Asphalt composition

Abstract

To provide an asphalt composition that can reduce the amount of generation of micro plastic, without impairing the durability of asphalt pavement.SOLUTION: The present invention provides an asphalt composition obtained by blending asphalt and an addition polymerization polymer, wherein the addition polymerization polymer has a hydroxyl value of 10-60 mgKOH / g, and a weight average molecular weight (Mw) of 2,500-70,000.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Asphalt paving is used for roads, parking lots, freight yards, and sidewalks because it is relatively easy to lay and the time from the start of paving work to the start of traffic is short. Asphalt paving is formed by an asphalt mixture in which aggregates are bound together with asphalt, so the paved road has good hardness and durability.

[0003] Patent Document 1 discloses an asphalt composition containing asphalt, an asphalt modifier made of copolymer, petroleum resin, and polyolefin resin in predetermined proportions, for the purpose of strengthening the adhesion between a floor slab and a waterproof sheet or between a coating-type waterproof layer and an asphalt paving material. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2004-346119 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] If asphalt pavement is not durable enough, it will deteriorate with long-term use, causing rutting. Furthermore, the road surface will wear away, generating asphalt dust and microplastics. The present invention relates to an asphalt composition that can reduce the amount of microplastics generated without impairing the durability of asphalt pavement. [Means for solving the problem]

[0006] The present invention relates to the following [1] to [6]. [1] An asphalt composition comprising asphalt and an addition polymerization polymer, The hydroxyl value of the addition polymerization polymer is 10 mg KOH / g or more and 60 mg KOH / g or less, and the weight-average molecular weight (M w An asphalt composition in which the ratio is between 2,500 and 70,000. [2] An asphalt mixture comprising the asphalt composition described in [1] above and aggregate. [3] The hydroxyl value is 10 mg KOH / g or more and 60 mg KOH / g or less, and the weight-average molecular weight (M w An asphalt modifier comprising an addition polymerization polymer having a ratio of 2,500 to 70,000. [4] A road paving method comprising the step of applying the asphalt mixture described in [2] to a road to form an asphalt coating layer. [5] A method for producing an asphalt composition comprising the step of mixing asphalt and an addition polymerization polymer, wherein the hydroxyl value of the addition polymerization polymer is 10 mg KOH / g or more and 60 mg KOH / g or less, and the weight-average molecular weight (M w A method for producing an asphalt composition, wherein the ratio is between 2,500 and 70,000. [6] A method for producing an asphalt composition comprising the following steps 1 and 2. Step 1: A process for producing an addition polymerization polymer having a hydroxyl value of 10 mg KOH / g or more and 60 mg KOH / g or less, and a weight-average molecular weight (Mw) of 2,500 or more and 70,000 or less. Step 2: Mixing asphalt with addition polymerization polymer. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an asphalt composition that can reduce the amount of microplastics generated without impairing the durability of asphalt pavement. [Modes for carrying out the invention]

[0008] [Asphalt Composition] The asphalt composition of the present invention is an asphalt composition prepared by blending asphalt and an addition polymerization polymer, wherein the hydroxyl value of the addition polymerization polymer is 10 mgKOH / g or more and 60 mgKOH / g or less, and the weight average molecular weight (M w ) is 2,500 or more and 70,000 or less.

[0009] The inventors of the present invention have found that by blending a specific amount of a specific addition polymerization polymer into an asphalt composition, the amount of microplastics generated can be reduced without impairing the durability of the asphalt pavement obtained by using the asphalt composition. Although the detailed mechanism by which the effects of the present invention are obtained is unknown, it is thought in part as follows. The aggregate constituting the asphalt pavement is hydrophilic. On the other hand, asphalt contains an asphaltene component that is hydrophilic and has aggregate adsorptivity, and a maltene component that is hydrophobic and has low aggregate adsorptivity. Since the interaction between the aggregate and the maltene component is low, the adhesiveness between the aggregate and the asphalt as a whole becomes insufficient, the road surface is scraped and worn asphalt powder is generated, which causes the generation of microplastics. Conventionally, an additive that enhances adhesiveness by interposing a compound having affinity for both the aggregate and the asphalt (especially the maltene component) has been used. However, such a compound also has the effect of softening the asphalt, resulting in insufficient durability of the asphalt pavement and causing rutting and cracking due to deterioration during long-term use. The addition polymerization polymer used in the present invention can impart adhesiveness between the asphalt and the aggregate while also expecting sufficient durability. As this mechanism of action, it is presumed that the specific addition polymerization polymer of the present invention preferentially interacts with the maltene component and imparts polarity, so that the adhesiveness between the aggregate and the asphalt can be improved without reducing the durability. Due to such an effect, it is considered that the amount of microplastics generated can be reduced without impairing the durability of the asphalt pavement.

[0010] [Asphalt] The asphalt composition of the present invention is formulated with asphalt. As the asphalt, various asphalts can be used. For example, in addition to straight asphalt which is petroleum asphalt for paving, modified asphalt can be mentioned. Examples of the modified asphalt include blown asphalt; asphalt modified with polymer materials such as thermoplastic elastomers and thermoplastic resins. Straight asphalt means a residual bituminous substance obtained by treating crude oil with an atmospheric distillation unit, a vacuum distillation unit, etc. Also, blown asphalt means asphalt obtained by heating a mixture of straight asphalt and heavy oil and then blowing air into it for oxidation. As the asphalt, from the viewpoints of the durability of asphalt paving and the ease of availability, straight asphalt or modified asphalt is preferably used. In this specification, "asphalt" includes bitumen defined in German Industrial Standard DIN EN 12597. "Asphalt" and "bitumen" shall be used interchangeably.

[0011] The blending amount of asphalt in the asphalt composition is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 75% by mass or more, even more preferably 80% by mass or more, from the viewpoints of reducing the generation amount of microplastics and exhibiting asphalt performance, and preferably 99.5% by mass or less, more preferably 99% by mass or less, still more preferably 98% by mass or less, from the viewpoint of reducing the generation amount of microplastics.

[0012] 〔Asphalt Modified with Thermoplastic Elastomer〕 From the viewpoint of the durability of asphalt paving, the modified asphalt is preferably asphalt modified with a thermoplastic elastomer and is a mixture of straight asphalt and a thermoplastic elastomer.

[0013] Examples of thermoplastic elastomers include at least one selected from styrene / butadiene block copolymer (hereinafter also simply referred to as "SB"), styrene / butadiene / styrene block copolymer (hereinafter also simply referred to as "SBS"), styrene / butadiene random copolymer (hereinafter also simply referred to as "SBR"), styrene / isoprene block copolymer (hereinafter also simply referred to as "SI"), styrene / isoprene / styrene block copolymer (hereinafter also simply referred to as "SIS"), styrene / isoprene random copolymer (hereinafter also simply referred to as "SIR"), ethylene / acrylic acid ester copolymer, styrene / ethylene / butylene / styrene copolymer, styrene / ethylene / propylene / styrene copolymer, polyurethane thermoplastic elastomer, polyolefin thermoplastic elastomer, isobutylene / isoprene copolymer, polyisoprene, polychloroprene, synthetic rubber other than those listed above, and natural rubber. Examples of commercially available ethylene / acrylic acid ester copolymers include "Elvaroy" (manufactured by DuPont) and "Lexpar EEA" (manufactured by Mitsubishi Chemical Corporation). Among these, 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.

[0014] Thermoplastic elastomers are considered to have a weight-average molecular weight (M) from the perspective of durability for asphalt pavement. w Preferably, the number is 85,000 or more, more preferably 100,000 or more, even more preferably 120,000 or more, and preferably 2,000,000 or less, more preferably 1,000,000 or less, even more preferably 500,000 or less, and even more preferably 150,000 or less. The weight-average molecular weight is measured by gel permeation chromatography using polystyrene as a standard sample.

[0015] In asphalt modified with thermoplastic elastomer, the ratio of thermoplastic elastomer is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, per 100 parts by mass of straight asphalt, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, from the viewpoint of durability of asphalt pavement.

[0016] Asphalt modified with a thermoplastic elastomer is preferably asphalt that has been pre-modified with a thermoplastic elastomer, from the viewpoint of simplifying the process of manufacturing the asphalt composition. Commercially available asphalt modified with a thermoplastic elastomer can be used. Asphalt modified with thermoplastic elastomers is standardized in the Japan Modified Asphalt Association standard "JMAAS-01:2019" ("Quality and Test Methods for Polymer-Modified Asphalt for Road Pavements"), and from the viewpoint of durability of asphalt pavement, modified type II or modified type III asphalt is preferred, and modified type II asphalt is more preferred.

[0017] [Addition polymerization polymers] The asphalt composition of the present invention comprises an addition polymerization polymer, wherein the hydroxyl value of the addition polymerization polymer is 10 mg KOH / g or more and 60 mg KOH / g or less, and the weight-average molecular weight (M w The value is between 2,500 and 70,000. Addition polymerization polymers refer to polymers that contain constituent units derived from addition polymerizable monomers. Addition polymerization polymers can be produced by carrying out addition polymerization reactions such as radical polymerization and ionic polymerization on addition polymerizable monomers.

[0018] Addition polymerization polymers are preferably polymers whose main chain is composed of hydrocarbon groups, from the viewpoint of reducing the amount of microplastics generated, as well as from the viewpoint of workability and quality stability. That is, addition polymerization polymers preferably have a main chain formed only of carbon-carbon bonds, and do not contain any atoms other than carbon, such as oxygen atoms, nitrogen atoms, or sulfur atoms, in the main chain. "Main chain" refers to the relatively longest bond chain in the addition polymerization polymer. However, the end of the longest bond chain of the addition polymerization polymer is not included in the "main chain". That is, even if one or both ends of the longest bond chain are hydroxyl groups, the polymer is still considered to have a main chain composed of hydrocarbon groups. The addition polymerization polymer is preferably a polymer composed of carbon atoms, oxygen atoms, and hydrogen atoms, and more preferably a polymer composed only of carbon atoms, oxygen atoms, and hydrogen atoms, and free of any other atoms.

[0019] Examples of addition polymerizable monomers include styrenes such as styrene, methylstyrene, α-methylstyrene, β-methylstyrene, tert-butylstyrene, chlorostyrene, chloromethylstyrene, methoxystyrene, styrene sulfonic acid or their salts; (meth)acrylic acid; (meth)acrylic acid esters such as alkyl (meth)acrylates (e.g., alkyl groups with 1 to 18 carbon atoms); olefins such as ethylene, propylene, and butadiene; halovinyls such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as vinyl methyl ether; vinylidenes such as vinylidene chloride; and N-vinyl compounds such as N-vinylpyrrolidone. The addition polymerization polymer may be a homopolymer obtained by addition polymerization of one type of addition polymerizable monomer, or a copolymer obtained by addition polymerization of two or more addition polymerizable monomers. If it is a copolymer, it may be a random copolymer, a block copolymer, or any other type. In this specification, "(meth)acrylic acid" refers to at least one selected from acrylic acid and methacrylic acid, and "(meth)acrylate" refers to at least one selected from acrylate and methacrylate.

[0020] From the viewpoint of reducing the amount of microplastics generated, the addition polymerization polymer has a hydroxyl value of 10 mg KOH / g or more, preferably 15 mg KOH / g or more, more preferably 20 mg KOH / g or more, even more preferably 25 mg KOH / g or more, and 60 mg KOH / g or less, preferably 58 mg KOH / g or less, more preferably 56 mg KOH / g or less, and even more preferably 55 mg KOH / g or less. The hydroxyl value can be measured according to the hydroxyl value measurement method described in JIS-K0070:1992. Methods known to those skilled in the art can be used to adjust the hydroxyl value of addition polymerization polymers to a desired range. Specifically, these methods include using hydroxyl group-containing monomers as addition polymerization monomers, saponifying constituent units derived from vinyl esters, modifying the hydroxyl groups in the main chain, modifying the hydroxyl groups at the ends, and so on. Examples of the hydroxyl group-containing monomers mentioned above include hydroxyalkyl esters of (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 3-hydroxypropyl (meth)acrylate.

[0021] Specific examples of addition polymerization polymers include polybutadiene with hydroxyl groups at both ends, styrene-hydroxyalkyl methacrylate copolymer, polyhydroxypolyolefin, and hydroxyl-modified styrene / butadiene / styrene block copolymer. From the viewpoint of improving the durability of asphalt pavement and reducing the amount of microplastics generated, the addition polymerization polymer is preferably at least one selected from polybutadiene with hydroxyl groups at both ends and styrene-hydroxyalkyl methacrylate copolymer. Polybutadiene with hydroxyl groups at both ends is also preferred from the viewpoint of economy and workability.

[0022] Addition polymerization polymers are considered to have a weight-average molecular weight (M) from the viewpoint of durability for asphalt pavement. w) is 2,500 or more, preferably 3,000 or more, more preferably 3,500 or more, still more preferably 4,000 or more, and from the viewpoint of reducing the generation amount of microplastics, it is 70,000 or less, preferably 50,000 or less, more preferably 30,000 or less, still more preferably 25,000 or less. The addition polymerization type polymer has a weight average molecular weight (M w ) may be 5,000 or more, 6,000 or more, 8,000 or more, 10,000 or more. The addition polymerization type polymer has a weight average molecular weight (M w ) may be 20,000 or less, 18,000 or less, 15,000 or less. The addition polymerization type polymer has a weight average molecular weight (M w ) is preferably 2,500 or more and 50,000 or less, more preferably 3,000 or more and 30,000 or less, more preferably 3,000 or more and 50,000 or less, still more preferably 5,000 or more and 50,000 or less, even more preferably 5,000 or more and 25,000 or less. The weight average molecular weight is measured by gel permeation chromatography using polystyrene as a standard sample.

[0023] In the asphalt composition of the present invention, from the viewpoint of reducing the generation amount of microplastics, the blending amount of the addition polymerization type polymer is preferably 1 part by mass or more, more preferably 2 parts by mass or more, still more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more with respect to 100 parts by mass of asphalt, and preferably 30 parts by mass or less, more preferably 28 parts by mass or less, still more preferably 25 parts by mass or less, even more preferably 23 parts by mass or less.

[0024] Commercially available addition polymerization type polymers may be used, or those synthesized by known production methods described in various publications etc. may be used.

[0025] In the asphalt composition of the present invention, other components such as softening agents, medium temperature agents, anti-stripping agents, and modifiers may be further blended as necessary. 〔Softening agent〕 The asphalt composition may contain a softening agent from the viewpoint of workability. The addition of a softening agent improves the flexibility of the asphalt composition at low temperatures, thereby improving workability. Examples of softening agents include polyolefin waxes such as polyethylene, polypropylene, and ethylene propylene copolymers. From the viewpoint of their effectiveness as softening agents, polyolefin waxes with a low molecular weight, such as a weight-average molecular weight of about 100 to 1,000, are preferred. From the viewpoint of softening effect, the amount of softener blended in the asphalt composition is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and from the viewpoint of durability of the asphalt pavement, it is preferably 2% by mass or less, more preferably less than 1% by mass.

[0026] One preferred embodiment of the asphalt composition of the present invention is, from the viewpoint of improving the durability of asphalt pavement and reducing the amount of microplastics generated, asphalt modified with a thermoplastic elastomer and having a hydroxyl value of 25 mg KOH / g or more and 60 mg KOH / g or less, and a weight-average molecular weight (M w The asphalt composition comprises an addition polymerization polymer having a ratio of 2,500 to 50,000, wherein the amount of the addition polymerization polymer is 3 to 25 parts by mass per 100 parts by mass of asphalt modified with the thermoplastic elastomer.

[0027] [Other ingredients] The asphalt composition of the present invention may contain reactive monomers. Examples of reactive monomers include monomers having one or more reactive functional groups such as hydroxyl groups, carboxyl groups, epoxy groups, primary amino groups, secondary amino groups, and addition polymerizable groups such as carbon-carbon unsaturated bonds. The content of reactive monomers is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less. The asphalt composition of the present invention preferably does not contain reactive monomers.

[0028] [Method for producing asphalt composition] A method for producing the asphalt composition of the present invention preferably includes a step of mixing asphalt with the above-mentioned addition polymerization polymer.

[0029] Specifically, one preferred embodiment of the method for producing an asphalt composition of the present invention is a method for producing an asphalt composition comprising the step of mixing asphalt and an addition polymerization polymer, wherein the hydroxyl value of the addition polymerization polymer is 10 mg KOH / g or more and 60 mg KOH / g or less, and the weight-average molecular weight (M w The present invention relates to a method for producing an asphalt composition in which the ratio is between 2,500 and 70,000.

[0030] Another preferred embodiment of the method for producing the asphalt composition of the present invention is a method for producing the asphalt composition comprising the following steps 1 and 2. Step 1: The hydroxyl value is 10 mg KOH / g or more and 60 mg KOH / g or less, and the weight-average molecular weight (M w A process for producing an addition polymerization polymer in which the ratio is between 2,500 and 70,000. Step 2: Mixing asphalt with addition polymerization polymer.

[0031] Addition polymerization polymers may be commercially available or synthesized by known manufacturing methods described in various publications, etc.

[0032] In the process of mixing asphalt and an addition polymerization polymer, preferably, the asphalt is heated and melted, the addition polymerization polymer is added, and the mixture is stirred and mixed in a commonly used mixer until each component is uniformly dispersed to obtain the asphalt composition. Commonly used mixers include homomixers, dissolvers, paddle mixers, ribbon mixers, screw mixers, planetary mixers, vacuum backflow mixers, roll mills, twin-screw extruders, and the like.

[0033] The mixing temperature of the asphalt and the addition polymerization polymer is preferably 100°C or higher, more preferably 120°C or higher, even more preferably 140°C or higher, and even more preferably 150°C or higher, and preferably 230°C or lower, more preferably 210°C or lower, even more preferably 200°C or lower, and even more preferably 190°C or lower, from the viewpoint of uniformly dispersing the addition polymerization polymer in the asphalt.

[0034] Furthermore, from the viewpoint of efficiently and uniformly dispersing the addition polymerization polymer in the asphalt, the mixing time between the asphalt and the addition polymerization polymer is preferably 0.1 hours or more, more preferably 0.5 hours or more, even more preferably 1.0 hour or more, and even more preferably 1.5 hours or more, and preferably 10 hours or less, more preferably 7 hours or less, even more preferably 5 hours or less, and even more preferably 3 hours or less. The mixing of asphalt and addition polymerization polymers is preferably carried out in an open atmosphere from the viewpoint of workability. An open atmosphere means carrying out the mixing in the presence of air.

[0035] [Asphalt mixture] The asphalt composition of the present invention is a binder composition, and aggregate is added to this asphalt composition to form an asphalt mixture, which is then used for paving. In other words, the asphalt composition of the present invention is suitable for paving, and is particularly suitable for road paving. The asphalt mixture of the present invention contains the aforementioned asphalt composition and aggregate. In other words, the asphalt mixture contains at least asphalt, an addition polymerization polymer, and aggregate.

[0036] 〔aggregate〕 As aggregate, crushed stone, pebbles, gravel, sand, recycled aggregate, ceramics, etc., can be arbitrarily selected and used. In addition, both coarse aggregate with a particle size of 2.36 mm or more and fine aggregate with a particle size of less than 2.36 mm can be used as aggregate. Examples of coarse aggregate include crushed stone with a particle size range of 2.36 mm or more and less than 4.75 mm, crushed stone with a particle size range of 4.75 mm or more and less than 12.5 mm, crushed stone with a particle size range of 12.5 mm or more and less than 19 mm, and crushed stone with a particle size range of 19 mm or more and less than 31.5 mm. The fine aggregate is preferably fine aggregate with a particle size of 0.075 mm or more and less than 2.36 mm. Examples of fine aggregate include river sand, hill sand, mountain sand, sea sand, crushed sand, fine sand, screenings, crushed stone dust, silica sand, artificial sand, glass cullet, foundry sand, and recycled aggregate crushed sand. The particle size values ​​mentioned above are those specified in JIS A5001:2008. Among these, a combination of coarse aggregate and fine aggregate is preferred.

[0037] The fine aggregate may also contain fillers with a particle size of less than 0.075 mm (e.g., sand). Examples of fillers include sand, fly ash, calcium carbonate, and slaked lime. Of these, calcium carbonate is preferred from the viewpoint of improving dry strength.

[0038] From the viewpoint of improving drying strength, the average particle size of the filler is preferably 0.001 mm or more, more preferably 0.05 mm or less, more preferably 0.03 mm or less, and even more preferably 0.02 mm or less. The average particle size of the filler can be measured with a laser diffraction particle size distribution analyzer. Here, the average particle size refers to the average particle size at 50% volume cumulative.

[0039] [Method for measuring the average particle size of fillers] The average particle size of the filler was measured using the LA-950 laser diffraction particle size distribution analyzer (manufactured by Horiba, Ltd.) under the following conditions. • Measurement method: Flow method • Dispersion medium: Ethanol • Sample preparation: 2 mg / 100 mL • Dispersion method: stirring, built-in ultrasonic for 1 minute

[0040] From the viewpoint of durability of asphalt pavement, the mass ratio of coarse aggregate to fine aggregate is preferably 10 / 90 or more, more preferably 20 / 80 or more, even more preferably 30 / 70 or more, and preferably 90 / 10 or less, more preferably 80 / 20 or less, and even more preferably 70 / 30 or less.

[0041] The following are examples of suitable formulations for asphalt mixtures. (1) An example of an asphalt mixture includes, for example, 30% to less than 45% by volume of coarse aggregate, 30% to 50% by volume of fine aggregate, and 5% to 10% by volume of asphalt composition (fine-grained asphalt). (2) An example of an asphalt mixture includes, for example, 45% by volume or more and less than 70% by volume of coarse aggregate, 20% by volume or more and 45% by volume of fine aggregate, and 3% by volume or more and 10% by volume of asphalt composition (dense-graded asphalt). (3) An example of an asphalt mixture includes, for example, 70% to 80% by volume of coarse aggregate, 10% to 20% by volume of fine aggregate, and 3% to 10% by volume of asphalt composition (porous asphalt).

[0042] The asphalt mixture may also contain other components as needed. In addition, the mixing ratio of asphalt in conventional asphalt mixtures containing aggregate and asphalt is usually determined according to the optimal amount of asphalt found in the "Asphalt Composition Mix Design" described in the "Pavement Design and Construction Guidelines" published by the Japan Road Association. In this invention, the above-mentioned optimal amount of asphalt corresponds to the total amount of asphalt and addition polymerization polymer. However, it is not necessary to limit the method to the method described in the "Guidelines for Pavement Design and Construction," and it may be determined by other methods.

[0043] [Method for producing asphalt mixture] The present invention provides a method for producing an asphalt mixture, comprising the step of mixing heated aggregate, asphalt, and an addition polymerization polymer.

[0044] Specific methods for manufacturing asphalt mixtures include conventional methods such as the plant mix method and the premix method. Both methods involve adding asphalt and addition polymerization polymers to heated aggregate. Addition methods include, for example, the premix method in which asphalt and addition polymerization polymers are pre-dissolved, or the plant mix method in which addition polymerization polymers are added to asphalt. Among these, the premix method is preferred from the viewpoint of durability of asphalt pavement. More specifically, the method for producing an asphalt mixture preferably involves the following steps in the mixing process: (i) After adding and mixing asphalt to heated aggregate, an addition polymerization polymer is added and mixed. (ii) Adding and mixing asphalt and an addition polymerization polymer to heated aggregate simultaneously, (iii) Add and mix the mixture of preheated asphalt and addition polymerization polymer to the heated aggregate. Among these, method (iii) is preferred from the viewpoint of the durability of the asphalt pavement.

[0045] The above-mentioned asphalt composition can be suitably used as the mixture of preheated and mixed asphalt and addition polymerization polymer in method (iii).

[0046] The temperature of the heated aggregate in methods (i) to (iii) is preferably 130°C or higher, more preferably 150°C or higher, even more preferably 170°C or higher, and even more preferably 180°C or higher, from the viewpoint of durability of the asphalt pavement, and preferably 230°C or lower, more preferably 210°C or lower, and even more preferably 200°C or lower, from the viewpoint of preventing thermal deterioration of the asphalt.

[0047] In the mixing process, from the viewpoint of durability of the asphalt pavement, the mixing temperature is preferably 130°C or higher, more preferably 150°C or higher, even more preferably 170°C or higher, and even more preferably 180°C or higher. From the viewpoint of preventing thermal degradation of the asphalt, the temperature is preferably 230°C or lower, more preferably 210°C or lower, and even more preferably 200°C or lower. The mixing time in the mixing process is not particularly limited, but is preferably 30 seconds or more, more preferably 1 minute or more, even more preferably 2 minutes or more, and even more preferably 5 minutes or more. The upper limit of the time is not particularly limited, but is preferably about 30 minutes.

[0048] From the viewpoint of the durability of the asphalt pavement, the method for producing the asphalt mixture preferably includes a step of holding the obtained mixture at the above-mentioned mixing temperature after the mixing step. During the holding process, the mixture may be further mixed, but it is sufficient to maintain a temperature above the aforementioned temperature. In the holding process, the mixing temperature is preferably 130°C or higher, more preferably 150°C or higher, even more preferably 170°C or higher, and even more preferably 180°C or higher. From the viewpoint of preventing thermal degradation of the asphalt composition, it is preferably 230°C or lower, more preferably 210°C or lower, and even more preferably 200°C or lower. The holding time in the holding process 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 for example, it is about 5 hours.

[0049] [Road paving methods] The asphalt mixture of the present invention is suitable for road paving, and as described above, the asphalt mixture obtained by adding aggregate to the asphalt composition is used for road paving. The road paving method includes the step of applying the aforementioned asphalt mixture to the road to form an asphalt paving material layer. Specifically, the road paving method includes the step of obtaining an asphalt mixture by mixing asphalt, the aforementioned addition polymerization polymer, and aggregate (step 1), and the step of applying the asphalt mixture obtained in step 1 to the road to form an asphalt paving material layer (step 2). The asphalt paving material layer is usually a base layer or a surface layer, and from the viewpoint of reducing the amount of microplastics generated, it is preferably a surface layer.

[0050] The asphalt mixture can be compacted using a known construction machinery setup and a similar method. When used as a heated asphalt mixture, the compaction temperature is preferably 100°C or higher, more preferably 120°C or higher, even more preferably 130°C or higher, and preferably 200°C or lower, more preferably 180°C or lower, from the viewpoint of durability of the asphalt pavement.

[0051] [Asphalt modifier] The asphalt modifier of the present invention has a hydroxyl value of 10 mg KOH / g or more and 60 mg KOH / g or less, and a weight-average molecular weight (M w It consists of an addition polymerization polymer in which the ratio is between 2,500 and 70,000. The asphalt modifier of the present invention can be used, for example, by mixing it with asphalt in an amount of 1 to 30 parts by mass per 100 parts by mass of asphalt to obtain an asphalt composition. After adding aggregate to the obtained asphalt composition to make an asphalt mixture, it can be used for paving. The asphalt modifier of the present invention can be suitably used as a modifier to be incorporated into an asphalt mixture containing aggregate. [Examples]

[0052] The physical properties of the polymer were measured and evaluated using the following method. [Measurement method] [Hydroxyl value of polymers] The hydroxyl value of the polymer was 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)).

[0053] [Weight-average molecular weight of polymers (M w )〕 The weight-average molecular weight was determined by gel permeation chromatography (GPC) using the following method. (1) Preparation of sample solution The sample was dissolved in tetrahydrofuran at 40°C to a concentration of 0.5 g / 100 mL. This solution was then filtered using a PTFE type membrane filter "DISMIC-25JP" (manufactured by Toyo Roshi Co., Ltd.) with a pore size of 0.20 μm to remove insoluble components and obtain the sample solution. (2) Molecular weight measurement Using the measurement apparatus and analytical column described below, tetrahydrofuran was flowed as the eluent at a flow rate of 1 mL / min, and the column was stabilized in a constant temperature bath at 40°C. 100 μL of the sample solution was injected into the column and measurements were performed. The molecular weight of the sample was calculated based on a pre-prepared calibration curve. The calibration curve used included several types of monodisperse polystyrene (A-500 (5.0 × 10) manufactured by Tosoh Corporation). 2 ), A-1000 (1.01 x 10 3 ), A-2500 (2.63 x 10 3 ), A-5000 (5.97 x 10 3 ), F-1 (1.02×10 4 ), F-2 (1.81×10 4 ), F-4 (3.97×10 4 ), F-10 (9.64×10 4 ), F-20 (1.90×10 5 ), F-40 (4.27×10 5 ), F-80 (7.06×10 5 ), F-128 (1.09×10 6 The sample used was prepared using )) as a standard sample. The values ​​in parentheses indicate the molecular weight. Measuring device: "HLC-8220GPC" (manufactured by Tosoh Corporation) Analysis columns: "TSKgel GMHXL" + "TSKgel G3000HXL" (manufactured by Tosoh Corporation)

[0054] Manufacturing Example 1 (Addition Polymer B) A three-pronged flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple was purged with nitrogen, 300 g of xylene was added, and the mixture was heated to 125°C and refluxed. A mixture of 850 g of styrene, 150 g of 2-hydroxyethyl methacrylate, and 300 g of dibutyl peroxide was added dropwise from a dropping funnel over 2 hours. Polymerization was carried out under reflux for 1 hour at 125°C, and then at 160°C for another hour. After that, the solvent was removed by distillation under reduced pressure at 200°C for 3 hours to obtain addition polymerization polymer B (styrene-hydroxyethyl methacrylate random copolymer (1)). Addition polymerization polymer B had a weight-average molecular weight of 5,000 and a hydroxyl value of 54 mgKOH / g.

[0055] Manufacturing Example 2 (Addition Polymer C) A three-pronged flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple was purged with nitrogen, 300 g of xylene was added, and the temperature was raised to 130°C and refluxed. A mixture of 850 g of styrene, 150 g of 2-hydroxyethyl methacrylate, and 150 g of dibutyl peroxide was added dropwise from a dropping funnel over 2 hours. Polymerization was carried out under reflux for 1 hour at 130°C, and then at 160°C for another hour. After that, the solvent was removed by distillation under reduced pressure at 200°C for 3 hours to obtain addition polymerization polymer C (styrene-hydroxyethyl methacrylate random copolymer (2)). The addition polymerization polymer C had a weight-average molecular weight of 17,500 and a hydroxyl value of 49 mgKOH / g.

[0056] Manufacturing Example 3 (Addition Polymer D) A three-pronged flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple was purged with nitrogen, 300 g of xylene was added, and the mixture was heated to 135°C and refluxed. A mixture of 850 g of styrene, 150 g of 2-hydroxyethyl methacrylate, and 30 g of dibutyl peroxide was added dropwise from a dropping funnel over 2 hours. Polymerization was carried out under reflux for 1 hour at 135°C, and then at 160°C for another hour. After that, the solvent was removed by distillation under reduced pressure at 200°C for 3 hours to obtain addition polymerization polymer D (styrene-hydroxyethyl methacrylate random copolymer (3)). The addition polymerization polymer D had a weight-average molecular weight of 75,000 and a hydroxyl value of 42 mgKOH / g.

[0057] Example 1 As a binder mixture, 1,000 g of modified type II asphalt (manufactured by Toa Road Industry Co., Ltd.) heated to 180°C was placed in a 3 L stainless steel container and stirred at 100 rpm. 30 g of addition polymerization polymer A (3 parts by mass per 100 parts by mass of asphalt) was gradually added, and the mixture was stirred at 300 rpm for 2 hours to prepare asphalt composition (AS-1).

[0058] Next, 15 kg of aggregate heated to 180°C (see below for aggregate composition) was placed in an asphalt mixer and mixed at 180°C for 60 seconds. Next, 847 g of the asphalt composition (AS-1) was added and mixed for 2 minutes in an asphalt mixer. The resulting asphalt mixture was stored at 180°C for 2 hours, then filled into a 300 × 300 × 50 mm mold, and subjected to 25 rotations of pressure treatment using a roller compactor (manufactured by Iwata Industries Co., Ltd.) at a temperature of 150°C and a load of 0.44 kPa to produce asphalt mixture (M-1) as a test specimen.

[0059] <Composition of aggregates> Crushed stone No. 6: 50.9 parts by mass Crushed sand 1 10.4 parts by mass Crushed sand 2 22.1 parts by mass Fine sand 10.4 parts by mass Stone powder (calcium carbonate) 6.2 parts by mass Passed mass%: Sieve mesh size 15 mm: 100% by mass Sieve mesh size 10 mm: 85.6% by mass Sieve mesh size 5 mm: 49.7% by mass Sieve mesh size 2.5 mm: 44.6% by mass Sieve mesh size 1.2 mm: 31.6% by mass Sieve mesh size 0.6 mm: 21.3% by mass Sieve mesh size 0.3 mm: 12.7% by mass Sieve mesh size 0.15 mm: 7.1% by mass

[0060] Examples 2-3 Asphalt compositions (AS-2) to (AS-3) were prepared in the same manner as in Example 1, except that the amount of addition polymerization polymer A was changed to 100 g (10 parts by mass per 100 parts by mass of asphalt) or 200 g (20 parts by mass per 100 parts by mass of asphalt). Asphalt mixtures (M-2) to (M-3) were obtained as test specimens in the same manner as in Example 1, except that 847 g of asphalt composition (AS-1) was replaced with 905 g of asphalt composition (AS-2) or 987 g of asphalt composition (AS-3).

[0061] Examples 4-5 Except for replacing addition polymerization polymer A with addition polymerization polymers B to C, the same procedure as in Example 2 was used to obtain asphalt compositions (AS-4) to (AS-5) and asphalt mixtures (M-4) to (M-5) as test specimens.

[0062] Example 6 Except for changing the modified type II asphalt to straight asphalt, an asphalt composition (AS-6) and an asphalt mixture (M-6) were obtained as test specimens in the same manner as in Example 5.

[0063] Comparative Example 1 An asphalt composition (AS-a1) was prepared in the same manner as in Example 2, except that addition polymerization polymer A was not included. In Example 2, an asphalt mixture (M-a1) was obtained as a test specimen in the same manner as in Example 2, except that 905 g of asphalt composition (AS-2) was replaced with 822 g of asphalt composition (AS-a1).

[0064] Comparative Examples 2-6 In Example 2, asphalt compositions (AS-a2) to (AS-a6) and asphalt mixtures (M-a2) to (M-a6) were obtained in the same manner as in Example 2, except that addition polymerization polymer A was replaced with addition polymerization polymers D to H, respectively.

[0065] [evaluation] <Measurement of microplastic generation> The test specimens were immersed in hot water set to 60°C in a 60°C constant temperature chamber. A wheel tracking test machine (manufactured by Iwata Industries Co., Ltd.) was used to conduct the test under the following conditions: load of 150 kg, ground pressure of 0.9 MPa, water temperature of 60°C, and speed of 15 cycles / minute. The test was stopped after 1,200 cycles (80 minutes). After dewatering and drying the water tank, the accumulated wear particles were collected and weighed, and this was defined as the "amount of microplastic generated." The obtained value was 0.3 m³. 2 This is the amount generated per 100m 2 I converted it to an average of a certain amount.

[0066] <Amount of rutting> The test specimens were immersed in hot water set to 60°C in a 60°C constant temperature chamber. A wheel tracking tester (manufactured by Iwata Industries Co., Ltd., load 1,370N, wheel width 47mm, line pressure 291.5N / cm) was used to move a wheel back and forth over the specimen at a speed of 15 times / minute, and the displacement was measured after 2,500 passes. Other measurement conditions followed the "B003 Wheel Tracking Test" described in the "Pavement Survey and Testing Methods Handbook" published by the Japan Road Association. The results are shown in Table 1.

[0067] [Table 1]

[0068] The asphalt and addition polymerization polymers used in the examples and comparative examples are as follows: (*) Asphalt A: Modified Type II asphalt (asphalt modified with thermoplastic elastomer) (manufactured by Toa Road Industry Co., Ltd.) (*) Asphalt B: Straight asphalt (manufactured by Toa Road Industry Co., Ltd.) (*) Addition polymerization polymer A: Polybutadiene with hydroxyl groups at both ends "G-3000" (manufactured by Nippon Soda Co., Ltd.) (*) Addition polymerization polymer B: Styrene-hydroxyethyl methacrylate random copolymer (1) (*) Addition polymerization polymer C: Styrene-hydroxyethyl methacrylate random copolymer (2) (*) Addition polymerization polymer D: Styrene-hydroxyethyl methacrylate random copolymer (3) (*) Addition polymerization polymer E: Polypropylene "High Wax NP056" (manufactured by Mitsui Chemicals, Inc.) (*) Addition polymerization polymer F: Hydroxyl group modified paraffin "Paracol 6470" (manufactured by Nippon Seiro Co., Ltd.) (*) Addition polymerization polymer G: Polybutadiene with hydroxyl groups at both ends "G-1000" (manufactured by Nippon Soda Co., Ltd.) (*) Addition polymerization polymer H: Terminal hydroxyl group polyethylene glycol "Uniox M-1000" (manufactured by NOF Corporation)

[0069] Comparative Example 1, which does not contain an addition polymerization polymer, and Comparative Examples 2-6, which contain polymers other than the specific addition polymerization polymer, failed to sufficiently reduce the amount of microplastics generated, and the durability of the asphalt pavement was insufficient. In contrast, the present invention demonstrates that an asphalt composition containing a predetermined amount of a specific addition polymerization polymer can reduce the amount of microplastics generated without impairing the durability of the asphalt pavement.

Claims

1. An asphalt mixture comprising an asphalt composition comprising asphalt and an addition polymerization polymer, and aggregate, The addition polymerization polymer is at least one selected from polybutadiene with hydroxyl groups at both ends and styrene-hydroxyalkyl methacrylate copolymer. The hydroxyl value of the addition polymerization polymer is 10 mg KOH / g or more and 60 mg KOH / g or less, and the weight-average molecular weight (Mw) is 4,000 or more and 25,000 or less. The asphalt content in the aforementioned asphalt composition is 60% by mass or more. In the aforementioned asphalt composition, the addition polymerization polymer is blended in an amount of 1 to 30 parts by weight per 100 parts by weight of the asphalt. An asphalt mixture in which the mass ratio of coarse aggregate to fine aggregate is 20 / 80 or more and 80 / 20 or less.

2. The asphalt mixture according to claim 1, wherein the asphalt is straight asphalt or modified asphalt.

3. The asphalt mixture according to claim 2, wherein the modified asphalt is asphalt modified with a thermoplastic elastomer.

4. The asphalt mixture according to claim 3, wherein the thermoplastic elastomer is at least one selected from styrene / butadiene block copolymer, styrene / butadiene / styrene block copolymer, styrene / butadiene random copolymer, styrene / isoprene block copolymer, styrene / isoprene / styrene block copolymer, styrene / isoprene random copolymer, and ethylene / acrylic acid ester copolymer.

5. A road paving method comprising the step of applying the asphalt mixture described in any one of claims 1 to 4 to a road to form an asphalt coating layer.

6. A method for producing an asphalt mixture, comprising the step of mixing heated aggregate, asphalt, and an addition polymerization polymer, The aforementioned asphalt mixture is an asphalt mixture comprising an asphalt composition made by blending asphalt and an addition polymerization polymer, and aggregate. The addition polymerization polymer is at least one selected from polybutadiene with hydroxyl groups at both ends and styrene-hydroxyalkyl methacrylate copolymer. The hydroxyl value of the addition polymerization polymer is 10 mg KOH / g or more and 60 mg KOH / g or less, and the weight-average molecular weight (Mw) is 4,000 or more and 25,000 or less. The amount of asphalt in the asphalt composition is 60% by mass or more. In the aforementioned asphalt composition, the addition polymerization polymer is blended in an amount of 1 to 30 parts by weight per 100 parts by weight of the asphalt. A method for producing an asphalt mixture, wherein the mass ratio of coarse aggregate to fine aggregate in the asphalt mixture is 20 / 80 or more and 80 / 20 or less.

7. The method for producing an asphalt mixture according to claim 6, wherein the temperature of the heated aggregate is 130°C or higher and 230°C or lower.

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