GB2311295A - Sports surfaces - Google Patents

Abstract

A sports playing surface comprising a coating and/or line markings and a base layer containing an aggregate and bitumen wherein the bitumen has dispersed or dissolved therein at least one oil-soluble soap which is a manganese, copper or cobalt salt of a monocarboxylic acid having not more than 30 carbon atoms and which is present in an amount such that the composition contains from 0.01. to 1%, based on the weight of the bitumen, of manganese, copper and/or cobalt ions.

Description

SPORTS SURFACES The invention relates to the use of modified bitumen compositions in the construction of coated and/or marked sports playing surfaces.

Sports such as tennis, basketball, netball etc. are often played on artificial surfaces comprising a bottom layer of bituminous macadam, upon which there is an optional coating of e.g. hard acrylic surfacing and/or markings particular to the relevant sport.

In hot weather or when such sports surfaces are new and have not yet fully hardened, the macadam layer is relatively yielding to the pressure exerted by the players. Such yielding tends to generate areas of wear in the surface coating and markings. This wear reduces the effective life of the sports surface which has to be replaced at great cost.

It is therefore desirable to provide a base layer for a sports surface which hardens quickly upon construction and is resistant to significant softening in hot weather.

Bituminous mixtures are a combination of mineral aggregates or slag aggregates, filler and bitumen or a bitumen-based blinder.

The mechanical properties of bituminous mixtures result from friction and cohesion. The friction comes from the interlock of the aggregate. It depends on the maximum aggregate fraction size used to form a blend and on the grading of the aggregate fractions which are blended together. The cohesion comes from the properties of the bitumen or bitumen-based binder. The flow or rheological properties of the binder are used to enable the mixture to be adequately prepared.

The vast majority of aggregates used for bituminous mixtures are derived from natural sources. These can be blasted and quarried from single lithology sources, dredged or excavated from pits, estuaries and rivers. Artificial aggregates from the by-products of steel manufacture or the remains of spent fuel can provide suitable alternatives to natural sources.

The chemical structure of bitumens makes them unstable materials. The resinous chemical structures can break down resulting in an increase in the viscosity and stiffness of the material. The material will also become less ductile. This type of breakdown is caused by heat and exposure to oxygen in the atmosphere. The degree of breakdown (oxidation) and 'hardening of a bitumen will depend on the temperature, the time held at that temperature and the ratio of the exposed surface area to the volume of the bitumen. Critical high temperature processes for bitumen occur during mixing with an aggregate and during the storage of the resultant mixture. The mixing process is critical. The temperature of the material must be high and because of the mixing process, a high surface area to volume of material exists. In service, exposure to the atmosphere at ambient temperatures will cause a hardening of the bitumen. In addition water may leach out from some of the chemical structures within the resinous fraction of the bitumen. This causes a further hardening of the material.

Sometimes, "bitumen" is generally referred to as "asphalt" therefore in discussing documents hereinafter the term asphalt will be maintained.

GB -A- 1,600,897 says that aggregate-containing asphalt has been employed as a paving composition for roads. The asphalt is conventionally obtained as a solid residue from the distillation of crude petroleum but is converted to a fluid state when paving a road. One fluid form is the suspension or emulsion of the asphalt in water.

After spreading and compressing the aggregate-containing asphalt, water evaporates and the asphalt hardens into a continuous mass. Another form of asphalt employed in road construction is a cut-back i.e., a liquid petroleum produced by fluxing an asphaltic base with a suitable distillate. A road is formed by layering the cut-back and evaporating the volatile distillate from the mass. In an alternative technique, the asphalt and aggregate can be mixed and applied at elevated temperatures at the fluid state of the asphalt to form the road.

US -A- 2,343,861 describes a method for increasing the adhesiveness of asphalt, especially in the form of a cut-back or emulsion, to be employed with aggregate in road construction. The patent discloses the addition of a lead soap, specifically lead oleate or naphthenate, to asphalt emulsions to increase the adhesiveness for aggregate. It is suggested that other heavy metal salts of organic acids such as Fe, Al, Mn, Zn, Co, Ni, Sn, Ca, Sr, Ba and Mg may also be employed.

A technique for fonning the lead soap by heating a lead oxide in the presence of the desired organic acids is also described. Such lead soaps are then added to the desired asphalt.

US -A- 2,928,753 discloses heavy metal soaps for use as dispersants in roofing asphalts to prevent failure of the asphalt due to "alligatoring". It discloses polyvalent metal salts of copper, cobalt, or manganese in combination with high molecular weight monocarboxylic acids such as oleic or naphthenic acid.

GB -A- 1,600,987 further discloses the use of oil-soluble soap to increase the strength of cured asphalt in a composition containing aggregate for road surfacing.

However when such compositions were used in practice the hardened roads proved to be susceptible to cracking under the weight of traffic and their use was discontinued.

The present inventors have discovered that hardened paving compositions are of particular benefit when used as a base for sports surfaces which have been coated and/or marked with lines or other indicia.

Hence according to the present invention there is provided a sports playing surface comprising a coating and/or markings and a base layer containing an aggregate and bitumen wherein the bitumen has dispersed or dissolved therein at least one oilsoluble soap which is a manganese, copper or cobalt salt of a monocarboxylic acid having not more than 30 carbon atoms, or a mixture of two or more thereof, and which is present in an amount such that the composition contains from 0.01 to 1%, based on the weight of the bitumen, of manganese, copper and/or cobalt ions.

In preferred embodiments of the present invention the salt is a linoleate, octoate, naphthenate, oleate, stearate, or laurate and the salt is preferably a manganese salt.

A further embodiment of the present invention comprises the use of an oilsoluble soap in the manufacture of a bituminous based sports surface wherein the sports surface has a coating and/or markings and the oil-soluble soap is dispersed or dissolved in the bituminous base composition and wherein the oil-soluble soap is a manganese, copper or cobalt salt of a monocarboxylic acid having not more than 30 carbon atoms, or a mixture of two or more thereof, and which is used in an amount such that the composition contains from 0.01 to 1%, based on the weight of the bitumen, of manganese, copper and/or cobalt ions. Oil-soluble soaps for use according to the invention are generally available commercially and may most preferably be added to the bitumen as a 10% solution in an appropriate hydrocarbon solvent.

Coatings may be any of those known in the art to be suitable for a hard playing surface but include e.g. hard non-ferrous acrylic surfaces. Markings may be composed of any paint or other coating composition known in the art to be suitable for this purpose and are preferably of an ultra-high viscosity.

In particularly preferred embodiments of the present invention, the bituminous surface may be produced as follows. Crushed rock and sand aggregates are heated to a temperature of 100do to 200PC. A hot petroleum bitumen of grade in the range 50 to 400 penetration is added and mixed with the aggregates. A manganese carboxylate salt is added to the bitumen at the rate of between 0.01 to 0.5kg per tonne of bitumen aggregate mixture. The mixture may then be applied to an appropriate site for rolling to form a sports surface using traditional techniques. Suitable coatings and/or markings may be applied once the base has hardened.

Claims (12)

1. A sports playing surface comprising a coating and/or line markings and a base layer containing an aggregate and bitumen wherein the bitumen has dispersed or dissolved therein at least one oil-soluble soap which is a manganese, copper or cobalt salt of a monoboxylic acid having not more than 30 carbon atoms and which is present in an amount such that the composition contains from 0.01. to 1%, based on the weight of the bitumen, of manganese, copper and/or cobalt ions.

2. A sports playing surface according to claim 1 wherein two or more oil-soluble soaps are dispersed or dissolved in the bitumen.

3. A sports playing surface according to either claim 1 or claim 2 wherein the salt is a linoleate, octoate, naphthenate, oleate, stearate, or laurate.

4. A sports playing surface according to any of claims 1 to 3 wherein the salt is a manganese salt.

5. Use of an oil-soluble soap in the manufacture of a bituminous based sports surface wherein the sports surface has a coating and/or markings and the oil-soluble soap is dispersed or dissolved in the bituminous base composition and wherein the one-oil soluble soap which is a manganese, copper or cobalt salt of a monocarboxylic acid having not more than 30 carbon atoms, and which is used in an amount such that the composition contains from 0.01. to 1%, based on the weight of the bitumen, of manganese, copper and/or cobalt ions.

6. User according to claim 5 wherein two or more oil-soluble soaps are dispersed or dissolved in the bitumen.

7. Use according to ether claim 5 or claim 6 wherein the salt is a linoleate, octoate, naphthenate, oleate, stearate or laurate.

8. Use according to any of claims 6 to 8 wherein the salt is a manganese salt.

9. A tennis court comprising a surface as claimed in any of claims 1 to 4.

10. A tennis court comprising a surface produced using a method comprising use of an oil-soluble soap, as claimed in any of claims 5 to 8.

11. A sports playing surface according to claim 1 substantially as herein described.

12. Each and every novel feature, composition and method substantially as herein described.