US20080206381A1

US20080206381A1 - Methods and systems for manufacturing yarns for synthetic turf

Info

Publication number: US20080206381A1
Application number: US12/035,784
Authority: US
Inventors: Joseph C. Price
Original assignee: Nexcel Synthetics LLC
Current assignee: Nexcel Synthetics LLC
Priority date: 2007-02-23
Filing date: 2008-02-22
Publication date: 2008-08-28

Abstract

Systems and methods for manufacturing synthetic yarns for synthetic turf. The systems and methods include rollers for advancing a plastic sheet forward through a manufacturing process. The plastic sheet is cooled and heated on opposing sides by alternating temperature rollers to pre-form the plastic sheet such that subsequent synthetic yarns made from the sheet will have a curled shape. The plastic sheet is then cut longitudinally by a plurality of slitting blades along the length of the sheet to form a plurality of single strand synthetic yarns. A drawing device then draws and stretches the single strand synthetic yarns to a desired width and thickness, wherein the drawing device includes a drawing oven for heating the yarns, and a plurality of drawing rollers for pulling and stretching the heated yarns. The final product drawn yarns comprise sealed, smooth yarns with desirable rounded edges and a curled tip.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent No. 60/891,387, filed Feb. 23, 2007, and entitled “Method and Apparatus for Manufacturing Yarns for Synthetic Turf,” which is incorporated herein by reference in its entirety.

FIELD OF THE PRESENT INVENTION

The present invention relates generally to manufacturing yarns for synthetic turf. More particularly, the present invention relates to methods, devices, and systems for manufacturing yarns for synthetic turf that are resilient, retain infill, and have improved appearance and texture.

BACKGROUND OF THE PRESENT INVENTION

Synthetic turf is a surfacing material used to imitate grass. It is generally used in areas where grass cannot grow, or in areas where grass maintenance is impossible or undesired. Synthetic turf may be used in several applications, including indoor and outdoor synthetic putting greens, golf short game facilities, indoor practice facilities, golf driving range tee mats and target greens, sports fields (such as football, soccer, rugby, bocce, tennis, baseball, lacrosse, etc.), lawns, parks, playgrounds, athletic fields, school play yards, cruise ships, hotels, other hospitality settings, and many other applications.
Synthetic turf is produced with a tufting process. A large number of needles insert synthetic yarn into a fabric or rubber backing structure. Then, a flexible adhesive such as polyurethane is used to bind the fibers to the backing structure. This process is similar to the procedure used to create the majority of residential and commercial carpets.
The fibers or yarns that make up the blades of “grass” for synthetic turf are typically made of a plastic material, such as nylon, polypropylene, linear low density polyethylene (hereinafter “LLDPE”), or any combination of these materials. Generally, these plastic materials are extruded into either thin sheets or individual strands, and are then drawn via a conventional drawing process to stretch and thin the sheets or strands.
One conventional method of manufacturing the fibers that make up the “grass” blades from an extruded sheet is called “fibrillation,” which essentially involves punching holes or slits in the plastic sheet after it has been drawn. Even though the plastic sheet is being cut and slit, however, the plastic sheet remains in one piece. Usually, the plastic sheet is then further cut into sections having a width of approximately 1 inch, and these sections (each of which still contains multiple “grass” strands connected together) are used in the tufting process to make the synthetic turf.
The cutting in the fibrillation process is accomplished by hammering the plastic sheet with a roller that includes a large number of pins on its outer surface, and the roller tears and cuts the sheet as the sheet moves forward along the processing line. Often, the cuts in the sheet create a honeycomb-like pattern, such that the end result is an intact sheet with multiple strands connected together that resemble the appearance of grass.
While the fibrillating process may be cheap and easy, there are several disadvantages associated with synthetic turf made from fibrillated “grass” blades. Because of the violent method in which the plastic sheets are cut, the resulting blades of “grass” have sharp or rough edges, which are undesirable because they present a more abrasive surface that can cause injury or irritation if someone slides or falls on the turf. Also, because of the forceful manner in which these plastic sheets are punctured and slit, the deterioration of the fibers begins as soon as the fibers are put into use. This deterioration is enhanced by brushing machines containing rigid bristles that are often used to sweep away fibers that have been torn from the turf. These brushing machines further break apart and tear the fibers, and typically accelerate the overall weakening of the turf. Additionally, because the strands of “grass” are lumped together into sections, and are not individual and discrete, the fibrillated synthetic turf lacks the look and feel of real grass.
To combat the abrasive, non-resilient nature of the fibrillated fibers, another type of fiber, typically called “monofilament” fiber, is created by extruding the plastic material through a die or spinneret to create several discrete strands of fiber. These monofilament fibers are advantageous over the fibrillated fibers because they are individual and discrete, so they more closely resemble real grass. Also, they have a smoother finish and feel as compared to fibrillated fibers.
However, because the monofilament fibers are straight and upright when installed as synthetic turf, the rubber and sand used as infill around the base of the fibers can blow away or be kicked around by players on the turf because there is nothing keeping the infill in place. This loss or displacement of infill is commonly referred to as “flyout.” Over time, flyout of infill results in a non-uniform, abrasive playing surface, which is highly undesirable. Additionally, because each strand of monofilament fiber must be individually extruded, it can be difficult to easily and efficiently manufacture large quantities of the fibers.
Therefore, there exists a long-felt but unresolved need for synthetic yarns, or “grass” blades, for synthetic turf that are resilient to abuse, have smooth or rounded edges, retain infill and prevent flyout, are easy to efficiently mass produce, and are individual and discrete to accomplish the look and feel of real grass.

BRIEF SUMMARY OF THE INVENTION

Briefly described, and according to one embodiment, the present invention relates to a system for manufacturing synthetic yarns used for synthetic turf. The system includes a plurality of rollers for advancing a plastic sheet along a predetermined path through the system. Initially, as the plastic sheet enters the system, a cooling roller cools one side of the sheet, and then a heating roller heats the opposing side of the sheet to pre-form the plastic sheet such that subsequent synthetic yarns made from the sheet will have a curled shape. After the plastic sheet is passed around the alternating cooling and heating rollers, a slitting component engages and slits the plastic sheet longitudinally along the length of the sheet to form a plurality of single strand synthetic yarns as the sheet advances along the predetermined path. A drawing component then pulls the single strand synthetic yarns under tension and heat to stretch and thin the yarns, and also to round or radius the edges of the yarns.
According to one aspect, the cooling roller maintains a temperature of about 25° C. and cools the plastic sheet as the plastic sheet enters the system. Additionally, the heating roller maintains an temperature of about 35° C. and heats the plastic sheet after the plastic sheet is passed around the cooling roller. According to one aspect, the temperatures of both the cooling roller and heating roller are controlled by the circulation of cold or hot water throughout the inside of the rollers.
According to another aspect, once the single strand synthetic yarns have been drawn by the drawing component, the yarns are cut to predetermined lengths and then reheated to effect a curled shape in the yarns. This curled shape was originally pre-formed in the plastic sheet when it was passed around the alternating cooling and heating rollers, and the subsequent reheating stage causes this latent curl to become effected. According to one aspect, the single strand synthetic yarns are applied to a backing after they have been cut to predetermined lengths but before they enter the reheating stage.
According to yet another aspect, the slitting component comprises a plurality of slitting blades that engage and continuously cut the plastic sheet into the plurality of single strand synthetic yarns as the sheet advances along the predetermined path. In one aspect, the plurality of slitting blades are spaced apart at a predetermined equal distance. This equal distance corresponds to the initial width of the single strand yarns, so it can be set by the user of the system to any initial width the user desires. Preferably, however, this predetermined distance is between about 1.00 mm to about 6.00 mm. Alternatively, the plurality of slitting blades may be spaced apart at a plurality of difference distances to create single strand synthetic yarns of a corresponding plurality of widths. According to one aspect, the plastic sheet advances through the slitting component at a speed of about 16.6 m/min.
According to still another aspect, a pulling and tensioning roller is positioned to contact the plurality of single strand synthetic yarns at a distance D less than or equal to 1.0 inch after the slitting blades to maintain tension on the yarns. When the initial yarn width is less than 5.00 mm, it is important to retain a distance D of less than or equal to 1.0 inch to keep the freshly-cut yarns moving freely through the apparatus, such that they do not become tangled or lose tension. Preferably, the distance D is about ¾ of at inch.
According to a further aspect, a second pulling and tensioning roller is positioned opposite the first pulling and tensioning roller such that the single strand synthetic yarns are pinched between the two rollers to maintain tension on the yarns. In one aspect, the second pulling and tensioning roller, rather than being directly opposite the first pulling and tensioning roller, is positioned at a distance from the first pulling and tensioning roller along the predetermined path.
According to another aspect, the drawing component includes a drawing oven for heating the single strand synthetic yarns and a plurality of drawing rollers adapted to pull and stretch the yarns. In one aspect, the drawing oven heats the single strand synthetic yarns to a temperature of about 90° C. to about 110° C. The yarns are heated in this way so that they may be stretched and shaped by the plurality of drawing rollers. The heated stretching of the yarns creates a smooth finish on yarns, and additionally rounds or radiuses the edges and corners of the yarns. This heated stretching provides a natural seal or finish on the single strand synthetic yarns giving the yarns a higher resilience and more natural look and feel as compared to other synthetic yarns used for synthetic turf.
According to one aspect, the plurality of drawing rollers create the tension that pulls and stretches the single strand yarns when they are in the drawing oven. After exiting the oven, the yarns are additionally pulled around the plurality of drawing rollers for further shaping and finishing. In one aspect, the drawing component pulls the plurality of single strand synthetic yarns under tension with a draw ratio of about 6:1.
According to an additional aspect of the present embodiment, at least one of the drawing rollers comprises a heated drawing roller, and at least one of the rollers comprises a cooled drawing roller. The heated drawing rollers maintain the temperature of the yarns as they are further processed by the rollers, and the cooled drawing rollers cool the yarns to room temperature as the yarns complete the drawing process. Preferably, the heated drawing rollers maintain a temperature of about 90° C. to about 110° C., and the cooled drawing rollers maintain a temperature of about 25° C. According to one aspect, the heated and cooled drawing rollers are heated and cooled in the same manner as the heating and cooling rollers used in an earlier stage of the system.
According to one aspect, the plastic sheet is made of linear low density polyethylene (LLDPE), polypropylene, nylon, or any combination of these materials. In another aspect, the plastic sheet initially has a width between about 0.5 m to about 3.0 m and a thickness between about 50 microns to about 500 microns (1.0×10⁻⁶meters) before the sheet is slit by the slitting component.
According to still another aspect, after the yarns are drawn and stretched by the drawing component, the final width of the single strand synthetic yarns will be less than the initial width of the yarns immediately after the yarns are slit by the slitting blades. In one aspect, the final width of the yarns is between about 0.5 mm to about 3.0 mm and the thickness of the yarns is between about 25 microns to about 150 microns.
According to one aspect, at least one of the rollers, pulling and tensioning rollers, and the drawing rollers of the system are driven by a rotational mechanical force to advance the plastic sheet and the resulting single strand synthetic yarns forward through the system along the predetermined path. Additionally, at least one of the rollers or pulling and tensioning rollers may be locked in a fixed position so that it does not rotate with the movement of the plastic sheet and single strand synthetic yarns to create added tension on the sheet and yarns. Alternatively, at least one of the rollers or pulling and tensioning rollers may be mounted on bearings such that it may rotate freely with the movement of the sheet or yarns to allow for smoother movement of the sheet and yarns through the system. Further, at least one of the rollers or pulling and tensioning rollers includes a rough or coarse surface for creating additional traction to move the sheet or yarns along the path. Preferably, the roller or pulling and tensioning roller(s) that include the rough surface should be the same roller(s) that are driven by the rotational mechanical force.
According to a yet further aspect, the system includes a winder to wind the plurality of single strand synthetic yarns together to form multiple strand synthetic yarn combinations after the yarns have been drawn by the drawing component, and a twister to wrap the multiple strand synthetic yarns combinations around a flanged spool for further processing.
According to another embodiment, the present invention relates to a method for manufacturing synthetic yarns used for synthetic turf. The method includes advancing a plastic sheet along a predetermined path. The method also includes the steps of cooling one side of the plastic sheet and then immediately heating the other side of the plastic sheet before the sheet is cut into single strand synthetic yarns. This alternating cooling and heating of opposing sides of the plastic sheet will eventually result in curled synthetic yarns after the sheet is cut into yarns and further processed. The method further comprises the step of continuously slitting the plastic sheet longitudinally into a plurality of single strand synthetic yarns, such that the sheet is slit as a set point along the predetermined path as the sheet advances along the path. The yarns are then drawn under tension and heat to stretch and thin the yarns and to round and curve the edges of the yarns.
According to one aspect, one side of the plastic sheet is cooled to a temperature of about 25° C., and the other side of the plastic sheet is heated to a temperature of about 35° C. before the sheet is slit into single strand synthetic yarns.
According to another aspect, after the yarns have been drawn under tension and heat, the yarns are cut to predetermined lengths and attached to a backing for further use as synthetic turf. In one aspect, the yarns are reheated after they are cut but before they are attached to the backing to cause the ends of the yarns to curl. In another aspect, the yarns are reheated after they have been cut and attached to the backing, again to cause the ends of the yarns to curl.
In an additional aspect, the plastic sheet advances along the predetermined path at a speed of about 16.6 m/min. In one aspect, before the plastic sheet is slit, the sheet has a width between about 0.5 m to about 3.0 m and a thickness between about 50 microns to about 500 microns.
According to yet another aspect, the single strand synthetic yarns have widths between about 1.0 mm to about 6.0 mm before the single strand synthetic yarns are drawn. In one aspect, the single strand synthetic yarns have widths between about 0.5 mm to about 3.0 mm and thicknesses between about 25 microns to about 150 microns after the single strand synthetic yarns are drawn.
According to still another aspect, the method further comprises the step of contacting and pulling the single strand synthetic yarns along the predetermined path immediately after the yarns have been slit to maintain tension in the yarns. Generally, this contacting and pulling occurs at a point less than or equal to 1.0 inch after the point in which the single strand synthetic yarns were slit.
According to a further aspect, the plurality of single strand synthetic yarns are drawn at a draw ratio of about 6:1. In one aspect, the yarns are heated to a temperature of about 90° C. to about 110° C. while being drawn. The yarns are heated in this way so that they may be stretched and shaped during the drawing process. The heated stretching of the yarns creates a smooth finish on the yarns, and additionally rounds or radiuses the edges and corners of the yarns. This heated stretching provides a natural seal or finish on the single strand synthetic yarns giving the yarns a higher resilience and more natural look and feel as compared to other synthetic yarns used for synthetic turf. Additionally, in some aspects, the single strand synthetic yarns are cooled after being drawn. In one aspect, the yarns are cooled to a temperature of about 25° C.
In yet a further aspect, the single strand synthetic yarns are wound and twisted together after being drawn for further processing.
According to one aspect, the plastic sheet is made of linear low density polyethylene (LLDPE), polypropylene, nylon, or any combination of these materials.
According to an additional aspect, the present invention also relates to the single strand synthetic yarns manufactured by a method of the present invention. These single strand synthetic yarns are subsequently used to make synthetic turf.
These and other embodiments and aspects of the present invention will become apparent from the following description of the preferred embodiment taken in conjunction with the following drawings, although variations and modifications therein may be affected without departing from the spirit and scope of the novel concepts of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate one or more embodiments of the invention and, together with the written description, serve to explain the principles of the invention. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment, and wherein:

FIG. 1A is a flow chart demonstrating the high-level components of the system according to embodiments of the present invention.

FIG. 1B is a side view illustrating a slitting station used to slit a plastic sheet into a plurality of single strand synthetic yarns for synthetic turf according to embodiments of the present invention.

FIG. 2A is a magnified front view illustrating a slitter blade bar having a plurality of slitting blades used to slit a plastic sheet into a plurality of single strand synthetic yarns for synthetic turf according to embodiments of the present invention.

FIG. 2B is a top view of the plastic sheet and resulting single strand synthetic yarns as the plastic sheet is slit according to an embodiment of the present invention.

FIGS. 3A-3C illustrate various embodiments of the slitter blade bar, slitting blades and the surrounding rollers.

FIG. 4 is a side view illustrating a series of drawing rollers used to stretch and pull the single strand synthetic yarns to a desired shape according to embodiments of the present invention.

FIG. 5A shows a cross-sectional view of a single strand synthetic yarn after it has been slit but before it has been drawn.

FIG. 5B shows a cross-sectional view of a single strand synthetic yarn for synthetic turf after it has been drawn according to embodiments of the present invention.

FIG. 6A shows a single strand synthetic yarn with a resulting curled tip according to embodiments of the present invention.

FIG. 6B shows a strand of conventional synthetic yarn.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Various embodiments of the invention are now described in detail. Referring to the drawings, like numbers indicate like components throughout the views. As used in the description herein and throughout the claims that follow, the meaning of “a”, “an”, and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
The terms used in this specification generally have their ordinary meanings in the art, within the context of the invention, and in the specific context where each term is used.
Certain terns that are used to describe the invention are discussed below, or elsewhere in the specification, to provide additional guidance to the practitioner in describing the apparatuses, systems, and methods of the invention and how to make and use them. For convenience, certain terms may be highlighted, for example using italics and/or quotation marks. The use of highlighting has no influence on the scope and meaning of a term; the scope and meaning of a term is the same, in the same context, whether or not it is highlighted. It will be appreciated that the same thing can be said in more than one way. Consequently, alternative language and synonyms may be used for any one or more of the terms discussed herein, nor is any special significance to be placed upon whether or not a term is elaborated or discussed herein. Synonyms for certain terms are provided. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification, including examples of any terms discussed herein, is illustrative only, and in no way limits the scope and meaning of the invention or of any exemplified term. Likewise, the invention is not limited to various embodiments given in this specification. Furthermore, subtitles may be used to help a reader of the specification to read through the specification, which the usage of subtitles, however, has no influence on then scope of the invention.
Techniques and processes for manufacturing synthetic turf are well known to those skilled in the art. Therefore, the scope of the disclosure of the present invention is limited to the manufacture of synthetic yarns used for synthetic turf. Generally, the material used for synthetic yarn is linear low density polyethylene (hereinafter “LLDPE”). LLDPE is a substantially linear polymer, with a significant number of short branches, commonly made by copolymerization of ethylene with longer-chain olefins. LLDPE has higher tensile strength and higher impact and puncture resistance as compared to other similar materials. It is very flexible and elongates under stress. It can be used to make thin films, with enhanced environmental stress cracking resistance than other similar materials. Additionally, LLDPE has good resistance to chemicals and ultraviolet radiation. Accordingly, LLDPE is a particularly well-suited starting material to create synthetic yarn for synthetic turf.
Referring now to FIG. 1A, the high-level components and steps 10 involved in manufacturing synthetic yarns used for synthetic turf are shown according to embodiments of the present invention. The manufacturing process of synthetic yarn begins with the LLDPE raw material, which is typically in pellet form. The pellets are heated and extruded in a conventional manner at extruder 50 to produce LLDPE film of a desired thickness and width. The width of the initial LLDPE sheet is typically in a range of about 0.5 meters to about 3.00 meters, and the thickness of the LLDPE sheet is typically in a range of about 50 to about 500 microns. Preferably, the LLDPE sheet has a starting width of about 1.4 meters and a thickness of about 300 microns for easy handling and higher efficiency. However, as will be apparent to one having ordinary skill in the art, other widths and thicknesses are possible.
After the LLDPE sheet exits the extruder 50, it enters a slitting station 100, in which the LLDPE sheet is rolled across opposing temperature rollers that heat and cool opposing sides of the LLDPE sheet to produce a curl in the finished product synthetic yarn. After the LLDPE sheet is passed around the alternating temperature rollers, the sheet is then slit into single strand synthetic yarns. As will be described in greater detail below, the synthetic yarns are advantageously slit before they are drawn. Once cut by the slitting station 100, the plurality of yarn strands enter a drawing oven 60 wherein the yarns are heated and drawn (i.e. “stretched”) to a desired width and thickness by being pulled by a plurality of drawing rollers 400 on the exit side of the drawing oven 60. Once complete, the finished yarn product is sent to a winder 70 and a twister 80 to wind the yarns together for further processing and installation onto the backing used for synthetic turf.
FIG. 1B illustrates a side view of the slitting station 100 and how an LLDPE sheet is slit into a plurality of single strand synthetic yarns for use in manufacturing synthetic turf according to embodiments of the present invention. The slitting station 100 includes an air knife 120, a cooling roller 101, a heating roller 102, a plurality of pulling and tensioning rollers 103, 104, 106, 108, 113, 114, 116, and 118, and a slitter blade bar 110 having a plurality of slitting blades 112. The LLDPE sheet 200 and resultant slitted single strand synthetic yarns 202 are threaded along a predetermined path indicated by arrows 300.
Initially, an LLDPE sheet 200 is extruded from the extruder 50, and is blown onto the cooling roller 101 by the air knife 120. The air knife 120 forces the LLDPE sheet 200 against the cooling roller 101 and additionally stabilizes the sheet. Once on the cooling roller 101, the LLDPE sheet 200 is pulled, in tension, by the pulling and tensioning rollers 103, 104, 106, 108, 113, 114, 116, and 118 around the cooling roller 101 to cool one side of the LLDPE sheet 200 to room temperature, preferably about 25° C. According to one embodiment, the cooling roller 101 is cooled internally by cooled water that is circulated throughout the inside of the roller in a conventional manner. In this way, the cooling roller 101 cools the LLDPE sheet 200 via conduction.
Once the LLDPE sheet 200 has passed around the cooling roller 101, the sheet is then pulled around a heating roller 102. As shown in FIG. 1B, the heating roller 102 heats the opposing side of the LLDPE sheet 200 that was cooled by the cooling roller 101. The LLDPE sheet 200 is passed around these alternating temperature rollers 101 and 102 to produce a final product synthetic yarn that has a curled tip, as shown and as will be described in FIG. 6A. The alternating cooling roller 101 and heating roller 102 serve to introduce a latent curl to the LLDPE sheet by cooling one side of the sheet while immediately thereafter heating the other side of the sheet, as shown in FIG. 1B. This resulting curl is not realized, however, until the LLDPE sheet has been fully processed into synthetic yarns, cut into smaller length segments, and then subsequently reheated after being placed onto the backing used for synthetic turf, as will be described in greater detail below. Additionally, according to one embodiment, the heating roller 102 is heated in the same way that the cooling roller 101 is cooled—by heated water that is circulated throughout the roller.
As mentioned previously, “flyout” is a major problem with conventional synthetic turf. The movement or loss of the sand and rubber infill around the base of the fibers and yarns when used for synthetic turf creates an uneven, unsightly, and even dangerous playing surface. The curled tips on the synthetic yarns manufactured according to embodiments of the present invention are desirable because they help to keep the infill in place around the base of the “grass” blades once the synthetic turf is in use. These curled tips keep the infill from being blown away or significantly moved because they bend downward, thus providing a cover for the infill. With straight, conventional fibers, however, there is no covering keeping the infill in place, and thus “flyout” frequently occurs. Additionally, the curled tips of the yarns produced according to embodiments of the present invention give the synthetic yarns a more natural look and feel as compared to non-curled, conventional yarns.
Still referring to FIG. 1B, after the LLDPE sheet 200 is passed around the heating roller 102, the sheet is fed along the LLDPE sheet path as indicated by arrows 300. At least one of the pulling and tensioning rollers 103, 104, 106, 108, 113, 114, 116, and 118 is powered by a rotating mechanical force to move the LLDPE sheet 200 forward along the path. One or more of these pulling and tensioning rollers are used to create tension such that the LLDPE sheet 200 is moved forward in a consistent and flat motion. While a wide range of speeds are possible to move the LLDPE sheet through the slitting station 100, a speed of about 16.6 m/min is preferable. In some embodiments, one or more of the plurality of pulling and tensioning rollers 103, 104, 106, 108, 113, 114, 116, and 118 are stationary and will not roll with the movement of the LLDPE sheet 200 in order to create added tension upon the sheet. In other embodiments, one or more of the plurality of pulling and tensioning rollers are mounted on two bearings, one on each end, such that these rollers rotate along with the movement of the LLDPE sheet 200.
As the LLDPE sheet 200 is pulled along the path indicated by arrows 300, it is cut longitudinally along its length by the slitter blade bar 110 and corresponding slitting blades 112. According to one embodiment of the present invention, the slitter blade bar 110 has two primary positions. In its initial or disengaged position, the slitter blade bar 110 is raised such that the slitting blades 112 are not in contact with the LLDPE sheet 200 (not shown). This initial position allows the LLDPE sheet 200 to be fed through all of the pulling and tensioning rollers 103, 104, 106, 108, 113, 114, 116, and 118 to create the required tension on the LLDPE sheet before the cutting begins. The second or engaged position is the primary position of the slitting station 100, wherein the slitter blade bar 110 is lowered once the system begins running such that the blades 112 become engaged with and continuously slit the LLDPE sheet 200 into a plurality of single strand synthetic yarns 202 as the sheet 200 is advanced. FIG. 1B shows the slitter blade bar 110 and slitting blades 112 in this second, engaged position. Preferably, pulling and tensioning roller 108 rotates with the movement of the LLDPE sheet 200 to allow for smooth transition of the LLDPE sheet into the slitting blades 112.
Referring still to FIG. 1B, once the LLDPE sheet 200 has been cut into single strand synthetic yarns 202 by the slitting blades, the yarns 202 are pulled by the pulling and tensioning rollers 113, 114, 116, and 118 for further processing. If a preferred embodiment, pulling and tensioning roller 113 is driven by a rotational mechanical force to keep the strands taught and moving smoothly after they are cut. Additionally, in one embodiment of the present invention, pulling and tensioning roller 113 has a rough or coarse outer surface to create enough traction to keep the single strand synthetic yarns 202 moving forward smoothly.
FIG. 2A is a magnified front view showing the slitter blade bar 110 with a plurality of slitting blades 112 for slitting the LLDPE sheet into a plurality of single strand synthetic yarns for synthetic turf according to one embodiment of the present invention. The slitting blades 112 comprise razor blades or any other blades particularly adapted for making fine, precise cuts. The slitting blades 112 are typically spaced apart at a predetermined equal distance L that cuts the LLDPE sheet 200 into single strand synthetic yarns 202 with the same corresponding strand width L, as shown in FIG. 5A. This predetermined distance L is in the range of about 1.00 mm to about 6.00 mm, and preferably is either 3.00 mm or 4.00 mm. Once, the yarns are cut, they will be stretched and thinned by the drawing process, so the initial width of cut L must be larger than the final desired width of the yarns L′. While the resulting strand width L′ for a particular cut width L may vary depending on the subsequent draw ratio created by the drawing rollers, a cut width of 3.00 mm will typically produce a final product single strand synthetic yarn 202 with a width of 1:3 mm, and a cut width of 4.00 mm will typically produce a final product single strand synthetic yarn with a width of 1.6 mm. In an alternative embodiment (not shown), the slitting blades 112 can be set apart at a variety of different distances L to enable a sheet of LLDPE to produce two or more sized strands of yarn from the single sheet of LLDPE.
FIG. 2B shows a top view of the LLDPE sheet 200 as it passes under the slitter blade bar 110 and through the slitting blades 112, and is cut into single strand synthetic yarns 202 of equal size L. As shown in FIG. 2B, the single strand synthetic yarns 202 are continually cut by the slitting blades 112 to produce discrete, continuous strands.
Referring now to FIGS. 3A, 3B, and 3C, various positions of the pulling and tensioning rollers 108, 113, and 115 around the slitter blade bar 110 and slitting blades 112 are shown according to different embodiments of the present invention. In FIG. 3A, pulling and tensioning roller 113 is positioned such that the point of contact between the roller and the single strand synthetic yarns 202 measures a distance D from the point of contact where the slitter blades 112 engage the LLDPE sheet 200. This pulling and tensioning roller 113 is positioned under the single strand synthetic yarns 202 after they are cut from the LLDPE sheet 200 by the slitting blades 112. Additionally, pulling and tensioning roller 113 is positioned such that its central axis is parallel with the central axis of the slitter blade bar 110.
When the distance L between the slitter blades 112 is less than 5.00 mm, it can be difficult to keep the slitted single strand synthetic yarns 202 moving straight and smoothly with the pulling and tensioning roller 113. Accordingly, the predetermined distance D is typically less than or equal to 1 inch, and preferably about ¾ of an inch.
In one embodiment, as shown in FIG. 3B, an additional pulling and tensioning roller 115 is added to provide more stability and direction to the single strand synthetic yarns 202 as they pass through the slitting blades 112. The additional pulling, and tensioning roller 115 is added on the opposite side of the single strand synthetic yarns 202 from roller 113, such that the material is pulled and pinched between these two rollers 113 and 115. Preferably, pulling and tensioning roller 115 is driven by a rotational mechanical force, similar to roller 113. Also, the distance D remains less than or equal to 1 inch, and preferably about ¾ of an inch.
In another embodiment, as shown in FIG. 3C, the additional pulling and tensioning roller 115 is again added on the opposite side of the single strand synthetic yarns 202 from pulling and tensioning roller 113, but in this embodiment roller 115 is placed at some distance after roller 113 along the processing path of the single strand synthetic yarns. This roller configuration produces slightly different amounts of tension on the LLDPE sheet 200 and resulting single strand synthetic yarns 202 as compared to the configurations shown in FIGS. 3A and 3B. Thus, the pulling and tensioning rollers 108, 113, and 115 can be moved and positioned by the user to produce a certain desired level of tension on the LLDPE material as it progresses through the system, and, in particular, through the slitting blades 112.
As will be understood by one having ordinary skill in the art, other variations of rollers, including the addition of further pulling and tensioning rollers, are also possible to effectively create tension and corresponding smooth movement of the single strand synthetic yarns 202 and LLDPE sheet 200. Regardless, it is, important to note that the distance between where the slitting blades 112 engage the LLDPE sheet 200 and the point of contact between the resulting yarns 202 and the pulling roller 113 is kept at a distance D that is typically less than 1 inch, and preferably about ¾ of an inch.
Referring, again to FIGS. 1A and 1B, after the single strand synthetic yarns 202 are slit by the slitting blades 112, the yarns are fed into the drawing oven 60 by pulling and tensioning rollers 116 and 118. Preferably, at least one of rollers 116 and 118 is driven by a rotational mechanical force. In one embodiment of the present invention, the rollers 116 and 118 slow down the single strand synthetic yarns 202 as the yarns enter the drawing oven 60 to create added tension in the yarns as they are heated by the oven and subsequently stretched by the series of drawing rollers 400. According to one embodiment of the present invention, the temperature inside the drawing oven 60 is preferably between about 90° C. and about 110° C., but as will be apparent to those having ordinary skill in the art, other oven temperatures are possible.
As shown in FIG. 4, a series of drawing rollers 400 for stretching the slit single strand synthetic yarns 202 to a desired shape are illustrated according to embodiments of the present invention. The series of drawing rollers 400 include a plurality of pulling and tensioning rollers and a plurality of drawing rollers. In the embodiment shown in FIG. 4, the pulling and tensioning rollers include rollers 402, 404, 406, and 408, and the drawing rollers include rollers 410, 412, 414, 416, 418, 420, 422, 424, 426, and 428. The single strand synthetic yarns 202 are threaded around the rollers along a path indicated by arrows 300. As will be understood by one of ordinary skill in the art, other positions and numbers of rollers are possible other than the configuration shown in FIG. 4.
As the single strand synthetic yarns 202 progress through the drawing oven 60, the yarns are pulled and stretched out of the oven by pulling and tensioning rollers 402 and 404, and additionally by the drawing rollers 410, 412, 414, 416, 418, 420, 422, 424, 426, and 428. It is this pulling and stretching of the yarns 202 while they are in the oven 60 that gives the yarns of the present invention their added resilience and finishing, as will be described in greater detail below. Essentially, the single strand synthetic yarns 202 are restrained somewhat by the slower-spinning rollers 116 and 118 at the front end of the oven 60 while the yarns 202 are pulled on the other side of the oven 60 by the series of drawing rollers 400. This differential in speed and tension is what causes the yarns to stretch while traveling through the drawing oven 60. Accordingly, at least one of the pulling and tensioning rollers 402 and 404 and the drawing rollers 410, 412, 414, 416, 418, 420, 422, 424, 426, and 428 is driven by a rotational mechanical force.
The number of rollers used in the series of drawing rollers 400, as well as the speed at which the rollers are rotating, dictates the drawing ratio exerted upon the single strand synthetic yarns 202. While a wide range of drawing ratios may be used within embodiments of the present invention, a ratio of about 6:1 is preferable. If the drawing ratio is too low, the single strand synthetic yarns 202 may become too soft and stick to the rollers. If the drawing ratio is too high, the resulting yarns will likely be stiff and undesirable. Accordingly, although several different drawing ratios are possible under embodiments of the present invention, a ratio of about 6:1 produces high quality fibers with the system described herein.
According to further embodiments of the present invention, the plurality of drawing rollers 410, 412, 414, 416, 418, 420, 422, 424, 426, and 428 includes a plurality of cooled drawing rollers and a plurality of heated drawing rollers. In the embodiment shown in FIG. 4, the heated drawing rollers include rollers 410, 412, 414, 416, 418, 420, and 422, and the cooled drawing rollers include rollers 424, 426, and 428. These drawing rollers are heated and cooled conventionally by hot or cold water that is circulated throughout the inside of the rollers, just like the cooling roller 101 and heating roller 102. The heated drawing rollers 410, 412, 414, 416, 418, 420, and 422 remain at a temperature of about 90° C. to about 110° C. to maintain the heat and elasticity of the single strand synthetic yarns 202 as they are pulled and stretched around the heated drawing rollers after exiting the drawing oven 60. The cooled drawing rollers 424, 426, and 428 are kept at a temperature of about 25° C. to cool the yarns 202 to room temperature as they complete the drawing process. As will be understood by one having ordinary skill in the art, however, the number, variation, and temperature of the heated and cooled drawing rollers may vary at the operator's discretion to produce yarns or fibers of different properties and qualities.
After the single strand synthetic yarns 202 have been sufficiently drawn, the yarns are moved along the path 300 by pulling and tensioning rollers 406 and 408 for further processing. Thus, at least one of pulling and tensioning rollers 406 and 408 should be driven by a rotational mechanical force.
FIG. 5A shows a cross-sectional view of a single strand synthetic yarn 202 after it has been cut by the slitting blades 112, but before it has been drawn. FIG. 5B demonstrates a cross-sectional view of the same yarn after it has passed through the drawing oven 60 and drawing roller device 400. As shown in FIG. 5A, the pre-drawn yarn has a width L and a thickness T. As shown in FIG. 5B, the post-drawn yarn has a decreased width L′ and decreased thickness T′ due to the stretching and pulling caused by the drawing process. Additionally, the corners and edges of the post-drawn yarn have been naturally rounded from the drawing process, as will be described in greater detail below. The cross-section of the yarn shown in FIG. 5B represents a preferred cross-section of a yarn produced according to embodiments of the present invention.
In one embodiment, before the single strand synthetic yarn 202 is drawnn, the yarn has a width L in the range of about 1.00 mm to about 6.00 mm, and a thickness T in the range of about 50 microns to about 500 microns. After the yarn 202 ,is drawn,'the′ resulting width L′ and thickness T′ may vary depending on the draw ratio and heating oven 60 temperature, but the preferable width L′ is in the range of about 1.3 mm to about 1.6 mm, and the preferable thickness T′ is in the range of about 100 microns to about 135 microns. As mentioned previously, a starting width L of 3.00 mm will generally produce yarns, with a final width L′ of 1.3 mm, and a starting width L of 4.00 mm will generally produce yarns with a final width L′ of 1.6 mm according to embodiments of the present invention.
One benefit of drawing the yarns 202 after they have been slit according to embodiments of the present invention is that the heated stretching of the yarns naturally rounds off or radiuses the corners and edges of the yarns, as shown in FIG. 5B. As the yarns 202 are pulled through the drawing oven 60, the edges of the yarns are pulled and heated, causing them to melt and become round. These rounded edges produce a more natural look and feel to the yarns, and they eliminate the rough or sharp edges present on the yarns immediately after cutting, as shown in FIG. 5A. As mentioned previously, yarns with rough edges can cause injury or irritation to people who fall or slide on synthetic turf that incorporates rough-edged yarns. The yarns produced from embodiments of the present invention have smooth, rounded edges, which are highly desirable.
Additionally, drawing the single strand synthetic yarns 202 through the drawing oven 60 produces a natural seal or finishing on the yarns, thereby increasing the overall resilience of the yarns. This seal is again caused by the heated stretching of the yarns 202 as they are drawn. As mentioned previously, cut yarns that are not finished or sealed begin to deteriorate quickly once in use on synthetic turf because they lack the resiliency and strength of sealed or finished yarns. The drawing process employed by embodiments of the present invention creates a natural seal on the finished yarns that is simply not present in many other yarns.
According to embodiments of the present invention, after the single strand synthetic yarns 202 exit the series of drawing rollers 400, the yarns are passed on to conventional winder and twister stations 70, 80 respectively for further processing. Thereafter, when the yarns 202 are ready for use in production, the yarns are cut into smaller sections and attached to a synthetic rubber backing (either woven or nonwoven) by a tufting process (not shown). The yarn and synthetic backing combination are moved onto a tentering system (a chain link system with needles around its edges) that grabs the combination and moves it under a coating bar, wherein the backing is coated with polyurethane or another similar adhesive. At this stage, the yarn is held upside down by the tentering system, such that the single strand synthetic yarns 202 are hanging downward, with the coated backing facing upward. The backing and yarns are then heated to cure the adhesive to permanently attach the yarns to the backing, and to effect the curled tip in the yarns. In one embodiment, this heating comprises sending the yarn and backing combination through three curing ovens, with each oven heating the combination to a temperature of about 160° C. to about 220° C. The combination spends approximately 1-3 minutes in each respective curing oven. The heat produced by the curing ovens is a steam coil heat focused predominantly on the backing. The single strand synthetic yarns 202 receive indirect heat while the yarns are facing downward.
When the yarns 202 that are manufactured according to embodiments of the present invention are heated during this final curing process, they develop a curled tip, as shown in FIG. 6A. The curl in the yarns is a result of the LLDPE sheet 200 being initially passed around the alternating cooling roller 101 and heating roller 102 to cool and heat opposing sides of the sheet 20 before the sheet 200 is slit into yarns 202. This curl remains latent in the yarns 202 until they are drawn, cut into smaller sections, and finally heated in the curing ovens with the backing. Accordingly, the alternating temperature, rollers 101, 102 serve to pre-form the plastic sheet with a curl, but that curl is not effected until final cutting and heating. Alternatively, FIG. 6B demonstrates a conventional yarn 604 that has not undergone any sort of curling treatment. The preferable curled yarn 602 not only helps to retain infill on synthetic turf, as described previously, but also looks and feels more like real grass.
According to one embodiment, the single strand synthetic yarns 202 are cut and reheated after the drawing process to produce the curled tip in the yarns, without being placed onto the rubber backing. Accordingly, attachment to the rubber backing is not necessary to effect the curled tip in the yarns. In this embodiment, the yarns 202 are laid out on a tray and heated in the curing ovens as described above.
According to one embodiment of the present invention, before the single strand synthetic yarns 202 are attached to a backing for use as synthetic turf, the yarns are wound together to form multiple strand synthetic yarn combinations via a winder 70 (not shown). Also, because yarns produced by embodiments of the present invention are individual, discrete, and smooth, they often are twisted around a roller with two bookends similar to a spool via a twister 80 to keep the yarns from sliding off the spool, and the spool is used to transport the yarns for further processing (not shown).
The foregoing description of the exemplary embodiments of the invention has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.
The embodiments were chosen and described in order to explain the principles of the invention and their practical application so as to enable others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.

Claims

1. A system for manufacturing single strand synthetic yarns for synthetic turf, comprising:

a plurality of rollers for advancing a sheet of plastic along a predetermined path within the apparatus;

a slitting component for receiving the plastic sheet and slitting the plastic sheet longitudinally along the length of the sheet to form a plurality of single strand synthetic yarns as the plastic sheet advances along the predetermined path; and

a drawing component positioned along the predetermined path after the slitting component for pulling the plurality of single strand synthetic yarns under tension and heat to stretch and thin the yarns and further to round the edges of the yarns.

2. The system of claim 1, further comprising a plurality of differential temperature rollers for alternatively heating and cooling opposing sides of the plastic sheet before the plastic sheet is cut by the slitting component.

3. The system of claim 2, wherein the plurality of differential temperature rollers alternatively cool one side of the plastic sheet to a temperature of about 25° C. and heat the other side of plastic sheet to a temperature of about 35° C.

4. The system of claim 2, further comprising a reheating component for reheating the plurality of single strand synthetic yarns after the yarns have passed through the drawing component and after the yarns have been cut to predetermined lengths, wherein the reheating causes the ends of the cut yarns to curl.

5. The system of claim 1, wherein the slitting component comprises a plurality of slitting blades that engage and continuously cut the plastic sheet into the plurality of single strand synthetic yarns as the sheet advances along the predetermined path.

6. The system of claim 5, wherein the plurality of slitting blades are spaced apart at a predetermined equal distance between about 1.0 mm to about 6.0 mm.

7. The system of claim 5, wherein the plurality of slitting blades are spaced apart at a plurality of different distances to create single strand synthetic yarns of a corresponding plurality of widths.

8. The system of claim 5, further comprising a first pulling and tensioning roller positioned to contact the plurality of single strand synthetic yarns at a distance less than or equal to 1.0 inch after the slitting blades to maintain tension on the yarns.

9. The system of claim 8, further comprising a second pulling and tensioning roller positioned opposite the first pulling and tensioning roller such that the plurality of single strand synthetic yarns are pinched between the first pulling and tensioning roller and the second pulling and tensioning roller to maintain tension on the yarns.

10. The system of claim 9, wherein the second pulling and tensioning roller is positioned at a predetermined distance from the first pulling and tensioning roller along the predetermined path.

11. The system of claim 1, wherein the plastic sheet advances through the slitting component at a speed of about 16.6 m/min.

12. The system of claim 1, wherein the drawing component includes a drawing oven for heating the plurality of single strand synthetic yarns and a plurality of drawing rollers adapted to stretch and shape the plurality of single strand synthetic yarns.

13. The system of claim. 12, wherein the drawing oven heats the single strand synthetic yarns to a temperature between about 90° C. to about 110° C.

14. The system of claim 12, wherein at least one of the plurality of drawing rollers heats the plurality of single strand synthetic yarns and wherein at least one of the plurality of drawing rollers cools the plurality of single strand synthetic yarns after the yarns exit the drawing oven.

15. The system of claim 14, wherein the plurality of single strand synthetic yarns are heated by a heated drawing roller to a temperature between about 90° C. to about 110° C. and are cooled by a cooled drawing roller to a temperature of about 25° C.

16. The system of claim 1, wherein the drawing component pulls the plurality of single strand synthetic yarns under tension with a draw ratio of about 6:1.

17. The system of claim 1, wherein the plastic sheet provided to the slitting component has a width between about 0.5 m to about 3.0 m and a thickness between about 50 microns to about 5.00 microns.

18. The system of claim 1, wherein the plurality of single strand synthetic yarns have a width between about 0.5 mm to about 3.0 mm and a thickness between about 25 microns to about 150 microns after the yarns have been formed by the slitting component and heated and stretched by the drawing component.

19. The system of claim 1, further comprising a winder to wind the plurality of single strand synthetic yarns together to form multiple strand synthetic yarn combinations after the yarns have been drawn by the drawing component and a twister to wrap the multiple strand synthetic yarn combinations around a flanged spool for further processing.

20. The system of claim 1, wherein the plastic sheet comprises linear low density polyethylene (LLDPE), polypropylene, nylon, or any combination thereof.

21. A system for manufacturing single strand synthetic yarns for synthetic turf, comprising:

a plurality of pulling and tensioning rollers for advancing a plastic sheet along a predetermined path within the system;

a series of alternating temperature rollers for heating and cooling opposing sides of the plastic sheet as the sheet advances along the predetermined path;

a plurality of slitting blades for slitting the plastic sheet to form a plurality of single strand synthetic yarns after the plastic sheet has passed around the alternating temperature rollers, wherein the slitting blades engage and continuously cut the plastic sheet as the sheet is advanced along the predetermined path;

a drawing oven for heating the plurality of single strand synthetic yarns once the yarns have been cut by the slitting blades, wherein the drawing oven heats the plurality of single strand synthetic yarns to assist in a heated stretching of the yarns; and

a series of drawing rollers adapted for tensionally pulling the plurality of single strand synthetic yarns through the drawing oven to produce the heated stretching of the yarns, wherein the heated stretching elongates and shapes the yarns and additionally rounds the edges of the yarns.

22. The system of claim 21, further comprising a reheating component for reheating the plurality of single strand synthetic yarns after the yarns have passed through the series of drawing rollers and after the yarns have been cut to predetermined lengths, wherein the reheating causes the ends of the cut yarns to curl.

23. The system of claim 21, wherein at least one pulling and tensioning roller is positioned to contact the plurality of single strand synthetic yarns at a distance less than or equal to 1.0 inch after the slitting blades to maintain tension on the yarns.

24. The system of claim 21, wherein at least one drawing roller in the series of drawing rollers heats the plurality of single strand synthetic yarns and wherein at least one drawing roller in the series of drawing rollers cools the plurality of single strand synthetic yarns after the yarns exit the drawing oven.

25. The system of claim 21, wherein the plastic sheet comprises linear low density polyethylene (LLDPE), polypropylene, nylon, or any combination thereof.

26. A method for manufacturing single strand synthetic yarns for synthetic turf, comprising the steps of:

advancing a plastic sheet along a predetermined path;

slitting the plastic sheet longitudinally into a plurality of single strand synthetic yarns, wherein the plastic sheet is slit at a set point along the predetermined path as the plastic sheet advances along the predetermined path; and, thereafter,

drawing the plurality of single strand synthetic yarns under tension and heat to stretch and thin the yarns and further to round the edges of the yarns.

27. The method of claim 26, further comprising the step of alternatively heating and cooling opposing sides of the plastic sheet before the sheet is slit into the plurality of single strand synthetic yarns.

28. The method of claim 27, wherein the plastic sheet is alternatively cooled to a temperature of about 25° C. and heated to a temperature of about. 35° C.

29. The method of claim 27, further comprising the step of cutting the plurality of single strand synthetic yarns to desired lengths after the yarns have been drawn and attaching the cut single strand synthetic yarns to a backing.

30. The method of claim 29, further comprising the step of reheating the cut single strand synthetic yarns before the yarns have been attached to the backing to produce a curled shape in the yarns.

31. The method of claim 29, further comprising the step of reheating the cut single strand synthetic yarns after the yarns have been attached to the backing to produce a curled shape in the yarns.

32. The method of claim 26, wherein the plastic sheet advances along the predetermined path at a speed of about 16.6 m/min.

33. The method of claim 26, wherein the step of slitting the plastic sheet includes continuously slitting the sheet at the set point as the plastic sheet advances along the predetermined path.

34. The method of claim 26, wherein before the plastic sheet is slit the sheet has a width between about 0.5 m to about 3.0 m and a thickness between about 50 microns to about 500 microns.

35. The method of claim 26, wherein the plurality of single strand synthetic yarns are slit such that each single strand synthetic yarn has a width of between about 1.0 mm to about 6.0 mm before the plurality of single strand synthetic yarns are drawn.

36. The method of claim 26, wherein the plurality of single strand synthetic yarns have a width between about 0.5 mm to about 3.0 mm and a thickness between about 25 microns to about 150 microns after the yarns have been slit and drawn.

37. The method of claim 26, further comprising the step of contacting and pulling the plurality of single strand synthetic yarns along the predetermined path immediately after the yarns have been slit to maintain tension on the yarns as the yarns progress along the predetermined path, wherein the contacting and pulling occurs at a point along the predetermined path less than or equal to 1.0 inch after the set point at which the plurality of single strand synthetic yarns are slit.

38. The method of claim 26, wherein the plurality of single strand synthetic yarns are drawn at a draw ratio of about 6:1.

39. The method of claim 26, wherein the plurality of single strand synthetic yarns are heated to a temperature between about 90° C. to about 110° C. while being drawn.

40. The method of claim 26, wherein the step of drawing the plurality of single strand synthetic yarns further comprises the step of cooling the plurality of single strand synthetic yarns after the yarns have been heated and stretched.

41. The method of claim 40, wherein the plurality of single strand synthetic yarns are cooled to a temperature of about 25° C.

42. The method of claim 26, further comprising the step of winding the plurality of single strand synthetic yarns together to form multiple strand synthetic yarn combinations after the yarns have been drawn and twisting the multiple strand synthetic yarn combinations together for further processing.

43. The method of claim 26, wherein the plastic sheet comprises linear low density polyethylene (LLDPE), polypropylene, nylon, or any combination thereof.

44. A single strand synthetic yarn manufactured according to the method described in claim 26.

45. A method for manufacturing single strand synthetic yarns for synthetic turf, comprising the steps of:

advancing a plastic sheet along a predetermined path;

alternatively heating and cooling opposing sides of the plastic sheet;

slitting the plastic sheet into a plurality of single strand synthetic yarns after the opposing sides of the plastic sheet have been alternatively heated and cooled, wherein the plastic sheet is continuously slit at a set point along the predetermined path as the plastic sheet advances along the predetermined path;

heating the plurality of single strand synthetic yarns once the yarns have been cut from the plastic sheet by the slitting blades, wherein the yarns are heated to assist in a heated stretching of the yarns; and, thereafter

pulling the plurality of single strand synthetic yarns under tension and heat to generate the heated stretching of the yarns, wherein the heated stretching elongates and shapes the yarns and additionally rounds the edges of the yarns.

46. The method of claim 45, further comprising the step of cutting the plurality of single strand synthetic yarns to desired lengths after the yarns have been pulled under tension and heat and attaching the cut single strand synthetic yarns to a backing.

47. The method of claim 46, further comprising the step of reheating the cut single strand synthetic yarns before the yarns have been attached to the backing to produce a curled shape in the yarns.

48. The method of claim 46, further comprising the step of reheating the cut single strand synthetic yarns after the yarns have been attached to the backing to produce a curled shape in the yarns.

49. The method of claim 45, further comprising the step of contacting and pulling the plurality of single strand synthetic yarns along the predetermined path immediately after the yarns are slit to maintain tension on the yarns as the yarns progress along the predetermined path, wherein the contacting and pulling occurs at a point along the predetermined path less than or equal to 1.0 inch after the set point at which the plurality of single strand synthetic yarns are slit.

50. The method of claim 45, wherein the step of pulling the plurality of single strand synthetic yarns under tension and heat further comprises the step of cooling the plurality of single strand synthetic yarns after the yarns have been heated and stretched.

51. The method of claim 45, wherein the plastic sheet comprises linear low density polyethylene (LLDPE), polypropylene, nylon, or any combination thereof.

52. A single strand synthetic yarn manufactured according to the method described in claim 45.