JP2007023217A - Asphalt mixture and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an asphalt mixture which uses sulfur subjected to a flame-proofing treatment to produce the non-inflammable safe sulfur and gives paved articles having excellent economy and excellent qualities such as excellent rut resistance. <P>SOLUTION: Flame-proofed retardant sulfur prepared by modifying sulfur with a polymerizable compound or polymer, or preferably flame-proofed sulfur-containing granules prepared by adding mineral fine particles to the flame-proofed retardant sulfur and granulating the mixture to subject the sulfur to the secondary flame-proofing treatment and reduce smell, are used as a material for modifying asphalt mixtures. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an asphalt mixture and a method for producing the same, and more particularly to an asphalt mixture and a method for producing the same that provide a pavement excellent in quality and economy.

  The asphalt mixture used for pavement is a mixture of crushed stone, sand, etc. having an appropriate particle size distribution, with the addition of straight asphalt with a penetration in the range of 40-100, generally melted by heating. It is. However, on highways, etc., pavement made of asphalt mixture using straight asphalt has been rubbing, especially in the summer when the road surface temperature is high, due to an increase in traffic volume, particularly large vehicle traffic volume. Rutting is not only degrading the flatness of the road surface and impairing the driving comfort of the vehicle, but also rainwater stays in the rudder when it rains, causing poor visibility due to vehicle slip and water splash. It has become a big problem.

  For these reasons, the use of modified asphalt as a countermeasure for rutting is increasing. The purpose of asphalt modification is to improve the softening point, toughness (holding force), tenacity (caking force), and viscosity characteristics by mixing a modifier with straight asphalt. By using the modified asphalt, it is possible to reduce the occurrence of rutting due to flow and wear and the occurrence of cracks such as low-temperature cracks.

  As the modifier, rubber emulsions, thermoplastic resins, and recently, thermoplastic elastomers having intermediate properties are used. Examples of the thermoplastic elastomer include SBS (styrene-butadiene-styrene block copolymer) and SIS (styrene-isoprene-styrene block copolymer). However, since these modifiers are expensive, the price of modified asphalt reaches about 1.5 to 2 times the price of ordinary straight asphalt. Furthermore, since the asphalt price is on the rise due to the rise in crude oil price, there is a need to develop a reformer that is inexpensive and has excellent resistance to resistance.

On the other hand, sulfur is currently produced as a by-product mainly in the oil refining process. Conventionally, these sulfurs have been mainly used as raw materials for agricultural products such as fertilizers and chemical products such as sulfuric acid. In recent years, with the strengthening of environmental standards aimed at reducing environmental impacts, oil refiners have been required to remove more sulfur from gasoline, light oil and other fuel oils in order to reduce SO _X and NO _X. Yes. As a result, sulfur production is expected to increase greatly in the future, and if the consumption of sulfur does not increase as it is, the treatment of sulfur will develop into a major problem.

  Since sulfur is thermoplastic like asphalt, it can be mixed with asphalt relatively easily in the molten state. Moreover, since the sulfur mixture which uses the binder which has sulfur as a main component shows the intensity | strength more than cement concrete, the trial which utilizes sulfur as an asphalt modifier has been performed from before. As a result, it has been conventionally recognized that sulfur increases the viscosity of asphalt and is effective in improving resistance to rutting and preventing low-temperature cracks. Furthermore, since sulfur is cheaper than asphalt and can reduce the amount of asphalt for the amount of sulfur added, the effect of reducing material costs is also great. However, sulfur is a flammable hazardous material classified as a hazardous material class 2 of the Fire Service Act, and it is necessary to add a storage tank and piping equipment dedicated to molten sulfur to existing asphalt plants, restrictions on transportation and storage, melting Asphalt mixtures modified with sulfur have not been put into practical use because of concerns about the odor generated from sulfur and the influence of toxic gases on the surrounding environment.

  It is an object of the present invention to produce and provide an asphalt mixture using sulfur safely, inexpensively and efficiently. It is another object of the present invention to provide a method for minimizing the influence of the odor generated during the production of the asphalt mixture on the surrounding environment.

A first aspect of the present invention is an asphalt mixture characterized in that a flame retardant sulfur-containing granular material is used as the modifier in the asphalt mixture containing the modifier.
Secondly, the present invention is the asphalt mixture described above, wherein the flame-retardant sulfur-containing granular material is composed of a granular material obtained by melting and cooling solidified polymerization-modified sulfur in the presence of mineral fine powder.

Thirdly, the present invention is the above asphalt mixture containing a fragrance.
Fourthly, according to the present invention, an asphalt mixture is characterized in that the flame retardant sulfur-containing granular material is charged into a pug mill mixer of an asphalt plant and the sulfur content is dissolved by heat exchange with heated aggregate and / or molten asphalt. It is a manufacturing method.

  According to the present invention, an asphalt mixture that gives a pavement having excellent characteristics such as resistance to rutting can be produced at a low cost. Moreover, since the lifetime of a paving body can be extended by using such a mixture, it is possible to keep the life cycle cost of a road low.

  The flame-retardant sulfur-containing granular material used in the present invention is a granular material that is not classified as a non-hazardous material that does not fall under the category 2 of the Fire Services Act dangerous materials by flame-retarding sulfur. A typical example of the method for flame retarding sulfur is a method in which sulfur and a sulfur modifier are melt-mixed at, for example, 110 to 150 ° C. and subjected to polymerization modification. Examples of the sulfur modifier used at this time include olefinic compounds and polymers such as cyclopentadiene, tetrahydroindene, dipentene, vinyltoluene, dicyclopentene, cycloolefinic acid and oligomers thereof. Moreover, the mixture ratio of the sulfur modifier at this time is 0.01-30 mass% normally with respect to the total mass of sulfur and a sulfur modifier, Preferably it is 0.1-20 mass%. In this way, the primary flame retardant sulfur is mixed with mineral fine powder or the like under melting to further make it flame retardant (secondary flame retardant), and then cooled and solidified to form a granular material.

  Examples of the mineral fine powder include industrial waste such as natural aggregate, artificial aggregate, slag, coal ash, and garbage incineration ash. The blending ratio of the mineral fine powder is preferably about 20 to 50% by weight ratio with respect to the whole reforming material, and the particle size is preferably 70% or more and 75 μm or less.

  As a method for granulating the modifying material, there are a method of directly pelletizing the molten mixture, and a method of once cooling and solidifying the molten mixture and then crushing or pulverizing it. The shape and size of the granular material are not particularly limited, and a shape and size that are easy to handle are appropriately selected. Examples of the shape include a tablet shape, a pellet shape, a slate shape, a chip shape, a granular shape, and a powder. As the size, the maximum particle size is preferably 25 mm or less, particularly 5 mm or less, considering the ease of melting during the production of the mixture.

  By using the flame retardant sulfur-containing granular material thus obtained as a modifier for asphalt mixture, there is no need to use a melting material transport vehicle such as a lorry vehicle at the time of transport. A transport vehicle can be used. In addition, since the flame-retardant sulfur-containing granular material is solid, it is not necessary to provide a dedicated facility such as a storage tank in the asphalt plant, and a large amount of modifier can be transported and stored at one time. Further, if sulfur that has not been flame-retardant is granulated and put into a pug mill mixer, dust explosion may occur. However, since the modifier used in the present invention is flame-retardant, there is less risk.

  As a method of crushing or pulverizing the modifying material, there is a method of using an existing apparatus such as a crusher that has been conventionally used for producing crushed stones after the modifying material is solidified. However, in order to produce a modified material having a smaller particle size, the molten modified material is thinly laid on a belt conveyor or the like to a thickness equivalent to the target maximum particle size, and is cooled by natural or water cooling. An effective method is to perform pulverization using an existing apparatus such as a crusher after forcible cooling by means of, for example. As a granulation method, a method of dropping a molten material is suitable, and a technique used in the field of chemicals and plastics can be applied.

The method for producing the modified asphalt mixture in the present invention is the same as the method for producing a normal asphalt mixture except for the introduction of the modifying material. Each aggregate stored in the stockyard is put into a cold hopper and sent to the dryer by a cold feeder at a rate determined by the compounding design. Aggregate heated by a dryer is raised to the upper part of the batch tower by a hot elevator, classified by a vibration sieve, and put into each hot bottle for each size. The amount and ratio of aggregate determined by the formulation design for each production batch is transferred from the hot bottle to the measuring tank, and after weighing, it is put into the pug mill mixer. And the asphalt mixture of this invention is obtained by adding a modifier with the quantity of asphalt and stone powder determined by the mixing | blending design to this, and heat-mixing.
In order to add the modifying material processed into a small shape to the asphalt mixture, there are the following methods.

  (1) The modified material is put into a pug mill mixer and mixed with the heated aggregate. After mixing for several seconds to several tens of seconds, the modifier is melted by the heat of the aggregate, and the aggregate surface is coated with the modifier, and then asphalt is added.

(2) Asphalt is put into a pug mill mixer and put into heated aggregate. After mixing for several seconds to several tens of seconds and the aggregate surface is coated with asphalt, the modifying material is added. The modifier is melted by the heat of asphalt and aggregate.
(3) The asphalt and the modifying material are simultaneously introduced into the pug mill mixer and mixed with the heated aggregate. The modifier is melted by the heat of asphalt and heated aggregate.

(4) The modifier is introduced into the asphalt storage tank of the asphalt plant and dissolved. Stir for a minimum of several minutes and mix evenly, then throw into the mixer and mix with heated aggregate.
(5) Before carrying the asphalt into the asphalt plant, the asphalt and the modifying material are mixed in the asphalt manufacturing factory or storage facility.

In any of the above-described methods, asphalt and sulfur (modifier) are both thermoplastic materials, and can be sufficiently uniformly mixed in the process.
As in (4) and (5), it is possible to mix the modifier and asphalt in advance before putting into the mixer, but it is also possible to produce a normal type of asphalt mixture in the asphalt plant. Considering this, it is necessary to provide two pipes including a metering device from the binder storage tank to the mixer in order to prevent the binder from being mixed. Therefore, in order to produce the asphalt mixture in the present invention without adding equipment to an existing asphalt plant, the modified material processed into a small shape is directly charged into the mixer (1), (2) or (3 ) Method is desirable. In these methods, the modifier is in a molten state by heat exchange with the heated aggregate and molten asphalt in the mixer and is uniformly mixed into the asphalt mixture. At this time, the aggregate temperature is desirably high to some extent in order to facilitate the melting of the modifier, but if it is too high, the amount of generation of toxic gases such as SO ₂ and H ₂ S is increased. A temperature of about 180 ° C. is appropriate.

  If the amount of the modified material processed into a small shape is small, it may be introduced manually from the additive inlet installed in the pug mill mixer, but if the amount used is large, the additive It is desirable to use an automatic dosing device. In this case, it is not necessary to place a person at the location where the toxic gas is generated, which leads to improvement of the working environment.

  There is no particular limitation on the blending ratio of asphalt and modifier. Straight asphalt (penetration 60 to 80) has a viscosity at 160 ° C. of about 180 cp, but the viscosity of the modifier is about 1400 cp, so the higher the blending ratio of the modifier, the greater the viscosity of the binder. Thus, a higher reforming effect can be obtained. However, if the blending ratio of the modifier is large, the melting point of sulfur is higher than that of asphalt, so it is necessary to increase the production temperature of the asphalt mixture. In this case, the amount of sulfur odor and toxic gas generated from the asphalt mixture increases. There are concerns about the impact on the surrounding environment. Moreover, since the rigidity of the pavement made of an asphalt mixture increases, shrinkage / expansion cracks may occur as in cement concrete. On the contrary, if the blending ratio of the modifying material is small, the modifying effect on the asphalt mixture is not sufficiently exhibited, and the strength cannot be expected. From the results of the strength test using the specimen and other characteristic tests, the blending ratio of the modifier to the total binder weight (total weight of asphalt and modifier) is preferably about 50 to 80%. However, even when the blending ratio of the modifying material is made smaller than this value, asphalt can be replaced with an inexpensive sulfur modifying material, so that the economic merit is great.

  The amount of the modified binder added (the total weight of the asphalt and the modifier) is approximately the same as the amount of asphalt added during the production of a normal asphalt mixture in a volume ratio. However, since the specific gravity of sulfur is larger than that of asphalt, the weight ratio varies depending on the blending ratio of the modifier and asphalt.

  In the case of the above production methods (1), (2) and (3), the mixing time of the modified asphalt mixture in the mixer needs to be adjusted by the blending ratio of the modifying material. Although depending on the shape of the modifying material, the larger the blending ratio of the modifying material, the longer the time required for the modifying material to melt in the mixer. Therefore, it is necessary to extend the mixing time. The standard mixing time is 50 to 100 seconds.

  Since the modifying material mainly composed of sulfur may emit a sulfur odor and affect the surrounding environment at the time of melting, an air freshener may be added to reduce the sulfur odor generated from the modifying material. It is valid. Examples of the fragrance include amyl acetate and amyl acetate. The addition amount of the fragrance is appropriately about 0.1 to 0.3% of the total weight of the binder, although it depends on the blending ratio of the modifier. It is appropriate to add these fragrances to the modifier or asphalt in advance. However, the addition of the fragrance to the modifier can be expected to have a deodorizing effect both when producing the modifier and when producing the asphalt mixture. desirable. Further, it is known that fine powder materials containing iron oxide such as iron oxide and steelmaking slag absorb toxic gas generated from sulfur. Therefore, adding such a material to the reforming material is also effective as an odor reduction measure.

[Example]
Below, the manufacture example of the asphalt mixture using the modifier which has sulfur as a main component is shown.
Material mixing ratio:

Production method:
(1) 4.0% by weight of petroleum-based olefinic acid was mixed with the molten sulfur obtained in the process of petroleum refining to produce modified sulfur.
(2) Molten modified sulfur and coal ash discharged from a thermal power plant were mixed at a weight ratio of 2: 1, and amyl acetate was further mixed at 0.3% of the total weight.

(3) After the produced sulfur intermediate material was cooled and solidified, it was pulverized by a crusher so that the maximum particle size was about 5 mm to produce a modifier.
(4) The asphalt mixture was manufactured in an existing asphalt plant. The aggregate to be mixed with the binder was a natural aggregate similar to that used in a normal asphalt mixture.

(5) The process from when the aggregate was put into the mixer from the stock yard was the same as that of a normal asphalt mixture. The target heating temperature of the aggregate in the dryer was 170 ° C.
(6) After heating aggregate is put into the mixer from the aggregate metering tank, about 5 seconds by dry mixing, and about 30 seconds after the modifier is introduced from the additive inlet of the mixer, asphalt is placed in the asphalt measuring tank. About 50 seconds after mixing.

Test results:
As a result of testing the asphalt mixture, the Marshall stability was recorded at 30 kN or more, and the dynamic stability was recorded at 30,000 times / mm or more, which proved that the resistance to rutting was very high.

Claims (4)

  An asphalt mixture containing a modifying material, wherein a flame retardant sulfur-containing granular material is used as the modifying material.   2. The asphalt mixture according to claim 1, wherein the flame-retardant sulfur-containing granular material is a granular material obtained by melting and polymerizing modified sulfur in the presence of a mineral fine powder and then solidifying by cooling.   The asphalt mixture of Claim 1 or 2 containing a fragrance | flavor.   A method for producing an asphalt mixture, comprising introducing a flame-retardant sulfur-containing granular material into a pug mill mixer of an asphalt plant and dissolving sulfur by heat exchange with heated aggregate and / or molten asphalt.