JPS6114255A - Production of paving asphalt mixture containing rubber additive - Google Patents

Abstract

PURPOSE:To obtain the titled mixture having improved high-temperature and low-temperature properties, by kneading a heated aggregate, a filler, heated asphalt and a non-aqueous, non-solvent type hot-melt modifying rubber additive in a specified kneading manner. CONSTITUTION:A heated aggregate (A), a filler (B), heated asphalt (C) and a non-aqueous, non-solvent type hot-melt modifying rubber additive (D) (e.g. a mixture of rubber and process oil or a cumarone/indene resin) are separately prepd. Components A, B and D are mixed together, and the mixture is then kneaded with component C. Components A, B, C and D are kneaded together. Components A, B and C are mixed togethr, and the resulting asphalt mixture is kneaded with component D to obtain the titled paving asphalt mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an improved paving asphalt mixture, and more particularly, the present invention relates to a method for producing an improved paving asphalt mixture, and more particularly, the present invention relates to a method for producing an improved paving asphalt mixture, and more particularly, a non-aqueous and non-solvent based hot-melt rubber additive is added to The present invention relates to a method for producing an asphalt mixture for pavement containing a rubber additive, which provides an asphalt pavement with markedly improved properties at high and low temperatures.

Asphalt is widely used as a paving material for roads, parking lots, playgrounds, etc. because it is cheap and can be supplied in large quantities. Moats, cracks from winter to early spring, and tire chains. These problems include changes in the type and amount of aggregate, filler, and asphalt in the asphalt mixture, and/or increases in pavement thickness, and strengthening of the roadbed. Yes, it may be possible to improve it to some extent, but no significant effects can be expected.

Therefore, various attempts have been made to solve the above-mentioned opening angle of asphalt pavement by mixing additives in asphalt or asphalt mixtures (for example, Japanese Patent Publication No. 47-17317
Publication No. 47-31083, Special Publication No. 1983-
(See Japanese Patent Publication No. 8087, Japanese Patent Publication No. 5.6=13728, Japanese Patent Application Laid-open No. 57-66206, etc.). Specific examples of such modifying additives include thermoplastic rubbers (styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-styrene block copolymer,
Butadiene block or random copolymer, ethylene-
propylene co-X polymer, ethylene-propylene-diene copolymer, inbutylene-isoprene copolymer, acrylonitrile-butadiene copolymer, chlorosulfonated polyethylene, acrylic acid ester polymer, etc.), thermoplastic polymers (polyethylene, IJ propylene 1.Attactic polypropylene, ethylene ethyl acrylate, ethylene vinyl acetate, etc.), various petroleum resins, waxes, antioxidants, anti-peeling agents, etc. are used alone or in combination. There are 2.
(・5. These additives are usually melted in advance with heated asphalt to prepare an asphalt premix in which the additives are uniformly dispersed in the asphalt, and then mixed with aggregates and fillers. This method is called "premixing method"
). In this premixing method, the additives are either dispersed in water in a mixer with a strong shearing force to form an emulsion, or in the form of a cut-back product with a suitable solvent (and heated and melted). Add the additive little by little to asphalt while stirring and mix while evaporating and dispersing the aqueous solvent, or alternatively, mix the additive with non-volatile heavy oil and then shred it, then heat and melt it into asphalt. Asphalt premixes containing modifying additives are prepared by mixing and dispersing them in the asphalt. However, all of these premixing methods require complicated steps and require heating and stirring at high temperatures for long periods of time. This often leads to deterioration of the rubber, polymer, and resin components in the additives.Additionally, the disadvantages of modified asphalt produced by the premixing method include storage in the production plant, heating mixing asphalt plant ( below"
The rubber and resin components contained therein are exposed to high temperatures for long periods of time during transportation to asphalt plants (referred to as "asphalt plants"), storage or remelting at asphalt plants, spraying and mixing of heated aggregates, and transportation to paving sites. As a result, the rubber and resin components often undergo thermal decomposition, oxidative decomposition, and polycondensation, resulting in deterioration and, as a result, the advantages of modified asphalt are substantially lost. Therefore, the preparation of a modified asphalt premix by the premixing method is not a good method.

On the other hand, in an asphalt plant, when producing a 7-sphalt mixture by kneading heated aggregates, fillers, heated asphalt, etc., additives such as those mentioned above are mixed in at the kneading stage (this method is called the "plant mixing method"). ) are also being carried out. In a broad sense, this plant mixing method includes a method in which additives are introduced and dispersed into an asphalt heated storage tank installed in an asphalt plant, but generally heated aggregates and molten asphalt from the plant are mixed in a predetermined amount. This method involves putting additives into a pug mill for mixing. In other words, in the production of a normal asphalt mixture, each batch is heated by a predetermined amount (150
The aggregate (~200°C) and room temperature filler are first air kneaded for 5 seconds or more, and then a predetermined amount of heated (140~185°C) asphalt is sprayed at high pressure with a spray bar and kneaded for 40~50 seconds to finish. When adding additives to this pug mill, the aggregate and additives are first kneaded, then asphalt is added and kneaded for a second time, or the additives and asphalt are simultaneously added to the aggregate and kneaded ( (including cases where additives and asphalt are mixed immediately before addition), or
Alternatively, either aggregate and asphalt are first kneaded, then additives are added and second kneaded.

Additives conventionally used in plant mixing methods include, for example, latex emulsions of thermoplastic rubbers, or powders, granules, flakes, emulsions, pastes, etc. of thermoplastic resins or polymers, which may be used alone or in combination. Ru.

Plant mixing methods using aqueous emulsions (e.g. oil-in-water emulsions of styrene-butadiene copolymers) have a considerable track record, but with this method, water, which accounts for half of the 11tY in the emulsion components, is lost during melt-kneading. Vaporize and mix temperature ``4'' TL・+tf-1)
1"mt, ao"c'+*H""゛6" 1゜disadvantage.The decrease in temperature and increase in mixing time will increase the operating cost of the asphalt plant and reduce productivity in the long run. Therefore, it goes without saying that this is not desirable.

Furthermore, even after construction, some moisture remains, which may cause problems such as peeling and premature aging.

In addition, in the plant mixing method, in which additives are added in the form of fine pieces such as powder, fine particles, and flakes, the additives are in solid form, so the mixing temperature in the pug mill (usually 140 to 1
Although it melts relatively easily at 85° C.), it is very difficult to uniformly disperse the solid in an asphalt mixture within a limited time. Moreover, considering that the mixture has a fairly high viscosity, with more than 80% of the volume being occupied by aggregate and filler, local uneven distribution of additives can be avoided even if kneading takes a long time. figure,
In order to improve the physical properties of the mixture as a whole, it is necessary to increase the amount of addition to a considerable extent.

Furthermore, for example, there is a method of dissolving rubber, resin, etc. in a solvent and using it in a liquid state.
Although it may be easy to uniformly disperse resins, etc., if it is a flammable solvent, there is a risk of vaporization and ignition during handling at high temperatures, and there is also a risk of harm to the human body.

Furthermore, although there is no danger of ignition if the solvent is nonflammable, it may cause problems such as toxicity to the human body and corrosion of metal parts. Furthermore, although the solvent in such a case should originally be removed at the final stage, it is completely impossible to recover it, which is completely contrary to the viewpoint of energy saving.

The so-called "cytomixing method" can be considered as a more suitable method than the above-mentioned plant mixing method. This site mixing method is used to add asphalt modification additives to roads,
This is a method of adding and kneading the asphalt mixture to the asphalt mixture immediately before it is laid at a paving site such as a parking lot. Normally, in asphalt pavement, a heated asphalt mixture transported from an asphalt plant by a dump truck or the like is received by a finisher, and an asphalt mixture adjusted to a constant thickness is spread from the rear of the finisher while it is moving slowly. The temperature of the mixture at this time is at least 110°C or higher. Then, it is immediately compacted to a specified density using iron wheel rollers, rubber tire rollers, etc., and then opened to traffic at a maximum temperature of 70°C or less. In addition, the CYCLINK construction method, which has recently become popular, involves excavating, crushing, heating mixing, leveling, and compacting the existing asphalt mixture using a paper mixer or the like.
At this time, insufficient oil or asphalt may be added to the old asphalt mixture, or a new asphalt mixture may be added. Therefore, even in such a recycling method, it is considered that there are many cases where it is preferable to use a modifying additive, and herein, this recycling method is also referred to as the site mixing method.

Therefore, in this site mixing method, if the modifying additive can be uniformly mixed and dispersed in the asphalt mixture immediately before it is laid, the heating time of the additive can be minimized. Therefore, the deterioration of the properties of the additive can be minimized. However, even in this site mixing method, as long as emulsion type, solid form, or solvent type additives are used, there are problems similar to those described in the plant mixing method.

Therefore, the present inventors used a premixing method, a plate Q'/7g method, or a phytomixing method51.
As a result of intensive studies on methods to solve the above-mentioned problems that occur when preparing asphalt mixtures for pavements containing road-modifying additives, we found that non-aqueous and non-solvent heat-melted It has been found that it is suitable to adopt a mold rubber additive and mix it into an asphalt mixture, preferably by a plant mixing method or a site mixing method, and the present invention has been completed.

According to the present invention, when producing an asphalt mixture for paving from heated aggregates, fillers, heated asphalt, and a modifying additive, it is possible to use a non-aqueous and non-solvent-based heating melt as the modifying additive. Using molded rubber additives, and (a) premixing heated aggregates, fillers, and the rubber additives, and then adding heated asphalt to the mixture and kneading, or (b) heating aggregates, The filler, the heated asphalt, and the rubber-based additive are kneaded together, or (e) the heated aggregate, the filler, and the heated asphalt are kneaded to prepare an asphalt mixture, and then the rubber-based additive is added to the mixture. Provided is a method for producing an asphalt mixture for pavement containing a rubber-based additive, which comprises adding and further kneading.

Therefore, "non-aqueous and non-solvent heat-melt rubber additives" do not contain water or volatile solvents and are used for thermoplastic rubber alone, or for thermoplastic rubber and non-volatile process oils, resins, and waxes. A composition obtained by using a combination of additives, etc., which is solid or semi-solid at room temperature and melts and becomes liquid when heated, and various additives are known. For example, those made by mixing process oil with rubber, and those made by mixing Ronindene resin with rubber ("Synthetic Rubber Handbook", 1939).
Published on November 30, 2015, Asakai Shoten, pp. 555-556). These additives are generally 200
℃ 300 mpa・S or less, preferably 200 mpa・S or less
It is desirable to have a melting viscosity of mPa-8 or less.

In particular, the following composition: (a) Mineral oil 60-90, containing a total of 35-80% by weight of aromatic and/or naphthenic hydrocarbons, having an asphaltene content of 5% by weight or less, and a flash point of 200°C or higher.
parts by weight, and (b) thermoplastic rubber, which can be dispersed in a mixture consisting of 40 to 10 parts by weight, and the resulting pavement has excellent properties, making it ideal as an additive in the present invention. It has been found.

This optimal rubber additive will be explained in more detail below.

Mineral oils used in the above additives generally have a boiling point (atmospheric pressure) of 350°C or higher, and generally about 5 to about 70 centistokes at 100°C, preferably 7 to 70 centistokes at 100°C.
It can have a viscosity in the range of 40 centistokes. Such mineral oils include base oil (process oil) obtained intermediately in the process of producing lubricating oil from crude oil;
Alternatively, a fraction rich in aromatic and/or naphthenic hydrocarbons after removing at least a part of the paraffinic hydrocarbons therefrom is suitable; The extracted residue obtained by further subjecting the overhead fraction obtained by distilling the heavy distillation residue oil under reduced pressure after removing boiling point components (e.g. gasoline, kerosene, light oil, etc.) to extractive distillation using furfural is advantageous. used for.

Specifically, Shell Oil Co., Ltd. MMO/Ex t
rac tl, (aromatic content 37%, naphthene content 19%, flash point 268°C. Viscosity 32 centistokes at 100°C)
; SPO/Extract (aromatic content 45% by weight,
Naphthene content 19% by weight, flash point 220℃, viscosity 100℃
(18 centistokes): LMO/Extract
(Aromatic content: 40% by weight, naphthenic content: 27% by weight, flash point: 230°C, viscosity: 34 centistokes at 100°C);
BS/Extract (Aromatic content: 19 cm, naphthene content: 34% by weight, flash point: 254°C, viscosity: 5% at ioo°C)
2 centistokes); 5hellflex 37
LJY (aromatic content 5% by weight, naphthene content 40% by weight
, flash point 200℃, viscosity 8.3 centistokes at 100℃); 5hellflex 491 JY (aromatic content 4% by weight, naphthene content 47% by weight, flash point 220℃, viscosity 9.8 centistokes), etc. It will be done.

On the other hand, as the thermoplastic rubber that can be dissolved and dispersed in mineral oil and mixed into molten asphalt, unvulcanized rubber, which has been conventionally used for rubber modification of asphalt, is used in the present invention. For example, natural rubber or various synthetic rubbers (for example, polybutadiene, polyisoprene, styrene-butadiene copolymer rubber, chloroprene rubber, isoprene-isobutylene copolymer rubber, etc.) can be used. However, in the present invention, in particular,
Styrene content is 30-45% by weight and molecular weight is 6.5
x104~15X10' polystyrene-polybutadiene block copolymer and styrene content is 10X
A polystyrene-polyisoprene block copolymer with a molecular weight of about 10XIO' to 15x104 with a weight of 20% is suitable.
-.1101 and TR-1107 are commercially available.

The above additives are prepared according to methods known per se,
For example, the mineral oil as mentioned above is heated to about 150 to about 200°C in advance.
This can be done by heating the mixture to a temperature of 100 mL, gradually adding the above-mentioned thermoplastic rubber little by little, and uniformly dissolving it while stirring with a propeller mixer or the like. At that time, the blending ratio of thermoplastic rubber to mineral oil is 6
The amount may be 40 to 10 parts by weight of the thermoplastic rubber per 0 to 90 parts by weight, preferably 30 to 20 parts by weight of the thermoplastic rubber to 70 to 80 parts by weight of mineral oil.

When preparing an asphalt mixture, the additives mentioned above can be heated and melted in advance to form a liquid, and then added in their entirety at once or in several portions if necessary. In this case, (a) the additive is heated and melted, added to air-kneaded heated aggregates and filler (at room temperature or heated) and kneaded, then heated asphalt is added and kneaded again, or (b) ) Adding and kneading heated asphalt and a heat-molten cough additive to air-kneaded heated aggregates and fillers at the same time, or (c) Kneading pre-prepared heated aggregates, fillers, and heated asphalt. The additive can be uniformly dispersed in the asphalt mixture by adding the additive to the asphalt mixture by heating and melting it and kneading it further. Particularly from the viewpoint of preventing deterioration of additives, method (c) is preferable.

The amount of rubber additive used is not strictly limited, but for ordinary pavement asphalt mixtures that use 3 to 15% by weight of heated asphalt, the amount of rubber solids in the asphalt and the additive is It is appropriate to use the rubber additives in such a proportion that the rubber solid content is in the range of 0.1 to 7% by weight based on the total amount of the rubber additives. Also, if displayed based on the total amount of additives and 7 sulfate, the additives will be 1"
It is generally desirable to use a coulometric range of about 0.25 to about 50 coulombs. If the amount of the additive is less than the lower limit, the effect of the rubber will not be sufficiently achieved, and if it exceeds the upper limit, there will be a negative effect due to excess rubber, that is, the viscosity of the asphalt mixture will be too high, making kneading and construction extremely difficult. As a result, there are negative effects such as a pavement with poor performance or an increase in material costs.

The rubber additive in the present invention can be very easily dispersed in asphalt. Therefore, the present invention is not limited to the plant mixing method and the site mixing method, but can of course also be used in the premixing method. In other words, for example, when considering small-scale construction work in rural areas, for technical and economic reasons, it is not possible to mix this additive into asphalt at a downstream production plant and transport it to the site. Of course, the method of the present invention can also be applied to cases where no data is obtained.

Therefore, in the method of the present invention, the heated and melted rubber additives are (a) added and kneaded during the mixing stage when the heated asphalt mixture is produced in an asphalt plant; (b) heated and kneaded in the produced heated asphalt mixture; 1. Finisher (leveling machine) just before applying the asphalt mixture to the paving site.
(c) Old asphalt mixture that has been crushed, heated and loosened in a recycling method that utilizes old or damaged conventional asphalt pavement as much as possible and regenerates it as new pavement. A composite mixture of it and a newly produced heated asphalt mixture is processed using a repaper (a scraping and leveling machine with a heating device), a remixer (a scraping machine with a heating device, adding supplementary material, remixing, and leveling. It can be mixed and dispersed into an asphalt mixture by various addition and kneading methods such as adding and kneading on an asphalt mixer.

In addition, examples of aggregates that can be used in the present invention include crushed stone, gravel, sand, etc., and examples of the aggregate include lime, cement, metal powder, mineral powder, etc. moreover,
As the asphalt, for example, straight asphalt with a penetration degree of 60 to 80 and a softening point of 40 to 50°C; plane asphalt with a penetration degree of 10 to 45 and a softening point of 75 to 130°C; and ~25 with a softening point of 55-8
Examples include solvent-based asphalt at 0°C.

The mixing ratio of these main components is the proportion that is not mixed in a normal pavement asphalt mixture, for example, the weight ratio of aggregate is 97 to 8.
5ch, asphalt 3-15%.

The asphalt mixture produced according to the present invention may contain tar, elasticity improver, viscosity lowering/improving agent, tackifier, antioxidant, anti-peeling agent, vulcanization accelerator, filler, pigment, etc., as necessary. can be contained in an appropriate amount.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 As a rubber additive, 72 parts by weight of MMOE oil manufactured by Shell Oil Co., Ltd. (aromatic content 38% by weight, naphthene content 25% by weight, flash point 255°C) and styrene-butadiene manufactured by Shell Chemical Co., Ltd. Block copolymer (styrene content 30% by weight, molecular weight i o o, o.

0) 28 parts by weight was used. This 34'
It becomes a liquid with a strong composition (viscosity: 210 mps+・S at 180°C).

As the asphalt mixture for pavement, dense particle size Ascon (13) specified by the Japan Road Association is used, and the amount of the required binder (in this case, asphalt raw rubber additive) is 5% of the total amount of the mixture.
．． The content was 3% by weight. The composition of the mixture was 94.70% by weight of aggregate + filler (hereinafter referred to as "aggregate"), 4.64% by weight of asphalt, and 0.66% by weight of additives.

The aggregate, asphalt, and additives were heated in advance and mixed at 178-171°C.

The mixing method in this case was carried out in the following three steps.

Method A: Additives and aggregate are kneaded, then asphalt is added and kneaded further.

Method B: Asphalt is added to the aggregate, and additives are immediately added and kneaded without stirring.

Method C: Niassfald and aggregate are kneaded, then additives are added and kneaded further.

Regardless of the method used, mixing was as smooth and smooth as in the case of conventional mixing of only asphalt and aggregate. After mixing, compact the marshall test specimen (diameter approx. 10 CIIL, height approx.
．． A wheel tracking test specimen (30x30x rectangular parallelepiped with a thickness of 5α) was prepared. The results of the Marshall test and wheel tracking test are shown in Table IK below. This shows that there is no difference between the three different mixing methods A, B, and C.

Comparative Example 1 A mixture of dense-grained asphalt (13) similar to that described in Example 1 was produced using a commonly commercially available straight asphalt for pavement (penetration 60/80). The composition in this case was 94.7% by weight of aggregate and 5.3% by weight of asphalt. Both were preheated and mixed at 163-157°C to obtain the same working viscosity as in Example 1.
It was compacted at 0-143°C. The results of the Marshall and wheel tracking tests are shown in Table 1, and according to the results, the porosity is almost the same as that of Example 1.
However, it can be seen that the deformation resistance at high temperature (60° C.) is extremely inferior to that of Example 1.

Comparative Example 2 A mixture similar to that described in Example 1 was produced using a styrene-butadiene rubber-containing latex emulsion (hereinafter referred to as "emulsion") that is commonly used in commercially available plant mixing methods. The emulsion weighs 50-
It was calculated that this rubber content was contained in the binder in an amount of 5% by weight. Therefore, the composition is 94.70 parts by weight of aggregate, 5.035 parts by weight of straight asphalt (penetration 60/80), and 0.53 parts by weight of emulsion.
It was 0 parts by weight. First, asphalt and aggregate were kneaded, and an emulsion was added thereto for secondary kneading. The temperature during secondary kneading and compaction is usually within the optimum viscosity range for rubberized asphalt by premixing (i.e., mixing is 180-20m/S1 compaction is 300-30+
n+”/S > 212-203℃, 19
The temperature ranged from 3 to 184°C, but this temperature was extremely high, and in particular, if it exceeded 200°C, there was a concern that the rubber would deteriorate, so in this comparative example, the same temperature conditions as in Example 1 were adopted. Comparing Method C of Example 1 with the kneading of this example, Comparative Example 2 was much more effective at kneading than Example 1 in secondary kneading, and water boiling and evaporation. Due to the need to soften the process, the time is more than four times longer, and the porosity of the mixture after compaction is about 1% higher, probably due to the influence of existing moisture.
became. As shown in Table 1, the results of the Marshall test and wheel tracking test are far inferior to those of Example 1, which was a slight improvement over straight asphalt and contained 1.5% less rubber.

Example 2 To investigate the behavior of modified asphalt mixture at low temperatures,
An experiment was conducted using a rubber additive having the same composition as in Example 1. Asphalt mortar based on the standards of Hokkaido Prefecture was used as the asphalt mixture for paving, and the amount of binder required was 11.2% by weight.

The composition of the mixture is 89.8% by weight of aggregate and 9.8% by weight of asphalt.
8% by weight, and 1.4% by weight of additives. The mixing temperature, degree, compaction temperature, and mixing method (three methods, A and BSC) were the same as in Example 1. Compaction was performed using a known method to prepare a specimen for labeling test (cuboid of 40 x 15 x thickness of 5 cWL).
A slab (a rectangular parallelepiped of 30 x 30 x thickness of 5 cIIL - prepared in the same manner as the above-mentioned wheel tracking test specimen) was prepared. This slab was cut using a diamond blade cutter to a length of 23cIrL x width of 4clI.
A small piece measuring L x 3 mm in thickness was obtained and used as a specimen for bending test. Both the labeling test and the bending test were carried out at -10°C.
It was carried out in The results are shown in Table 2 below. From this A.

It can be seen that there is no difference between the three different mixing methods B and C.

Comparative Example 3 Straight asphalt for paving, which is relatively superior in low temperature range among commercially available asphalts (penetration 80/100)
An asphalt mortar similar to that in Example 1 was produced using the following. The composition in this case was 89.8% by weight of aggregate and 11.2% by weight of asphalt. Mixing temperature is 148-143
℃, and the compaction temperature was 137 to 132℃. The results of the labeling test and bending test are shown in Table 2, and according to K, the porosity is almost the same as in Example 2, and a specimen with a lower than apparent appearance was obtained, but at low temperature (-10°C) The difference is that the impact resistance and flexibility are extremely inferior to those of Example 2.

Comparative Example 4 A mixture similar to Example 2 was prepared using the same emulsion as in Comparative Example 2 above.

The rubber content in the binder was calculated to be 5% by weight. Therefore, the composition is 89.8 parts by weight of aggregate, 10 parts of asphalt)
．． 64 parts by weight, and 1.12 parts by weight of the emulsion. The mixing method and mixing temperature were the same as in Comparative Example 2. Comparing Method C of Example 2 and the kneading of this example, it was found that in both cases, the time required for the secondary kneading in Comparative Example 4 was much longer than in Example 2, and the time required was more than 4 times. Moreover, the porosity in the mixture after compaction was also about 1% higher.

As seen in Table 2, the results of the labeling test and the bending test are far greater than those of Example 2, in which the amount of rubber is 1.5 inches less.

Claims (1)

[Scope of Claims] When producing an asphalt mixture for pavement from heated aggregates, fillers, heated asphalt, and a modifying additive, a non-aqueous and non-solvent heat-melting rubber system is used as the modifying additive. Additives are used, and (a) heated aggregates, filler, and the rubber additive are mixed in advance, and then heated asphalt is added to the mixture and kneaded, or (b) heated aggregates, filler, and heated Either asphalt and the rubber additive are kneaded simultaneously, or (c) heated aggregates, fillers, and heated asphalt are kneaded to prepare an asphalt mixture, and then the rubber additive is added to the mixture and further kneaded. A method for producing an asphalt mixture for pavement containing a rubber additive.