FR2671115A1 - Composition for all-weather track, its method of production and its method - Google Patents

Abstract

The invention relates to a composition for racetrack surfacing. The composition of the invention contains a synthetic polymer, a hydrocarbon-containing oil which is liquid between 4 and 32 DEG C, and a material, such as sand, in particle form. The synthetic polymer is advantageously an elastomer, on its own or in combination with a non-elastomeric polymer; or else it is generally a mixture of polymers which are soluble and dispersible in oil, which form, with the oil, a binder for the particles. The track composition easily forms a base, and the cushioning part does not form blocks or pack down (subside), but retains its granular quality, which can be raked even at track temperatures exceeding approximately 54 DEG C. The composition is not unfavourably affected by wet weather. Application in particular to producing racecourse (horseracing) tracks.

Description

 The present invention relates to a composition useful as an all-weather coating material for tracks, in particular for horse racing tracks.

Today, most racetracks have a clay coating and are usually called "cinder" tracks. Recent studies at the Massachusetts Institute of Technology, reported in an article in The Blood-Horse of March 25, 1989, pages 1704-08, entitled "The Race for Safety", have shown that the risk of injury to a race was in direct relation with the degree of compactness of the covering on which it runs and the force bearing on the front legs of the horse. Doctor Pratt, who carried out this research, explained that ordinary "ash" tracks undergo during their use a high degree of compaction under the action of horses' hooves. This compaction reaches its maximum on the surface of the track which is just below the horse's hooves. Consequently, the track acquires areas of great compactness and areas of less compactness. Consequently, when the horse runs at high speed, the bones of its legs are likely to be subjected to very different load factors depending on the area of the track which is struck by the hoof. This study indicates that an uneven load acting on the bones of a horse's legs is a key factor of fatigue with risk of fracture when the maximum level of fatigue endurance is exceeded.

 Dr Pratt said that to improve the conditions of a runway in "ash", the moisture content of the runway should be maintained in an interval of about 7 to 11% of water. The ordinary watering vehicle used on racetracks to humidify the track increases the humidity of the track by about 0.3% per pass.

Thus, in hot and dry weather, the loss of water due to evaporation cannot be adequately compensated by the use of a watering vehicle.

 Track coating materials containing synthetic binders offer the possibility of producing a more elastic coating than an "ash" track.

However, efforts to this end have so far not produced entirely satisfactory results. For example, the product available commercially under the name of "Equitrack" sold by the firm In any case has significant drawbacks. The tracks normally include a base layer or "sole" which constitutes a compacted base of 5 to 10 cm thick covered with a "cushion" of looser granular material which has a thickness of approximately 5 cm. the construction of the track, the base or "sole" made of the material "Equitrack" is not easily formed when the ambient temperatures rise up to the daytime temperatures which one ordinarily meets in summer, namely ambient temperatures exceeding approximately 27 C. Under these conditions, the "Equitrack" material relaxes and softens and cannot easily receive the shape of the desired compacted sole. In addition, the material of the track requires an installation period of approximately 6 to 12 months during which the sole must be regularly worked until it is stabilized. Finally, the composition of "Equitrack", which tends to become sticky by direct exposure to the sun, forms by cooling blocks which create "false soles". These blocks prevent effective raking to form a correct cushion and also foul the maintenance equipment.

 It remains necessary to find a coating composition for racing tracks which is easy to install, which does not require long periods of establishment of a sole, which offers a suitable elastic cushion and which can be easily raked and maintained. .

 The invention resides in a composition suitable for use as a coating material for horse racing fields. The composition of the invention is easy to apply and does not require long periods to establish the sole. In addition, the covering material or cushion does not become sticky or tend to form blocks in hot weather, and is easy to maintain by raking. The composition of the invention also makes it possible to obtain a coating of elasticity suitable for horse racing.

 The track composition of the invention comprises a binder and a natural particulate material such as sand. The binder comprises a synthetic polymeric component and a hydrocarbon composition.

 In one embodiment, the polymeric component comprises an oil-soluble polymer and an oil-dispersible polymer. In a second embodiment, the polymer comprises an elastomer. In another embodiment, the polymer component is an elastomer in combination with another polymer.

 The hydrocarbon composition useful in the invention consists of petroleum fractions which flow readily as a liquid at normal ambient temperatures, i.e., in the range of 4.4 to 37.8 "C.

 When the particulate matter, the polymers and the hydrocarbon oil are mixed in suitable proportions, they give a composition for the coating of tracks which is suitable for use in all weathers, including in hot weather. Under normal conditions, solar radiation can heat track coverings up to 46-65 "C. At this point, as previously explained, prior art coating compositions which contain synthetic polymers become tacky and tend to forming blocks and false soles. Stable soles are difficult to form due to the softening of the composition due to heat. On the other hand, the composition of the invention, when it is subjected to sunshine even at the point of reaching a temperature in the range of 46 to 65 "C, forms a stable sole, does not become sticky and therefore does not form blocks or false soles under the shock of horses' hooves or under the action of material interview. Consequently, the cushion formed from the track composition of the invention remains suitable for raking.

On the drawings
- Figure 1 is a graphic representation which shows the effect of temperature on the pour point of binders comprising the products "Elvax 250", polypropylene "PD 5225" and "Mobilsol" R 90
- Figure 2 is a graphical representation of the effect of temperature on the pour point of binders comprising the product "Elvax 250", the ethylene-ethyl acrylate copolymer "DPD 6169" and the product "Mobilsol" R 90
- Figure 3 is a graphic representation of the effect of the content of chlorinated polyethylene binders on the pour point. The straight line in dashed lines corresponds to an extrapolation
- Figure 4 is a graphic representation of the effect produced on the pour point by the relative proportions of polypropylene and chlorinated polyethylene in binders. The dashed line on the graph corresponds to an extrapolation.

 The track covering material according to the invention comprises a particulate material such as sand, and a binder comprising a synthetic polymer component which may be a polymer or a mixture of polymers, and a hydrocarbon oil.

 The particulate matter comprises sand, clay or a mixture thereof and is preferably sand which generally contains particles of about 0.06 to about 2 mm. The particle diameter and the characteristics of the sand are not, however, decisive with regard to the properties of the final composition.

 The petroleum oil or hydrocarbon oil which can be advantageously used in the composition of the invention is a liquid capable of flowing at ambient temperatures, that is to say at temperatures of approximately 4.4 to approximately 37.8 C. Useful petroleum fractions include heavier or higher boiling fractions than kerosene, that is, gas oils. In particular, oils such as the aromatic oils sold by the company Mobil under the names of "Mobisol" R 90 and 30 are particularly useful.

 As mentioned above, the synthetic polymer component can be a polymer or a mixture of polymers. The invention can be divided into three embodiments based on the polymeric component.

 In one embodiment, the polymer component comprises an oil-soluble polymer, in particular chosen from soluble copolymers of ethylene with ethyl acetate, the ethyl acetate content of which ranges from approximately 20 to approximately 30 t by weight and an oil dispersible polymer, in particular chosen from copolymers of ethylene and propylene dispersible in oil. In a second embodiment, the polymer comprises an elastomer. And in another embodiment, the polymer component is an elastomer in combination with another polymer.

When using polymers which are soluble and dispersible in oil, the polymer-oil mixture used as a binder is of a thixotropic nature and resists decomposition by heat, that is to say when it is mixed with sand to form a coating material for race tracks, it resists a passage to the sticky state and the formation of blocks, so that it is stable even at temperatures reaching 45-65 "C. Representative examples polymers dispersible in petroleum oils include polypropylene PD 5225 (IF 60) from the company Exxon, the ethylene-ethyl acrylate copolymer DPD 6169 from the company Union
Carbide, etc., comprising polymers of these types having different molecular weights. Oil-soluble polymers include ethylene vinyl acetate (EVA) copolymers having a vinyl acetate content of at least about 25% by weight. weight such as, for example, the product Elvax 250 from the firm DuPont.

 When preparing the polymer-oil binder using the soluble polymer-dispersible polymer embodiment, any order of mixing can be used. For example, one could first mix petroleum oil with the soluble polymer and then add the dispersible polymer. In general, the petroleum oil-polymer binder produced in this embodiment contains about 95 to about 85% by weight of petroleum oil based on the total weight of the mixture of polymers and oil; about 70 to 30% by weight of soluble polymer and about 30 to about 70% by weight of dispersible polymer, the weight percentages being based on the total weight of the polymers only.The specific ratio between these polymers depends on the particular polymers that are used and it can be easily determined by a small number of tests as indicated in the examples given below.

 The binder composition according to the invention preferably does not flow readily at temperatures below about 52 "C.

 To produce a raceway coating material, the binder must be mixed with a particulate material such as, for example, sand. Useful associations of binders based on hydrocarbon oil and oil-soluble polymer-dispersed in oil with particles include associations in which the binder represents a proportion of 3 to about 12% by weight, preferably of 4 to 8% by weight.

 In another embodiment, the elastomeric polymer is used to formulate the binder.

The elastomeric polymer may be a styrenebutadiene copolymer, an ethylene-propylene-diene copolymer or a mixture thereof, or may be chosen from chlorinated polyethylenes such as, for example, chlorinated polyethylene T4211 from the company Dow Chemical (chlorine content 42%, melt viscosity 900 Pa.s), etc. In addition, the elastomeric polymer does not need to be a single polymer, but can consist of a mixture of polymers.

Thus, for example, mixtures of high molecular weight and low molecular weight elastomers such as the product CPE T-3623A from the company Dow Chemical (36% chlorine, melt viscosity 1800 Pa.s) and the product CPE T-4211 from the same company can be mixed with the product Mobilsol R 30 to form an excellent binder in which the proportion of CPE T-3623A is approximately 9% by weight, the proportion of CPE T-4211 is approximately 2% by weight and the proportion of Mobilsol R 30 is approximately 89% by weight. It goes without saying that the invention is not limited to these examples of percentages by weight or of mixtures. In general, the binder composition can range from about 5 to about 15% by weight of polymer, preferably from about 7 to about 12% by weight of polymer. The hydrocarbon oil content of the binder can range from about 85 to about 95% by weight, preferably 88 to 93% by weight. In addition, the composition useful as a race track coating material includes the binder in association with a suitable particulate material.

The binder content of this coating material can vary from about 3.0 to about 12% by weight, preferably from about 4 to about 8% by weight.

 In another embodiment, the polymeric component comprises an oil-soluble elastomeric polymer in combination with an oil-dispersible polymer such as, for example, polypropylene. This polymer component can be incorporated into petroleum oil to form the binder by any mixing process; for example, the first polymer can be mixed with the oil and then the other can be added, or a mixture of polymers can be added to the oil. The composition of the binder can range from 5 to 15% by weight of polymeric component, preferably 7 to 12% by weight based on the total weight of binder. The proportion of elastomeric polymer can range from about 30 to about 100% by weight, preferably from about 50 to about 90% by weight of the polymer component. In order to use this binder in combination with the particulate material to produce a coating composition for race tracks, the coating composition can usually contain from about 3.0 to about 12% by weight of binder, preferably about 4 to about 8% by weight of binder.

The invention also relates to a method for producing a coating composition for racing tracks, characterized in that it consists
(i) mixing a synthetic polymer or a mixture of polymers with a hydrocarbon oil; said oil being fluid at temperatures from about 4 to about 32 "C, to form a binder which does not readily flow at temperatures below about 52"C; and
(ii) adding said binder to a particulate material or to mixtures of such materials to produce a composition for coating race tracks. Under preferential conditions, said polymers comprise an ethylene-vinyl acetate copolymer, copolymers of ethylene and propylene dispersible in oil, a chlorinated polyethylene, a styrene-butadiene copolymer, an ethylenepropylene-diene copolymer or their mixtures.

The invention finally relates to a method of using the compositions described above, characterized in that it consists
(i) raking the composition; and
(ii) running horses on the composition, a process for forming a covering for race tracks, characterized in that it consists
(a) making a sole by laying a thickness of at least about 10 cm from the composition described above; and
(b) covering the sole with a cushion of the composition described above, as well as a method for forming a covering for race tracks, characterized in that it consists
(a) placing a sole approximately 12.7 cm thick from the composition described above; and
(b) harrowing the upper part by about 5 cm from the sole to form a cushion.

 The following examples serve to illustrate particular embodiments and should not be considered as defining the scope of the invention which has been set out above.

 In the examples, the term "pour point" refers to the starting flow temperature of a material used as a binder. The pour point is measured by loading a sample of 85.05113.4 ml of binder into a 113.4 ml container and allowing the sample to age for 48 hours at room temperature. The binder is then placed in an oven and the temperature is raised in steps of 5.5 "C.

The sample containers are then inverted at 90 "and, if the material flows easily or if it is found to move significantly, this temperature is therefore recorded to represent its pour point.

 In addition, the term "bonding" refers to the property similar to that of the adhesive which is necessary to compact the particulate material so as to form a stable sole useful as a coating composition for race tracks. The grip is measured by placing a small amount of the binder between the index finger and the thumb and pressing it into a thin film. A quick movement of moving the thumb and index finger closer, apart and closer together ("work") gives an indication of the hooking characteristic. The force necessary to detach the fingers and the ability of the product to adhere again -determine the attachment of the product. Although this test is somewhat subjective, the Applicant does not know of standardized methods allowing this stickiness characteristic to be measured.

Example 1
Several mixtures of binders were prepared with the oil-soluble polymer Elvax 250 from the firm
DuPont (ethylene vinyl acetate (EVA) 28%, IF 25) and an oil dispersible polymer, polypropylene (PP) PD 5225 IF 60 from the company Exxon in a hydrocarbon oil,
Mobilsol R 90. These mixtures were prepared at 160-190 "C with stirring. The binders contained 10 to 12% by weight of the total polymer component based on the total weight of binder. Mixtures were prepared with ratios
EVA: PP, in% by weight, from 0: 100, 40:60, 50:50, 60:40 and 100: 0. The pour point of these mixtures was determined, the results being reported in Figure 1.

The results indicate that to reach a pour point exceeding about 52 "C, the binder must contain less than about 60% by weight of Elvax. Furthermore, when the proportion of Elvax is reduced to less than about 30% by by weight, the binder begins to lose its tackiness and ability to bind particulate matter, therefore the optimal range of EVA: PP weight percent ratios is 30:70 to 50:50 for this particular composition.

Example 2
A series of binders was prepared using the product DPD 6169 from the firm Union Carbide (ethylene ethyl acrylate or EEA); the product Elvax 250 from the firm DuPont (ethylene vinyl acetate or EVA) and the product Mobilsol R 90. These binders contained 10% by weight of the total polymer component based on the weight of binder. Binders were prepared with ratios (% by weight) EVA: EEA of 100: 0, 60:40, 50:50, 40:60, 30:70 and 0: 100. The pour point and the attachment point were determined on these mixtures, the results being reproduced in FIG. 2. From FIG. 2, it appears that to reach a pour point exceeding approximately 54 "C, the percentage by weight of EVA should be less than about 40% by weight. However, as the percentage by weight of EVA decreases, so does the bonding or adhesiveness of the binder. Thus, the useful range of proportion EVA ranges from about 20 to about 40% by weight of the total polymer added for this composition.

Example 3
Mixtures were prepared with 10% by weight of product T-4211 from the company Dow Chemical (chlorinated polyethylene (CPE) containing 42 t of chlorine) and 90% by weight of
Mobilsol R 90. It was found that this mixture had very good bonding and it did not flow until it was heated to about 54 "C. When another identical mixture was prepared, except that the CPE content was 10.6% by weight, this mixture proved to be rubbery at room temperature with good adhesion, and it did not flow even at temperatures above 60 "C. Consequently, the proportion of CPE has a significant effect on the properties of the binder, as shown in FIG. 3.

Example 4
A composition was prepared by mixing 70% by volume of a first mixture containing 10.6% by weight of chlorinated polyethylene T-4211 from the company Dow Chemical and 89.4% by weight of Mobilsol R 90, with 30% by weight. volume of a second mixture containing 10% by weight of polypropylene PD 5225 from the company Exxon in the product Mobilsol R 90. The resulting binder proved to be rubbery with excellent adhesion and had a pour point exceeding 65 "C. , as shown in Figure 4.

Example 5
Five 200g portions of sand were heated to 1800C with stirring. Without stopping the agitation, about 6.1-6.5% by weight of a binder composition was added to each of the five sand samples. These binder compositions were as follows
(a) A binder containing 10% by weight of mixture of polymers and 90% by weight of Mobilsol R 90. The mixture of polymers contained 60% by weight of EEA DPD 6169 and 40% by weight of Elvax 250.

(b) A binder composition containing 10% of a mixture of polymers and 90% of Mobilsol R go. The polymer blend consisted of 55% by weight of
PD 5225 from the company Exxon and 45% by weight of Elvax 250.

 (c) A binder containing 10.6% by weight of chlorinated polyethylene T-4211 from the company Dow Chemical and 89.4 * by weight of Mobilsol R 90.

 (d) A binder containing 11.3% by weight of chlorinated polyethylene T-4211 from the company Dow Chemical and 88.7% by weight of Mobilsol R 90.

 (e) A commercial sand / binder mixture sold under the trade name "Equitrack".

 Each of the five samples was tested for compaction, heat stability and raking ability. In the compaction test, about 50% of the sand-binder mixture was loaded into a glass cylinder closed at one end, 38.1 mm in diameter. The product was lightly packed and the core of compacted material was removed. If this core of material failed to bond, compaction was deemed to be inadequate. The cores formed of binder and sand were then exposed to sunlight for a period of 4 hours during which ambient temperatures ranged from 29 to 35 "C. At the end of this period of exposure to sunlight, the temperature of the carrots just below the surface was found to be 62" C. Each core was then subjected to a block formation and raking ability test.

 The composition using binder (a) was suitably compacted and did not lose its shape after exposure to sunlight. When the material was spread, it did not appear excessively tacky and could be raked without forming blocks. This property was not changed after cooling to 25 "C.

 The composition using binder (b) was suitably compacted and the carrot did not lose its shape after exposure to sunlight. The material could be raked without forming blocks. The composition containing the binder (c) has shown a very good compactability and has held up well to heat. Under hot raking conditions, the composition showed no tendency to block.

 The composition using binder (d) gave results similar to those of the composition using binder (c), except that the material allowed an even more rigid compaction. The composition did not become excessively tacky on heat and raking did not cause blocking.

The composition prepared using the binder
Commercial Equitrack showed good compaction at 25 "C. However, the surface of the carrot became sticky when heated in direct sunlight. When the material was spread and raked, it showed a tendency to form. The hot product also tended to adhere to the rake. During cooling, the blocks formed did not fall apart during a subsequent raking. The product was not as granular and as fluid as it was. had been before the hot test.

 From an analysis of these results, it can easily be seen that the product of the invention is superior to the product available on the market. The product of the invention is more stable under normal conditions of heating by exposure to direct sunlight and gives a base material suitable for raking and not compacting, remarkably suitable for forming a coating composition for race tracks. Binder proportions of 5% by weight or more can be used to obtain the easy formation of a sole without appreciable loss of heat resistance, i.e. without the tendency to soften which makes the formation of the sole.

 It goes without saying that the present invention has only been described for explanatory but in no way limitative, and that numerous modifications can be made thereto without departing from its scope.

Claims (12)

 1. Composition useful for race track coatings, characterized in that it comprises a natural particulate material and a binder comprising a synthetic polymeric component and a fluid hydrocarbon oil in the range from 4.4 to 37.8 C.  2. Composition useful for race track coatings according to claim 1, characterized in that it consists  (i) a binder comprising  (a) an oil-soluble polymer chosen from soluble copolymers of ethylene with ethyl acetate, the ethyl acetate content of which ranges from about 20 to about 30 tonnes by weight;  (b) an oil dispersible polymer chosen from copolymers of ethylene and propylene dispersible in oil; and  (c) a hydrocarbon oil, this oil being fluid in a temperature range from about 4.4 to about 37.8 "C; and  (ii) a particulate material comprising sand, clay or mixtures thereof; the binder composition does not readily flow at temperatures below about 52 "C.  3. Composition according to claim 2, characterized in that the oil-soluble polymer represents approximately 30 to approximately 70% by weight and the dispersible polymer represents approximately 70 to approximately 30% by weight of the total weight of the polymers; the good hydrocarbon oil represents approximately 85 to approximately 95% by weight of the total weight of the polymers and of the oil; the binder representing a proportion of about 3 to about 12 t by weight relative to the total weight of the binder and the particulate matter.  4. Composition useful for race track coatings according to claim 1, characterized in that it consists  (i) a binder composition comprising  (a) an elastomeric polymer component comprising a chlorinated polyethylene, a styrene butadiene copolymer, an ethylene-propylene-diene copolymer or mixtures thereof; and  (b) a hydrocarbon oil, said oil being fluid in the temperature range of about 4.4 to about 37.8 "C; and  (ii) a particulate matter  said binder composition not flowing easily at temperatures below about 52 "C.  5. Composition according to claim 4, characterized in that the elastomeric polymer component ranges from about 5 to about 15% by weight; the hydrocarbon oil ranges from approximately 85 to approximately 95 tonnes by weight relative to the total weight of the binder; and the binder ranges from about 3 to about 12% by weight relative to the total composition for race tracks.  6. Composition according to claim 4, characterized in that it further comprises a second non-elastomeric polymer component consisting of polypropylene.  7. Composition according to claim 6, characterized in that the second non-elastomeric polymer component is up to about 70 t by weight relative to the total weight of the polymers.  8. Composition according to claim 4, characterized in that the elastomeric polymer component consists of a mixture of elastomers.  9. Method for producing a coating composition for race tracks, characterized in that it consists  (i) mixing a synthetic polymer or a mixture of polymers with a hydrocarbon oil; said oil being fluid at temperatures from about 4.4 to about 37.8 "C, to form a binder which does not readily flow at temperatures below about 52" C; and  (ii) adding said binder to a particulate material or to mixtures of such materials to produce a composition for coating race tracks.  10. The method of claim 9, characterized in that said polymers comprise an ethylene-vinyl acetate copolymer, copolymers of ethylene and propylene dispersible in oil, a chlorinated polyethylene, a styrene-butadiene copolymer, an ethylene copolymer - propylene-diene or their mixtures.  ll A method of using the compositions according to claim 2, 4 or 6, characterized in that it consists  (i) raking the composition; and  (ii) run horses on the composition.  12. Method for forming a coating for race tracks, characterized in that it consists  (a) producing a sole by laying a thickness of at least about 10 cm of the composition according to claims 2, 4 or 6; and  (b) covering the sole with a cushion of the composition according to claims 2, 4 or 6.  13. Method for forming a covering for race tracks, characterized in that it consists  (a) placing a sole approximately 12.7 cm thick in the composition according to claims 2, 4 or 6; and  (b) harrowing the upper part by about 5 cm from the sole to form a cushion.