FIELD OF INVENTION

This invention relates to a recycled composition. More particularly, this invention relates to a recycled composition for road surfaces. Still more particularly, this invention relates to a recycled product for use as a binder and odour neutral composition in a road surface formulation.

BACKGROUND ART

The following references to and descriptions of prior proposals or products are not intended to be, and are not to be construed as, statements or admissions of common general knowledge in the art. In particular, the following prior art discussion does not relate to what is commonly or well known by the person skilled in the art, but assists in the understanding of the inventive step of the present invention of which the identification of pertinent prior art proposals is but one part.

Recycled products for use in road surfaces have been described in which ground motor vehicle tyres have been deployed as a component of the road surface fonnulation. However, pungent odours that may be injurious to health or, at the least, a cause of road worker respiratory discomfort, make the use of recycled rubber problematic.

An object of the present invention is to ameliorate the aforementioned disadvantages of the prior art or to at least provide a useful alternative thereto.

STATEMENT OF INVENTION

The invention according to one or more aspects is as defined in the independent claims. Some optional and/or preferred features of the invention are defined in the dependent claims. Accordingly, in one aspect of the invention there is provided:

A liquefied rubber bitumen composition for asphalt including: particulate rubber derived from vehicle tyres; a polymer for increasing elasticity of the particulate rubber;

a carbon powder toner mix; a hardener mineral;

bitumen; and

an anti-odour agent to negate sulfurous odour, wherein the particulated rubber is liquefied by heating and mixed with the remaining constituents to form a liquefied bitumen product ready for mixing with aggregate to form asphalt.

In another aspect, the invention provides:

A liquefied rubber bitumen composition for asphalt including: particulate rubber derived from recycled vehicle tyres;

an emulsion or solution polymerised polymer for increasing elasticity of the particulate rubber; a toner mix;

calcium carbonate; bitumen; and

a plant-based oil performing as an anti-odour agent to negate sulfurous odour, wherein the particulated rubber is separated from fabric and metal tyre components, the particulated rubber is liquefied by heating and mixed with the remaining constituents to form a liquefied bitumen composition ready for mixing with aggregate to form an asphalt mix.

In still another aspect of the invention, there is provided:

A method of making a liquefied rubber bitumen composition for asphalt including the following steps:

obtaining particulate rubber from recycled tyres, including grinding the tyres and the separating the rubber component from other fabric and metal constituents of the tyre; delivering a batch of the rubber particulate component to a hopper and subsequently to a vat heated to 170 - 210°C, involving liquefying the heated rubber component; gradually adding a polymer thickener, toner powder, hydrated lime and a plant based essential oil in the heated vat; and mixing the liquefied rubber mix together with about 10001 (1250kg) of bitumen to produce the composition; and allowing the composition to cool to about 150 - 170°C.

In yet another aspect of the invention, there is provided:

A method of making a liquefied rubber bitumen composition for asphalt including the following steps: obtaining particulate rubber from recycled tyres, including grinding the tyres and the separating the rubber component from other fabric and metal constituents of the tyre; delivering a batch of the rubber particulate component to a hopper and subsequently to a vat heated to 190 - 200°C, involving liquefying the heated rubber component; gradually adding solution polymerized styrene-butadiene rubber, toner powder, hydrated lime and Geraniol oil in the heated vat; and mixing the liquefied rubber mix together with bitumen to produce the composition; and allowing the composition to cool to about 160 - 170°C.

Rubber

The rubber is preferably derived from used vehicle road tyres. The rubber is preferably separated from the other tyre components, such as fabric, wire and steel ribbon. The tyres are comminuted, ground down or otherwise particulated, and the non-rubber constituents separated out. The isolated particulated rubber material is subjected to heat to liquefy same in a hot melt. The temperature of the melt is preferably between 150 - 210°C, still more preferably between 160 - 200°C, and most preferably 190 - 200°C. Once the entire rubber-bitumen composition is completed, ready for transport to a road laying site, the composition may be permitted to cool by about 20 - 25%, maintaining a melt temperature of about 150 - 160°C, and providing an effective liquefied composition or mix ready for mixing with aggregate to form asphalt.

The percentage by weight range of the rubber as a constituent of the composition is about 10 - 20%, and preferably about 12 - 18%, depending on the properties required of the ultimate asphalt product and the particular properties of the rubber used in any instance. For example, the rubber may depend on the type and brand of tyres used as the source of rubber, and may be in the range of soft tyre rubber or harder tyre rubber. The hardness of the rubber determines the temperature required to liquefy the rubber, with a softer rabber allowing the rubber to be liquefied at a lower temperature but requiring more rubber to be used to provide the wet rubber mix required.

The rubber hardness may be measure by the standard Shore A hardness. A soft tyre rubber may have a hardness of about Shore 55 A, whereas a hard rubber tyre may have a hardness rated at Shore 70A, and tyres may have intermediate hardness of anywhere between Shore 55A - 70A.

Polymer

The polymer may be an emulsion rubber resin. The polymer may be an emulsion polymerized rubber, such as styrene-butadiene rubber. The polymer may be an acrylonitrile-butadiene rubber. The polymer is preferably a solution polymerized styrene-butadiene rubber. A suitable, commercially available polymer is Europrene sol™. The polymer improves the elasticity of the liquefied or molten particulated or crumbed rubber component. The preferred range of the polymer by weight in the composition is about 1.2 - 2%, and the particular proportion of the polymer used in each case is determined by the inherent elasticity properties of the particulated rubber used in any particular case and the requirements of the particular application, i.e. the physical properties required of the asphalt end product.

Toner

The toner is the standard fine dry mix of plastic particles and carbon used in toner cartridges for laser printers and photocopiers. The toner is preferably a powder used in laser printers and photocopiers to form the printed text and images on the paper. It is typically a mix of carbon powder and iron oxide, in which the carbon is melt-mixed with a polymer. The toner operates as a thickener [that affects the grade of asphalt. It is used to vary the grade of asphalt between classes 170, 320, 400, 600, and most preferably Classes 170 and 320. The toner may be used to thicken the mix to improve the durability and thickness for better adherence to aggregate in the ultimate asphalt product. Preferably, the toner is included in the composition in the range of 0.2 - 0.7% by weight.

Hardener

The hardener is used to vary the hardness of the composition and the ultimate asphalt product for different climatic conditions and pavement properties. Hard pavement may require a hardener component of up to 2%, e.g. in Saudi Arabian asphalt compositions where road temperatures can reach 95 - 100°C. In Russia, where road temperatures can be as low as -35 - -40°C and can rise to 75°C, a lower hardener component of 1.2% by weight is preferred. The composition may comprise calcium carbonate in the range of 1.2 - 2% by weight.

Bitumen

The composition preferably includes Class 170 or 320 residual bitumen in a proportion range of 77 - 86% by weight in the composition, and preferably in the range 77.3 - 85.4% by weight.

Anti-Odour Agent

The anti-odour agent may be a masking or neutralising agent, whereby the smell detectable by the human olfactory caused by sulphur-derived airborne fumes or particles is neutralised. Plant based essential oils capable of wetting the composition and negating the smell may be used. A particularly preferred plant-based essential oil is Geraniol oil because it is both effective to negate the sulfurous odour derived from the rubber melt and is cost effective. The proportions of the anti-odour agent in the composition may vary between 0.03 - 1.0% by weight, preferably 0.07 - 0.3%, and most preferably about 0.1% by weight, or about 11 in every 10001 of composition.

Composition

In producing the ultimate asphalt product, it is generally accepted that a product having more than 8% bitumen composition by weight results in a road surface that is too shiny and slippery and not acceptable to road authorities. However, a composition proportion that is too low (less than 7%) will generally result in unacceptable aggregate segregation. It has been found that the current composition formulation permits a lesser proportion of composition to be used because the liquefied rubber mix improves the binding performance of the composition. Accordingly, the preferred range of the composition by weight in the ultimate asphalt mix is between 6 - 7%, still more preferably 6.1 - 6.3%.

Moreover, use of the liquefied rubber component improves performance of a road surface prepared using the composition by virtually eliminating hydro-absorption of water in the asphalt mix. Whereas a typical asphalt mix may absorb 200ml of water in a 600mm core sample over a 2 week period, asphalt made using the composition of the invention results in negligible water absorption. Water absorption is considered an important deleterious factor in road surface deterioration due to the hydraulic destmctive effect of vehicle tyres compressing a road surface full of water as a vehicle passes over, thereby hydraulically causing the break-up of the asphalt layer.

Moreover, the hydrophobic nature of the composition and ultimate asphalt product has the effect of improving water run off, such that the passage of vehicles thereover causes less wheel spray.

The presence of a high proportion of rubber material in the ultimate asphalt product also reduces road noise.

EXAMPLE Preferred features of the present invention will now be described with particular reference to one or more examples. However, it is to be understood that the features illustrated in and described herein are not to be construed as limiting on the scope of the invention, except as may be recited in the claims accompanying this specification. Example 1

A test sample of liquefied rubber bitumen composition for asphalt was produced as follows. Particulate rubber was derived from recycled Bridgestone ^rM tyres having a hardness rating of Shore 70A. The tyres were ground and the rubber component separate from other fabric and metal constituents of the tyre. A 250kg batch of the rubber particulate component was delivered to a 10001 hopper and subsequently to a 10,0001 vat heated to 190 - 200°C. The heated rubber component liquefied and gradually about 201 (25kg) of Europrene sol™ , 7.5kg of toner, 25kg of hydrated lime and about 21 (2.5kg) of Geraniol oil, were added and mixed together with about 10001 (1250kg) of bitumen oil to produce a composition according to one embodiment of the invention.

The composition was then permitted to cool to 170°C and maintained at that temperature in a liquid emulsion until transferred to a 25T capacity transport mixer where it was slowly mixed with about 23,500kg of aggregate comprising a standard mix of crushed rock (granite in particle sizes of between about 7 - 20mm

(predominantly 10 - 14mm), washed and quarry sand (predominantly quarry sand), and granite and silica dust.

The resultant 25T asphalt mix was laid and set to form a road surface. Whilst laying the hot asphalt mix, the Applicant observed that no unpleasant odour was detectable.

A 600mm core sample was taken 3 weeks after installation and tested for moisture content. There was no moisture content detected in the sample.

The sample was tested for aggregate segregation and the rate was found to be 0.32% by weight.

The sample was manually observed for sulphurous odour presence and this could not be detected. Example 2

A test sample of liquefied rubber bitumen composition for asphalt was produced as follows. Particulate rubber was derived from recycled Pirelli ^{1 M} tyres having a hardness rating of Shore 60A. The tyres were ground and the rubber component separate from other fabric and metal constituents of the tyre. A 200kg batch of the rubber particulate component was delivered to a 10001 hopper and subsequently to a 10,0001 vat heated to 190 - 200°C. The heated rubber component liquefied and gradually about 161 (20kg) of Europrene sol™ , 10kg of toner, 30kg of hydrated lime and about 11 (1.25kg) of Geraniol oil, were added and mixed together with about 9001 (1110kg) of bitumen oil to produce a composition according to another embodiment of the invention.

The composition was then permitted to cool to 160°C and maintained at that temperature in a liquid emulsion until transferred to a 25T capacity transport mixer where it was slowly mixed with about 23,500kg of aggregate comprising a standard mix of crushed rock (granite in particle sizes of between about 7 - 20mm

(predominantly 10 - 14mm), washed and quarry sand (predominantly quarry sand), and granite and silica dust.

The resultant 25T asphalt mix was laid and set to form a road surface. Whilst laying the hot asphalt mix, the Applicant observed that no unpleasant odour was detectable. A 600mm core sample was taken 3 weeks after installation and tested for moisture content. There was no moisture content detected in the sample.

The sample was tested for aggregate segregation and the rate was found to be 0.36% by weight.

The sample was manually observed for sulphurous odour presence and this could not be detected.

Throughout the specification and claims the word "comprise" and its derivatives are intended to have an inclusive rather than exclusive meaning unless the contrary is expressly stated or the context requires otherwise. That is, the word "comprise" and its derivatives will be taken to indicate the inclusion of not only the listed components, steps or features that it directly references, but also other components, steps or features not specifically listed, unless the contrary is expressly stated or the context requires otherwise.

In the present specification, terms such as "apparatus", "means", "device" and

"member" may refer to singular or plural items and are terms intended to refer to a set of properties, functions or characteristics performed by one or more items or components having one or more parts. It is envisaged that where an "apparatus", "means", "device" or "member" or similar term is described as being a unitary object, then a functionally equivalent object having multiple components is considered to fall within the scope of the term, and similarly, where an "apparatus", "assembly", "means", "device" or "member" is described as having multiple components, a functionally equivalent but unitary object is also considered to fall within the scope of the term, unless the contrary is expressly stated or the context requires otherwise.

Orientational terms used in the specification and claims such as vertical, horizontal, top, bottom, upper and lower are to be interpreted as relational and are based on the premise that the component, item, article, apparatus, device or instrument will usually be considered in a particular orientation, which will generally be apparent from the context.

It will be appreciated by those skilled in the art that many modifications and variations may be made to the methods of the invention described herein without departing from the spirit and scope of the invention.