JP2009209194A - Asphalt rubber and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an asphalt rubber which ensures decrease in viscosity reduction during heated storage and is suitable for heated storage, and a method for producing the asphalt rubber. <P>SOLUTION: The asphalt rubber contains a rubber powder comprising a rubber composition having a composition ratio (mass ratio) of (softening rubber)/(hardening rubber) into straight asphalt, wherein the composition ratio of (softening rubber)/(hardening rubber) is preferably in a range from 50/50 to 80/20. The content of the rubber powder comprising the (softening rubber)/(hardening rubber) composition is preferably in a range from 5 to 30 mass%, and the particle diameter of the rubber powder comprising the (softening rubber)/(hardening rubber) composition is preferably in a range from 10 to 5,000 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an asphalt rubber and a method for producing the same, and more particularly to an asphalt rubber suitable for heat storage and a method for producing the same.

  Conventionally, it is known to use rubber obtained by pulverizing waste tires as an elastic pavement material. When this elastic pavement material is applied to a sidewalk, the elasticity of rubber has an effect on shock absorption and safety in the event of a fall. In addition to performance and breathability, it has excellent sound absorption, and is therefore effective in reducing noise generated on the tire and road surface. However, due to the elasticity of rubber, compaction tends to be insufficient, and wear tends to occur, leaving a problem in durability.

  Also known is an asphalt rubber in which rubber powder obtained by pulverizing waste tires is mixed with asphalt. When using asphalt rubber instead of ordinary asphalt, it is said that the film covering the aggregate such as stone and sand is thickened, the durability of the pavement is improved, and cracking is difficult to occur. Such an asphalt rubber is produced by adding a predetermined amount of waste tire rubber powder to heat-melted straight asphalt, stirring and mixing at a predetermined temperature, and then aging the mixture at a predetermined temperature. Usually, rubber powder is used that is obtained by pulverizing waste tires such as buses and trucks (hereinafter referred to as “TB rubber powder”), and stirring, mixing, and aging are performed at 180 ° C. (for example, Patent Document 1).

The feature of such asphalt rubber is that TB rubber powder swells and is reformed into a high-viscosity binder, and thus, it is said that performance similar to that of modified asphalt can be expected. It has been reported that the asphalt rubber thus obtained is excellent in fluid resistance, wear resistance, fatigue resistance, slip resistance, weather resistance and the like.
JP 2006-328139 A (Claims etc.)

  In Japan, asphalt binders are often stored by heating because of the large number of small-lot shipments on site. This applies not only to straight asphalt but also to other modified asphalts. However, this heat storage is known to cause a decrease in viscosity of any conventionally known asphalt rubber binder, which is an unstable function as a paving binder when considering storage of asphalt rubber. It means that there is.

  Accordingly, an object of the present invention is to provide an asphalt rubber suitable for heat storage with reduced viscosity reduction during heat storage and a method for producing the same.

  As a result of intensive studies, the inventors of the present invention have made a rubber powder composed of a softening rubber / curing rubber composition in which the composition ratio (mass ratio) of rubber components in the TB rubber powder conventionally added to asphalt is in a predetermined range. As a result, it was found that the asphalt rubber does not cause a decrease in viscosity even after heat storage, and the present invention has been completed.

  That is, the asphalt rubber of the present invention is characterized by containing rubber powder made of a rubber composition in which the composition ratio (mass ratio) is softening rubber ≧ curing rubber as rubber powder in straight asphalt. is there.

  In the present invention, the composition ratio (mass ratio) is preferably in the range of 50/50 to 80/20. Further, the content of the rubber powder composed of the softening rubber / curing rubber composition is preferably in the range of 5 to 30% by mass, and further, the rubber powder composed of the softening rubber / curing rubber composition The particle size is preferably in the range of 10 to 5000 μm. Furthermore, it is preferable that the softening rubber is natural rubber and the curable rubber is styrene butadiene rubber.

  The asphalt rubber manufacturing method of the present invention includes a melting step of heating and melting the straight asphalt, and a rubber comprising the softening rubber / curing rubber composition while stirring the straight asphalt at a melting temperature or higher after melting. It is characterized by comprising an addition step of adding powder, a stirring step of continuing stirring after the addition, while maintaining the melting temperature or higher, and an aging step of aging in a thermostat after stirring.

  According to the present invention, the above configuration makes it possible to obtain an asphalt rubber with reduced viscosity reduction even in heat storage, and the asphalt rubber suitable for heat storage is manufactured by the manufacturing method of the present invention. It became possible.

Hereinafter, preferred embodiments of the present invention will be described in detail.
It is important that the asphalt rubber of the present invention contains rubber powder made of a rubber composition having a composition ratio (mass ratio) of softening rubber ≧ curing rubber as rubber powder in straight asphalt. Here, the softening type rubber means a rubber which is deteriorated into a soft rubber having a low degree of polymerization due to a molecular degradation, such as natural rubber (NR), isoprene rubber (IR), butyl rubber (IIR), ethylene. Examples include propylene rubber (EPR) and epichlorohydrin rubber (CO). Further, curable rubber refers to a rubber that deteriorates into a phenotypic phenomenon, loses flexibility and elongation, and changes to a hard but brittle rubber. Styrene butadiene rubber (SBR), butadiene rubber (BR), acrylonitrile butadiene Examples thereof include rubber (NBR), chloroprene rubber (CR), and ethylene propylene rubber (EPDM). In the present invention, NR can be suitably used as the softening rubber, and SBR can be suitably used as the curable rubber.

  Examples of straight asphalt used in the present invention include straight asphalt 40/60, 60/80, 80/100, 100/120, and the like. These can be used alone or in combination of two or more. The asphalt may be decolorized asphalt.

  In the present invention, the composition ratio (mass ratio) of the softening rubber / curing rubber is preferably in the range of 50/50 to 80/20. When the composition ratio (mass ratio) of the softening rubber exceeds 80, the rubber powder is decomposed during heat storage, so that the viscosity of the asphalt rubber is reduced. On the other hand, the composition ratio (mass ratio) of the curable rubber is If it exceeds 50, gelation occurs, so the compatibility with asphalt deteriorates.

  The content of the rubber powder comprising the softening rubber / curing rubber composition used in the present invention is preferably in the range of 5 to 30% by mass, more preferably 10 to 20% by mass, based on the total amount of asphalt rubber. . If the content of the rubber powder comprising the softening rubber / curing rubber composition exceeds 30% by mass, the fluidity at high temperature is low and the construction becomes difficult, whereas if it is less than 5% by mass, the fluidity at high temperature. Is large, and the material is low in rubber elasticity.

  The particle size of the rubber powder made of the softening rubber / curing rubber composition used in the present invention is preferably in the range of 10 to 5000 μm. If the particle size of the rubber powder comprising the softening rubber / curing rubber composition exceeds 5000 μm, the rubber powder is difficult to gel and the effects of the present invention cannot be obtained satisfactorily.

  In addition, the softening rubber / curing rubber composition includes compounding agents usually used in the rubber industry, such as reinforcing fillers, softening agents, anti-aging agents, coupling agents, vulcanizing agents, vulcanizing agents, and the like. A sulfur accelerator or the like may be blended within the range of blending amounts usually used as necessary. Note that a small amount of other rubber powder may be contained within a range not impairing the effects of the present invention.

  In addition, the asphalt rubber of the present invention includes, as necessary, other additives such as a color pigment, an ultraviolet absorber, an antioxidant, an adhesion improver, an anti-aging agent, a metal deactivator, a light stabilizer, and a foaming agent. Further, a water removing agent, a diluting solvent, a polymer for adjusting physical properties, a low molecular additive or the like may be blended.

Next, the manufacturing method of the asphalt rubber of this invention is demonstrated.
The asphalt rubber manufacturing method of the present invention includes a melting step in which straight asphalt is heated and melted, and a rubber powder comprising a softening rubber / curing rubber composition is added while stirring the straight asphalt at a melting temperature or higher after melting. It includes an addition step, a stirring step in which stirring is continued while maintaining the melting temperature or higher after the addition, and an aging step in which aging is performed in a thermostat after the stirring.

  In the melting step, the heating and melting temperature of straight asphalt is preferably in the range of 130 ° C to 180 ° C. This is because straight asphalt is not sufficiently melted at a temperature lower than 130 ° C., whereas the melting effect does not change when the temperature exceeds 180 ° C.

  In the addition step, the temperature at which the rubber powder made of the softening rubber / curing rubber composition is added to the heat-melted straight asphalt is preferably 150 ° C to 200 ° C. When the temperature is lower than 150 ° C., the rubber powder made of the softening rubber / curing rubber composition is not sufficiently gelled. On the other hand, when the temperature exceeds 200 ° C., the asphalt is thermally deteriorated. At this time, the addition of the rubber powder composed of the softening rubber / curing rubber composition may be added while stirring the heated straight asphalt or after the addition, but the softening rubber / curing rubber may be added. Considering the promotion of gelation and uniform mixing of the rubber powder made of the composition, it is preferable to add straight asphalt with stirring. At this time, the stirring speed is preferably 50 rpm to 3000 rpm. When the stirring speed is less than 50 rpm, the dispersion of the rubber powder composed of the added softening rubber / curing rubber composition becomes insufficient and a uniform mixture cannot be obtained. On the other hand, the stirring effect does not change even when the speed exceeds 3000 rpm. It is.

  In the stirring step, the stirring time is preferably 10 minutes or more after adding the rubber powder made of the softening rubber / curing rubber composition to the heated and melted straight asphalt. This is because it takes about 10 minutes for the heat-melted straight asphalt and the rubber powder made of the added softening / curing rubber composition to gel and be mixed uniformly. Further, the stirring speed is preferably 50 rpm to 3000 rpm. This is because a uniform asphalt rubber cannot be obtained when the stirring speed is less than 50 rpm, while the stirring effect does not change even when the stirring speed exceeds 3000 rpm. In addition, as for the temperature of the asphalt rubber at this time, 150 to 200 degreeC is preferable. When the temperature is lower than 150 ° C., the rubber powder made of the softening rubber / curing rubber composition is not sufficiently gelled. On the other hand, when the temperature exceeds 200 ° C., the asphalt is thermally deteriorated.

  In the aging process, the rubber powder composed of the softening rubber / curing rubber composition added to the straight asphalt is gelled and mixed uniformly, and then aging is performed at a predetermined temperature for a predetermined time. A range of 150 ° C to 200 ° C is preferred. If the temperature is lower than 150 ° C., the normal melting state of the rubber powder composed of straight asphalt and softening rubber / curing rubber composition cannot be maintained. If the temperature exceeds 200 ° C., the asphalt rubber will cause thermal deterioration. . Further, when the aging time is less than 30 minutes, the aging effect cannot be sufficiently obtained, and therefore, 30 minutes or more is preferable.

Hereinafter, the present invention will be described in more detail with reference to examples.
(Example)
An asphalt rubber according to the present invention was prepared by the following procedure. Note that straight asphalt 60-80 manufactured by Nippon Oil Corporation was used as straight asphalt, and rubber powder made of an NR / SBR composition having a composition ratio (mass ratio) of 63/37 was used as rubber powder.

  First, straight asphalt was melted using a mantle heater (manufactured by Otsuka Denki Co., Ltd.) and heated to 180 ° C. Then, while stirring at 200 to 400 rpm using a stirrer, 12.5% by mass of rubber powder is added and stirred for about 30 minutes while maintaining at 180 ° C., and then aged in a constant temperature bath at 180 ° C. for 2.5 hours. Asphalt rubber was prepared.

  The asphalt rubber prepared in the above procedure was heated and stored at 180 ° C., and the viscosity of the asphalt rubber was measured after a predetermined number of days. For viscosity measurement, Viscotester VT-04F manufactured by Lion was used. The day immediately after aging was defined as day 0. The obtained results are shown in FIG.

(Comparative Example 1)
Asphalt rubber was prepared in the same procedure as in Example, except that rubber powder composed of NR was used as rubber powder, and the viscosity was measured in the same procedure. The obtained results are also shown in FIG.

(Comparative Example 2)
Asphalt rubber was prepared in the same procedure as in Example, except that rubber powder made of an NR / SBR composition having a composition ratio (mass ratio) of 37/63 was used as rubber powder. Measurements were made. The obtained results are also shown in FIG.

(Comparative Example 3)
Asphalt rubber was prepared in the same procedure as in the Examples except that rubber powder composed of SBR was used as rubber powder, and the viscosity was measured in the same procedure. The obtained results are also shown in FIG. The contents of the rubber powder used in Examples and Comparative Examples 1 to 3 are as shown in Table 1 below.

※１ ＪＳＲ（株）製 ＃１５００
※２ 大内新興化学（株）製 ノクラック６Ｃ
※３ 大内新興化学（株）製 リターダーＣＴＰ
※４ 大内新興化学（株）製 ノクセラーＤＭ
※５ 大内新興化学（株）製 ノクセラーＤ

* 1 # 1500 made by JSR Corporation
* 2 Nocrack 6C manufactured by Ouchi Shinsei Chemical Co., Ltd.
* 3 Retarder CTP manufactured by Ouchi Shinsei Chemical Co., Ltd.
* 4 Noxeller DM manufactured by Ouchi Shinsei Chemical Co., Ltd.
* 5 Noxeller D manufactured by Ouchi Shinsei Chemical Co., Ltd.

  From FIG. 1, when rubber powder (Example) comprising an NR / SBR composition having a composition ratio (mass ratio) of 63/37 is used, the viscosity of the asphalt rubber is stable even when heated and stored. I understand. This means that heat storage over a long period is possible. On the other hand, when rubber powder made of NR (Comparative Example 1) is used, the rubber powder is decomposed, so that the viscosity decreases with time, and the high viscosity that is characteristic of asphalt rubber cannot be maintained. Moreover, when the rubber powder (comparative example 2) which consists of a NR / SBR composition whose composition ratio (mass ratio) is 37/63, and the rubber powder which consists of SBR (comparative example 3) are used, the content rate of SBR is Since it is high, gelation occurs, the compatibility with asphalt is lowered, a stable viscosity cannot be obtained, and it can be seen that heat storage is difficult in either case.

It is a graph showing the viscosity change at the time of the heat storage at 180 degreeC of the asphalt rubber concerning an Example and Comparative Examples 1-3.

Claims (6)

  An asphalt rubber comprising a rubber powder comprising a rubber composition having a composition ratio (mass ratio) of softening rubber ≧ curing rubber as rubber powder in straight asphalt.   The asphalt rubber according to claim 1, wherein the composition ratio (mass ratio) is in the range of 50/50 to 80/20.   The asphalt rubber according to claim 1 or 2, wherein the content of the rubber powder comprising the softening rubber / curing rubber composition is in the range of 5 to 30% by mass.   The asphalt rubber according to any one of claims 1 to 3, wherein a particle size of rubber powder made of the softening rubber / curing rubber composition is in the range of 10 to 5000 µm.   The asphalt rubber according to any one of claims 1 to 4, wherein the softening rubber is natural rubber and the curable rubber is styrene butadiene rubber.   In the manufacturing method of the asphalt rubber according to any one of claims 1 to 5, a melting step of heating and melting the straight asphalt, and the softening rubber / Including an addition step of adding rubber powder made of a curable rubber composition, an agitation step of continuing stirring while maintaining the melting temperature or higher after the addition, and an aging step of aging in a thermostat after the stirring A manufacturing method of the asphalt rubber characterized.

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