GB1563440A - Bitumen compositions and process for their preparation - Google Patents

Abstract

In these mixtures of bitumen and filler-containing atactic polyolefins, fillers having a specific surface area of at least 1 m<2>/g and a maximum particle size of 30 mu m are employed in an amount of 5-25 % by weight of the filler-containing atactic polyolefins. The fillers, such as chalk, zinc white, limestone powder, magnesium carbonate, etc., are suspended in the polyolefins. To prepare the bitumen mixture, the filler-containing polyolefin is introduced into hot bitumen. The mixtures prepared in this way are stable and separation does not occur even on standing for an extended period in the melt-liquid state.

Description

(54) BITUMEN COMPOSITIONS AND PROCESS FOR THEIR PREPARATION (71) We, VEBA-CHEMIE AKTIENGESELLSCHAFT, a German Body Corporate of 4660 Gelsenkirchen-Buer, Pawikerstrasse 30, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to bitumen compositions and a process for their preparation.

In many fields of application it is desirable to alter the properties of the wellknown building material bitumen in such a way that it can stand up to the increased demands, usually as regards its stability to ageing and the temperature range of its plasticity. The addition of polymers to bitumen in order to improve the properties of the bitumen is well known. Special importance attaches to the atactic polyolefins, especially because unlike crystalline polyolefins, for example polyolefin regenerate, they can be mixed easily and without technical effort with bitumen.

In this Specification, the term "atactic polyolefins" is to be understood to mean the polymers of propylene monomer and its higher homologues which are for the most part soluble in ether, hexane or n-heptane, and also copolymers of such monomers with -olefins such as are obtained in the polymerisation of the said monomers with Ziegler-Natta type catalysts. The properties of these polymers can be varied within a wide range by the polymerisation conditions, mixing the polymers with one another and similar treatments. The ball and ring softening points of the commercial products are between 70 C and 1600C, the melt viscosity, usually measured at 1700C to 1900C, is between 500 mPa. s and a few 100,000 mPa. s Typical representative polymers possess the following properties: Atactic Polypropylene (Homopolymer) 1.A B C D 2. 6% 0 11% 5% 3. 153 C 114 C 156 C 156 C 4. 8000 mPa. s 480 mPa . s 3500 mPa . s 120000mPa.s 5. 221/10 mm 421/10 mm 151/10 mm 251/10 mm Key 1 .=Product 2.=n-heptane insolubles 3.=Ball and ring softening point 4=Melt viscosity at 190 C 5.=Penetration Atactic Polybutylene-l- (Homopolymer) Ether insolubles 0 Ball and ring softening point 1120C Melt viscosity at 190 C 10000 mPa.s Penetration 40 1/10 mm Atactid Butylene-l -propylene Copolymer Ether insolubles 1501, Ball and ring softening point 89"C Melt viscosity at 1900C 5000 mPa 5 Penetration 18 li10 mm Mixtures of atactic polyolefins with bitumen are used, forexample, as binders for road building, for jointing compounds, sealing compounds, adhesive compounds and also as sealing compounds for roofing and water-proofing felts. Of technical interest are mixtures with a content of atactic polyolefin of 3 to 50 per cent by weight, for road building one uses mainly mixture with 5 to 15 per cent by weight of polyolefin, and for roofing and sealing felts mixtures with 30 to 50 per cent by weight of polyolefin.A disadvantage of bitumen mixtures with a content of atactic polyolefins of more than 5 per cent by weight and less than 40 per cent by weight is that after they have been allowed to stand for a fairly long time when they are heated into a molten state, they tend to separate in such a way that the atactic polyolefin accumulates in the upper layers. One therefore has to maintain such mixtures homogeneous by circulating them with a pump or by agitation. However, these mixing facilities are only available in extremely few processing plant and transport vehicles. There is therefore a considerable demand for mixtures of bitumen and atactic polyolefins which do not tend to separate out under processing conditions.

Processes which prevent the separation of atactic polyolefins and bitumen have hitherto not been known. German Offenlegungsschrift No. 2,363,733 merely states that the tendency of mixtures of bitumen and polyolefin waste to separate out is reduced when a proportion of colour pigment or finely-divided mineral impurities with a particle size of less than 0.5 mm (e.g. sand, fertiliser residues) is present. Polyolefin waste is to be understood to mean foils, bottles etc., the raw material of which possesses a melt index of between 0.1 g/10 minutes and 10 g/10 minutes. However, if one adds to mixtures of 10% atactic polypropylene and 90% bitumen B 80 in the molten state crushed limestone with a maximum particle size of 0.5 mm, the tendency to separate out is not reduced but, on the contrary, is increased.A mixture of 30 per cent by weight atactic polypropylene and 70 per cent by weight of bitumen B 80 separates out suddenly on the addition of crushed limestone with a particle size of a maximum of 0.5 mm, when the filler sinks to the bottom and the atactic polypropylene accumulates on the surface. An addition of colour pigment, such as for example carbon black, as can be obtained on the market under the trade name Printex 60, to the mixture of atactic polypropylene and bitumen B 80 also does not reduce the tendency to separate out. The reason why one observes a completely different behaviour with atactic polyolefin than with the regenerated polyolefins of German Offenlegungsschrift No. 2,363,733 is certainly to be found in the different character of the polymers.In German Offenlegungsschrift No. 2,363,733 the term regenerated polyolefins is to be understood to mean high-molecular products. From the data regarding melt index given in the Offenlegungsschrift one can assume molecular weights of 70,000 to 200.000 for polyethylene and 200,000 to 700,000 for polypropylene. The atactic polyolefins used for mixing with bitumen, on the other hand, possess on an average molecular weights of only 30,000 to 60,000. One may therefore count on a very different behavior already on the basis of the different molecular weights.

German Offenlegungsschrift No. 2,363,733 further states that the tendency of regenerated polyolefin to separate out even if fillers and/or pigments are present, is still too great for practical purposes and must be improved by adding printing aids.

Contrary to this, we have found that stable mixtures of atactic polyolefins and bitumens can also be produced without printing aids if certain fillers are present in the atactic polyolefin.

Accordingly, the present invention provides a composition comprising 9s to sO per cent by weight of distilled bitumen and 5 to 50 per cent by weight of a mixture of atactic polyolefins and a filler having a specific surface area of at least 1 m2/g, the amount of filler being 5 to 25 per cent by weight of the total weight of the polyolefins and the filler.

It is advantageous if the atactic polyolefin containing the filler is stirred into the hot bitumen in the form of granulate or chips.

The quantity of mineral fillers must be calculated in principle in such a way that the density of the atactic polyolefin containing filler is made to approach the density of the bitumen used. The atactic polyolefin, when present in quantities of over 5 per cent by weight, occurs in the bitumen predominantly as finely dispersed droplets, and the filler particles must therefore not exceed the maximum droplet size. This is approximately 30 microns. The fillers used according to the invention must therefore possess a particle size corresponding to a specific B.E.T. surface area of at least 1 m2/g. Fillers with a smaller surface area than this are unsuitable.

The filler must be adequately dispersed in the atactic polyolefin and in particular it must bc ensured that filler agglomerates which look like larger particle sizes are broken up. Fillers which satisfy the above mentioned conditions are, for example.

Champagne chalk prepared by wet grinding and screening, finely ground crystalline calcite filler, technically pure zinc oxide according to ISO Type 1. and also for example magnesium carbonate, magnesium oxide, carbon black and fine limestone. These fillers possess specific surface areas of 3.5 m2/g and 8 to 9 m2/g. Not suitable are coarser powdered limestones or iron oxide, which usually have specific surface areas of 0.05 m2/g and 0.6 m2/g.

It is believed that the atactic polyolefin completely encases the filler particles so that, after mixing with the bitumen. polyolefin droplets which, as a result of the "heavy core" which they possess have a density which closely approximates to that of the surrounding bitumen and there is thus no separation.

If one uses carbon black as filler, because of the very high specific surface area, obviously a different mechanism comes into effect.

The Examples given in the following Table illustrates the present invention.

Examples 1, 2 and 10 to 13 are comparative examples. In the Examples, the fillers were mixed into the atactic polyolefins in a Meili pugger at 120 to 170"C. The polyolefin containing filler was stirred into the hot bitumen in small pieces. The mixture was homogenous after about 20 minutes. For testing the tendency to separate out, the mixture was left in an atmosphere of nitrogen for 3 hours at 180 C without stirring. Then the ball and ring softening points were determined in different layers. The mixture was regarded as stable if differences were only found within the limits of experimental error.

No. 1 2 3 4 5 6 7 8 9 10 11 12 13 Atactic polypropylene 8000 mPs.s/190 C Pts 98 95 93 90 80 90 80 90 80 90 85 Atactic polybutylene-1 5000 mPa.s/190 C Pts 93 90 Fumace black specific surfaca area 119 m2/g Pts 2 5 7 7 Chalk specific surface area 3.5 m2/g Pts 10 20 ZnO zinc white Colloidal extra spec. surface area 8-9 m2/g Pts 10 20 10 Crushed limestone spec.surface area 0.05 m2/g Pts 10 20 Iron oxide spec. surfacearea 0.6 m2/g Pts 10 15 Density at 20 C of the polyolefin containing filler g/cm3 0.90 0.96 0.99 1.04 0.93 0.99 0.94 0.99 Separation, 15% into bitumen 80 after 3 hrs storage at 180 C yer yes no no no no no no no yes yes yes yes

Claims (9)

1. WHAT WE CLAIM IS: I. A stabilised bitumen composition comprising 95 to 50 per cent by weight of distilled bitumen, and 5 to 50 per cent by weight of a mixture of atactic polyolefins and a filler having a specific surface area of at least I m2/g, the amount of filler being 5 to 25 per cent by weight of the total weight of the polyolefins and the filler.
2. 2. A composition according to Claim I, wherein the filler has a specific surface area of 3.5 m2/g.
3. 3. A composition according to Claim I, wherein the filler has a specific surface area of 8 to 9 m2/g.
4. 4. A composition according to Claim I, wherein the filler is Champagne chalk, crystalline calcite, zinc oxide, magnesium carbonate, magnesium oxide, carbon black or limestone.
5. 5. A composition according to Claim 1 substantially as described in any one of Examples 3 to 9.
6. 6. Process for the production of a composition as claimed in any one of the preceding claims, which process comprises stirring the polyolefin containing the filler into hot bitumen.
7. 7. Process according to Claim 6, wherein the polyolefin containing the filler is in the form of granulate or chips.
8. 8. Process according to Claim 6 substantially as hereinbefore described in any one of Examples 3 to 9.
9. 9. A composition according to any one of Claims 1 to 5 when prepared by a process as claimed in Claim 6, 7 or 8.