NL1033949C2 - Artificial grass constructed from fibers consisting of a core and a mantle, as well as an artificial grass field built from it. - Google Patents

Description

Brief indication: Artificial grass made from fibers that consist of a core and a sheath, as well as an artificial grass field built from it.

The present invention relates to artificial grass 5 constructed from fibers consisting of a core and a jacket, the core and the jacket being composed of different materials. The present invention furthermore relates to a method for manufacturing such artificial grass fibers.

Such a type of artificial grass is known per se from European patent EP 0 996 781, granted in the name of the present applicant, in which a polyamide-containing yarn is used for the manufacture of artificial grass, wherein the yarn, in addition to polyamide, also comprises a polyolefin compound contains selected from the group consisting of polypropylene, LLDPE and a block copolymer of polypropylene and polyethylene. In addition to the method of manufacturing a yarn known therefrom, in which the polymer is extruded to form monofilaments, which are subsequently further processed into strips, wherein a number of strips are twisted to form a yarn, a method has also been disclosed wherein yarn is obtained by co-extrusion. During such a co-extrusion the jacket consists of polyamide, while the core 20 consists of one of the aforementioned plastics.

From the international application WO 2004/106601 a yarn for an artificial grass field is known, wherein the yarn is a so-called tape filament, consisting of a core layer and two outer layers of a material other than the core layer, wherein the core layer contains polyester and / or polyolefin material and the 25 outer layers contain high density polyethylene.

Japanese patent publication JP 2003 342848 discloses a yarn for an artificial grass field consisting of a conjugated yarn composed of a resin composition comprising 70-99% by weight of nylon (polyamide) and 1-30% by weight of polyethylene, as the inner layer, and polyethylene as the outer layer.

A phenomenon known to artificial grass, in particular when the artificial grass is used for playing football, is the occurrence of burns when the players make a sliding. This problem does not occur with natural grass, which natural material has a high water content and feels soft on contact, so that the friction with the skin will be high. This high friction 1033949 2 is disadvantageous from the point of view of damaging the skin, but due to the fact that natural grass will wear off slightly after contact, there is no question of burns in the contact between the skin and the natural grass. In addition, it can be reported that natural grass is soft and, after abrasion, will grow again, and it can furthermore be noted that the relatively soft nature of natural grass also contributes to good resilient or resiliency properties.

On the other hand, the choice of materials used for artificial grass is generally controversial. The material used for the artificial grass is, for example, a soft material that has access to a large elastic range. Such a property results in good resilience, but also in a high degree of friction, the latter aspect of which will lead to an excessive adhesion of the skin to the artificial grass when a sliding is carried out, and thus to unavoidable damage to the skin, which is undesirable. In the field of heat development with such a sliding, these materials are assessed as poor, despite the fact that the contact time between the skin and the artificial grass is limited due to the high degree of friction. The material used for the artificial grass can also be a hard material that has a small elastic range, which results in poor resilient properties, but where the friction is limited, however. The limitation in the area of friction will reduce skin damage. In addition, these hard materials are assessed as good in the area of heat development during sliding because the contact time is longer.

The aforementioned artificial grass pitches have been known for many years, with hockey being one of the most frequently practiced sports on artificial grass. Football, rugby, tennis, skiing and golf can also be mentioned here.

In order to avoid the aforementioned problems in the field of human skin-field interaction, large amounts of water are applied to the artificial grass field on a large scale, in particular during important sports competitions. With artificial grass fields for practicing hockey sport, the artificial grass field is thus almost completely submerged in water, which is undesirable from an environmental point of view.

An object of the present invention is to provide a special type of artificial grass that imitates the favorable properties of natural grass, in particular in the field of resilience and sliding, as much as possible.

3

Another object of the present invention is to provide an artificial grass that has high durability and can be assembled from commercially available materials.

Another object of the present invention is to provide an artificial grass fiber that lacks the necessity to flood the artificial grass field.

The present invention as stated in the preamble is characterized in that the material for the jacket has a hydrophilicity that differs from the hydrophilicity of the material used for the core, in particular that the material for the jacket has a hydrophilicity that is higher then the hydrophilicity of the material used for the core.

Using such a type of artificial grass, the artificial grass will exhibit some degree of moisture absorption, whereby one or more of the aforementioned objectives are met. Because the artificial grass according to the present invention feels somewhat moist, when practicing a ball game, in particular hockey, the ball will easily roll over the field. Moreover, in the case of contact sports, in particular football, the chance of adverse injuries after, for example, sliding has been made, will be limited to a minimum.

The present inventors have found that the material for the sheath is preferably selected from the group of polyurethane, cellulose, chitosan, polyvinyl alcohol and derivatives thereof, or a combination thereof, in particular one or more derivatives of cellulose belonging to the group of viscose, cellulose (di) acetate and cellulose (tri) acetate have been used. Chitosan is a linear polysaccharide and is obtained from chitin. A particular advantage of chitosan is that it exhibits good adhesion to the core material and also has antibacterial properties.

As a suitable material for the core, there can be mentioned a material selected from the group of polyesters, polypropylene, ethyl vinyl acetate (EVA), saturated styrene thermoplastic elastomer (SEBS), polyamides, polyethylene compounds and copolymers of ethylene and acrylate, or combinations thereof. Particularly suitable polyethylene compounds are selected from the group of high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and anhydride modified polyolefins, in particular polypropylene compounds and 4 polyethylene compounds . Suitable suitable polyamides are polyamides of the type 6, 6.6, 6.10 and 6.12. Suitable polyesters are polybutylene terephthalate and polyethylene terephthalate.

In a special embodiment it is desirable that there is a means between the material for the core and the material for the jacket that promotes the adhesion between the material for the core and the material for the jacket, wherein in a special embodiment it holds that the adhesion promoter is a copolymer of ethylene and methyl acrylate.

Particularly suitable embodiments of the present artificial grass are formed by a combination of polyamide (core) and cellulose (tri) diacetate (jacket), LDPE (core) and cellulose (tri / di) acetate (jacket), polypropylene with SEBS ( core) and cellulose (tri / di) acetate (jacket). Another suitable material for the core is the material which, in addition to EVA, also contains copolymers of ethylene and acrylate, polypropylene and / or polyethylene, or combinations thereof.

The material for the core, as used in the present artificial grass fiber, in particular has an elastic modulus (measured according to ASTM D638) of at most 500 MPa, in particular an elastic modulus (measured according to ASTM D638) of at most 300 MPa.

The material for the jacket preferably has an elasticity modulus (measured according to ASTM D638) of at least 500 MPa, in particular an elasticity modulus (measured according to ASTM D638) of at least 750 MPa.

In the present artificial grass, constructed from fibers consisting of a core of a plastic material and a sheath, it is preferable that the thickness of the sheath be a volume share in the range of 1-40% by volume, based on the whole fiber.

Although in the present description of the description it has always been referred to as a jacket, it is also possible in a particular embodiment for the jacket to comprise a number of (sub) layers, wherein at least one of the layers comprises a material selected from the group consisting of polyurethane, cellulose, chitosan, polyvinyl alcohol and derivatives thereof, or a combination thereof, wherein it is particularly preferred that for the outer clad layer one or more derivatives of cellulose belong to the group of viscose, cellulose (di) acetate and cellulose (tri) acetate applied.

According to the present inventors, it is possible to manufacture the present artificial grass in a number of ways. A possible way is the first dissolving, if possible, of the jacket material, after which the solution thus obtained is applied to the core material, whereafter the solvent used thereby is removed, whereby the material for the core 5 can be activated in advance.

Another possibility is to use a co-extrusion process, the condition being that the material for the jacket must be meltable and therefore extrudable. In addition, it is possible to use a combined chemical / extrusion process in which the core material, optionally pre-activated with, for example, fumaric acid dissolved in ethanol, is covered with the material for the jacket.

Although in the present application it is always referred to that a casing is applied to a core of a plastic material, in a special embodiment it is also possible to use a material whose hydrophilicity is higher for the usual filling material or infill applied to an artificial grass field. is then the hydrophilicity of the material, in particular the outer layer thereof, which has been used for the production of the artificial grass fibers.

In a particular embodiment of the present application it is also possible to hydrophilize the material for the core so as to improve adhesion with water, or to improve the interaction with the (yet to be applied) hydrophilic sheath. The hydrophilization is preferably carried out by digging one or more reactive groups on the core material, for example maleic anhydride on a polyethylene core, in particular LDPE and LLDPE.

The material used for the jacket can also contain one or more additives, such as, for example, additives that promote the absorption and release of moisture, additives that adversely affect the growth of algae and / or fungi, additives that influence the elasticity of the artificial grass fiber as such. , additives that achieve UV resistance, additives that influence the rolling resistance of the fiber, additives that provide a color to the fiber.

The present invention further relates to a method for manufacturing an artificial grass fiber consisting of a core of a plastic material and a jacket, wherein the core and the jacket are composed of different materials, as stated in the appended claims.

The present invention will be explained below with reference to a number of examples, but it should be noted, however, that the present invention is by no means limited to such special examples.

Example 1

Polyamide 6 was extruded, the core material thus obtained, as bands or monofilaments, being additionally washed with warm water to remove the so-called spin finish. The core material thus extruded was subsequently passed through a bath with a solution of an adhesion promoter, using a solution of fumaric acid, in particular 1 - 2% fumaric acid in an azeotropic mixture of ethanol with water, with a residence time lying in the 10-30 seconds. Another suitable adhesion promoter is terephthalic acid. After the aforementioned activation was carried out, a commercially available viscose rayon was applied using a so-called coating spinneret. After the aforementioned coating step, a coagulation was carried out, namely the guiding of the material thus obtained through a coagulation bath, in particular an aqueous composition containing 9% by weight of sulfuric acid and 13% by weight of sodium sulphate, the viscose being regenerated and therefore converted into cellulose. The core material thus provided with the jacket layer was dried and possibly washed with water. The artificial grass fiber thus obtained can be described as a fiber that contains a highly resilient core and a very thin sheath that is hydrophilic and provides an improvement in the field of sliding interaction compared to a commercially available artificial grass fiber that does not have a sheath that exhibits a hydrophilicity different from the hydrophilicity of the material used for the core.

Example 2 The same starting material for the core as mentioned in example 1 was used, wherein, after washing with hot water to remove the spin finish, the extruded material was passed through a bath containing a solution of the jacket material to be applied . Suitable coating materials may be: cellulose (di) acetate, dissolved in cold acetone, cellulose (tri) acetate, dissolved in cold methylene chloride and polyvinyl alcohol, dissolved in cold 6N hydrochloric acid. The two first-mentioned jacket materials are preferred because of the good adhesion with polyamide. Furthermore, the core materials thus provided with a sheathing material can be air-dried in a simple manner because the solvents used have a low boiling point. The artificial grass fiber obtained with example 2 contains a highly resilient core, on which core there is a thin sheath that is hydrophilic, so that the sliding interaction shows a clear improvement with respect to an artificial grass fiber that does not have the above-mentioned sheath material.

Example 3

The core material used was polyamide 6.6, whereby the jacket material to be processed by means of co-extrusion must be meltable, using cellulose (di) acetate, cellulose (tri) acetate and polyvinyl alcohol. The shell material was applied to the core material by co-extrusion. An advantage of the aforementioned co-extrusion is that the use of (harmful) solvents is avoided, in addition to the possibility that the material for the core and the material for the sheath in the contact zone can mix slightly with each other, whereby the adhesion between the two materials is promoted. . The fiber thus obtained contains a highly resilient core and a hydrophilic sheath, which entails an improvement in the field of sliding interaction with respect to artificial grass fibers without a hydrophilic outer layer.

Example 4

The core material extruded in Example 1 was used, the core material obtained as filaments being immersed for a long time, at most 24 hours, in a 1 N hydrogen chloride (HCl) solution to effect a partial hydrolysis of the amide functions in the polyamide . The filaments thus treated were repeatedly washed with water before being exposed to an aqueous solution containing 9 parts by volume of di-epoxybutane, 1 part by volume of ethanol and 1 part by volume of sodium carbonate (0.025 M in water). Exposure was at a temperature of 80 ° C for 15 hours. After the aforementioned treatment, the filaments thus treated were washed with water and dried in air, after which the activated filaments were contacted with an aqueous solution (1.8% by volume of acetic acid) containing 1.5% of chitosan, in particular by the filaments through the by drawing an aqueous solution, or by spraying the aqueous solution onto the filaments. Finally, the filaments were dried for one hour to allow the chitosan to further react with the polyamide. The fiber thus obtained, consisting of a polyamide core and a chitosan cladding layer, can be considered as a fiber which comprises a highly resilient core provided with a thin, hydrophilic cladding, which fiber exhibits a clear improvement in sliding interaction compared to of an artificial grass fiber that does not have the aforementioned combination of jacket and core material. It can further be noted that chitosan as an overlay layer exhibits an antibacterial effect and inhibits the growth of algae.

Example 5

The same operations as mentioned in Examples 1-3 were used, except that always a polyethylene compound was used as the core material, in particular LDPE and LLDPE. The fiber thus obtained contains a highly resilient core and a hydrophilic sheath, which entails an improvement in the field of sliding interaction with respect to artificial grass fibers without a hydrophilic outer layer. The core materials used in this example can also be modified, as described below in Examples 6-8, to obtain a particularly good adhesion with the jacket material.

Example 6

An extruded core material of the polyethylene type, in particular LDPE and LLDPE, or polypropylene was hydrophilized by "grafting" a reactive group, in particular maleic anhydride, on the hydrophobic polymer chains. The polymer was dissolved in a suitable solvent, for example o-dichlorobenzene, and then a suitable initiator, for example tertiary butyl peroxide, 10% by weight based on the polymer, and maleic anhydride, 1% by weight relative to the polymer, were mixed in. After heating for 1 hour at a temperature of 170 ° C. under an atmosphere of nitrogen, the reaction product was purified by precipitation in boiling acetone. Said purification step was repeated twice. The product obtained is a polymer chain of which about 0.05% of the carbon atoms present have a hydrophilic group. If desired, the grafts thus applied can be hydrolyzed by maintaining the resulting filaments in boiling water for about 10 minutes. By the aforementioned hydrolysis, the anhydride functions present will be converted into carboxyl functions, which results in a lower contact angle with water, resulting in a strong adhesion of water.

Example 7

A polyethylene compound, in particular LDPE, was extruded in a twin screw extruder in the presence of 1% by weight maleic anhydride and a suitable initiator, for example 0.15% by weight dicumyl peroxide, at a temperature of about 200 ° C under an atmosphere of nitrogen. Using a residence time of about 5 minutes, 60% of the maleic anhydride thus added was grafted on the carbon chain. The filaments thus obtained can be hydrolyzed by maintaining the material in boiling water for about 10 minutes. By the aforementioned hydrolysis the anhydride functions present will be converted into carboxyl functions, whereby a strong adhesion of water is obtained.

Example 8

A polyethylene compound, in particular LDPE, was extruded and the filaments thus obtained were contacted with a solution of the following composition: 20-maleic anhydride, preferably 2 to 3% by weight, based on the polymer, photo-initiator , preferably 3-6% by weight relative to the anhydride, with suitable photoinitiators being benzophenone, benzoyldimethyldital and thioxanthan, preferably benzophenone, solvent such as acetone or ethyl acetate, acetone being preferred.

After the filaments were wetted with the aforementioned solution, a treatment with UV radiation was carried out. The treatment thus applied consisted of exposure to a UV lamp for 1 to 7 minutes which also emits radiation in the wavelength range of 200-300 nm, with an intensity of 2500-6000 pW / cm 2 and a temperature in the range of 35 -85 ° C, with a temperature above 60 ° C being preferred because maleic anhydride will melt and thus be able to react better. Using the aforementioned UV-action, it was found by the present inventors that 70-90% of the added maleic anhydride on the carbon chain was taken. After photographing is finished, it is possible to remove the unreacted reagents by rinsing with acetone followed by water. In addition, it was possible to hydrolyze the grafts thus applied by maintaining the filaments 5 in boiling water for a period of about 10 minutes, whereby the anhydride functions present were converted into carboxyl functions, resulting in a strong adhesion with water.

The present inventors have found that the hydrolysis step mentioned in the aforementioned Examples 5-8 is omitted when a jacket material is subsequently to be applied. In particular, the hydrolysis step is carried out when no sheathing is applied to the core material. The aforementioned Examples 5-8 result in an artificial grass fiber containing a highly resilient core, the grafts as such already being considered as a hydrophilic sheath on the core material, whereby it is also possible to still apply a hydrophilic sheath to the thus modified core material. as described in Examples 1-4, thereby further improving the sliding interaction.

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Claims (23)

1. Artificial grass composed of fibers consisting of a core of a plastic material and a jacket, the core and the jacket being composed of different materials, characterized in that the material for the jacket has a hydrophilicity that differs from the hydrophilicity of the material used for the core. 2. Artificial grass according to claim 1, characterized in that the material for the jacket has a hydrophilicity that is higher than the hydrophilicity of the material used for the core. Artificial grass according to one or more of claims 1-2, characterized in that the material for the jacket is selected from the group consisting of polyurethane, cellulose, chitosan, polyvinyl alcohol and derivatives thereof, or a combination thereof. Artificial grass according to claim 3, characterized in that one or more derivatives of cellulose belonging to the group of viscose, cellulose (di) acetate and cellulose (tri) acetate are used. Artificial grass according to one or more of the preceding claims, characterized in that the material for the core is selected from the group consisting of polyesters, polypropylene, ethyl vinyl acetate (EVA), saturated styrene, thermoplastic elastomer (SEBS), polyamides, polyethylene compounds and copolymers of ethylene and acrylate, or combinations thereof. 6. Artificial grass according to claim 5, characterized in that the polyethylene compounds are selected from the group of high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and anhydride modified polyolefins, in particular polypropylene compounds and polyethylene compounds. 7. Artificial grass according to one or more of the preceding claims, characterized in that there is a means between the material for the core and the material for the jacket that promotes the adhesion between the material for the core and the material for the jacket . The artificial grass according to one or more of claims 1-7, characterized in that the material for the core is polyamide and the material for the jacket is cellulose (tri / di) acetate. 1033949 The artificial grass according to one or more of claims 1-7, characterized in that the material for the core is LDPE and the material for the jacket is cellulose (tri / di) acetate. 10. Artificial grass according to one or more of claims 1-7, characterized in that the material for the core is a combination of polypropylene with SEBS and the material for the cellulose (tri / di) acetate jacket. 11. Artificial grass according to one or more of claims 1-7, characterized in that the material for the core also contains copolymers of ethylene and acrylate, polypropylene and / or polyethylene, or combinations thereof, in addition to EVA. Artificial grass according to one or more of the preceding claims, characterized in that the material for the core has an elastic modulus (measured according to ASTM D638) of at most 500 MPa. 13. Artificial grass according to claim 12, characterized in that the material for the core has an elastic modulus (measured according to ASTM D638) of at most 300 MPa. Artificial grass according to one or more of the preceding claims, characterized in that the material for the jacket has an elastic modulus (measured according to ASTM D638) of at least 500 MPa. Artificial grass according to claim 14, characterized in that the material 20 for the jacket has an elastic modulus (measured according to ASTM D638) of at least 750 MPa. Artificial grass according to one or more of the preceding claims, characterized in that the thickness of the casing has a volume share in the range 1 - 40 volume%, based on the entire fiber. The artificial grass according to claim 7, characterized in that the adhesion promoter is a copolymer of ethylene and methyl acrylate. 18. Artificial grass according to one or more of the preceding claims, characterized in that the jacket comprises a number of layers, at least one of the layers of which comprises a material selected from the group consisting of polyurethane, cellulose, chitosan, polyvinyl alcohol and derivatives thereof , or a combination of these. Artificial grass according to claim 18, characterized in that one or more derivatives of cellulose belonging to the group of viscose, cellulose (di) acetate and cellulose (tri) acetate are used for the outermost layer layer. A method of manufacturing an artificial grass fiber consisting of a core of a plastic material and a sheath, the core and the sheath being composed of different materials, characterized in that the material is extruded for the core to obtain extruded core material, the material for the sheath being applied to the extruded core material. A method according to claim 20, characterized in that the material for the sheathing is applied by passing the extruded core material through a bath of the sheathing material to be applied. 22. Method as claimed in claim 20, characterized in that the material for the casing is applied by extruding the material for the core and the material for the casing simultaneously. 23. Method as claimed in one or more of the claims 20-21, characterized in that the extruded core material is first provided with an adhesion-promoting agent, whereafter the material for the sheath is applied to the core material thus pretreated. 20 10339 49