BITUMINOUS COMPOSITION

Abstract: Bituminous composition comprising a bituminous component and a block copolymer composition which comprises at least one of the group consisting of linear triblock copolymers, multi-armed block copolymers and diblock copolymers, which block copolymers comprise at least one block of a monovinylaromatic hydrocarbon (A) and at least one block of a conjugated diene (B), wherein the block copolymer composition which is present in an amount in the range of from 1 to 10 % wt., based on total bituminous composition, has a vinyl content of at least 25 % by weight, based on the total diene content, and any diblock copolymner (AB) present has an apparent molecular weigth in the range of from 60,000 to 100,000.

Description: Bituminous Composition The present invention concerns bituminous compositions which can easily be processed and which have advantageous high and low temperature properties which are maintained over time during storage at elevated temperature, giving an improved estimated service life when used m road applications. Butadiene homopolymers with a high vinyl content (determined by infrared examination essentially the same as that set forth m "The Analysis of Natural and Synthetic Rubbers by Infrared Spectroscopy" H.L. Dmsmore and D.C. Smith in Naval Research Laboratory Report No. P-2861, August 20, 1964) are known from U.S. Patent Specification No. 3,301,840 and are preparable by utilising a hydrocarbon solvent such as tetrahydrofuran during polymerisation. U.S. Patent Specification No. 4,129,541 describes, as a comparison polymer, a block co-polymer which has a vinyl content of 47° by weight (also determined by infrared (IR) techniques) which can be prepared utilising tetrahydrofuran by a process described m U.S. Patent Specification No. 3,639,521. The authors of U.S. 4,129,541 are seeking an asphalt (also known as bitumen) -containing composition which m use as a pipeline coating m the low temperature environment of off-shore pipeline installations would provide for a longer service life by improving resistance to cracking. Their findings show that at temperatures of 0°C there is generally a gradual decrease in crack time improvement as the conjugated diene level is increased, regardless of the method of polymer preparation, but that for polymers such as the high vinyl polymer A the crack time is actually decreased (i.e. worse 1 from that of compositions which contain no polymer at all. The use of high vinyl conjugated diene/monovinyl aromatic block copolymers as modifiers for rubber- modified-asphalt roofing or waterproofing materials is described in U.S. Patent Specification No. 4,530,652. Such block copolymers have a vinyl content of at least 25°, exemplified as 33, 40 and 45o, based on total diene content, and were found to improve at least one of dispersability in asphalt, viscosity (measured at 177°C), high temperature flow resistance and low temperature break resistance. It has now surprisingly been found that attractive low and high temperature properties can be achieved m a high vinyl content block copolymer modified bitumen for road applications and furthermore that such properties can be more attractively retained over time when compared with bitumen blends containing conventional block copolymers. Accordingly, the present invention provides a bituminous composition which comprises a bituminous component and a block copolymer composition comprising at least one of the group consisting of linear triblock copolymers, multi-armed block copolymers and diblock copolymers, whicπ block copolymers comprise at least one block of a conjugated diene and at least one block of a monovinylaromatic hydrocarbon, wherein the block copolymer composition which is present in an amount m the range of fro 1 to 10 _wt, based on the total bituminous composition, has a vinyl content of at least 25 by weight, based on the total diene content, and any diblock copc_ymer present has an apparent molecular weight m the range of from 60,000 to 100,000. The bituminous compositions in accordance with the present invention are of particular interest since they advantangeously αisplay a lower viscosity at hign temperature and a higher softening point when compared with bitumen blends containing conventional block copolymers . With the term "apparent molecular weight" as used throughout the specification is meant the molecular weight of a polymer, as measured with gel permeation chromatography (GPC) using poly (styrene) calibration standards (according to ASTM D 3536) . When a coupling agent is used the diblock content is suitably less than 25 %wt, preferably less than 15 wt, and more preferably less than 10 %wt . By "diblock content", there should be understood the amount of non-coupled diblock copolymer that is finally present in the prepared block copolymer composition. When the block copolymer composition is prepared via the full sequential preparation method, essentially only triblock copolymers are formed having an apparent molecular weight in the range of from 120, 000 to 200, 000. As already indicated above, the block copolymer may be either linear or radial; good results have been given by both copolymer types. The block copolymer constituents include linear triblock copolymers (ABA) , multi-armed block copolymers ( (AB) n X) and diblock copolymers (AB) , with A representing a monovmyl aromatic hydrocarbon polymer block, B representing a conjugated diene polymer block, r being an integer of 2 or higher, preferably between 2 ana 6 and X representing the residue of a coupling agent. The coupling agent may be any di- or polyfunctional coupling agent known in the art, for example, dibromoethane, silicon tetrachloride, αiethyi adipate, divmylbenzene, dimethyldichlorosilane, methyi αichlorosilane. Particularly preferred in such a preparation route is the use of non-halogen containing coupling agents, for example gamma-glycidoxypropyl- tπmethoxysilane (Epon 825), and diglycidylether of bisphenol A. The block copolymers, which are useful as modifiers in the bituminous compositions according to the present invention, may be prepared by any method known m the art including the well known full sequential polymerisation method, optionally in combination with reinitiation, and the coupling method, as illustrated m e.g. U.S. Patents Nos. 3,231,635; 3,251,905; 3,390,207; 3,598,887 and 4,219,627 and EP 0413294 A2, 0387671 Bl, 0636654 Al, WO 04/22931. The block copolymer may therefore, for example, be prepared by coupling at least two diblock copolymer molecules AB together. Techniques to enhance the vinyl content of the conjugated diene portion are well known and may involve the use of polar compounds such as ethers, amines and other Lewis bases and more in particular those selected from the group consisting of dialkylethers of glycols. Most preferred modifiers are selected from dialkyl ether of ethylene glycol containing the same or different terminal alkoxy groups and optionally oeanng an alkyl substituent on the etnylene radical, such as monoglyme, diglyme, αietnoxyethane, 1 , 2-dιethoxy-propane, l-ethoxy-2, 2- tert-outoxyethane, of which 1, 2-dιethoxypropane is most preferred. The apparent molecular weight of the diblock copolymer (AB) is m the range of from 60,000 to 100, 0C0. Suitably, said diblock copolymer molecular weight is m the range of from 65,000 to 95,000, preferably from "0,000 to 90,000, more preferably from 75, 000 to 85, 00C . The content cf monovinyl aromatic hydrocarbon of the final bloc . copolymer is suitably m the range of from 10 to 55% by weight, preferably in the range of from 20 to 45, and more preferably 25 to 40, " by weight based on the total block copolymer. Suitable monovmyl aromatic hydrocarbons include styrene, o-methylstyrene, p-methylstyrene, p-tert- butylstyrene, 2, -dιmethylstyrene, α-methylstyrene, vmylnaphthalene, vmyltoluene and vmylxylene, or mixtures thereof of which styrene being the most preferred. The total vinyl content of the block copolymer is at least 25% by weight. Suitably the vinyl content is in the range of from 30 to 80, preferably from 35 to 65' by weight, more preferably 45 to 55 by weight and most preferably from 50 to 55° by weight, especially more than 50% wt. Suitable conjugated dienes include those having from 4 to 8 carbon atoms, for example 1, 3-butadιene, 2- methyl-1, 3-butadιene (isoprene) , 2, 3-dιmethyl-l, 3- butadiene, 1, 3-pentadιene and 1, 3-hexadιene. Mixtures of such dienes may also be used. Preferred conjugated dienes are 1, 3-butadιene and isoprene, with 1,3- butadiene being the most preferred. It will be appreciated that with the term "vinyl content" actually is meant that a conjugated diene is polymerised via 1, 2-addιtιon. Although a pure "vinyl" group is formed only in the case of 1,2 addition polymerisation of 1,3 butadiene, the effects of 1,2 addition polymerisation of other conjugated dienes on the found final properties of the block copolymer and the o_ends of it with bitumen will be the same. The bituminous component present in tne b tuπnous compositions according to the present invention may be a naturally occurring bitumen or derived from a rinera. oil. Also petroleum pitches obtained by a cracking process and coal tar can be useα as the bitαrιrιo_.5 component as well as blends of various bituminous materials. Examples of suitable components include distillation or "straight-run bitumens", precipitation bitumens, e.g. propane bitumens, blown bitumens, e.g. catalytically blown bitumen, and mixtures thereof. Other suitable bituminous components include mixtures of one or more of these bitumens with extenders (fluxes) such as petroleum extracts, e.g. aromatic extracts, distillates or residues, or with oils. Suitable bituminous components (either "straight-run bitumens" or "fluxed bitumens") are those having a penetration of m the range of from 50 to 250 dmm (as measured by ASTM D 5) . Suitably, bitumens having a penetration in the range of from 60 to 170 dmm are used. Both compatible as well as incompatible bitumens may be used. The polymer modifier is present in the bituminous composition in an amount in the range of from 1 to 10% by weight, more preferably of from 2 to 8 by weight, based on total citummous composition. The bituminous composition may also, optionally, contain other ingredients such as may be required for the end-use envisaged. Of course, if advantageous, other polymer modifiers may also be included in the bituminous composition of the invention. The improved properties of the polymer-bitumen blends of the present invention, in terms of a low high-temperature viscosity and improved properties retention upon prolonged storage at elevated temperature, er.aoles such blends to be of significant oenefit in roaα application use. Thus, trie present invention furtner relates to the use of the present bituminous composition in an asphalt mixture for road applications. Tne low viscosity at high temperat re means that asp..a__t mixtures can be proαuceα, ap _..e _ and compacted at lower temperatures than with binders based on bitumens and conventional block copolymers falling outside the scope of the present invention. The following Examples illustrate the present invention. Example 1 A first block copolymer of the invention (polymer 1) was prepared by the following full sequential polymerisation process: 90 g styrene was added to 6 litres of cyclohexane at 50°C, after which 5.65 mmol of sec-butyl lithium was added. The reaction was completed after 40 minutes. Hereafter, 1.46 mL diethoxypropane was added, followed by the addition of 400 g of butadiene in 10 minutes. The temperature of the reaction mixture rose to 60°C. The polymerisation was allowed to proceed at this temperature for 85 minutes. Hereafter the second portion of 90 g styrene is added in 1 minute. The polymerisation is allowed to proceed at 60°C for 15 minutes before 0.5 mL of ethanol is added to terminate the polymerisation. After cooling down the reaction mixture, 0.6- IONOL by weight on polymer was added for stabilisation. The product was isolated by steam stripping to give white crumbs. Details of the polymer are given in Table 1. Example 2 A second block copolymer of the invention (polymer 21 was prepared by the following process: 180 g styrene was added to 6 litres of cylohexane at 50°C, after which 11.25 mmol of sec-butyl lithium was added. The reaction was completed after 10 minutes. Hereafter, 1.46 mL diethoxypropane was added, followed by the addition cf 400 g of butadiene in 10 minutes. The temperature cf the reaction mixtrue rose to 60°C. The polymerisation was allowed to proceed at this temperature for 85 minutes. At this point in the polymerisation a sample is taken from the reaction and analysed by GPC ASTM D 3536. Then the coupling agent (gamma-glycidoxy-propyltrimethoxy silane) was added. The molar amount of coupling agent added, is 0.25 times that of the mmols of sec-butyl lithium for polymer. The reaction mixture was allowed to stand for 30 minutes at 60°C. After cooling down the reaction mixture, 0.6% by weight of IONOL on polymer was added for stabilisation. The product was isolated by steam stripping to give white crumbs. Details of the polymer are given in Table 1, together with those of the commercially available polymer Kraton D1101CS (polymer 3) which have been included for reasons of comparison. Example 3 A blend of 7% by weight of polymer in bitumen was prepared for each of polymers 1 to 3 by the following procedure m which a Silverson L4R high shear mixer was used: The bitumen was heated to 160°C and subsequently the polymer was added. During polymer addition the temperature increased to 180°C, wnich is caused by the energy input of tne mixer. At 180°C the temperature was Kept constant by on/off switching of the high shear mixer. Blending was continued until a homogeneous biend was obtained which was monitored by fluorescence microscopy. Generally the blenαmg time was around 60 minutes . The bitumen grade used for this example is a compatible bitumen, designated PX-100 and naving a penetration of 1C0 dmm (as measured by ASTM I' 5, . The polymer-citumen blends were then tested for suitability for road applications. The evaluatio s fcr botn cold temperature and nigh temperature perrcrmance initially and after 6, 24, 48 ana " ftours aqe_ιu time for the polymer blends are given m Table 1 to 3 respectively. The test methods used were: Viscosity : evaluated at 120°C, 150°C and 180°C using a Haa .e rotovisco eter . Softening point (Ring and Ball) according to ASTM D 36 Penetrating according to ASTM D 5. Elastic recovery as described in the German TLmOB (1992, . Fraass test according to IP 80. From Tables 2 to 4 it can clearly be seen that for bituminous comoositions m accordance with the present mventic: Taoies _: ana the softenina point and elastic recoveries are oetter retained than for a bituminous composition containing a polymer (Table 4) , but failing outside the scope of the present invention, indicating a better polymer stability. The initial viscosities cf the bituminous compositions according to the present invention are lower, whilst the softening points are higher than with the bitumen containing the conventicnal block copolymer. TABLE 1 Ke: Re ■ ΠD^C ir.rrare; SDΘ! :e..er::=ll αescrioed in ASTM 3 __ Ke: AΞTI-. I Ξ53ό as αetected cy W aosorption Re: . .re wei ~ - ratio cf amount cf material formed r- rreser.t :e:cre coupling Ref 5. Product available under tradename KRATON D IIOICS: a Imearily coupled triblock copolymer with the MW parameters listed in Table 1. 304 - 11 - TABLE 4 D1101 0 6 24 48 72 hours hours hours hours hours (*) Ductility failure after 12 cm elongation (74% recovery ) n.a. not analysed

Claims: C L A I M S 1. Bituminous composition comprising a bituminous component and a block copolymer composition which comprises at least one of the group consisting of linear triblock copolymers, multi-armed block 5 copolymers and diblock copolymers, which block copolymers comprise at least one block of a monovinylaromatic hydrocarbon (A) and at least one block of a conjugated diene (B) , wherein the block copolymer composition which is present in an amount in 0 the range of from 1 to 10 % by weight, based on the total bituminous composition, has a vinyl content of at least 25 by weight, based on the total diene content, and any diblock copolymer (AB) present has an apparent molecular weight in the range of from 60, 000 to 5 100,000. 2. A bituminous composition as claimed in claim 1, wherein the block copolymer has a vmyi content in the range of from 35 to 65° by weight. 3. A bituminous composition as claimed in claim 2, () wherein tne block copolymer has a vmyi content in the range of from 45 to 55r by weight. . A bituminous composition as claimed in any one of claims 1 to 3, wnerem the diblock copolymer has an apparent molecular weight m the range of from 65,000 5 to 95, 000. 5. A bituminous composition as claimed in claim 4, wnerem the diolock copolymer has an apparent molecular weight tne range of from 70,000 to 90,000. 6. A bituminous composition as claimed m any one of 0 claims 1-5 having a diblock content of 25wt or less. 7. A method of improving the service life cf a Ditummous composition modified witn an elastomer whicr comprises utilising as the elastomer a block copolymer as claimed in any one of claims 1-6. 8. Use of a bitumen composition as claimed in any one of claims 1-6 m an asphalt mixture for road applications .

Inventors: KORENSTRA JAN, VAN WESTRENEN JEROEN, VONK WILLEM CORNELIS, KORENSTRA, JAN, VAN WESTRENEN, JEROEN, VONK, WILLEM, CORNELIS
Applicants: SHELL INT RESEARCH, SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1996
Main classification: C08L95
IPC codes: C08L25, C08L53, C08L95