SEO, Akira (4052-2 Nakatsu, Aikawa-CyoAikou-Gu, Aikou Kanagawa, 243-0303, JP)
SHELL CANADA LIMITED (400 - 4th Avenue S.W, Calgary, Alberta T2P 2H5, CA)
MORIKUBO, Michio (9F Otemachi Bldg, 1-6-1 Chiyoda-k, Tokyo Tokyo, 100-0004, JP)
SEO, Akira (4052-2 Nakatsu, Aikawa-CyoAikou-Gu, Aikou Kanagawa, 243-0303, JP)
C L A I M S
1. An asphalt binder characterised in that it contains 0.5 to 20.0% by mass of asphalt; the remainder comprises a petroleum-type solvent-extracted oil; the aromatic content is not less than 70.0% by mass; and the complex elastic modulus for 0.1 rad/sec at 25°C is not more than 10.0 Pa.
2. An asphalt binder according to claim 1, characterised in that the aforementioned asphalt is solvent deasphalted asphalt, straight asphalt, blown asphalt or a mixture of two or more kinds thereof, and the asphaltene content is not more than 40.0% by mass.
3. An asphalt binder according to claim 1 or claim 2, characterised in that the flash point is not less than 250 0 C. 4. An asphalt binder according to any preceding claim, wherein the petroleum-type solvent-extracted oil has a boiling point of not less than 350 0 C, a viscosity at 100 0 C of from 5 to 100 mPa.s, a flash point of not less than 25O 0 C and an aromatic content of not less than 75.0% by mass .
5. An asphalt binder according to any preceding claim, wherein the petroleum-type solvent-extracted oil is a Bright Stock Extract.
6. Use of an asphalt binder according to any preceding claim as an asphalt regeneration additive.
7. Use of an asphalt binder according to any one of claims 1 to 5 as a softener for new asphalt compositions which do not use asphalt pavement waste.
8. Use of an asphalt binder according to any one of claims 1 to 5 as an extender oil for styrene-butadiene- styrene block copolymers which are used as asphalt modifiers . |
ASPHALT BINDER
Field of the Invention
This invention relates to an asphalt binder to be added to asphalt compositions in order to modify hardness and aromatic content, and in particular to an asphalt binder suitable as a softener for reclaimed asphalt, rubber extender oils and blending oils. Background of the Invention
In recent years there has been increasing re-use of asphalt pavement waste, but because, in general, the asphalt component in the waste has deteriorated and hardened, it is not possible to ensure sufficient penetration or elongation without further action, and there are problems associated with cracks appearing early in re-used paving. Also, it is known that, because of the deterioration of the pavement, the aromatic component in the asphalt decreases (Tonishi Tomotsugu, "Investigation of the physical science aspects of modified asphalts" , Reports in brief by outside researchers in 1994, pages 167-170, Public Works Research Centre, June 1995; and Tateishi Daisaku, "Investigation of the physical science aspects of modified asphalts" , Reports in brief by outside researchers in 1994, pages 229-232, Public Works Research Centre, June 1996) . Hitherto, when re-using asphalt pavement waste, it has been softened by adding highly aromatic animal or vegetable oil-type additives, such as extracts, or pitch-type additives to supplement the asphalt component. Among these additives used in reclaiming asphalt, the addition of highly aromatic mineral oils in particular can bring the asphalt component in deteriorated asphalt waste close to asphalt
which does not use asphalt waste material - in other words, close to the composition of new asphalt - so that the flexibility and suppleness of the reclaimed asphalt are improved, and this is effective in guaranteeing in- service performance (especially not being prone to cracking) . However, there are problems in that these asphalt regeneration additives have poor flowability at normal temperatures (around 25 0 C) and workability deteriorates . Asphalt regeneration additives have therefore been proposed which are designed to improve workability during reclaiming of the asphalt by lowering the kinematic viscosity at normal temperatures. Japanese Laid-open Patent 2-91303 discloses an additive for regenerating asphalt pavement waste comprising a mineral oil wherein the aromatic content is 7 to 35%, the pour point is -5 0 C or less, the kinematic viscosity at a temperature of 40 0 C is 30 to 500 mm 2 /sec and the flash point is not less than 230 0 C, and as embodiments thereof it cites, for example, a paraffin type dewaxed lubricating oil and a mixture of a paraffin type dewaxed lubricating oil and a naphthene type extract. Further, Japanese Laid-open Patent 8-333515 discloses an additive for regenerated asphalt comprising an extract oil wherein the kinematic viscosity at 40 0 C is 600 to 2000 mm 2 /sec and the aniline point is no more than 35°C.
Japanese Laid-open Patent 2005-154464 discloses an asphalt regeneration additive composition which is a composition obtained by blending with fats or oils a mineral oil wherein the kinematic viscosity at 40 0 C is
300 to 900 mm 2 /sec and the polycyclic aromatic content is less than 3% by mass, and whereof the kinematic viscosity at 40 0 C is 40 to 400 mm 2 /sec, the polycyclic aromatic
content is less than 3% by mass and the flash point is not less than 220 0 C. Furthermore, Japanese Laid-open Patents 2005-154465 and 2005-154467 disclose additive compositions obtained by blending a mineral oil with fats or oils or a fatty acid alkyl ester compound. The kinematic viscosity of the mineral oil at 6O 0 C is 100 to 1000 mm 2 /sec. The kinematic viscosity of the additive composition at 60 0 C is 20 to 300 mm 2 /sec and the flash point of the additive composition is not less than 21O 0 C or 22O 0 C. Yet further, Japanese Laid-open Patent 2005- 154469 discloses an asphalt regeneration additive composition wherein the kinematic viscosity at 60 0 C is 30 to 200 mm 2 /sec, the polycyclic aromatic content less than 3% by mass, the flash point is not less than 220 0 C, the aromatic content is 10 to 20%, and the initial boiling point according to gas chromatography distillation is not less than 28O 0 C.
However, there are problems in the aforementioned prior art, as illustrated below. The additives used for asphalt regeneration as described in the prior art reduce the kinematic viscosity by reducing the aromatic content, and so ensure flowability at normal temperatures, but, as mentioned above, because the aromatic content has decreased owing to deterioration in the asphalt pavement waste, if additives for asphalt regeneration are used where the aromatic content is small, as described in the prior art, the aromatic content in the entire regenerated asphalt composition is reduced. As a result, the regenerated asphalt composition cannot be brought close to the composition of new asphalt, and there will be problems such as a reduction in flexibility and suppleness in the pavement after laying, and early cracking may occur.
This invention has been devised to solve these problems, and its aim is to provide an asphalt binder with good workability by improving flowability at normal temperatures without reducing the aromatic content. Summary of the Invention
The asphalt binder relating to this invention is characterised in that it contains 0.5 to 20.0% by mass of asphalt; the remainder comprises a petroleum-type solvent-extracted oil; the aromatic content is not less than 70.0% by mass; and the complex elastic modulus for 0.1 rad/sec at 25 0 C is not more than 10.0 Pa.
In this invention, because the complex elastic modulus for 0.1 rad/sec at 25 0 C is set at not more than 10.0 Pa, flowability at normal temperatures is excellent, and workability can be made satisfactory in comparison with additives of the prior art. Also, because the aromatic content is not less than 70.0% by mass, if it is used as an additive for asphalt regeneration, it is possible to bring the composition of the regenerated asphalt close to the composition of new asphalt, and so it is possible to improve the flexibility and suppleness of the pavement. In other words, by using the asphalt binder of this invention, regenerated asphalt compositions with similar characteristics to those of asphalt compositions which do not use asphalt pavement waste are obtained.
Also, it is preferable that the aforementioned asphalt is a solvent deasphalted asphalt, straight asphalt, blown asphalt or a mixture of two or more kinds of these asphalts and has an asphaltene content of not more than 40.0% by mass. By virtue of this, it is possible to improve the workability (flowability) of the asphalt binder at normal temperatures without diluting
the aromatic content within the petroleum-type solvent- extracted oil. Further, because the amount of these asphalts in the blend is made a specific amount (not more than 20.0% by mass), large rises in the asphaltene content in the asphalt composition are inhibited, and solubility with rubbers such as SBS (styrene-butadiene- styrene) can be made satisfactory.
The asphalt binder of this invention also preferably has a flash point of not less than 250 0 C. By virtue of this, the safety of the asphalt binder is increased and handling becomes easier.
According to this invention, because a suitable amount of asphalt is mixed with a petroleum-type solvent- extracted oil, the aromatic content is not less than 70.0% by mass and the complex elastic modulus for 0.1 rad/sec at 25°C is set at not more than 10.0 Pa, it is possible to improve flowability at normal temperatures without reducing the aromatic content, and to improve workability without reducing the characteristics of the pavement material even when it is used as an additive for asphalt regeneration.
Brief Explanation of Drawing
Figure 1 is an oblique view showing schematically the measuring portion of the rheometer. Detailed Description of the Invention
The invention is described in detail below with regard to its optimum form of embodiment. The inventors have undertaken intensive research in order to achieve satisfactory workability by improving the flowability of asphalt binders which are used as softeners for reclaimed asphalt, rubber extender oils and rubber blended oils, and specifically in order to simplify pouring from storage containers such as drums and pails, and transfer
by means of pumps (in particular, flow within pipes at start-up time) . As a result, they discovered that, under such conditions of use, and in particular when initiating a flow, because a very slow force acts on the asphalt binder (the weight, if pouring from a storage container, the pressure if transferring by means of a pump) , it is possible to obtain the flowability that is required in these operations if the complex elastic modulus is measured at a slow load frequency of the order of 0.1 rad/sec (0.0159 Hz) at 25°C and if the value thereof is not more than 10.0 Pa. They arrived at this invention by further discovering that the complex elastic modulus for 0.1 rad/sec at 25°C becomes not more than 10.0 Pa if asphalt is added in specified proportions to a petroleum- type solvent extracted oil used in the prior art as an additive for asphalt.
In other words, the asphalt binder of this invention is a mixture of asphalt (0.5 to 20.0% by mass) and petroleum-type solvent extracted oil (80.0 to 99.5% by mass) . The aromatic content in the additive as a whole is not less than 70.0% by mass, and the complex elastic modulus for 0.1 rad/sec at 25°C is not more than 10.0 Pa.
An explanation is given below of the reasons for limiting the values in the asphalt binder of this invention.
Asphalt at 0.5 to 20% by mass: Asphalt is added in order to improve flowability at normal temperatures and to improve compatibility with the asphalt composition. However, if the asphalt content is less than 0.5% by mass, these effects are not obtained. On the other hand, if the asphalt content exceeds 20.0% by mass, the proportion of the petroleum-type solvent-extracted oil becomes too small and there is virtually no flow at
normal temperatures, so that workability is reduced. Furthermore, an increase in the asphaltene content is induced and there will also be some reduction in compatibility with rubbers such as SBS. Consequently, the asphalt content is made 0.5 to 20.0% by mass.
For the asphalt of this invention it is possible to use, for example, those which are straight asphalt (see JIS K2207) , solvent deasphalted asphalt (see "New Petroleum Dictionary" , edited by the Institute of Petroleum, 1982, p. 308), blown asphalt (see JIS K 2207), or mixtures of two or more of these, and where the asphaltene content is not more than 40.0% by mass. As well as the fact that these asphalts are all easy to procure, and so are suitable for use in, for example, community infrastructure such as roads, it is possible to improve the workability (flowability) of asphalt compositions at normal temperatures without diluting the aromatic content within the petroleum-type solvent- extracted oil. However, if the asphaltenes in the asphalt exceeds 40.0% by mass, compatability with rubbers such as SBS will decrease. Therefore, it is preferable to use those where the asphaltene content is not more than 40.0% by mass. By this means, it is possible to limit the total asphaltene content in the asphalt binder to not more than 10.0% by mass. Normally, asphalt has of the order of at least 5.0% by mass of asphaltenes.
Petroleum-type solvent extracted oil at 80 to 99.5% by mass: Petroleum-type solvent-extracted oils are extracted oils produced during solvent extraction processes when making lubricating oils from crude oil, and are oily substances rich in aromatic and naphthenic components (see "Before petroleum products are made", Figure 6-1 'General lubricating oil manufacturing
processes', published by the Sekiyu Renmei, November 1971, p. 99, and "New Petroleum Dictionary", edited by the Institute of Petroleum, 1982, p. 304). When these petroleum-type solvent-extracted oils are added to asphalt compositions, they are the component which acts as a softener, and it is preferable if the boiling point is not less than 350 0 C, the viscosity at 100 0 C is 5 to 100 mPa.s, the flash point is not less than 250 0 C and the aromatic content is not less than 75.0% by mass. An example of such petroleum-type solvent-extracted oils is the Bright Stock Extract, extracted by means of solvents such as phenol, N-methylpyrrolidone, liquid sulphur dioxide and furfural. If the content of this petroleum- type solvent-extracted oil is less than 80.0% by mass, the flowability decreases and satisfactory workability is not achieved. On the other hand, if the content of this petroleum-type solvent-extracted oil exceeds 99.5% by mass, the flowability again decreases and satisfactory workability is not achieved. Consequently, the content of this petroleum-type solvent-extracted oil is set at 80.0 to 99.5% by mass.
Aromatic content of not less than 70.0% by mass: The aromatic content influences the characteristics as pavement material, and in particular the flexibility and suppleness of the pavement. As mentioned above, because asphalt pavement waste has a reduced aromatic component owing to deterioration, if it is used as the raw material of an asphalt composition, it is necessary to increase the aromatic content in the additive. Specifically, if the aromatic component of the asphalt binder added is less than 70.0% by mass, when it is mixed with the depleted asphalt (asphalt pavement waste) , the aromatic content cannot be sufficiently increased. In other words,
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the regenerated asphalt cannot be brought close to the composition of new asphalt composition, and so it becomes difficult to improve the flexibility and suppleness of the pavement, and cracks will occur soon after laying. Consequently, in the asphalt binder of the invention the aromatic content is set at not less than 70.0% by mass. The aromatic content specified in this invention can be obtained by chromatograph development of the component extracted by means of a mixed solution of dichloromethane (95% by mass) and methanol (5% by mass) from the residue after extracting and developing the asphalt binder in n- hexane and toluene then detecting by means of a hydrogen flame, using, for example, thin- layer chromatography.
Complex elastic modulus for 0.1 rad/sec at 25 0 C of not more than 10.0 Pa: As mentioned above, the objective aimed at by improving workability in this invention is an operation whereby a slow force acts at normal temperatures, and therefore it is necessary to improve flowability by reducing the complex elastic modulus for 1 rad/sec at 25 0 C. Specifically, if the complex elastic modulus for 1 rad/sec at 25°C exceeds 10.0 Pa, there is virtually no flow at normal temperatures, so that workability during pouring from storage containers and during transfer is reduced. Consequently, the complex elastic modulus for 1 rad/sec at 25°C in the asphalt binder of this invention is set at not more than 10.0 Pa.
The complex elastic modulus G* specified in this invention can be measured by a rheometer. Figure 1 is an oblique view showing schematically the measuring portion of the rheometer. Specifically, as shown in Figure 1, the asphalt binder 1 is sandwiched between two parallel discs 2a and 2b, a sinusoidal strain of the specified frequency is applied to one disc 2a and the sinusoidal stress σ
transmitted to the other disc 2b through the asphalt binder 1 is measured. The measurement conditions at this time are: diameter of discs 2a and 2b: 40 mm; thickness of asphalt binder 1: 1 mm; strain: 10%. The complex elastic modulus G* is obtained from the mathematical formula 1 (see below) on the basis of the results of these measurements, Y in the undermentioned Mathematical Formula 1 is the maximum strain applied to the disc 2a.
Mathematical formula 1
G* = σ Y
Japanese Laid-open Patent 2000-186211 discloses an invention which specifies the complex elastic modulus of an asphalt composition, but the aim of that invention is to ensure the elongation when re-using asphalt pavement waste, and it specifies a complex elastic modulus for 10 rad/sec (1.59 Hz) at 15 0 C. In other words, it is different from the aim of the present invention and so the measurement conditions of the complex elastic modulus differ. In the case of an asphalt composition and the asphalt binder added thereto, generally, if the load frequency at the time of measurement differs, the behaviour differs, and so just because the complex elastic modulus at 10 rad/sec may be low, it is not necessarily the case that the complex elastic modulus at 0.1 rad/sec is low. In other words, because, as in this invention, the flowability during work when a slow pressure is acting is improved, a load frequency of 10 rad/sec is too fast a condition, and it is necessary to evaluate the complex elastic modulus by measuring at the slower load frequency of 0.1 rad/sec.
Also, for the asphalt binder of this invention a flash point of not less than 250°C is preferred. In this way, the safety of the asphalt binder increases and both use and storage are easier, so that workability can be improved.
As mentioned above, because, in the asphalt binder of this invention, the complex elastic modulus for 0.1 rad/sec at 25 0 C is not more than 10.0 Pa, flowability at normal temperatures is excellent, and it is possible to achieve good workability during operations where a slow force is applied as when pouring from storage containers or conveying by pump. Also, because the asphalt binder of this invention has a high aromatic content of not less than 70.0% by mass compared with the asphalt regeneration additives of the prior art, the flexibility and suppleness of the pavement are improved even when using it as an asphalt regeneration additive, and it has the same characteristics as when using new asphalt compositions which do not use asphalt pavement waste. The asphalt binder of this invention may be used not only as an asphalt regeneration additive as described above, but also as a softener for new asphalt compositions which do not use asphalt pavement waste. Also, because the asphalt binder of this invention has a high aromatic content and excellent compatibility with styrene, it can also be used as an extender oil for SBS polymers (styrene-butadiene-styrene block copolymers) which are used as asphalt modifiers (stiffeners) . The effect of the invention is explained more specifically below by giving examples of embodiment and comparative examples. In the examples of embodiment, a petroleum-type solvent-extracted oil and a deasphalted asphalt, straight asphalt or mixture thereof or blown
asphalt were mixed in the proportions shown in Table 1 using a propeller mixer, to produce the asphalt binders for the examples of embodiment and comparative examples. The mixing conditions at this time were a mixing temperature of 17O 0 C, mixing time of 30 minutes and mixer speed of 3000 revolutions per minute. Also, the examples of embodiment used a petroleum-type solvent-extracted oil with a viscosity at 100 0 C of 0.060 Pa. s, density at 15°C of 974.2 kg/m 3 , flash point of 325°C, aromatic content of 80.7% by mass, and asphaltene content of 0.9% by mass.
The solvent deasphalted asphalt had a penetration at 25°C of 8 (1/10 mm), softening point of 66.5°C, density at 15 0 C of 1028 kg/m 3 , flash point of 352°C, aromatic content of 61.1% by mass, and asphaltene content of 14.0% by mass. The straight asphalt had a penetration at 25 0 C of 62 (1/10 mm), softening point of 48.O 0 C, density at 15 0 C of 1033 kg/m 3 , flash point of 36O 0 C, aromatic content of 47.7% by mass, and asphaltene content of 17.8% by mass. The blown asphalt had a penetration at 25°C of 34 (1/10 mm), softening point of 102.0 0 C, density at 15 0 C of 1035 kg/m 3 , flash point of 356 0 C, aromatic content of 38.3% by mass, and asphaltene content of 31.0% by mass. The lubricating oil had a density at 15°C of 884.6 kg/m 3 , flash point of 246°C, kinematic viscosity at 100 0 C of 11.3 mm 2 /sec, aromatic content of 29.7% by mass, and asphaltene content of 0.2% by mass.
Table 1
Next, the aromatic content in the asphalt binders of each of the examples of embodiment and comparative examples, the viscosity at 60 0 C and the complex elastic modulus for 0.1 rad/s at 25°C were measured. The aromatic content was measured using a thin-layer chromatography auto-detector (Iatroscan MK- 5) made by Mitsubishi Kagaku Co. Ltd. by the method described above. Also, the viscosity at 60 0 C was measured using a rotational viscometer made by Brookfield. The measurements were made for a No. Sc4-21 rotor and measurement speed of 20 rpm. Further, the complex elastic modulus G* at 25°C was measured by the method mentioned above using a rheometer made by TA Instruments (ARES) . The results are combined into the aforementioned Table 1. The underlined values in the aforementioned Table 1 show values outside the range of this invention.
Regenerated asphalt compositions were prepared using the asphalt binders of each of the examples of embodiment and comparative examples. The workability and flexibility of the asphalt composition at that time were evaluated.
The results are shown in Table 2. The workability of the asphalt binders shown in Table 2 was rated as 0 if there was flowability at 25 0 C and as X if there was no flowability at 25 0 C and heating was required at the time of work. Also, the flexibility of the regenerated asphalt was rated as 0 if the abrasion (cross-sectional area) was not more than 1 cm 2 using a reciprocating chain-type ravelling machine which imparts an abrading action by striking a specimen disposed on a stand with a chain to which is attached a rotating wheel, under a temperature condition of -10 0 C (see "Handbook of Methods of Testing Pavement" edited by Nihon Doro Kyokai [Japan Road
Association] , p. 517) , and as X if the abrasion (cross- sectional area) exceeded lcm 2
Table 2
As shown in Table 2, the asphalt binder of Comparative Example No. 1, which consisted of just a petroleum type solvent-extracted oil, was able to impart flexibility to the regenerated asphalt composition, but flowability was low, so that workability was poor. The asphalt binder of Comparative Example No. 2, where the blend proportions of the petroleum type solvent-extracted oil and the deasphalted asphalt were outside the range of the invention, similarly imparted flexibility to the regenerated asphalt composition but had poor workability. Further, the asphalt binder of Comparative Example No. 3,
which was a mixture of a petroleum type solvent-extracted oil and a lubricating oil, had good workability but, because the aromatic content was less than 70.0% by mass, had poor flexibility in respect of the regenerated asphalt composition.
In contrast, the asphalt binders Nos . 1 to 10, which are examples of embodiment prepared within the range of this invention, had good workability and regenerated asphalt compositions to which these were added had excellent flexibility.
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