Asphalt Modifier

Abstract

To provide an asphalt modifier that gives an asphalt composition having high storage stability, allowing polyester to be uniformly dispersed in asphalt, even after stored at high temperature for a long time.SOLUTION: An asphalt modifier comprises a polyester that contains a constitutional unit derived from an alcohol component, containing a C4-12 aliphatic diol (A) of 50 mol% or more and 99 mol% or less and an alkylene oxide-added bisphenol A (B) of 1 mol% or more and 50 mol% or less, and a constitutional unit derived from a carboxylic acid component.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an asphalt modifier and an asphalt composition. [Background technology]

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

[0003] Patent Document 1 discloses an asphalt composition for road paving that has excellent dry strength, water immersion strength, and bending strength. The asphalt composition contains asphalt, a predetermined amount of polyester resin, and aggregate, and the polyester resin has structural units derived from an alcohol component including a predetermined amount of an alkylene oxide adduct of bisphenol A and structural units derived from a carboxylic acid component including a predetermined amount of one or more acids selected from fumaric acid, maleic acid, terephthalic acid, and isophthalic acid, and the asphalt composition has a predetermined softening point, glass transition point, number average molecular weight, and acid value. Patent Document 2 discloses an asphalt composition containing asphalt, a polyester resin, and a dispersant, which has excellent storage stability at high temperatures. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 10,662,110 [Patent Document 2] U.S. Patent Application Publication No. 2019-0233647 Summary of the Invention [Problem to be solved by the invention]

[0005] In the asphalt composition for road paving described in Patent Document 1, when polyester is mixed with asphalt, the difference in specific gravity between the asphalt and polyester prevents the mixture from remaining homogeneous, resulting in polyester precipitation, which can result in variations in the strength of the asphalt pavement. In the asphalt composition described in Patent Document 2, adding a dispersant to the asphalt composition reduces the dispersed diameter of the polyester and suppresses the formation of polyester precipitates in the asphalt, enabling the creation of pavements with uniform strength. However, if the asphalt composition is stored at high temperatures for several hours or longer, the dispersant's ability to adsorb to the polyester decreases, which can lead to a loss of uniformity in the strength of the asphalt pavement. It often takes several hours or more from the time the asphalt mixture is produced at the construction company's plant until it is transported to the paving site and applied to the road, so further improvements in storage stability are required. The present invention relates to an asphalt modifier and an asphalt composition for obtaining an asphalt composition having excellent storage stability in which a polyester is uniformly dispersed in the asphalt even after long-term storage at high temperatures. [Means for solving the problem]

[0006] The present inventors have discovered that the above problems can be solved by blending a specific polyester into an asphalt composition containing asphalt and a polyester. That is, the present invention includes the following [1] to [2]. [1] An asphalt modifier comprising a polyester containing structural units derived from an alcohol component, including 50 mol% to 99 mol% of an aliphatic diol (A) having 4 to 12 carbon atoms and 1 mol% to 50 mol% of an alkylene oxide adduct of bisphenol A (B), and structural units derived from a carboxylic acid component. [2] An asphalt composition containing the asphalt modifier described in [1] above. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an asphalt modifier for obtaining an asphalt composition having excellent storage stability in which a polyester is uniformly dispersed in asphalt even after long-term storage at high temperatures, and an asphalt composition. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Asphalt modifier] The asphalt modifier of the present invention comprises a polyester containing structural units derived from an alcohol component, which contains 50 mol % to 99 mol % of an aliphatic diol (A) having from 4 to 12 carbon atoms and 1 mol % to 50 mol % of an alkylene oxide adduct of bisphenol A (B), and structural units derived from a carboxylic acid component.

[0009] The reason why the present invention has an effect is not clear, but is thought to be as follows. It is believed that the aliphatic diol-derived structural units of the polyester that constitutes the asphalt modifier of the present invention interact with low-molecular-weight components with aliphatic alkyl structures in the asphalt to form a complex. This complex maintains the stability of the interface between the asphalt and the polyester, and since the difference in specific gravity between the polyester and asphalt is small, it is believed that polyester precipitation is unlikely to occur. In addition, because the polyester directly forms a complex with the constituent components of the asphalt, it is believed that the material will remain stable even after long-term storage at high temperatures.

[0010] The definitions of various terms used in this specification are shown below. In the polyester, 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" encompasses not only the carboxylic acid itself, but also anhydrides that decompose to produce an acid during the reaction, 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.

[0011] <Polyester> The polyester constituting the asphalt modifier of the present invention will now be described. The polyesters can be used alone or in combination of two or more. From the viewpoint of storage stability, the polyester contains constitutional units derived from an alcohol component containing 50 mol % to 99 mol % of an aliphatic diol (A) having from 4 to 12 carbon atoms and 1 mol % to 50 mol % of an alkylene oxide adduct of bisphenol A (B), and constitutional units derived from a carboxylic acid component. The alcohol component, the carboxylic acid component, and the physical properties of the polyester will be described below.

[0012] (alcohol content) The carbon number of the aliphatic diol (A) having 4 to 12 carbon atoms (hereinafter referred to as "aliphatic diol (A)") is preferably 5 or more, more preferably 6 or more, from the viewpoint of storage stability, and is preferably 10 or less, more preferably 8 or less. Examples of the aliphatic diol (A) include 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-butenediol, 1,3-butanediol, neopentyl glycol, 1,10-decanediol, and 1,12-dodecanediol, and 1,6-hexanediol is preferred. The aliphatic diol (A) can be used alone or in combination of two or more. From the viewpoint of storage stability, the content of the aliphatic diol (A) in the alcohol component is 50 mol% or more, preferably more than 50 mol%, more preferably 52 mol% or more, even more preferably 55 mol% or more, relative to 100 mol% of the alcohol component, and is 99 mol% or less, preferably 95 mol% or less, more preferably 85 mol% or less, even more preferably 70 mol% or less.

[0013] The alkylene oxide adduct of bisphenol A (B) includes an alkylene oxide adduct of bisphenol A represented by the following formula (I).

[0014] [ka]

[0015] [In the formula, OR 1 and R 1 O is alkylene oxide and R 1 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 [2,2-bis(4-hydroxyphenyl)propane] and an ethylene oxide adduct of bisphenol A. The alkylene oxide adduct of bisphenol A (B) can be used alone or in combination of two or more. From the viewpoint of durability of asphalt pavement, the content of the alkylene oxide adduct of bisphenol A (B) in the alcohol component is 1 mol% or more, preferably 5 mol% or more, more preferably 15 mol% or more, even more preferably 30 mol% or more, relative to 100 mol% of the alcohol component, and is 50 mol% or less, preferably less than 50 mol%, more preferably 48 mol% or less, even more preferably 45 mol% or less.

[0016] The molar ratio of the aliphatic diol (A) to the alkylene oxide adduct of bisphenol A (B) in the alcohol component [(A) / (B)] is preferably 1.2 or more, more preferably 1.3 or more, even more preferably 1.4 or more, from the viewpoint of storage stability, and is preferably 9 or less, more preferably 5 or less, even more preferably 3 or less.

[0017] The alcohol component may contain an alcohol component other than the aliphatic diol (A) and the alkylene oxide adduct (B) of bisphenol A. Specific examples include an aliphatic diol other than the aliphatic diol (A), an aromatic diol other than the alkylene oxide adduct (B) of bisphenol A, and a polyhydric alcohol having a valence of 3 to 8. These alcohol components may be used alone or in combination of two or more. Examples of polyhydric alcohols having a valence of 3 to 8 include trihydric alcohols such as glycerin.

[0018] The alcohol component may contain an aliphatic monoalcohol (C) from the viewpoint of storage stability. The aliphatic monoalcohol (C) preferably has 12 or more carbon atoms, more preferably 14 or more carbon atoms, and even more preferably 16 or more carbon atoms, and preferably has 22 or less carbon atoms, more preferably 21 or less carbon atoms, and even more preferably 20 or less carbon atoms. Examples of the aliphatic monoalcohol (C) include lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, arachidyl alcohol, and docosanol, with stearyl alcohol being preferred. When an aliphatic monoalcohol (C) is contained, the content thereof is preferably 0.1 mol% or more, more preferably 1 mol% or more, even more preferably 5 mol% or more, and preferably 20 mol% or less, more preferably 15 mol% or less, even more preferably 10 mol% or less, relative to 100 mol% of the total alcohol components.

[0019] A preferred embodiment of the polyester of the present invention is one in which the alcohol component consists essentially of an aliphatic diol (A) and an alkylene oxide adduct of bisphenol A (B).

[0020] (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 can be used alone or in combination of two or more. From the viewpoint of storage stability, the number of carbon atoms in the main chain of the aliphatic dicarboxylic acid is preferably 3 or more, more preferably 4 or more, and preferably 10 or less, more preferably 6 or less. The number of carbon atoms in the main chain of the aliphatic dicarboxylic acid includes the carbon atoms forming the carboxy group. The aliphatic dicarboxylic acid may be either a saturated aliphatic dicarboxylic acid or an unsaturated aliphatic dicarboxylic acid, with unsaturated aliphatic dicarboxylic acids being preferred. Note that the saturated aliphatic dicarboxylic acid is an aliphatic dicarboxylic acid that does not have an unsaturated bond in its main chain, while the unsaturated aliphatic acid is an aliphatic dicarboxylic acid that has an unsaturated bond in its main chain. Specific examples of saturated aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid. Specific examples of unsaturated aliphatic dicarboxylic acids include fumaric acid, maleic acid, citraconic acid, itaconic acid, and glutaconic acid. Aliphatic dicarboxylic acids also include succinic acids substituted with an alkyl group having from 1 to 20 carbon atoms or an alkenyl group having from 2 to 20 carbon atoms, such as dodecylsuccinic acid, dodecenylsuccinic acid, and octenylsuccinic acid. Examples of aromatic dicarboxylic acids include terephthalic acid, phthalic acid, isophthalic acid, naphthalenedicarboxylic acid, etc. Among these, one or more selected from terephthalic acid and isophthalic acid is preferred, and terephthalic acid is more preferred. Examples of the polycarboxylic acid having a valence of 3 to 6 include tricarboxylic acids such as trimellitic acid, 2,5,7-naphthalenetricarboxylic acid, and pyromellitic acid.

[0021] From the viewpoint of storage stability, the carboxylic acid component preferably contains one or more selected from fumaric acid and maleic acid, more preferably fumaric acid. The total content of at least one selected from fumaric acid and maleic acid in the carboxylic acid component is preferably 10 mol% or more, more preferably 40 mol% or more, and even more preferably 80 mol% or more, based on 100 mol% of the carboxylic acid component, and is 100 mol% or less, preferably 95% or less.

[0022] The carboxylic acid component may contain an aliphatic monocarboxylic acid (D) from the viewpoint of storage stability. The aliphatic monocarboxylic acid (D) preferably has 12 or more carbon atoms, more preferably 14 or more carbon atoms, and even more preferably 16 or more carbon atoms, and preferably has 22 or less carbon atoms, more preferably 21 or less carbon atoms, and even more preferably 20 or less carbon atoms. The aliphatic monocarboxylic acid (D) includes saturated aliphatic monocarboxylic acids and unsaturated monocarboxylic acids, preferably saturated aliphatic monocarboxylic acids. Examples of saturated aliphatic monocarboxylic acids include lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid, preferably stearic acid. Examples of unsaturated aliphatic monocarboxylic acids include oleic acid, linoleic acid, and linolenic acid. When the carboxylic acid component contains an aliphatic monocarboxylic acid (D), the content thereof is preferably 0.1 mol% or more, more preferably 1 mol% or more, even more preferably 5 mol% or more, and preferably 20 mol% or less, more preferably 15 mol% or less, even more preferably 10 mol% or less, relative to 100 mol% of the total carboxylic acid components.

[0023] The alcohol component and the carboxylic acid component may contain one or more selected from the aforementioned aliphatic monoalcohol (C) and the aforementioned aliphatic monocarboxylic acid (D). In this case, either the aliphatic monoalcohol (C) or the aliphatic monocarboxylic acid (D) is preferably contained, and the aliphatic monocarboxylic acid (D) is more preferably contained.

[0024] Preferred embodiments of the polyester of the present invention include an embodiment in which the carboxylic acid component is composed substantially only of an aliphatic dicarboxylic acid, and an embodiment in which the carboxylic acid component is composed substantially only of an aliphatic dicarboxylic acid and an aliphatic monocarboxylic acid.

[0025] (molar ratio of carboxylic acid component to alcohol component) From the viewpoint of the durability of asphalt pavement, the equivalent ratio of the carboxyl groups of the carboxylic acid component to the hydroxyl groups of the alcohol component (COOH groups / OH groups) is preferably 0.6 or more, more preferably 0.7 or more, even more preferably 0.8 or more, and is preferably 1.3 or less, more preferably 1.2 or less, even more preferably 1.1 or less.

[0026] The polyester of the present invention may be modified to an extent that does not substantially impair its properties. Specific examples of modified polyesters include polyesters grafted or blocked with phenol, urethane, epoxy, or the like, by methods described in JP-A Nos. 11-133668, 10-239903, and 8-20636. A preferred modified polyester is a urethane-modified polyester obtained by urethane-extending polyester with a polyisocyanate compound.

[0027] (Physical properties of polyester) From the viewpoint of storage stability, the acid value of the polyester is preferably 3 mgKOH / g or more, more preferably 8 mgKOH / g or more, even more preferably 10 mgKOH / g or more, and is preferably 60 mgKOH / g or less, more preferably 40 mgKOH / g or less, even more preferably 30 mgKOH / g or less. From the same viewpoint, the hydroxyl value of the polyester is preferably 10 mgKOH / g or more, more preferably 12 mgKOH / g or more, even more preferably 15 mgKOH / g or more, and is preferably 50 mgKOH / g or less, more preferably 40 mgKOH / g or less, even more preferably 30 mgKOH / g or less. From the same viewpoint, the number average molecular weight of the polyester is preferably 1,500 or more, more preferably 2,000 or more, even more preferably 2,300 or more, and preferably 8,000 or less, more preferably 3,000 or less, even more preferably less than 3,000, even more preferably 2,900 or less. From the same viewpoint, the weight average molecular weight of the polyester is preferably 5,000 or more, more preferably 6,000 or more, even more preferably 7,000 or more, and preferably 60,000 or less, more preferably 10,000 or less, even more preferably 9,000 or less. From the same viewpoint, the peak top molecular weight of the polyester is preferably 4,000 or more, more preferably 4,500 or more, even more preferably 5,000 or more, and preferably 25,000 or less, more preferably 9,000 or less, even more preferably 8,000 or less. From the same viewpoint, the polydispersity (Mw / Mn) of the polyester is preferably 2.5 or more, more preferably 2.9 or more, and preferably 8.5 or less, more preferably 8.0 or less, and even more preferably 4.0 or less.

[0028] The acid value, hydroxyl value, number average molecular weight, weight average molecular weight, peak top molecular weight, and polydispersity can be measured by the methods described in the Examples. The acid value, hydroxyl value, number average molecular weight, weight average molecular weight, peak top molecular weight, and polydispersity can be adjusted by the raw material monomer composition, the amount of catalyst, reaction conditions, etc.

[0029] (Polyester manufacturing method) The method for producing the polyester is not particularly limited, and for example, the polyester can be produced by polycondensing the alcohol component and the carboxylic acid component described above. The blending amounts of the alcohol component and the carboxylic acid are such that the molar ratio of the structural units derived from the carboxylic acid component to the structural units derived from the alcohol component [carboxylic acid component / alcohol component] falls within the above-mentioned numerical range. The temperature of the polycondensation reaction is not particularly limited, but from the viewpoint of reactivity, it is preferably 160° C. or higher, more preferably 190° C. or higher, even more preferably 200° C. or higher, and preferably 260° C. or lower, more preferably 250° C. or lower, even more preferably 240° C. or lower. The polycondensation may be carried out in an inert gas atmosphere.

[0030] From the viewpoint of reaction rate, a tin(II) compound having no Sn-C bond, such as tin(II) di(2-ethylhexanoate), can be used as an esterification catalyst for the polycondensation reaction. The amount of the esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.2 parts by mass or more, relative to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component, and is preferably 1.5 parts by mass or less, more preferably 1.0 part by mass or less, and even more preferably 0.6 parts by mass or less. In addition to the esterification catalyst, a pyrogallol compound such as gallic acid can be used as a promoter in the polycondensation reaction from the viewpoint of reaction rate. The amount of the promoter used is preferably 0.001 part by mass or more, more preferably 0.005 part by mass or more, even more preferably 0.01 part by mass or more, and preferably 0.15 part by mass or less, more preferably 0.10 part by mass or less, even more preferably 0.08 part by mass or less, relative to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. In addition to the catalyst, a polymerization inhibitor such as 4-tert-butylcatechol can be used in the polycondensation reaction. The amount of the polymerization inhibitor used is preferably 0.001 part by mass or more, more preferably 0.01 part by mass or more, and preferably 0.10 part by mass or less, more preferably 0.05 part by mass or less, per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

[0031] (Polyester content in asphalt modifier) The content of the polyester in the asphalt modifier is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 85% by mass or more, based on the total mass of the asphalt modifier.

[0032] 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.

[0033] [Asphalt composition] The asphalt composition of the present invention contains asphalt and the polyester that constitutes the asphalt modifier.

[0034] <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.

[0035] (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.

[0036] 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, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and preferably 30% by mass or less, more preferably 15% by mass or less, even more preferably 5% by mass or less.

[0037] From the viewpoint of the durability of asphalt pavement, the asphaltene content in the asphalt is preferably 13% by mass or more, more preferably 15% by mass or more, even more preferably 17% by mass or more, and preferably 35% by mass or less, more preferably 27% by mass or less, even more preferably 24% by mass or less. The asphaltene content in asphalt is a value measured in accordance with Japan Petroleum Institute standard JPI-5S-22-83 "Asphaltene Composition Analysis Method by Column Chromatography."

[0038] The total content of straight asphalt and polymer-modified asphalt in the asphalt composition is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more, from the viewpoint of exhibiting asphalt performance, and is preferably 99.5% by mass or less, more preferably 99% by mass or less, and even more preferably 98% by mass or less, from the viewpoint of storage stability.

[0039] <Polyester content> From the viewpoint of durability and storage stability of the asphalt pavement, the content of polyester in the asphalt composition is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, even more preferably 4 parts by mass or more, per 100 parts by mass of asphalt, and is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, even more preferably 10 parts by mass or less, even more preferably 8 parts by mass or less.

[0040] <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 the polyester.

[0041] [Method for producing asphalt composition] The asphalt composition of the present invention can be produced by mixing asphalt with the polyester. Specifically, the asphalt is heated and melted, the polyester is added, and the mixture is stirred and mixed in a commonly used mixer until the polyester is uniformly dispersed in the asphalt, thereby obtaining the 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.

[0042] From the viewpoint of uniformly dispersing the polyester in the asphalt, the mixing temperature of the asphalt and the polyester is preferably 140°C or higher, more preferably 150°C or higher, even more preferably 160°C or higher, and is preferably 230°C or lower, more preferably 210°C or lower, even more preferably 200°C or lower. Furthermore, from the viewpoint of uniformly dispersing the polyester in the asphalt, the mixing time between the asphalt and the polyester is preferably 15 minutes or more, more preferably 30 minutes or more, and even more preferably 1 hour or more, and is preferably 10 hours or less, more preferably 5 hours or less, and even more preferably 3 hours 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.

[0043] [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 asphalt composition. That is, the asphalt mixture contains at least aggregate, asphalt, and the polyester.

[0044] <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 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, more preferably 90% by mass or more, more preferably 92% by mass or more, and preferably 98% by mass or less, more preferably 97% by mass or less, and even more preferably 96% by mass or less.

[0045] <Additives> In addition to the aggregate, asphalt, and polyester described above, various additives conventionally used in asphalt mixtures, such as film-forming agents, thickening stabilizers, and emulsifiers, may 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.

[0046] [Asphalt mixture manufacturing method] 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.

[0047] From the viewpoint of the durability of the asphalt pavement, the temperature of the heated aggregate is preferably 130°C or higher, more preferably 150°C or higher, and even more preferably 170°C or higher, and 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.

[0048] The mixing temperature of the aggregate and asphalt composition is preferably 130°C or higher, more preferably 150°C or higher, and even more preferably 170°C or higher, from the viewpoint of durability of the asphalt pavement, and is 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 degradation of the asphalt. The mixing time for the aggregate and the asphalt composition is not particularly limited, but is preferably 30 seconds or more, more preferably 1 minute or more, and even more preferably 2 minutes or more, and is preferably 2 hours or less, more preferably 1 hour or less, and even more preferably 30 minutes or less.

[0049] 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.

[0050] [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 the steps of applying the asphalt mixture to a road to form an asphalt pavement layer. Specifically, the road paving method includes the steps of mixing the asphalt composition with heated aggregate to obtain an asphalt mixture (Step 1), and applying the asphalt mixture obtained in Step 1 to a road to form an asphalt pavement layer (Step 2). The asphalt pavement layer is preferably a base layer or a surface layer.

[0051] The asphalt mixture may be compacted and applied in the same manner using known construction machinery. From the viewpoint of the durability of the asphalt pavement, the compaction temperature when used as a heated asphalt mixture is preferably 100°C or higher, more preferably 120°C or higher, and even more preferably 130°C or higher, and is preferably 200°C or lower, more preferably 180°C or lower. [Example]

[0052] In the following Production Examples, Examples and Comparative Examples, "parts" and "%" are "parts by mass" and "% by mass" unless otherwise specified.

[0053] The physical properties of the polyester were measured and evaluated by the following methods. (1) Acid value of polyester The acid value of the polyester 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)).

[0054] (2) Hydroxyl value of polyester The hydroxyl value of the polyester was measured according to the method of JIS K0070: 1992, except that the measurement solvent was changed from the mixed solvent of ethanol and ether specified in JIS K0070: 1992 to tetrahydrofuran.

[0055] (3) Number average molecular weight, weight average molecular weight, peak top molecular weight and polydispersity of polyester The molecular weight distribution was measured by gel permeation chromatography (GPC) according to the following method, and the number average molecular weight Mn, weight average molecular weight Mw, peak top molecular weight Mp, and polydispersity Mw / Mn were determined. (i) Preparation of sample solution The sample was dissolved in tetrahydrofuran at 60° C. to a concentration of 0.5 g / 100 mL. Then, at room temperature, this solution was filtered using a PTFE-type membrane filter with a pore size of 0.2 μm (manufactured by Toyo Roshi Kaisha, Ltd., "DISMIC-25JP") to remove insoluble matter, thereby obtaining a sample solution. (ii) Molecular weight measurement The following measuring equipment and analytical column were used, and tetrahydrofuran was used as the eluent at a flow rate of 1 mL per minute. The column was stabilized in a thermostatic bath at 40°C. 100 μL of the sample solution obtained in (i) above was injected into the column and the measurement was carried out. The molecular weight of the sample was calculated based on a calibration curve prepared in advance. The calibration curve used here included several types of monodisperse polystyrene "A-500" (5.0 × 10 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 x 10 3 ), "F-2" (1.81 x 10 4 ), "F-4" (3.97 x 10 4 ), "F-10" (9.64 x 10 4 ), "F-20" (1.90 x 10 5 ), "F-40" (4.27 x 10 5 ), "F-80" (7.06 x 10 5 ), "F-128" (1.09 x 10 6 ) (all manufactured by Tosoh Corporation) were used as standard samples. The numbers in parentheses indicate molecular weights. Measuring device: "HLC-8320GPC" (Tosoh Corporation) Analytical column: "GMHXL" + "G3000HXL" (manufactured by Tosoh Corporation)

[0056] Production Examples 1 to 4 (Production of Polyesters (E-1) to (E-4)) The alcohol component, carboxylic acid component, and polymerization inhibitor shown in Table 1 were placed in a 10-L four-neck flask equipped with a thermometer, stainless steel stirring rod, dehydration tube, nitrogen inlet tube, and thermocouple, and the temperature was raised to 130°C. After that, tin(II) di(2-ethylhexanoate) and gallic acid were added under a nitrogen atmosphere, and the temperature was raised to 140°C. The temperature was then raised to 210°C over 7 hours, and the reaction was continued at 210°C and 8 kPa for 1 hour to obtain polyesters (E-1) to (E-4). The results are shown in Table 1.

[0057] Production Example 5 (Production of Polyester (C-1)) The alcohol component, carboxylic acid component, and polymerization inhibitor shown in Table 1 were placed in a 10-L four-neck flask equipped with a thermometer, stainless steel stirring rod, dehydration tube, nitrogen inlet tube, and thermocouple, and the mixture was heated to 130°C. After that, tin(II) di(2-ethylhexanoate) and gallic acid were added under a nitrogen atmosphere, and the mixture was heated to 170°C. The mixture was then heated to 190°C over 3 hours, reacted at 190°C for 2 hours, and then reacted at 190°C for 3 hours at 8 kPa to obtain polyester (C-1). The results are shown in Table 1.

[0058] Production Example 6 (Production of Polyester (C-2)) The alcohol and carboxylic acid components shown in Table 1 were placed in a 10-L four-neck flask equipped with a thermometer, stainless steel stirring rod, dehydration tube, nitrogen inlet tube, and thermocouple, and the mixture was heated to 130°C. After that, tin(II) di(2-ethylhexanoate) and gallic acid were added under a nitrogen atmosphere, and the mixture was heated to 180°C. The mixture was then heated to 210°C over 3 hours and reacted at 210°C for 3 hours, followed by another 1.5 hours at 210°C under 8 kPa to obtain polyester (C-2). The results are shown in Table 1.

[0059] Production Example 7 (Production of Polyester (C-3)) The alcohol component, carboxylic acid component, and polymerization inhibitor shown in Table 1 were placed in a 10-L four-neck flask equipped with a thermometer, stainless steel stirring rod, dehydration tube, nitrogen inlet tube, and thermocouple, and the temperature was raised to 130°C. After that, tin(II) di(2-ethylhexanoate) and gallic acid were added under a nitrogen atmosphere, and the temperature was raised to 140°C. The temperature was then raised to 210°C over 7 hours, and the reaction was continued at 210°C and 8 kPa for 1 hour to obtain polyester (C-3). The results are shown in Table 1.

[0060] [Table 1]

[0061] Example 1 (Asphalt Composition) 200 g of straight asphalt (Associated Asphalt, Performance Grade (PG) 64-22, asphaltene content in asphalt: 20.9% by mass) that had been preheated to 180°C was weighed into a 300 mL stainless steel beaker, and 10 g (5 parts by mass per 100 parts by mass of asphalt) of the polyester (E-1) obtained in Production Example 1 was added thereto. The mixture was stirred at 180°C and a stirring speed of 400 rpm for 2 hours to prepare asphalt composition (AS-1).

[0062] Examples 2 to 4, Comparative Examples 1 to 3 Asphalt compositions AS-2 to AS-4 and AS-C1 to AS-C3 were prepared in the same manner as in Example 1, except that the blending ratios were changed as shown in Table 2.

[0063] Comparative Example 4 An asphalt composition AS-C4 was prepared in the same manner as in Comparative Example 1, except that 0.25 g of a dispersant (manufactured by Lubrizol Corporation, "Solplus K240") was added as an additive together with the polyester (C-1).

[0064] [evaluation] [Storage stability test (cigar tube test)] The tendency of polyester separation in the asphalt composition was evaluated according to ASTM D7173. Specifically, 50 g of the obtained asphalt composition was poured into a vertically standing 25 mm diameter aluminum tube ("Aluminum Tube" manufactured by GENEQ Inc.). The aluminum tube into which the asphalt composition had been poured was sealed and left standing vertically at 163°C for 48 hours. The aluminum tube was then kept standing vertically and allowed to solidify at -10°C for 4 hours. The solidified sample was cut into three equal parts together with the aluminum tube using an electric cutter, and the central part was discarded. The upper and lower samples were separately heated to 163°C to liquefy, and their softening points were measured using a softening point tester (PAC LP, Ring and Ball Herzog HRB 754) according to ASTM D36. The smaller the difference between the softening points of the lower and upper samples, the better the storage stability of the asphalt composition. The results are shown in Table 2.

[0065] [Table 2]

[0066] Comparing the Examples and Comparative Examples above, it can be seen that the asphalt compositions using the specific polyesters of the Examples exhibit superior storage stability at high temperatures compared to the asphalt compositions of the Comparative Examples. By using the asphalt composition of the present invention in asphalt pavement, it is expected that a pavement with uniform strength can be obtained even after long-term storage at high temperatures.

Claims

1. An asphalt modifier comprising a polyester containing structural units derived from an alcohol component, the structural units containing 50 mol % to 99 mol % of an aliphatic diol (A) having from 4 to 12 carbon atoms and 1 mol % to 50 mol % of an alkylene oxide adduct of bisphenol A (B), and structural units derived from a carboxylic acid component.

2. 2. The asphalt modifier according to claim 1, wherein the polyester has a number average molecular weight of 1,500 or more and 8,000 or less.

3. The asphalt modifier according to claim 1 or 2, wherein the alcohol component contains 0.1 mol% to 20 mol% of an aliphatic monoalcohol (C) having 12 to 22 carbon atoms, relative to a total of 100 mol% of the alcohol component.

4. 3. The asphalt modifier according to claim 1 or 2, wherein the carboxylic acid component contains 0.1 mol% to 20 mol% of an aliphatic monocarboxylic acid (D) having 12 to 22 carbon atoms, relative to a total of 100 mol% of the carboxylic acid component.

5. The asphalt modifier according to claim 4, wherein the aliphatic monocarboxylic acid (D) has 16 or more and 20 or less carbon atoms.

6. 3. The asphalt modifier according to claim 1, wherein the polydispersity index Mw / Mn of the polyester is 2.9 or more and 8.0 or less.

7. 3. The asphalt modifier according to claim 1, wherein the molar ratio [(A) / (B)] of the aliphatic diol (A) to the alkylene oxide adduct of bisphenol A (B) is 1.2 or more and 9 or less.

8. An asphalt composition comprising asphalt and the asphalt modifier according to claim 1 or 2.

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