Fiber for artificial turf   

Abstract: A fiber for artificial turf is of the type of monofilament fibers utilized in the manufacturing of artificial turf carpets and which are obtained by extrusion with polyolefins, in polyethylene or another material. The fiber forming the carpets for artificial turf includes a flat rectangular general cross section with its shorter sides rounded. A central part of one of the longer faces of the fiber includes a curved-convex projection, and its other longer face includes a pair of curved-convex projections in a symmetrical position with respect to its central axis, with which a fiber is obtained for artificial turf with high resilience which facilitates its recovery against successive occasional or temporary loads, maintaining its original appearance for a longer time.

This application is a 371 National Phase of PCT/IB2010/052761 filed on June 18, 2010, and published in English on Mar. 10, 2011, as International Publication No. WO 2011/027235 A1, which claims priority to Spanish Patent Application No. P200930645 filed on Sep. 3, 2009, the entire disclosures of which are incorporated herein by reference.

The following invention, according to what is expressed in the statement of the present specification, relates to a fiber for artificial turf, being of the type of fibers utilized in the manufacturing of artificial turf carpets, by weaving the fibers, such that the essential object is to obtain a fiber with some resilient characteristics which make it recover its vertical position after being compressed, occasionally or temporarily, maintaining its original appearance for a long time.

For that purpose, the extruded monofilament fiber manufactured with polyolefins in polyethylene, has a certain cross section, and the height of the fibers forming the turf carpets present a certain length.

In this manner, the fibers forming the artificial turf carpet are allowed to recover their vertical position after being subjected to successive loads.

In the present specification, a fiber for artificial turf is described, of special application in manufacturing artificial fiber carpets for turf in the installation of fields for different sports, such as soccer, golf, rugby, or hockey.

In the same way, the fiber for artificial turf is equally applied to other uses, such as gardens, access roads, or decoration.

BACKGROUND OF THE INVENTION

As it is known, each day there are more organizations and sports clubs opting to provide their installations, with playing fields for different sports, with artificial turf as an alternative to natural grass turf since they require less maintenance and to offer a sensation similar to the one of natural grass turf and to present improvements, such as, an artificial turf field can be used all year round, and the natural grass turf fields by requiring a recovery period in which they cannot be used. These artificial turf carpets are manufactured by weaving the artificial fibers.

On the other hand, with the object to obtain artificial turf carpets with fibers that maintain their characteristics over time, the monofilament fibers should have high resilience which makes them recover their vertical position after having been occasionally or temporarily compressed over time, preventing the fibers staying tilted over the ground.

In this manner, it has been attempted to obtain fibers made of different materials and sections with the object to provide them with high resilience, being able to consider the patent documents U.S. Pat. No. 6,432,505; EP 1837423, and PCT WO2005/005731.

In this way, in the American patent U.S. Pat. No. 6,432,505, a synthetic turf is described having a substrate and a plurality of turf filaments made of synthetic polymer anchored to the substrate, said filaments having a diamond-shaped cross section, with a longitudinal axis along from one end to another end, and a lateral axis located in the middle, so that the thickness of the filament gradually decreases from said lateral axis, substantially, symmetrically and smoothly over the longitudinal axis toward each end.

In the European patent EP 1837423, a synthetic turf is described comprising a turf carpet and some knots projecting therefrom, the knots comprise individual filament strands and at least one shredded strand and, at least, a number of said strands consists essentially of a mixture of high density polyethylene and low density linear polyethylene.

In the patent PCT WO2005/005731, an artificial turf filament is described wherein the filament has, in cross section, a central area and two wing areas in the opposite sides of said central area, and with a divergent orientation, such that an outward protruding head is formed at one side of the divergent areas of the central area, and at the far side from the divergent areas, the central area, has a face which is essentially aligned in the place of said central area and which is merged to the adjacent faces of each wing area.

SUMMARY

In the present specification, a fiber for artificial turf is described, being of the type of monofilament fibers utilized in the manufacturing of artificial turf carpets, by weaving the fibers and which are obtained by extrusion in polyethylene or another material, such that the fiber for artificial turf presents a flat rectangular cross section with its shorter sides rounded, in the central part of one of its longer faces being provided with a curved-convex projection, and in its other longer face is provided with a pair of projections, equally curved-convex, in a symmetrical position with respect to its central axis.

In a preferred embodiment, the fiber for artificial turf has a width of approximately 1400 μm.

In the same way, in a preferred implementation the fibers for artificial turf which form the carpets have a height of approximately 60 mm.

The thickness of the fiber for artificial turf in the central part of the curved-convex projections is the same for all of them, such that in a preferred implementation the thickness of the fiber for artificial turf in the central part of the curved-convex projections is of approximately 270 μm.

For supplementing the description to be carried out next, and with the object to aid to a better understanding of the characteristics of the invention, a set of drawings is attached to the present specification, with figures where the most characteristic details of the invention are depicted in an illustrative but not limitative manner.

FIG. 1. Shows a perspective view of a segment of a fiber for artificial turf, being able to observe the cross section thereof.

FIG. 2. Shows a detailed perspective view of some weaved fibers forming the corresponding carpet for artificial turf.

FIG. 3. Shows a results table of the recovery index of the fibers, with different cross sections, to be analyzed, with a height of 60 mm, according to the elapsed time of 1, 30 and 240 minutes from its release from a compressive load.

FIG. 4. Shows an evolution table of the fibers in their recovery over time of 1, 30 and 240 minutes after their release from a compressive load, according to the recovery index of the analyzed fibers with a height of 60 mm.

FIG. 5.—Shows a classification table of the analyzed fibers according to a height of 60 mm, according to the elapsed time of 1, 30 and 240 minutes, after their release from a compressive load.

DETAILED DESCRIPTION

Given that the resilience of the fibers forming the carpets for artificial turf is affected by both their section and the height of the fibers forming them, with the object to obtain a fiber for artificial turf with high resilience which facilitates its recovery against successive occasional or temporary loads and maintains its original appearance, a series of samples of fibers of different sections have been analyzed in order to obtain that fiber presenting higher resilience.

In this way, taking into account that both the height of the fibers forming the carpets for artificial turf and its section affect the recovery thereof, i.e. their resilience and utilizing the method described in the Patent of Invention P200930107 wherein a method for determining the recovery grade in artificial fiber carpets is described, an analysis has been carried out in order to assess the recovery of fibers with different sections, for which it determines the recovery index as well as the recovery rate, such that this parameter points out the speed at which a material recovers after being released from a load.

From these premises, four samples of artificial turf carpets have been analyzed, with fibers of different sections being manufactured from monofilament extruded polyethylene, and the fibers forming the carpets have a height of 60 mm, one of the samples being the fiber object of the invention with a certain section which confers it high resilience.

In this way, the section of the fiber object of the invention has been subjected to an analysis together with three more samples of different sections, so that the cross section of the fiber 1 object of the invention (corresponding to the sample of section 3) presents a flat rectangular general shape with its shorter sides rounded, in the central part of one of its longer faces being provided with a curved-convex projection 2, and in its other longer face is provided with a pair of curved-convex projections 3 in a symmetrical position with respect to its central axis.

In this manner, the special section of the sample 3 based on the curved-convex projections of its longer faces confer it with high resilience, in which the height of the fiber forming the artificial turf carpets collaborates.

Moreover, in a preferred implementation of the fiber 1 for forming artificial turf carpets, it has a width “D” of approximately 1400 μm.

On the other hand, the thickness “d” of the fiber for artificial turf in the central part of the curved-convex projections is the same in all of them, such that in a preferred implementation is of approximately 270 μm.

In this way, as observed in FIG. 2 of the designs, fibers 1 forming the weaved bundles of the artificial turf carpet, will have a height preferably of 60 mm, although, logically, the height could be another one.

As in the cited Spanish patent P200930107, the method is specified based on applying to the samples a constant compressive load of 1400 kg during 72 hours, such that, once said time is elapsed, the load is released and images of the same zone are captured after 1, 30 and 240 minutes. Before applying the compressive load, an image has also been taken in order to know and define the total area occupied by the fibers, this value corresponding to 100% of the fibers in their state of equilibrium.

The captured images are analyzed for each one of the times and the area occupied by the fibers is calculated, assigning 100% recovery to the initial area occupied by the fibers before applying the load, such that calculating the recovery index is carried out applying the following ratio

Recovery   index   ( % ) , I t = Area   after   releasing   load   ( mm 2 ) Area   without   load   ( mm 2 ) × 100

In this way, applying the described methodology, the results of the recovery index have been obtained for the carpets formed of some fibers with a height of 60 mm, shown in the table of FIG. 3, after a time of 1, 30 and 240 minutes of being released from the load, being able to observe how the sample of section 3 presents a recovery index of 100% already at 30 minutes of releasing the load.

In the same way, in FIG. 3 of the designs, the evolution of the recovery index is observed in the four analyzed samples at a fiber height of 60 mm, so that once the stationary time (240 minutes) is reached, the recovery considerably increases arriving, in the samples object of the invention, to said value.

In FIG. 4 of the designs, the classification of the result obtained from the four analyzed samples is depicted, being able to observe how the fibers of the sample 3 object of the invention are the ones that recover more, having logically, higher resilience.

Lastly, in FIG. 5 of the designs the evolution of the recovery index of the four analyzed samples is depicted at a fiber height of 60 mm, being able to observe how the sample 3 object of the invention is the one having a greater recovery index.

In this manner, it is concluded that a fiber 1 for forming carpets for artificial turf with a flat rectangular general cross section with its shorter sides rounded, and in the central part of its longer faces provided with a curved-convex projection 2, and in its other longer face provided with a pair of curved-convex projections 3 in a symmetrical position with respect to its central axis, presents high resilience making the fibers forming the artificial turf carpets to recover their vertical position after being subjected to some successive compressive loads and making them to maintain their original aesthetics over time.

In a preferred implementation of the fiber 1 for forming artificial turf carpets, it has a width “D” of approximately 1400 μm.

On the other hand, the thickness “d” of the fiber for artificial turf in the central part of the curved-convex projections is the same for all of them, such that in a preferred implementation is of approximately 270 μm.