WO2009017262A1

WO2009017262A1 - Foaming asphalt modifier

Info

Publication number: WO2009017262A1
Application number: PCT/KR2007/003615
Authority: WO
Inventors: Seung-Han Cheon; Sunwoo Cheen; Joonbum Pyun; Chang-Yong Lee
Original assignee: Korea Kumho Petrochemical Co., Ltd.
Priority date: 2007-07-27
Filing date: 2007-07-27
Publication date: 2009-02-05

Abstract

The present invention provides a foaming asphalt modifier comprising i) 100 wt part of styrene-butadiene-styrene block copolymer having the weight average molecular weight of said block copolymer is 50,000~300,000 wherein said styrene-butadiene-styrene block copolymer is prepared by mixing 40~70 wt part of branched styrene-butadiene- styrene block copolymer and 30-60 wt part of linear styrene-butadiene-styrene block copolymer; ii) 5 ~30 wt part of tackifying resin; iii) 3-50 wt part of process additive; and in) 0.01-20 wt part of physical or chemical foaming agent, wherein said foaming agent has 50-250 °C as foaming temperature and generates 20-350 ml/g of amount of decomposition gas. The foaming asphalt modifier of the present invention can afford the excellent processibility, fusibility and dispersion property in the asphalt mixtures.

Description

FOAMINGASPHALT MODIFIER

TECHNICAL FIELD

The present invention relates to a foaming asphalt modifier. More particularly, this invention relates to a foaming asphalt modifier having low specific gravity for enhancing the productivity and operation efficiency for preparing asphalt mixtures by shortening the melting time of asphalt modifier as well as shortening the time for preparing asphalt mixtures from foaming asphalt modifier.

BACKGROUND ART

Generally, an asphalt modifier composition has been made of non-foamed composition, which results in the delay of operation time for preparing a uniformly dispersed asphalt mixtures due to the delayed melting time of asphalt modifier.

To solve above problems, a foaming asphalt modifier has been developed, which generates air bubbles consisting of nitrogen, carbon monoxide and/or carbon dioxide by the decomposition or expansion of foaming agents due to the difference of inner and outside pressure of the composition when the temperature of asphalt modifier composition reaches the decomposition temperature of the foaming agents. On the other hand, cells which are made or grown by the expansion or evaporation of foaming agent in the microcapsules can result in the porous pores in the asphalt composition. Ultimately, the foaming asphalt modifier can enhance the processibility, melting property and dispersion property of asphalt modifier, which enables the improvement of melting rate of asphalt modifier as well as properties of modified asphalt binder composition, when it is applied to plant-mix method.

Two kinds of manufacturing methods for asphalt mixtures, such as, a premix method for preparing asphalt paving mixtures by mixing aggregate and premixed modified asphalt containing asphalt and modifier and a plant-mix method for preparing asphalt paving mixtures by mixing aggregate, asphalt and asphalt modifier simultaneously, have been disclosed. Plant-mix method is advantageous since it does not cause any phase separation during storage and decline of mechanical property at high temperature. Asphalt modifier used for said plant-mix method has been required to be dissolved in the asphalt promptly.

To meet with this requirement, in Korean Patent No. 417,294, an asphalt modifier comprising linear and radial type of styrene-butadiene-styrene block copolymer, tackifying resin and process oil has been disclosed.

An asphalt modifier according to plant-mix method requires 2~3 folds amounts of asphalt modifier compared to those of asphalt modifier made by linear type of styrene- butadiene-styrene copolymer used for conventional dense graded asphalt composition. Further, if the amounts of asphalt modifier can be reduced for preparing asphalt mixtures, a commercially competitive product can be manufactured by reducing the cost. In our previous Korean Patent No. 655,635 by the inventors of the present application, an asphalt modifier comprising i) 100 wt part of radial type based styrene- butadiene-styrene mixed block copolymers as base material; ii) 10-60 wt part of tackifying resin; and iii) 5-70 wt part of process oil, wherein said radial type based block copolymers comprises 10-100 wt% of radial type of styrene-butadiene-styrene block copolymer has been disclosed. However, in case that radial type of styrene-butadiene- styrene block copolymer is used in an amount of more than 20 wt part of the base material, it has some handicaps for applying this asphalt modifier to plant-mix method due to the low fusibility, even though other properties of asphalt binder and mixture are enhanced. Further, in case that tackifying resin is used in an amount of more than 20 wt part of base material, it has also some handicaps for applying this asphalt modifier because blocking can occur in the course of pelletizing process and storage, even though the fusibility is enhanced.

Accordingly, the present invention has developed a foaming asphalt modifier for road pavement with enhanced fusibility to be applied to plant-mix method. More specifically, a foaming asphalt modifier having good properties at the small amount has been developed by broadening the amount range of radial type of styrene-butadiene- styrene block copolymer in the base material as well as minimizing the amount of tackifying resin not to cause the blocking in the course of pellet process and storage.

For this purpose, the changed contents of the asphalt modifier and the formation of porous pores in the asphalt modifier have been introduced. Further, the cost of product can be reduced by minimizing the amount of asphalt modifier in the asphalt binder and mixture. Therefore, the foaming asphalt modifier of the present invention can afford the excellent processibility, fusibility and dispersion property in the asphalt composition.

DISCLOSURE OF INVENTION

The object of the present invention is to provide a foaming asphalt modifier comprising i) 100 wt part of radial type based styrene-butadiene-styrene mixed block copolymers as base material wherein the styrene monomer contents of said mixed block copolymers is 15-50 wt% and the weight average molecular weight of said mixed block copolymers is 50,000-300,000; ii) 5-30 wt part of tackifying resin; iii) 3-50 wt part of processing adjuvant; and iv) 0.01-20 wt part of foaming agent, wherein said radial type based styrene-butadiene-styrene mixed block copolymers comprise i) 40-70 wt% of radial type of styrene-butadiene-styrene block copolymer having 2-6 of branches, ii) 30-60 wt% of linear type of styrene-butadiene-styrene block copolymer.

Further, said radial type based styrene-butadiene-styrene mixed block copolymers further comprise less than 15 wt% of multiblock type of styrene-butadiene-styrene copolymer.

Further, said radial type based styrene-butadiene-styrene mixed block copolymers further comprise less than 10 wt% of styrene-butadiene diblock copolymer. On the other hand, said asphalt modifier further comprises 1-20 wt part of resin at least one selected from i) ethylene-α-olefϊn(C2~C20) graft copolymer; ii) styrene- acrylonitrile resin wherein acrylonitrile content is 15-45 wt%; or iii) ethyl ene-vinylacetate resin wherein vinylacetate content is 5-70 wt%.

On the other hand, said foaming agent can be used at least one of physical foaming agent and chemical foaming agent, wherein the foaming temperature is 60-250 ^°C and the amount of generating gas is 20-350 ml/g.

As said foaming agent, physical foaming agent selected from the group consisting of butane, pentane, neo-pentane, hexane, iso-hexane, heptane, iso-heptane, benzene, toluene, methylchloride, trichloroethylene, dichloroethane, trifluorochloromethane and dichlorodifluoromethane can be used.

Further, chemical foaming agent selected from the group consisting of inorganic chemical foaming agent, such as, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, ammonium nitrite, azide, sodium boride and light metal; and organic chemical foaming agent, such as, azo/diazo compound, N-nitroso compound, sulfonylhydrazide, azide, triazine derivative, tri/tetrazol derivative, urea derivative can be used.

Further, said processing adjuvant is at least one selected from mineral process oil, oily resin, oily butadiene rubber, oily polybutene, oily polyisobutylene, functional radical substituted oil or fatty oil. BEST MODE FOR CARRYING OUT THE INVENTION

The present invention can be described in detail as follows.

The present invention relates to a foaming asphalt modifier and a preparation process thereof. More specifically, the foaming asphalt modifier of the present invention has improved the fusibility and dispersion property by introducing porous pores in the asphalt modifier. Further, the foaming asphalt modifier of the present invention can be prepared by following steps i) adding radial type of styrene-butadiene-styrene block copolymer, which shows low fusibility and dispersion property in the asphalt mixture; tackifying resin; processing adjuvant; and physical or chemical foaming agent in the Henschel mixer; ii) melting and blending the mixture in the single or twin screw extruder; and iii) extruding the pellet type of foaming asphalt modifier. Of course, the foaming asphalt modifier of the present invention can be used in asphalt mixtures for drainage pavement.

Further, said radial type based styrene-butadiene-styrene mixed block copolymers further comprise less than 15 wt% of multiblock type of styrene-butadiene-styrene copolymer or less than 10 wt% of styrene-butadiene diblock copolymer.

A foaming asphalt modifier has been developed by broadening the amount range of radial type of styrene-butadiene-styrene block copolymer in the base material as well as minimizing the amount of tackifying resin not to cause the blocking in the course of pelletizing process and storage. Further, the foaming asphalt modifier of the present invention can afford excellent properties at the small amount.

A foaming asphalt modifier comprising i) 100 wt part of radial type based styrene- butadiene-styrene mixed block copolymers as base material; ii) 5-30 wt part of tackifying resin; iii) 3-50 wt part of processing adjuvant; and iv) 0.01-20 wt part of foaming agent is melted and blended in the single or twin screw extruder and the pellet type of foaming asphalt modifier is extruded.

Further, said asphalt modifier further comprises 1—20 wt part of resin at least one selected from i) ethylene-α-olefϊn(C2~C20) graft copolymer; ii) styrene-acrylonitrile resin wherein acrylonitrile content is 15-45 wt%; or iii) ethyl ene-vinylacetate resin wherein vinylacetate content is 5-70 wt%.

Further, said foaming asphalt modifier further comprises the additives, for example, anti-oxidant, heat stabilizer, anti-static agent and/or lubricant.

The radial type of styrene-butadiene-styrene block copolymer of the present invention has 15-50 wt% of styrene content and 50,000-300,000 of weight average molecular weight. Further, linear type of styrene-butadiene-styrene block copolymer or styrene-butadiene diblock copolymer can be added to said radial type of styrene-butadiene- styrene block copolymer to enhance the processibility and property. If the amount of radial type of styrene-butadiene-styrene block copolymer is less than 70 wt part as to 100 wt part of styrene-butadiene-styrene block copolymers, it does not affect any harmful effect to fusibility without formation of pores in modifier.

As tackifying resin used in the present invention, at least one among synthetic petroleum resin, such as, C5 or C9 petroleum resin, phenol resin, cumarone-indene resin and dicyclopentadiene resin; natural petroleum resin, such as, rosin, terpene resin and rosin ester can be used.

As processing adjuvant in the present invention, mineral process oil, oily resin, oily butadiene rubber, oily polybutene, oily polyisobutylene, functional radical substituted oil or fatty oil can be used alone or in combination.

As foaming agent in the present invention, any physical or chemical foaming agent can be used without any restriction. However, the foaming agent having 60-250 ^°C as foaming temperature and generating 20-350 ml/g of amount of decomposition gas can be preferred. The foaming agent can be used alone or in combination.

An accelerator for foaming agent can be used for improving the foaming property. As physical foaming agent using expansion of compressed gas, evaporation of liquid and/or solution of gas, butane, pentane, neo-pentane, hexane, iso-hexane, heptane, iso- heptane, benzene, toluene, methylchloride, trichloroethylene, dichloroethane, trifluorochloromethane, dichlorodifluoromethane can be used.

Further, as inorganic chemical foaming agent generating gas by heat decomposition of foaming agent, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, ammonium nitrite, azide, sodium boride and light metal can be used.

Further, as organic chemical foaming agent, azo/diazo compound, such as, 2-2'- azobis(isobutylonitrile), 2,2'-azobis(2-methylbutylonitrile), 2,2'-azobis(2,3- dimethylbutylonitrile), 2,2 ' -dimethoxy-2,2 ' -azopropane, 2,2 ' -dibutoxy-2,2 ' -azopropane, N,N'-di(tertbutyl)azodicarbonamide; N-nitroso compound, such as, N,N'- dinitrosopentamethylenetetraamine, N,N'-dimethly-N,N'-dinitrosoterephthalamide; sulfonylhydrazide, such as, P-toluenesulfonylhydrazide, benzosulfonylhydrazide, 4,4'- oxybis(benzenesulfonylhydrazide), bis(hydrazosulfonyl)benzene, benzene- 1 ,4'- disulfonylhydrazide, 4,4 ' -diphenylsulfonylhydrazide, diphenylsulfone-3 ,3 - disulfonylhydrazide; azide, such as, terephthalazide, p- methoxycarbonylaminobenzenesulfazide, p-phenylmethylurethanesulfazide, diphenyl-4,4' - disulfazide, 4,4'-bis(sulfazide)diphenyl, 4,4'-bis(sulfazido)diphenyloxide; triazine derivative, such as, 2,4,6-trihydrazino-l,3,5-triazine, 2,4,6-sulfohydrazo-S-triazine; tri/tetrazol derivative, such as, n-hydroxybenzotriazol, 5-amino-4-mercapto-l,2,3-triazol, 5-hydroxytetrazol, ammonium-5-azidetetrazol; urea derivative, such as, ureaoxalate, nitrourea can be used.

The amount of foaming agent can be used 0.01-20 wt part as to 100 wt part of styrene-butadiene-styrene block copolymer as base material. If the amount of foaming agent is less than 0.01 wt part, the improvement of fusibility in the asphalt composition can not be accomplished due to low formation of pores. On the other hand, if the amount of foaming agent is more than 20 wt part, the further improvement of fusibility in the asphalt composition can not be accomplished, since further formation of pores does not occur remarkably compared with the large amount of the foaming agent used.

The melting and blending of foaming asphalt modifier can be made in 100~200^°C . If the temperature of melting and blending is less than 100^°C, the melting of styrene block domain in the styrene-butadiene-styrene block copolymer is not enough, which affects the harmful effect to blending. On the other hand, if the temperature of melting and blending is more than 200 ^°C , the melting viscosity in the extruder is so low that the decomposition gas cannot disperse uniformly, which affects the harmful effect to form a uniformly dispersed porous pores.

The present invention can be explained more concretely by following examples. However, the scope of the present invention shall not be limited by following examples.

EXAMPLES

(Example 1) Preparation of asphalt modifier binder

65 wt part of radial type of styrene-butadiene-styrene block copolymer, 35 wt part of linear type of styrene-butadiene-styrene block copolymer, 20 wt part of hydrocarbonic tackifying resin, 10 wt part of process oil, 0.3 wt part of anti-oxidant, 1 wt part of azo compound foaming agent are added and mixed in the low speed mixer. Then, the mixture is melted and blended at 180^°C in the twin screw extruder. Strand type of asphalt modifier is extruded from the die of twin screw extruder. Finally, the pellet type of asphalt modifier is prepared upon cooling it in cooled water and cutting it as rotatory cutter. The asphalt binder is prepared by mixing 12 wt part of pellet type of asphalt modifier and 88 wt part of asphalt using high shear mixer. Then, the properties of the asphalt binder, such as, viscosity at 60 ^°C, softening point, penetration, rolling thin film oven test (RTOFT), toughness, tenacity, dynamic shear modulus and m- value are measured. The result of test is shown in Table 1.

(Example 2) Preparation of asphalt modifier binder (change of amount of asphalt modifier)

The asphalt binder is prepared by mixing 10 wt part of pellet type of asphalt modifier prepared in Example 1 and 90 wt part of asphalt using high shear mixer. Then, the properties of asphalt composition, such as, viscosity at 60 ^°C , softening point, penetration, rolling thin film oven test, toughness, tenacity, dynamic shear modulus and m-value are measured. The result of test is shown in Table 1.

(Example 3) Preparation of asphalt modifier binder

55 wt part of radial type of styrene-butadiene-styrene block copolymer, 40 wt part of linear type of styrene-butadiene-styrene block copolymer, 5 wt part of styrene-butadiene diblcok copolymer, 20 wt part of hydrocarbonic tackifying resin, 10 wt part of process oil, 0.3 wt part of anti-oxidant, 1 wt part of azo compound foaming agent are added and mixed in the low speed mixer. Then, the mixture is melted and blended at 180°C in the twin screw extruder. Strand type of asphalt modifier is extruded from the die of twin screw extruder. Finally, the pellet type of asphalt modifier is prepared upon cooling it in cooled water and cutting it as rotatory cutter.

The asphalt binder is prepared by mixing 12 wt part of pellet type of asphalt modifier and 88 wt part of asphalt using high shear mixer. Then, the properties of the asphalt binder, such as, viscosity at 60 ^"C, softening point, penetration, rolling thin film oven test (RTOFT), toughness, tenacity, dynamic shear modulus and m-value are measured. The result of test is shown in Table 1.

(Example 4) Preparation of asphalt modifier binder (change of amount of asphalt modifier)

The asphalt binder is prepared by mixing 10 wt part of pellet type of asphalt modifier prepared in Example 3 and 90 wt part of asphalt using high shear mixer. Then, the properties of asphalt composition, such as, viscosity at 60 ^"C , softening point, penetration, rolling thin film oven test, toughness, tenacity, dynamic shear modulus and m-value are measured. The result of test is shown in Table 1.

(Example 5) Preparation of asphalt modifier binder

50 wt part of radial type of styrene-butadiene-styrene block copolymer, 40 wt part of linear type of styrene-butadiene-styrene block copolymer, 5 wt part of styrene- butadiene-styrene multiblock copolymer, 5 wt part of styrene-butadiene diblcok copolymer, 20 wt part of hydrocarbonic tackifying resin, 10 wt part of process oil, 0.3 wt part of antioxidant, 1 wt part of azo compound foaming agent are added and mixed in the low speed mixer. Then, the mixture is melted and blended at 180^°C in the twin screw extruder. Strand type of asphalt modifier is extruded from the die of twin screw extruder. Finally, the pellet type of asphalt modifier is prepared upon cooling it in cooled water and cutting it as rotatory cutter.

The asphalt binder is prepared by mixing 12 wt part of pellet type of asphalt modifier and 88 wt part of asphalt using high shear mixer. Then, the properties of the asphalt binder, such as, viscosity at 60 "C , softening point, penetration, rolling thin film oven test (RTOFT), toughness, tenacity, dynamic shear modulus and m-value are measured. The result of test is shown in Table 1.

(Example 6) Preparation of asphalt modifier binder (change of amount of asphalt modifier)

The asphalt binder is prepared by mixing 10 wt part of pellet type of asphalt modifier prepared in Example 5 and 90 wt part of asphalt using high shear mixer. Then, the properties of asphalt composition, such as, viscosity at 60 ^°C , softening point, penetration, rolling thin film oven test, toughness, tenacity, dynamic shear modulus and m-value are measured. The result of test is shown in Table 1.

Table 1.

(Comparative Example 1) Preparation of asphalt modifier binder (linear type of styrene-butadiene-styrene block copolymer)

100 wt part of linear type of styrene-butadiene-styrene block copolymer, 30 wt part of hydrocarbonic tackifying resin, 10 wt part of process oil, 0.3 wt part of anti-oxidant are used for raw materials of asphalt modifier. Other preparation method is same as described in Example 1. The asphalt binder is prepared by mixing 12 wt part of pellet type of asphalt modifier and 88 wt part of asphalt. Further, the properties of the asphalt binder are measured as the same manner of Example 1. The result of test is shown in Table 2.

(Comparative Example 2) Preparation of asphalt modifier binder (excessive amount of linear type of styrene-butadiene-styrene block copolymer)

80 wt part of linear type of styrene-butadiene-styrene block copolymer, 20 wt part of radial type of styrene-butadiene-styrene block copolymer, 30 wt part of hydrocarbonic tackifying resin, 10 wt part of process oil, 0.3 wt part of anti-oxidant are used for raw materials of asphalt modifier. Other preparation method is same as described in Comparative Example 1. The asphalt binder is prepared by mixing 12 wt part of pellet type of asphalt modifier and 88 wt part of asphalt. Further, the properties of the asphalt binder are measured as the same manner of Comparative Example 1. The result of test is shown in Table 2.

(Comparative Example 3) Preparation of asphalt modifier binder (radial type of styrene-butadiene-styrene block copolymer)

100 wt part of radial type of styrene-butadiene-styrene block copolymer, 20 wt part of hydrocarbonic tackifying resin, 10 wt part of process oil, 0.3 wt part of anti-oxidant are used for raw materials of asphalt modifier. Other preparation method is same as described in Comparative Example 1. The asphalt binder is prepared by mixing 12 wt part of pellet type of asphalt modifier and 88 wt part of asphalt. Further, the properties of the asphalt binder are measured as the same manner of Comparative Example 1. The result of test is shown in Table 2.

(Comparative Example 4) Preparation of asphalt modifier binder (excessive amount of linear type of styrene-butadiene-styrene block copolymer)

90 wt part of linear type of styrene-butadiene-styrene block copolymer, 10 wt part of styrene-butadiene diblock copolymer, 30 wt part of hydrocarbonic tackifying resin, 10 wt part of process oil, 0.3 wt part of anti-oxidant are used for raw materials of asphalt modifier. Other preparation method is same as described in Comparative Example 1. The asphalt binder is prepared by mixing 12 wt part of pellet type of asphalt modifier and 88 wt part of asphalt. Further, the properties of the asphalt binder are measured as the same manner of Comparative Example 1. The result of test is shown in Table 2.

(Comparative Example 5) Preparation of asphalt modifier binder (excessive amount of styrene-butadiene diblock copolymer)

20 wt part of linear type of styrene-butadiene-styrene block copolymer, 40 wt part of styrene-butadiene diblock copolymer, 30 wt part of radial type of styrene-butadiene- styrene block copolymer, 30 wt part of hydrocarbonic tackifying resin, 10 wt part of process oil, 0.3 wt part of anti-oxidant are used for raw materials of asphalt modifier. Other preparation method is same as described in Comparative Example 1. The asphalt binder is prepared by mixing 12 wt part of pellet type of asphalt modifier and 88 wt part of asphalt. Further, the properties of the asphalt binder are measured as the same manner of Comparative Example 1. The result of test is shown in Table 2.

(Comparative Example 6) Preparation of asphalt modifier binder (base material comprising radial type of styrene-butadiene-styrene block copolymer and styrene- butadiene diblock copolymer)

60 wt part of radial type of styrene-butadiene-styrene block copolymer, 40 wt part of styrene-butadiene diblock copolymer, 20 wt part of hydrocarbonic tackifying resin, 10 wt part of process oil, 0.3 wt part of anti-oxidant are used for raw materials of asphalt modifier. Other preparation method is same as described in Comparative Example 1. The asphalt binder is prepared by mixing 12 wt part of pellet type of asphalt modifier and 88 wt part of asphalt. Further, the properties of the asphalt binder are measured as the same manner of Comparative Example 1. The result of test is shown in Table 2.

Table 2.

As shown in Table 1, the asphalt binders prepared in Examples 1~6 can show the excellent fusibility, that is, less than 20 minutes of melting time. Also, other properties of Examples 1-6 can show the excellent values which meet with specification requirement.

In case of Comparative Example 1, only linear type of styrene-butadiene-styrene block copolymer has been used as base material. Therefore, blocking occurs as well as high weight loss after RTFOT. Further, in case of Comparative Example 2, excessive amount of linear type of styrene-butadiene-styrene block copolymer has been added to base material. Therefore, blocking also occurs as well as low physical properties compared to those of Examples.

In case of Comparative Example 3, only radial type of styrene-butadiene-styrene block copolymer has been used as base material. Therefore, it causes the delay of melting time, whereas other properties are acceptable. Further, in case of Comparative Example 4, excessive amount of linear type of styrene-butadiene-styrene block copolymer has been added to base material. Therefore, blocking also occurs as well as low weight loss after RTFOT compared to those of Examples.

In case of Comparative Example 5, excessive amount of styrene-butadiene diblock copolymer has been used as base material. Therefore, blocking occurs. Further, it causes the delay of melting time as well as decline of other properties. Further, in case of Comparative Example 6, base material comprises only radial type of styrene-butadiene- styrene block copolymer and styrene-butadiene diblock copolymer. Therefore, blocking also occurs as well as the delay of melting time.

Therefore, we proved that a foaming asphalt modifier comprising i) 100 wt part of radial type based styrene-butadiene-styrene mixed block copolymers as base material wherein the styrene monomer contents of said mixed block copolymers is 15-50 wt% and the weight average molecular weight of said mixed block copolymers is 50,000-300,000; ii) 5-30 wt part of tackifying resin; iii) 3-50 wt part of processing adjuvant; and iv) 0.01-20 wt part of foaming agent, wherein said radial type based styrene-butadiene-styrene mixed block copolymers comprise i) 40-70 wt% of radial type of styrene-butadiene- styrene block copolymer having 2-6 of branches, ii) 30-60 wt% of linear type of styrene- butadiene-styrene block copolymer shows optimum physical properties of asphalt material.

INDUSTRIAL APPLICABILITY

The industrial applicability of present invention is to provide a foaming asphalt modifier which shows better physical properties by only small amount of asphalt modifier. The foaming asphalt modifier of present invention improves the melting velocity by formation of porous pores in the asphalt modifier. On the other hand, the amount of tackifying resin can be reduced according to the improvement of melting velocity. Further, the blocking can be prevented in the course of pelleting process, package or storage.

Claims

What is claimed is:

1. A foaming asphalt modifier comprising i) 100 wt part of radial type based styrene- butadiene-styrene mixed block copolymers as base material wherein the styrene monomer contents of said mixed block copolymers is 15-50 wt% and the weight average molecular weight of said mixed block copolymers is 50,000-300,000; ii) 5-30 wt part of tackifying resin; iii) 3-50 wt part of processing adjuvant; and iv) 0.01-20 wt part of foaming agent, wherein said radial type based styrene-butadiene-styrene mixed block copolymers comprise i) 40-70 wt% of radial type of styrene-butadiene-styrene block copolymer having 2-6 of branches, ii) 30-60 wt% of linear type of styrene- butadiene-styrene block copolymer.

2. The foaming asphalt modifier according to claim 1, wherein said radial type based styrene-butadiene-styrene mixed block copolymers further comprise less than 15 wt% of multiblock type of styrene-butadiene-styrene copolymer.

3. The foaming asphalt modifier according to claim 1, wherein said radial type based styrene-butadiene-styrene mixed block copolymers further comprise less than 10 wt% of styrene-butadiene diblock copolymer.

4. The foaming asphalt modifier according to any one of claims 1-3, wherein said asphalt modifier further comprises 1-20 wt part of resin at least one selected from i) ethylene-α- olefin(C2~C20) graft copolymer; ii) styrene-acrylonitrile resin wherein acrylonitrile content is 15-45 wt%; or iii) ethylene- vinylacetate resin wherein vinylacetate content is 5-70 wt%.

5. The foaming asphalt modifier according to claim 1, wherein said foaming agent can be used at least one of physical foaming agent and chemical foaming agent, wherein the foaming temperature is 60-250 ^°C and the amount of generating gas is 20-350 ml/g.

6. The foaming asphalt modifier according to claim 5, wherein said foaming agent comprises i) physical foaming agent selected from the group consisting of butane, pentane, neo-pentane, hexane, iso-hexane, heptane, iso-heptane, benzene, toluene, methylchloride, trichloroethylene, dichloroethane, trifluorochloromethane and dichlorodifluoromethane; ii) chemical foaming agent selected from the group consisting of inorganic chemical foaming agent, such as, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, ammonium nitrite, azide, sodium boride and light metal; and organic chemical foaming agent, such as, azo/diazo compound, N-nitroso compound, sulfonylhydrazide, azide, triazine derivative, tri/tetrazol derivative, urea derivative.

7. The foaming asphalt modifier according to claim 1, wherein said processing adjuvant is at least one selected from mineral process oil, oily resin, oily butadiene rubber, oily polybutene, oily polyisobutylene, functional radical substituted oil or fatty oil.