The present invention relates to slides for sport or play, for example for skating or other activity requiring low friction so as to facilitate sliding or gliding.
Presently sport or play activities requiring a low friction support, for example skating, takes place on artificial skating grounds or on natural ice. Artificial ice grounds involve high investment costs, and solely the cooling plant for a conventional ice ground amounts presently to several million SEK. To this comes high operational costs which for cooling only are estimated to about half a million SEK per year. The season for a conventional artificial ice ground is often not more than about seven months, and during periods with high daytime temperatures it is often uneconomical. An artificial skating ground is furthermore restricted to a specific geographic location and is thus useful only at the site where the cooling tubes are cast into the support.
Another inconvenience with artificial ice grounds is the fact that the cooling equipment uses cooling media containing ammonia and water containing salts. The ammonia will have to be replaced at frequent intervals and the waste is considered as an environmental hazard and must be especially treated according to the environmental laws.
Furthermore, the usefulness of today's artificial ice grounds is very limited. When the outdoor temperature exceeds about 10°C artificial ice grounds function only indoors within an enclosure. This, however, results in very high operational costs. In practice an iceground can be used only if the surface of the ice has a temperature of between about -1°C and -20°C. In countries having a high average temperature skating is virtually impossible to practice.
As prior art reference is made to DE-A-3 445 976 and US-A-3,726,817 which disclose slides based on wax and polymer but which do not suggest the presence of any crack resistance-imparting mineral.
The present invention has for an object to provide slides for sport and play which involve essentially reduced investment and operational costs and furthermore are capable of operation within a much broader temperature range. Another object of the invention is to provide slides which are easy to restore and the friction coefficient and surface hardness of which can be modified according to the activity involved. Still another object of the invention is to provide slides which show improved non-cracking characeristics.
For these and other objects which will be clear from the following description the invention provides for a slide for sport or play, comprising a surface layer that has been formed by the solidification of a melted mixture based on a wax and a polymer, characterized in that said mixture comprises more than 40% by weight of said wax in the form of a natural and/or synthetic hard wax, 5-30% by weight of said polymer, and 5-40% by weight of a crack resistance-imparting mineral, said percentages being based on the weight of the total composition.
Thus, the slide according to the invention does not require energy consuming cooling and the surface may thus have the environmental temperature which can vary between wide limits, for example from -20°C to +50°C. In this manner it is possible to avoid the inconvenience caused by a cold ice surface in the form of the chill that the sport practitioners are subjected to.
The surface of the slide has suitably a hardness of from about 0 to 15 measured using needle penetration according to DIN 51579 or Norm ASTM 1321 at +20°C.
In a preferred embodiment of the invention the mixture has a melting point of from about 80 to about 180°C, preferably from about 90 to about 140°C, especially from about 100 to about 130°C.
The hard wax used in the composition or mixture according to the invention is the major component thereof, which generally means that the weight percentage thereof is greater than the weight percentage of any of the other components or ingredients of the mixture. This means that said hard wax comprises more than 40, often more than 50, % by weight of the total composition or mixture.
A multitude of hard waxes are useful in the invention, and a suitable wax can be selected among technique waxes, microwaxes, synthetic waxes, especially polyethylene waxes, and paraffin waxes, including mixtures thereof.
For the purpose of modifying the properties of the wax, especially increasing the homogeneity of binding and also increasing the hardness of the surface of the slide, the hard wax is admixed with a polymer material in an amount of 5-30% by weight.
Such polymer material is suitably in the form of powders, granulates or dust, and preferable types of materials are polyethylene, polypropylene, nylon and similar and of course mixtures thereof.
Especially in order to have a crack-resistant surface of the slide claimed the mixture contains as a third ingredient at least one mineral in an amount of 5-40% by weight.
Said mineral is preferably selected from the group consisting of talcum and mica, including mixtures thereof. For the purpose of the invention, however, said third ingredient need not necessarily be a natural mineral or inorganic compound. Rather it may well be any synthetic equivalent of such a mineral ocurring in nature, such as an inorganic compound in the form of an oxide, phosphate, carbonate and/or hydrate.
In order to further reduce the friction and to improve the wear characteristics of the slide the mixture may also contain friction and wear reducing additives, especially of a lamellar molecular structure, in an amount of up to 10% by weight, preferably 0,1 - 10% by weight, especially 2 - 10% by weight, based on the total composition.
Said additives are preferably selected from the group consisting of molybden disulphide, graphite, boron nitride and cerium trifluoride.
It is preferred that the viscosity of the mixture at 140°C is from about 1000 to 100000, especially 2000 to 50000 centiStoke (cSt).
It may also be suitable to add to the mixture stabilizing additives, such as UV-stabilizers, anti-oxidants etc. Such additives are of a conventional kind and do not require further detailed description.
The advantages associated with the slide according to the present invention is the fact that the surface thereof may be easily restored by using equipment that is passed across the surface with heating to melt the uppermost surface layer, often not more than about 1 mm, of the slide. The slide according to the invention can also be used anywhere and thus also in countries having a high round-the-year temperature.
The slide according to the present invention has a versatile use and can be used i.a. as a slide for hockey, bandy, curling, and as minor playgrounds for skating. The slide according to the invention can be used also for cross-country skating, as slides for sliding, bob sleighing, tobogganing, etc.
It is preferred to use in the slide according to the invention such a composition of the mixture that the coefficient of expansion from liquid to solid form is as close to zero as possible, in order that possible cracking in the restoration of the surface by melting of the surface layer shall be eliminated.
The invention will now be further described by exemplifying embodiments, but it should be noted that the invention is not limited to these specific embodiments and that its scope is defined only in the appended patent claims.
The following four ingredients were used to prepare two different slides having properties similar to ice.
The hard wax 1 is melted above 120°C. The polymer 2 as well as the mineral 3 are combined with the wax, with stirring, when the temperature reaches about 160°C. The weight percentages of 1, 2 and 3 are 55%, 20% and 25%, respectively. The stirring is maintained for at least 10 minutes. The molten mixture is poured into molds for solidification in the shape of plates. Said plates are melted together into a continuous slide having outstanding properties similar to those of ice.
The procedure from Example 1 is repeated while reducing the percentage of the mineral 3 to 20% and adding the additive 4 as a fourth ingredient at a percentage of 5%. The slide obtained possesses characteristics similar to those of Example 1 and with even lower friction.