The present invention relates to bitumen compositions, their preparation, and their use in bitumen emulsions for road applications, e.g. surface dressings. Bitumens used for these applications may have different origins. Venezuelan crude oils that naturally contain acidic molecules (naphthenic acids) are considered as having good qualities for manufacturing bitumen emulsions. Crude oils from other sources, e.g. Middle East oils, do not contain these acids. However, it is known to add (and incorporate) naphthenic acids to non-naphthenic bitumens in order to try to attain the quality of naphthenic bitumens.

EP-A-0416682 discloses bitumen compositions comprising bitumen and at least one polymerised fatty acid contained in the bitumen and their use in bitumen emulsions for surface dressing applications suitable for roads.

It has now been found that bitumen compositions having surprisingly enhanced properties can be obtained by incorporating a particular succinic anhydride derivative into bitumens.

According to the present invention there is provided a bitumen composition comprising bitumen and a succinic anhydride derivative incorporated in the bitumen, wherein the derivative comprises a mono-alkene on to which has been grafted a succinic anhydride function.

Preferred mono-alkenes are those having a chain length of 12 to 40 carbon atoms, particularly 1-alkenes. Particularly preferred are the 1-alkenes having a chain length of 14 to 19 carbon atoms.

Such succinic anhydride derivatives can be obtained by any suitable known method, for example, by the processes described in US-A-3412111 or US-A-4691030. The succinic anhydride derivative is preferably present in an amount of at least 0.1% w/w of the bitumen, preferably an amount in the range of 0.1% to 1% w/w of the bitumen, more preferably an amount in the range of 0.1% to 0.5% of the bitumen. In accodance with the present invention the bitumen composition may suitably comprise two or more different types of the succinic anhydride derivative.

The present invention also provides a process for preparing a bitumen composition of the present invention which process comprises incorporating the succinic anhydride derivative into the bitumen, conveniently by mixing the succinic anhydride derivative directly into molten bitumen. The bitumen may be any bitumen, but the advantages of the present invention are most clearly attained when the bitumen is a non-nap tr.eπic bitumen, as will readily be appreciated by er : : . . . e ύ in the art.

Emulsions for road applicaticr.r, * . :. : .rlace dressings, may readily be prepare;. 1::: : .'..rcr. compositions of the invention, in KΓ. Λ . *τ.-...r.er . The present invention thus further includes the use of bitumen compositions according to the present invention in a bitumen emulsion for surface dressings suitable for road applications.

The present invention will be further understood from the following illustrative Examples, in which parts and percentages are by weight unless otherwise indicated. EXAMPLES

Various doped bitumens were prepared based on two 200 penetration bitumens, that is, industrially produced

non-naphthenic bitumens (Bitumens A and B) which were each prepared from different crude oils.

The bitumens were doped by adding agents to the molten bitumens whilst stirring until homogeneous. Emulsions containing about 65% bitumen were prepared in conventional manner from the above bitumens, by introducing bitumen (at 140°C) into a colloid mill together with an aqueous phase containing hydrochloric acid and emulsifier (N-alkyl (tallow) propylene diamine - "DINORAM S" ex. CECA, France (DNS)).

Various properties of the bitumens (adhesivity) and of the emulsions (e.g. viscosity, breaking behaviour) were measured, and the results are given in Tables 1 to 3 following, in which: R is a maleinated 1-alkene having a hydrocarbon chain length of 14 carbon atoms; S is a maleinated 1-alkene having a hydrocarbon chain length of 16 carbon atoms; T is a maleinated 1-alkene having a hydrocarbon chain length of 18 carbon atoms;

U is a blend of maleinated 1-alkenes having hydrocarbon chain lengths from 15 to 19 carbon atoms; V is a blend of maleinated 1-alkenes having hydrocarbon chain lengths from 15 to 19 carbon atoms; W is a blend of maleinated 1-alkenes, 25% having a hydrocarbon chain length of 14 carbon atoms, 50% having a hydrocarbon chain length of 16 carbon atoms and 25% having a hydrocarbon chain length of 18 carbon atoms; and C is a polymerised fatty acid ("PRIPOL 1017" ex.

Unichema International, UK) used for purposes of comparison

TABLE 1

TABLE 1 (continued)

storage stability decantation % 0.8 0.8 0.8 sedimentation 2.3 2.9 3.2 3.7

%

TABLE 2

TABLE 2 (con t i nued )

TABLE 3

In the above Tables 1 to 3 viscosity was measured in known manner using a dynamic viscometer Bohling V88 (25°C; shear rate - 150 sec ^-1 ; time - 30 min) .

Adhesivity of the bitumen and breaking rates of the emulsions were tested as follows:

1. ADHESIVITY (LCPC Method)

The purpose of this test is to assess the adhesivity, in the presence of water, of a hydrocarbon binder coated on aggregate, and in it the displacement of bitumen by water on the surface of the aggregate is measured. In the test, bitumen- coated aggregate is plunged into water while hot, and the percentage of the surface covered by the binder after 16 hours' immersion at 60°C is evaluated. The test is carried out with four types of reference aggregate, as indicated.

2. IREC break index

Reference fines (siliceous fines in the case of cationic emulsions) are poured continously through a funnel at a rate of 0.3 to 0.5 g/s into a beaker containing lOOg of emulsion. The mixture is agitated constantly, and the addition of fines halted when the aggregate-emulsion system takes on the appearance of a block. The quantity of fines added to the lOOg of bitumen emulsion is called the break index.

3. SMS 210m break index lOg of aggregate (Corbigny porphyry, 2 to 4mm) are placed in contact with an excess of emulsion (about lOg) for 1 hour in an environment saturated with water in order to prevent any evaporation. The unbroken emulsion is removed with distilled water. After drying, the quantity of bitumen deposited is determined by weighing, and the result expressed in relation to lOg of emulsion.

4. GBI (Global Breaking Index)

The results of the IREC and SMS 210 tests are combined to generate the global breaking index. This is defined by the relationship: GBI = 72.5 - 0.45 IREC + 30.2 log(SMS 210)

From the Tables, it is evident that the succinic acid derivatives significantly improved the breaking properties of the emulsions. In particular, it can be seen that the bitumen compositions of the present invention exhibit improved breaking properties when compared to the comparative compositions containing no dope (indicated in Tables 1 to 3 by "0%") and those containing "PRIPOL 1017" (indicated by "C" in Tables 1 to 3) .