The present invention relates to an asphalt composition, especially an asphalt composition suitable for use in road applications, and a process for preparing such an asphalt composition. It is known, for instance from US 5,306,750, to include polymers in asphalt compositions for use in road applications in order to increase performance over a broad temperature range. This means that the asphalt composition will not be too soft and malleable at high temperatures or too brittle at low temperatures.

In US 5,306,750 asphalt compositions have been described which comprise an asphalt and an epoxy- functionalised polymer.

Surprisingly, it has now been found that improved asphalt compositions can be provided when such asphalt compositions contain in addition a small amount of a polyamine.

Accordingly, the present invention provides an asphalt composition comprising an asphalt, an epoxy- functionalised polymer and a polyamine.

A wide variety of asphalts can be utilised in accordance with the present invention. Suitable asphalts include those described in for example U.S. Patent No. 5,306,750 column 1, which is hereby incorporated by reference. In most cases, asphalt is a bottom product remaining after distillation of the crude oil. In another type of asphalt lighter fractions or less severely distilled bottoms are mixed with a deeply flashed bottom material, to arrive at an asphalt having a desired viscosity or other desired parameters depending on the planned end usage of the asphalt. It is also known to obtain desired asphalt

properties by adding aromatic-containing by-products of lubrication oil production. All of the above-disclosed base asphalts are known in the art. Suitably, the asphalts are obtained by straight-run distillation/flashing of asphaltic crude oils.

Suitably, the asphalts have a penetration of less than 120 dmm, preferably less than 100 dmm (as measured with ASTM D 5 at 25°C) .

The epoxy-functionalised polymer to be used in accordance with the present invention are suitably those derived from two or more monomers such as ethylene,alkyl (meth) acrylates, isoprene, styrene, and butadiene, and are described in detail in U.S. Patent No. 5,306,750. The preferred epoxy-functionalised polymers comprise glycidyl-functionalised polymers.

Suitably, the epoxy-functionalised polymer is present in an amount of from 0.5 to 3 %wt, preferably from 1 to 2 %wt, based on total asphalt composition.

Suitable polyamines to be used in accordance with the present invention contain 1 to 10 nitrogen atoms having at least one amine group. Preferably, the polyamine has at least two primary amine groups. In addition the polyamine may comprise one or more secondary amine sites. Preferably, the polyamine contains 2 to 10 nitrogen atoms, more preferably 4 to 10 nitrogen atoms. If less than 0.05 %wt issued, then there is usually no benefit in enhancing compatibility and if more than 2 %wt is used, then the composition will usually be too viscous to process. Thus, the polyamine is suitably present in an amount of from 0.05 to 2 %wt, preferably of from 0.1 to 0.5 %wt, based on total asphalt composition. It is theorised that the amine reacts with the epoxy groups on the polymer, thereby linking polymers together and making the polymer network more stable. Alternatively, the polyamine reacts with the epoxy-functionalised polymer

and asphalt constituents thereby making the asphalt composition more compatible.

The polyamines can be alkyl or aryl amines. Suitable polyamines include aromatic amines such as p- phenylenedia ine, 2,4-diaminotoluene, methylenedianiline, and aliphatic amines such as ethylene-diamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine. Aliphatic amines are preferred because they are more reactive.

As will be clear from the above, the present asphalt composition is a highly crosslinked asphalt composition.

The polyamines to be used in accordance with the present invention are not polymers since they only have a low number of repeating units, e.g., about six for a typical ethylene-polyamine. Thus, the molecular weights of the polyamines are relatively low compared to molecular weights of the polymers, since polymers may have 50,100, or more repeating units and molecular weights in the thousands or tens or hundreds of thousands.

The molecular weight of the polyamine is suitable such that the boiling point of the polyamine is above that of the temperature of the mixture during reaction, for example for ethylene polyamines, the molecular weight is preferably at least 140 at reaction temperatures of 200°C. Typically, ethylene polyamine have weight average molecular weights of from 60 to 500. Preferred molecular weight ranges as used in this method are from 130 to 300.

The present invention also relates to a process for preparing the present asphalt composition which comprises mixing at an elevated temperature a polyamine and an asphalt mixture which comprises an asphalt and an epoxy-functionalised polymer.

The temperature at which the polyamine and first asphalt mixture are mixed vary depending on the source of the asphalt and the polymer. The temperature should be high enough to ensure adequate mixing without being high enough to cause loss of product. Suitably, the process is carried out at a temperature in the range from 100°C to 250°C, preferably, in the range from 150°C to 230°C.

The epoxy-functionalised polymer can suitably be mixed with the asphalt at conditions as described in U.S. Patent No. 5,306,750, columns 5-8, which is therefore hereby also incorporated by reference in respect of the mixing conditions.

Suitably, the epoxy-functionalised polymer and the asphalt are mixed at a temperature in the range from 100°C to 250°c, preferably of from 150°C to 230°C.

A beneficial result of the process and the composition of the present invention is that less polymer is needed. This is valuable since the polymer greatly increases the production cost. In the process and composition of this invention the weight ratio of polymer to polyamine is suitably from 1 to 20. Preferably the ratio is from 2 to 10, and more preferably from 4 to 7. Another benefit of the invention is increased performance grade (PG) levels without increasing the polymer content. For example the asphalt composition may have a PG level of at least PG70 or PG76. As known in the art, PG levels are specified by AASHTO MP1 as results from AASHTO TP5. In this respect reference is made to Performance Asphalt Binder Specification and Testing, Superpave Series No. 1 (SP-1), The Asphalt Institute. The increased PG levels represent increased temperature range stability or performance. While the PG levels are specifically mentioned, the invention is equally applicable to other standard grade level

measurement methods which reflect increased temperature range stability, such as penetration and viscosity grading.

The invention will now be illustrated by means of the following Examples. Example 1 (comparative)

In experiments 1, 2 and 4 asphalt compositions were prepared which are not in accordance with the present invention, since they do not contain a polyamine. Asphalt A, an asphalt prepared from a crude oil vacuum distillation residue and a softer oil fraction, graded as AC-20 (AASHTO M226-80 (1986), table 2) or PG64-22 (AASHTO MPl), was used as base for modification with a glycidyl-functionalised polymer. 200 grams of Asphalt A were heated to 190°C while stirring under a nitrogen blanket and the glycidyl functionalised polymer (ELVALOY AM, Du Pont) was blended in at this temperature.

Polymer was added at concentrations of 1.0 and 2.0% on weight basis in experiments 2 and 4 respectively, whereas experiment 1 was carried out without the glycidyl-functionalised polymer. The asphalt/polymer blends were stirred for 4 hours at 190°C under nitrogen. After this treatment the blends were nitrogen blanked and stored in closed containers at 163°C for 24 hours. The results for the high temperature property G*/sinσ (AASHTO TP5) at various test temperatures are given in the table, for experiments 1, 2 and 4. Comparison of these data with those obtained from samples which were stored for more prolonged periods (up to 28 days) showed that the 24 hour storage period was sufficient to complete the polymer/asphalt reaction. Example 2

In experiments 3 and 5 asphalt compositions were prepared in accordance with the present invention.

In these experiments, 200 grams of Asphalt A were heated to 190°C whilst stirring under a nitrogen blanket and the glycidyl functionalised polymer (ELVALOY AM, Du Pont) was blended in at this temperature. Polymer concentrations were 1.0 and 2% on weight basis in experiments 3 and 5 respectively. After the polymer was completely dissolved (typically after 1 hour) , TriEthyleneTetraAMine (TETA) was added to the asphalt/polymer blend at a concentration of 20% on polymer content.

After homogenising, the asphalt/polymer/TETA blends were nitrogen blanketed and stored in closed containers for 24 hours at 163°C. The results for GVsinσ are given in the table, for experiments 3 and 5. The Table shows the beneficial results of the present invention. First, it shows that considerably less polymer can be used to obtain an increased PG level of PG70 when also a polyamine is added to the asphalt. (See experiment 3 versus experiment 4) . The results also show that for a fixed amount of polymer the addition of a polyamine can increase the PG level more than the addition of polymer alone. In this respect reference is made to experiment 2 versus experiment 3 and experiment 4 versus experiment 5. In experiment 4 an addition of 2.0% polymer increased the base case from PG64 to PG70. In comparison, in experiment 5, the addition of polyamine increased the grade level from PG70 to PG76, when compared with experiment 4.