AU704340B1 - Compound and bituminous compositions containing said compound - Google Patents

Description

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AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION NAME OF APPLICANT(S): Shell Internationale Research Maatschappij B.V.

ADDRESS FOR SERVICE: DAVIES COLLISON CAVE Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

INVENTION TITLE: Compound and bituminous compositions containing said compound The following statement is a full description of this invention, including the best method of performing it known to me/us:i la This invention relates to polymeric compounds for use in bituminous compositions. This invention also relates to a highly stable bituminous composition which contains bitumen and the aforementioned compound.

Bitumen is a common material utilized for the preparation of paving and roofing materials and also for "*.*coatings such as pipe coatings and tank liners. While oooo the material is suitable in many respects, it inherently I is deficient in some physical properties which it would be highly desirable to improve. Efforts have been made in this direction by addition of certain conjugated diene rubbers, ethylene containing plastics like EVA, ~and polyethylene, neoprene, amorphous polyolefins, resins, fillers and other materials for the modification of one or more of the physical properties of the bitumen. Each of these added materials modifies the bitumen in one respect or another but certain *deficiencies can be noted in all modifiers proposed.

S. For example, some of them have excellent weather resistance, sealing and bonding properties but are often deficient with respect to warm tack, modulus, hardness and other physical properties; and some of them improve only the high temperature performance of bitumen, some only improve the low temperature performance of bitumen, while some lack thermal stability or mixing stability with bitumen.

Since the late 1960s, diene polymer rubbers such as styrene-butadiene rubber and styrene-rubber block 2 copolymers such as styrene-butadiene-styrene and styrene-isoprene-styrene block copolymers have been used to dramatically improve the thermal and mechanical properties of bitumen. Practical application of the rubber addition approach requires that the blended product retain improved properties and homogeneity during transportation, storage and processing. Long term performance of elastomer-modified bitumen also depends on the ability of the blend to maintain thermal and chemical stability.

Such polymers have been found to be very advantageous but in some end uses, such as roll roofing membranes, high processing viscosity of blends of eeeo bitumen and such polymers leads to reduced manufacturing 15 rates. Other attempts at lowering the processing viscosity, such as reducing molecular weight or polymer content or adding oil, have proved to be undesirable '.'because the softening point of the composition was lowered to such an extent that adequate slump resistance could not be achieved. Also, the processing stability of blends of some of the commercially used polymers could advantageously be improved to provide a wider processing window. Hydrogenated versions of styrenic S: block copolymers provide greatly improved processing stability.

Styrenic block copolymers are widely used as bitumen modifiers for roofing and paving applications.

Since bitumen can vary significantly in its chemical composition and molecular weight distribution, bitumen modifiers must either be supplied for specific bitumens or a modifier must be found that has utility over as wide a range of bitumen properties as possible. In particular, styrenic block copolymers tend to be 3 incompatible with bitumens which have a high asphaltenes content. One compound which is compatible with such bitumens is a compounded blend of a styrenic block copolymer which is optionally hydrogenated, a naphthenic oil, and carbon black. Mixtures of three components which have not been compounded by melt processing do not provide improved compatibility. Such compounds are disclosed in U.S. Patent No. 5,036,119.

The naphthenic oil is required because of the high melt viscosity of styrenic block copolymers, especially in the presence of carbon black. Typically, compounds of :high molecular weight styrenic block copolymers require the addition of oil to avoid unacceptable degradation or melt fracture during processing. A high level of oil is 15 undesirable in applications which are highly sensitive to bleeding of the oil or where the oil causes unacceptable loss of high temperature properties.

Other polymers are currently used for bitumen modification including amorphous polyolefins, especially high molecular weight atactic polypropylene. Atactic Spolypropylene has advantages in processability and high temperature performance but requires higher addition .levels than styrenic block copolymers. Lower molecular weight amorphous polyolefins do not have the strength or elasticity of styrenic block copolymers.

It would be advantageous to produce a composition which combined the advantages of styrenic block copolymers and amorphous polyolefins and minimized their individual disadvantages. It has not been possible to create such compositions using conventional unhydrogenated styrenic block copolymers because they are incompatible with amorphous polyolefins. Blends of unhydrogenated styrenic block copolymers, amorphous 4 polyolefins, and bitumen typically exhibit unacceptably poor phase stability during processing and long term performance.

Single ply membranes are widely used in the roofing industry. They are commonly produced from EPDM, PVC, and CSPE. EPDM makes thermoset single ply membranes which require careful cleaning and adhesive application to seal the seams. PVC and CSPE make thermoplastic single ply membranes which have environmental problems because the polymers are chlorinated.

Thus it can be seen that there is a need for a styrenic block copolymer compound that is easily processable, highly compatible with bitumen, and preferably oil free to minimize bleeding and maximize high temperature properties. There is also a need for a method to compatibilize blends of unhydrogenated styrenic block copolymers and amorphous polyolefins.

There is also a need for a thermoplastic, weatherable single ply roofing membrane which has minimal 20 environmental problems. There is also a need for such a compound with enhanced weatherability. The present invention provides compounds which meet one or more, in particular all of these needs.

Therefore, the present invention relates to a compound which comprises from 20 to 90% by weight of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene having a weight average molecular weight of from 80,000 to 300,000, from 10 to 70% by weight of a low viscosity amorphous polyolefin having a viscosity of less than 100,000 cps at 190 0 C and greater than 100,000 cps at 38 0 C, and from 0.1 to 20% by weight of carbon black.

11~1111 5 The present invention further relates to a bituminous composition which comprises from 2 to 20% by weight of the above compound and from 80 to 98% by weight of a bituminous component.

The bituminous component in the bituminous-polymer compositions according to the present invention may be a naturally occurring bitumen or derived from a mineral oil. Also, petroleum derivatives obtained by a cracking process, pitch and coal tar can be used as the bituminous 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 and 5 mixtures thereof. Other suitable bituminous components include mixtures of one or more of these bitumens with extenders such as petroleum extracts, e.g. aromatic *extracts, distillates or residues, or with oils.

a: Compatible bitumens are preferred for use in the present invention. However, the present invention significantly widens the scope of bitumens which are Ccompatible with the invention styrenic block copolymer compound. Bitumens that up to now could not be used, because such bitumens were generally incompatible with the polymer component but can be used in the bituminous composition of the invention, are bitumens with high bitumenene contents, i.e. greater than 12%. Asphaltenes are known to those skilled in the art. For purposes of this application, asphaltenes make up the n-heptane insoluble fraction of bitumen. The compounds of the present invention can be used with these bitumens to produce compatible and useful bitumen compositions.

6 Polymers containing ethylenic unsaturation or both aromatic and ethylenic unsaturation may be prepared using anionic initiators or polymerization catalysts.

Such polymers may be prepared using bulk, solution or emulsion techniques. In any case, the polymer containing at least ethylenic unsaturation will, generally, be recovered as a solid such as a crumb, a powder, or a pellet, but it also may be recovered as a liquid. Polymers containing ethylenic unsaturation and polymers containing both aromatic and ethylenic unsaturation are available commercially from several suppliers.

In general, when solution anionic techniques are used, copolymers of conjugated diolefins and alkenyl 5 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, biphenyls or anthracenyl derivatives. It is preferred to use an organoalkali metal (such as sodium or potassium) compound in a suitable solvent at a temperature in the range from 150°C to 300°C, preferably at a temperature in the range from 0°C to 1000C. Particularly effective anionic polymerization initiators are organolithium compounds having the general formula: RLin wherein R is an aliphatic, cycloaliphatic, aromatic or alkyl-substituted aromatic hydrocarbon radical having from 1 to 20 carbon atoms and n is an integer of 1 to 4.

Conjugated diolefins which may be polymerized anionically include those conjugated diolefins 7 containing from 4 to 24 carbon atoms, preferably 4 to 8, such as 1,3-butadiene, isoprene, piperylene, methylpentadiene, phenyl-butadiene, 3,4-dimethyl-1,3hexadiene, and 4,5-diethyl-1,3-octadiene. Isoprene and butadiene are the preferred conjugated diene monomers for use in the present invention because of their low cost and ready availability. Alkenyl aromatic hydrocarbons which may be copolymerized include vinyl aryl compounds such as styrene, various alkylsubstituted styrenes, alkoxy-substituted styrenes, vinyl napthalene, and alkyl-substituted vinyl napthalenes.

The block copolymers may be produced by any well known block polymerization or copolymerization procedures including the well-known sequential addition 15 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 a mixture of conjugated diene and vinyl aromatic hydrocarbon monomers utilizing the difference in their copolymerization reactivity rates.

p According to one preferred embodiment, the block copolymer used in compound of the present invention is a hydrogenated block copolymer. Hydrogenated polymers are useful in circumstances wherein unhydrogenated block copolymers have as one of their principal limitations their sensitivity to oxidation. This can be minimized by hydrogenating the copolymers, especially in the diene blocks. The hydrogenation of these block copolymers may be carried out by a variety of well established processes including hydrogenation in the presence of such catalysts as Raney Nickel, noble metals such as platinum, and palladium and soluble transition metal 8 catalysts. Titanium biscyclopentadienyl catalysts may also be used. Suitable hydrogenation processes which can be used are 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. 3,113,986, 4,226,952 and Reissue 27,145. 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 close to zero percent as possible, of their original 15 ethylenic unsaturation content prior to hydrogenation.

These polymers preferably have a vinyl aromatic hydrocarbon content of 20 to 35% by weight so that they .achieve adequate properties and are sufficiently compatible with the bitumen. They should have a weight average molecular weight of from 80,000 to 300,000 g/mol. Polymers with molecular weight below 80,000 will be less efficient and polymers with molecular weight above 300,000 will be difficult to process.

The molecular weights of linear polymers or unassembled linear segments of polymers such as mono-, di-, triblock, etc., arms of star 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 weight. For anionically polymerized linear polymers, the polymer is essentially monodisperse (weight average molecular weight/number average molecular weight ratio approaches unity), and it is both 9 convenient and adequately descriptive to report the "peak" molecular weight of the narrow molecular weight distribution observed. Usually, the peak value is between the number and the weight average. The peak molecular weight is the molecular weight of the main species shown on the chromatograph. For polydisperse polymers the weight average molecular weight should be calculated from the chromatograph and used. For materials to be used in the columns of the GPC, styrenedivinyl benzene gels or silica gels are commonly used and are excellent materials. Tetrahydrofuran is an excellent solvent for polymers of the type described herein. A refractive index detector may be used. oo Measurement of the true molecular weight of the 15 final coupled radial or star polymer is not as e straightforward or as easy to make using GPC. This is because the radial or star shaped molecules do not .separate and elute through the packed GPC columns in the same manner as do the linear polymers used for the calibration, and, hence, the time of arrival at a UV or refractive index detector is not a good indicator of the molecular weight. A good method to use for a radial or star polymer is to measure the weight average molecular weight by light scattering techniques. The sample is dissolved in a suitable solvent at a concentration less than 1.0 gram of sample per 100 milliliters of solvent and filtered using a syringe and porous membrane filters of less than 0.5 prm pore size directly into the light scattering cell. The light scattering measurements are performed as a function of scattering angle and of polymer concentration using standard procedures. The differential refractive index (DRI) of the sample is measured at the same wavelength and in the same solvent used for the light scattering. The following references provide more information about molecular weight determination: 1. Modern Size-Exclusion Liquid Chromatography, W. W.

Yau, J. J. Kirkland, D. D. Bly, John Wiley Sons, New York, NY, 1979.

2. Light Scattering from Polymer Solution, M. B.

Huglin, ed., Academic Press, New York, NY, 1972.

3. W. Kaye and A. J. Havlik, Applied Optics, 12, 541 (1973).

4. M. L. McConnell, American Laboratory, 63, May, 1978.

The low viscosity amorphous polyolefin of this invention should be of sufficiently high viscosity to limit migration and bleeding and sufficiently low viscosity for facile processing. The viscosity of the amorphous polyolefin as measured on a Brookfield viscometer should be less than 100,000 cps (centipoise) at 190 0 C and greater than 100,000 cps at 38 0 C. The polyolefin should be amorphous as crystalline polyolefins will not form phase stable blends. For the purpose of this invention amorphous is defined as having a crystallinity of less than 10% as determined by small angle x-ray diffraction. Suitable polymers for this invention include polyethylene-propylene, atactic polypropylene, polyethylene-1-butene, a random copolymer of ethylene and a higher alpha olefin, and polyisobutylene.

The compound of this invention comprises from 20 to 90%, preferably 45 to 80%, by weight of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene which is optionally hydrogenated, from to 70%, preferably 15 to 40% and more preferably 10 to 40%, by weight of a low

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11 viscosity amorphous polyolefin, and from 0.1 to preferably 5 to 20%, by weight of carbon black.

Preferably, the compound contains substantially no oil, that is has an oil content of less than 2% by weight, more preferably less than 1% by weight, even more preferably less than 0.5% by weight. The styrenic block copolymer must comprise at least 20% of the compound and no more than 70% of the amorphous polyolefin or little benefit in properties over the amorphous polyolefin is realized. There must be at least 10% of the amorphous polyolefin and not more than 90% of the styrenic block copolymer or the compound cannot be easily processed by conventional melt processing techniques. The carbon black must be present in an amount of at least 0.1% or 15 little benefit for stabilization and compatibilization is realized. If more than 20% is used, then little additional benefit is seen and melt processing becomes unduly difficult. Diene optionally hydrogenated, from 10 to 70% by weight of a low viscosity amorphous polyolefin, and from 0.1 to 20% by weight of carbon black. If less than 20% of the bituminous component is used, then the bituminous composition is unduly difficult to produce by conventional techniques and if more than 98% is used, then little benefit is derived from the addition of the compound.

Free carbon black is very difficult to handle. Its fine particle size, polarity, and electrical conductivity make it a severe nuisance dust. To overcome this problem, the carbon black may be preblended with part or all of the amorphous polyolefin to form a masterbatch prior to compounding with the styrenic block copolymer. This preblending may be accomplished at a temperature where the amorphous 12 polyolefin is in a liquid state in blending equipment such as a ribbon blender, a drum mixer, or other conventional equipment.

This bituminous composition is useful for the manufacture of roll roofing membranes, waterproofing and dampproofing membranes, and elastomer modified shingles.

This bituminous composition is also useful for the manufacture of hot mix bitumen concrete. This bituminous composition is also useful for hot mopping application of roll roofing membranes and built up roofing plies provided that the incorporated styrenic block copolymer is hydrogenated.

The invention also provides a single ply roofing membrane made from the above compound provided that the incorporated styrenic block copolymer is hydrogenated.

This roofing membrane is weatherable and seams can be sealed by heat welding. It contains no halogen which i Senvironmentally desirable. Optionally the membrane may include other components commonly used in single ply roofing membranes such as bitumen, fillers, UV stabilizers, and antioxidants. This single ply roofing membrane may be prepared using conventional sheet rubber manufacturing techniques such as calendering, molding, and sheet extrusion.

P:OPER\CAE\8002-98AME 22i2/99 12A- The invention will now be further described with reference to the following examples. The examples are considered to be illustrative of the present invention. It is to be understood that the invention is not limited to the specific details of the examples.

Examples Compounds were prepared on a Banbury mixer. Oil-free Vulcan 9A32 carbon black from Cabot was premixed with E1200 amorphous polyolefin from Eastman. Two compounds were prepared: Compound 1 with Polymer 1, a hydrogenated styrene-butadiene-styrene linear block copolymer having a weight average molecular weight of 126,000 and a polystyrene content of 30 percent by weight, and Compound 2 with Polymer 2, an unhydrogenated 0 0 So @000*, 0* 9.

00*00 *0 Sf f ft**f t tf 13 styrene-butadiene-styrene radial block copolymer having a weight average molecular weight of 264,000 and a polystyrene content of 31 percent by weight. The compounds contained 50% by weight of the block copolymer, 35% by weight of the amorphous polyolefin, and 15% by weight of the carbon black. These blends were processed in the Banbury mixer until a temperature of 190 0 C was achieved (approximately three minutes).

These compounds were then used to make blends in bitumen. 600 grams of bitumen was preheated to 180 0 C in a quart can. The desired amount of compound was cut into three to five millimeter pieces and added to the hot bitumen. The blend was stirred using a Silverson L4R high shear mill rotating at 3000 revolutions per 15 minute for 45 minutes.

Blend 1 12% by weight of Compound 1 in AC20 bitumen made at Shell's Wood River, Illinois refinery.

Blend 2 12% by weight of Compound 2 in the same bitumen.

20 Blend 3 4% by weight of Compound 2 in Total Blend 4 The same as Blend 1 except the individual compound components, 6% by weight Polymer 1, 4.2% by weight of E1200, and 1.8% by weight of Vulcan 9A32 carbon black, were added directly to the bitumen without precompounding.

Blend 5 The same as Blend 2 except the individual compound components, 6% by weight Polymer 2, 4.2% by weight of E1200, and 1.8% by weight of Vulcan 9A32 carbon black, were added directly to the bitumen without precompounding.

Blend 6 16% by weight of Compound 1 in a Venezuelan bitumen.

14 Blends 1, 2, 4, and 5 were subjected to the one day can test for separation. A sample of the bituminous composition in a pint can is heated at 177 0 C for one day.

After cooling and removing the can, the hard, brittle bitumenene rich phase is separated from the soft, rubbery polymer rich phase with a hot knife. The fraction of polymer rich phase (FPR) is determined by dividing the weight of the polymer rich phase by the weights of both fractions. If there is no separation the FPR is 100%. A FPR less than 65% is poor. A standard unhydrogenated styrene-butadiene-styrene block copolymer blended in this same bitumen would have over 40% by weight separation. Blend 1 had a FPR of >95% and Blend 2 had a FPR of 100%. Blends 4 and 5 had FPR's of 15 Blend 3 was subjected to the aluminum tube separation test. A sample of the bituminous composition '9 is sealed in an aluminum tube which is held vertically in an oven at 163°C for two days. The sample is cooled and cut into thirds. The ring and ball softening point of the top and bottom thirds is determined. A difference in softening points of 2.5°C is considered good. The standard unhydrogenated polymer above in S9'* Total AC20 would have a ring and ball difference of more than 12°C. Blend 3 had a difference of only 0.5°C. The upper PG grade as determined by AASHTO MP1 of Blend 3 was 70 versus 64 for the base bitumen.

Properties were determined for Blend 6. The Brookfield viscosity at 190C was 3800 cps. The ring and ball softening point was 134°C. The 25°C penetration was 39 units. The penetration (pen) is a measure of hardness of bitumens and bitumen blends and is measured 15 by ASTM D5 at 25 0 C. This bituminous composition would be suitable for formulating a roll roofing membrane or a mopping bitumen.

Three more compounds were produced comprising percent by weight Polymer 1, 35 percent by weight of an amorphous polyolefin (APO), and 15 percent by weight of a different carbon black. The APOs used were three different grades from Eastman, EASTOFLEX E1200, P1023, and D172. The compounds were blended into Woodriver AC10 bitumen at 10.5 percent by weight. The properties are shown in the following table: APO Softening Point Pen Viscosity of Neat APO S°C 190 0 C mPa-s E1200 84 35 20,000 P1023 82 34 2300 D172 78 35 5800 The results shown in the above table indicate that utilizing amorphous polyolefins with a range of viscosities gives little effect on penetration and only a modest effect on the ring and ball softening point.

Further, very little, if any, effect on the low temperature flexibility was observed.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims (1)

16- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A compound which comprises from 20 to 90% by weight of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene having a weight average molecular weight of from 80,000 to 300,000, from 10 to 70% by weight of a low viscosity amorphous polyolefin having a viscosity of less than 100,000 cps at 190C and greater than 100,000 cps at 38°C, and from 0.1 to 20% by weight of carbon blacks. 2. A compound as in Claim 1 which comprises from 45 to 80% by weight of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene, from 15 to 40% by weight of a low viscosity amorphous polyolefin, and from 5 to 20% by weight of carbon black. 3. A compound as in Claim 1 or Claim 2 in which the conjugated diene block of the block copolymer is hydrogenated. 4. A bituminous composition which comprises from 80 to 98% by weight of a bituminous component and from 2 to 20% by weight of the compound as claimed in any of claims 1 to 2. 0 S 5. A bituminous composition which comprises from 80 to 98% by weight of a bituminous component and from 2 to 20% by weight of the compound as claimed in Claim 3. 6. A single ply roofing membrane prepared from the compound in Claim 3 or the composition in Claim 7. A compound substantially as hereinbefore described with reference to the Examples. 8. A bituminous composition substantially as hereinbefore described with reference to P:\0PER\CAE\80902-98.AME 22/2199 17 the Examples. 9. A roofing membrane substantially as hereinbefore described with reference to the Examples. DATED this TWENTY SECOND day of FEBRUARY, 1999 Shell Internationale Research Maatschappij B.V. DAVIES COLLISON CAVE Patent Attorneys for the Applicant 0@ 9 S S S. S S .55. 555* S S S. S S Si.. *S 5 S 555* SS 55 55** S S 5* 9 5S S S S 55 .SSS S S 9 S. S S S