Non-directional rectangular filaments and products

Disclosed herein are novel synthetic polymer filaments, and yarns made therefrom, for use in synthetic turf products. The filaments have a rectangular cross-section and the normal directional tendency of such filaments when used in synthetic turf is overcome by folding or texturing the filaments in such a manner that, while the normal advantageous flexibility of the rectangular filament is retained, the directional tendency is removed. When filaments of the invention are used to produce synthetic turfs, the turf surface imparts an essentially non-directional response to objects rolled thereon.

BACKGROUND OF THE INVENTION 
This invention relates to synthetic polymer filaments of rectangular 
cross-section which have been textured in such a manner as to render them 
essentially non-directional and suitable for use in synthetic turf 
products, such as golf greens. 
A considerable commercial interest has developed in synthetic or man-made 
turfs. Fur example, the product disclosed in U.S. Pat. No. 3,328,828 
consists of filaments which are tufted into a backing. To resemble natural 
turf, the filaments must be of heavy denier (e.g., 100 or above). However, 
with such large filaments, flexibility becomes a problem which is overcome 
by the use of filaments with a rectangular cross-section (width/thickness 
&gt;3/1). However, rectangulr filaments have a tendency to bend only along 
the longitudinal axis and this tendency increases as the size of the 
filament increases. i.e., the rectangular filaments are said to have a 
directional character. After tufting, weaving, or knitting to form turf, 
the flat rectangular, ribbon-like filaments are oriented uniformly with 
the result that the pile lays preferentially in the direction 
corresponding with the directional tendency of the filaments. It can be 
seen intuitively that in stroking an object across the pile surface, such 
as a golf ball, if the ball is stroked with the pile lay, the surface will 
roll much faster than if the ball is stroked against the pile lay. A ball 
stroked at an angle to the pile lay will tend to deviate from its natural 
course. 
To overcome the directional drawbacks of large rectangulr filaments, it has 
been suggested (e.g., see U.S. Pat. No. 3,565,742) that short lengths of 
filaments be flocked onto an adhesive-covered backing to achieve a more 
random orientation of the filaments. This procedure, however, cannot be 
performed on conventional tufting, knitting, or weaving machinery. Many 
other techniques have also been tried to minimize the directional 
tendencies of the synthetic turf surface. See, for example, U.S. Pat. Nos. 
3,513,061 and 3,513,062. 
Another problem associated with large rectangular filaments, in addition to 
their tendency to bend only along the longitudinal axis, is the low 
covering power of such filaments. To overcome this problem in artificial 
turf, U.S. Pat. No. 3,681,912 suggests texturing the filaments by twisting 
the filaments and passing the filament edges over a heated surface. 
Intuitively, it can be seen that this process imparts a relatively small 
and uniform amount of texturing to the filaments, i.e., it is questionable 
how much the natural stiffness and directional tendencies of the filaments 
are reduced. Additionally, such processes are generally not suitable to 
high speed performance.

DESCRIPTION OF THE INVENTION 
The invention overcomes difficulties associated with the prior art by 
forming synthetic turf from continuous ribbon filaments of at least 100 
denier each characterized by major (longitudinal) and minor (lateral) 
axes. As viewed laterally along the minor axis, the fibers have an 
essentially rectangular cross-sectional area. To overcome the directional 
tendency of the rectangular filaments, each filament is textured to 
provide a plurality of folds wherein both the major and minor axes bend 
simultaneously to show the major longitudinal plane of the filament at an 
angle with respect to portions of the plane on the other side of the fold. 
The folds are randomly oriented with respect to one another (i.e., they 
appear irregularly in the filament) and it has been found that the 
presence of such folds overcomes the natural directional flexibility of 
the rectangular cross-section and imparts a substantially universal, 
non-directional flexibility to the filaments. 
To better illustrate the invention, reference is made to FIG. 1a depicting 
prior art synthetic turf having large (e.g., above 100 denier) rectangular 
filaments. In filament 10 when a force 12 is applied, the filament tends 
to bend along the longitiudinal axis 14 rather than along the lateral axis 
16. If a force 18 is applied to filament 10, against the lateral axis, 
bending is resisted, although, of course, the filament will bend if the 
force is sufficiently large. By contrast, in FIG. 1b, depicting the 
invention, the filament 30 has several folds 32 wherein both the major 
axis 34, and the minor axis 36 bind simultaneously to skew or twist the 
major longitudinal plane 37 of a filament at an angle with respec to other 
portions of the same plane. For example, plane 37a forms an angle of 
approximately 90.degree. with 37b and the angle between 37b and 37c is 
somewhat greater than 90.degree.. It should also be understood that the 
portions of plane 37 (37a, 37b, 37c) need not be in the same vertical 
plane, i.e., the folds impart a three dimensional nature to the filament. 
This is shown in FIG. 1c which is a side view of 1b as viewed along arrow 
38. It is the simultaneous bending of both the major and minor axes which 
imparts to filaments of the invention a three dimensional nature and a 
texture and "feel" resembling natural turf. 
In addition, the simultaneous bending of the filament axes gives the 
filaments an essentially non-directional nature when employed as piling in 
synthetic turf products. With reference to FIG. 1d, the filament 30 has 
several three-dimensional folds 32 which due to the simultaneous bending 
of the filament axes, resemble universal joints in the sense that they can 
be distorted, either singly or in combination to flexibly accommodate a 
force 33 applied from any direction with the result that the filament is 
distorted, for example, to assume positions such as shown at 35 and 39. 
Because of the system of three-dimensional folds, whatever stiffness is 
present, because of the rectangular cross-sectional of the filament, is 
turned into an advantage because as the force 33 is applied, it is 
transmitted along the filament to the joint or fold area 32 where the 
filament bends to accommodate the force. If the fold cannot fully 
accommodate the force applied, the residual is transmitted further along 
the filament to other folds were further distortion can take place. As a 
result, the filament is relatively uniformly flexible in any direction 
and, when used in synthetic turf, provides an essentially non-directional 
response to objects such as golf balls, rolled across the surface of the 
turf. 
In another embodiment of the invention, with reference to FIG. 2, the 
non-directional filaments are tufted into a backing 40 on conventional 
machinery with the loops being cut to form a synthetic turf with a 
cut-pile surface, indicated generally at 42. Because of the folds 
described above, after cutting the individual filaments of the cut pile 
"bloom" appreciably and achieve a very random orientation, although, of 
course, they have been tufted into the backing 40 in the conventional 
oriented manner. The random orientation of the filaments of the invention 
is particularly significant in that a large number are oriented generally 
parallel to the surface of the backing so that the sides and edges of the 
filaments form part of the cut pile surface with the filament ends being 
buried in the pile. This last factor is very important because directional 
tendencies associated with the presence of the filament ends at the 
surface are thereby reduced. The filament folds, besides resulting in a 
large number of buried ends, also greatly reduce the stiffness of filament 
ends present at the surface. Also, the covering power of the folded 
filaments is quite high with the synthetic turf showing little or no 
"grinning" through. This permits the filaments to be employed in reduced 
amounts, e.g., synthetic turf made with from 20 to 30 oz./square yard 
compared favorably in covering power with conventional synthetic turf 
formed from untextured rectangular filaments employing from 38 to 42 
oz./yard. 
Although essentially level, the overall pile surface 42 is relatively rough 
in comparison with a cut-pile surface formed from untextured ribbons. 
However, due to the relative absence of ends and the reduced stiffness of 
the filaments, the pile surface greatly resembles natural turf in 
appearance and also in its performance characteristics. For example, with 
regard to an object rolled across the surface of the turf such as a golf 
ball, the surface does not impart abnormal acceleration or deceleration to 
the ball and, as said above, is also essentially non-directional. 
The novel filaments of the invention are prepared by the process depicted 
in FIG. 3 and described in more detail in U.S. Pat. No. 3,832,759. With 
reference to FIG. 3, yarn 10 is drawn into an aspirator indicated 
generally at 11, by a venturi cup 12. Air for the venturi 12 is supplied 
through an air inlet 13 in the jet housing 14. The feed yarn is propelled 
by air through chamber 12a into the crimping tube 15 which has an enlarged 
diameter compared with chamber 12a. Also, air used to propel the yarn is 
allowed to escape through exhaust ports 16 in crimping tube 15. Due to the 
escape of air and the enlarged diameter of tube 15, the yarn is not 
propelled through tube 15 with the same velocity as in chamber 12a and, 
therefore, begins to fold back upon itself forming a series of random 
folds 10a. The yarn also impinges upon the walls of tube 15 which also 
increases the folding action. At this point, the yarn has achieved 
considerable bulk, but due to the absence of mechanical crimping elements 
such as are used, for example, in gear crimping, the surface of the yarn 
is relatively free of abrasion and also retains a generally rectangular 
configuration. The absence of abrasion is important because in synthetic 
turf products, the yarn is exposed to large amounts of UV radiation, 
ozone, oxygen, etc., and surface abrasions provide ideal starting points 
for deterioration of the yarn. 
The folds obtained in tube 15 are set in accumulator tube 17 by the 
introduction of steam through hollow arm 19. The velocity of the steam 
also tends to further crimp the yarn filaments but is primarily to set the 
crimp already developed in tube 15. The yarn passes from tube 17 and is 
placed under sufficient tension to permit take-up by a conventional 
winding apparatus (not shown). In the absence of tube 15, the ultimate 
bulk level imparted to the filaments would be considerably less, i.e., 
more nearly comparable to normal "stuffer box" processing. 
With reference to FIG. 4, it will be seen that after take-up, the 
individual filaments are physically separate and unbonded, but are also 
entangled with one another. Each filament has a number of folds 
distributed randomly along its length. The filaments are also 
substantially free of ring-like loops. With reference to FIG. 5, the 
filaments have a generally rectangular or ribbon-like cross-section (FIG. 
5c). Also, while the sheen normally associated with synthetic filaments is 
reduced to a great degree by texturing, it may be reduced still further if 
desired by imparting longitudinal ribs to the filament during extrusion as 
seen in FIGS. 5a and 5b. 
Of particular interest in fabricating synthetic turf products, it has been 
discovered that filaments textured as depicted in FIG. 3 contain a large 
residual shrinkage of 5.0% or more which is developed by application of 
heat. For example, immediately following texturing, the filaments have a 
wet bulk level of from 28% to 33% which is measured by the test described 
below and calculated as follows: 
##EQU1## 
However, after the filaments have been tufted to form cut-pile synthetic 
turf, and the turf is heated in an oven set at about 130.degree. C., the 
pile height as measured from the top of the backing to the cut-pile 
surface, has been found to shrink by as much as 20 to 25%, and preferably 
from 35 to 40%. Likewise, this phenomenon is also observed by heating 
yarn, or individual filaments which have been textured, at a temperature 
of 138.degree. C. for about 3 minutes. The shrinkage is believed to be due 
to the relatively large amount of latent, permanent crimp developed in the 
filaments by the texturing method described in FIG. 3. This high shrinkage 
and latent permanent crimp is unexpected because in view of the speed with 
which the filaments are textured, i.e., from 500 to 1000 m/minute, and the 
very large size of the filaments, it was not anticipated that the heat 
history of the filaments would be sufficient to impart such a high degree 
of shrinkage or latent permanent crimp. 
The wet bulk level test referred to above was developed to determine the 
bulk (or crimp) developed in a synthetic carpet yarn that has been crimped 
by stuffer box or steam. The procedure for measuring the wet bulk is as 
follows: A glass tube 7 cm. in diameter and 60 cm. in height is filled 
with distilled water to a point within 0.5 - 1.0 cm. of its top. The water 
is preheated to 158.degree. F. for nylon or 206.degree. F. for polyester 
by a 600-watt cylindrical heater controlled by a Variac variable resistor. 
Using 3 grams pretension, a length of yarn is wound on a skein holder into 
a skein having a circumference of about one meter. The amount of yarn in 
the skein is equal to: 
##EQU2## 
The skein is held by a suitable hook and weighted with a 4.5 gram weight. 
The skein is measured to the nearest tenth of a centimeter (i.e., 1/2 the 
circumference) and then placed in the preheated water bath. At the end of 
30 seconds, the skein length is again read to the nearest tenth of a 
centimeter. 
Suitable filaments are those with a denier of at least 100 and may have a 
denier of 350 or greater, but preferably from 225 to 250, which are 
extruded from polyamides, polyesters, and polypropylene, e.g., nylon 6, 
nylon 66, nylon 6, nylon 610, and nylon 11, and their filament forming 
copolymers. If found advantageous, the filaments may be treated with 
surfactants, or other means, to roughen the surface sufficient to aid 
fabrication thereof and prevent footwear slippage. The ribbon should be 
drawn and treated to provide the physical properties desired depending 
upon the polymer composition and the utilization planned for the turf. 
Preferably, the thermoplastic material is pigmented green to simulate the 
color of grass, although other colors may be used for special effects. 
It is known that the addition of certain pigments to thermoplastic 
materials such as nylon and polyester may increase its resistance to 
degradation by ultraviolet light, although many pigments, particularly 
inorganic materials, tend to accelerate such degradation. It has been 
found that a mixture of about 0.50 percent of a phthalocyanine green and 
1.50 percent of a cadmium yellow based on polymer weight provides good 
color depth and sufficient stabilization against ultraviolet light for 
most applications. 
Phthalocyanine green refers to the well-known chlorinated copper 
phthalocyanine chelate compounds widely used to colorant; for example, 
Monastral Green and Mapaco Green pigments made by E. I. du Pont de 
Nemours, Pigment Department, Wilmington, Del. Cadmium Lithopone yellow 
designates the common yellow inorganic pigments consisting principally of 
cadmium sulfide. The cadmium yellow pigments supplied by the Glidden 
Company, Baltimore, Md., and by Kentucky Color Company, Louisville, Ky., 
have proven quite satisfactory. 
If desired, the nylon may be further stabilized by the incorporation of any 
of a number of well known UV absorbers which are compatible with the 
resin. These include such compounds as the aryl esters of phosphoric acid, 
the alkaryl phosphinates, zinc phosphates, manganous salts, chromium 
salts, and copper salts. For optimum water resistance properties, the 
nylon ribbons should be placed under the minimum tension possible. 
The backing material may be formed with fibers prepared from polyesters, 
polyacrylonitrile, polypropylene and nylon. Formation of the backing may 
be accomplished by weaving and knitting or any of the known processes for 
preparing nonwovens, particularly needle punching. The backing fibers are 
preferably green solution dyed to add color depth to the turf and thus 
enhance the grass-like appearance thereof where this result is desired; 
however, white or conventionally dyed fibers of green or other colors may 
be employed. 
Synthetic turf products of the invention normally have a face pile height 
of between 1/4 inch and 3/4 inch with a face density between 20 and 42 
ounces per square yard, and most often about 30 ounces per square yard. 
The exact pile height desired is, of course, determined by the particular 
utilization of the turf. For general playground activities such as tennis, 
volleyball, baseball, softball, touch football, soccer, and badminton, a 
pile height of about 1/4 to 1/2 inches is preferred. For other 
applications such as tee-off pads on golf driving ranges and par-3 
courses, a turf having a nylon pile height of about 1/2 to 3/4 inches is 
preferred. A backing composed of fibers woven into a fabric having 18 
.times. 18 (18 warp ends and 18 filling ends) with 3 ounces per square 
yard is satisfactory for most common applications. 
Synthetic turf can be fabricated by weaving, tufting, or knitting. Tufting 
is the preferred method and is carried out, for example, by tufting 10 to 
20 monofilament ribbons on a 5/32 gauge machine at a density of about 30 
ounces per square yard into a woven or nonwoven backing fabric. Suitable 
backing fabrics include 5 to 10 ounces per yarn nylon scrim reinforced 
needle punched fabric formed from acrylic staple fibers which has been 
treated with about 1.5 ounces per square yard of an 80/20 mixture of Hycar 
1571 and Resloom M-80 resin. Hycar 1571 is a water emulsion of 
butadiene-acrylonitrile copolymer sold by B.F. Goodrich Chemical Co., 
Cleveland, Ohio, and Resloom M-80 is a melamine-formaldehyde resin sold by 
Monsanto Co., St. Louis, Mo. 
Another backing material suitable for tufting is a nylon scrim reinforced 
polyurethane foam carpet backing which is marketed under the trademark, 
Chemback, by the Chemstrand Co., Division of Monsanto Company. Chemback is 
comprised of an open-mesh woven nylon scrim coated with foamed 
polyurethane having a density of approximately 2 lbs. per cubis foot. 
Chemback is produced in thicknesses of approximately 0.06 to 0.10 inch and 
in weights of 3 to 6 ounces per square yard. 
After weaving, knitting, or tufting the face ribbon with the backing to 
produce a turf fabric, a solution of latex or the like is applied to the 
back of the fabric by padding or spraying, although other methods may be 
used to achieve acceptable results. The latex provides dimensional 
stability to the fabric and also serves to anchor the ribbons in the 
backing material. It must, therefore, be of a composition which has good 
adhesion to both the synthetic ribbons and the synthetic backing material. 
One such latex composition is a dispersion of Lotol 7562, Pyratex Dow 
Corning Antifoam, and Alcogum. Other suitable latex formulations are 
described in Column 4, lines 21 et. seq. of U.S. Pat. No. 3,332,828, and 
are expressly incorporated by reference into the present disclosure. 
As further illustration of the invention, flat monofilament ribbons of 
nylon 6 were prepared by dry blending nylon 6 chips with phthalocyanine 
green pigmented chips and extruding this mixture by conventional melt 
extrusion techniques. The resulting grass green filaments, which were 
0.1785 inch wide by 0.0049 inch thick (250 denier), were collected in 
water, dried, drawn at a ratio of 3.7 to 1 and taken up as a bundle of 18 
filaments. The cross-sectional configuration was essentially as depicted 
in FIG. 5a. The filaments were textured according to the method depicted 
in FIG. 3 at a rate of 600 meters/minute. The air pressure entering at 
inlet 13 was 80 p.s.i., steam pressure was 9 p.s.i., the diameter of 
accumulator chamber 17 was 0.75 inch. The wet bulk level of the yarn 
bundle was 18 to 25% measured as above. 
A cut pile synthetic turf was fabricated using a conventional tufting 
machine with the machine set at 7 stitches per inch. 5/32 gauge. The pile 
was about 1/2 inch in height at a weight of 26 ounces/square yard. The 
backing was woven polypropylene of 18 .times. 18 construction (as 
explained heretofore). A latex adhesive was applied to the underside of 
the backing and the turf product was cured in an oven at about 280.degree. 
F. for about 3 minutes to dry the latex. Drying also developed latent 
crimp in the pile causing a shrinkage of 25% to 3/8 inch in height. 
The cured turf product substantially resembled that depicted in FIG. 2 with 
the pile showing very good coverage with little, if any, "grinning" 
through, even when the turf was folded back upon itself so that the two 
folded sides were almost flush one with another leaving only a small loop 
along the fold line. 
When viewed by a person standing thereon, the turf product has a very close 
resemblance to natural turf and in addition the performance 
characteristics very closely resemble those observed with natural turf. 
For example, when employed as a synthetic golf green, the turf product did 
not provide either abnormal acceleration or deceleration to golf balls and 
did not appear to cause the balls to deviate from the direction in which 
they were stroked, i.e., the cut pile surface appeared to be essentially 
non-directional.