BITUMINOUS COMPOSITIONS AND PREPARATION THEREOF

Abstract: A road surface dressing composition is made by (a) blending together at a temperature of 140 to 200°C, (i) a bitumen fluxed with a petroleum derived aromatic oil to a penetration of over 220 (mm 10), (ii) a styrene-butadiene copolymer; (b) mixing the resultant blend for at least 10 minutes at a temperature of 150 to 190°C with 0.01 to 0.6% of sulphur based on the weight of the bitumen content of the said fluxed bitumen; and (c) mixing the resultant product at a temperature of 125 to 150°C with a light fluxant, preferably hydrocarbonaceous, to decrease the final viscosity of the composition to a required value.

Description: BITUMINOUS COMPOSITIONS & PREPARATION THEREOF BACKGROUND OF THE INVENTION This invention relates to bituminous compositions and the preparation thereof; more especially to those which include styrenebutadiene copolymers. Particularly, but not exclusively, the compositions are suitable as binder compositions for road surface coating or dressing and hot mixes. Other applications may include immersion coating, roof waterproofing and joint filler/sealant. The term bitumen is used herein substantially coterminously with the term asphalt to include appropriate natural materials and also petroleum derived materials. In a road the surface dressing is the uppermost layer which is exposed to traffic, and generally comprises a layer of binder (consisting of or incorporating bitumen) in which chippings are embedded. This technique is used in the construction of a new pavement and also in the maintenance of old pavements. Such dressings are applied by first depositing a thin layer of binder on the existing worn surface course, and then scattering the chippings and rolling the surface. For some applications a "single" operation involving application of binder followed by application of chippings is employed, whereas sometimes a "double operation technique is used. In this the binder composition is applied to the road surface, followed by large-sized chippings; thereafter further binder composition is applied followed by smaller-sized chippings. The binder is in liquid form when applied, and subsequently solidifies at ambient temperature to form, with the chippings, a hard surface dressing which will take the force of moving vehicles without undue wear or deformation. Conventionally the binder layer is applied as a liquid by one of several techniques, each of which is employed to apply the binder at acceptable viscosity to the road surface. Thus, the hot spray method employs heat and optionally a fluxant to reduce the viscosity of the binder; typically application temperatures of 140-C and above are used. The cut-back method employ 6 a relatively high proportion of low boiling point fluxant, e.g. about 15%, to reduce viscosity and application is at a temperature of about 80-100'C. A more recent technique is that where the bituminous binder is applied to the surface to be treated at relatively low or even ambient temperature in the form of a low viscosity emulsion with water (e.g. 30-80%) and option ally a fluxant. The quality of surface dressings required depends on the nature of the road to which they are applied. Thus road surfaces which are subject to high stresses, such as at roundabouts, require very strong binders, and hitherto expensive binder composi tions comprising epoxy compounds and bitumen have been used.- Somewhat less durable binders are required for road surfaces which simply have steep cambers, and hitherto bitumen modified with rubbers such as styrenebutadiene-styrene (SBS) block copolymers has been used. Both of these high quality binder compositions are used in relatively small volumes, and have relatively high cost. Conventional "normal quality" binders which are used for the major proportion of road surfaces, and hence in large volumes, have hitherto generally comprised bitumen alone, although in some cases the binder has also included an aliphatic solvent such as kerosene to facilitate handling and application to the road base surface. Some conventional "normal quality" surface dressing binder compositions have also included SBS in admixture with the bitumen, although these have had to be chemically reacted to improve compatibility of the rubber with the bitumen. Furthermore, various EVA's have been used in combination with bitumen in road surface uses, but again, except for special grades, these have suffered from a degree of incompatibility with the bitumen. Problems encountered with road surface dressings are generally associated with a reduction of expected lifetime, primarily due to the nature of the traffic passing over the road. Heavy traffic is very detri mental to surface dressings. Typically, dressing lifetime is reduced because of indentation of the surface layer; because of ageing of the binder; and because chippings are pulled out of the binder. This latter problem arises if the binder becomes brittle at low temperature, or lacks cohesion at high temperature, or shows a lack of adhesion to the chippings or to the base road surface. A desideratum is, therefore, a binder composition which exhibits high cohesion at high temperature, resistance to low temperatures, and high stiffness. Further, it is desirable that materials used to modify the bitumen used in such binders be readily miscible, i.e. compatible with the bitumen and with any solvents or fluxants which may also be incorporated. PRIOR ART It is known to improve bituminous binding agents by the incorporation therein of: (I) natural or crepe rubbers [(1) GB-A-460854]; (I1) synthetic elastomers or rubbery copolymers t(2- GB-A 1304238; (3) GB-A-1385006; (4) GB-A-1324599; (5) GB A-1324600; (6) GB-A-915445; (7) GB-A-1130385 and (8) GB-A-1440474]; (III) copolymers, in particular, styrene-butadiene copolymers [(9) GB-A-1548541; (10) GB-B-2038848, (11) GB-B-2025986, (12) EP-2023 B1, (13) EP.96638 Al, (14) Fr-A-2360630 and (15) (;B-A-1330425J. In order to initiate or enhance the reaction (which term is used broadly and includes grafting) between the bitumen and rubber/elastomer/copolymer, sulphur is frequently employed. References (1), (9) to (12) and (15) disclose processes in which sulphur is essential, and references (2) to (5) and (8) in which it is optional. Furthermore, whether or not sulphur is employed, it is known to assist the mixing of the bitumen and the rubber/elastomer/copolymer by employing specific solvent oil or flux oils. This is disclosed in above references (1) to (3), (6) to (8) and (11) to (13) where such use is essential; and references (4), (5) and (14) where it is optional, but normally preferred. The improvement obtained in the prior art processes is generally some increase in softening temperature (ring and ball) compared with a bitumen of the same penetration but not containing the polymer. Sometimes the brittleness temperature (Fraass point) is also decreased. Almost always the elastomeric properties of the binding agent are improved. SUMMARY OF THE INVENTION It is an object of the present invention to provide a bituminous binder, and process for the manufacture thereof, having improved softening temperatures and brittleness temperatures. In one aspect the invention provides a bituminous -- binder composition for use in surface dressing of roads, comprising an aromatic oil fluxed bitumen of penetration over 220 (mum/10), modified with a styrene butadiene copolymer and further containing a light aliphatic hydrocarbons solvent and/or a light aromatic hydrocarbons solvent. In another aspect the invention provides a process for preparing a bitumen/styrene-butadiene copolymer composition, comprising the steps of: (a) blending together at 8 temperature of 140 to 2000C1 (i) a bitumen fluxed with a petroleum derived aromatic oil to a penetration of over 220 (mm/10), (ii) a styrene-butadiene copolymer; (b) mixing the resultant blend for at least 10 minutes at a temperature of 150 to 1900C with 0.01 to 0.6 of sulphur based on the weight of the (unfluxed) bitumen employed; and (c) mixing the resultant material at a temperature of 125 to 150 C with a light fluxant to decrease the final viscosity of the composition to a required value. GENERAL DESCRIPTION Preferably the bitumen of the fluxed bitumen employed in the initial blending step (a) of the process of the invention is a low penetration bitumen in the range 25 to 70, especially 35 to 60, preferably 40 to 50 (mm/10 ASTM standard method). A mixture of two or more such bitumens may be used. A suitable petroleum derived aromatic oil fluxant for fluxing such bitumen(s) to a penetration above 220 has a kinematic viscosity of at least 900 cSt at 40"C, preferably at least 1000. Generally, the flash point of the aromatic oil fluxant is at least 2000 C, preferably 230 to 250 C, as measured by the ASTM D 92 method. Suitable boiling ranges would lie within the broad overall range of minimum 3000 C, or minimum 3300 C, maximum 6000C. The fluxed bitumen employed in the blending step (a) with the styrene-butadiene copolymer preferably has a penetration (mm/10) of at least 300, normally at least 350; suitably in the range 350 to 500, preferably 375 to 425. The styrene-butadiene copolymer employed in the blending step (a) with the fluxed bitumen is suitably from 1 to 10e by weight, based on the amount of bitumen employed (that is to say, the bitumen content of the fluxed bitumen). A preferred range i8 2 to 8 ó. The styrene-butediene copolymer may be a block; disequenced; multisequenced; or a statistical copolymer. Number average molecular weight ranges for such polymers are suitably from at least 30,00Q. An upper limit of 380,000 is generally suitable. From 50,000 to 380,000 is generally preferred, with from 75,000 to 350,000 being more preferred. Commercially available products include those sold under the trade names Solprene, Cariflex and Finaprene. The temperature employed in blending step (a) is from 140 to 2000C, more suitably 160 to 1800C. Normally, the blending step will be continued for from 30 min to 2 hours, generally about 1 hour being suitable. The mixing step (b) is continued for at least 10 min, suitably 15 to 60 min, preferably 25 to 35 min. The temperature will be in the range 150 to 1900C, suitably 160 to 1800C. The amount of sulphur employed normally lies in the range 0.005 to lE.OZ, preferably up to 5.do, based on weight of the copolymer. Normally, too, the sulphur range is 0.01 to 0.3v based on the weight of the unfluxed bitumen employed in step (a); suitably the amount used is from 0.03 to 0.2X, more preferably 0.04 to 0.1v; By "sulphur" is meant sulphur which is not chemically combined or chemically bonded. Thus, flowers of sulphur is one suitable material. The resultant product from step (b) is mixed with e light fluxant at a temperature in the range 125 to 1500. Suitable light fluxents include light aromatic hydrocarbon solvents, light aliphatic hydrocarbon solvents, or a mixture of these. Suitable such fluxants may have a distillation range lying within the broad range ISO to 3300C; for example, 175 to 3200C or 230 to 2650C. Such fluxants are commercially available. The amount of the light fluxant employed will depend,upon the final viscosity it is desired to achieve. It may be found that 10 to 15 wt. ¯ (based upon the total weight of composition including light fluxant) is suitable to provide a road surface dressing composition. Other uses, such as roof sealants may require more or less than that. DESCRIPTION OF PREFERRED i'BODIMENTS The invention will now be illustrated, in a non-limitative manner, by the following Example: Exampl Six formulations in accordance with the invention were prepared The materials, and proportions thereof, employed are indicated in Table 1 below. Formulation III was prepared on a pilot plant scale. Quantities are qiven as parts by weight. The method of preparation employed in each case was as follows: 76 parts of the 40/50 bitumen were blended with 24 parts of an aromatic oil fluxant having a boiling range 320 to 5800C. The resultant blend had a penetration of about 400 (mm/10). Referring to Formulation I as an example, 84.4 parts of the said resultant blend were taken and mixed with 4 parts of the SBS copolymer at 1700C for 1 hour under stirring. As another example, in Formulation V, 86.5 parts blend were mixed with 1.5 parts of the SBS copolymer under the same conditions. The styrene-butadiene copolymer employed was a block copolymer, 70:3D butadiene:styrene, having a number average molecular weight of approximately 300,000. The sulphur was then added, the mixture being stirred at 170 C for 30 minutes. After this reaction/chemical modification period the mixture was cooled to 1400C and the light solvent added under a nitrogen stream. The light solvents used were commercially available aromatic or aliphatic solvents, having boiling ranges within the general limits 2200C and 300 C. TABLE 1 EMI10.1 <tb> <SEP> 40/50 <SEP> Aromatic <SEP> SBS <SEP> S <SEP> Light <SEP> Light <tb> <SEP> Fluxuant <SEP> Copolymer <SEP> Aromatic <SEP> Aliphatic <tb> <SEP> Formulation <SEP> Copolymer <SEP> Solvent <SEP> Solvent <tb> <SEP> Bitumen <tb> (mm/10) <tb> <SEP> - <SEP> 84.4 <SEP> parts <SEP> <tb> <SEP> I <SEP> (64.17) <SEP> (20.27) <SEP> 4 <SEP> 0.04 <SEP> 12 <SEP> <tb> <SEP> - <SEP> 84.4 <SEP> parts <SEP> <tb> <SEP> II <SEP> (64.17) <SEP> (20.27) <SEP> 4 <SEP> 0.04 <SEP> - <SEP> 12 <tb> <SEP> - <SEP> 84.0 <SEP> parts <SEP> <tb> <SEP> III <SEP> (63.8) <SEP> (20.2) <SEP> 4 <SEP> 0.04 <SEP> - <SEP> 12 <tb> TABLE 1 (Cont'd) EMI11.1 <tb> <SEP> 40/50 <SEP> Aromat- <SEP> SBS <SEP> Light <SEP> Light <tb> <SEP> Formulation <SEP> bitumen <SEP> ic <SEP> Copolymer <SEP> S <SEP> Aromatic <SEP> Aliphatic <tb> <SEP> (mm/10) <SEP> Fluxant <SEP> Solvent <SEP> Solvent <tb> <SEP> - <SEP> 85.0 <SEP> parts <SEP> <tb> <SEP> IV <SEP> (64.6) <SEP> (20.4) <SEP> 3. <SEP> 0.03 <SEP> - <SEP> 12.0 <tb> <SEP> - <SEP> 86.5 <SEP> parts <SEP> <tb> <SEP> V <SEP> (65.7) <SEP> (20.8) <SEP> 1.5 <SEP> 0.015 <SEP> - <SEP> 12.0 <tb> <SEP> - <SEP> 86.5 <SEP> parts <SEP> <tb> VI <SEP> (65.7) <SEP> (20.8) <SEP> 1.5 <SEP> 0.075 <SEP> - <SEP> 12.0 <tb> The physical properties of the six formulations were measured by conventional techniques and the results are shown in Table 2. Also included in Table 2 are the corresponding values obtained on a commercially available bitumen/styrene butadiene copolymer surface dressing product. The product is known as "STYRELF" and includes about 5% of copolymer. It is a product of Elf France. The properties of the six formulations of the present invention, and of the known product, were also measured after a curing test. The test involved curing a 1 mm film of each in a ventilated oven at 50 C for 15 days. The results of the curing test are also shown in Table 2. It will be seen from Table 2 that the products of the invention have a surprisingly good combination of high R & B, low Fraass point and suitable penetration. This is especially so with the product III which was made on a pilot plant scale. The high ring and ball softening temperatures and low Franks point endow the products of the invention with a very large workability temperature range, being as much as 1150C in formulation III. Table 3 shows the results of VI ALIT adhesivity tests on blend III. This test is described, for example, in an article by M. Brossel in "Bulletin de Liaison des Laboratoires des Ponts et Chaussees", No.4 November-December 1963; or in "Avant Projet du Mode Operatoire du Laboratoire Central des Ponts et Chaussees, Paris", March 1973. As can be seen from the Table, the adhesivity - stone adhesion - was 100 < even under the most severe test conditions (5 C). TABLE 2 EMI13.1 <tb> 1111 <SEP> III <SEP> STYRELP <tb> <SEP> Viscosity <SEP> lOOoc <SEP> 909 <SEP> 997.6879.11235.8 <tb> <SEP> (cyst) <SEP> 120 <SEP> C <SEP> 386 <SEP> 391.2 <SEP> 472.9 <SEP> <tb> <SEP> 0 <tb> <SEP> 140 <SEP> o"e <SEP> 240 <SEP> 232.7 <SEP> 265.4 <SEP> 190.1 <tb> <SEP> u <SEP> 16 <SEP> OOC <SEP> 135 <SEP> 136.2 <SEP> 153.0 <SEP> 96.3 <tb> <SEP> W <SEP> R & <SEP> Point <SEP> Point <SEP> C) <SEP> i <SEP> 45.2 <SEP> 55w6 <SEP> 6q.o <SEP> 29.0 <tb> <SEP> o <tb> <SEP> o <SEP> Penetration <tb> <SEP> (lOOg/5s <SEP> ooC <SEP> 150 <tb> <SEP> mn/lo) <SEP> 10 <SEP> C <SEP> > 250 <tb> <SEP> R & <SEP> Softening <SEP> Point <SEP> ( <SEP> C) <SEP> 78.4 <SEP> 82.8 <SEP> 88.5 <SEP> 57 <tb> <SEP> Penetration <tb> <SEP> .IQOgjSs <SEP> 250C <SEP> 106 <SEP> 113 <SEP> 1152 <SEP> 83 <tb> <SEP> z <SEP> mn/lO) <tb> <SEP> Fraass <SEP> Point <SEP> ( <SEP> C) <SEP> -21 <SEP> -22 <SEP> < -27 <SEP> -20 <tb> <SEP> u <tb> <SEP> Tensile <SEP> Curve <tb> <SEP> <SEP> (-lO & <SEP> lO <SEP> mm/min} <SEP> 2 <SEP> 7¯3xlO <SEP> 6¯8xlD <SEP> 2.8xlD <SEP> > <SEP> 4xlO <SEP> <tb> <SEP> N <SEP> (-10 <SEP> C, <SEP> 10 <SEP> zirn/inin) <SEP> 2 <SEP> 7-.3x10 <SEP> 68x10 <SEP> Stress <SEP> ? <SEP> N/m <SEP> <tb> <SEP> Break <SEP> point <SEP> Break <SEP> point <tb> <SEP> o <SEP> , <tb> Belong, <SEP> 380 <SEP> 380 <SEP> > 320 <SEP> > 460 <SEP> 40O <tb> TABLE 2 (Cont'd) EMI14.1 <tb> <SEP> IV <SEP> V <SEP> VI <tb> BEFORE <SEP> CURING <tb> Viscosity <SEP> 100 C <SEP> 857.5 <SEP> 314.3 <SEP> 418.7 <tb> <SEP> 120 C <SEP> 318.2 <SEP> 153.0 <SEP> 195.2 <tb> (cSt) <SEP> 140 C <SEP> 168.5 <SEP> 78.0 <SEP> 103.1 <tb> <SEP> 160 C <SEP> 99.1 <SEP> 41.5 <SEP> 60.0 <tb> R <SEP> & B <SEP> Softening <SEP> Point <SEP> ( C) <SEP> 37.6 <SEP> < 20. <SEP> 27.1 <tb> Penetration <SEP> 0 C <SEP> 224 <SEP> > 290 <SEP> 283 <tb> (100 <SEP> g/5 <SEP> a <SEP> 10 C <SEP> - <SEP> - <SEP> <tb> <SEP> mm/10) <tb> <SEP> AFTER <SEP> CURING <tb> <SEP> R <SEP> & B <SEP> SOftening <SEP> Point <SEP> ( C) <SEP> 82.5 <SEP> 42.1 <SEP> 55.5 <tb> Penetration <SEP> 25 C <SEP> 107 <SEP> 155 <SEP> 165 <tb> (100 <SEP> g/5 <SEP> 5 <SEP> 1 <SEP> 107 <SEP> 155 <SEP> I <SEP> 165 <SEP> 1 <tb> mm/10) <tb> Fraass <SEP> Point <SEP> ( C) <SEP> -17 <SEP> -15 <SEP> -18 <tb> <SEP> Tensile <SEP> Curve <tb> <SEP> (-10 C, <SEP> 100 <SEP> mm/min) <tb> Stress <SEP> N/mê <SEP> 5.3x105 <SEP> 1.6x106 <SEP> 5.0x105 <tb> <SEP> Break <SEP> Point <tb> Break <SEP> Point <SEP> I <SEP> I <SEP> 93 <tb> <SEP> Elongation <SEP> % <SEP> 148 <SEP> 31 <SEP> 93 <tb> TABLE 3 VIALIT ADHESIVITY ON BLEND III EMI15.1 STORAGE <SEP> TEMPERATURE <SEP> 5 C <tb> IMPACT <SEP> AT <SEP> 5 C <tb> GRAVELLING TEMPERATURE STORAGE TIME ADHESIVITY EMI15.2 20 <SEP> MIN <SEP> 100 <SEP> % <tb> 5 <SEP> #2 <SEP> H <SEP> 100 <SEP> % <tb> 5 <SEP> H <SEP> 100 <SEP> % <tb> 15 C 2 H 100 % 25 C 2 H 100 %

Claims: CLAIMS: 1. A process for preparing a bitumen/styrene-butadiene copolymer composition, comprising the steps of: (a) blending together st a temperature of 140 to 200DC, (i) a bitumen fluxed with a petroleum derived aromatic oil to a penetration of over 220 (mum/10), (ii) a styrene-butadiene copolymer; (b) mixing the resultant blend for at least 10 minutes at a temperature of 150 to 1900C with 0.01 to 0.6dud of sulphur based on the weight of the bitumen content of the said fluxed bitumen; and (c) mixing the resultant product at a temperature of 125 to 150 C with a light fluxant to decrease the final viscosity of the composition to a required value. 2. A process as claimed in claim 1, wherein the bitumen employed in step (a) has a penetration range of 40 to 50 before fluxed with said aromatic oil. 3. A process as claimed in claim 1 or claim 2, wherein the petroleum-derived aromatic oil has a kinematic viscosity of at least 1000 cSt at 400C. 4. A process as claimed in any preceding claim, wherein the penetration of the fluxed bitumen in step (a) is at least 350, preferably 375 to 425. 5. A process as claimed in any preceding claim, wherein the styrene-butadiene copolymer has a number average molecular weight of over 30,000; preferably 75,000 to 350,000. 6. A process as claimed in any preceding claim, wherein from 0.01 to 0.3dud of sulphur is employed. 7. A process as claimed in any preceding claim, wherein the light fluxant employed in step (c) comprises a light aliphatic hydrocarbon solvent or a light aromatic hydrocarbon solvent or mixture thereof, 8. A bitumen/styrene-butadiene copolymer composition whenever prepared by a process claimed in any preceding claim. 9. A bituminous binder composition for use in surface dressing of roads, comprising an aromatic oil fluxed bitumen of penetration over 220 (mm/10), modified with a styrene butadiene copolymer and sulphur and further containing a light aliphatic hydrocarbons solvent and/or a light aromatic hydrocarbons solvent. 10. The use of a composition claimed in claim 8 or claim 9 in the surface dressing of roads.

Inventors: PLAINDOUX, MARC
Applicants: ESSO SOCIETE ANONYME FRANCAISE
Application year: 1985
Main classification: C08L95
IPC codes: C08L101, C08L95, C08L25, C08L77, C08L51, C08L21, C08L9, C08L7, C08L23