Process for the preparation of an asphalt composition

Abstract: Preparation of an asphalt composition using an asphalt modifier composition comprising at least one member selected from the group consisting of rubber-base modifiers and resin-base modifiers and a phosphorus compound permits the modifier to be satisfactorily dissolved in asphalt. Further, when paving is conducted by using a composition for paving prepared with such the asphalt composition, the adhesion of asphalt to an aggregate is high, and the resultant pavement has markedly improved in rutting resistance and wearing resistance. Therefore, such the pavement has a prolonged service life.

Description: The present invention relates to a process of preparing an asphalt composition comprising a rubber-base modifier and/or a resin-base modifier, and a phosphorus compound. More particularly, the asphalt modifier composition has an excellent solubility of the rubber-base modifier and/or the resin-base modifier contained therein as the main component(s) in asphalt when mixed with asphalt. The asphalt composition is excellent in adhesion to an aggregate, and, when used for executing a pavement, can markedly reduce the formation of rutting and wearing of the pavement and can prolong the service life of the pavement. An asphalt composition for paving comprises asphalt and, in addition, various additives for improving the properties such as weather resistance and temperature dependence of the asphalt. Such an asphalt composition is used for paving in places where conventional petroleum asphalt, when used alone, has no satisfactory function or places where the long-term service life and durability of the pavement are required. Examples of such additives include rubber-base modifiers, such as natural rubber, styrene-butadiene rubber and chloroprene rubber, and resin-base modifiers, such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer and polyesters. They are used alone or as a mixture of two or more of them. Since, however, these modifiers have poor compatibility with asphalt, the following problems arise. (1) In order to prepare a homogeneous asphalt composition, a mixture of an asphalt with the modifier must be agitated with heating at a high temperature for a long period of time. As the result, the problem of denaturations of the modifier and the asphalt arises, and the resultant asphalt composition has such disadvantages that designed dynamic stability and toughness tenacity cannot be provided and that a pavement executed by using the asphalt composition suffers from significant wearing. Further, the asphalt is denatured, which deteriorates the dispersibility of asphaltene (n-pentane insolubles) contained in the asphalt and the homogeneity of the asphalt. Thus, a problem of lowering the adhesion of the asphalt to an aggregate arises as well. (2) The modifier which has been homogeneously dispersed in the asphalt agglomerates during storage under heating, thus causing the modifier to be separated from the asphalt. For example, a styrene-butadiene rubber which is one member of modifiers has a lower specific gravity (about 0.93/15°C) than the asphalt (specific gravity: about 1.04/15°C). Therefore, when the separation of the modifier from the asphalt has occurred during storage of the asphalt composition in a storage tank under heating, the modifier is unevenly distributed. As the result, in the upper part of the asphalt composition, the modifier (styrene-butadiene rubber) becomes rich, while in the lower part thereof, the modifier becomes poor. Thus, the asphalt composition includes a part not exhibiting designed various properties. When an asphalt composition which is poor in the modifier content is used for paving, the resultant pavement has very poor rutting resistance and wearing resistance. In order to solve the above problem, that is, the problem of the separation of the modifier from the asphalt at high temperatures, Japanese Patent Publication-A No. 6-329919 proposes a process comprising using, together with an asphalt, an ester prepared by reacting a copolymer prepared from an ethylenically unsaturated carboxylic acid and an aromatic vinyl compound with a hydroxyl group-containing compound, or a salt of the ester, and Japanese Patent Publication-A No. 7-157665 discloses the utilization of an asphalt modifier comprising an oil-soluble polymer having both an acid group and a basic group. The adoption of these methods results in somewhat improvement of the properties of the asphalt composition. However, a further improvement in the dispersibility of the modifier, when the asphalt composition is allowed to stand without agitation for a long period of time, has been desired in the art. Further, it is required that the asphalt is less likely to be stripped from the aggregate for improving the properties of a pavement executed by using an asphalt composition. For this reason, in order to improve the adhesion of the asphalt to the aggregate, Japanese Patent Publication-A No. 60-188462 proposes the addition of a specific acid organophosphorus compound to an asphalt, while Japanese Patent Publication-A No. 6-192579 proposes the use of polypropylene or polyethylene modified with maleic anhydride as the modifier. In recent years, there is a fear of the there deterioration in the quality of asphalt, while there is a fear of a good-quality aggregate for paving being exhausted. Therefore, a further improvement in the adhesion of the asphalt to the aggregate has been desired in the art. An object of the present invention is to provided a process of preparing an asphalt composition which has excellent solubility and dispersibility in asphalt, and can improve the properties of the asphalt such as weather resistance and temperature dependence, and which improves the adhesion of the asphalt to an aggregate and, at the same time, improves the rutting resistance and wearing resistance of the pavement which has been executed by using the modifier composition to be able to prolong the service life of the pavement. The present inventors have made extensive studies for improving the above-mentioned problems according to the conventional modifiers. As a result of the studies, they have found that, by using an asphalt modifier composition comprising a specific phosphorus compound and a modifier, the solubility and dispersibility of the modifier in asphalt are improved, the properties of the asphalt such as weather resistance and temperature dependence are improved, the adhesion of the asphalt to the aggregate is improved, and the rutting resistance and wearing resistance of the pavement which has been executed by using the modifier composition are improved. Thus, the present invention relates to a process of preparing an asphalt composition comprising mixing at least one member selected from the group consisting of rubber-base modifiers and resin-base modifiers, with a specified phosphorus compound and then mixing this modifier with asphalt. The asphalt modifier composition is preferably one prepared through the step of mixing at least one member selected from the group consisting of rubber-base modifiers and resin-base modifiers with a phosphorus compound at a temperature of from 50 to 200°C. The phosphorus compound is an acid organophosphorus compound represented by the following formula (1), and the content of the acid organophosphorus compound is 0.1 to 30% by weight based on the total weight of the at least one member selected from the group consisting of rubber-base modifiers and resin-base modifiers, and the acid organophosphorus compound: wherein R represents a saturated or unsaturated aliphatic hydrocarbon group having 8 to 36 carbon atoms or an alkylphenyl group having 6 to 26 carbon atoms in total; m is 1 or 2 and k is 1 or 2, provided that the sum of m and k is 3; and the product of m and n, which represents the average number of ethylene oxide molecules added per molecule, is 0 to 20. The acid organophosphorus compound represented by the above formula (1) includes compounds represented by the following formula (1a): wherein R represents a saturated or unsaturated aliphatic hydrocarbon having 8 to 36 carbon atoms or an alkylphenyl group having 6 to 26 carbon atoms in total; m represents an integer of 1 to 2; n represents an integer of 0 to 10; k represents an integer of 1 to 2; and the sum of m and k is 3. The asphalt composition comprises an asphalt and the above-mentioned asphalt modifier composition, wherein the content of the asphalt modifier composition is 0.1 to 30% by weight based on the weight of the asphalt. The mixing step is preferably a melt-mixing step. Further applicability of the present invention with become apparent from the following detailed description and examples. The asphalt modifier composition comprises a rubber-base modifier and/or a resin-base modifier, and a phosphorus compound. Examples of the rubber-base modifiers include natural rubber (NR), and synthetic rubbers such as styrene-butadiene rubber (SBR), styrene-butadiene-styrene rubber (SBS), styrene-isoprene rubber (SIR) and chloroprene rubber (CR). Among them, block copolymers of aromatic compound monomers each having a vinyl group with conjugate diene compound monomers are thermoplastic rubbers, and are preferred from the viewpoint of the solubility in asphalt. Examples of the aromatic compound monomers each having a vinyl group, which are starting materials for the block copolymers described above, include monomers such as styrene, p-methylstyrene, tert-butylstyrenes, α-methylstyrene and 1,1-diphenylethylene. Among them, styrene is preferred from the viewpoints of cost and reactivity. One member alone among these monomers, or two or more of them is(are) used as the starting material(s) for the above-mentioned block copolymers. While, examples of the conjugate diene compound monomers include monomers such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene and 1-phenyl-1,3-butadiene. Among them, 1,3-butadiene and isoprene are preferred from the viewpoints of cost and reactivity. One member alone among these monomers, or two or more of them is (are) used as the starting material(s) for the above-mentioned block copolymers. Among the above-mentiond block copolymers, styrene-butadiene-styrene rubber (SBS) and styrene-isoprene-styrene rubber (SIS) are preferred, and SBS is most preferred. The thermoplastic block copolymer may be prepared by, for example, a process comprising first polymerizing an aromatic compound monomer having a vinyl group with the use of an organolithium compound or the like as the polymerization initiator in an inert hydrocarbon solvent, then copolymerizing a conjugate diene compound monomer therewith, and thereafter repeatedly subjecting the aromatic compound monomer having a vinyl group and the conjugate diene compound monomer to block copolymerization. The polymerization temperature in such the reaction is not particularly limited. In usual, however, it is preferably in the range of from 20 to 130°C when the productivity is taking into consideration. Still more preferably, the polymerization initiation temperature is in the range of from 30 to 90°C, and the maximum attainable temperature during polymerization and aging is in the range of from 80 to 120°C. Examples of inert hydrocarbon solvents usable in the reaction include cyclohexane, n-hexane, benzene, toluene, xylene and octane, and mixtures of two or more of them. Among them, cyclohexane is preferred. The resin-base modifiers usable in the present invention include polyethylene, polypropylene, polystyrene, polycarbonate, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), ethylene-propylene copolymer, polyurethane, acrylic ester copolymers, styrene-acrylic ester copolymers, polyester resin and petroleum resin and, in addition, thermosetting resins such as phenol-aldehyde copolymers and epoxy resins. Among them, ethylene-vinyl acetate copolymer and ethylene-ethyl acrylate copolymer are preferred because an asphalt composition containing any of such the modifiers has large flow resistance. Further, in the present invention, voluntary mixtures of a rubber-base modifier and a resin-base modifier may be used as the asphalt modifier. Among them, a mixture of SBS and EEA, a mixture of SBS and EVA, a mixture of SIS and EEA, and a mixture of SIS and EVA are preferred, because the asphalt composition containing any of such the mixtures is superior in properties such as adhesion to an aggregate, weather resistance and temperature dependence, and the pavement executed with such the asphalt composition is excellent in rutting resistance and wearing resistance. The organophosphorus compounds are used from the viewpoints of dispersibility in the rubber-base modifier and/or the resin-base modifier, and the homogeneity of the resultant modifier composition. These compounds may be used together with an inorganic phosphorus compound. Examples of the inorganic phosphorus compounds usable in the present invention include phosphoric anhydride (P 2 O 5 ), polyphosphoric acid, orthophosphoric acid, phosphorus oxytrichloride (POCl 3 ), phosphorus trichloride (PCl 3 ) and phosphorus pentasulfide (P 2 S 5 ). The use of phosphoric anhydride, polyphosphoric acid, or orthophosphoric acid is preferred particularly from the viewpoint of handleability. An asphalt composition comprising an asphalt modifier composition containing 0.1 to 10% by weight of the inorganic phosphorus compound has higher adhesion to an aggregate than an asphalt composition not containing any inorganic phosphorus compound. Thus, it is preferable that the asphalt modifier composition further contains the above-mentioned inorganic phosphorus compound in an amount of 0.1% by weight or more from the viewpoint of improving the adhesion of the asphalt composition to the aggregate. While from the viewpoint of the homogeneity of the asphalt modifier composition, it is preferable that the composition contains the inorganic phosphorus compound in an amount of 10% by weight or less. The content of the inorganic phosphorus compound in the asphalt modifier composition is preferably 0.5 to 5% by weight, and still more preferably 1 to 5% by weight. The reason why the asphalt modifier composition containing the inorganic phosphorus compound has excellent adhesion to an aggregate is presumably as follows. It is known that the inorganic phosphorus compound contained in the asphalt modifier composition is used as a catalyst in the production of a blown asphalt and contributes to the formation of a developed network structure (see Japanese Patent Publication-B No. 54-23691). Similarly, the inorganic phosphorus compound functions as a crosslinking agent between the rubber-base modifier and/or the resin-base modifier, and a higher order network structure (asphaltene) in the asphalt, and is useful to strengthen the gel structure in the asphalt. By virtue of this, the asphalt composition containing an inorganic phosphorus compound has high adhesion to an aggregate and good resistance to stripping from the aggregate. However, when the inorganic phosphorus compound and the rubber-base modifier and/or the resin-base modifier are separately melt-mixed with the asphalt, the above effect can not be satisfactorily exhibited because the inorganic phosphorus compound has poor dispersibility in the asphalt. Another embodiment of the asphalt modifier composition is prepared from the modifier described above, and an inorganic phosphorus compound and a compound having a hydroxyl group capable of bonding to the inorganic phosphorus compound. The compound having a hydroxyl group capable of bonding to the inorganic phosphorus compound may be a low-molecular weight compound or a high-molecular weight compound, and is not particularly limited. Examples of the low-molecular weight compounds usable herein include aliphatic alcohols such as 2-ethylhexyl alcohol, decyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol and arachidyl alcohol; alkylphenols such as octylphenol and nonylphenol; synthetic alcohols synthesized by the oxo process, the Ziegler process, the Guerbet process or the like; adducts of the above alcohols and alkylphenols with an alkylene oxide(s), preferably ethylene oxide and/or propylene oxide, wherein the (total) amount of the alkylene oxide(s) is 1 to 10 moles per mole of the alcohol (or alkylphenol); diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol and 1,6-hexanediol; etherified bisphenols such as bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A and polyoxypropylenated bisphenol A; dihydric alcohols other than bisphenols; and trihydric or higher alcohols such as sorbitol, 1,2,3,6-hexane-tetraol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane and 1,3,5-trihydroxybenzene; and mixtures of two or more of the above low-molecular weight compounds. Among them, those having a large number of carbon atoms are preferred from the viewpoints of the solubility and dispersibility in the asphalt modifier, and those having 16 or more carbon atoms are particularly preferred from the viewpoint of the adhesion of the asphalt composition to an aggregate. Examples of high-molecular weight compounds usable herein include polyethylene glycol, polypropylene glycol, polyvinyl alcohol, a polyester polyol prepared by the polycondensation of a dihydric alcohol with a dibasic acid component, cellulose and its derivatives, and epoxy resins, and mixtures of two or more of the above high molecular weight compounds. Among these high-molecular weight compounds, those having a molecular weight of 10000 or less, particularly 5000 or less, are preferred from the viewpoint of the bondability to, i.e., the reactivity with, the inorganic phosphorus compound. The compound having a hydroxyl group capable of bonding to the inorganic phosphorus compound is considered to play the following role. When the asphalt modifier composition contains an inorganic phosphorus compound as the phosphorus compound, the adhesion of an asphalt composition prepared by using such the modifier composition to an aggregate and the resistance thereof to stripping from the aggregate are higher than those in the case of an asphalt composition not containing any phosphorus compound. However, the asphalt is an organic material, and the affinity of an organic compound for the asphalt is higher than that of an inorganic compound for the asphalt. Therefore, when an inorganic phosphorus compound is reacted with a compound having a hydroxyl group capable of bonding to the inorganic phosphorus compound in the preparation process of the asphalt modifier composition, an organophosphorus compound having higher affinity for asphalt can be obtained. Since such the organophosphorus compound has excellent dispersibility in asphalt, the properties inherent in the phosphorus compound can be satisfactorily exhibited in an asphalt composition prepared by using such the asphalt modifier composition. The inorganic phosphorus compound and the compound having a hydroxyl group capable of bonding to the inorganic phosphorus compound are incorporated into the modifier in the system of the asphalt modifier composition, and are given an opportunity for bonding at a high frequency. That is, both the compounds are reacted with each other in the system of the asphalt modifier composition at a high reaction efficiency. During the preparation of the modifier composition, the inorganic phosphorus compound and the compound having a hydroxyl group capable of bonding to the inorganic phosphorus compound are not always completely reacted with each other. Further, under some preparation conditions, the inorganic phosphorus compound and the compound having a hydroxyl group capable of bonding to the inorganic phosphorus compound are present as they are in the modifier composition. Therefore, the modifier composition prepared by using the inorganic phosphorus compound and the compound having a hydroxyl group capable of bonding to the inorganic compound includes the following embodiments: ;(1) a modifier composition comprising a modifier and an organophosphorus compound which is a product of a reaction of an inorganic phosphorus compound with a compound having a hydroxyl group capable of bonding to the inorganic compound; and (2) a modifier composition comprising a modifier, an inorganic phosphorus compound, a compound having a hydroxyl group capable of bonding to the inorganic phosphorus compound, and an organophosphorus compound which is a product of a reaction of the inorganic phosphorus compound with the compound having a hydroxyl group capable of bonding to the inorganic phosphorus compound. The modifier composition comprises an acid organophosphorus compound represented by the following formula (1): wherein R represents a saturated or unsaturated aliphatic hydrocarbon group having 8 to 36 carbon atoms or an alkylphenyl group having 6 to 26 carbon atoms in total; m is 1 or 2 and k is 1 or 2, provided that the sum of m and k is 3; and the product of m and n, which represents the average number of ethylene oxide molecules added per molecule, is 0 to 20, with n being preferably an integer of 0 to 10. The acid organophosphorus compound can be easily prepared on an industrial scale by an usually known method. Further, the above product of a reaction of an inorganic phosphorus compound with a compound having a hydroxyl group capable of bonding to the inorganic phosphorus compound may have, in some cases, a chemical formula represented by the above formula (1). The acid organophosphorus compound represented by the formula (1) is prepared, for example, by the reaction of phosphoric anhydride (P 2 O 5 ), polyphosphoric acid, phosphorus oxytrichloride (POCl 3 ), phosphorus trichloride (PCl 3 ) or phosphorus pentasulfide (P 2 S 5 ) with a hydroxyl compound represented by the formula: RO(C 2 H 4 O) n H. When the acid organophosphorus compound may have a structure represented by the formula: in some cases, and it is needless to say that such the tautomer having the above structure is also included in the scope of the organophosphorus compounds of the present invention. When phosphoric anhydride (P 2 O 5 ) is used as the starting material, the reaction scheme is represented as follows and the reaction product usually becomes a mixture of a monoester and a diester: In the present invention, any of a monoester, a diester and a mixture of a monoester and a diester may be used as the acid organophosphorus compound. However, the use of an acid organophosphorus compound having a content of a monoester of 40% by mole or more is preferred from the viewpoints of the solubility and dispersibility of the asphalt modifier composition containing the acid organophosphorus compound in the asphalt. The content of the monoester of the acid organophosphorus compound is more preferably 60% by mole or more, particularly preferably 60 to 90% by mole, and most preferably about 80% by mole. Examples of the hydroxyl compounds usable as the starting material in the preparation of the compound represented by the above formula (1) include the low-molecular weight compounds and the high-molecular weight compounds described above as examples of the compounds having a hydroxyl group capable of bonding to the inorganic phosphorus compound. Among the low-molecular weight compounds, those having a large number of carbon atoms are preferred from the viewpoints of the solubility and dispersibility in the asphalt, and those having 16 or more carbon atoms are particularly preferred from the viewpoint of the adhesion of the asphalt composition to an aggregate. Among the high-molecular weight compounds, those having a molecular weight of 10000 or less, particularly 5000 or less, are preferred from the viewpoint of the bondability to, i.e., the reactivity with, the inorganic phosphorus compound as the starting material. When the asphalt modifier composition contains the acid organophosphorus compound in an amount of 0.1 to 30% by weight based on 100% by weight in total of the modifier and the above acid organophosphorus compound, such the asphalt modifier composition has excellent solubility and dispersibility in the asphalt and an asphalt composition prepared by using such the modifier composition has excellent adhesion to an aggregate. The asphalt modifier composition contains the above acid organophosphorus compound in an amount of 0.1% by weight or more from the viewpoint of the solubility and dispersibility of the asphalt modifier composition in the asphalt. The content of the acid organophosphorus compound is 30% by weight or less from the viewpoint of homogeneous mixing of the modifier with the acid organophosphorus compound. The content of the acid organophosphorus compound is preferably 0.5 to 20% by weight, particularly preferably 1 to 20% by weight. The reason why the asphalt modifier composition containing the acid organophosphorus compound has excellent solubility and dispersibility in asphalt is presumably as follows. The acid organophosphorus compound contained in the asphalt modifier composition has both a polar group and a nonpolar group in its molecule, and hence serves in the asphalt as a compatibilizer (dispersant for dispersing in oil), i.e., has the effect of homogeneously dispersing the rubber-base modifier and/or the resin-base modifier.in the asphalt. In this case, previous homogeneous mixing of the acid organophosphorus compound with the above modifier offers better effect. Mixing of the acid organophosphorus compound with the above modifier on a molecular level is ideal. However, the above effect can be exhibited even when the acid organophosphorus compound and the modifier are in a state of phase separation. Meanwhile, it is known that the phosphorus compound is used as a catalyst in the production of a blown asphalt and contributes to the formation of a developed network structure. Similarly, the phosphorus compound is considered to function as a crosslinking agent between the rubber-base modifier and/or the resin-base modifier, and a higher order network structure (asphaltene) in the asphalt. However, when the acid organophosphorus compound and the rubber-base modifier and/or the resin-base modifier are separately melt-mixed with the asphalt, the effect of the acid organophosphorus compound as the crosslinking agent is low. The reason why the presence of the acid organophosphorus compound results in an improved adhesion of the asphalt composition to an aggregate is considered in that, since the acid organophosphorus compound has the above structure, it acts on the interface between the asphalt composition and the aggregate. The asphalt modifier composition is prepared by mixing a phosphorus compound with the above modifier. Mixing methods are not particularly limited, but any method is usable. For example, the modifier composition can be prepared by mixing the above phosphorus compound with the above modifier by means of a heat-melting oven, a roll kneader, a Banbury mixer, a kneader-extruder or the like. Alternatively, the modifier composition can be prepared by adding the phosphorus compound in a heat-melted state or as a solution thereof in a solvent before and/or after the preparation of the above modifier thereto, that is, to the starting material composition for the modifier and/or the modifier, followed by mixing therewith. Among the mixing methods described above, a method comprising adding an acid organophosphorus compound to a commercially available or prepared modifier in a heat-melted state and mixing therewith, and a method comprising adding, after the preparation of a modifier, an inorganic phosphorus compound and a compound having a hydroxyl group capable of bonding to the inorganic phosphorus compound, which are starting materials for an acid organophosphorus compound, to the modifier, and preparing the acid organophosphorus compound and, at the same time, mixing the modifier with the phosphorus compound, are preferred from the viewpoint of homogeneous mixing and productivity. The mixing is preferably conducted at a temperature of 50 to 200°C. When the mixing is conducted at a temperature within the above range, a homogeneous mixture of the modifier and the phosphorus compound can be obtained. The asphalt composition comprises an asphalt and the modifier composition of , and the content of the asphalt modifier composition is 0.1 to 30% by weight based on the weight of the asphalt. When the asphalt modifier composition is used in an amount within the above range, the resultant asphalt composition has excellent properties such as weather resistance and temperature dependence, and excellent adhesion to an aggregate, and a pavement executed by using the asphalt composition exhibits excellent rutting resistance and wearing resistance. Hence, the pavement has a prolonged service life. In order to attain the above various effects, the asphalt modifier composition is used in an amount of 0.1% by weight or more based on the weight of the asphalt, while it is used in an amount of 30% by weight or less from the viewpoint of the compatibility thereof with the asphalt. The asphalt modifier composition is used in an amount of preferably 0.5 to 20% by weight, still more preferably 1 to 10% by weight. The asphalt to be used in the present invention is a mixture composed mainly of hydrocarbons, called "bituminous material", and specific examples thereof include petroleum asphalts such as straight asphalt, semi-blown asphalt, blown asphalt and cutback asphalt; and natural asphalt. In the present invention, one member among them may be used, or two or more of them may be used. Further, deteriorated asphalt (in general, asphalt having a low penetration due to the migration of the maltene fraction in the asphalt to asphaltene) recovered from waste pavement and the like are also usable. Furthermore, an asphalt composition comprising an asphalt regenerating additive for restoring the lowered penetration of the asphalt to the penetration equivalent to that of fresh asphalt [specified in "Puranto Saisei Hosou Gijutsu Shishin" (published by Japan Road Association)] is also usable. As the asphalt regenerating additive, the modifier composition of the present invention can also be used. The asphalt composition of the present invention is prepared by mixing the asphalt modifier composition of the present invention with an asphalt. The method for mixing the asphalt modifier composition with the asphalt is not particularly restricted, and any method can be applied. Specifically, an asphalt composition can be prepared by, if desired, mixing, preferably melt-mixing, the asphalt modifier composition described above with the asphalt by means of, for example, a heat-melting oven, a roll kneader, a Banbury mixer, a kneader-extruder or the like. The asphalt composition thus prepared may optionally contain, if necessary, various additives commonly used for the conventional asphalt compositions, for example, fillers and auxiliary agents such as silica, talc, calcium carbonate, mineral powders, glass fibers and cellulose fibers, reinforcements, mineral aggregates, pigments, softening agents such as process oils, and foaming agents such as azodicarbonamides. When the use of the asphalt composition as the material for road paving is contemplated, the asphalt composition is usually used in the form of a mixture thereof with an aggregate such as mineral stone, sand, slag cement and hydrated lime. If necessary, such the mixture (i.e., composition for paving) may further contain an amine-, amide-, or phosphate-base antistripping agent or the like for the purpose of preventing the stripping of the asphalt composition from the aggregate. The asphalt composition prepared by using the asphalt modifier composition of the present invention has excellent adhesion to an aggregate and an antistripping property, and can satisfy various properties required in the market. Accordingly, the asphalt composition of the present invention can be utilized as the material for road paving, a roofing material, and an underground protective material for vehicles, which are used in construction for waterproofing. Examples The present invention will now be described in more detail with reference to the following Examples. Example 1 The acid organophosphorus compounds listed in Table 1 and a commercially available styrene-butadiene rubber (SBR) (entire styrene content: 25% by weight, weight-average molecular weight: 350,000) were weighed at the ratios specified in Table 1, followed by mixing. The resultant mixtures were kneaded by means of an 8-inches roll kneader under the conditions of the number of revolutions of 15 rpm, the temperature of 200°C, and the mixing time of 10 min to prepare asphalt modifier compositions. No. Acid organophosphorus compd. (numerical values within parentheses represent molar ratios) Mixing ratio (by wt.) organophosphorus compd./SBR No. 1 Monostearyl phosphate 2/98 No. 2 Distearyl phosphate 10/90 No. 3 Mixture of monostearyl phosphate and distearyl phosphate (1/1) 5/95 No. 4 Mixture of monostearyl phosphate and distearyl phosphate (3/7) 3/97 No. 5 Mixture of monostearyl phosphate and distearyl phosphate (7/3) 3/97 No. 6 Mixture of monooleyl phosphate and dioleyl phosphate (7/3) 5/95 No. 7 Mixture of monocetyl phosphate and dicetyl phosphate (7/3) 5/95 No. 8 Phosphoric esters of Guerbet's alcohol (no. of carbon atoms: 32) (mono/di = 7/3) 10/90 No. 9 Phosphoric esters of polyoxyethylene (5 mol) nonylphenyl ether (mono/di = 1/1) 10/90 No. 10 Phosphoric esters of ethylene oxide (2 mol) adduct of laurylamine(mono/di = 1/1) 10/90 No. 11 Phosphoric esters of polyoxypropylene (8 mol) butylphenyl ether (mono/di = 1/1) 10/90 Example 2 The acid organophosphorus compounds listed in Table 2 and a commercially available styrene-butadiene-styrene block copolymer (SBS) (Solprene 406, manufactured by Asahi Chemical Industries Co., Ltd.) were weighed at the ratios specified in Table 2, followed by mixing. The resultant mixtures were agitated and mixed at 50°C in the presence of a solvent (a xylene/tetrahydrofuran (7/3) mixed solvent). After mixing, the temperature of the mixtures was raised to remove the solvent by distillation. Thus, asphalt modifier compositions were prepared. Example 3 Air in a 5-liter stainless steel reactor equipped with an agitator was thoroughly purged with nitrogen. Thereafter, 2000 g of cyclohexane, 5 g of tetrahydrofuran, and 80 g of styrene were fed into the reactor, and the temperature was brought to 65°C. Subsequently, a solution of n-butyllithium in cyclohexane [net weight (amount of n-butyllithium): 0.3 g] was fed into the reactor to initiate polymerization of styrene. After styrene was substantially completely polymerized, 240 g of butadiene was added to the reaction mixture and the polymerization was continued. No. Acid organophosphorus compd. (numerical values within parentheses represent molar ratios) Mixing ratio (by wt.) organophosphorus compd./SBS No. 1 Monostearyl phosphate 1/99 No. 2 Distearyl phosphate 10/90 No. 3 Mixture of monostearyl phosphate and distearyl phosphate (1/1) 5/95 No. 4 Mixture of monostearyl phosphate and distearyl phosphate (3/7) 3/97 No. 5 Mixture of monostearyl phosphate and distearyl phosphate (7/3) 3/97 No. 6 Mixture of monooleyl phosphate and dioleyl phosphate (7/3) 5/95 No. 7 Mixture of monocetyl phosphate and dicetyl phosphate (7/3) 5/95 No. 8 Phosphoric esters of Guerbet's alcohol (no. of carbon atoms: 32) (mono/di = 7/3) 5/95 No. 9 Phosphoric esters of polyoxyethylene (5 mol) nonylphenyl ether (mono/di = 1/1) 5/95 No. 10 Phosphoric esters of ethylene oxide (2 mol) adduct of laurylamine(mono/di = 1/1) 5/95 No. 11 Phosphoric esters of polyoxypropylene (8 mol) butylphenyl ether (mono/di = 1/1) 5/95 The reaction temperature at this time was 90°C. After the reaction of butadiene was completed, the reaction mixture thus obtained was aged, i.e., held, at 90°C for about 15 minutes. Thereafter, styrene in the same amount as that previously used was added to the resultant reaction mixture, and the polymerization was continued. After styrene was substantially completely polymerized, 1 g of water was added to the reaction mixture. The water was homogeneously dispersed in the system to completely deactivate the polymerization active species. Subsequently, 8.16 g of each of the acidic organophosphorus compounds specified in Table 3 (styrene-butadiene-styrene block copolymer : acid organophosphorus compound = 98% by weight : 2% by weight) was added to the reaction mixture thus obtained, and the resultant mixture was agitated. At this time, the temperature was 90°C. Each resultant mixture (polymer solution) was withdrawn from the reactor and subjected to steam topping to remove the solvent. Continuously, the obtained mixture was dried (temperature: 150°C) by dehydration by means of an extruder kneader. Thus, mixtures of a styrene-butadiene-styrene block copolymer with acid organophosphorus compounds were prepared. As the result of analysis, it has been found that the entire styrene content of the styrene-butadiene-styrene block copolymer was 38%. The entire styrene content was calculated from the absorption intensity at 262 nm determined with ultraviolet spectrophotometer (UV 200, manufactured by Hitachi Co., Lid.). The acid organophosphorus compounds were each homogeneously dispersed in the block copolymer. P (phosphorus) in each of the mixtures was quantitatively analyzed with inductively coupled plasma (ICP) emission spectrometer (SPS 1100H, manufactured by Seiko Electronic Industries Ltd.). As the result, it has found that the contents of the acid organophosphorus compounds were each in the range of from 2.0 to 2.2 % by weight. The reason why the contents of the acid organophosphorus compounds became high, as compared with those at feed, is in that the yield of the copolymer was not 100%. No. 1 Monostearyl phosphate No. 2 Distearyl phosphate No. 3 Mixture of monostearyl phosphate and distearyl phosphate (1/1) No. 4 Mixture of monostearyl phosphate and distearyl phosphate (3/7)* No. 5 Mixture of monostearyl phosphate and distearyl phosphate (7/3)* No. 6 Mixture of monostearyl phosphate and distearyl phosphate (8/2)* No. 7 Mixture of monooleyl phosphate and dioleyl phosphate (7/3)* No. 8 Mixture of monooleyl phosphate and dioleyl phosphate (8/2)* No. 9 Mixture of monocetyl phosphate and dicetyl phosphate (7/3)* No. 10 Mixture of monocetyl phosphate and dicetyl phosphate (8/2)* No. 11 Phosphoric esters of Guerbet's alcohol (number of carbon atoms: 32) (mono/di = 7/3)* No. 12 Phosphoric esters of Guerbet's alcohol (number of carbon atoms: 32) (mono/di = 8/2)* No. 13 Phosphoric esters of polyoxyethylene (5 mol) nonylphenyl ether (mono/di = 1/1)* No. 14 Phosphoric esters of ethylene oxide (2 mol) adduct of laurylamine (mono/di = 1/1)* No. 15 Phosphoric esters of polyoxypropylene (8 mol) butylphenyl ether (mono/di = 1/1)* Example 4 The acid organophosphorus compounds listed in Table 1 and a commercially available ethylene-vinyl acetate copolymer (EVA) (Evaflex 210, manufactured by Du Pont-Mistui Polychemicals Co., Ltd.) were weighed at the ratios specified in Table 1, followed by mixing. The resultant mixtures were kneaded by means of an 8-inches roll kneader under the conditions of the number of revolutions of 15 rpm, the temperature of 150°C, and the mixing time of 10 min to prepare asphalt modifier compositions. Example 5 and Comparative Examples 1 to 20 50 g of each of the asphalt modifier compositions prepared in Examples 1 to 4 was melt-mixed with 1000 g of straight asphalt (penetration 60/80) in a 2-liter hot-melting oven for 90 minutes at 180°C. Thus, the asphalt compositions of the present invention were prepared. For comparison, the copolymer alone used in any of Examples 1 to 4 (i.e., not adding any acid organophosphorus compound) was used instead of the asphalt modifier composition of the present invention. Thus, asphalt compositions (Comparative Examples 1, 6, 11, and 16) were prepared. Further, for comparison, the copolymer alone used in any of Examples 1 to 4 was melt-kneaded with the asphalt for 90 minutes at 180°C, and then the acid organophosphorus compound was added to the resultant mixture, followed by mixing. Thus, asphalt compositions (Comparative Examples 2, 4, 7, 9, 12, 14, 17, and 19) were prepared. While, asphalt compositions (Comparative Example 3, 5, 8, 10, 13, 15, 18, and 20) were prepared in the same manner as that described above, except that the order of addition of the copolymer and the acid organophosphorus compound was reversed. These asphalt compositions were evaluated by the following methods. <Evaluation Methods> (Compatibility, Dispersibility, and Solubility) For evaluating the compatibility of asphalt with the asphalt modifier compositions prepared in Examples 1 to 4 and the dispersibility and solubility of the modifier compositions in asphalt, the asphalt compositions of the present invention and the comparative asphalt compositions, as prepared above, were stored at a high temperature. Specifically, 1000 g of the sample (asphalt composition) was placed in a cylindrical container having an inner diameter of 80 mm and allowed to stand at 180°C for 5 hours in an open system. Thereafter, a part of the uppermost portion in the asphalt composition was placed on a slide glass, cooled, and then observed under an optical microscope to measure the domain diameter of the modifier (copolymer) in the asphalt. Usually, an asphalt modifier has a lower specific gravity than asphalt. When therefore the compatibility of the asphalt modifier with the asphalt or the dispersibility and solubility of the asphalt modifier in the asphalt is poor, the asphalt composition causes phase separation during standing, resulting in agglomeration of the asphalt modifier on the upper part of the asphalt composition, whereby the domain diameter of the modifier is increased. Thus the compatibility of the asphalt modifier with the asphalt or the dispersibility and solubility of the asphalt modifier in the asphalt can be evaluated by observing the asphalt composition after standing. In this case, when even one modifier domain having a diameter of 100 µm or more was observed, the asphalt modifier composition was evaluated as X; when even one modifier domain having a diameter of 50 to 100 µm was observed, the asphalt modifier composition was evaluated as Δ; and when the diameters of all the modifier domains do not exceed 50 µm, the asphalt modifier composition was evaluated as O. (Toughness and tenacity tests) Toughness and tenacity values most directly represent the properties of asphalt compositions containing a rubber and/or a resin. More specifically, the toughness represents the force of the asphalt grasping an aggregate (i.e., resistance to pull-out, cohesive force) at ordinary temperatures, while the tenacity represents the force resistant to externally applied large deformation pressure (i.e., caking property). The test sample was prepared by allowing 1000 g of the asphalt composition to stand in a cylindrical container having an inner diameter of 80 mm at 180°C for 5 hours in an open system, removing 800 g of the composition from the upper part of the composition, and taking the same from the residue (200 g) of the composition. The test was conducted according to the method described in JEAAS (Japanese Emulsified Asphalt Association Standard). An asphalt composition containing a modifier having poor compatibility, dispersibility and solubility causes phase separation during standing, and the modifier is unevenly distributed and agglomerates on the upper part of the asphalt composition. As a result, the asphalt composition present in the lower part after standing is poor in the modifier content. Such an asphalt composition has low toughness and tenacity. Evaluation results are given in Tables 4 to 7. Modifiers and modifier compns. used, and prepn. methods for asphalt compns. Compatibility, dispersibility, and solubility Toughness (25°C) kgf·cm Tenacity (25°C) kgf·cm Ex. Ex. 1 - No. 1 O 184 136 Ex. 1 - No. 2 O 163 121 Ex. 1 - No. 3 O 187 140 Ex. 1 - No. 4 O 189 139 Ex. 1 - No. 5 O 191 137 Ex. 1 - No. 6 O 185 139 Ex. 1 - No. 7 O 187 140 Ex. 1 - No. 8 O 169 120 Ex. 1 - No. 9 O 166 123 Ex. 1 - No. 10 O 165 122 Ex. 1 - No. 11 O 168 116 Comp. Ex. 1 SBR alone used in Ex. 1 X 97 43 Comp. Ex. 2 SBR alone used in Ex. 1 was mixed with asphalt, followed by adding organophosphorus compd. No. 1 to the resultant mixture and mixing therewith. Δ 142 109 Comp. Ex. 3 Organophosphorus compd. and SBR were used in the reverse order of Comp. Ex. 2. Δ 151 110 Comp. Ex. 4 SBR alone used in Ex. 1 was mixed with asphalt, followed by adding organophosphorus compd. No. 2 to the resultant mixture and mixing therewith. Δ 117 74 Comp. Ex. 5 Organophosphorus compd. and SBR were used in the reverse order of Comp. Ex. 4. Δ 121 75 Modifiers and modifier compns. Used, and prepn. methods for asphalt compns. Compatibility, dispersibility, and solubility Toughness (25°C) kgf·cm Tenacity (25°C) kgf·cm Ex. Ex. 2 - No. 1 O 263 209 Ex. 2 - No. 2 O 190 149 Ex. 2 - No. 3 O 236 185 Ex. 2 - No. 4 O 240 190 Ex. 2 - No. 5 O 241 191 Ex. 2 - No. 6 O 238 185 Ex. 2 - No. 7 O 245 200 Ex. 2 - No. 8 O 244 195 Ex. 2 - No. 9 O 230 190 Ex. 2 - No. 10 O 235 192 Ex. 2 - No. 11 O 228 185 Comp. Ex. 6 SBS alone used in Ex. 2 X 105 70 Comp. Ex. 7 SBS alone used in Ex. 2 was mixed with asphalt, followed by adding organophosphorus compd. No. 1 to the resultant mixture and mixing therewith. Δ 158 116 Comp. Ex. 8 Organophosphorus compd. and SBS were used in the reverse order of Comp. Ex. 7. Δ 150 112 Comp. Ex. 9 SBS alone used in Ex. 2 was mixed with asphalt, followed by adding organophosphorus compd. No. 2 to the resultant mixture and mixing therewith. Δ 160 110 Comp. Ex. 10 Organophosphorus compd. and SBS were used in the reverse order of Comp. Ex. 9. Δ 162 115 Modifiers and modifier compns. Used, and prepn. methods for asphalt compns. Compatibility, dispersibility, and solubility Toughness (25°C) kgf·cm Tenacity (25°C) kgf·cm Ex. Ex. 3 - No. 1 O 215 173 Ex. 3 - No. 2 O 220 175 Ex. 3 - No. 3 O 218 178 Ex. 3 - No. 4 O 215 171 Ex. 3 - No. 5 O 216 168 Ex. 3 - No. 6 O 220 168 Ex. 3 - No. 7 O 210 166 Ex. 3 - No. 8 O 215 169 Ex. 3 - No. 9 O 215 175 Ex. 3 - No. 10 O 212 174 Ex. 3 - No. 11 O 210 170 Comp. Ex. 11 Polymer alone used in Ex. 3 X 152 100 Comp. Ex. 12 Polymer alone used in Ex. 3 was mixed with asphalt, followed by adding organophosphorus compd. No. 1 to the resultant mixture and mixing therewith. Δ 170 110 Comp. Ex. 13 Organophosphorus compd. and polymer were used in the reverse order of Comp. Ex. 12. Δ 171 111 Comp. Ex. 14 Polymer alone used in Ex. 3 was mixed with asphalt, followed by adding organophosphorus compd. No. 2 to the resultant mixture and mixing therewith. Δ 165 115 Comp. Ex. 15 Organophosphorus compd. And polymer were used in the reverse order of Comp. Ex. 14. Δ 166 113 Modifiers and modifier compns. used, and prepn. methods for asphalt compns. Compatibility, dispersibility, and solubility Toughness (25°C) kgf·cm Tenacity (25°C) kgf·cm Ex. Ex. 4 - No. 1 O 135 86 Ex. 4 - No. 2 O 100 58 Ex. 4 - No. 3 O 120 70 Ex. 4 - No. 4 O 122 74 Ex. 4 - No. 5 O 127 87 Ex. 4 - No. 6 O 100 64 Ex. 4 - No. 7 O 111 65 Ex. 4 - No. 8 O 118 67 Ex. 4 - No. 9 O 110 68 Ex. 4 - No. 10 O 115 65 Ex. 4 - No. 11 O 116 60 Comp. Ex. 16 EVA alone used in Ex. 4 X 53 10 Comp. Ex. 17 EVA alone used in Ex. 4 was mixed with asphalt, followed by adding organophosphorus compd. No. 1 to the resultant mixture and mixing therewith. Δ 75 21 Comp. Ex. 18 Organophosphorus compd. and polymer were used in the reverse order of Comp. Ex. 17. Δ 75 22 Comp. Ex. 19 EVA alone used in Ex. 4 was mixed with asphalt, followed by adding organophosphorus compd. No. 2 to the resultant mixture and mixing therewith. Δ 60 20 Comp. Ex. 20 Organophosphorus compd. and polymer were used in the reverse order of Comp. Ex. 19. Δ 64 15 <Results> The asphalt compositions of the present invention had excellent compatibility of the modifier with the asphalt and excellent dispersibility and solubility of the modifier in the asphalt, not only immediately after the preparation thereof but also after storage at a high temperature. In contrast, the asphalt compositions not containing any acid organophosphorus compound, i.e., containing the asphalt modifier alone (Comparative Examples 1, 6, 11, and 16) suffered from marked lowering in dispersibility of the modifier in the asphalt after storage at a high temperature. The asphalt compositions which were prepared by separately adding the modifier and the acid organophosphorus compound (Comparative Examples 2, 3, 4, 5, 7, 8, 9, 10, 12, 13, 14, 15, 17, 18, 19, and 20), though each of them contained both the modifier and the acid organophosphorus compound, caused a lowering in dispersibility of the modifier in the asphalt after storage at a high temperature. Further, the asphalt compositions of the present invention had a large force of grasping the aggregate and, at the same time, a large resistance to an externally applied large change (deforming pressure). Example 6 and Comparative Examples 21 to 24 By using the asphalt compositions prepared in Example 5, the following tests were conducted. The asphalt compositions were used immediately after the preparation thereof. (Adhesion to aggregate) Rieder and Weber Test was conducted to confirm the adhesion of the asphalt composition to an aggregate. This testing method is one proposed by British Road Research Institute. More specifically, the test herein was conducted as follows. 43 parts by weight of crushed stones each having a particle diameter of 0.15 to 0.075 mm were mixed with 43 parts by weight of crushed stones each having a particle diameter of 0.3 to 0.15 mm, followed by heating to be at 180°C. 14 parts by weight of the asphalt composition which had been thoroughly melt-mixed at 180°C was added to the crushed stone mixture. The resultant mixture was sufficiently agitated to completely coat the crushed stones with the asphalt composition. 0.5 g of the mixture comprising the crushed stones and the asphalt composition with which the crushed stones had been coated was put into a beaker containing 25 ml of each sodium carbonate solution having a predetermined concentration specified in Table 8, and the resultant mixture was boiled for one minute. Among the solutions which caused even a small amount of the asphalt composition to begin to be stripped from the crushed stones (i.e., the solutions wherein pieces of the asphalt composition stripped from the crushed stones floated), the solution having the lowest concentration was recorded, and the adhesion score of the asphalt composition was determined from the concentration according to the criteria indicated in Table 8. Sodium carbonate concn. (M) 0 1/256 1/128 1/64 1/32 1/16 1/8 1/4 1/2 1 Adhesion score 0 1 2 3 4 5 6 7 8 9 Note: When no stripping has been observed in the case where 1M solution of sodium carbonate was used, the adhesion score is 10. (Water-immersion wheel tracking test) The water-immersion wheel tracking test specified in Hosou Shikenhou Binran (published by Japan Road Association) was conducted to examine the durability of each cured pavement composition containing the asphalt composition and the antistripping property of the asphalt composition. The water-immersion wheel tracking test is a wheel tracking test conducted in such a state that the sample is immersed in water and enables the influence of water on the pavement in actual use to simulate in a laboratory. The pavement composition was prepared by feeding into a pugmill mixer a dense grade mix prepared by mixing crushed stone No. 6 (from Takatsuki), crushed stone No. 7 (from Takatsuki), sand (from Yodogawa), screenings (from Takatsuki), and stone powder (from Shiga Prefecture) together in a weight ratio of 35 : 25 : 20 : 13 : 7, and any of the asphalt compositions used in Example 5 and Comparative Examples 1 to 20 in a weight ratio of dense grade mix to asphalt composition of 95 : 5, and then agitating the resultant mixture for 20 seconds. Both the aggregate (dense grade mix) and the asphalt composition were used after being heated to 180°C. Resultant pavement compositions were each placed in a compaction mold and compacted by means of a roller compactor to prepare test pieces for the wheel tracking test. Actual test conditions were more severe than usual conditions and were as follows. The immersion curing time in water for the test piece was 6 hours; the temperature was 70°C; the water level during the test was such that the half of the test piece was under water; and the contact pressure was 6.4 kgf/cm 2 . Six hours after the initiation of immersion curing in water, the percentage area of the asphalt composition stripped from the aggregate was visually evaluated. When the test piece was broken within six hours after the initiation of immersion curing due to stripping of the asphalt composition from the aggregate, the test was stopped at that point. The evaluation results are given in Table 9. Modifiers and modifier compns. used Adhesion to aggregate (adhesion score) Percentage stripping after water-immersion wheel tracking test (%) Ex. Ex. 1 - No. 1 6 10 Ex. 1 - No. 2 8 5 Ex. 1 - No. 3 10 2 Comp. Ex. 21 SBR alone used in Ex. 1 3 30 Ex. Ex. 2 - No. 4 10 0 Ex. 2 - No. 5 10 0 Ex. 2 - No. 6 9 2 Comp. Ex. 22 SBS alone used in Ex. 2 2 40 Ex. Ex. 3 - No. 9 10 0 Ex. 3 - No. 11 10 0 Ex. 3 - No. 13 10 0 Comp. Ex. 23 Polymer alone used in Ex. 3 2 50 Ex. Ex. 4 - No. 3 10 5 Ex. 4 - No. 4 10 0 Ex. 4 - No. 5 10 0 Comp. Ex. 24 EVA alone used in Ex. 4 1 55 <Results> The Examples wherein the asphalt composition of the present invention were used were excellent in both the adhesion to an aggregate and the antistripping property in the water-immersion wheel tracking test. On the contrary, in the Comparative Examples, these properties were inferior thereto. As described above, the asphalt compositions which were prepared by using the asphalt modifier compositions were excellent in compatibility of the modifier with the asphalt and dispersibility and solubility in the asphalt, and such the excellent properties were the resultant pavement has markedly improved in rutting resistance and wearing resistance. Therefore, such the pavement has a prolonged service life maintained even after storage of the asphalt compositions at a high temperature. Therefore, the asphalt compositions , when stored in an asphalt production plant and an asphalt mixture plant, do not cause any trouble resulting from the separation of the modifier. That is, the asphalt modifier compositions have excellent properties capable of improving the properties of asphalt. When therefore the asphalt composition is used as a paving material, they can provide pavements which are less likely to cause rutting and wearing. Further, since the asphalt compositions have improved adhesion to an aggregate, pavements laid by using the same have a prolonged service life.

Claims: A process for preparing an asphalt composition which comprises mixing at least one member selected from a rubber-base modifier and a resin-base modifier, with 0,1 % to 30 % by weight, based on said member, of an acid organophosphorus compound of the following formula (1) : wherein R represents a saturated or unsaturated aliphatic hydrocarbon group having 8 to 36 carbon atoms or an alkylphenyl group having 6 to 26 carbon atoms in total; m is 1 or 2 and k is 1 or 2, provided that the sum of m and k is 3; and the product of m and n, which represents the average number of ethylene oxide molecules added per molecule, is 0 to 20, to prepare an asphalt modifier and then mixing this modifier with asphalt. Process according to claim 1, wherein the acid organophosphorus compound is applied in admixture with an inorganic phosphorus compound. Process as defined in claim 2, wherein the asphalt composition further comprises a compound having a hydroxyl group capable of bonding to the inorganic phosphorus compound. Process according to any one of the claims 1 to 3, wherein the first mixing step is performed at a temperature from 50°C to 200°C. Process as defined in any one of the claims 1 to 4, wherein the first mixing step is performed by means of a heat-melting oven, a roll kneader, a Banbury mixer or a kneader-extruder at a temperature from 50°C to 200°C. Process as defined in any one of the claims 1 to 5, wherein the content of the monoester of the phosphorus compound is 40 mole % or more, preferably 60 to 90 mole %. Process as defined in any one of the claims 1 to 6, wherein said member is styrene-butadiene-styrene rubber (SBS) or styrene-butadiene-rubber (SBR). Use of the modifier composition as defined in any one of the claims 1 to 7 for manufacturing an asphalt composition.

Inventors: IKENAGA TAKAYUKI, TANAKA SHINGO, IKENAGA, TAKAYUKI, TANAKA, SHINGO
Applicants: KAO CORP, KAO CORPORATION
Application year: 1997
Main classification: C08L95
IPC codes: C08K3, C08K5, C08L95, C08L21