Patent Application
20100040808
This invention relates to synthetic fibers and methods for producing synthetic fibers for use in artificial grass sports fields.
Currently, synthetic materials are being used for numerous purposes. For example, the use of various sorts of synthetic materials in artificial lawns for sports fields has markedly increased in recent years.
Research in this regard has concentrated on the development of synthetic fibers for use in artificial lawns for sports fields, in which fibers of a particular length are attached to a substrate, for example, by tufting. The development of artificial grass fibers and artificial grass sports fields derived therefrom has progressed to the point that it is now possible to construct artificial grass sports fields which are very difficult to distinguish from natural grass sports fields, not only with regard to the way they look but also, and in particular, with regard to the way they function during play.
Unlike natural grass sports fields, artificial grass sports fields can be played on longer and more intensively, regardless of the weather conditions. Currently, the development of new artificial grass fibers is particularly focused on obtaining a fiber that will further reduce the incidence of injuries such as grazes and burns caused by sliding or twisted joints.
Existing fibers specifically developed for an artificial grass sports field are obtained from a layer of synthetic material, for example, by means of a cutting operation. The layer of synthetic material may consist of a mixture of different synthetic materials, for example, with one synthetic material serving to give the fiber a certain strength (against breaking or splitting), while another synthetic material in the mixture provides the fiber with a certain elasticity or flexibility or better sliding properties.
A drawback of such existing synthetic fibers is the fact that, due to the homogeneous structure all sub-properties of the fiber are homogeneously incorporated in the fiber. As a result, certain properties of the fiber may be less prominently present than is desirable, while other properties predominate more than is desirable. Therefore, the composition of currently available fibers is usually standardized and often their production and material costs are unnecessarily high.
The present invention provides a method for producing a synthetic fiber for use in an artificial grass sports field, comprising the steps of supplying a layer of synthetic material; and providing or obtaining the synthetic fiber from the layer of synthetic material wherein the layer of synthetic material comprises at least two layers of different synthetic materials using a co-extrusion process.
The invention also provides a synthetic fiber and an artificial lawn suitable for a sports field, including a substrate to which synthetic fibers according to the invention are attached.
Stated another way, the present invention relates to a method of producing a synthetic fiber for use in an artificial grass surface comprising: i) providing a layer of synthetic material comprising at least two layers of different synthetic materials having different function-specific properties; and ii) forming the synthetic fiber therefrom using a co-extrusion process.
Moreover, after step i), the layer of synthetic material can be stretched or, after step ii), the synthetic fiber can be stretched to significantly improve the playing properties of an artificial grass surface including the synthetic fiber.
The present invention provides a more universal fiber, which, on the one hand, can be produced for a specific use and which, on the other hand, saves production and material costs.
The invention disclosed herein is, of course, susceptible to embodiment in many forms. Shown in the drawings and described herein in detail are preferred embodiments of the invention. It is understood, however, that the present disclosure is an exemplification of the principles of the invention and does not limit the invention to the illustrated embodiments.
As will be seen herein, the present invention provides a more universal fiber which, on the one hand, can be produced for a specific use and which, on the other hand, saves production and material costs. According to the invention, the layer of synthetic material comprises at least two layers of different synthetic materials, using a co-extrusion process.
The co-extrusion process accomplishes a separation of the various properties of the synthetic materials that are used. By providing the synthetic fiber with a layered structure, it becomes possible to provide each layer with a function-specific property, which property does not need to be present elsewhere in the fiber, or needs to be present only to a markedly reduced degree. This makes it possible to select the formulation for the fiber specifically for a certain use, which, in addition to a more efficient material consumption, also results in a synthetic fiber with markedly improved playing and fiber properties than in the case of homogeneously composed known fibers.
According to the present invention, the playing properties of the synthetic fiber are significantly improved by stretching the fiber after the co-extrusion process. Apart from an increase in length, according to the invention, the selection of materials is important so that after the stretching process a fiber is provided with such strength properties in a transverse direction that the fiber will split less easily, for example. When used in an artificial grass sports field, such a fiber, and consequently the artificial lawn, has a much longer life, and the artificial lawn requires much less maintenance, thus remaining playable longer. Furthermore, the risk of injury to a player is considerably reduced.
According to the invention, the fiber can comprise at least one monofilament or several twined monofilaments. The fiber can be formed as a band, and more in particular the band fiber can be formed as a fibrillated band fiber.
In a first functional embodiment of the process according to the present invention, the layer of synthetic material comprises a core layer of a first synthetic material having two sides, which core layer is surrounded on both sides by one or several outer layers, each consisting of a different synthetic material.
Thus, a functional separation of the different properties of the different synthetic materials is achieved, in which each layer of synthetic material has a function-specific property, which is not necessary or not functional elsewhere in the fiber.
The layers can have different thicknesses, depending on the desired function-specific properties of the synthetic fiber to be obtained.
In a first embodiment, the first synthetic material comprises a mixture of a polymer and a plastomer, in which preferably the ratio of the plastomer in the core layer is about 30 to about 80 weight percent and more preferably the ratio of the plastomer in the core layer is about 30 to about 50 weight percent. This results in a fiber having a core layer which, from a function-specific viewpoint, exhibits a very favorable non-splitting behavior.
In another embodiment, at least one of the other synthetic materials includes a hydrophilic additive. The artificial grass fiber thus obtained has the function-specific characteristic that it can absorb moisture (water). This keeps the artificial grass sports field moist longer, which has a positive effect on playing behavior (slides etc.). When the field is played on, the absorbed moisture is released, the same as with natural grass.
An example of a hydrophilic additive that can be used as the top layer or outer layer of the co-extrusion fiber is ethylene vinyl alcohol copolymer. Depending on the quantity of vinyl alcohol in the copolymer, this polymer is capable of absorbing a considerable amount of water.
Another embodiment of a hydrophilic additive is polyhydroxyethyl methylacrylate.
In yet another embodiment, at least one of the other synthetic materials can comprise an antistatic additive. As a result, any static electricity generated when the field is played on can discharge. Usually, the material spread or strewn between the fibers, which is used in many artificial grass sports fields, is statically charged during play and as a result migrates upwards in the field. Thus, the granular strewing material can be spread through the air, which is less pleasant during play.
The antistatic additive also ensures that no static discharges will take place via the players.
More specifically, the antistatic additive can be a polymer, especially a permanent antistatic agent, such as a polyamide or a polyether block amide. In another embodiment, the additive is a polyester block copolymer.
The invention will now be explained in more detail with reference to the drawings, in which:
The fibers (10, 20, 30, 40) are obtained from a foil of a synthetic material, which foil, obtained by co-extrusion, comprises at least two layers of different synthetic materials (11, 12) as shown in
For example, it is possible to use a synthetic material for the sub-layer 11 which provides the synthetic fiber with the required mechanical strength (and rigidity) and, in particular, non-splitting properties such that the synthetic fiber used for the artificial grass sports field will not split as a result of being played on.
In another embodiment as shown in
Thus, the outer layers 21 and 22 can have an elastic property, for example, contrary to the inner layer 21, which provides the fiber with a certain rigidity (against breaking or splitting), which elastic property of the outer layer 21 or 22 has a positive effect on the playing properties of the artificial grass sports field.
Whereas in the embodiment of
The essence of the method according to the invention and the synthetic fibers according to the invention obtained thereby lie in the fact that the synthetic fiber, contrary to the known synthetic fibers, does not have a homogeneous structure in which all different synthetic materials and the related properties are homogeneously incorporated in the fiber. As a result of the homogeneous structure or composition of the existing artificial grass sports fields, certain properties of the fiber may be present less prominently than is desirable, whereas other properties are more predominantly present than desired.
Using the method according to the invention, it is possible to obtain synthetic fibers according to a specific formulation that, contrary to standardized fibers, exhibit a function-specific property in certain parts of the fiber that is not considered necessary or desirable elsewhere in the fiber.
This enables a more efficient use of the various (synthetic) materials, which not only serves to reduce costs but also provides a more universal synthetic fiber according to the invention having markedly improved playing and fiber properties than in the homogeneously constructed known fibers. In this specific embodiment, the inner layers 11, 21, 31 and 41 are made of a more inexpensive synthetic material that in principle provides the fiber with a certain strength against breaking or splitting. The outer layers 12, 22, 32, 32a-32b, 42a-42b and 43a-43b are made of a synthetic material that does not necessarily need to be present in the fiber core.
In this context, a specific embodiment can have an outer layer including an antistatic additive. The antistatic additive prevents the fiber from being charged by means of static electricity generated as a result of the artificial grass sports field being played on. On the other hand, the antistatic additive precisely ensures that the generated static electricity can discharge from the artificial grass sports field and, for example, will not discharge via the players, which can lead to unpleasant experiences.
In addition, in most artificial grass sports fields a strewing material (usually made of a rubber-like material) is used, which, due to the static electricity that is generated, migrates upward in the artificial grass sports field and which is spread through the air as a result of the field being played on. The airborne strewing material has a disturbing effect on the players.
The antistatic additive in particular comprises a permanent antistatic agent, for example, a polymer, such as a polyamide or polyether block amide. In another embodiment, the additive is a polyester block copolymer.
In another embodiment, one of the outer layers (or both outer layers) (12, 22-23, 32a-32b, 43a-43b) can comprise a hydrophilic additive. The artificial grass fiber thus obtained has the function-specific characteristic that it can absorb moisture (water) from the atmosphere, such as rain. This allows the artificial grass sports field to remain moist longer, just like a natural-lawn sports field, which has a positive effect on the playing behavior in particular when sliding, etc. While the field is being played on, the absorbed moisture is released, the same as with natural grass.
An example of a hydrophilic additive that can be used as the top layer or outer layer (12, 22-23, 32a-32b, 43a-43b) of the co-extrusion fiber is ethylene vinyl alcohol copolymer. Depending on the quantity of vinyl alcohol in the copolymer, this copolymer can absorb a significant amount of water.
The middle layer (11, 21, 31, 41) in this example gives the fiber its strength, while the relatively thin top layer (12, 22-23, 32a-32b, 43a-43b) absorbs water. This water can be absorbed from the air (in the form of rain, fog, etc.) or can be supplied by an active sprinkler installation. (Often, artificial grass sports fields are sprinkled just before they are played on.)
During play, the absorbed water is released again, which reduces the risk of injury, for example when sliding. Furthermore, the absorbed water keeps the temperature of the field lower, since an artificial grass sports field can be heated by the sun, under adverse conditions to temperatures as high as 70° C.
Another embodiment of a hydrophilic additive as the outer layer (12, 22-23, 32a-32b, 43a-43b) uses polyhydroxyethyl methacrylate. In order to prevent bonding problems to the middle layer (11, 21, 31, 41), a five-layer co-extrusion configuration is required, as shown in
For illustration purposes, the various layers of the artificial grass fiber (as shown in
In the embodiment shown in
In another embodiment, as shown in
The foregoing description and the accompanying drawings are illustrative of the present invention. Still other variations in arrangements of materials and components are possible without departing from the spirit and scope of this invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1026239 | May 2004 | NL | national |
This application claims priority based on Netherlands Application No. 1026239 filed on May 19, 2004 and is the National Stage of International Application No. PCT/NL2005/000275 filed on Apr. 11, 2005, which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/NL2005/000275 | 4/11/2005 | WO | 00 | 1/9/2008 |
