Artificial turf with marbled monofilament

Abstract

A method of manufacturing artificial turf creating a liquid polymer mixture, wherein the polymer mixture is at least a two-phase system. A first one of the phases includes a first polymer and a first dye, and a second one of the phases of the polymer mixture includes a second polymer and a second dye. The second dye has a different color than the first dye, the second polymer being of the same or of a different type as the first polymer. The first and the second phase are immiscible, the first phase forming polymer beads within the second phase. The method further includes extruding the polymer mixture into a monofilament including a marbled pattern of the first and second color; quenching the monofilament; reheating the monofilament; stretching the reheated monofilament to deform the polymer beads into threadlike regions and to form the monofilament into an artificial turf fiber; and incorporating the artificial turf fiber into an artificial turf backing.

Claims

1. A method of manufacturing artificial turf, the method comprising the steps of: creating a liquid polymer mixture, wherein the polymer mixture is a two-phase system, the polymer mixture not including a compatibilizer, a first one of the phases comprising a first polymer and a first dye, a second one of the phases of the polymer mixture comprising a second polymer and a second dye, the second dye having a different color than the first dye, the first and the second phase being immiscible, the first phase forming polymer beads within the second phase, wherein a phase separation of the first and the second phase is achieved by selecting the first and the second polymer such that the difference in melt mass-flow rate of the first and second polymer results in a phase separation of a molten mixture of the first and second polymer, wherein the first polymer is a first linear low-density polyethylene (LLDPE) having a first melt mass flow rate, wherein the second polymer is a second LLDPE having a second melt mass flow rate different from the first melt mass flow rate, wherein the first LLDPE and the second LLDPE have different molecular weights, wherein the first LLDPE has a smaller mass share of the polymer mixture and the second LLDPE has a larger share of the polymer mixture, and wherein the first melt mass flow rate (190° C/2.16 kg) is 0.5-5 g/10 min and the second melt mass flow rate (190° C/2.16 kg) is 8-100 g/10 min; extruding the polymer mixture into a monofilament comprising a marbled pattern of the first and second color; quenching the monofilament; reheating the monofilament; stretching the reheated monofilament to deform the polymer beads into a form of threadlike regions and to form the monofilament into an artificial turf fiber; incorporating the artificial turf fiber into an artificial turf backing, wherein the creation of the liquid polymer mixture comprises heating the polymer mixture to reach at the time of extrusion a temperature of 190-260° C., and wherein the quenching is performed in a quenching solution having a temperature of 10-60° C., wherein in the marble pattern of the monofilament the occurrence of the two different first and second colors changes every 50-1000 μm.

2. The method of claim 1, wherein one of the first and the second polymers is a polar polymer and the other one is an apolar polymer and wherein the first and second polymers are chosen such that the polarity difference of the polar and the apolar polymer results in the phase separation of the first and second phase.

3. The method of claim 1, wherein the second polymer is a non-polar polymer and/or wherein the first polymer is a polar polymer.

4. The method of claim 1, wherein the polymer beads comprises crystalline portions and amorphous portions, wherein stretching the polymer beads into the form of threadlike regions causes an increase in the size of the crystalline portions relative to the amorphous portions.

5. The method of claim 1, wherein the creation of the polymer mixture comprises the steps of: forming a first mixture comprising the first polymer; heating the first mixture; extruding the first mixture having a predefined shape or a predefined size, wherein a size of the polymer beads is based upon the predefined size or the predefined shape of the extruded first mixture; granulating the extruded first mixture; mixing the granulated first mixture with the second polymer, the second polymer being not granulated; and heating the granulated first mixture with the second polymer to form the polymer mixture.

6. The method of claim 1, wherein the first polymer is any one of the following: polyamide, polyethylene terephthalate (PET), and polybutylene terephthalate (PBT).

7. The method of claim 1, wherein the second polymer is any one of the following: polyethylene, polypropylene, and a mixture thereof.

8. The method of claim 1, the extrusion being performed at a pressure of 40-140 bars.

9. The method of claim 1, wherein the polymer mixture comprises 0.2 to 40 percent by weight the first polymer.

10. The method of claim 1, wherein the polymer mixture comprises more than 70 percent by weight the second polymer.

11. The method of claim 1, wherein the first dye is an azo-nickel pigment complex in a concentration of 0.5-5 by weight of the first phase and/or wherein the second dye is phthalocyanin green in a concentration of 0.001-0.3 % by weight of the second phase.

12. The method of claim 1, wherein the artificial turf fiber extends a predetermined length beyond the artificial turf backing, and wherein the form of threadlike regions have a length less than one half of the predetermined length.

13. An artificial turf according to the method of claim 1, comprising an artificial turf textile backing and the artificial turf fiber incorporated into the artificial turf textile backing, wherein the artificial turf fiber comprises at least one monofilament including a surface, the at least one monofilament comprising the marbled pattern of the first and the second color on the surface, wherein the monofilament is a monofilament created in the extrusion step from the liquid polymer mixture, each of the at least one monofilament comprising: the first polymer in the form of the threadlike regions, the first polymer comprising the first dye having the first color; the second polymer, the second polymer comprising the second dye having the second color, wherein the form of threadlike regions are embedded in the second polymer, wherein the first polymer is immiscible in the second polymer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following embodiments of the invention are explained in greater detail, by way of example only, making reference to the drawings in which:

(2) FIG. 1 shows a flowchart which illustrates an example of a method of manufacturing artificial turf;

(3) FIG. 2 shows a flowchart which illustrates one method of creating the polymer mixture;

(4) FIG. 3a shows a section of the marbled surface of a monofilament;

(5) FIG. 3b shows a photograph of a moulded part generated in the extrusion process;

(6) FIG. 4 shows a diagram which illustrates a cross-section of a polymer mixture;

(7) FIG. 5 shows a further example of a polymer mixture;

(8) FIG. 6 illustrates the extrusion of the polymer mixture into a monofilament;

(9) FIG. 7 shows a cross-section of a small segment of the monofilament;

(10) FIG. 8 illustrates the effect of stretching the monofilament;

(11) FIG. 9 shows an electron microscope picture of a cross-section of a stretched monofilament; and

(12) FIG. 10 shows an example of a cross-section of an example of artificial turf.

DETAILED DESCRIPTION

(13) Like numbered elements in these figures are either equivalent elements or perform the same function. Elements which have been discussed previously will not necessarily be discussed in later figures if the function is equivalent.

(14) FIG. 1 shows a flowchart which illustrates an example of a method of manufacturing artificial turf. First in step 100 a liquid polymer mixture is created. The polymer mixture is at least a two-phase system. The first phase comprises a first polymer and a first dye. The second phase comprises a second polymer and a second dye. According to some embodiments, the polymer mixture may comprise a third phase, e.g. a compatibilizer or a further polymer being immiscible both with the first and second phase. Optionally, the third phase may comprise a third dye having a different color than the first and second dyes. The first polymer and the second polymer are immiscible and the first and second dye basically are confined to their respective phase, i.e., there is—in the time until the liquid polymer mix is extruded and has solidified as monofilament—approximately no diffusion of a dye into another one of the phases. In other examples there may be additional polymers such as a third, fourth, or even fifth polymer that are also immiscible with the second polymer. There also may be additional compatibilizers which are used either in combination with the first polymer or the additional third, fourth, or fifth polymer, and there may be a respective dye in each of the further polymers.

(15) The liquid polymer mix may be created by heating the first and second and any further polymer, if any, to a temperature that is above the melting point of said polymers. Thereby, the liquid polymer mixture may optionally be stirred at a stirring rate suitable to ensure that the molten first polymer is dispersed in the form of beads in the molten second polymer, whereby in some embodiments a third phase comprising the compatibilizer may build an envelope layer around the beads.

(16) In the next step 102 the polymer mixture is extruded into a monofilament. Next in step 104 the monofilament is quenched or rapidly cooled down. Next in step 106 the monofilament is reheated. In step 108 the reheated monofilament is stretched to deform the polymer beads into thread-like regions and to form the monofilament into the artificial turf fiber.

(17) Additional steps may also be performed on the monofilament to form the artificial turf fiber. For instance the monofilament may be spun or woven into a yarn with desired properties. Next in step 110 the artificial turf fiber is incorporated into an artificial turf backing. Step 110 could for example be, but is not limited to, tufting or weaving the artificial turf fiber into the artificial turf backing. Then in step 112 the artificial turf fibers are bound to the artificial turf backing. For instance the artificial turf fibers may be glued or held in place by a coating or other material. Step 112 is an optional step. For example if the artificial turf fibers are woven into the artificial turf backing step 112 may not need to be performed.

(18) FIG. 2 shows a flowchart which illustrates one method of creating the liquid polymer mixture. In this example the liquid polymer mixture to be created is a three-phase system. First in step 200 a first mixture is formed by mixing the first polymer with the first dye and the compatibilizer. Additional additives may also be added during this step, e.g. to increase flame or UV-resistance or improve the flowing properties of the polymer mixture. Next in step 202 the first mixture is heated. Next in step 204 the first mixture is extruded. Then in step 206 the extruded first mixture is then granulated or chopped into small pieces. Next in step 208 the granulated first mixture is mixed with the second polymer and the dye. Additional additives may also be added to the polymer mixture at this time. Finally in step 210 the granulated first mixture is mixed with the second polymer and the second dye and the resulting mixture is heated to form the liquid polymer mixture. The heating and mixing may occur at the same time. In the resulting liquid three phase mixture, the first phase may comprise the molten first polymer and the first dye, the second phase may comprise the molten second polymer and the second dye, and the third phase may comprise the compatibilizer. Some or all of the phases may comprise some or more of the further additives.

(19) According to other embodiments (not shown), the first mixture is formed as granulated first mixture described above. In addition, a second granulated mixture is created by mixing the second polymer with the second dye. Additional additives may be added during this step. Then, the second mixture is heated and extruded. The extruded second mixture is then granulated or chopped into small pieces to provide the granulated second mixture. The granulated first and second mixtures are mixed together and are heated, thereby forming the liquid polymer mixture.

(20) FIG. 3a shows a section of the surface of a monofilament according to embodiments of the invention. The “white” polymer domains or (“threads”) 302 correspond to a first phase, the dark polymer domains 304 correspond to a second phase.

(21) According to embodiments, the occurrence of polymer domains of the different phases and respective colors changes every 50-1000 μm. According to embodiments, the occurrence of polymer domains of the different phases and respective colors changes every 100-700 μm of the extruded and stretched monofilament. For example, the distance d between the center of a first and a second polymer domain may be about 300 μm.

(22) FIG. 3b shows a photograph of a moulded part generated in the extrusion process.

(23) A first part 314 of the moulded part depicts an area in which a separation of phases occurred next to the extrusion hole. In this area, the molten polymer mixture is under high pressure and shows a turbulent flow characteristic. In area 314 (under high pressure conditions and at turbulent flow conditions), domains of the same phase do not have enough time to unify and to generate a visible marbled pattern as at the time of solidification, the individual polymer domains in region 314 are too thin.

(24) A second part 318 of the moulded part depicts an area in which a separation of phases occurred sufficiently far away from the extrusion hole. In this area, that corresponds to the state of a monofilament at the end of the quenching process in a quenching liquid, the molten polymer mixture is under low pressure (e.g. pressure of environmental air) and shows a laminar flow characteristic. In area 318, domains of the same phase have enough time to unify to clearly visible thread-like regions 310 of a particular color (e.g. yellow or light-green) that can clearly be separated from the (e.g. green or dark-green) background polymer phase. Thus, area 318 that corresponds to the state of an extruded and quenched monofilament according to embodiments of the invention, comprises a visible marbled pattern as at the time of solidification, the individual polymer domains in region 318 change every 50-1000 μm, e.g. every 300 μm.

(25) In the depicted example, the polymer domain 310 may be yellow and correspond to a first polymer consisting of polyamide, the polymer region 312 may be green and correspond to a PE or PP phase.

(26) FIG. 4 shows a diagram which illustrates a cross-section of a liquid polymer mixture 400. The polymer mixture 400 comprises at least a first phase with a first polymer and a first dye and a second phase 404 with a second polymer and a second dye. In the depicted embodiment, the polymer mixture comprises a third phase 406 that mainly or solely comprises a compatibilizer. The third phase may comprise the first or the second or a third dye or no dye at all. The first phase and the second phase are immiscible. The first polymer and the first phase is less abundant than the second phase (that mainly consists of the second polymer). The first phase 402 is shown as being surrounded by the compatibilizer phase 406 and being dispersed within the second phase 404. The first phase 402 surrounded by the compatibilizer phase 406 forms a number of polymer beads 408. The polymer beads 408 may be spherical or oval in shape or they may also be irregularly-shaped depending up on how well the polymer mixture is mixed and the temperature. The polymer mixture 400 is an example of a three-phase system. The compatibilizer phase 406 separates the first phase 402 from the second phase 406.

(27) FIG. 5 shows a further example of a polymer mixture 500. The example shown in FIG. 5 is similar to that shown in FIG. 4 however, the polymer mixture 500 additionally comprises a fourth phase 502 with a third polymer. Some of the polymer beads 408 are now comprised of the third polymer. The polymer mixture 500 shown in FIG. 5 is a four-phase system. The four phases are made up of a first phase 402 comprising the first polymer and the first dye, a second phase 404 comprising the second polymer and the second dye, a third phase 406 comprising the compatibilizer and a fourth phase 502 comprising the further polymer 502. The first phase 402 and the fourth phase 502 are not miscible with each other and are not miscible with the second phase 404 or the third phase. The compatibilizer as a third phase separates the first phase from the second phase and separates the fourth phase 502 from the second phase 404.

(28) In this example the same compatibilizer is used for both the first phase (and respective first polymer) and the fourth phase (and respective polymer). In other examples a different compatibilizer could be used for the first phase 402 and the fourth phase 502.

(29) For example, the four phase polymer mixture may be created by forming a first granulated mixture and a second granulated mixture. The granulated first mixture is formed by mixing the first polymer, the first dye and the compatibilizer, heating the first mixture, extruding the first mixture and granulating the extruded first mixture. The granulated second mixture is formed by mixing the third polymer, a third dye and a compatibilizer (the same or a different one as used for creating the first mixture), heating the second mixture, extruding the second mixture and granulating the extruded second mixture. The creating of the polymer mixture further comprises mixing the first granulated mixture and the second granulated mixture with the second polymer and a second dye that will remain in the second phase resulting from the melting of the second polymer. The creating of the polymer mixture further comprises the step of heating the first granulated mixture and the second granulated mixture with the second polymer to form the liquid polymer mixture. This method may provide for a precise means of making the polymer mixture and controlling the size and distribution of the polymer beads using two different polymers and respective dyes that are embedded in a further (the second) polymer, typically PE comprising a still other (“second”) dye. The resulting marble texture may thus comprise three different colors, a first color resulting from the first dye in the first phase, a second color resulting from the second dye in the second (PE) phase that surrounds the beads comprising the first or third polymer, and a third color resulting from the third dye in the third phase 502. Thus, complex marbled color patterns can be generated that faithfully reflect the appearance of natural grass.

(30) As an alternative to this the polymer mixture could be made by adding the first polymer the first dye, the second polymer and the second dye, the third polymer and the one or more types of compatibilizer all together at the same time and then mixing them more vigorously. The first, second and fourth dye in this case have to be chosen such that they migrate to their respective phases after the mixture was melted. For example, the first dye may be polar and migrate into the first phase comprised mainly of a first, polar polymer. The second dye may be apolar and migrate into the second phase comprised mainly of a second, apolar polymer. The third dye could be covalently bound to the third polymer before the third polymer is added to the mixture.

(31) FIG. 6 illustrates the extrusion of the polymer mixture into a monofilament. Shown is an amount of polymer mixture 600. Within the polymer mixture 600 there is a large number of polymer beads 408. The polymer beads 408 may be made of one or more polymers that is not miscible with the second polymer and is also separated from the second polymer by a compatibilizer. A screw, piston or other device is used to force the polymer mixture 600 through a hole 604 in a plate 602. This causes the polymer mixture 600 to be extruded into a monofilament 606. The monofilament 606 is shown as containing polymer beads 408 also. The second polymer in the second phase 404 and the polymer beads 408 are extruded together. In some examples the second polymer will be less viscous than the polymer beads 408 comprising the first polymer and the polymer beads 408 will tend to concentrate in the center of the monofilament 606. This may lead to desirable properties for the final artificial turf fiber as this may lead to a concentration of the thread-like regions in the core region of the monofilament 606. However, the composition of the first and second phases and in particular the first and second polymers are chosen such (e.g. in respect to polymer chain length, number and type of side chains, etc.) that the first phase has a higher viscosity than the second phase and that the beads and the thread-like regions concentrate in the core region in the monofilament, whereby there are still sufficient amounts of the beads and the thread-like regions on the surface of the monofilament to result in a marbled color texture on the surface of the monofilament.

(32) FIG. 7 shows a cross-section of a small segment of the monofilament 606. The monofilament is again shown as comprising the second polymer 404 with the polymer beads 408 mixed in. The polymer beads 408 are separated from the second polymer by compatibilizer which is not shown. To form the thread-like structures a section of the monofilament 606 is heated and then stretched along the length of the monofilament 606. This is illustrated by the arrows 700 which show the direction of the stretching. The first and second polymers have different colors. In case the surface of a monofilament is abraded, the marbled color pattern is still visible as the two different dyes are not confined to the surface region. Nevertheless, the fine-granular embedding of the first phase into the second phase prevents a delamination of the two different polymers or polymer phases.

(33) FIG. 8 illustrates the effect of stretching the monofilament 606. In FIG. 8 an example of a cross-section of a stretched monofilament 606 is shown. The polymer beads 408 in FIG. 7 have been stretched into thread-like structures 800. The amount of deformation of the polymer beads 408 would be dependent upon how much the monofilament 606′ has been stretched.

(34) Examples may relate to the production of artificial turf which is also referred to as synthetic turf. In particular, the invention relates to the production of fibers that imitate grass both in respect to mechanical properties (flexibility, surface friction) as well as optical properties (color texture). The fibers are composed of first and second phases that are not miscible and differ in material characteristics as e.g. stiffness, density, polarity and in optical characteristics due to the two different dyes. In some embodiments, a fiber may in addition comprise a compatibilizer and further components.

(35) In a first step, the polymer mixture comprising two or more different phases respectively comprising a polymer and a dye and optionally some additional substances is generated whereby the quantity of the second polymer is about 80-90 mass percent of the polymer mixture. The quantities of the first phase which may mainly consist of the first polymer may be 5% to 10% by mass of the polymer mixture and the quantity of a third phase being largely or completely comprised of the compatibilizers being 5% to 10% by mass of the polymer mixture. Using extrusion technology results in a mixture of droplets or of beads of the first polymer surrounded by the compatibilizer that is dispersed in the polymer matrix of the second polymer and that have a different color than the second phase.

(36) The melt temperature used during extrusion is dependent upon the type of polymers and compatibilizer that is used. However the melt temperature is typically between 230° C. and 280° C.

(37) A monofilament, which can also be referred to as a filament or fibrillated tape, is produced by feeding the mixture into an fiber producing extrusion line. The melt mixture is passing the extrusion tool, i.e., a spinneret plate or a wide slot nozzle, forming the melt flow into a filament or tape form, is quenched or cooled in a water spin bath, dried and stretched by passing rotating heated godets with different rotational speed and/or a heating oven.

(38) The monofilament or type is then annealed online in a second step passing a further heating oven and/or set of heated godets.

(39) By this procedure the beads or droplets of the first phase (optionally surrounded by a compatibilizer phase) are stretched into longitudinal direction and form small fiber like, linear structures. The majority of the linear structures is completely embedded into the polymer matrix of the second polymer but a significant portion, e.g. 5 or more % of the linear structures, are at the surface of the monofilament.

(40) FIG. 9 shows a microscopic picture of a cross-section of a stretched monofilament manufactured using an example of a method described above. The horizontal white streaks within the stretched monofilament 606 are the thread-like structures 800. Several of these thread-like structures are labeled 800. The thread-like structures 800 can be shown as forming small linear structures of the first polymer within the second polymer.

(41) The resultant fiber may have multiple advantages, namely softness combined with durability and long term elasticity. In case of different stiffness and bending properties of the polymers the fiber can show a better resilience (this means that once a fiber is stepped down it will spring back) In case of a stiff first polymer, the small linear fiber structures built in the polymer matrix are providing a polymer reinforcement of the fiber.

(42) Delimitation due to the composite formed by the first and second polymers is prevented due to the fact that the short fibers of the second polymer are embedded in the matrix given by the first polymer.

(43) FIG. 10 shows an example of a cross-section of an example of artificial turf 1000. The artificial turf 1000 comprises an artificial turf backing 1002. Artificial turf fiber 1004 has been tufted into the artificial turf backing 1002. On the bottom of the artificial turf backing 1002 is shown a coating 1006. The coating may serve to bind or secure the artificial turf fiber 1004 to the artificial turf backing 1002. The coating 1006 may be optional. For example the artificial turf fibers 1004 may be alternatively woven into the artificial turf backing 1002. Various types of glues, coatings or adhesives could be used for the coating 1006. The artificial turf fibers 1004 are shown as extending a distance 1008 above the artificial turf backing 1002. The distance 1008 is essentially the height of the pile of the artificial turf fibers 1004. The length of the thread-like regions within the artificial turf fibers 1004 is half of the distance 1008 or less.

List of Reference Numerals

(44) 100-110 steps

(45) 200-210 steps

(46) 302 first color of first dye

(47) 304 second color of second dye

(48) 310 unified first phase domains of yellow color

(49) 312 unified second phase domains of green color

(50) 314 turbulent flow moulded part region

(51) 318 laminar flow moulded part region

(52) d average distance between regions of different color

(53) 400 polymer mixture

(54) 402 first phase

(55) 404 second phase

(56) 406 third phase with compatibilizer

(57) 408 polymer bead

(58) 500 polymer mixture

(59) 502 third polymer

(60) 600 polymer mixture

(61) 602 plate

(62) 604 hole

(63) 606 monofilament

(64) 606′ stretched monofilament

(65) 700 direction of stretching

(66) 800 threadlike structures

(67) 1000 artificial turf

(68) 1002 artificial turf carpet

(69) 1004 artificial turf fiber (pile)

(70) 1006 coating

(71) 1008 height of pile