslinked rubber, and stirring and mixing in a commonly used mixer until each component is uniformly dispersed. Commonly used mixers include homomixers, dissolvers, paddle mixers, ribbon mixers, screw mixers, planetary mixers, vacuum backflow mixers, roll mills, and twin-screw extruders.

[0050] The mixing temperature of the asphalt with the polyester resin and crosslinked rubber is preferably 100°C or higher, more preferably 130°C or higher, even more preferably 160°C or higher, and even more preferably 170°C or higher, and preferably 230°C or lower, more preferably 210°C or lower, even more preferably 200°C or lower, and even more preferably 190°C or lower, from the viewpoint of uniformly dispersing the polyester resin and crosslinked rubber in the asphalt.

[0051] Furthermore, the mixing time between the asphalt and the polyester resin and crosslinked rubber is preferably 1 minute or more from the viewpoint of efficiently and uniformly dispersing the polyester resin and crosslinked rubber in the asphalt, and preferably 10 hours or less, more preferably 7 hours or less, even more preferably 5 hours or less, even more preferably 3 hours or less, and even more preferably 1 hour or less from the viewpoint of improving productivity. From the viewpoint of further dispersibility, the above mixing time is more preferably 10 minutes or more, even more preferably 0.5 hours or more, even more preferably 1.0 hour or more, and even more preferably 1.5 hours or more. And from the viewpoint of further improving productivity, even more preferably 10 minutes or less, and even more preferably 2 minutes or less.

[0052] [Asphalt mixture] The asphalt mixture of the present invention contains the above-mentioned asphalt, aggregate, polyester resin, and crosslinked rubber.

[0053] The total content of the polyester resin and the crosslinked rubber in the asphalt mixture is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.10% by mass or more, even more preferably 0.15% by mass or more, and preferably 4% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and even more preferably 1% by mass or less. The asphalt content in the asphalt mixture is preferably 2.5% by mass or more, more preferably 3% by mass or more, even more preferably 3.5% by mass or more, even more preferably 4% by mass or more, and preferably 10% by mass or less, more preferably 9% by mass or less, even more preferably 8% by mass or less, and even more preferably 7% by mass or less.

[0054] In the asphalt mixture of the present invention, the total content of the polyester resin and the crosslinked rubber is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less, from the viewpoint of durability of asphalt pavement.

[0055] <Aggregates> As aggregate, crushed stone, pebbles, gravel, sand, recycled aggregate, ceramics, etc., can be arbitrarily selected and used. 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 as aggregate. 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 is preferably fine aggregate with a particle size of 0.075 mm or more and less than 2.36 mm. Examples of 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, foundry sand, and recycled aggregate crushed sand. The particle size values ​​mentioned above are those specified in JIS A5001:2008. Among these, a combination of coarse aggregate and fine aggregate is preferred.

[0056] The aggregate may further contain fillers with a particle size of less than 0.075 mm. Examples of fillers include sand, fly ash, calcium carbonate powder such as limestone powder, and slaked lime. Among these, calcium carbonate powder is preferred 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, more preferably 0.05 mm or less, more preferably 0.03 mm or less, and even more preferably 0.02 mm or less. Here, the average particle size is the average particle size at 50% volume accumulation (D 50 This means that it can be measured with a laser diffraction particle size distribution analyzer.

[0057] From the viewpoint of durability of asphalt pavement, the mass ratio of coarse aggregate to fine aggregate is preferably 10 / 90 or more, more preferably 15 / 85 or more, even more preferably 20 / 80 or more, and preferably 90 / 10 or less, more preferably 80 / 20 or less, and even more preferably 70 / 30 or less.

[0058] The following are examples of suitable formulations for asphalt mixtures: (1) Fine-graded asphalt comprising 30% to less than 45% by volume of coarse aggregate, 30% to 50% by volume of fine aggregate, and 5% to 10% by volume of asphalt composition. (2) An example of an asphalt mixture is dense-graded asphalt comprising, for example, 45% to less than 70% by volume of coarse aggregate, 20% to 45% by volume of fine aggregate, and 3% to 10% by volume of asphalt composition. (3) Porous asphalt comprising 70% to 80% by volume of coarse aggregate, 10% to 20% by volume of fine aggregate, and 3% to 10% by volume of asphalt composition. In addition, the mixing ratio of asphalt in conventional asphalt mixtures containing aggregate and asphalt is usually determined according to the optimal amount of asphalt found in the "Asphalt Composition Mix Design" described in the "Pavement Design and Construction Guidelines" published by the Japan Road Association. In this invention, the above-mentioned optimal amount of asphalt corresponds to the total amount of asphalt, polyester resin, and crosslinked rubber. However, it is not necessary to limit the method to the method described in the "Guidelines for Pavement Design and Construction," and it may be determined by other methods. One embodiment of the present invention is a state in which aggregate is covered with a layer of the above-described asphalt composition of the present invention.

[0059] [Method for producing asphalt mixture] The present invention provides a method for producing an asphalt mixture, comprising the steps of mixing asphalt, heated aggregate, polyester resin, and crosslinked rubber. The mixing process involves mixing asphalt, heated aggregate, polyester resin, and crosslinked rubber simultaneously or in any order. From the viewpoint of durability and flexibility of the asphalt pavement, it is preferable to mix the crosslinked rubber with the heated aggregate at the same time as the asphalt or after the asphalt. It is preferable that the above-mentioned polyester resin and crosslinked rubber be added to the asphalt in the same process. That is, it is preferable that the crosslinked rubber be added together with the polyester resin and dispersed in the asphalt, rather than being pre-mixed into the asphalt as a modifier for modified asphalt. Specific methods for manufacturing asphalt mixtures include conventional methods such as the plant mix method and the premix method. Both methods involve adding the polyester resin and the crosslinked rubber to heated aggregate, asphalt (and, if necessary, a thermoplastic elastomer). Addition methods include, for example, the premix method in which asphalt (and, if necessary, a thermoplastic elastomer), the polyester resin, and the crosslinked rubber are dissolved in advance, or the plant mix method in which asphalt (and, if necessary, a thermoplastic elastomer) is added to the aggregate, and then the polyester resin and the crosslinked rubber are added simultaneously or in any order. Among these, the plant mix method is preferred from the viewpoint of exhibiting asphalt performance. More specifically, the method for producing an asphalt mixture preferably involves the following steps in the mixing process: (i) Add and mix asphalt (and thermoplastic elastomer as necessary) to heated aggregate to obtain a mixture, then add the polyester resin and the crosslinked rubber and mix the mixture with the polyester resin and the crosslinked rubber. (ii) Add and mix asphalt (and thermoplastic elastomer as necessary), the polyester resin and the crosslinked rubber to the heated aggregate simultaneously, or (iii) Add and mix the mixture of preheated and mixed asphalt (and thermoplastic elastomer if necessary), the polyester resin, and the crosslinked rubber to the heated aggregate. Among these, the mixing process is preferably (i), in which asphalt and heated aggregate are mixed first, and then polyester resin and crosslinked rubber are mixed, from the viewpoint of efficiently dispersing the asphalt components.

[0060] In the methods described in (i) to (iii) above, the method for preparing the mixture of asphalt (and optionally a thermoplastic elastomer), polyester resin, and the crosslinked rubber is not particularly limited, but it is preferable to include the step of heating and melting the asphalt, adding the polyester resin, the crosslinked rubber, and optionally other additives, and stirring and mixing in a commonly used mixer until each component is uniformly dispersed. Commonly used mixers include homomixers, dissolvers, paddle mixers, ribbon mixers, screw mixers, planetary mixers, vacuum backflow mixers, roll mills, twin-screw extruders, etc.

[0061] The mixing temperature of the above-mentioned asphalt, polyester resin, and crosslinked rubber is preferably 100°C or higher, more preferably 130°C or higher, even more preferably 160°C or higher, even more preferably 170°C or higher, and preferably 230°C or lower, more preferably 210°C or lower, even more preferably 200°C or lower, and even more preferably 190°C or lower, from the viewpoint of uniformly dispersing the polyester resin in the asphalt and exhibiting asphalt performance.

[0062] Furthermore, the mixing time for the asphalt, polyester resin, and crosslinked rubber is preferably 0.1 hours or more, more preferably 0.5 hours or more, even more preferably 1.0 hour or more, even more preferably 1.5 hours or more, and preferably 10 hours or less, more preferably 7 hours or less, even more preferably 5 hours or less, and even more preferably 3 hours or less, from the viewpoint of efficiently and uniformly dispersing the polyester resin and crosslinked rubber in the asphalt and exhibiting asphalt performance. The preferred content of the polyester resin and crosslinked rubber in relation to the asphalt is as described above.

[0063] The asphalt mixture of the present invention is preferably used as a hot asphalt mixture that is substantially free of water.

[0064] [Road paving construction methods] The asphalt mixture of the present invention is suitable for road paving. The road paving construction method of the present invention preferably includes the step of applying the asphalt mixture of the present invention to a road or the like to form an asphalt paving material layer. The asphalt paving material layer is usually the base layer or surface layer of the road, and is preferably the surface layer of the road from the viewpoint of exhibiting the effect of resistance to rutting.

[0065] In road paving methods, the asphalt mixture can be compacted using the same construction machinery configuration and method as for ordinary asphalt mixtures. When used as a heated asphalt mixture, the compaction temperature of the asphalt mixture is preferably 100°C or higher, more preferably 120°C or higher, even more preferably 130°C or higher, and preferably 200°C or lower, more preferably 180°C or lower, and even more preferably 170°C or lower, from the viewpoint of exhibiting asphalt performance. [Examples]

[0066] Various physical properties were measured and evaluated using the following methods. In the following examples and comparative examples, unless otherwise specified, parts and percentages are based on mass.

[0067] (1) Vicat softening temperature of the polyester resin Using a flow tester "CFT-500D" (manufactured by Shimadzu Corporation), a 1 g sample was heated at a rate of 6 °C / min while applying a load of 1.96 MPa with a plunger and extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. The plunger drop of the flow tester was plotted against the temperature, and the temperature at which half of the sample had flowed out was taken as the Vicat softening temperature.

[0068] (2) Molecular weight of the polyester The weight-average molecular weight was determined by gel permeation chromatography (GPC) using the following method. (i) Preparation of the sample solution The sample was dissolved in chloroform at 40 °C to a concentration of 0.5 g / 100 mL. Then, this solution was filtered using a PTFE type membrane filter "DISMIC-25JP" (manufactured by Toyo Roshi Kaisha, Ltd.) with a pore size of 0.20 μm to remove insoluble components, and used as the sample solution. (ii) Molecular weight measurement Using the following measuring apparatus and analytical column, chloroform was used as the eluent and flowed at a rate of 1 mL / min, and the column was stabilized in a thermostat at 40 °C. 200 μL of the sample solution was injected there and measurement was carried out. The molecular weight of the sample was calculated based on a calibration curve prepared in advance. For this calibration curve, several types of monodisperse polystyrenes (A-500 (5.0×10 2 ), A-1000 (1.01×103), A-2500 (2.63×10 3 ), A-5000 (5.97×10 3 ), F-1 (1.02×10 4 ), F-2 (1.81×10 4 ), F-4 (3.97×10 4 ), F-10 (9.64×10 4 ), F-20 (1.90×10 5 ), F-40 (4.27×10 5 ), F-80 (7.06×10 5 ), F-128 (1.09×10 6 )) manufactured by Tosoh Corporation were used as standard samples. The values in parentheses indicate the molecular weights. Measuring device: "HLC-8320GPC" (manufactured by Tosoh Corporation) Analysis columns: "TSKgel Super HZM" + "TSKgel Super H-RC" x 2 (manufactured by Tosoh Corporation)

[0069] (3) Acid value and hydroxyl value of polyester The acid value and hydroxyl value of 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)).

[0070] Manufacturing Example 1 (Polyester Resin A-1) The raw materials other than alkenyl succinic anhydride shown in Table 1 were placed in a 10-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, a drop-through condenser, and a nitrogen inlet tube. Under a nitrogen atmosphere, the amount of di(2-ethylhexanoate)tin(II) shown in Table 1 was added, and the temperature was raised to 235°C over 3 hours in a mantle heater. After reaching 235°C, the temperature was maintained for 5 hours, and after visual confirmation that the PET particles had disappeared from the reaction mixture, it was cooled to 180°C. After cooling to 180°C, alkenyl succinic anhydride (molecular weight = 256) was added, and the temperature was raised to 210°C over 2 hours, and then maintained at 210°C for 1 hour. A reduced-pressure reaction was carried out at 8.3 kPa, and the reaction was continued until the softening point of 105.2°C shown in Table 1 was reached, yielding the target polyester resin A-1.

[0071] Manufacturing Example 2 (Polyester Resin B-1) The alcohol components of the polyester shown in Table 1 and terephthalic acid were placed in a 5-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, fall-flow condenser, and nitrogen inlet tube. Under a nitrogen atmosphere, the amount of tin(II) di(2-ethylhexanoate) shown in Table 1 was added, and the temperature was raised to 235°C over 3 hours in a mantle heater, where it was maintained for 7 hours. A reduced-pressure reaction was carried out at 8.0 kPa until the softening point of 107.0°C shown in the table was reached, yielding the target polyester resin B-1.

[0072] [Table 1]

[0073] Example 1 15 kg of aggregate heated to 180°C (see below for aggregate composition) was placed in an asphalt mixer and mixed at 180°C for 60 seconds. Next, 820 g of straight asphalt (manufactured by Mitsubishi Corporation Energy) was added and mixed in the asphalt mixer for 1 minute. Then, 41 g of polyester A1 and 41 g of crosslinked rubber 1 (powdered rubber #16, manufactured by Shinsei Rubber Co., Ltd.) were added and mixed in the asphalt mixer for 2 minutes. The resulting asphalt mixture was in a state where the aggregate was covered with a layer of asphalt composition. Visual inspection of the asphalt composition confirmed that there was no aggregation of the crosslinked rubber and that the crosslinked rubber was dispersed in the asphalt in a solid state. The obtained asphalt mixture was quickly filled into a 300 x 300 x 50 mm mold, and asphalt specimens were prepared by applying pressure for 25 rotations at a temperature of 150°C and a load of 0.44 kPa using a roller compactor (manufactured by Iwata Kogyosho Co., Ltd.), followed by heat curing at 180°C for 2 hours. In addition, 1.2 kg of asphalt mixture was weighed and cylindrical specimens were prepared using a Marshall test compactor (manufactured by Nakajima Gihan Co., Ltd., "Automatic Asphalt Compactor"). The specimens were slowly cooled to room temperature and demolded using a demolding machine. <Composition of aggregates> Crushed stone No. 6, 40.0 parts by mass Crushed stone No. 7, 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 mesh size 15 mm: 100% by mass Sieve mesh size 10 mm: 88.7% by mass Sieve mesh size 5 mm: 60.5% by mass Sieve mesh size 2.5 mm: 42.6% by mass Sieve mesh size 1.2 mm: 29.9% by mass Sieve mesh size 0.6 mm: 19.8% by mass Sieve mesh size 0.3 mm: 11.5% by mass Sieve mesh size 0.15 mm: 6.2% by mass

[0074] [evaluation] <Evaluation of rutting depth (wheel tracking test)> The obtained asphalt mixture was promptly filled into a 300 x 300 x 50 mm mold and subjected to heat curing by being stored at 180°C for 2 hours. Then, using a roller compactor (manufactured by Iwata Kogyosho Co., Ltd.), it was subjected to 25 rotations at a temperature of 150°C and a load of 0.44 kPa to produce asphalt specimen M-1a. Asphalt specimen M-1a was immersed in hot water set to 60°C in a 60°C constant temperature chamber. A wheel tracking test machine (manufactured by Iwata Kogyosho Co., Ltd., load 1716N, wheel width 47mm, line pressure 291.5N / cm) was used to move a wheel back and forth over the specimen at a speed of 15 reciprocations / minute, and the displacement was measured after 1,250 reciprocations. Other measurement conditions followed the "B003 Wheel Tracking Test" described in the "Pavement Survey and Testing Methods Handbook" published by the Japan Road Association. Furthermore, the amount of rutting in wheel tracking tests is an indicator of the durability of asphalt pavement. The results are shown in Table 2.

[0075] <Measurement of flow value: Marshall stability test> The obtained asphalt mixture weighed 1.2 kg, was stored at 180°C for 2 hours for heat curing, and then compacted 50 times on each side for a total of 100 times using a Marshall test compactor, the "Automatic Asphalt Compactor" (manufactured by Nakajima Gihan Co., Ltd.), to produce a cylindrical asphalt specimen M-1b. After demolding, the asphalt specimen M-1b was immersed in a 60°C constant temperature water bath for 30 minutes. Then, using a Marshall loading device (manufactured by Nakajima Gihan Co., Ltd.), the overturned asphalt specimen M-1b was crushed with a flat plate at a speed of 50 mm / min, and the amount of displacement from the starting point of the displacement slope to the maximum load was measured and defined as the flow value. Other measurement conditions followed the "B001 Marshall Stability Test" described in the "Pavement Survey and Testing Methods Handbook" published by the Japan Road Association. The flow value is used as an indicator of the flexibility and crack resistance of asphalt pavement at its service temperature. The results are shown in Table 2.

[0076] Examples 2-5, Comparative Examples 1-5 Except for changing the asphalt mixture formulation to the one shown in Table 2, asphalt specimens were prepared in the same manner as in Example 1, and the rutting depth and flow value were evaluated. The results are shown in Table 2.

[0077] The crosslinked rubbers used in Examples 1-5 and Comparative Examples 1-5 are shown below. Cross-linked rubber 1: Powdered rubber #16 (particle size under 1 mm), Main material: TB tire, manufactured by Shinsei Rubber Co., Ltd. Cross-linked rubber 2: Powdered rubber #30 (particle size under 500 μm), Main material: TB tire, manufactured by Shinsei Rubber Co., Ltd. Cross-linked rubber 3: Powdered rubber #50 (particle size under 300 μm), Main material: TB tire, manufactured by Shinsei Rubber Co., Ltd. Furthermore, cross-linked rubbers 1-3 are all manufactured by crushing waste tires.

[0078] [Table 2]

[0079] The results shown in Table 2 indicate that the present invention provides asphalt pavement with excellent durability and flexibility.

Claims

1. An asphalt composition comprising asphalt, a polyester resin, and a crosslinked rubber.

2. The asphalt composition according to claim 1, wherein the mass ratio of the crosslinked rubber to the polyester resin [(crosslinked rubber) / (polyester resin)] is 1 / 9 or more and 9 / 1 or less.

3. The asphalt composition according to claim 1, wherein the crosslinked rubber is derived from a tire.

4. 4. The asphalt composition according to claim 3, wherein the tire-derived crosslinked rubber is obtained by crushing tires.

5. The asphalt composition of claim 3, wherein the tire is a scrap tire.

6. The asphalt composition according to claim 1, wherein the particle size of the crosslinked rubber is 20 mm or less.

7. The asphalt composition of claim 1 , wherein the crosslinked rubber is dispersed in the asphalt.

8. 2. The asphalt composition of claim 1, wherein the polyester resin comprises constitutional units derived from ethylene glycol derived from polyethylene terephthalate and constitutional units derived from terephthalic acid.

9. The asphalt composition according to any one of claims 1 to 8, wherein the asphalt is straight asphalt or modified asphalt.

10. 10. The asphalt composition of claim 9, wherein the modified asphalt is a thermoplastic elastomer-modified asphalt.

11. An asphalt mixture containing asphalt, polyester resin, cross-linked rubber and aggregate.

12. The asphalt mixture according to claim 11, wherein the total content of the polyester resin and the crosslinked rubber in the asphalt mixture is 0.01% by mass or more and 4% by mass or less.

13. The asphalt mixture according to claim 11, wherein the particle size of the crosslinked rubber is 20 mm or less.

14. 12. The asphalt mixture of claim 11, wherein the polyester resin comprises building blocks derived from ethylene glycol and building blocks derived from terephthalic acid derived from polyethylene terephthalate.

15. A method for producing an asphalt mixture, comprising the step of mixing asphalt, polyester resin, heated aggregate, and crosslinked rubber.

16. The method for producing an asphalt mixture according to claim 15, wherein the mixing step is a step of mixing the asphalt and the heated aggregate, and then mixing the polyester resin and the crosslinked rubber.

17. The method for producing an asphalt mixture according to claim 15, wherein the polyester resin and the crosslinked rubber are added to the asphalt in the same step.

18. A road paving method comprising a step of applying the asphalt mixture according to any one of claims 11 to 14 or the asphalt mixture obtained by the method according to any one of claims 15 to 17 to a road to form an asphalt pavement layer.