GB2251247A - Racetrack surface composition - Google Patents

Abstract

A racetrack surface composition includes a synthetic polymer component, a hydrocarbon oil fluid between 40 DEG -100 DEG F (4 DEG -38 DEG C), and a particulate material such as sand. The synthetic polymer component is preferably either an elastomer, or an elastomer in combination with non-elastomeric polymer; or alternatively a mixture of oil soluble and oil dispersible polymers which together with the oil form a binder for the particulate material. The racetrack composition readily forms a pad and the cushion portion does not clump or compact but maintains its granular, rakeable quality even at track temperatures above about 130 DEG F (55 DEG C). The composition is not adversely affected by wet weather.

Description

TITLE: ALL WEATHER RACETRACK COMPOSITION Background of the Invention 1. Field of the Invention This invention relates to a composition useful as an all-weather surface material for racetracks, especially horse racetracks.

2. Background Currently, most horse racetracks are covered with a clay surface and are commonly referred to as "dirt" tracks. Recent studies at the Massachusetts Institute of Technology as reported an -article in The Blood-Horse of March 25, 1989, pp. 1704-08 entitled "The Race for Safety," have shown that the risk of injury to a racehorse is directly related to the degree of compaction of the surface upon which it is being raced and the amount of force brought to bear upon the horse's front legs. Dr.

Pratt, who carried out this research, explained that during use ordinary dirt tracks undergo a great deal of compaction under the action of horses hooves. This compaction is greatest on the track area immediately beneath the horses hooves. Consequently, the track develops areas of high compaction and areas of lesser compaction. When running at speed, therefore, the bones of the horse's legs could experience very different load factors depending upon the area of the track upon which the hoof impacts. The study indicates that uneven loading of a horse's leg bones is a key factor in fatigue with consequent fracture when the maximum level of fatigue endurance is exceeded.

In order to improve "dirt" track conditions, Dr.

Pratt indicates that the moisture content of the track should be kept within a window of about 7-11% water. The ordinary water truck used at racetracks to moisten the track increases track moisture by about .3 of one percent per pass. Thus, on a hot, dry day, the loss of water due to evaporation may not be replenished adequately by use of a water truck.

Racetrack surface materials using synthetic binders offer the potential for producing a surface more resilient than a "dirt" track. However, thus far efforts in this direction have not produced altogether successful results.

For example, the commercially available product, EQUITRACK, sold by En tout cas has significant disadvantages. Racetracks typically include a base layer or "pad" which is a compacted base 2-4 inches thick covered by a "cushion" of looser, granular material which is about 2 inches thick. At the track installation stage, the base or "pad" based on the EQUITRACK material is not easily formed when ambient temperatures rise to typically encountered Summer daytime temperatures, ambient temperatures above about 800F. Under these conditions, the EQUITRACK material loosens and softens and cannot be easily formed into the desired compacted pad. Further, the track material requires a settling-in period of about 6-12 months during which the pad has to be regularly worked until it is established.Finally, the-EQUITRACK composition, which tends to become sticky in direct sunlight, forms clumps when it cools creating "false pads." These clumps prevent effective raking to form a proper cushion and also fouls maintenance equipment.

There yet exists a need for a racetrack surface composition that provides ease of installation, does not require long periods of time to establish a pad, provides a suitable, resilient cushion and that is readily rakeable and easily maintained.

Summary of the Invention The invention is a composition suitable for use as a horse racetrack surface material. The invention composition is easily installed, not requiring long periods of time to establish the pad. Further, the surface or cushion material does not become sticky or tend to form clumps in hot weather and is easily maintained by raking. The invention composition also provides a suitably resilient surface for horse racing.

The invention racetrack composition 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.

And, in yet another embodiment, the polymeric component is an elastomer in combination with another polymer.

The hydrocarbon composition useful in the invention are those petroleum fractions which will flow readily as a liquid at normal ambient temperatures, i.e., in the range 40-90 F.

When the particulate, polymers and hydrocarbon oil are combined in appropriate proportions, they provide a racetrack cover composition which is suitable for use in all weather conditions including hot weather. Under normal conditions, solar radiation can cause racetrack surfaces to heat up to 115-1500F. At this stage, as explained previously, prior art surfacing compositions which contain synthetic polymers become sticky and tend to form clumps and false pads. Stable pads are difficult to form due to the softening of the composition due to heat.

In contrast, the invention composition, when subject to insolation even to the point of reaching a temperature in the range of 115-15O0F, will form a stable pad, will not become sticky and will therefore not form clumps or false pads under the impact of horses hooves or the action of maintenance equipment. Consequently, the cushion of the invention track composition will maintain a rakeable quality.

Brief Description of the Drawings Fig. 1 is a graph showing the effect of temperature on the pour point of binders including ELVAX 250, polypropylene PD 5225 and MobilsolE 90.

Fig. 2 is a graph showing the effect of temperature on the pour point of binders including ELVAX 250, ethylene ethacrylate DPD 6169 and MobilsolS 90.

Fig. 3 is a graph showing the effect of chlorinated polyethylene content of binders on pour point. Dashed lines on the graph reflect extrapolation.

Fig. 4 is a graph showing the effect of the relative proportions of polypropylene and chlorinate polyethylene in binders on pour point. Dashed lines on the graph reflect extrapolation.

Description of the Preferred Embodiments The invention racetrack surface material includes a particulate material such as sand, and a binder comprising a synthetic polymer component which may be a polymer or mixture of polymers, and a hydrocarbon oil.

The particulate material is preferably sand which generally contains particles sized from about 0.06 to about 2 mm. The particle size and characteristcs of the sand are, however, not critical to the properties of the final composition.

The petroleum or hydrocarbon oil suitable for use in the invention composition is a liquid able to flow at ambient temperatures, i.e. from about 40 to about 900F.

Useful petroleum fractions include those fractions heavier than or of higher boiling point than kerosene, i.e. gas oils. In particular, oils such as the aromatic oils sold by MOBIL as Mobisole 90 and 30 are especially useful.

As mentioned before, the synthetic polymer component may be a polymer or a mixture of polymers. The invention may be separated into three embodiments based upon the polymeric component.

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.

And, in yet another embodiment, the polymeric component is an elastomer in combination with another polymer.

When a combination of oil soluble and oil dispersible polymers are used, the polymer-oil binder mixture is thixotropic in nature and resistant to heat breakdown, i.e., when combined with sand to form a race trach surface material it is resistant to becoming sticky and clumping together so that it is stable even at temperatures as high as 125-1500F. Typical examples of petroleum oil dispersible polymers include: Exxon's polypropylene PD5225 (MI 60), Union Carbide's ethylene ethylacrylate copolymer DPD 6169 and the like, including polymers of these types having different molecular weights. The oil soluble polymers include the ethylene vinyl acetate copolymers (EVA) having at least about 25 wt.% vinyl acetate content such as, for instance, DuPont's ELVAX 250.

In preparing the polymer-oil binder using the soluble polymer-dispersible polymer embodiment, any order of mixing may be used. For instance, one could first mix the petroleum oil with the soluble polymer and then add the dispersible polymer. In general, the petroleum oil-polymer binder produced in this embodiment includes from about 94 wt.% to about 85 wt.% petroleum oil based upon the total weight of the mixture of polymers and oil; from about 70 wt.% to 30 wt.% soluble polymer; and from about 30 wt.% to about 70 wt.% dispersible polymer, where the polymer wt.% are based upon the total weight of the polymers only. The specific ratio between these polymers depends upon the specific polymers used and may be readily determined with a few tests as shown in the examples below.

In order to produce a racetrack surfacing material the binder must be combined with a particulate material such as, for instance, sand. Useful combinations of the oil soluble-oil dispersed polymer and hydrocarbon oil binders with particulates include those combinations wherein the binder is from 3 wt.% to about 12 wt.%, preferably from 4 wt.% to 8 wt.%.

In an alternative embodiment, an elastomeric polymer is used to formulate the binder. The elastomeric polymer may be selected from the chlorinated polyethylenes such as, for instance, Dow Chemical's chlorinated polyethylene T-4211, (chlorine content 42%, melt viscosity 9000 poise), and the like. Further, the elastomeric polymer need not be one polymer but can be a blend of polymers. Thus, for example blends of higher and lower molecular weight elastomers such as Dow Chemical's CPE T-3623A (36% Cl, melt viscosity 18,000 poise) and CPE T-4211 may be blended with MobilsolE 30 to produce an excellent binder wherein the CPE T-3623A proportion is about 9 wt%, the CPE T-4211 is about 2 wt% and the MobilsolE 30 is about 89 wt%. It being understood that the invention is not limited to these exemplary weight percentages or blends.In general, the binder composition can range from about 5 wt.% to about 15 wt.% polymer; preferably from about 7 to about 12 wt.% polymer. The hydrocarbon oil content of the binder may range from about 85 to about 95 wt.%; preferably 88 to 93 wt.%. Further, the composition useful as a racetrack surfacing material includes the binder in combination with suitable particulate material. The binder content of this surfacing material may vary from about 3.0 to about 12 wt.%; preferably from about 4 to about 8 wt.%.

In yet another embodiment, the polymer component comprises an oil soluble elastomeric polymer in combination with an oil dispersible polymer such as, for example, polypropylene. This polymer component may be blended into petroleum oil to form the binder by any mixing procedure, for example, first one polymer may be mixed with the oil, then the other may be added or a mixture of polymers may be added to the oil. The binder composition may range from 5 to 15 wt.% polymer component, preferably 7 to 12 wt.%, based upon the total weight of the binder. The proportion of elastomeric polymer may range from about 30 to about 100 wt.%, preferably from about 50 wt.% to about 90 wt.%, of the polymer component.

In order to use this binder in combination with particulate material to produce a racetrack surface composition, the surface composition may usefully include from about 3.0 to about 12 wt.% binder, preferably from about 4 to about 8 wt.% binder.

The following examples serve to illustrate specific embodiments and are not intended to define the scope of the invention which is explained above and claimed below.

In the Examples, the term "pour point" refers to the temperature of incipient flow of a binder material. The pour point was measured by placing a 3-4 oz. sample of binder material in a 4-oz. jar and aging this for 48 hours at room temperature. The binder was then placed in an oven and the temperature increased in 10 F increments.

The sample containers were then tilted 900 and, if the material poured readily or was seen to move significantly, then this temperature was recorded as its pour point.

Further, the term "tack" refers to the adhesive-like property which is required to compact the particulate matter to form a stable pad useful as a racetrack surface composition. The tack was measured by placing a small amount of the binder between the forefinger and thumb and pressing this into a thin film. Rapid closing, separation and closing of the thumb and forefinger ("working") gives an indication of the tack characteristic. The force required to separate the fingers and the ability of the product to re-adhere determines the tack of the product.

While this test is somewhat subjective, the inventor is not aware of standardized procedures for measuring this adhesive characteristic.

Example 1 Several blends of binders were prepared with oil soluble polymer, DuPont ELVAX 250 (ethylene vinyl acetate (EVA) 28% MI 25) and an oil dispersible polymer, Exxon's polypropylene (PP) PD 5225 MI 60 in a hydrocarbon oil, MobilsolE 90. These blends were prepared at 320 - 3750F with mixing. The binders contained 10-12 wt.% of total polymer component based on the total weight of binder.

Blends were prepared with EVA:PP wt.% ratios of 0:100, 40:60, 50:50, 60:40 and 100:0. These blends were tested for pour point and the results are shown in Fig. 1. The results indicate that to achieve a pour point in excess of about 1250F, the binder should contain less than about 60 wt.% ELVAX. On the other hand, when the proportion of ELVAX is reduced to less than about 30 wt.%, the binder begins to lose tack or capability to bind particulate matter. Consequently, the optimal range of wt.% ratios of EVA:PP is from 30:70 to 50:50 for this particular composition.

Example 2 A series of binder blends were prepared using Union Carbide's DPD 6169 (ethylene ethacrylate or EEA); DuPont's ELVAX 250 (ethylene vinyl acetate or EVA) and MobilsolE 90. These binders contained 10 wt.% of total polymer component based upon the weight of the binder. Binders were prepared with EVA:EEA wt.% ratios of 100:0, 60:40, 50:50, 40:60, 30:70, 0:100. These blends were tested for pour point and tack and the results are tabulated in Fig.

2. From Fig. 2, it is apparent that to achieve a pour point of above about 1300F, the wt.% EVA should be less than about 40 wt.%. However, as the wt.% EVA decreases, so does the tack of the binder. Thus, the useful range of EVA proportion is from about 20 to about 40 wt.% of the total polymer added for this composition.

Example 3 Blends were prepared with 10 wt.% of Dow Chemical's T-4211 (a chlorinated polyethylene (CPE) containing 42% chlorine) and 90 wt.S MobilsolE 90. This blend was found to have very good tack and did not pour until heated to about 1300F. When another-identical blend was prepared with the exception that the CPE content was 10.6 wt.%, it was rubbery at room temperature with good tack and did not pour even at temperatures above 140"F. Consequently, the proportion of CPE has a significant effect on the binder properties as shown in Figure 3.

Example 4 A blend was prepared by mixing 70% by volume of a first blend containing 10.6 wt.% of Dow Chemical's T-4211 chlorinated polyethylene and 89.4 wt.% MobilsolS 90; with 30 volume % of a second blend containing 10 wt.% of Exxon's PD 5225 polypropylene in Mobilsolg 90. The resulting binder was rubbery with excellent tack and had a pour point in excess of 1500F as shown in Figure 4.

Example 5 Five 200 g quantities of sand were heated to 1800C while stirring. While continuing to stir, about 6.1 - 6.5 wt.% of a binder composition was added to each of the five samples of sand. These binder compositions were: (a) A binder containing 10 wt.% of a polymer combination and 90 wt.% Mobilsolb 90. The polymer combination was a 60 wt.% of DPD 6169 EEA and 40 wt.% of ELVAX 250.

(b) A binder composition containing 10% of a polymer combination and 90% MobilsolE 90. The polymer combination consisted of 55 wt.% of Exxon's PD 5225 and 45 wt.% ELVAX 250.

(c) A binder containing 10.6 wt.% of Dow Chemical's T-4211 chlorinated polyethylene and 89.4 wt.% of MobilsolE 90.

(d) A binder containing 11.3 wt.% of Dow Chemical's T-4211 chlorinated polyethylene and 88.7 wt.% MobilsolS 90.

(e) A commercially produced sand/binder sold under the trade name EQUITRACK.

Each of the five samples were tested for compactibility, heat stability, and rakeability. In testing for compactibility, approximately 50% of the sand-binder mixture was placed in a one and one-half inch diameter closed-ended glass cylinder. The product was lightly tamped down and the pelletized, compacted material was removed. If this pelletized material did not bind together, compaction was deemed inadequate. The binder-sand pellets were then placed in sunlight for a period of 4 hours, during which time ambient temperatures ranged from 85 to 950F. At the end of this period of exposure to sunlight, the temperature of the pellets just below the surface was measured as l430F Each pellet was then tested for clumping and rakeability.

The composition using binder (a) compacted well and did not lose its shape after exposure to sunlight. When the material was spread out, it was not excessively sticky and could be raked without clumping. This property did not change after cooling to 770F.

The composition using binder (b) compacted well and the pellet did not lose its shape after exposure to sunlight. The material could be raked without clumping.

The composition including binder (c) showed very good compactibility and held up well under heat. Under raking conditions while hot, the composition showed no tendency to clump.

The composition using binder (d) produced results similar to that of binder (c) except that the material compacted even firmer. The composition did not become excessively sticky under heat and raking did not cause clumping.

The composition using the commercial EQUITRACK binder showed good compactibility at 770F. However, the surface of the pellet became sticky upon heating in direct sunlight. When the material was spread out and raked, it showed a tendency to clump. The hot product also showed a tendency to stick to the rake. Upon cooling, clumps formed which did not break up upon further raking. The product was not as granular and free-flowing as it had been before the heat testing.

From an analysis of these results, it is readily apparent that the invention product is superior to the currently commercially available product. The invention product is more stable under normal conditions of heating by direct sunlight and provides a rakeable, non-compacting cushion material eminently suitable for use as a racetrack surface composition. Binder levels of 5 wt.% or more may be used to obtain easy pad formation without significant loss of heat resistance, i.e. tendency to become soft which makes pad formation difficult.

The invention has been described with reference to its preferred embodiments. From this description, a person of ordinary skill in the art may appreciate changes that could be made in the invention which do not depart from the scope and spirit of the invention as described above and claimed hereafter.

Claims (12)

WHAT IS CLAIMED IS:

1. A composition useful for racetrack surfaces comprising: (i) a binder comprising: (a) an oil-soluble polymer selected from the soluble copolymers of ethylene with vinyl acetate wherein the vinyl acetate content is from about 20 to about 30 wt.%; (b) an oil dispersible polymer selected from the oil dispersible copolymers of ethylene and propylene; and (c) a hydrocarbon oil, said oil being fluid in temperature range from about 400F to-about 1000F; and (ii) particulate matter comprising sand, clay, or mixtures thereof; wherein the binder composition does not pour readily at temperatures less than about 1259F.

2. The composition of claim 1 wherein said oil-soluble polymer is from about 30 wt.% to about 70 wt.%, and said dispersible polymer is from about 70 wt.% to about 30 wt.% of the total weight of the polymers; the hydrocarbon oil is from about 85 wt.% to about 95 wt.% of the total weight of the polymers and the oil; the binder being from about 3 wt.% to about 12 wt.% of the total weight of the binder and the particulate matter.

3. A composition useful for racetrack surfaces comprising: (i) a binder composition comprising: (a) an elastomeric polymer component comprising chlorinated polyethylene, styrene butadiene, ethylene propylene diene or mixtures thereof; and (b) a hydrocarbon oil, said oil being fluid in the temperature range from about 450F to about 900F; and (ii) particulate matter; wherein said binder composition does not pour readily at temperatures less than about 1300F.

4. The composition of claim 3 wherein said elastomeric polymer component is from about 5 wt.% to about 15 wt.%; the hydrocarbon oil is from about 85 wt.% to about 95 wt.% of the weight of the binder; and the binder is from about 3 wt.% to about 12 wt.S of the total racetrack composition.

5. The composition of claim 3 further comprising a second non-elastomeric polymeric component comprising polypropylene.

6. The composition of claim 5 wherein said second non-elastomeric polymeric component is up to about 70 wt.% of the total weight of the polymers.

7. The composition of claim 3, wherein the elastomeric polymer component comprises a mixture of elastomers.

8. A process for producing a racetrack surface composition comprising: (i) mixing a synthetic polymer or mixture of polymers with a hydrocarbon oil; said oil being a fluid at temperatures from about 400F to about 900F to form a binder that does not pour readily at temperatures below about 1250F; (ii) adding said binder to a particulate material or mixtures thereof to produce a racetrack surface composition.

9. The process of claim 8 wherein said polymers comprise ethylene vinyl acetate, oil dispersible copolymers of ethylene and propylene, chlorinated polyethylene, styrene butadiene, ethylene propylene diene, or mixtures thereof.

10. A method of using the compositions of claims 1, 3 or 5 comprising: (i) raking the composition; and (ii) allowing horses to race upon the composition.

11. A method of making a racetrack surface comprising: (a) producing a pad by laying down at least about 4 inches of the composition of claims 1, 3 or 5; (b) covering the pad with a cushion of the composition of claims 1, 3 or 5.

12. A method of making a racetrack surface comprising: (a) laying down a pad of about 5 inches in thickness of the composition of claims 1, 3 or 5; (b) harrowing the top about 2 inches of the pad to form a cushion.