JPS595621B2 - Reactive rubberized asphalt mixture for road paving and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rubberized asphalt mixture for road paving and a method for producing the same, and more particularly to a crosslinking reaction type rubberized asphalt mixture and a method for producing the same.

Currently, many types of rubberized asphalt or additives for producing rubberized asphalt have been developed and marketed as road paving materials, but no matter what type of material they are, they all undergo a crosslinking reaction. It is characterized by being used in a so-called uncured state.

However, when referring to rubber, it must naturally have rubber elasticity, and it goes without saying that this rubber elasticity can only be obtained through a crosslinking reaction caused by vulcanization. It is therefore clear that what is used in its unvulcanized state cannot be called rubber in the proper sense of the word. Also, the so-called "rubberized asphalt" to which "goshi material is added" used in such an unvulcanized state cannot be considered "rubberized asphalt" in the correct sense of the word.

Of course, various vulcanization attempts have been made to date in the production of rubberized asphalt, but none of them have been able to be put to practical use. The reason for this failure was that it was not possible to set appropriate conditions for the crosslinking reaction (curing) by vulcanization, including the selection of the type of vulcanizing agent. As a practical matter, when paving roads using a rubberized asphalt mixture, even if one attempts to vulcanize the rubber, if the crosslinking reaction (curing) has been completed before the mixture is compacted. However, the necessary and sufficient rolling pressure cannot be achieved, and a good pavement cannot be obtained.

In such a case, vulcanization into rubber only brings about negative results. Therefore, in order to obtain a rubberized asphalt pavement with rubber elasticity, the crosslinking reaction must not be completed at least until after compaction, and the rubberized asphalt composition must remain in a partially cured state until then. No. On the other hand, when true rubberized asphalt with rubber elasticity is used in road paving mixtures, the physical and chemical properties are significantly improved compared to ordinary straight asphalt. This has already been sufficiently proven through numerous laboratory tests.

In particular, excellent resistance to low-temperature embrittlement in cold regions and abrasion resistance in snowy regions, and on the other hand, problems that urgently need to be solved today in warm regions, including large areas of Japan, namely traffic volume. A remarkable effect achieved by rubber elasticity is the drastic improvement in resistance to flow deformation of the pavement surface, so-called "rutting", caused by a dramatic increase in rubber elasticity.

Generally speaking, problems that occur at low temperatures, especially low-temperature embrittlement and physical fracture in winter, and problems that occur at relatively high temperatures, that is, flow deformation at high temperatures in summer, can be solved using the same "rubber additive." This was an almost impossible requirement to be met at the same time.

That is, even if one of the requirements could be satisfied, the other requirement could not be met. The greatest industrial advantage of a truly rubberized asphalt mixture with rubber elasticity is that
The present invention is capable of satisfying these two requirements at the same time. Japanese Patent Publication No. 43-22319 can certainly be called an epoch-making invention in that it discloses the idea of producing rubberized asphalt having rubber elasticity.

That is, this patent relates to a method of producing a rubberized asphalt composition by reacting a polydiene intermediate polymer containing an allyl hydroxyl group as a functional group with an isocyanate to produce urethane, and blending the urethane with asphalt. However, when urethane and asphalt are blended, the urethane is blended in a state where at least a portion of the urethane is unhardened. According to this patent, the diene intermediate polymer used as the base agent usually has an average of at least 1.8 primary allylic hydroxyl groups per molecule at the ends of the hydrocarbon backbone; The viscosity of the body polymer is approximately 5 at 30°C.
~20,000 poise, preferably about 50-5,000
poise, and its average molecular weight is approximately 400 to 25,
000, is a liquid or flowable semi-solid at at least ambient temperature.

That is, the rubber material provided by this patent is a low-molecular liquid rubber, and the highly reactive allylic hydroxyl group contained at the end of its main chain bonds with isocyanate as a curing agent to cause a crosslinking reaction. However, the fact that a final paving mixture with rubber elasticity can thereby be obtained is certainly a novel idea.

However, to date, there has been no case in which a rubberized asphalt pavement mixture has actually been manufactured and applied based on the method of this patent.

This is because the specific conditions actually met for the production and construction of road paving mixtures were not met. According to this patent, as already mentioned, at the time of blending the urethane obtained by the reaction of a polydiene intermediate polymer containing an allyl hydroxyl group with an isocyanate and asphalt, at least one portion of the urethane is However, on the other hand, this polydiene intermediate polymer is blended at the temperature of normal asphalt pavement, that is, 120'F (approximately 49°C) to
It is specified that the ability to react with isocyanate compounds at temperatures of about 200 degrees Fahrenheit (approximately 94 degrees Celsius) is thought to be due in large part to this more reactive allyl structure.

It can be seen from this that the reaction conditions of the polydiene intermediate polymer and isocyanate in this patent are initiated by heating, and the reaction is initiated by heating, and the reaction The urethane must be in a partially unhardened state when combined with the asphalt, while the capacity for reaction is limited to a terminal temperature of 120 F' to 200 F'. It depends on the allyl structure of the functional group.

In other words, the partially unhardened urethane resin featured in this patent can be heated between 120'F (approximately 49°C) and 200'
It can only be maintained through a reaction at a relatively low temperature of F (approximately 94°C). However, this does not correspond to the practical requirements required for the production of road paving mixtures. That is, in general, when producing a road paving mixture in an asphalt plant, the asphalt is usually heated to at least 150°C to 165°C, and this heating temperature is set in consideration of the temperature at the time of construction. This is considered an essential condition.

Therefore, the above-mentioned reaction must also be considered to take place under these temperature conditions. However, according to the experiments conducted by the present inventors, the reaction according to Japanese Patent Publication No. 43-22319 was 140
It was confirmed that the reaction was already completed at ℃, and the urethane was completely cured.

For this reason, the method disclosed in Japanese Patent Publication No. 43-22319 could not be put to practical use. Based on the above facts, the inventors of the present invention have established a new method for producing a crosslinking reaction type rubberized asphalt mixture that can be put into practical use by eliminating the drawbacks of the method of Japanese Patent Publication No. 43-22319. succeeded in.

That is, an object of the present invention is to provide a new method that makes it possible to produce a crosslinking reaction type rubberized asphalt mixture in the process of producing an asphalt mixture for road paving in an existing asphalt plant.

Another object of the present invention is to provide a method for producing a rubberized asphalt mixture in which the crosslinking reaction (curing) of the rubberized asphalt is completed only after rolling compaction in the construction process.

Yet another object of the present invention is to provide a process for producing a rubberized asphalt mixture that is extremely easy to handle.

Yet another object of the present invention is to provide a rubberized asphalt mixture that is safe and easy to apply.

Yet another object of the present invention is to provide rubberized asphalt with rubber elasticity that has significantly improved resistance to both low-temperature embrittlement of pavement bodies in cold regions and flow deformation of pavement bodies in high-temperature regions. There is a mixture to serve.

Other objects of the invention will become apparent from the following description.

The rubber used in the present invention is a moisture-curable diene liquid rubber.

This includes polybutadiene, styrene-butadiene copolymer, polyisoprene, styrene-isoprene copolymer, polypentadiene, acrylonitrile-butadiene copolymer, polychloroprene, isobutylene-isoprene copolymer, butadiene and 2-15 carbon atoms. refers to a low molecular weight liquid rubber whose basic skeleton is a copolymer of higher alcohol with methacrylate, etc., which has isocyanate groups as functional groups at both ends of the main chain, and whose molecular weight is 500 to 50,000. do. This liquid rubber is characterized in that it hardens by absorbing a small amount of moisture, such as moisture in the air, without using a separate hardening agent.

That is, a crosslinking reaction is initiated by absorbing moisture, and the cured product obtained as a result has rubber elasticity as in the case of normal vulcanized rubber. As mentioned above, in the moisture-curable diene liquid rubber used in the present invention, moisture is the condition for the crosslinking and curing reaction, not heating.

Therefore, the reaction is not affected by the heating temperature of the asphalt or aggregate in the asphalt plant. Instead, the liquid rubber used in this invention must be stored well protected from moisture before being added to the molten asphalt.

That is, it is necessary to encapsulate the liquid rubber with a moisture-proof material.

As one means for this purpose, a moisture-proof synthetic resin film is recommended. In this case, the synthetic resin film must be moisture-proof and at the same time, when added to molten asphalt, immediately dissolve at the temperature of the molten asphalt.

Since asphalt is usually heated and melted at 150 to 165°C, a synthetic resin that melts at this temperature is selected. For example, films made from thermoplastic resins such as polyethylene, polypropylene, polyvinylidene chloride, and polyvinyl chloride are used. Of course, the method of protecting liquid rubber from moisture of the present invention is not limited to encapsulation with the thermoplastic resin film described above.

Store it naked in a moisture-proof container without wrapping it in a moisture-proof film, and when adding it to dissolved asphalt, heat it to 100°C or more in advance to make it completely moisture-proof. You can also reach your goal by. The mechanism of the curing reaction of liquid rubber according to the present invention is as follows. As mentioned above, compaction of asphalt mixtures generally needs to be carried out and completed at a temperature range of 140°C to 100°C, and especially in the case of rubberized asphalt mixtures, the viscosity of the mixture is somewhat high. Therefore, it is customary to carry out the process in a slightly higher temperature range than the above-mentioned temperature range.

This temperature range required for compaction is advantageous for the rubberized asphalt mixtures produced according to the invention. This is because as long as the rolling temperature is 100℃ or higher,
There is no risk of moisture being absorbed by the mixture. As a result, no hardening reaction occurs during the rolling process, and sufficient rolling can be performed. After compaction, on the other hand, the curing of the mixture must be completed in as short a time as possible.

In the case of the present invention, after the compaction of the mixture is completed, the temperature of the resulting pavement rapidly drops to below 100°C, and as a result, the pavement begins to absorb moisture and harden in a short period of time. be exposed.

According to experiments conducted by the inventors of the present invention, the curing reaction was almost completed within 24 hours.

In this way, a pavement with excellent rubber elasticity was obtained using exactly the same work as when constructing using a normal asphalt mixture. A rubberized asphalt mixture for road paving with such curing conditions has never been produced before in the history of rubberized asphalt, and in this sense it must be called a completely new product in itself.

As a concrete effect, asphalt paved roads face 2
The fact that two problems, namely low-temperature embrittlement in cold regions and flow deformation in high-temperature regions, can be solved simultaneously with the same product can be called truly revolutionary.

Furthermore, as a working advantage, the liquid rubber used in the present invention is a liquid rubber as seen in Japanese Patent Publication No. 43-22319, or a so-called "two-component type" as in epoxy.
However, since it is a "one-liquid type", it is extremely easy to handle and practical.

The addition ratio of liquid rubber to molten asphalt is 4 by weight.
~10%.

In this case, the addition ratio is based on the ratio of the mixture of molten asphalt and liquid rubber as 100. This means that a corresponding proportion of molten asphalt is replaced by liquid rubber. When the addition ratio is 4% or less, the effect of rubber addition is not significant, and when the addition ratio is 10% or less,
This is because in the above cases, no effect commensurate with the increase in costs can be obtained.

That is, adding more than that is useless. The asphalt used in the method of the present invention is an asphalt used in the production of ordinary road paving asphalt mixtures, and
No special limitations are required.

That is, a material having a penetration degree of 60 to 100 is used. In addition, the aggregate used in the method of the present invention is one that is used in the production of ordinary asphalt mixtures for road paving, and its particle size composition also complies with standards established by public bodies. does not require aggregates or special particle size formulations.

Further, there are no particular limitations on the location where the liquid rubber of the present invention is added to molten asphalt in an existing asphalt plant, but as a practical matter, the most desirable location is the asphalt measuring tank. That is, the liquid rubber is poured into an asphalt measuring tank in which one batch of asphalt is measured for each charge, and is added to and mixed with the molten asphalt. This is because the addition process itself is simple, and since the amounts of both asphalt and liquid rubber are small, the mixing of the two can be done easily and accurately. Furthermore, since it is added at each charge, there is no loss of liquid rubber, which is economical.

In contrast, pouring into an asphalt kettle is impractical to the point of being practically impossible. In addition, the moisture-curable diene liquid rubber is put into a mixer at the end of an asphalt plant, either as it is or wrapped in a moisture-proof synthetic resin film that melts at the temperature of molten asphalt, and then melted in the mixer. It is also possible to create a rubberized asphalt mixture by stirring and mixing with an asphalt mixture consisting of asphalt and heated aggregate, but in this case the liquid rubber is not added directly to the molten asphalt, but in a mixer. Since the asphalt and aggregate have already been mixed in the mixer and the asphalt mixture has already been prepared, the liquid rubber is added to the mixer to coat the surface of the finished asphalt mixture and then to fuse it with the asphalt. To do/become.

This is a suboptimal solution compared to the production of rubberized asphalt in a metering tank, but it is an option if adding to the metering tank is not possible for some reason.

In addition, moisture-curing diene-based liquid rubber or moisture-curing diene-based liquid rubber whose viscosity has been adjusted to be low with a solvent in a closed container such as a drum is charged into an asphalt measuring tank using appropriate pressure feeding equipment, and then converted into molten asphalt. It may be added and mixed. EXAMPLE 1 Batch Asphalt Mixture Production In an asphalt plant with a capacity of 1 ton, asphalt with a penetration of 80 was heated and melted in a kettle to 150°C, while aggregates having the following particle size composition were heated to 160°C.

On the other hand, a liquid polybutadiene crude MDI (4,4'-diphenylmethane diisocyanate) prepolymer having a molecular weight of 2,800 was charged into a polyethylene film bag capable of containing 500 gr.

The molten asphalt is sent from the kettle to an asphalt measuring tank, and in the same measuring tank, the amount of asphalt binder required to make one batch (1 ton) of asphalt mixture is 62 kg (6.2%), and the liquid rubber is If the amount added is 6% of the binder, the required amount of asphalt is 62
kg-621<g×6%=58.28kg, so 5
8 kg of asphalt was weighed and 4 kg of bagged liquid rubber was added to it. The rubberized asphalt obtained with the melting of the polyethylene bag was further conveyed to a mixer and mixed with aggregate heated to 160° C. in the mixer to obtain a rubberized asphalt mixture.

The rubberized asphalt mixture was transported to the construction site and immediately subjected to compaction work, but the surface temperature of the mixture at the start of compaction was 130°C, and at the end of compaction it was around 100°C. During the compaction process, the temperature of the mixture is 100
Since the temperature was above .degree. C., moisture absorption had not yet occurred, and the curing reaction was therefore rudimentary, so the compaction work was extremely easy and sufficient compaction could be completed.

The above rolling conditions are exactly the same as those for normal rolling of asphalt mixtures. Incidentally, after the compaction work was completed, as the surface temperature decreased to below 100°C, the curing reaction progressed. The road was immediately opened to traffic. Incidentally, before and after this, a marshal test, a wheel tracking test, and a thin film heating test were conducted in the test room, and the results are as follows.

(a) Standard Marshal Test Based on the median amount of asphalt binder that satisfies the standard value obtained from the results of the standard marshal test, the design amount of asphalt was set at 6.2%.

Further, a comparison test between two types of rubberized asphalt mixtures and a straight asphalt mixture (no rubber added) with a liquid rubber content of 4% and 8% is as follows.

(b) Wheel tracking test results The resistance to flow deformation of asphalt mixtures at high temperatures is generally determined by the British Transport and Road Research Institute (TRRL).
The so-called wheel tracking test developed by J.D. et al. was used, and this wheel tracking test was also used to determine the flow deformation resistance of the rubberized asphalt produced according to the present invention.

This test simulated the "ruts" caused by heavy vehicle running on an actual track and the kneading effect caused by repeated vehicle running, and tested the asphalt mixture at high temperature (60℃).
), the results of comparative tests on straight asphalt mixtures (without rubber addition) and asphalt mixtures to which various proportions of cross-linked liquid polybutadiene prepolymer according to the present invention were added are as follows. As shown in the table.

As is clear from Table 2, in the case of straight asphalt without rubber added, the deformation rate was 5.7 on the 35th day of curing, whereas in the case of 4% rubber added, the deformation rate was 2. .01 Furthermore, in the case of adding 8% rubber content, 0.4
%, it is shown that the deformation rate decreases in proportion to the increase in the amount of rubber added.

In particular, when the maximum addition amount is 8%, the latter value is actually less than i compared to the case where no addition is made. From this, it can be concluded that the addition of crosslinking liquid rubber has a remarkable effect on preventing flow deformation of the road pavement surface that occurs at relatively high temperatures.

(c) Experimental results regarding softening point and Fraas embrittlement point The resistance to flow deformation at high temperatures depends on the softening point of the asphalt binder, and the fracture resistance at low temperatures depends on the Fraas embrittlement point. For the sake of simplicity, we conducted an experiment to see how the moisture-curing liquid rubber of the present invention differs from a conventional straight asphalt binder without rubber additives at both high and low temperatures. The results are as follows.

The experiment used a rolling thin film heating method that simulates actual use.

As is clear from the above table, as the addition of liquid rubber increases, both the softening point and Fraas embrittlement point show a linear improvement. It is far more than that.

That is, in conventional asphalt-modifying additives, reaching a softening point of 60°C was already considered to be the greatest effect, so in the present invention, in the case of 6% addition, the softening point reached 82°C, 82°C. It must be said that in the case of % addition, the temperature reaches 135°C, which is an order of magnitude that is unimaginable from conventional common sense.

In addition, in the case of adding a conventionally known asphalt improver,
On the other hand, if the softening point of the liquid rubber of the present invention can be increased, the general situation is that it is actually worse than straight asphalt without additives when used in cold regions. In this case, the present invention not only maintains an order-of-magnitude improvement in softening point as described above, but also improves resistance to low-temperature embrittlement when used in cold regions as the amount of addition increases. This is an unexpected industrial effect due to the crosslinking reaction, and it can be concluded that this is clearly due to the effect of rubber elasticity due to the crosslinking reaction.

Claims (1)

[Claims] 1. Polybutadiene, styrene-butadiene copolymer,
Selected from polyisoprene, styrene-isoprene copolymer, polypentadiene, acrylonitrile-butadiene copolymer, polychloroprene, isobutylene-isoprene copolymer, copolymer of butadiene and methacrylate of higher alcohol having 2 to 15 carbons A road characterized by containing a moisture-curable diene liquid rubber having a basic main chain consisting of a rubber having a molecular weight of 500 to 50,000, and having isocyanate groups as functional groups at both ends of the main chain. Rubberized asphalt mixture for paving. 2 polybutadiene, styrene-butadiene copolymer,
Selected from polyisoprene, styrene-isoprene copolymer, polypentadiene, acrylonitrile-butadiene copolymer, polychloroprene, isobutylene-isoprene copolymer, copolymer of butadiene and methacrylate of higher alcohol having 2 to 15 carbons A moisture-curable diene liquid rubber having an isocyanate group as a functional group at both ends of the main chain and a molecular weight of 500 to 50,000 is added and mixed into molten asphalt. 1. A method for producing a rubberized asphalt mixture for road paving having rubber elasticity, which comprises preparing a rubberized asphalt composition and mixing it with heated aggregate. 3 polybutadiene, styrene-butadiene copolymer,
Selected from polyisoprene, styrene-isoprene copolymer, polypentadiene, acrylonitrile-butadiene copolymer, polychloroprene, isobutylene-isoprene copolymer, copolymer of butadiene and methacrylate of higher alcohol having 2 to 15 carbons A moisture-curable diene liquid rubber having an isocyanate group as a functional group at both ends of the main chain and a molecular weight of 500 to 50,000 is dissolved at the temperature of molten asphalt. A method for producing a rubberized asphalt mixture for road paving having rubber elasticity as claimed in claim 2, which is covered with a moisture-proof synthetic resin film. 4 polybutadiene, styrene-butadiene copolymer,
Selected from polyisoprene, styrene-isoprene copolymer, polypentadiene, acrylonitrile-butadiene copolymer, polychloroprene, isobutylene-isoprene copolymer, copolymer of butadiene and methacrylate of higher alcohol having 2 to 15 carbons Moisture-curable diene liquid rubber with isocyanate as a functional group at both ends of the main chain and a molecular weight of 500 to 50,000 is used as it is or in the form of molten asphalt. The liquid rubber is encapsulated in a moisture-proof synthetic resin film that melts at a certain temperature and then placed in a mixer of an asphalt plant, and the liquid rubber is stirred and mixed with an asphalt mixture consisting of molten asphalt and heated aggregate in the mixer. A method for producing a rubberized asphalt mixture for road paving having rubber elasticity.