WO2025197595A1 - Asphalt modifier - Google Patents

Abstract

The present invention relates to an asphalt modifier that includes a resin A and carbon black, the carbon black content being no more than 2.5 mass%, and the mass ratio (inorganic filler/carbon black) of inorganic filler (excluding carbon black) to carbon black being no more than 1.

Description

Asphalt modifier

The present invention relates to an asphalt modifier, an asphalt composition, and a method for producing an asphalt composition.

Asphalt pavement, which uses an asphalt mixture obtained by adding aggregate to an asphalt composition (asphalt binder), is used to pave roads, parking lots, freight yards, sidewalks, etc., because it is relatively easy to lay and the time between the start of paving work and the start of traffic is short. Because the road surface of this asphalt pavement is formed from an asphalt mixture in which aggregate is bound with asphalt, the paved road has good hardness and durability.

For example, Patent Document 1 (JP 2004-256663 A) describes an asphalt binder and paving asphalt mixture that can be used over a wider temperature range and that can be easily and inexpensively provided to improve the rut resistance and crack resistance of straight asphalt, which accounts for the majority of road paving asphalt, and that contains up to 30 parts by weight of carbon black with a nitrogen adsorption specific surface area (N ₂ SA) of 40 to 180 ^{m 2} /g and a DBP absorption of 80 cm ³ /100g or more per 100 parts by weight of straight asphalt, and that has an A value calculated by the following formula (1) in the range of 200 nm or less.
A=f・Dst・{[(0.86)/(φ・β) ^1/3 ]-1}…(1)
where f = exp(ΔD50/2Dst) ² ,
β=[1+0.0181(24M4DBP)]/1.59.
Here, Dst is the mode diameter (nm) of the Stokes equivalent diameter distribution of carbon black aggregates, ΔD50 is the half width (nm) of the Stokes equivalent diameter distribution, φ is the volume fraction, and 24M4DBP is the compressed DBP absorption amount (cm ³ /100 g).

[1] An asphalt modifier containing resin A and carbon black,
The carbon black content is 2.5% by mass or less,
An asphalt modifier in which the mass ratio of inorganic filler (excluding carbon black) to carbon black [inorganic filler/carbon black] is 1 or less.
[2] An asphalt composition containing asphalt and the asphalt modifier described in [1] above.
[3] A method for producing an asphalt composition, comprising the following steps 1 to 3 in this order:
Step 1: A step of mixing resin A and carbon black to obtain an asphalt modifier. Step 2: A step of mixing asphalt with the asphalt modifier obtained in Step 1. However, the asphalt modifier obtained in Step 1 contains 2.5% by mass or less of carbon black, and the mass ratio of inorganic filler (excluding carbon black) to carbon black [inorganic filler/carbon black] is 1 or less.

Detailed Description of the Invention

Asphalt pavement has a problem in that when exposed to sunlight for a long period of time, ultraviolet rays cause deterioration and cracks. This problem is particularly serious in areas with strong sunlight irradiation. When asphalt pavement deteriorates, repair becomes necessary. Pavement repair increases maintenance costs and has a significant impact on automobile traffic. Therefore, there is a demand for asphalt pavement that is less susceptible to deterioration by ultraviolet rays and has excellent weather resistance. However, the technology described in Patent Document 1 does not consider the weather resistance of the asphalt composition.
The present invention relates to an asphalt modifier that can realize an asphalt composition with excellent weather resistance, an asphalt composition using the asphalt modifier, and a method for producing the asphalt composition.

The inventors have discovered that the above problem can be solved by blending a specific amount of carbon black or less into an asphalt modifier containing Resin A and carbon black.

The present invention provides an asphalt modifier that can produce an asphalt composition with excellent weather resistance, an asphalt composition that uses the asphalt modifier, and a method for producing the asphalt composition.

[Asphalt modifier]
The asphalt modifier of the present invention contains resin A and carbon black, has a carbon black content of 2.5 mass% or less, and has a mass ratio of inorganic filler (excluding carbon black) to carbon black [inorganic filler/carbon black] of 1 or less. From the viewpoint of uniformly dispersing the carbon black in the asphalt and improving the weather resistance of the asphalt composition, the asphalt modifier of the present invention is preferably a melt-kneaded product.

The reason why the present invention has an effect is not clear, but is thought to be as follows.
Carbon black is resistant to ultraviolet light degradation, so its use in asphalt pavement can improve the weather resistance of roads. However, when carbon black is directly added to and mixed with asphalt or modified asphalt, the carbon black tends to aggregate in the asphalt, which means that a very large amount of carbon black must be added to improve weather resistance.
The asphalt modifier of the present invention contains resin A and carbon black, and the mass ratio of inorganic filler (excluding carbon black) to carbon black [inorganic filler/carbon black] is 1 or less. Therefore, even if the carbon black content is kept to 2.5 mass% or less, by mixing the asphalt modifier with asphalt, the carbon black can be uniformly dispersed in the asphalt. Therefore, it is believed that the weather resistance of asphalt compositions can be improved by using the asphalt modifier of the present invention.

The definitions of various terms used in this specification are shown below.
In the polyester resin, a "structural unit derived from an alcohol component" means a structure in which a hydrogen atom is removed from a hydroxy group of an alcohol component, and a "structural unit derived from a carboxylic acid component" means a structure in which a hydroxy group is removed from a carboxy group of a carboxylic acid component.
The term "carboxylic acid component" is a concept that includes not only the carboxylic acid itself, but also anhydrides that decompose during the reaction to produce an acid, and alkyl esters of carboxylic acids (for example, alkyl groups having 1 to 3 carbon atoms). When the carboxylic acid component is an alkyl ester of carboxylic acid, the number of carbon atoms in the alkyl group that is the alcohol residue of the ester is not included in the number of carbon atoms of the carboxylic acid.

<Resin A>
From the viewpoint of weather resistance, resin A is preferably a thermoplastic resin and preferably does not have a carbon-carbon double bond in its structure. The melting point or softening point of resin A is preferably 270°C or lower, more preferably 240°C or lower, and even more preferably 200°C or lower. The lower limit is, for example, 80°C or higher.
The melting point and softening point of Resin A can be adjusted by the raw material monomer composition, molecular weight, catalyst amount or reaction conditions, and can be determined by the method described in the Examples below.
Specific examples of resin A include polyester resin, ethylene-vinyl acetate copolymer resin, polyethylene resin, polypropylene resin, nylon resin, polystyrene resin, acrylonitrile-styrene copolymer resin (AS resin), polyvinyl chloride resin (PVC resin), polyvinyl alcohol resin (PVA resin), acrylonitrile-butadiene-styrene copolymer resin (ABS resin), and polyvinylidene chloride resin. Each resin can be used alone or in combination of two or more.
From the viewpoints of weather resistance, the aesthetic appearance of the asphalt pavement surface, and blackness, Resin A preferably contains one or more resins selected from polyester resin, ethylene-vinyl acetate copolymer resin, polyethylene resin, polypropylene resin, and nylon resin, more preferably contains one or more resins selected from polyester resin, ethylene-vinyl acetate copolymer resin, polyethylene resin, and polypropylene resin, and even more preferably contains polyester resin.

[Polyester resin]
The polyester resin is a polycondensation product of an alcohol component and a carboxylic acid component, and contains structural units derived from an alcohol component and structural units derived from a carboxylic acid component.
The polyester resin may be an amorphous polyester resin or a crystalline polyester resin, and is preferably an amorphous polyester resin.
The alcohol component, the carboxylic acid component, and the physical properties of the polyester resin will be described below.

(Alcohol content)
Examples of the alcohol component include chain aliphatic diols, alicyclic diols, aromatic diols, trihydric or higher polyhydric alcohols, etc. These alcohol components may be used alone or in combination of two or more.

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

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

Aromatic diols include, for example, bisphenol A (2,2-bis(4-hydroxyphenyl)propane) and alkylene oxide adducts of bisphenol A. Examples of alkylene oxide adducts of bisphenol A include the alkylene oxide adducts of bisphenol A represented by the following formula (I):

[In the formula, ^OR1 and ^R1O are alkylene oxides, ^R1 is an alkylene group having 2 or 3 carbon atoms, x and y are positive numbers indicating the average number of moles of alkylene oxide added, and the sum of x and y is preferably 1 or more, more preferably 1.5 or more, and is preferably 16 or less, more preferably 8 or less, and even more preferably 4 or less.]

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

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

The alcohol component may further contain a monohydric aliphatic alcohol in order to adjust the physical properties. Examples of monohydric aliphatic alcohols include lauryl alcohol, myristyl alcohol, palmityl alcohol, and stearyl alcohol. These monohydric aliphatic alcohols may be used alone or in combination of two or more.

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

The aliphatic dicarboxylic acid preferably has 4 or more carbon atoms in the main chain and 10 or less, more preferably 8 or less, and even more preferably 6 or less, such as fumaric acid, maleic acid, oxalic acid, malonic acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, succinic acid substituted with an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms, or anhydrides or alkyl esters thereof (e.g., alkyl groups having 1 to 3 carbon atoms). Examples of substituted succinic acids include dodecylsuccinic acid, dodecenylsuccinic acid, and octenylsuccinic acid.
Succinic acid substituted with an alkyl group having from 1 to 20 carbon atoms or an alkenyl group having from 2 to 20 carbon atoms, or an anhydride thereof, can be produced, for example, according to the description in JP-A-2008-145712. Commercially available products can also be used.

Aromatic dicarboxylic acids include, for example, phthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, or their anhydrides and alkyl esters (for example, alkyl groups having 1 to 3 carbon atoms). Of the above aromatic dicarboxylic acids, isophthalic acid and terephthalic acid are preferred, with terephthalic acid being more preferred, from the standpoints of suppressing aggregate scattering and weather resistance.

The trivalent or greater hexavalent polycarboxylic acid is preferably a trivalent carboxylic acid. Examples of trivalent or greater hexavalent polycarboxylic acids include trimellitic acid, 2,5,7-naphthalenetricarboxylic acid, pyromellitic acid, and anhydrides of these acids.

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

(Structural unit derived from polyethylene terephthalate)
The polyester resin preferably contains a polycondensate of an alcohol component, a carboxylic acid compound, and polyethylene terephthalate (PET). The polyethylene terephthalate may contain small amounts of components such as butanediol and isophthalic acid in addition to structural units derived from ethylene glycol and terephthalic acid. The polyethylene terephthalate is preferably recycled polyethylene terephthalate.
When the polyester resin contains structural units consisting of ethylene glycol and terephthalic acid derived from polyethylene terephthalate, the "structural units derived from alcohol components" include structural units derived from ethylene glycol derived from polyethylene terephthalate, and the "structural units derived from carboxylic acid components" include structural units derived from terephthalic acid derived from polyethylene terephthalate.

(Preferred embodiment of polyester resin)
In a preferred embodiment of the polyester resin, the content of structural units derived from aromatic diols in 100 mol% of structural units derived from alcohol components is preferably 10 mol% or more and 70 mol% or less, more preferably 20 mol% or more, even more preferably 30 mol% or more, and more preferably 60 mol% or less, even more preferably 50 mol% or less.
In a preferred embodiment of the polyester resin, the content of structural units derived from aliphatic diols in 100 mol% of structural units derived from alcohol components is preferably 30 mol% or more and 90 mol% or less, more preferably 40 mol% or more, even more preferably 50 mol% or more, and more preferably 80 mol% or less, even more preferably 70 mol% or less.
In a preferred embodiment of the polyester resin, the content of structural units derived from aromatic dicarboxylic acids in 100 mol% of structural units derived from carboxylic acid components is preferably 50 mol% or more and 98 mol% or less, more preferably 60 mol% or more, even more preferably 70 mol% or more, and more preferably 95 mol% or less, even more preferably 90 mol% or less.
In a preferred embodiment of the polyester resin, the content of structural units derived from aliphatic dicarboxylic acids in 100 mol% of structural units derived from carboxylic acid components is preferably 1 mol% or more and 20 mol% or less, more preferably 3 mol% or more, even more preferably 6 mol% or more, and more preferably 16 mol% or less, even more preferably 12 mol% or less.
In a preferred embodiment of the polyester resin, the content of the polycondensate of the alcohol component, the carboxylic acid component, and polyethylene terephthalate (PET) in the polyester resin is, from the viewpoint of weather resistance, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and still more preferably 95% by mass or more, and is 100% by mass or less.

(Physical properties of polyester resin)
From the viewpoint of weather resistance, the softening point of the polyester resin is preferably 80°C or higher and 140°C or lower, more preferably 85°C or higher, even more preferably 90°C or higher, and 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 weather resistance, the glass transition point of the polyester resin is preferably 30°C or higher and 95°C or lower, more preferably 40°C or higher, even more preferably 50°C or higher, and more preferably 85°C or lower, even more preferably 75°C or lower, and even more preferably 65°C or lower.
From the viewpoint of weather resistance, the acid value of the polyester resin is preferably 1 mgKOH/g or more and 30 mgKOH/g or less, more preferably 3 mgKOH/g or more, even more preferably 5 mgKOH/g or more, and more preferably 20 mgKOH/g or less, even more preferably 15 mgKOH/g or less.
From the viewpoint of weather resistance, the hydroxyl value of the polyester resin is preferably 1 mgKOH/g or more and 40 mgKOH/g or less, more preferably 10 mgKOH/g or more, even more preferably 20 mgKOH/g or more, and more preferably 35 mgKOH/g or less, even more preferably 30 mgKOH/g or less.

The softening point, glass transition point, acid value, and hydroxyl value of polyester resins can be measured by the methods described in the Examples. The softening point, glass transition point, acid value, and hydroxyl value can be adjusted by the raw material monomer composition, molecular weight, catalyst amount, or reaction conditions.

The polyester resin may be modified to the extent that its properties are not substantially impaired. Specific examples of modified polyester resins include polyester resins grafted or blocked with phenol, urethane, epoxy, etc., using methods described in JP-A Nos. 11-133668, 10-239903, and 8-20636. A preferred modified polyester resin is a urethane-modified polyester resin in which polyester resin is urethane-extended with a polyisocyanate compound.

(Method for producing polyester resin)
The polyester resin can be produced, for example, by polycondensing the alcohol component and the carboxylic acid component described above.
The temperature of the polycondensation reaction adjusts the reactivity and is preferably 160°C or higher, more preferably 190°C or higher, even more preferably 200°C or higher, and is preferably 260°C or lower, more preferably 250°C or lower, even more preferably 240°C or lower.

When the polyester resin contains structural units derived from ethylene glycol derived from polyethylene terephthalate and structural units derived from terephthalic acid derived from polyethylene terephthalate, the amount of polyethylene terephthalate present in the raw material is preferably 5% by mass or more and 65% by mass or less, more preferably 15% by mass or more, even more preferably 25% by mass or more, and more preferably 55% by mass or less, even more preferably 45% by mass or less, of 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, an ester exchange reaction occurs, and a polyester resin can be obtained in which structural units derived from polyethylene terephthalate are incorporated into structural units derived from the alcohol component and structural units derived from the carboxylic acid component.
Polyethylene terephthalate may be present from the start of the polycondensation reaction or may be added to the reaction system during the polycondensation reaction. The timing of adding polyethylene terephthalate is preferably when the reaction rate between the alcohol component and the carboxylic acid component is 10% or less, more preferably 5% or less. The reaction rate refers to the value of the amount of reaction water produced (mol) / the theoretical amount of water produced (mol) × 100.

In view of the reaction rate, an esterification catalyst can be used in the polycondensation reaction. Examples of the esterification catalyst include tin(II) compounds that do not have a Sn—C bond, such as tin(II) di(2-ethylhexanoate). From the viewpoint of the reaction rate, the amount of the esterification catalyst used is preferably 0.01 parts by mass or more and 2.0 parts by mass or less, more preferably 0.1 parts by mass or more, even more preferably 0.2 parts by mass or more, and more preferably 1.5 parts by mass or less, and even more preferably 1.0 part by mass or less, relative to 100 parts by mass of the raw material monomer.
In the polycondensation reaction, an esterification promoter can be used in addition to the esterification catalyst. Examples of the esterification promoter include pyrogallol compounds such as gallic acid. The amount of the esterification promoter used is preferably 0.001 to 0.20 parts by mass, more preferably 0.005 to 0.01 parts by mass, even more preferably 0.01 to 0.15 parts by mass, and even more preferably 0.10 to 0.10 parts by mass, per 100 parts by mass of the raw material monomer.

[Ethylene-vinyl acetate copolymer resin]
Ethylene-vinyl acetate copolymer resins are addition polymers of ethylene and vinyl acetate, and the polymerization form may be block or random. The content of vinyl acetate-derived structural units in the ethylene-vinyl acetate copolymer resin is preferably 10% by mass or more and 35% by mass or less, and from the viewpoint of dispersing carbon black in asphalt and improving weather resistance, it is more preferably 15% by mass or more, even more preferably 20% by mass or more, and more preferably 30% by mass or less.

[Polyethylene resin]
Specific examples of polyethylene resins include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), very-low-density polyethylene (ULDPE), and linear low-density polyethylene (LLDPE). From the viewpoint of weather resistance, medium-density polyethylene, low-density polyethylene, very-low-density polyethylene, and linear low-density polyethylene are preferred, and low-density polyethylene, very-low-density polyethylene, and linear low-density polyethylene are more preferred.

[Polypropylene resin]
The polypropylene resin may be a homopolymer of propylene or a copolymer of propylene and an α-olefin, but a homopolymer of propylene is preferred. The copolymer of propylene and an α-olefin may be polymerized in either a random or block form.
The number of carbon atoms in the α-olefin is preferably from 2 to 18. Specific examples of the α-olefin include ethylene, propylene, butene, pentene, hexene, heptene, octene, and nonene.
The content of propylene-derived structural units in the copolymer of propylene and an α-olefin is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, and is 99% by mass or less.

[Nylon resin]
Specific examples of nylon resins include polycapramide (nylon 6), poly-ω-aminoheptanoic acid (nylon 7), poly-ω-aminononanoic acid (nylon 9), polyundecaneamide (nylon 11), polylauryl lactam (nylon 12), polyethylenediamineadipamide (nylon 2,6), polytetramethyleneadipamide (nylon 4,6), polyhexamethyleneadipamide (nylon 6,6), polyhexamethylenesebacamide (nylon 6,10), polyhexamethylenedodecamide (nylon 6,12), polyoctamethyleneadipamide (nylon 8,6), polydecamethyleneadipamide (nylon 10,8), caprolactam/lauryl lactam copolymer (nylon 6/12), caprolactam/ω-amino Examples of the nylon copolymer include aliphatic nylons and copolymers thereof, such as nononanoic acid copolymer (nylon 6/9), caprolactam/hexamethylenediammonium adipate copolymer (nylon 6/6,6), lauryllactam/hexamethylenediammonium adipate copolymer (nylon 12/6,6), ethylenediamine adipamide/hexamethylenediammonium adipate copolymer (nylon 2,6/6,6), caprolactam/hexamethylenediammonium adipate/hexamethylenediammonium sebacate copolymer (nylon 6,6/6,10), and ethyleneammonium adipate/hexamethylenediammonium adipate/hexamethylenediammonium sebacate copolymer (nylon 6/6,6/6,10).

From the viewpoint of weather resistance, the total content of polyester resin, ethylene-vinyl acetate copolymer resin, polyethylene resin, polypropylene resin, and nylon resin in Resin A is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, and is 100% by mass or less.

(Content of resin A in asphalt modifier)
From the viewpoint of weather resistance, the content of resin A in the asphalt modifier is preferably 97.0 mass% or more, more preferably 97.5 mass% or more, even more preferably 98.0 mass% or more, still more preferably 98.5 mass% or more, of the total mass of the asphalt modifier. It is less than 100 mass%, preferably 99.99 mass% or less, more preferably 99.95 mass% or less, still more preferably 99.7 mass% or less.

<Carbon black>
Various grades of carbon black can be used. From the viewpoint of weather resistance, the grade of carbon black is preferably HAF, SAF, ISFA, EPC, FEF, GPF, HMF, or SRF, more preferably HAF, SAF, ISAF, or EPC, and even more preferably HAF.
From the viewpoint of weather resistance, the dibutyl phthalate (DBP) oil absorption of the carbon black is preferably 70 ml/100 g or more and 130 ml/100 g or less, more preferably 80 ml/100 g or more, even more preferably 90 ml/100 g or more, and more preferably 120 ml/100 g or less, even more preferably 110 ml/100 g or less.
The DBP oil absorption of carbon black is measured in accordance with "Determination of oil absorption" of ISO 4656 (JIS K 6217-4:2008).
From the viewpoint of weather resistance, the nitrogen adsorption specific surface area of carbon black is preferably 10 m ² /g or more, more preferably 30 m ² /g or more, even more preferably 50 m ² /g or more, and even more preferably 70 m ² /g or more, and preferably 200 m ² /g or less, more preferably 100 m ² /g or less, and even more preferably 85 m ² /g or less. From the same viewpoint, the nitrogen adsorption specific surface area of carbon black is preferably 10 m ² /g or more and 200 m ² /g or less, more preferably 30 m ² /g or more and 100 m ² /g or less, and even more preferably 50 m ² /g or more and 85 m ² /g or less.
The nitrogen adsorption specific surface area of carbon black is measured in accordance with JIS K 6217-2:2001.
The carbon black may be used alone or in combination of two or more.

(Carbon black content in asphalt modifier)
From the viewpoint of weather resistance, the carbon black content in the asphalt modifier is 2.5 mass% or less of the total mass of the asphalt modifier. From the viewpoint of weather resistance, the content is preferably 0.01 mass% or more and 2.0 mass% or less, more preferably 1.5 mass% or less, more preferably 0.05 mass% or more, even more preferably 0.3 mass% or more, and even more preferably 0.7 mass% or more.

In order to improve the dispersibility of carbon black and enhance weather resistance, the asphalt modifier preferably has a blackness of 7 or more and 40 or less, more preferably 30 or less, even more preferably 20 or less, and even more preferably 15 or less. Blackness can be measured by the method described in the examples.

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

<Inorganic filler>
In the present invention, the inorganic filler means an inorganic filler other than carbon black that is commonly used in asphalt modifiers, and specific examples include silica and diatomaceous earth.

(Content of inorganic filler in asphalt modifier)
In the asphalt modifier, the content of inorganic filler per 100 parts by mass of resin A is preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, even more preferably 0.1 parts by mass or less, and may even be 0 parts by mass, from the viewpoint of the durability of the asphalt pavement.

In the asphalt modifier, the mass ratio of inorganic filler to carbon black [inorganic filler/carbon black] is 1 or less, preferably 0.5 or less, more preferably 0.1 or less, and may be 0, from the viewpoint of the durability of the asphalt pavement.

[Method for producing asphalt modifier]
The asphalt modifier can be obtained, for example, by heating resin A, carbon black, and, if necessary, an inorganic filler to melt resin A, and kneading the mixture in a commonly used mixer until the carbon black and inorganic filler are uniformly dispersed in resin A.
Commonly used mixers include a homomixer, a dissolver, a paddle mixer, a ribbon mixer, a screw mixer, a planetary mixer, a vacuum countercurrent mixer, a roll mill, and a twin-screw extruder.

[Asphalt composition]
The asphalt composition of the present invention contains asphalt and the resin A and carbon black that constitute the asphalt modifier.

<Asphalt>
The asphalt composition of the present invention contains asphalt.
As the asphalt, various types of asphalt can be used, including, for example, straight asphalt, which is petroleum asphalt for paving, and modified asphalt.
Straight asphalt is the residual bitumen material obtained by subjecting crude oil to atmospheric distillation or vacuum distillation.
Modified asphalts include blown asphalt, polymer-modified asphalt modified with polymeric materials such as thermoplastic elastomers and thermoplastic resins (hereinafter also referred to as "polymer-modified asphalt"). Blown asphalt refers to asphalt obtained by heating a mixture of straight asphalt and heavy oil and then blowing air into it to oxidize it.
The asphalt is preferably selected from straight asphalt and polymer-modified asphalt, with polymer-modified asphalt being more preferred from the viewpoint of durability of the asphalt pavement, and straight asphalt being more preferred from the viewpoint of versatility.

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

Among these, from the viewpoint of durability of asphalt pavement, the thermoplastic elastomer is preferably at least one selected from SB, SBS, SBR, SI, SIS, SIR, and ethylene/acrylic acid ester copolymer, more preferably at least one selected from SB, SBS, SBR, SI, SIS, and SIR, and even more preferably at least one selected from SBR and SBS.
From the viewpoint of the durability of the asphalt pavement, the content of thermoplastic elastomer in the polymer modified asphalt is preferably 0.1% by mass or more and 30% by mass or less, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and more preferably 15% by mass or less, even more preferably 7% by mass or less.

From the viewpoint of the durability of asphalt pavement, the asphaltene content in asphalt is preferably 13 mass% or more and 35 mass% or less, more preferably 15 mass% or more, even more preferably 17 mass% or more, and more preferably 27 mass% or less, even more preferably 24 mass% or less.
The content of asphaltene in asphalt is a value measured in accordance with Japan Petroleum Institute standard JPI-5S-22-83 "Composition analysis method of asphaltene by column chromatography."

The total content of straight asphalt and polymer-modified asphalt in the asphalt composition is preferably 60% by mass or more and less than 100% by mass, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and more preferably 99.5% by mass or less. From the perspective of demonstrating asphalt performance, the total content is preferably above the lower limit, and from the perspective of storage stability, it is preferably below the upper limit.

(Resin A and carbon black content, etc.)
From the viewpoint of durability and storage stability of the asphalt pavement, the total content of resin A and carbon black in the asphalt composition is preferably 0.5 parts by mass or more and 15 parts by mass or less, more preferably 0.8 parts by mass or more, and more preferably 12 parts by mass or less, even more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less, per 100 parts by mass of asphalt.

The carbon black content in Resin A and carbon black is 2.5% by mass or less. From the standpoint of weather resistance, this content is preferably 0.01% by mass or more and 2.0% by mass or less, more preferably 1.5% by mass or less, and more preferably 0.05% by mass or more.

In the asphalt composition, the content of inorganic filler per 100 parts by mass of resin A is preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, even more preferably 0.1 parts by mass or less, and may even be 0 parts by mass, from the perspective of the durability of the asphalt pavement.

The mass ratio of inorganic filler (excluding carbon black) to carbon black in the asphalt composition [inorganic filler/carbon black] is 1 or less, preferably 0.5 or less, more preferably 0.1 or less, even more preferably 0.01 or less, and may even be 0, from the viewpoint of durability and storage stability of the asphalt pavement.
As mentioned above, specific examples of inorganic fillers include silica and diatomaceous earth.

<Dispersant>
The asphalt composition may further include a dispersant.
Examples of dispersants include polymer dispersants such as polyamidoamines and their salts, polycarboxylic acids and their salts, high molecular weight unsaturated acid esters, modified polyurethanes, modified polyesters, modified poly(meth)acrylates, (meth)acrylic copolymers, and naphthalenesulfonic acid-formalin condensates. In the present invention, the term "polymer dispersant" refers to a dispersant having a weight-average molecular weight of 1,000 or more.
However, from the viewpoint of storage stability, the content of the dispersant is preferably less than 1 part by mass, more preferably less than 0.5 parts by mass, and even more preferably substantially no dispersant is contained, relative to 100 parts by mass of Resin A.

<Other ingredients>
The asphalt composition may further include an organic acid.
The organic acid may be acetic acid, citric acid, malic acid, fumaric acid, maleic acid, or an organic acid anhydride.
However, from the viewpoint of storage stability, the content of the organic acid is preferably less than 1 part by mass, more preferably less than 0.5 parts by mass, and even more preferably substantially no organic acid is contained, relative to 100 parts by mass of Resin A.
Furthermore, in the asphalt composition, the mass ratio of organic acid to carbon black [organic acid/carbon black] is 1 or less, preferably 0.5 or less, more preferably 0.1 or less, even more preferably 0.01 or less, and may even be 0, from the viewpoint of durability and storage stability of the asphalt pavement.

From the viewpoint of weather resistance, it is preferable that the carbonyl index (C _A ) of the asphalt composition of the present invention after 48 hours of irradiation with 300 to 400 nm ultraviolet light at 150 W/ ^m2 and the carbonyl index (C _B ) before ultraviolet light irradiation satisfy the following formula (1):
C _A /C _B <2 (1)
The carbonyl index is the ratio of the absorbance at 1700 cm ⁻¹ to the absorbance at 1600 cm ⁻¹ of the asphalt composition (absorbance at 1700 cm ⁻¹ /absorbance at 1600 cm ⁻¹ ), as measured by Fourier transform infrared spectroscopy (FT-IR).
The lower limit of the formula (1) is, for example, 1.0 from the viewpoint of manufacturing.

[Method for producing asphalt composition]
The method for producing an asphalt composition of the present invention comprises the following steps 1 and 2 in this order.
Step 1: Mixing resin A and carbon black to obtain an asphalt modifier. Step 2: Mixing asphalt with the asphalt modifier obtained in Step 1. However, the carbon black content in the asphalt modifier obtained in Step 1 is 2.5 mass% or less, and the mass ratio of inorganic filler (excluding carbon black) to carbon black [inorganic filler/carbon black] is 1 or less from the viewpoint of durability and storage stability of asphalt pavement.

Step 1 is the same as in the above-mentioned [Method for producing asphalt modifier].
In step 2, the asphalt is heated and melted, the asphalt modifier is added, and the mixture is stirred and mixed in a commonly used mixer until the resin A and carbon black that constitute the asphalt modifier are uniformly dispersed in the asphalt, thereby obtaining an asphalt composition.
Commonly used mixers include a homomixer, a dissolver, a paddle mixer, a ribbon mixer, a screw mixer, a planetary mixer, a vacuum countercurrent mixer, a roll mill, and a twin-screw extruder.

The mixing temperature of the asphalt and the asphalt modifier is preferably 140°C or higher and 230°C or lower, more preferably 150°C or higher, even more preferably 160°C or higher, and more preferably 210°C or lower, even more preferably 200°C or lower, from the viewpoint of uniformly dispersing the resin A and carbon black that constitute the asphalt modifier in the asphalt.
Furthermore, from the viewpoint of uniformly dispersing the polyester in the asphalt, the mixing time of the asphalt and the asphalt modifier is preferably 5 minutes or more and 5 hours or less, more preferably 10 minutes or more, even more preferably 20 minutes or more, and more preferably 3 hours or less, even more preferably 1 hour or less.
The asphalt composition of the present invention is a binder composition, and can be used for paving after, for example, adding aggregate to the asphalt composition to form an asphalt mixture. In other words, the asphalt composition of the present invention is suitable for paving, and particularly suitable for road paving.

[Asphalt mixture]
An asphalt mixture, which is a suitable example of the use of the asphalt composition, will now be described.
The asphalt mixture contains aggregate and the above-described asphalt composition. That is, the asphalt mixture contains at least aggregate, asphalt, resin A, and carbon black.

<Aggregate>
The aggregate can be selected from crushed stone, boulders, gravel, sand, recycled aggregate, ceramics, etc. In addition, the aggregate can be either coarse aggregate with a particle size of 2.36 mm or more or fine aggregate with a particle size of less than 2.36 mm, with a combination of coarse aggregate and fine aggregate being preferred.
From the viewpoint of the durability of the asphalt pavement, the aggregate content in the asphalt mixture is preferably 85% by mass or more and 98% by mass or less, more preferably 90% by mass or more, more preferably 92% by mass or more, and more preferably 97% by mass or less, and even more preferably 96% by mass or less.

<Additives>
In addition to the aggregate, asphalt, resin A, and carbon black described above, various additives conventionally used in asphalt mixtures, such as film-forming agents, thickening stabilizers, and emulsifiers, may also be added to the asphalt mixture as necessary.
The total content of these additives in the asphalt mixture is preferably 50% by mass or less, more preferably 25% by mass or less, and even more preferably 5% by mass or less.

[Method for producing asphalt mixture]
There are no particular limitations on the method for producing the asphalt mixture, and any method may be used. Generally, the method can be carried out in accordance with the method for producing an asphalt mixture containing aggregate and asphalt. Specifically, the asphalt composition described above can be added to heated aggregate and mixed.

The temperature of the heated aggregate is preferably 130°C or higher and 230°C or lower, more preferably 150°C or higher, even more preferably 170°C or higher, more preferably 210°C or lower, and even more preferably 200°C or lower. From the perspective of the durability of the asphalt pavement, the temperature of the heated aggregate is preferably above the lower limit stated above, and from the perspective of preventing thermal degradation of the asphalt, it is preferably below the upper limit stated above.

The mixing temperature of the aggregate and asphalt composition is preferably 130° C. or higher and 230° C. or lower, more preferably 150° C. or higher, even more preferably 170° C. or higher, more preferably 210° C. or lower, and even more preferably 200° C. or lower. From the viewpoint of the durability of the asphalt pavement, the mixing temperature of the aggregate and asphalt composition is preferably equal to or higher than the lower limit mentioned above, and from the viewpoint of preventing thermal degradation of the asphalt, it is preferably equal to or lower than the upper limit mentioned above.
The mixing time for the aggregate and the asphalt composition is not particularly limited, but is preferably 30 seconds or more and 2 hours or less, more preferably 1 minute or more, even more preferably 2 minutes or more, and more preferably 1 hour or less, even more preferably 30 minutes or less.

From the viewpoint of the durability of the asphalt pavement, the method for producing an asphalt mixture preferably includes a step of mixing aggregate and an asphalt composition and then holding the resulting asphalt mixture at the above-mentioned mixing temperature or at a temperature equal to or higher than the mixing temperature.
In the step of holding the asphalt mixture, the mixture may be further mixed.
The retention time is preferably 0.5 hours or more, more preferably 1 hour or more, and even more preferably 1.5 hours or more. The upper limit of the time is not particularly limited, but is, for example, about 48 hours.

[Road paving method]
The asphalt mixture is suitable for road paving, and as described above, an asphalt mixture obtained by adding aggregate to an asphalt composition is used for road paving.
The road paving method includes a step of applying the above-mentioned asphalt mixture to a road to form an asphalt pavement layer. Specifically, the road paving method includes a step of mixing the above-mentioned asphalt composition with heated aggregate to obtain an asphalt mixture (Step I), and a step of applying the asphalt mixture obtained in Step I to a road to form an asphalt pavement layer (Step II). The asphalt pavement layer is preferably a base layer or a surface layer.

The asphalt mixture can be compacted and applied using a similar method using known construction machinery. When used as a heated asphalt mixture, the compaction temperature is preferably 100°C or higher and 200°C or lower, more preferably 120°C or higher, even more preferably 130°C or higher, and more preferably 180°C or lower, from the perspective of the durability of the asphalt pavement.

The present invention includes the following aspects.
<1>
An asphalt modifier containing resin A and carbon black,
The carbon black content is 2.5% by mass or less,
An asphalt modifier having a mass ratio of inorganic filler (excluding carbon black) to carbon black [inorganic filler/carbon black] of 1 or less.
<2>
The asphalt modifier according to <1>, comprising a melt-kneaded mixture of resin A and carbon black.
<3>
The asphalt modifier according to <1> or <2>, wherein the blackness is 7 or more and 40 or less, preferably 7 or more and 30 or less, more preferably 7 or more and 20 or less, and even more preferably 7 or more and 15 or less.
＜4＞
<1> to <3>, wherein the resin A comprises one or more selected from polyester resin, ethylene-vinyl acetate copolymer resin, polyethylene resin, polypropylene resin, and nylon resin. The asphalt modifier according to any one of <1> to <3>.
<5>
The asphalt modifier according to <4>, wherein the polyester resin contains a polycondensate of an alcohol component, a carboxylic acid compound, and polyethylene terephthalate.
<6>
<1> to <5>, wherein the content of resin A is 97.0% by mass or more, preferably 97.5% by mass or more, more preferably 98.0% by mass or more, and even more preferably 98.5% by mass or more. Asphalt modifier according to any one of <1> to <5>.
＜７＞
<1> to <6>, wherein the content of resin A is less than 100% by mass, preferably 99.99% by mass or less, more preferably 99.95% by mass or less, and even more preferably 99.7% by mass or less. Asphalt modifier according to any one of <1> to <6>.
＜8＞
The content of resin A is 97.0% by mass or more and less than 100% by mass, preferably 97.5% by mass or more and 99.99% by mass or less, more preferably 98.0% by mass or more and 99.95% by mass or less. The asphalt modifier according to any one of <1> to <7>.
＜９＞
<1> to <8>, wherein the carbon black content is 2.0% by mass or less, preferably 1.5% by mass or less. The asphalt modifier according to any one of <1> to <8>.
<10>
<1> to <9>, wherein the carbon black content is 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.7% by mass or more. Asphalt modifier according to any one of <1> to <9>.
<11>
The carbon black content is 0.01% by mass or more and 2.5% by mass or less, preferably 0.05% by mass or more and 2.0% by mass or less, more preferably 0.3% by mass or more and 1.5% by mass or less. The asphalt modifier according to any one of <1> to <10>.
<12>
<1> to <11>, wherein the mass ratio of the inorganic filler to the carbon black [inorganic filler / carbon black] is 0.5 or less, preferably 0.1 or less, more preferably 0. Asphalt modifier according to <1> to <11>.
<13>
An asphalt modifier containing resin A and carbon black,
The carbon black content is 0.01% by mass or more and 2.5% by mass or less,
The content of resin A is 97.5% by mass or more and 99.9% by mass or less,
An asphalt modifier having a mass ratio of inorganic filler (excluding carbon black) to carbon black [inorganic filler/carbon black] of 1 or less.
<14>
An asphalt modifier containing resin A and carbon black,
The carbon black content is 0.01% by mass or more and 2.5% by mass or less,
The content of resin A is 97.5% by mass or more and 99.9% by mass or less,
Resin A is polyester,
An asphalt modifier having a mass ratio of inorganic filler (excluding carbon black) to carbon black [inorganic filler/carbon black] of 1 or less.
＜15＞
An asphalt composition containing asphalt and the asphalt modifier according to any one of <1> to <14>.
<16>
<15> The asphalt composition according to
An asphalt composition in which the carbonyl index (C _A ) after 48 hours of irradiation with 300 to 400 nm ultraviolet light at 150 W/m ² and the carbonyl index (C _B ) before ultraviolet light irradiation satisfy the following formula (1):
C _A /C _B <2 (1)
The carbonyl index is the ratio of the absorbance at 1700 cm ⁻¹ to the absorbance at 1600 cm ⁻¹ of the asphalt composition (absorbance at 1700 cm ⁻¹ /absorbance at 1600 cm ⁻¹ ), as measured by Fourier transform infrared spectroscopy.
＜17＞
A method for producing an asphalt composition, comprising the following steps 1 and 2 in this order:
Step 1: A step of mixing resin A and carbon black to obtain an asphalt modifier. Step 2: A step of mixing asphalt with the asphalt modifier obtained in Step 1. However, the asphalt modifier obtained in Step 1 contains 2.5% by mass or less of carbon black, and the mass ratio of inorganic filler (excluding carbon black) to carbon black [inorganic filler/carbon black] is 1 or less.

The present invention will be explained in detail below using examples, but the present invention is not limited to these examples in any way.

The physical properties of Resin A and the like were measured and evaluated by the following methods.
[Measurement method]
[Softening point, melting point and glass transition point]
(1) Softening Point Using a flow tester "CFT-500D" (Shimadzu Corporation), 1 g of a sample was extruded from a nozzle with a diameter of 1 mm and a length of 1 mm while applying a load of 1.96 MPa with a plunger while heating at a temperature increase rate of 6°C/min. The plunger depression amount of the flow tester was plotted against the temperature, and the temperature at which half of the sample flowed out was taken as the softening point.
(2) Melting Point and Glass Transition Point Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan Co., Ltd.), 0.01 to 0.02 g of a sample was weighed into an aluminum pan, heated to 200°C, and cooled from that temperature to 0°C at a rate of 10°C/min. Next, measurements were taken while heating to 150°C at a rate of 10°C/min. The melting point was determined when the temperature of the peak with the largest peak area was within 20°C of the softening point.
The glass transition temperature was determined as the temperature at the intersection of an extension of the baseline below the maximum endothermic peak temperature and a tangent line showing the maximum slope from the rising part of the peak to the peak apex.

[Acid value and hydroxyl value of polyester resin]
The acid value and hydroxyl value of the polyester resin 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)).

Manufacturing example (polyester resin)
The BPA-PO shown in Table 1 was placed in a 5-liter four-neck flask equipped with a thermometer, a stainless steel stirring rod, a downflow condenser, and a nitrogen inlet tube and heated to 100°C. After adding terephthalic acid at 100°C, the temperature was increased to 180°C at 0.5°C/min. After adding PET at 180°C, the temperature was increased to 235°C at 0.5°C/min. Under a nitrogen atmosphere, 20 g of tin(II) di(2-ethylhexanoate) and 2 g of gallic acid were added at 235°C, and a condensation polymerization reaction was carried out at 235°C for 6 hours. After cooling to 180°C, branched alkenyl succinic anhydride (alkenyl group carbon number: 12, dodecenyl) was added. The temperature was increased from 180°C to 220°C at 0.3°C/min, and the reaction was continued at 220°C and 20 kPa until the softening point shown in Table 1 was reached, yielding a polyester resin.

Example a1 (Production of asphalt modifier a1)
While rotating a baby roll heated to 180 ° C, 99.9 g of the polyester resin synthesized in the above Production Example and 0.1 g of carbon black (HAF) were placed on it to dissolve the polyester resin. The rotation speed was changed to 15 rpm, and the mixture was kneaded for 20 minutes. After kneading was completed, the kneaded product was removed from the kneader, and the kneaded product adhering to the baby roll was scraped off and kneaded into the kneaded product removed from the kneader to obtain asphalt modifier a1.

Examples a2 to a6 and Comparative Examples b1 to b4 (Production of Asphalt Modifiers a2 to a6 and b1 to b4)
Asphalt modifiers a2 to a6 were produced in the same manner as in Example a1, except that the type of resin and the blending amounts of resin and carbon black were as shown in Table 2.
The polyester resin obtained in the production example was designated as asphalt modifier b1.
The carbon black was designated as asphalt modifier b2.
Asphalt modifiers b3 and b4 were produced in the same manner as in Example a1, except that the type of resin and the blending amounts of resin and carbon black were as shown in Table 2.

[evaluation]
The blackness of the asphalt modifier was measured as follows, and the results are shown in Table 2.

[Blackness]
The asphalt modifier was placed in an aluminum container (manufactured by Trusco Nakayama Corporation, product number RC092282 220CC) and dissolved in a dryer at 180 ° C. The container was removed, allowed to stand until it reached room temperature, and then the asphalt modifier was removed from the container. Next, a color difference meter (TES-135A, manufactured by TES ELECTRICAL ELECTRONIC CORP.) was placed on the bottom of the removed asphalt modifier (the surface that was in contact with the bottom of the container) and measured, and the Lab value was taken as the blackness.
Note that the blackness of asphalt modifier b2 was not measured.

Example 1 (Production of Asphalt Composition 1)
50 g of modified asphalt (Resifix, manufactured by Showa Rekisei Kogyo Co., Ltd.) was weighed into a 300 ml stainless steel container and stirred at 300 rpm with a propeller while heating to 180° C. After stirring for 10 minutes, 2.5 g of asphalt modifier a1 was added, and the mixture was stirred for 30 minutes to obtain asphalt composition 1.
One to two drops of the above-mentioned asphalt composition 1 were placed on a glass slide, which was then covered with a cover glass and allowed to stand for 3 minutes in a dryer at 180° C. Asphalt composition 1 sandwiched between the glass slide and the cover glass spread, and it was confirmed that an asphalt coating had been formed on the glass slide, and the cover glass was immediately removed.

Examples 2 to 6 and Comparative Examples 1 to 5 (Production of Asphalt Compositions 2 to 6 and c1 to c5)
Asphalt compositions 2 to 5 and c1 to c5 were produced in the same manner as in Example 1, except that the types and amounts of asphalt modifiers were as shown in Table 3. An asphalt coating was formed on a glass slide using each asphalt composition.

[evaluation]
The asphalt coatings obtained from the asphalt compositions were evaluated as follows, and the results are shown in Table 3.

[Evaluation of CB dispersibility]
The morphology of the asphalt coating on the slide glass was confirmed by bright-field observation using a microscope (DSX1000, manufactured by Olympus Corporation). If no carbon black (CB) aggregates of 500 μm or more were observed, the dispersibility of the CB was rated as "good," and if they were observed, the dispersibility of the CB was rated as "poor."

[Weather resistance test]
The asphalt coatings on the glass slides obtained in each of the Examples and Comparative Examples were irradiated with ultraviolet light using a Super Xenon Weather Meter SX75 (Suga Test Instruments Co., Ltd.) under conditions of a UV intensity of 150 W/m ² , an irradiation wavelength of 300 to 400 nm, a tank temperature of 40°C, and a relative humidity of 75%. The glass slides were attached around a lamp to ensure uniform irradiation of the ultraviolet light, and were rotated while being irradiated with ultraviolet light for 48 hours, and these were used as samples after ultraviolet irradiation.
For the measurements (1) and (2) below, samples before and after ultraviolet irradiation were used.

(1) Pencil Hardness Measurement Pencil hardness was measured using a pencil scratch tester (manufactured by TP Giken Co., Ltd.) according to JIS K5600-5-4:1990. The asphalt coating formed on a glass slide was scratched with a tester, starting with a high-hardness 9H pencil (uni-pencil for pencil scratch value test) and gradually decreasing the hardness. The scratches were observed using a microscope (DSX1000 manufactured by Olympus Corporation), and the pencil hardness at which the coating was scraped and the glass was exposed was determined. The highest pencil hardness at which the coating was scraped and the glass was not exposed was taken as the pencil hardness of the asphalt coating. For example, if the glass was exposed by scraping with 4H and not exposed by 3H, the pencil hardness of the asphalt coating was taken as 3H.
(2) FT-IR measurement (calculation of carbonyl index increment)
FT-IR measurements were performed using an apparatus manufactured by Thermo Fisher Scientific Inc. Measurements were performed using samples before and after UV irradiation, and the carbonyl indices (I) and (II) below were calculated from the obtained absorption peak curves, and the carbonyl index increment was calculated using the following formula. A larger carbonyl index increment indicates more deterioration of the asphalt coating, and a smaller carbonyl index increment indicates better weather resistance.

Carbonyl Index Increment = Carbonyl Index (II) / Carbonyl Index (I)

Carbonyl index (II): absorbance at 1700 cm ⁻¹ / absorbance at 1600 cm ⁻¹ of the sample after UV irradiation Carbonyl index (I): absorbance at 1700 cm ⁻¹ / absorbance at 1600 cm ⁻¹ of the sample before UV irradiation

Table 3 shows that asphalt compositions obtained using asphalt modifiers containing resin A and carbon black, in which the carbon black content is 2.5% by mass or less and the mass ratio of inorganic filler (excluding carbon black) to carbon black [inorganic filler/carbon black] is 1 or less, have excellent weather resistance (Examples 1 to 6). Furthermore, in Examples 2 and 3, in which polyester resin was used as resin A, the pencil hardness was higher after UV irradiation than before UV irradiation, indicating better weather resistance. This is presumably due in part to the fact that the asphalt coating formed using an asphalt modifier containing a specific amount of polyester resin exhibited stronger interactions between the carbon black and asphalt components upon UV irradiation.
In contrast, when only polyester resin was used as the asphalt modifier (Comparative Example 1), when the carbon black content in the asphalt modifier exceeded 2.5% by mass (Comparative Examples 3 and 4), and when no asphalt modifier was used (Comparative Example 5), the pencil hardness decreased after UV irradiation compared to before UV irradiation, indicating that the weather resistance of the asphalt composition was poor. In Comparative Example 2, only carbon black was used as the asphalt modifier, but the carbon black was sometimes not sufficiently dispersed in the asphalt, making it impossible to produce a uniform asphalt coating, and the rating was therefore "-".

Claims (9)

An asphalt modifier containing resin A and carbon black,
The carbon black content is 2.5% by mass or less,
An asphalt modifier having a mass ratio of inorganic filler (excluding carbon black) to carbon black [inorganic filler/carbon black] of 1 or less. The asphalt modifier according to claim 1, comprising a melt-kneaded mixture of resin A and carbon black. The asphalt modifier according to claim 1 or 2, having a blackness of 7 or more and 40 or less. The asphalt modifier according to any one of claims 1 to 3, wherein resin A comprises one or more resins selected from polyester resin, ethylene-vinyl acetate copolymer resin, polyethylene resin, polypropylene resin, and nylon resin. The asphalt modifier according to claim 4, wherein the polyester resin contains a polycondensate of an alcohol component, a carboxylic acid compound, and polyethylene terephthalate. The asphalt modifier according to any one of claims 1 to 5, wherein the content of resin A is 97.0% by mass or more. An asphalt composition containing asphalt and the asphalt modifier described in any one of claims 1 to 6. The asphalt composition of claim 7,
An asphalt composition in which the carbonyl index (C _A ) after 48 hours of irradiation with 300 to 400 nm ultraviolet light at 150 W/m ² and the carbonyl index (C _B ) before ultraviolet light irradiation satisfy the following formula (1):
C _A /C _B <2 (1)
The carbonyl index is the ratio of the absorbance at 1700 cm ⁻¹ to the absorbance at 1600 cm ⁻¹ of the asphalt composition (absorbance at 1700 cm ⁻¹ /absorbance at 1600 cm ⁻¹ ), as measured by Fourier transform infrared spectroscopy. A method for producing an asphalt composition, comprising the following steps 1 and 2 in this order:
Step 1: A step of mixing resin A and carbon black to obtain an asphalt modifier. Step 2: A step of mixing asphalt with the asphalt modifier obtained in Step 1. However, the asphalt modifier obtained in Step 1 contains 2.5% by mass or less of carbon black, and the mass ratio of inorganic filler (excluding carbon black) to carbon black [inorganic filler/carbon black] is 1 or less.