GB2394194A

GB2394194A - Pipe coating

Info

Publication number: GB2394194A
Application number: GB0323981A
Authority: GB
Inventors: Evert Alan Mulder
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 2002-10-14
Filing date: 2003-10-13
Publication date: 2004-04-21
Also published as: GB0323981D0

Abstract

The present invention provides a pipe coating which comprises a bitumen composition comprising in the range of from 20 to 98 % by weight of a petroleum bitumen, in the range of from 0.5 to 30 % by weight of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene, and in the range of from 0.5 to 30% by weight of an asphaltite or a lake asphalt, all weights based on total bitumen composition, a process for preparing coated pipes, and the use of a bitumen composition as a pipe coating.

Description

1- 2394194

Pipe Coating The present invention relates to a pipe coating, a process for preparing coated pipes, and the use of a bitumen composition as a pipe coating.

Backaround of the Invention

j Pipelines are efficient means for the transportation of gaseous, liquid and slurried materials over long or short distances with minimum impact on the environment.

Long and large diameter pipelines are usually made from carbon steel, an iron based material that is subject to 10 corrosion. The corrosion process is a naturally occurring one in which the iron reverts to its oxide through the effects of water and oxygen from the air.

This process affects nearly all iron structures, above ground, below ground and in water. Structures which are 15 accessible and above ground may be maintained by regular painting or by some other form of coating. Pipelines are, however, rarely accessible and must be protected from their environment for the whole of their service life by a suitable corrosion resistant coating. One 20 commonly used means of corrosion protection is the use of a thick bituminous enamel coating optionally reinforced with a glass fibre or polyester wrap and optionally coated with a concrete coating for mechanical protection As further insurance against corrosion such a high 25 integrity coating can further be supported by the use of cathodic protection.

Pipe coatings can further have an advantageous insulating effect.

Whilst bitumen is in many respects naturally 30 suitable for use in pipe coating, it is inherently

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deficient in some physical properties that it would be desirable to improve.

Bitumen to be used in pipe coating must meet a stringent set of requirements. Of particular importance 5 is that the coating is very hard as pipes are susceptible to accidental damage when in transit, when being laid or when in use. In this regard, it is important that a bitumen composition for use as a pipe coating retains a good level of performance at high temperature, as 10 pipelines are often required to carry hot materials.

Also, it is advantageous if a pipe coating has good flexibility as pipes are often subjected to a degree of bending when being laid.

Efforts have been made to modify the properties of 15 bitumen by addition of polymers. For example, styrenic block copolymers, such as styrenebutadiene-styrene and styrene-isoprene-styrene block copolymers have been used in bituminous pipe coating, in particular to improve low temperature properties. However, the block copolymers are 20 sometimes incompatible with bitumen resulting in non homogeneous mixtures.

Incompatibility is most common with harder grades of bitumen and this has limited the use of styrenic block copolymers in pipe coatings, especially in pipe coatings 25 for high temperature applications, as it can be difficult to acquire consistently hard base bitumen suitable for such formulations.

Polyolefin additives may be used to increase the hardness of bitumen, and it is possible to adjust the 30 hardness of a bituminous pipe coating by incorporating an appropriate amount of a polyolefin into the composition.

In this way the amount of base bitumen available for use in bituminous pipe coatings, in particular compositions comprising styrenic block copolymers, may be increased.

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However the use of polyolefin additives is not without drawbacks. As well as representing an additional expense, there is a limit to the hardness that can be achieved through addition of polyolefins. Furthermore, 5 the use of polyolefin additives can have a detrimental effect on a compositions viscosity and /or its adherence to a pipe or base layer.

Therefore, it would be advantageous if there was a means to adjust the hardness of a bituminous pipe coating 10 which does not require the use of polyolefin additives.

Asphaltite is the group name for a class of naturally occurring resinous hydrocarbon. Asphaltites are formed in the same manner as oil and coal, i. e. from vegetation that as been subjected to high temperature and 15 pressure below the surface of the earth. They are principally mined for use in inks or as a wood coating.

It is known to use asphaltite in paving material.

For example, US 9621108 describes gilsonite-asphalt emulsions that comprise a base stock consisting of a 20 blend of gilsonite, asphalt, and a rubber latex. The emulsion component is said to be useful as a chip seal composition whilst the base stock is useful as paving material. US 5023282 describes asphalt cement wherein ailsonite is used in combination with a reactive oil; the 25 gilsonite being used to prevent highway rutting which can occur when oil is used to reduce the viscosity of rubberized asphalt. The asphalt compositions described are all typical paving asphalt having a penetration of at least 65 dam.

30 Lake asphalt is a form of natural asphalt found in well defined surface deposits. It is a very hard material, generally being used in 50/50 blends with 200 penetration grade bitumen, the mixture having a penetration of about 50 dmm at 25 C. Such mixtures are

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used in hot rolled asphalt formulations for road applications, the mix composition being adjusted to allow for the mineral matter contained in the lake asphalt.

Summary of the Invention

5 It has now surprisingly been found that the hardness of pipe coatings comprising petroleum bitumen and styrenic block copolymers may be improved by incorporating an asphaltite or a lake asphalt into the composition.

Moreover, it has been found that such compositions retain 10 their hardness at elevated temperature better than polyolefin-containing compositions.

Accordingly, the present invention provides a pipe coating which comprises a bitumen composition comprising in the range of from 20 to 98 % by weight of a petroleum 15 bitumen, in the range of from 0.5 to 30 % by weight of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene, and in the range of from 0.5 to 30% by weight of an asphaltite or a lake asphalt, all weights based on total bitumen composition.

20 Detailed Description of the Invention

The bitumen composition on which the pipe coating of the present invention is based comprises in the range of from 20 to 98 %, preferably 30 to 90 %, more preferably 0 to 80%, even more preferably 50 to 70% and most preferably 25 55 to 60 % by weight of a petroleum bitumen, based on total bitumen composition.

Petroleum bitumen is bitumen that has been manufactured from crude oil. Petroleum bitumen consists predominately of hydrocarbon molecules but may also 30 contain minor amounts of heterocyclic species and functional groups containing sulphur, nitrogen and oxygen atoms, and trace quantities of metals such as vanadium, nickel and iron which occur in the form of inorganic salts and oxides or in porphyrins structures. As will be

( - 5 - understood by those skilled in the art, the precise composition of a petroleum bitumen will vary according to the source of the crude oil from which it originated and the refinery processes by which it was produced.

5 Petroleum bitumen is distinct from naturally occurring materials such as lake asphalt or rock asphalt which are a mixture of mineral matter and/or organic matter, and a bitumen-like binder.

Examples of petroleum bitumen that may be employed 10 in the present invention include distillation or straight' run bitumen, precipitation bitumen e.g. propane bitumen, and air-blown or oxidised bitumen. The petroleum bitumen of the present invention may also comprise extenders such as petroleum extracts. Preferred bitumen 15 according to the present invention are distillation bitumen and propane bitumen, propane bitumen being particularly preferred.

Preferably, the petroleum bitumen of the present invention has a penetration of less than 50 dmm (measured 20 according to BS 2000: Part 49 at 25 C), more preferably of less than 30 dmm, and even more preferably less than 20 dmm. Preferably the petroleum bitumen will have a penetration of at least 2 dmm. In a preferred embodiment of the present invention, the petroleum bitumen has a 25 penetration in the range of from 5 to 15 dmm.

The bitumen composition on which the pipe coating of the present invention is based preferably comprises in the range of from 2 to 12 % by weight of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene, more 30 preferably from to 10 %, even more preferably from 6 to 10 % and most preferably from 7 to 9%, all weights based on total amount of bitumen composition.

The block copolymers of the present invention preferably comprise at least two terminal poly(monovinyl

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aromatic hydrocarbon) blocks and at least one central poly(conjugated diene) block, forming a continuous network. The block copolymers for use in the present 5 invention may be linear or radial and preferably have the structure A-B-A or (A-B)nY, with n being an integer of from 2 to 100, preferably 2 to 20, more preferably 2 to 6 and Y being the residue of a coupling agent; wherein A is a poly(monovinyl aromatic hydrocarbon) block and B is a 10 poly(conjugated diene) block, which may optionally have been hydrogenated.

Linear block copolymers which may be utilized in the present invention may be represented by the following general formula: 15 AZ-(B-A)y-Bx wherein: A is a block of vinyl aromatic hydrocarbons i B is a block of conjugated dienesi x and z are, independently, O or l; and 20 y is an integer ranging from 1 to about 15.

Radial polymers which may be utilised in this invention may be represented by the following general formula: [BX-(A-B)yAz]nC; and 25 [Bx- (A-B)y-Az]n -c-[B,]n wherein A, B. x, y and z are as previously defined; n is a number from 3 to 30; C is the core of the radial polymer formed with a 30 polyfunctional coupling agent; B' is a block of conjugated dienes which B' may be the same or different from Bi and

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n' and n" are integers representing the number of each type of arm and the sum of A' and A" will be from 3 to 30 The molecular weights of linear polymers or S unassembled linear segments of polymers such as mono-, di triblock, etc., arms of radial polymers before coupling are conveniently measured by Gel Permeation Chromatography (GPC), where the GPC system has been appropriately calibrated with polystyrene standards of known molecular 10 weight (ASTM 3536).

It is preferred that the A blocks have an apparent weight average molecular weight of from 3000 and 70,000 each while the block B preferably each have an apparent weight average molecular weight of from 10,000 and l5 300,000. It is more preferred that the A blocks each I have an apparent weight average molecular weight of from 5,000 and 50,000, and each B block has an apparent weight average molecular weight of from 15, 000 and 200,000. It is most preferred that the A blocks each have an apparent 20 weight average molecular weight of from 7,000 and 30,000, and each B block has an apparent weight average molecular weight of from 45, 000 and 120,000.

Blocks A and B may be either homopolymer, random or tapered copolymer blocks as long as each block is 25 predominantly the class of the monomer characterizing the block. For example, the block copolymer may contain A blocks which are styrene/alpha-methylstyrene copolymer blocks or styrene/butadiene random or tapered copolymer blocks as long as the blocks individually predominate in 30 vinyl aromatic hydrocarbons. The blocks A are preferably monovinyl monocyclic arenes such as styrene and alpha methylstyrene, and styrene is particularly preferred.

By predominantly being the class of the monomer characterizing the block, it is meant that more than 75%

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by weight of the A blocks are vinyl aromatic monomer units, and more than 75% by weight of the B blocks are conjugated diene monomer units.

The blocks B may comprise homopolymers of conjugated 5 diene monomers, copolymers of two or more conjugated dienes, and copolymers of one or more of the dienes with a vinyl aromatic hydrocarbon as long as the blocks B are predominantly conjugated diene units. The conjugated | dienes preferably contain in the range of from 4 to 8 10 carbon atoms. Examples of such suitable conjugated diene monomers include: 1,3- butadiene (butadiene), 2-methyl 1,3-butadiene(isoprene), 2,3-dimethyl-1,3butadiene, 1,3 pentadiene(piperylene) and 1,3-hexadiene; preferred conjugated diene monomers being butadiene and isoprene. I 15 In a further embodiment, the blocks B may comprise a copolymer of a diene and ethylene, for example a copolymer of butadiene and ethylene or isoprene and ethylene. The vinyl aromatic hydrocarbon blocks, e.g., 20 polystyrene blocks, preferably comprise in the range of from 5 to 50% by weight of the total block copolymer, more preferably comprise from 25 to 35% by weight of the total block copolymer and most preferably comprise from 28 to 32% by weight of the total block copolymer.

25 The block copolymers for use in the present invention can be prepared using anionic initiators or polymerization catalysts. Such polymers may be prepared using bulk, solution or emulsion techniques.

In general, when solution anionic techniques are 30 used, copolymers of conjugated diene and vinyl aromatic hydrocarbons are prepared by contacting the monomer or monomers to be polymerized simultaneously or sequentially with an anionic polymerization initiator such as group IA metals, their alkyls, amides, silanolates, napthalides,

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b phenyls or anthracenyl derivatives. It is preferred to use an organcalkali metal (such as sodium or potassium) compound in a suitable solvent at a temperature in the range of from -150 C to 300 C, preferably at a temperature 5 in the range of from 0 C to 100 C. Particularly effective anionic polymerization initiators are organolithium compounds having the general formula: RLin wherein R is an aliphatic, cycloaliphatic, aromatic or lO alkyl-substituted aromatic hydrocarbon radical having in the range of from 1 to 20 carbon atoms and n is an integer of 1 to 4.

The block copolymers may be produced by any well known block polymerization or copolymerization procedure 15 including the well-known sequential addition of monomer techniques, incremental addition of monomer technique or coupling technique. As is well known in the block copolymer art, tapered copolymer blocks can be incorporated in the multiblock copolymer by copolymerizing 20 a mixture of conjugated diene and vinyl aromatic hydrocarbon monomers utilizing the difference in their copolymerization reactivity rates.

In a preferred embodiment of the present invention, the conjugated diene block of the block copolymer of a 25 vinyl aromatic hydrocarbon and a conjugated diene is hydrogenated. Such hydrogenated block copolymers are preferred as compositions according to the invention comprising hydrognetacd block copolymers are less susceptible to degradation when heated to high 30 temperature, as is often required when applying a bitumen composition as a pipe coating.

The block copolymers may conveniently be hydrogenated by a variety of well established processes including hydrogenation in the presence of such catalysts

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as Raney Nickel, noble metals such as platinum, and palladium and soluble transition metal catalysts.

Titanium biscyclopentadienyl catalysts may also be used.

Suitable hydrogenation processes which can be used are 5 ones wherein the diene-containing polymer or copolymer is dissolved in an inert hydrocarbon diluent such as cyclohexane and hydrogenated by reaction with hydrogen in the presence of a soluble hydrogenation catalyst. Such processes are e.g. disclosed in U.S. Patent Nos. 10 3,113,986, and 9,226, 952. The polymers are typically hydrogenated in such a manner as to produce hydrogenated block copolymers having a residual unsaturation content in the polydiene block of less than 20%, preferably less than 10%, more preferably less than 5% and most preferably as 15 close to zero percent as possible, of their original ethylenic unsaturation content prior to hydrogenation.

Preferred block copolymers to be employed in the present invention are linear block copolymers having an apparent molecular weight value in the range of from 20 60,000 to 250,000, more preferably of from 80,000 to 200, 000, even more preferably of from 90,000 to 150,000 and most preferably of from 100,000 to 125,000.

Block copolymers which may very conveniently be employed in the present invention are styrene-butadiene 25 styrene block copolymers and styreneisoprene-styrene block copolymers, wherein the diene block of the block copolymer has been hydrogenated, with styrene-butadiene styrene block copolymers being particularly preferred.

A further type of block copolymer that may be 30 preferably employed in the bitumen compositions of the present invention is a styrene-ethylenebutadiene-styrene block copolymer, wherein the conjugated diene block is a copolymer of ethylene and butadiene; it will be recognized by those skilled in the art that after hydrogenation of

the ethylene-butadiene mid-klock, this type of polymer will closely resemble a styrene-butadiene-styrene block copolymer wherein the diene block has been hydrogenated.

A particularly preferred bitumen composition 5 according to the present invention is a composition wherein the block copolymer is a styrenebutadiene styrene block copolymer or a styrene-ethylene-butadiene styrene block copolymer.

Examples of preferred block copolymers are available 10 from Kraton B.V. under the designation "Kraton G" (Kraton is a trademark), for example Kraton G-1650 and Kraton G 1654. The bitumen composition on which the pipe coatings of the present invention is based preferably comprises in 15 the range of from 0.5 to 10 %, more preferably 0.5 to 5 %, even more preferably 1 to 3 by weight of an asphaltite or a lake asphalt. In the bitumen composition of the present invention, the asphaltite or lake asphalt component may be a mixture of an asphaltite and a lake 20 asphalt. In a preferred embodiment of the present invention the asphaltite or lake asphalt component comprises solely asphaltite.

Asphaltite is the group name for a class of compound which comprises albertite, anthraxalite, grahamite, 2: impsonite, libollite, nigrite and uintaite. Asphaltites are resinous hydrocarbon materials and are classified according to their softening point. Where the pipe coatings of the present invention comprise an asphaltite, it is preferred that the asphaltite has a softening point 30 in the range of from 140 to 220 C, more preferably of from 150 to 216 C, and most preferably of from 160 to 182 C (measured according to ASTM E 28-92).

Preferably the asphaltite is selected from the group consisting of uintaite and grahamite, uintaite being

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particularly preferred. Cintaite is an asphaltite from the Linta Basin, Utah, USA, and is sometimes referred to as gilson te. Uintaite is obtainable from the American Gilsonite Company, under the trade name GILSONITE.

5 Lake asphalt is a form of asphalt found in well defined surface deposits. Examples of lake asphalt include Trinidad lake asphalt and Bermudez lake asphalt from Venezuela. Other lake asphalts that may conveniently be used in accordance with the present invention are lake 10 asphalts of Iranian origin.

The pipe coating of the present invention displays a good level of performance without the need for any polyolefin to be incorporated into the bitumen composition. Accordingly, a preferred bitumen composition 15 for use in the present invention comprises less than l by weight of a polyolefin additive, more preferably less than 0.1%, even more preferably less than 0.01 %, based on total weight of bitumen composition. Most preferably, the bitumen compositions of the present invention do not 20 contain any polyolefin additive.

The bitumen composition of the present invention may be prepared according to conventional methods well known to those skilled in the art. Conveniently, petroleum bitumen may be heated to a temperature of from 150 C to 25 200 C, preferably 160 to 190 C, and then the block copolymer and asphaltite and/or lake bitumen mixed into the composition using a high shear mixer.

Whilst the bitumen composition used in the pipe coating of the present invention may contain other 30 components such as filler etc. it is an advantageous feature of the present invention that the combination of petroleum bitumen, block copolymer and asphaltite and/or lake asphalt alone has the necessary hardness for use as a pipe coating, and that it remain hard when exposed to high

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temperature conditions. Accordingly, it is preferred that once mixed the combination of petroleum bitumen, block copolymer and asphaltite and/or lake asphalt of the present invention will have a penetration at 25 C of less j than 15 dam, more preferably less than 10 dmm and most preferably of from 1 to 5 dmm; and a penetration at 50 C of less than 30 dam, more preferably less than 25 dam, and most preferably of from 5 to 20 dmm (as measured by BS 2000: Part 49).

I0 The bitumen composition used in the pipe coating of the present invention may additionally contain up to 50%, preferably in the range of from 1 to 50%, more preferably from 15 to 40%, most preferably 25 to 35% by weight of one or more fillers. For the purposes of the present I 15 application the filler is considered to be part of the bitumen composition. Fillers are inert and substantially non-hydroscopic materials. Fillers which may be used are for example, glass fibre, slate powder, talc, and rock flour. Other components including resins, stabilizers or 20 flame retardants may be incorporated. Other polymer modifiers may also be included in the bitumen composition of the invention.

Preferably, filler is added to the bitumen composition after the block copolymer and asphaltite 25 and/or lake asphalt have been have been mixed into the composition. For the avoidance of doubt, and as will be readily understood by those skilled in the art, in the bitumen composition of the present invention the total amount of 30 petroleum bitumen, block copolymer, asphaltite or lake bitumen, and optionally filler, will not exceed 100 %wt of the total bitumen composition.

The bitumen composition used in the pipe coatings of the present invention show good high temperature

- 14 performance, preferably having a softening point of at least 120 C (measured according to AS 2000: Part 58), more preferably at least 140 C.

The pipe coatings according to the present invention S may be used for coating pipe of any type of material, such as for instance, iron, steel, and other metals and alloys, as well as concrete.

Examples of materials where the pipe coatings according to the invention can be used are steel pipes to JO be used as pipelines for oil, gas and water.

The present invention further provides a process for preparing a coated pipe, which process comprises coating a pipe in a pipe coating according to the invention.

According to this process, the pipe coating may be 15 applied directly to the pipe or optionally to a pipe precoated with a primer.

A conventional method of coating pipes starts with priming with a primer followed by application of the bitumen enamel (composition), while optionally one or 20 more layers of wrapping material are applied simultaneously to the liquid enamel. The method can be terminated by application of an additional layer of wrapping material. For pipes to be used offshore, a final concrete coating is generally applied for 25 protection of the pipe and for counter-acting buoyancy, especially when said pipe is empty. The present invention further provides a pipe coated with a pipe coating according to the present invention.

The present invention still further provides for 30 the use of a bitumen composition comprising in the range of from 20 to 98 % by weight of a petroleum bitumen, in the range of from 0.5 to 30 % by weight of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene, and in the range of from 0.5 to 30% by

- 15 weight of an asphaltite or a lake asphalt, all weights based on total bitumen composition, as a pipe coating.

Bitumen compositions described hereinbefore as being preferred with respect to the pipe coating of the present 5 invention are similarly preferred with respect to said use of a bitumen composition as a pipe coating.

The invention will be further understood from the following illustrative examples. In the examples the various additives are designated as follows: 10 "Kraton G 1650" is a hydrogenated styrene-ethylene butadiene- styrene linear block copolymer having an apparent molecular weight of 109, 000, and a polystyrene content of 30 % wt. Kraton G 1650 was obtained from Kraton B.V. (Kraton is a trade mark).

15 "IPO" is a high molecular weight isotactic polyolefin ethylene/propylene copolymer having a specific gravity of 0.89 g/cm3,(ISO 1183/A); a flexural modulus of 80 MPa (ISO 178), a Vitcat softening point of 55 C (9.81N; ISO 306/A50); and a melt flow rate of 8 g/lOmin 20 (230 C, 2.16 KG; ISO 1133); obtained from Montell Polyolefins, UK under the designation Adflex X 101 H (Adflex is a trade name).

"Uintaite" is an asphaltite from the Uinta Basin, Utah, USA, having a softening point of 160 to 182 C; 25 obtained from the American Gilsonite Company under the designation 'GILSONITE HMA' (Gilsonite is trade name).

Example 1

A bitumen composition according to the present invention was prepared as follows. A propane bitumen 30 having a penetration of 10 dram at 25 C (BS 2000: Part 99) and a softening point of approximately 50 C, (BS 2000: Part 58), was heated to temperature of 165 C and a block copol\rmer was then added to the bitumen. The bitumen and block copolymer were mixed, the uinitate added, and

- 16 mixing continued until a homogenous blend was obtained.

The temperature during mixing was not allowed to exceed 185 C. After high shear mixing, the composition was heated to 180 C in a low shear mixer and slate dust 5 filler added and mixed with the blend for approximately half an hour.

Comparative Example A A comparative example was prepared in the same manner as the composition of Example 1, except that a lO polyolefin was added in place of the uinitate, and the base bitumen was a propane bitumen having a penetration of 14 dram at 25 C (BS 2000: Part 49) and a softening point of approxiimately 50 C (BS 2000: Part 58) The contents of the bitumen composition of Example 1 15 and comparative Example A, and their penetration at a temperature of 25 C and 50 C, are shown in Table 1.

From Table 1 it can be seen that the bitumen composition of Example 1 has a penetration at 25 C of 2 dam (8 dmm harder than that of the base bitumen) whilst 20 the composition of comparative Example A has a penetration at 25 C of 8 dmm (4 dram harder than the base bitumen).

Further, it can be seen that at a temperature of 50 C the bitumen composition of Example 1 retains its strength far better than that of comparative Example A; the penetration 25 of the composition of Example 1 increasing by just 16 dmm on heating to 50 C, compared with an increase in penetration of 28 dmm when the composition of comparative Example A was heated to 50 C.

Accordingly, it has been shown that the present 30 invention provides a means to adjust the hardness of a bituminous pipe coating which does not require the use of polyolefin additives, and that the pipe coatings of the invention are less temperature susceptible than comparative compositions containing polyolefin additives.

This is particularly advantageous as it means that pipe coatings containing the composition of the present invention will retain their strength at elevated temperature, for example when the pipe is used to carry 5 hot material.

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Claims

I - 19 C L A I M S

1. A pipe coating which comprises a bitumen composition comprising in the range of from 20 to 98 % by weight of a petroleum bitumen, in the range of from 0.5 to 30 % by weight of a block copolymer of a vinyl aromatic 5 hydrocarbon and a conjugated diene, and in the range of from 0.5 to 30% by weight of an asphaltite or a lake asphalt, all weights based on total bitumen composition.

2. A pipe coating according to claim 1, wherein the bitumen composition comprises in the range of from 40 to ]0 80 % by weight of a petroleum bitumen, in the range of from 2 to 12 % by weight of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene, and in the range of from 0.5 to 5% by weight an asphaltite or a lake asphalt. 15

3. A pipe coating according to claim 1 or claim 2, wherein the bitumen composition further comprises from 1 to 50% by weight of a filler.

9. A pipe coating according to any one of claims 1 to 3, wherein the asphaltite is selected from the group 20 consisting of uintaite and grahamite.

5. A pipe coating according to any one of claims 1 to 4, wherein the bitumen composition comprises an asphaltite having a softening point in the range of from 140 to 220 C.

25

6. A pipe coating according to any one of claims 1 to 5, wherein the block copolymer comprises at least two terminal poly(monovinylaromatic hydrocarbon) blocks and at least one central polyconjugated diene) block.

7. A pipe coating according to any one of claims 1 to 6, wherein the diene block of the block copolymer is hydrogenated.

8. A pipe coated with a pipe coating as claimed in any S one of claims 1 to 7.

9. A process for preparing a coated pipe, comprising coating a pipe in a pipe coating according to any one of claims 1 to 7.

10. Use of a bitumen composition comprising in the range ]0 of from 20 to 98 % by weight of a petroleum bitumen, in the range of from 0.5 to 30 % by weight of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene, and in the range of from 0.5 to 30% by weight of an asphaltite or a lake asphalt, all weights 15 based on total bitumen composition, as a pipe coating.

TS 92 81GB. DS4 7