JPH0443939B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved method for producing an asphalt mixture for paving, and more specifically, by dispersing a non-aqueous and non-solvent heat-melting rubber additive into an asphalt mixture using a specific (melt) kneading method. The present invention relates to a method for producing an asphalt mixture for pavement containing a rubber additive, which provides an asphalt pavement with significantly improved properties at high or low temperatures. Asphalt is widely used as a paving material for roads, parking lots, playgrounds, etc. because it is inexpensive and can be supplied in large quantities. ,
Problems such as cracks from winter to early spring, abrasion caused by tire chains and spiked tires, and shrinkage cracks due to temperature stress have always been exposed. These problems occur in asphalt mixtures.
Although the problem can be improved to some extent by changing the types and amounts of aggregate, filler, and asphalt and/or increasing the thickness of the pavement and strengthening the roadbed, no significant effects can be expected. Therefore, various attempts have been made to solve the above-mentioned problems with asphalt pavement by mixing certain additives with asphalt or asphalt mixtures (for example, Japanese Patent Publication No. 17317/1983; Special Publication No. 47-31083, Publication No. 8087-1987, Publication No. 13728-1987
(See 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-butadiene block or random copolymer, ethylene-butadiene block copolymer, styrene-butadiene block copolymer, styrene-butadiene block or random copolymer, propylene copolymer, ethylene-propylene-diene copolymer, isobutylene-isoprene copolymer, acrylonitrile-butadiene copolymer, chlorosulfonated polyethylene, acrylate ester polymer, etc.), thermoplastic polymers (polyethylene, polypropylene, tactical polypropylene, ethylene ethyl acrylate, ethylene vinyl acetate, etc.), various petroleum resins, waxes, antioxidants,
Anti-peeling agents and the like are used alone or in combination. These additives are usually melt-mixed 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 also referred to as "pre-preparation"). (referred to as "mixing method"). In this premixing method, the additives are dispersed in water in a mixer with a strong shearing force to form an emulsion, or in the form of a cutback with a suitable solvent and then added to hot melted asphalt. Add the additive little by little while stirring to evaporate and evaporate the water or solvent, or mix the additive with non-volatile heavy oil and then shred it and mix it into heated and molten asphalt. an asphalt premix containing a modifying additive is prepared by means such as dispersion;
However, all of these premixing methods require complicated steps, and often require heating and stirring at high temperatures for long periods of time.
This can easily lead to deterioration of components such as resin. Furthermore, the disadvantages of modified asphalt produced by the premixing method include storage in the production plant, transportation to a heated mixing asphalt plant (hereinafter referred to as "asphalt plant"), storage or remelting in the asphalt plant, heating bone The rubber and resin components contained in the materials are exposed to high temperatures for long periods of time during spraying and mixing, as well as transportation to the paving site, resulting in thermal decomposition and oxidative decomposition and polycondensation of the rubber and resin components. Often, the asphalt deteriorates and its benefits as a modified asphalt are substantially lost. Therefore, the preparation of modified asphalt premixes by the premixing method cannot be said to be an advisable means. On the other hand, in an asphalt plant, when producing an asphalt mixture by kneading heated aggregates, fillers, heated asphalt, etc., additives such as those described above are mixed in at the kneading stage (this method is referred to as a "plant mixing method"). is 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 is a method in which additives are put into a pug mill for mixing. In other words, in the production of a normal asphalt mixture, for each batch, a predetermined amount of heated (150 to 200℃) aggregate and room temperature filler are first dry kneaded for 5 seconds or more, and then a predetermined amount of heated (140 to 185℃) asphalt is mixed. Spray at high pressure from a spray bar and knead for 40 to 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 the case where the additives and asphalt are mixed immediately before addition), or the aggregate and asphalt are first kneaded, then the additives are added and secondly kneaded. Additives conventionally used in plant mixing processes are, for example, latex emulsions of thermoplastic rubbers, or powders, granules, flakes, emulsions of thermoplastic resins or polymers,
paste, etc., and these may be used alone or in combination. Although plant mixing methods using water-based emulsions (e.g. oil-in-water emulsions of styrene-butadiene copolymer) have a considerable track record,
According to this method, water, which accounts for approximately half of the emulsion components, vaporizes during melt-kneading, lowering the mixing temperature, and is time consuming since the components are added little by little. Needless to say, lowering the temperature and increasing the mixing time are undesirable since they increase the operating cost of the asphalt plant and reduce productivity in the long run. Furthermore, since some moisture remains even after construction, problems such as peeling and premature aging may occur. 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 185℃) is relatively low. Although easily melted, 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, it is difficult to avoid localized uneven distribution of additives even if kneading takes a long time. First, in order to improve the physical properties of the mixture as a whole, it is necessary to increase the amount added considerably. Furthermore, for example, when using a method in which rubber, resin, etc. are dissolved in a solvent and used in a liquid state, it may be easy to uniformly disperse the rubber, resin, etc. into the asphalt mixture, but if it is a flammable solvent, it will be difficult to use it at high temperatures. There is a risk of vaporization and ignition during handling, and there is also a danger 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. A so-called "cytomixing method" can be considered as a more suitable method than the above-mentioned plant mixing method. This site mixing method is a method in which an additive for asphalt modification is added to and kneaded into an asphalt mixture immediately before it is spread on a paving site such as a road or 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 at a finisher, and an asphalt mixture adjusted to a constant thickness is spread from the rear of the finisher in a slowly moving state. 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 temperature below 70°C. In addition, the recycling method, which has recently become popular, uses a ripper or remixer to excavate, crush, and remove the existing asphalt mixture.
The process involves heating, mixing, leveling, and compacting, and at this time, the oil and asphalt that are missing in the old asphalt mixture are added and refilled.
Additionally, new asphalt mixture may be added. Therefore, it is considered that there are many cases in which it is preferable to use a modifying additive in such a recycling method, and this recycling method is also referred to as the site mixing method here. Therefore, in this site mixing method, if the modifying additive can be uniformly mixed and dispersed in the asphalt mixture immediately before spreading, the heating time of the additive can be minimized, Deterioration of the properties of the additive can also 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 have conducted intensive studies on methods for solving the above-mentioned problems that occur when preparing asphalt mixtures for pavements containing modifying additives by the premixing method, plant mixing method, or site mixing method. As a result, a non-aqueous and non-solvent heat-melting rubber additive is adopted as a modification additive, and this is preferably mixed by a plant mixing method or a site mixing method.
It was discovered that it is suitable to mix it into an asphalt mixture, and the present invention was completed. According to the present invention, when producing a paving asphalt mixture from heated aggregates, fillers, heated asphalt, and a modifying additive, thermoplastic rubber and nonvolatile mineral oil are used as the modifying additive. A non-aqueous and non-solvent heat-melting rubber additive consisting of a composition obtained by combination use is used, and (a) heated aggregates, filler and the rubber additive are mixed in advance, and then the mixture is mixed. (b) Knead heated aggregates, filler, heated asphalt, and the rubber additive at the same time; or (c) Knead heated aggregates, filler, and heated asphalt. Provided is a method for producing an asphalt mixture for pavement containing a rubber-based additive, which comprises preparing an asphalt mixture, then adding the rubber-based additive to the mixture and further kneading the mixture. According to the present invention, a non-aqueous and non-solvent heat-melting rubber additive is used as the modifying additive, which does not contain water or volatile solvents.
A composition obtained by using a combination of thermoplastic rubber and non-volatile mineral oil, which is solid or semi-solid at room temperature and melts into a liquid state when heated. Various types of such additives are known, such as those made by mixing process oil with rubber ("Synthetic Rubber Handbook", November 1962).
Published on March 30th, Asakura Shoten, pages 555-556). These additives generally have a temperature of 300 mPa・S or less at 200°C, preferably 200 mPa・S.
It is desirable to have the following melting viscosity. In particular, the following composition: (a) Mineral oil containing a total of 35 to 80% by weight of aromatic and/or naphthenic hydrocarbons, an asphaltene content of 5% by weight or less, and a flash point of 200°C or higher;
A rubber additive consisting of 60 to 90 parts by weight and (b) 40 to 10 parts by weight of thermoplastic rubber can be easily liquefied, has excellent affinity with asphalt, and can be used to uniformly form an asphalt mixture in a short time. It is possible to disperse in
Moreover, the properties of the resulting pavement are excellent, and it has been found that it is optimal as an additive in the present invention. This optimal rubber additive will be explained in more detail below. The nonvolatile mineral oil used in the above additives generally has a boiling point (atmospheric pressure) of 350°C or higher, and is generally within the range of about 5 to about 70 centistokes, preferably 7 to 40 centistokes at 100°C. It can have viscosity. Such non-volatile mineral oils include vacuum distillate oil (process oil) obtained intermediately in the process of producing lubricating oil from crude oil, or aromatic and / or fractions rich in naphthenic hydrocarbons are suitable; industrially, for example, residual oils from atmospheric distillation after removing low-boiling components (e.g. gasoline, kerosene, light oil, etc.) from crude oil by atmospheric distillation; An extracted oil obtained by further subjecting the distillate obtained by distilling under reduced pressure to extractive distillation using furfural is advantageously used.
For example, MMO/Extract manufactured by Ciel Sekiyu Co., Ltd.
(Aromatic content 37% by weight, naphthene content 19% by weight, flash point 268°C. Viscosity 32 centistokes at 100°C);
SPO/Extract (aromatic content 45% by weight, naphthene content
LMO/Extract (40% aromatics, 27% naphthenes, flash point 230°C, viscosity 34 centistokes at 100°C); BS /Extract (aromatic content 19% by weight,
Naphthene content 34% by weight, flash point 254℃, viscosity 100℃
52 centistokes); Shellflex371JY (aromatic content 5% by weight, naphthene content 40% by weight, flash point 200℃,
Viscosity: 8.3 centistokes at 100°C); Shellflex 491JY (aromatic content: 4% by weight, naphthene content: 47% by weight, flash point: 220°C, viscosity: 9.8 centistokes). On the other hand, as the thermoplastic rubber that can be dissolved and dispersed in nonvolatile mineral oil and mixed into molten asphalt, unvulcanized rubber that has been conventionally used for rubber modification of asphalt is used in the present invention. can be used as well, for example natural rubber and various synthetic rubbers (e.g. polybutadiene,
Polyisoprene, styrene-butadiene copolymer rubber, chloroprene rubber, isoprene-isobutylene copolymer rubber, etc.) can be used, but in the present invention, in particular, rubber having a styrene content of 30 to 45% by weight and a molecular weight of 6.5×10 ⁴ to 15 Polystyrene-polybutadiene block copolymers with a styrene content of about 10×10 ⁴ and polystyrene-polyisoprene block copolymers with a molecular weight of about 10× ^{10 4} to 15×10 ⁴ are suitable. Examples include those commercially available from Ciel Kagaku Co., Ltd. under the trade names TR-1101 and TR-1107. The above-mentioned rubber additive can be prepared according to a method known per se. For example, non-volatile mineral oil as described above is heated in advance to a temperature of about 150 to about 200°C, and a small amount of the above-mentioned thermoplastic rubber is added thereto. This can be carried out by adding the ingredients gradually and uniformly dissolving them while stirring with a propeller mixer or the like. In this case, the blending ratio of thermoplastic rubber to nonvolatile mineral oil can be 40 to 10 parts by weight of thermoplastic rubber to 60 to 90 parts by weight of nonvolatile mineral oil, preferably 70 to 80 parts by weight of nonvolatile mineral oil. Thermoplastic rubber for 30 parts
~20 parts by weight. When preparing the asphalt mixture, the rubber additives described above can be heated and melted in advance to form a liquid, and then added in their entirety at once or in portions as necessary. In this case, (a) the additive is heated and melted, added to air-mixed heated aggregates and filler (at room temperature or heated) and kneaded, then heated asphalt is added and kneaded again, or (b) ) Add heated asphalt and the heated molten additives to air-kneaded heated aggregates and filler at the same time and knead, or (c) Knead pre-prepared heated aggregates, filler, 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 then kneading it. 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 solids content is in the range of 0.1 to 7% by weight based on the total amount of . Furthermore, it is generally desirable to use the additive in a range of about 0.25 to about 50% by weight, expressed based on the total amount of additive and asphalt. If the amount of the additive is less than the lower limit, the effect of the rubber will not be fully exhibited, and if it exceeds the upper limit, there will be negative effects due to excess rubber, that is, the viscosity of the asphalt mixture will be too high, making kneading and construction extremely difficult. This has the negative effect of creating pavement with poor performance or increasing 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 or the site mixing method, and it is of course possible to use it in the premixing method. In other words, when considering, for example, small-scale local construction, technical and
Of course, the method of the present invention can also be applied in cases where, for economic reasons, it is necessary to mix the additive into asphalt at a downstream production plant and transport it to the on-site asphalt plant. 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, and (b) heated and kneaded in the produced heated asphalt mixture. Immediately before leveling the asphalt mixture at the pavement site, add and knead it on a finisher (leveling machine); (c) Utilize old or damaged asphalt pavement as much as possible and regenerate it as new pavement. In the recycling method, a repairer (a scraping and leveling machine with a heating device), a remixer, and a remixer are used for old asphalt mixtures that have been crushed, heated, and loosened, or a composite mixture of that and newly manufactured heated asphalt mixtures. (A stirrer with a heating device,
It can be mixed and dispersed in the asphalt mixture by various addition and kneading methods, such as adding and kneading on a supplementary material, remixing, leveling machine), etc. In addition, examples of aggregates that can be used in the present invention include crushed stone, gravel, sand, etc., and examples of fillers include lime, cement, metal powder, mineral powder, etc. Furthermore, asphalt, for example, straight asphalt with a penetration of 60 to 80 and a softening point of 40 to 50℃; a penetration of 10 to 45 and a softening point of
Blown asphalt with a temperature of 75 to 130°C; and solvent-deasphalted asphalt with a penetration of 5 to 25 and a softening point of 55 to 80°C. The mixing ratio of these main components is the mixing ratio in a normal asphalt mixture for paving, for example, 97 to 85% aggregate and 3 to 15% asphalt by weight. The asphalt mixture produced according to the present invention contains tar, an elasticity improver, a viscosity lowering/improving agent, a tackifier, an antioxidant, an anti-peeling agent, a vulcanization accelerator, a filler, a 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 Manufactured by Ciel Sekiyu Co., Ltd. as a rubber additive
MMOE oil (38% aromatics, naphthenes)
A blend consisting of 72 parts by weight of styrene-butadiene block copolymer (styrene content: 30% by weight, molecular weight: 100,000) manufactured by Ciel Chemical Co., Ltd. (25% by weight, flash point: 255°C) was used. This compound is semisolid at room temperature, and becomes a liquid with a uniform composition when heated (viscosity: 210 mPa·S at 180°C). Asphalt mixture for pavement use was Ascon 13 with a dense particle size specified by the Japan Road Association, and the amount of the required binder (here, asphalt + rubber additive) was 5.3% by weight based on the total amount of the mixture. The mixture composition is aggregate + filler (hereinafter simply referred to as "aggregate")
94.70% by weight, asphalt 4.64% by weight, additives
The content was 0.66% by weight. The aggregate, asphalt, and additives were preheated and mixed at 178-171°C. The following three mixing methods were used in this case. 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: Asphalt and aggregate are kneaded, then additives are added and kneaded further. Regardless of the method used, the mixture was as smooth as the conventional mixing of only asphalt and aggregate. After mixing, compact the specimen for marshal test (approximately 10
cm, cylindrical shape with a height of about 6.4 cm) and a wheel tracking test specimen (cuboid shape with a size of 30 x 30 x 5 cm thick). The results of the marshal test and wheel tracking test are shown in Table 1 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 Ascon 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. Heat both in advance,
163 to 157 to obtain the same working viscosity as in Example 1.
It was mixed at 150-143°C and compacted at 150-143°C. The results of the marshal and wheel tracking tests are as shown in Table 1, and according to these, it is possible to obtain an apparently identical specimen with almost no difference in porosity from Example 1, but the deformation resistance at high temperature (60°C) is Example 1
It can be seen that it is extremely inferior. Comparative Example 2 A mixture similar to that described in Example 1 was prepared using a commercially available latex emulsion containing styrene-butadiene rubber (hereinafter referred to as "emulsion") that is often used in plant mixing methods. The emulsion contained 50% by weight of rubber, and this rubber content was calculated to be 5% by weight in the binder. Therefore, the mix is aggregate
94.70 parts by weight, straight asphalt (penetration 6
0/80) was 5.035 parts by weight, and the emulsion was 0.530 parts by weight. First, asphalt and aggregate were kneaded, and 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., 180±20 mm 2 /S for mixing and 180 ± 20 mm ² /S for compaction,
300± ^30mm2 /S) to 212~203℃ and 193~
The temperature was 184°C, but this temperature was too high, and there was a concern that the rubber would deteriorate especially if it exceeded 200°C. Therefore, 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 is much more difficult to knead than Example 1 in secondary kneading, and boils and evaporates water more gently. It took more than four times as long to do this, and the porosity of the compacted mixture was about 1% higher, probably due to the presence of moisture. As shown in Table 1, the results of the marshal test and wheel tracking test are far inferior to Example 1, which is only a slight improvement over straight asphalt and has a 1.5% less rubber content.

[Table] Example 2 In order to investigate the behavior of the 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 the Hokkaido Regional Development Bureau was used as the asphalt mixture for pavement, and the amount of binder required was 11.2% by weight. The mixture composition is 89.8% aggregate and asphalt.
The content was 9.8% by weight, and the additive content was 1.4% by weight. mixing temperature,
Compaction temperature and mixing method (3 methods A, B, C)
The procedure was the same as in Example 1. Compaction was performed using a known method on the labeling test specimen (40 x 15 x thickness 5
A rectangular parallelepiped (30 x 30 x 5 cm thick - prepared in the same manner as the wheel tracking test specimen described above) was prepared. This slab was cut using a diamond blade cutter to obtain a small piece measuring 23 cm long x 4 cm wide x 3 cm thick, which was used as a specimen for a bending test. Both the labeling test and the bending test were conducted at -10°C. The results are shown in Table 2 below. This shows that there is no difference between the three different mixing methods A, B, and C. Comparative Example 3 An asphalt mortar similar to that in Example 1 was produced using straight asphalt for pavement (penetration 80/100), which is relatively superior in the low temperature range among commercially available asphalts. In this case, the mix is aggregate 89.8
% by weight, asphalt was 11.2% by weight. The mixing temperature was 148-143°C, and the compaction temperature was 137-132°C. Table 2 shows the results of the labeling test and bending test.
According to this method, an apparently identical specimen with almost no difference in porosity from Example 2 can be obtained, but the impact resistance and flexibility at low temperatures (-10°C) are better than in Example 2. It can be seen that it is also extremely inferior. 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, 10.64 parts by weight of asphalt, and 1.12 parts by weight of emulsion. The mixing method and mixing temperature were the same as in Comparative Example 2. Comparing Method C of Example 2 with the kneading of this example, Comparative Example 4 is much more difficult to knead than Example 2 in secondary kneading, takes more than four times the time, and The porosity in the mixture after compaction also increased by about 1%. As seen in Table 2, the results of the labeling test and the bending test are far inferior to those of Example 2, which has a 1.5% lower amount of rubber.

【table】

Claims (1)

[Claims] 1. When producing an asphalt mixture for pavement from heated aggregates, filler, heated asphalt, and a modifying additive, the combination of thermoplastic rubber and nonvolatile mineral oil is used as the modifying additive. Using a non-aqueous and non-solvent heat-melting rubber additive consisting of a composition obtained by (b) Knead heated aggregates, filler, heated asphalt, and the rubber additive at the same time; or (c) Knead heated aggregates, filler, and heated asphalt to form asphalt. A method for producing an asphalt mixture for pavement containing a rubber-based additive, which comprises preparing a mixture, then adding the rubber-based additive to the mixture and further kneading the mixture.