Method for producing asphalt mixture

Abstract

The purpose of the present invention is to provide a method for producing an asphalt mixture, the method having: a step for mixing 100 parts by mass of an aggregate with 0.03-4 parts by mass of an asphalt masterbatch at 100-200ºC; and a step for further adding and mixing asphalt (c). The asphalt masterbatch contains: 10-50 mass% of a modified hydrogenated petroleum resin (a) that satisfies conditions (1) to (3); and straight asphalt (b). By using this method, it is possible to obtain an asphalt mixture which can efficiently bring out a water resistance-improving effect of an additive and which exhibits excellent water resistance. (1) Silicon element is contained at a quantity of 0.5-20 mass% in terms of silicon atoms; (2) The weight average molecular weight is 500-5000; (3) The molecular weight distribution (Mw / Mn) is 1.1-3.5.

Description

Asphalt mixture manufacturing method

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

[0002] In recent years, asphalt peeling, a phenomenon in which rainwater or groundwater penetrates between the asphalt and aggregate, causing the asphalt coating on the aggregate surface to peel off, has become a major cause of damage to asphalt pavements. This asphalt peeling reduces the ability of the aggregates to adhere to one another, potentially increasing the likelihood of damage such as cracks and potholes. To address this issue, methods have been developed to prevent asphalt peeling by incorporating anti-peeling agents into the asphalt, such as resin acids (e.g., dimer acid and rosin), saturated fatty acids (e.g., stearic acid, palmitic acid, and myristic acid), and unsaturated fatty acids (e.g., oleic acid, linoleic acid, and ricilenoic acid) (Patent Documents 1 and 2). Furthermore, Patent Document 3 discloses an asphalt composition containing a silane-containing compound having a cyclic structure within its molecular structure or a modified hydrogenated petroleum resin with specific bromine value, silicon content, weight-average molecular weight, and molecular weight distribution, with the aim of providing a technology for preventing asphalt peeling and improving water resistance.

[0003] JP 2016-121320 A JP 2015-143340 A International Publication No. 2021 / 161672

[0004] Although anti-stripping agents such as resin acids and fatty acids are expensive to combat the above-mentioned asphalt peeling phenomenon, adding them in excess of a certain amount does not provide sufficient anti-stripping effect, especially for acidic rocks such as granite. Therefore, a technology to suppress asphalt peeling is needed for these rocks as well. Furthermore, the technology disclosed in Patent Document 3 requires a large amount of silane-containing compound to achieve its performance. Therefore, a large amount of silane-containing compound must be added to the asphalt to be mixed with aggregate, which is inefficient. In other words, using a large amount of silane-containing compound not only increases costs, but also leads to crosslinking of the silane-containing compound in the high-temperature environment when mixed with aggregate, which can actually hinder performance. Therefore, a method has been sought for improving the water resistance of asphalt pavements by more efficiently using additives such as silane-containing compounds while suppressing unnecessary reactions such as crosslinking. Therefore, an object of the present invention is to provide a method for producing an asphalt mixture that can efficiently utilize the water-resistance-improving effect of additives and produce an asphalt mixture with excellent water resistance.

[0005] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by using a method including a step of mixing an asphalt masterbatch containing a specific modified hydrogenated petroleum resin with aggregate.

[0006] That is, the present invention relates to the following items <1> to <6>. <1> A method for producing an asphalt mixture, comprising the steps of mixing 0.03 to 4 parts by mass of an asphalt masterbatch with 100 parts by mass of aggregate at 100 to 200°C, and further adding and mixing asphalt (c), wherein the asphalt masterbatch contains 10 to 50% by mass of a modified hydrogenated petroleum resin (a) that satisfies the following (1) to (3), and straight asphalt (b): (1) Contains 0.5 to 20.0% by mass of silicon atoms, (2) Has a weight-average molecular weight of 500 to 5,000, and (3) Has a molecular weight distribution (Mw / Mn) of 1.1 to 3.5. <2> A method for producing an asphalt mixture according to item <1>, wherein the modified hydrogenated petroleum resin (a) has a softening point of 60 to 150°C. <3> The method for producing an asphalt mixture according to <1> or <2>, wherein the mass ratio [(a) / (b)] of the modified hydrogenated petroleum resin (a) to the straight asphalt (b) in the asphalt masterbatch is 10 / 90 to 50 / 50. <4> The method for producing an asphalt mixture according to any one of <1> to <3>, wherein the total amount of the asphalt (c) and the straight asphalt (b) is 3 to 10 parts by mass per 100 parts by mass of aggregate. <5> The method for producing an asphalt mixture according to any one of <1> to <4>, wherein the asphalt mixture contains 1.3 to 4.0 ppm by mass of silicon atom-equivalent silicon element contained in the modified hydrogenated petroleum resin (a). <6> An asphalt masterbatch used in the method for producing an asphalt mixture according to any one of <1> to <5>, comprising 10 to 50 mass% of a modified hydrogenated petroleum resin (a) that satisfies the following (1) to (3), and straight asphalt (b): (1) Contains 0.5 to 20.0 mass% silicon element in terms of silicon atoms, (2) Has a weight average molecular weight of 500 to 5,000, and (3) Has a molecular weight distribution (Mw / Mn) of 1.1 to 3.5.

[0007] According to the present invention, it is possible to provide a method for producing an asphalt mixture that can efficiently bring out the water resistance improving effect of an additive and obtain an asphalt mixture that has excellent water resistance.

[0008] [Method for manufacturing asphalt mixture] The method for manufacturing an asphalt mixture of the present invention comprises the steps of mixing 0.03 to 4 parts by mass of an asphalt masterbatch with 100 parts by mass of aggregate at 100 to 200°C, and further adding and mixing asphalt (c), wherein the asphalt masterbatch contains 10 to 50% by mass of a modified hydrogenated petroleum resin (a) and straight asphalt (b) that satisfy the following (1) to (3): (1) Contains 0.5 to 20.0% by mass of silicon atoms, (2) A weight-average molecular weight of 500 to 5,000, and (3) A molecular weight distribution (Mw / Mn) of 1.1 to 3.5.

[0009] The reason why the water resistance-improving effect of the additives can be efficiently exploited and an asphalt mixture with excellent water resistance can be obtained by the asphalt mixture production method of the present invention is unclear, but it is thought to be as follows. According to conventional technology, the additive silane-containing compound is mixed with the entire asphalt, so in the production of asphalt mixtures, most of the additives other than those around the aggregates are located away from the aggregates, which does not contribute to the adhesion between the aggregates and asphalt, resulting in inefficiency. On the other hand, by first mixing the asphalt masterbatch containing a relatively large amount of the modified hydrogenated petroleum resin with the aggregates, the aggregate surfaces can be efficiently coated with the additives, which develops affinity between the aggregate surfaces and asphalt and improves adhesion. Therefore, it is believed that the water resistance-improving effect of the additives can be efficiently exploited and an asphalt mixture with excellent water resistance can be obtained. The details of the asphalt mixture production method of the present invention are described below.

[0010] <Asphalt Masterbatch Mixing Step> The method for producing an asphalt mixture of the present invention includes a step of mixing 0.03 to 4 parts by mass of asphalt masterbatch with 100 parts by mass of aggregate at 100 to 200°C. The asphalt masterbatch contains 10 to 50% by mass of a modified hydrogenated petroleum resin (a) and straight asphalt (b) that satisfy the following (1) to (3): (1) Contains 0.5 to 20.0% by mass of silicon element, calculated as silicon atoms; (2) A weight-average molecular weight of 500 to 5,000; and (3) A molecular weight distribution (Mw / Mn) of 1.1 to 3.5.

[0011] (Aggregate) The aggregate used in this step may be crushed stone, gravel, recycled aggregate, sand, or the like.

[0012] (Asphalt Masterbatch) The asphalt masterbatch used in this process contains 10 to 50 mass% of modified hydrogenated petroleum resin (a) and straight asphalt (b) that satisfy the following (1) to (3): (1) Contains 0.5 to 20.0 mass% silicon element in terms of silicon atoms, (2) Has a weight average molecular weight of 500 to 5,000, and (3) Has a molecular weight distribution (Mw / Mn) of 1.1 to 3.5.

[0013] [Modified Hydrogenated Petroleum Resin (a)] The modified hydrogenated petroleum resin (a) satisfies the above (1) to (3).

[0014] In this specification, "petroleum resin" refers to a resin obtained by polymerizing or copolymerizing one or more unsaturated compounds selected from aliphatic olefins or aliphatic diolefins having 4 to 10 carbon atoms, which are obtained as by-products during the production of olefins such as ethylene by thermal decomposition of petroleum such as naphtha, or aromatic compounds having 8 or more carbon atoms and having an olefinically unsaturated bond. Petroleum resins can be broadly classified into, for example, "aliphatic petroleum resins" obtained by polymerizing aliphatic olefins or aliphatic diolefins, "aromatic petroleum resins" obtained by polymerizing aromatic compounds having an olefinically unsaturated bond, and "aliphatic-aromatic copolymer petroleum resins" obtained by copolymerizing aliphatic olefins or aliphatic diolefins with aromatic compounds having an olefinically unsaturated bond.

[0015] Examples of the aliphatic olefins having 4 to 10 carbon atoms include butene, pentene, hexene, and heptene. Examples of the aliphatic diolefins having 4 to 10 carbon atoms include butadiene, pentadiene, isoprene, piperylene, cyclopentadiene, dicyclopentadiene, and methylpentadiene. Examples of aromatic compounds having 8 or more carbon atoms and an olefinically unsaturated bond include styrene, α-methylstyrene, β-methylstyrene, vinyltoluene, vinylxylene, indene, methylindene, and ethylindene. Furthermore, it is not necessary for all of the raw material compounds for this petroleum resin to be by-products of olefin production by thermal decomposition of petroleum such as naphtha; chemically synthesized unsaturated compounds may also be used.

[0016] Preferable examples of petroleum resins include dicyclopentadiene-based petroleum resins obtained by polymerizing cyclopentadiene or dicyclopentadiene, dicyclopentadiene-styrene-based petroleum resins obtained by copolymerizing these cyclopentadiene or dicyclopentadiene with styrene, C5-based petroleum resins obtained by polymerizing isoprene or piperylene, and C9-based petroleum resins obtained by polymerizing C9 monomers such as indene or vinyltoluene.

[0017] In this specification, "hydrogenated petroleum resin" refers to a petroleum resin obtained by adding hydrogen atoms to the above-mentioned petroleum resin. Hydrogenated petroleum resins include fully hydrogenated petroleum resins in which substantially no unsaturated bonds remain and partially hydrogenated petroleum resins in which unsaturated bonds remain, with fully hydrogenated petroleum resins being preferred. As the hydrogenated petroleum resin, hydrogenated aliphatic-aromatic copolymer petroleum resins are preferred.

[0018] The modified hydrogenated petroleum resin (a) contains 0.5 to 20.0 mass% silicon element in terms of silicon atoms. The silicon element is preferably derived from an organosilane structure. The silicon element content can be measured by ICP atomic emission spectroscopy, specifically by the method described in the Examples. The modified hydrogenated petroleum resin (a) contains 0.5 to 20.0 mass% silicon element in terms of silicon atoms, preferably 0.5 to 10.0 mass%, more preferably 0.5 to 5.0 mass%, even more preferably 0.8 to 4.0 mass%, and even more preferably 0.8 to 1.8 mass%. The modified hydrogenated petroleum resin (a) is preferably a silane-modified hydrogenated petroleum resin having an organosilane structure. Among these, a modified hydrogenated petroleum resin in which an alkoxysilyl group is bonded to the main chain of the hydrogenated petroleum resin via a bonding moiety is preferred. Here, "the alkoxysilyl group is bonded to the main chain of the hydrogenated petroleum resin via a bond" means, for example, that a direct bond is bonded to a carbon atom contained in a hydrogenated polymer (hydrogenated petroleum resin) obtained by polymerizing aliphatic olefins, aliphatic diolefins, and an aromatic compound having an olefinically unsaturated bond, and adding a hydrogen atom, as described above, and that an alkoxysilyl group is further bonded to the carbon atom. As the alkoxysilyl group, a trialkoxysilyl group having an alkoxy group having 1 to 20 carbon atoms, which may be linear or branched, is preferred, and a trialkoxysilyl group having an alkoxy group having 1 to 10 carbon atoms, which may be linear or branched, is more preferred. Specific examples include a trimethoxysilyl group, a triethoxysilyl group, a tripropoxysilyl group, etc., and at least one selected from the group consisting of a trimethoxysilyl group and a triethoxysilyl group is preferred, with a trimethoxysilyl group being more preferred. The bonding portion may be any organic group having a valence of two or more that can bond to a carbon atom in the main chain of the hydrogenated petroleum resin and to which an alkoxysilyl group can be bonded, and is preferably an alkylene group, more preferably an alkylene group having 2 to 3 carbon atoms.

[0019] The weight average molecular weight (Mw) of the modified hydrogenated petroleum resin (a) is 500 to 5,000, preferably 600 to 3,000, more preferably 700 to 2,000, and even more preferably 800 to 1,500. The weight average molecular weight is an index of fluidity when melted; the smaller the weight average molecular weight, the greater the fluidity when melted, resulting in excellent spreadability and adhesion to aggregate surfaces while maintaining the water resistance that is the effect of the present invention. The weight average molecular weight can be measured specifically by the method described in the Examples.

[0020] The molecular weight distribution (weight average molecular weight / number average molecular weight, Mw / Mn) of the modified hydrogenated petroleum resin (a) is 1.1 to 3.5, preferably 1.3 to 3.0, more preferably 1.5 to 3.0, and even more preferably 2.0 to 2.5. The molecular weight distribution represents the degree of dispersion of molecular weight, and becomes broad when the amount of low molecular weight components or high molecular weight components is extremely large. The molecular weight distribution can be measured specifically by the method described in the examples.

[0021] The number average molecular weight (Mn) of the modified hydrogenated petroleum resin (a) is preferably 100 to 4,500, more preferably 250 to 2,500, and even more preferably 300 to 1,500.

[0022] The softening point of the modified hydrogenated petroleum resin (a) is preferably 60 to 150°C, more preferably 80 to 140°C, even more preferably 90 to 130°C, and even more preferably 98 to 120°C. The softening point can be measured by the ring and ball method, specifically by the method described in the examples. When the softening point is in the above range, an excellent balance between water resistance and adhesion to the aggregate surface is achieved.

[0023] [Method for producing modified hydrogenated petroleum resin (a)] There are no particular limitations on the method for producing the modified hydrogenated petroleum resin (a), but the following method is preferred from the viewpoint of efficiently introducing silane into the resin and improving water resistance. The method for producing the modified hydrogenated petroleum resin (a) is preferably a method in which a hydrogenated petroleum resin is reacted with a compound having a carbon-carbon double bond and an alkoxysilyl group in the presence of a compound that generates radicals.

[0024] The hydrogenated petroleum resin used in the production method is synonymous with the "hydrogenated petroleum resin" described above in the section [Modified hydrogenated petroleum resin (a)], and specifically, is a petroleum resin obtained by adding hydrogen atoms to a petroleum resin. Hydrogenated petroleum resins include fully hydrogenated petroleum resins in which substantially no unsaturated bonds remain, and partially hydrogenated petroleum resins in which unsaturated bonds remain, and the hydrogenated petroleum resin used in the production method of the present invention is preferably a fully hydrogenated petroleum resin. As the hydrogenated petroleum resin, hydrogenated aliphatic-aromatic copolymer petroleum resin is preferred.

[0025] The petroleum resin used as a raw material for hydrogenated petroleum resin has the same meaning as the "petroleum resin" described above in the section [Modified Hydrogenated Petroleum Resin (a)], and is specifically as follows. Petroleum resins are resins obtained by polymerizing or copolymerizing one or more unsaturated compounds selected from aliphatic olefins and aliphatic diolefins having 4 to 10 carbon atoms, which are obtained as by-products during the production of olefins such as ethylene by thermal decomposition of petroleum such as naphtha, or aromatic compounds having 8 or more carbon atoms and having an olefinically unsaturated bond. Petroleum resins can be broadly classified into, for example, "aliphatic petroleum resins" obtained by polymerizing aliphatic olefins and aliphatic diolefins, "aromatic petroleum resins" obtained by polymerizing aromatic compounds having an olefinically unsaturated bond, and "aliphatic-aromatic copolymer petroleum resins" obtained by copolymerizing aliphatic olefins and aliphatic diolefins with aromatic compounds having an olefinically unsaturated bond.

[0026] Examples of the aliphatic olefins having 4 to 10 carbon atoms include butene, pentene, hexene, and heptene. Examples of the aliphatic diolefins having 4 to 10 carbon atoms include butadiene, pentadiene, piperylene, isoprene, cyclopentadiene, dicyclopentadiene, and methylpentadiene. Examples of aromatic compounds having 8 or more carbon atoms and an olefinically unsaturated bond include styrene, α-methylstyrene, β-methylstyrene, vinyltoluene, vinylxylene, indene, methylindene, and ethylindene. Furthermore, it is not necessary for all of the raw material compounds for this petroleum resin to be by-products of olefin production by thermal decomposition of petroleum such as naphtha; chemically synthesized unsaturated compounds may also be used.

[0027] Preferable examples of petroleum resins include dicyclopentadiene-based petroleum resins obtained by polymerizing cyclopentadiene or dicyclopentadiene, dicyclopentadiene-styrene-based petroleum resins obtained by copolymerizing these cyclopentadiene or dicyclopentadiene with styrene, C5-based petroleum resins obtained by polymerizing isoprene or piperylene, and C9-based petroleum resins obtained by polymerizing C9 monomers such as indene or vinyltoluene.

[0028] The compound having a carbon-carbon double bond and an alkoxysilyl group used in the production method is a compound in which one or more organic groups having a carbon-carbon double bond and one or more alkoxy groups are bonded to a silicon atom. Examples of the organic group having a carbon-carbon double bond include vinyl, allyl, butenyl, cyclohexenyl, cyclopentadienyl, and (meth)acryloxypropyl, with vinyl, methacryloxy, and acryloxy groups being preferred. Examples of the alkoxy group include methoxy, ethoxy, isopropoxy, and butoxy. One or more alkoxy groups are preferably bonded to the silicon atom, more preferably two or more, and even more preferably three. Specific examples of the compound having a carbon-carbon double bond and an alkoxysilyl group include vinyltriethoxysilane, vinyltrimethoxysilane, methacryloxypropyltrimethoxysilane, and methacryloxypropyltriethoxysilane. At least one selected from the group consisting of vinyltriethoxysilane and vinyltrimethoxysilane is preferred, with vinyltrimethoxysilane being more preferred. The amount of the compound having a carbon-carbon double bond and an alkoxysilyl group used in the production method is, in terms of silicon atoms of the compound having a carbon-carbon double bond and an alkoxysilyl group, preferably 0.5 to 20.0 mass%, more preferably 0.5 to 10.0 mass%, even more preferably 0.5 to 5.0 mass%, still more preferably 0.8 to 4.0 mass%, even more preferably 0.8 to 1.8 mass%, relative to the hydrogenated petroleum resin.

[0029] The radical-generating compound used in the production method can be a compound generally known as a radical polymerization initiator. The radical-generating compound can be appropriately selected from, for example, various organic peroxides and azo compounds such as azobisisobutyronitrile and azobisisovaleronitrile, and among these, organic peroxides are preferred. Examples of organic peroxides include diacyl peroxides such as dibenzoyl peroxide, di-3,5,5-trimethylhexanoyl peroxide, dilauroyl peroxide, didecanoyl peroxide, and di(2,4-dichlorobenzoyl)peroxide; hydroperoxides such as t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, and 2,5-dimethylhexane-2,5-dihydroperoxide; di-t-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 1,1-di(t-butylperoxy)cyclohexane, 1,1-di(t-hexylperoxy)cyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, and α,α'-bis(t-butylperoxy). peroxyketals such as 1,1-bis-t-butylperoxy-3,3,5-trimethylcyclohexane and 2,2-bis(t-butylperoxy)butane; alkyl peresters such as 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, n-butyl 4,4-di(t-butylperoxy)valerate, t-butylperoxyoctoate, t-butylperoxypivalate, t-butylperoxyneodecanoate, and t-butylperoxybenzoate; and peroxycarbonates such as di-2-ethylhexylperoxydicarbonate, diisopropylperoxydicarbonate, di-sec-butylperoxydicarbonate, and t-butylperoxyisopropylcarbonate. Among these, dialkyl peroxides are preferred. These may be used alone or in combination of two or more.The amount of the radical-generating compound used is not particularly limited, but is preferably 0.01 to 10% by mass, more preferably 0.01 to 5% by mass, based on the hydrogenated petroleum resin.

[0030] As described above, a suitable method for producing the modified hydrogenated petroleum resin (a) is a method of reacting a hydrogenated petroleum resin with a compound having a carbon-carbon double bond and an alkoxysilyl group in the presence of a compound that generates radicals. There are no limitations on the reaction method as long as the reaction proceeds sufficiently. However, (1) a method of mixing molten hydrogenated petroleum resin, a compound having a carbon-carbon double bond and an alkoxysilyl group, and a compound that generates radicals, and generating radicals by heating or the like, to cause the reaction, is preferred. (2) A method of dissolving a hydrogenated petroleum resin, a compound having a carbon-carbon double bond and an alkoxysilyl group, and a compound that generates radicals in an organic solvent, and generating radicals by heating or the like, to cause the reaction, is more preferred. (1) A method of mixing molten hydrogenated petroleum resin, a compound having a carbon-carbon double bond and an alkoxysilyl group, and a compound that generates radicals, and generating radicals by heating or the like, to cause the reaction, is more preferred.

[0031] In the case of the method (1) above, it is preferable to melt the hydrogenated petroleum resin, mix it with a compound having a carbon-carbon double bond and an alkoxysilyl group, add a compound that generates radicals, and heat it to react the hydrogenated petroleum resin with the carbon-carbon double bond portion of the compound having a carbon-carbon double bond and an alkoxysilyl group to obtain a modified hydrogenated petroleum resin. In this method, if the melt viscosity of the hydrogenated petroleum resin is low, it is preferable to carry out the reaction while stirring in a conventional reaction apparatus, and if the melt viscosity of the hydrogenated petroleum resin is high, it is preferable to carry out the reaction while melt-kneading using a roll mill, Banbury mixer, extruder, or the like. The reaction temperature is preferably 100 to 300°C, more preferably 100 to 200°C.

[0032] In the case of the method (2), it is preferable to dissolve the hydrogenated petroleum resin in an organic solvent, mix it with a compound having a carbon-carbon double bond and an alkoxysilyl group, add a compound that generates radicals, and heat it to react the hydrogenated petroleum resin with the carbon-carbon double bond portion of the compound having a carbon-carbon double bond and an alkoxysilyl group to obtain a modified hydrogenated petroleum resin. Examples of organic solvents that can be used in this method include hydrocarbon solvents such as pentane, hexane, heptane, cyclohexane, toluene, xylene, and decahydronaphthalene, halogenated hydrocarbon solvents such as chlorobenzene, dichlorobenzene, and trichlorobenzene, and liquefied α-olefins. The reaction temperature is preferably −50 to 300°C, more preferably 0 to 300°C, even more preferably 100 to 300°C, and even more preferably 100 to 200°C.

[0033] [Straight Asphalt (b)] The straight asphalt (b) can be asphalt or a mixture thereof specified in JIS K 2207. It is preferable to use straight asphalt having a penetration grade of 40 to 60 to 200 to 300.

[0034] [Composition and Production Method of Asphalt Masterbatch] The asphalt masterbatch contains 10 to 50 mass% of modified hydrogenated petroleum resin (a) and straight asphalt (b). The content of modified hydrogenated petroleum resin (a) in the asphalt masterbatch is 10 to 50 mass%, preferably 15 to 50 mass%, more preferably 15 to 45 mass%, even more preferably 20 to 45 mass%, still more preferably 20 to 40 mass%, even more preferably 25 to 40 mass%, and still more preferably 25 to 35 mass%.

[0035] The mass ratio [(a) / (b)] of the modified hydrogenated petroleum resin (a) to the straight asphalt (b) in the asphalt masterbatch is preferably 10 / 90 to 50 / 50, more preferably 15 / 85 to 50 / 50, even more preferably 15 / 85 to 45 / 55, still more preferably 20 / 80 to 45 / 55, still more preferably 20 / 80 to 40 / 60, still more preferably 25 / 75 to 40 / 60, and still more preferably 25 / 75 to 35 / 65.

[0036] The content of straight asphalt (b) in the asphalt masterbatch is preferably 50 to 90% by mass, more preferably 50 to 85% by mass, even more preferably 55 to 85% by mass, still more preferably 55 to 80% by mass, still more preferably 60 to 80% by mass, still more preferably 60 to 75% by mass, and still more preferably 65 to 75% by mass.

[0037] By setting the content and mass ratio of the modified hydrogenated petroleum resin (a) and the straight asphalt (b) within the above ranges, the water resistance improving effect of the modified hydrogenated petroleum resin can be efficiently brought out, and an asphalt mixture with excellent water resistance can be obtained.

[0038] In addition to the modified hydrogenated petroleum resin (a) and the straight asphalt (b), the asphalt masterbatch may contain any additives within the range that does not impair the effects of the present invention. Furthermore, the asphalt base oil and reinforcing material ultimately contained in the asphalt mixture may also be contained within the range that does not impair the effects of the present invention. Examples of optional additives include antioxidants.

[0039] An antioxidant may be added for the purpose of enhancing thermal stability. Known antioxidants can be used. It is preferable to use a phenolic antioxidant as the antioxidant. Examples of phenolic antioxidants include triethylene glycol bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,5-di-tert- Examples of such an alkyl ester include butyl-4-hydroxybenzylphosphonate-diethyl ester, N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide), 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, and 3,9-bis[2-{3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane. Commercially available antioxidants that can be used include pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (IRGANOX1010, manufactured by BASF Corporation) and 1,3,5-tris-(3′,5′-di-tert-butyl-4′-hydroxybenzyl)isocyanuric acid (ADK STAB AO-20, manufactured by ADEKA Corporation).

[0040] The asphalt masterbatch contains, in terms of silicon atoms, preferably 0.10 to 0.60 mass%, more preferably 0.13 to 0.50 mass%, even more preferably 0.13 to 0.45 mass%, still more preferably 0.13 to 0.40 mass%, still more preferably 0.15 to 0.40 mass%, still more preferably 0.20 to 0.40 mass%, still more preferably 0.20 to 0.30 mass%, and still more preferably 0.20 to 0.27 mass% of silicon element. From the viewpoint of more efficiently improving water resistance in terms of the amount of masterbatch used, the asphalt masterbatch more preferably contains 0.15 to 0.50 mass% of silicon element, more preferably 0.20 to 0.50 mass%, even more preferably 0.20 to 0.50 mass%, even more preferably 0.30 to 0.50 mass% of silicon element. In the production method of the present invention, an asphalt masterbatch containing the above-mentioned amount of silicon element can be used, so that the water resistance improving effect of the modified hydrogenated petroleum resin can be efficiently brought out, and an asphalt mixture having excellent water resistance can be obtained.

[0041] There is no limitation on the method for producing the asphalt masterbatch, but it can be obtained as follows.

[0042] Specifically, modified hydrogenated petroleum resin (a) and straight asphalt (b) are heated and mixed to obtain a mixture. The aforementioned additives, as well as the asphalt base oil and reinforcing material contained in the asphalt mixture described below, may also be mixed. Heat mixing is preferably performed using a stirring device, for example, at 100°C or higher. The heating temperature is preferably 100°C or higher, and although there is no upper limit, 200°C or lower is preferred. The heating temperature is preferably 100 to 200°C, more preferably 100 to 180°C, even more preferably 100 to 170°C, even more preferably 100 to 160°C, and even more preferably 140 to 160°C. The resulting mixture can be pulverized, pelletized, or the like to obtain an asphalt masterbatch in the form of a block or pellet.

[0043] (Asphalt Masterbatch Mixing Conditions) This step is a step in which 0.03 to 4 parts by mass of asphalt masterbatch is mixed with 100 parts by mass of aggregate at 100 to 200° C. The amount of asphalt masterbatch used in the mixing is 0.03 to 4 parts by mass, preferably 0.03 to 3 parts by mass, more preferably 0.03 to 2 parts by mass, even more preferably 0.04 to 2 parts by mass, still more preferably 0.04 to 1.0 part by mass, still more preferably 0.04 to 0.5 parts by mass, still more preferably 0.05 to 0.10 parts by mass, and still more preferably 0.05 to 0.08 parts by mass, with respect to 100 parts by mass of aggregate. The temperature at which the asphalt masterbatch is mixed with the aggregate is 100 to 200°C, and from the viewpoint of suppressing the progression of crosslinking of the modified hydrogenated petroleum resin at high temperatures, it is preferably 100 to 180°C, more preferably 100 to 170°C, even more preferably 100 to 160°C, and even more preferably 140 to 160°C. Mixing at 160°C or less is particularly preferable because it makes it possible to suppress crosslinking even when a high concentration of modified hydrogenated petroleum resin is used. Therefore, by mixing within the above temperature range, an asphalt mixture with excellent water resistance can be obtained.

[0044] The amount of the asphalt masterbatch and the amount of the modified hydrogenated petroleum resin (a) contained in the asphalt masterbatch are preferably adjusted taking into account the silicon content of the asphalt mixture. Preferably, they are adjusted taking into account the silicon content of the entire asphalt mixture, including the amount of asphalt (c) in the next step. The silicon content referred to here refers to the silicon contained only in the modified hydrogenated petroleum resin (a), and does not include the silicon contained in aggregates, etc. The asphalt mixture contains, in terms of silicon atoms, preferably 1.0 to 6.0 ppm by mass of silicon element contained in the modified hydrogenated petroleum resin (a), more preferably 1.3 to 5.0 ppm by mass, even more preferably 1.3 to 4.5 ppm by mass, even more preferably 1.3 to 4.0 ppm by mass, even more preferably 1.5 to 4.0 ppm by mass, even more preferably 2.0 to 4.0 ppm by mass, even more preferably 2.0 to 3.0 ppm by mass, and even more preferably 2.0 to 2.7 ppm by mass. By containing the above-mentioned amount of silicon element contained in the modified hydrogenated petroleum resin (a) in the asphalt mixture, the water resistance improving effect of the modified hydrogenated petroleum resin can be efficiently brought out, and an asphalt mixture with excellent water resistance can be obtained.

[0045] In this process, the asphalt masterbatch is added to aggregate having a predetermined particle size and mixed at a predetermined rotation speed to obtain a mixture of the asphalt masterbatch and aggregate. The optional additives described above that may be contained in the asphalt masterbatch may be added when mixing the asphalt masterbatch and aggregate. By performing this process under the above conditions, the aggregate surface can be coated with the modified hydrogenated petroleum resin and straight asphalt, thereby efficiently utilizing the water resistance-improving effect of the modified hydrogenated petroleum resin and obtaining an asphalt mixture with excellent water resistance.

[0046] <Asphalt Addition and Mixing Step> The method for producing an asphalt mixture of the present invention further comprises a step of adding and mixing asphalt (c) after the asphalt masterbatch mixing step. This step allows for the production of an asphalt mixture that has excellent water resistance.

[0047] (Asphalt (c)) Examples of the asphalt (c) used in this step include straight asphalt, solvent deasphalt such as propane deasphalt, blown asphalt, and semi-blown asphalt, and these may be used in combination.

[0048] Straight asphalt can be asphalt specified in JIS K 2207 or a mixture thereof. It is preferable to use straight asphalt equivalent to a penetration grade of 40-60 to 200-300. Solvent deasphalted asphalt corresponds to the residue obtained by extracting solvent deasphalted oil (high-viscosity lubricating oil fraction) from vacuum distillation residual oil (see "New Petroleum Dictionary," edited by the Japan Petroleum Institute, 1982, p. 308). When propane or propane and butane are used as the solvent, it is called propane deasphalted asphalt. Blown asphalt is, for example, asphalt specified in JIS K 2207. Semi-blown asphalt is, for example, semi-blown asphalt specified in "Asphalt Pavement Guidelines," published by the Japan Road Association, January 13, 1997, p. 51, Table 3.3.4. In this step, in addition to asphalt (c), aromatic heavy mineral oil and reinforcing material may be used. Aromatic heavy mineral oil and reinforcing material may be used appropriately depending on the environment in which the asphalt mixture of the present invention is used, etc. The aromatic heavy mineral oil and reinforcing material used in this step are contained in the resulting asphalt mixture. Furthermore, in addition to asphalt (c), aromatic heavy mineral oil and reinforcing material, any additive may be used within a range that does not impair the effects of the present invention. The any additive used in this step is contained in the resulting asphalt mixture.

[0049] (Aromatic heavy mineral oil) The aromatic heavy mineral oil can be a solvent-extracted oil obtained by deasphalting the residual oil of vacuum distillation of crude oil with propane or the like, and then subjecting the solvent-deasphalted oil to solvent extraction with a polar solvent such as furfural to obtain bright stock (heavy lubricating oil). It is preferable to add an extract as the aromatic heavy mineral oil.

[0050] The role of the extract is to increase the solubility of the thermoplastic elastomer in asphalt and prevent separation during storage stability, so the amount of extract required increases as the amount of thermoplastic elastomer added increases. Also, adding more extract than necessary compared to the amount of thermoplastic elastomer added will decrease the elastic modulus of the asphalt (composition).

[0051] The content of the extract is determined taking into consideration the penetration, softening point, storage stability, complex modulus of elasticity indicating strength, dynamic stability (DS) in a wheel tracking test, and bending work and bending stiffness indicating low-temperature properties. The amount of extract relative to the total of straight asphalt (b), asphalt (c), aromatic heavy mineral oil, and reinforcing material is preferably 2.0% by mass or more and 8.0% by mass or less, but the extract need not be used.

[0052] (Reinforcing Material) A thermoplastic elastomer may be used as the reinforcing material. Among thermoplastic elastomers, SBS (styrene-butadiene-styrene copolymer) is preferred. The performance of SBS can be estimated mainly from its molecular weight and styrene content. The styrene content here refers to the mass % of styrene contained in SBS.

[0053] Currently, the weight-average molecular weight of SBS that is easily available industrially is from 120,000 to 250,000. The styrene content of SBS is from 25.0 to 35.0% by mass, preferably from 27.0 to 33.0% by mass, of the total SBS.

[0054] In addition to the above, SBS with different molecular weights and styrene contents are available, and the molecular weight of these SBS is from 80,000 to 90,000. Furthermore, the styrene content is from 25.0 to 50.0% by mass of the total SBS.

[0055] Although SBS is not required, if SBS is used, the amount of SBS relative to the total of straight asphalt (b), asphalt (c), aromatic heavy mineral oil, and reinforcing material is preferably 7.0% by mass or less. By setting the SBS content to 7.0% by mass or less, it is possible to maintain the asphalt continuous phase and improve the water resistance of a dense-graded mixture with excellent water impermeability. On the other hand, if it is desired to produce an asphalt mixture with high drainage or permeability by intentionally creating voids within the pavement, by setting the SBS content to more than 7.0% by mass, a phase transition of the SBS will occur, allowing the production of an asphalt mixture with high drainage or permeability.

[0056] The SBS may be a mixture of only one type of SBS, or two or more types of SBS having specific molecular structures may be selected and mixed. Mixing only one type of SBS is preferable because it eliminates the complexity of selecting and mixing two or more types of SBS and enables a reduction in manufacturing labor.

[0057] (Optional Additives) In this step, in addition to the asphalt (c), aromatic heavy mineral oil, and reinforcing material, any additives may be used as long as they do not impair the effects of the present invention.

[0058] Optional additives include petroleum resins and hydrogenated petroleum resins obtained by adding hydrogen atoms to petroleum resins. Petroleum resins are resins obtained by polymerizing or copolymerizing one or more unsaturated compounds selected from aliphatic olefins and aliphatic diolefins having 4 to 10 carbon atoms, which are obtained as by-products during the production of olefins such as ethylene by thermal decomposition of petroleum such as naphtha, or aromatic compounds having 8 or more carbon atoms and having an olefinically unsaturated bond. Petroleum resins can be broadly classified into, for example, "aliphatic petroleum resins" obtained by polymerizing aliphatic olefins and aliphatic diolefins, "aromatic petroleum resins" obtained by polymerizing aromatic compounds having an olefinically unsaturated bond, and "aliphatic-aromatic copolymer petroleum resins" obtained by copolymerizing aliphatic olefins and aliphatic diolefins with aromatic compounds having an olefinically unsaturated bond. Examples of these aliphatic olefins having 4 to 10 carbon atoms include butene, pentene, hexene, and heptene. Examples of aliphatic diolefins having 4 to 10 carbon atoms include butadiene, pentadiene, isoprene, piperylene, cyclopentadiene, dicyclopentadiene, and methylpentadiene. Examples of aromatic compounds having 8 or more carbon atoms and an olefinically unsaturated bond include styrene, α-methylstyrene, β-methylstyrene, vinyltoluene, vinylxylene, indene, methylindene, and ethylindene. It is not necessary for all of the raw material compounds for this petroleum resin to be by-products of olefin production by thermal decomposition of petroleum such as naphtha; chemically synthesized unsaturated compounds may also be used. Suitable examples of petroleum resins include dicyclopentadiene-based petroleum resins obtained by polymerizing cyclopentadiene or dicyclopentadiene, dicyclopentadiene-styrene-based petroleum resins obtained by copolymerizing these cyclopentadiene or dicyclopentadiene with styrene, C5-based petroleum resins obtained by polymerizing isoprene or piperylene, and C9-based petroleum resins obtained by polymerizing C9 monomers such as indene or vinyltoluene. Hydrogenated petroleum resins are petroleum resins obtained by adding hydrogen atoms to the above-mentioned petroleum resins, and include fully hydrogenated petroleum resins in which substantially no unsaturated bonds remain and partially hydrogenated petroleum resins in which unsaturated bonds remain, with partially hydrogenated petroleum resins being preferred.

[0059] Furthermore, examples of optional additives include polyethylene-based polyolefins, such as Hi-Zex 1300J, Neo-Zex 20201J, and Ult-Zex 15150J (manufactured by Prime Polymer Co., Ltd.), and Affinity GA1950 and Affinity GA1900H (manufactured by Dow).

[0060] Other optional additives include antioxidants. The antioxidant may be added for the purpose of increasing thermal stability. Known antioxidants can be used. It is preferable to use a phenolic antioxidant as the antioxidant. Examples of phenolic antioxidants include triethylene glycol bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,5-di-tert- Examples of such an alkyl ester include butyl-4-hydroxybenzylphosphonate-diethyl ester, N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide), 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, and 3,9-bis[2-{3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane. Commercially available antioxidants that can be used include pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (IRGANOX1010, manufactured by BASF Corporation) and 1,3,5-tris-(3′,5′-di-tert-butyl-4′-hydroxybenzyl)isocyanuric acid (ADK STAB AO-20, manufactured by ADEKA Corporation).

[0061] (Asphalt Addition and Mixing Conditions) This process is a process in which asphalt (c) is further added and mixed after the asphalt masterbatch mixing process. The amount of asphalt (c) added is preferably adjusted taking into account the amount of straight asphalt (b) contained in the asphalt masterbatch. In other words, if a large amount of straight asphalt (b) is used in the previous process, it is preferable to reduce the amount of asphalt (c) added in this process to adjust the amount of asphalt in the entire asphalt mixture.

[0062] The total amount of asphalt (c) and straight asphalt (b) is preferably 3 to 10 parts by mass, more preferably 3 to 9 parts by mass, even more preferably 3 to 8 parts by mass, still more preferably 3 to 7 parts by mass, even more preferably 3 to 6 parts by mass, and still more preferably 4 to 6 parts by mass, relative to 100 parts by mass of aggregate.

[0063] In this process, asphalt (c) is added to a mixture of aggregate and asphalt masterbatch, and the mixture is mixed at a predetermined rotation speed to obtain an asphalt mixture. The aromatic heavy mineral oil, reinforcing material, and optional additives may be mixed simultaneously with asphalt (c), or may be mixed with asphalt (c) in advance and then mixed with the mixture to form an asphalt composition. The temperature when mixing asphalt (c) and the mixture is preferably 100 to 200°C, more preferably 100 to 180°C, more preferably 100 to 170°C, even more preferably 100 to 160°C, and even more preferably 140 to 160°C. By performing this process under the above conditions, the aggregate surface can be coated with the modified hydrogenated petroleum resin and straight asphalt, and the water resistance-improving effect of the modified hydrogenated petroleum resin can be efficiently utilized, resulting in an asphalt mixture with excellent water resistance.

[0064] The asphalt mixture obtained as described above may be temporarily stored in a temperature-controlled container so as to maintain a predetermined temperature.

[0065] <Asphalt Mixture> The asphalt mixture obtained by the asphalt mixture manufacturing method of the present invention preferably has the following composition: The asphalt mixture contains modified hydrogenated petroleum resin (a), straight asphalt (b), and asphalt (c), and may also contain optional additives, aromatic heavy mineral oil, reinforcing materials, etc.

[0066] The asphalt mixture contains, in terms of silicon atoms, preferably 1.0 to 6.0 ppm by mass of silicon element contained in the modified hydrogenated petroleum resin (a), more preferably 1.3 to 5.0 ppm by mass, even more preferably 1.3 to 4.5 ppm by mass, even more preferably 1.3 to 4.0 ppm by mass, even more preferably 1.5 to 4.0 ppm by mass, even more preferably 2.0 to 4.0 ppm by mass, even more preferably 2.0 to 3.0 ppm by mass, and even more preferably 2.0 to 2.7 ppm by mass. By containing the above-mentioned amount of silicon element contained in the modified hydrogenated petroleum resin (a) in the asphalt mixture, the water resistance improving effect of the modified hydrogenated petroleum resin can be efficiently brought out, and an asphalt mixture with excellent water resistance can be obtained.

[0067] The total amount of asphalt (c) and straight asphalt (b) contained in the asphalt mixture is preferably 3 to 10 parts by mass, more preferably 3 to 9 parts by mass, even more preferably 3 to 8 parts by mass, still more preferably 3 to 7 parts by mass, still more preferably 3 to 6 parts by mass, and still more preferably 4 to 6 parts by mass, relative to 100 parts by mass of aggregate.

[0068] The total amount of the modified hydrogenated petroleum resin (a) and straight asphalt (b) contained in the asphalt mixture is 0.03 to 4 parts by mass, preferably 0.03 to 3 parts by mass, more preferably 0.03 to 2 parts by mass, even more preferably 0.04 to 2 parts by mass, still more preferably 0.04 to 1.0 part by mass, still more preferably 0.04 to 0.5 parts by mass, still more preferably 0.05 to 0.10 parts by mass, and still more preferably 0.05 to 0.08 parts by mass, relative to 100 parts by mass of aggregate.

[0069] The content of the modified hydrogenated petroleum resin (a) relative to the total content of the modified hydrogenated petroleum resin (a) and the straight asphalt (b) is 10 to 50 mass%, preferably 15 to 50 mass%, more preferably 15 to 45 mass%, even more preferably 20 to 45 mass%, still more preferably 20 to 40 mass%, still more preferably 25 to 40 mass%, and still more preferably 25 to 35 mass%.

[0070] The mass ratio of the modified hydrogenated petroleum resin (a) to the straight asphalt (b) [(a) / (b)] is preferably 10 / 90 to 50 / 50, more preferably 15 / 85 to 50 / 50, even more preferably 15 / 85 to 45 / 55, still more preferably 20 / 80 to 45 / 55, still more preferably 20 / 80 to 40 / 60, still more preferably 25 / 75 to 40 / 60, and still more preferably 25 / 75 to 35 / 65.

[0071] The content of straight asphalt (b) relative to the total content of modified hydrogenated petroleum resin (a) and straight asphalt (b) is preferably 50 to 90% by mass, more preferably 50 to 85% by mass, even more preferably 55 to 85% by mass, still more preferably 55 to 80% by mass, still more preferably 60 to 80% by mass, still more preferably 60 to 75% by mass, and still more preferably 65 to 75% by mass.

[0072] The asphalt mixture is obtained by the above-described method for producing an asphalt mixture and has the above-described composition, so that the water resistance improving effect of the modified hydrogenated petroleum resin can be efficiently brought out, and an asphalt mixture with excellent water resistance can be obtained.

[0073] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples in any way.

[0074] [Analysis of Modified Hydrogenated Petroleum Resin] [1. Silicon Content] 0.1 g of sample (resin) was heated in an electric furnace at 550°C for 12 hours, and a measurement solution was prepared by alkali fusion of the ash. ICP atomic emission spectroscopy was performed using an ICP atomic emission spectroscopy analyzer "720-ES" (manufactured by Agilent Technologies Inc.) to determine the silicon content in terms of silicon atoms. The silicon content derived from the modified hydrogenated petroleum resin in the asphalt masterbatch, the silicon content derived from the modified hydrogenated petroleum resin in the asphalt composition, and the silicon content derived from the modified hydrogenated petroleum resin in the asphalt mixture were calculated using the silicon content derived from the modified hydrogenated petroleum resin obtained above in terms of silicon atoms.

[0075] [2. Molecular Weight and Molecular Weight Distribution] The average molecular weight of the resin was measured by gel permeation chromatography (GPC). For the measurement, a GPC measurement device "HLC-8321GPC / HT" (manufactured by Tosoh Technosystems Corporation) was used, as a detector, a liquid chromatogram RI detector "WATERS 150C" (manufactured by Waters Corporation), two TOSOH GMHHR-H(S)HT columns, and 1,2,4-trichlorobenzene was used as an eluent. The number average molecular weight (Mn) and weight average molecular weight (Mw) in terms of polystyrene were determined, and the molecular weight distribution (Mw / Mn) of the resin was calculated.

[0076] 3. Softening Point: Measured in accordance with JIS K 6863.

[0077] [Analysis and Evaluation of Asphalt Mixtures] [1. Evaluation of Peeling Resistance (Evaluation of Water Resistance)] This evaluation was performed for each Example and Comparative Example. Ten asphalt mixtures were selected and placed in 100 mL of a 1.0 mol / L aqueous sodium carbonate solution. The aqueous solution was then heated on a hot plate, and heated for 1 minute after reaching 90°C. After cooling, the top surface of the asphalt mixture was visually observed, and the peeled area ratio of the asphalt covering the surface of the aggregate was calculated and expressed as a percentage (%). Evaluation was also performed according to the following criteria. The smaller the peeled area ratio on the top surface of the asphalt mixture, the more suppressed is the peeling of the asphalt, and the better the water resistance of the asphalt mixture. A: Peeled area ratio is 10% or less B: Peeled area ratio is more than 10% and less than 30% C: Peeled area ratio is more than 30%

[0078] [Production of Modified Hydrogenated Petroleum Resin] Production Example 1 100 g of hydrogenated petroleum resin (trade name "Imarve P-100" manufactured by Idemitsu Kosan Co., Ltd.) was placed in a 500 mL separable flask equipped with a nitrogen inlet tube and a stirring blade, and heated to 160 ° C. in an oil bath under a nitrogen stream and melted. Once the hydrogenated petroleum resin was dissolved, 3.2 g of vinyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) was added with stirring, and the mixture was stirred until homogeneous. Next, 0.69 g of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (trade name "Perhexa (registered trademark) 25B" manufactured by NOF Corporation) was added dropwise as an organic peroxide. After the dropwise addition, the mixture was allowed to react for 1 hour at an internal temperature (reaction mixture temperature) of 160 ° C. After completion of the reaction, the mixture was left to dry under reduced pressure with stirring at 150 ° C. for 1 hour to obtain modified hydrogenated petroleum resin a. The analysis and evaluation results of the obtained modified hydrogenated petroleum resin a are shown in Table 1.

[0079] Production Example 2 Modified hydrogenated petroleum resin b was obtained in the same manner as in Production Example 1, except that the amount of vinyltrimethoxysilane in Production Example 1 was changed to 4.7 g. The analysis and evaluation results of the obtained modified hydrogenated petroleum resin b are shown in Table 1.

[0080] Production Example 3 Modified hydrogenated petroleum resin c was obtained in the same manner as in Production Example 1, except that the amount of vinyltrimethoxysilane in Production Example 1 was changed to 8.3 g. The analysis and evaluation results of the obtained modified hydrogenated petroleum resin c are shown in Table 1.

[0081] Production Example 4 Modified hydrogenated petroleum resin d was obtained in the same manner as in Production Example 1, except that the amount of vinyltrimethoxysilane in Production Example 1 was changed to 10.0 g. The analysis and evaluation results of the obtained modified hydrogenated petroleum resin d are shown in Table 1.

[0082]

[0083] [Production of Asphalt Masterbatch] Production Examples 5 to 9 The modified hydrogenated petroleum resins obtained in Production Examples 1 to 4 and straight asphalt (manufactured by Idemitsu Kosan Co., Ltd., penetration 72) were charged into a 200 mL stainless steel cylindrical container in the proportions shown in Table 2, and the mixture was stirred and mixed for 15 minutes using a stirring device and a mantle heater at 160°C and a rotation speed of 2,000 rpm or more and 4,000 rpm or less to obtain the asphalt masterbatches shown in Table 2.

[0084]

[0085] [Production of Asphalt Mixture] Example 1 (Asphalt Masterbatch Mixing Step) Hard sandstone aggregate (No. 6 crushed stone) was washed with water and dried. The asphalt masterbatch A obtained in Production Example 5 was heated at 160°C for 1 hour. Then, 0.1 g of asphalt masterbatch A was added to 95 g of hard sandstone aggregate and stirred for 3 minutes to obtain a mixture of asphalt masterbatch and aggregate. (Asphalt Addition and Mixing Step) Next, 4.9 g of straight asphalt was added to the total mixture of asphalt masterbatch and aggregate (95.1 g) and stirred for 3 minutes to obtain an asphalt mixture. The composition and evaluation results of the obtained asphalt mixture are shown in Table 3.

[0086] Examples 2 to 4 (Asphalt Masterbatch Mixing Step) Asphalt mixtures were obtained in the same manner as in Example 1, except that the asphalt masterbatch used in the asphalt masterbatch mixing step in Example 1 was changed to the type and amount of the masterbatch shown in Table 3. The composition and evaluation results of the obtained asphalt mixtures are shown in Table 3.

[0087] Comparative Example 1: No. 6 crushed hard sandstone aggregate was washed with water and dried, and the asphalt composition obtained in Production Example 9 was heated at 180°C for 1 hour. 5.0 g of the asphalt composition was added to 95 g of the hard sandstone aggregate and stirred for 3 minutes to obtain an asphalt mixture. The composition and evaluation results of the obtained asphalt mixture are shown in Table 3.

[0088]

[0089] The results in Table 3 show that the asphalt mixtures obtained by the asphalt mixture manufacturing methods of the examples have excellent peeling resistance after hot water treatment. Therefore, the asphalt mixtures obtained by the asphalt mixture manufacturing method of the present invention can efficiently bring out the water resistance-improving effect of the modified hydrogenated petroleum resin, and therefore have a high peeling prevention effect. In addition, since a higher concentration of modified hydrogenated petroleum resin than conventional can be used while suppressing unnecessary reactions such as crosslinking, a higher peeling prevention effect is achieved. As described above, the asphalt mixture manufacturing method of the present invention can efficiently bring out the water resistance-improving effect of the additives, and can produce an asphalt mixture with excellent water resistance.

Claims

1. A method for producing an asphalt mixture, comprising the steps of mixing 0.03 to 4 parts by mass of an asphalt master batch with 100 parts by mass of aggregate at 100 to 200°C, and further adding and mixing asphalt (c), wherein the asphalt master batch contains 10 to 50% by mass of a modified hydrogenated petroleum resin (a) that satisfies the following (1) to (3), and straight asphalt (b): (1) Contains 0.5 to 20.0% by mass of silicon atom equivalent; (2) Weight average molecular weight is 500 to 5,000; (3) Molecular weight distribution (Mw / Mn) is 1.1 to 3.

5.

2. The method for producing an asphalt mixture according to claim 1, wherein the softening point of the modified hydrogenated petroleum resin (a) is 60 to 150°C.

3. The method for producing an asphalt mixture according to claim 1 or 2, wherein the mass ratio [(a) / (b)] of the modified hydrogenated petroleum resin (a) to the straight asphalt (b) in the asphalt masterbatch is 10 / 90 to 50 / 50.

4. The method for producing an asphalt mixture according to any one of claims 1 to 3, wherein the total amount of the asphalt (c) and the straight asphalt (b) is 3 to 10 parts by mass per 100 parts by mass of the aggregate.

5. The method for producing an asphalt mixture according to any one of claims 1 to 4, wherein the asphalt mixture contains 1.3 to 4.0 ppm by mass of silicon atom contained in the modified hydrogenated petroleum resin (a).

6. An asphalt master batch for use in the method for producing an asphalt mixture according to any one of claims 1 to 5, comprising 10 to 50 mass% of modified hydrogenated petroleum resin (a) and straight asphalt (b) that satisfy the following (1) to (3): (1) Contains 0.5 to 20.0 mass% silicon element calculated as silicon atom; (2) Has a weight average molecular weight of 500 to 5,000; and (3) Has a molecular weight distribution (Mw / Mn) of 1.1 to 3.5.

Images