Note: Descriptions are shown in the official language in which they were submitted.
M~LT-DR~ING, COOLING, ~TTE'N~i~rrIN~,
AND FIEAT TREATING UN~ER TE~SIOM, OF FILAMENT
BACKGROUND
Nylon fiber is one of the most versatile and useful
man-made fibers developed to date. In its monofilament form
it is bulked by crimping and the crimped filament is twisted
to~ether with other bul~ed monofilaments to form a nyloJl yarn
which is particularly suited for carpets. These nylon yarns,
when tufted through a suitable backing, form a pile fabric
that has excellent wearability and a good hand, i.e., it is
pleasant to the touch.
Since the cost of nylon has increased substantially over
the past few years, lower cost substitutes having physical
characteristics similar to that of nylon are being sought.
Polypropylene yarns recently have been introduced which for
some applications serve as a substitute for nylon carpet yarns.
TG date carpets employing polypropylene face yarns have made
modest penetration of the market, and polypropylene yarns
now represent approximately 5 percent of the face yarns used
in the manufacture of carpets.
THE INVENTION
I have invented a novel monofilament fiber made of low
cost polymeric material. My fiber is characterized by having
an elastic modulus of from abou~ 5,000 to about 60,000 psi,
an area moment of inertia of from about 400 x 10 14 to about
7,000 x 10 1 in4, and a stiffness parameter (as d~fincd belo~)
of from about 1 x 10 5 to about 1 x 10 8 lb - in . Elastic
modulus is determined by measuring the initial slope of the
stress-strain curve derived according to ASTM standard method
9~"
Y ,f~ -~
No. D2256-69. Strain measurements are corrected for gauge
length variations by the methocl described in an article en-
titled "A ~lethod for Determining Tensile Strains and Elas~ic
~lodulus of ~letallic ~ilaments," AS~I Trans~ctions Quarterly,
Vol. 60~ No. 4, December 1967J PP. 726-27.
The chief criterion for selecting a polymeric material
is its elastic modulus. The best material so far uncovered
is an ethylene-vinyl acetate copolymer having a vinyl acetate
content ranging from about 1 to about 10 percent by weight
and a melt index of from about 0 5 to about 9. This material
will provide the monofilament with the desired elastic
modulus and is also relatively inexpensive. The following
thermoplastic materials will provide the monofilament with
an elastic modulus within the range of from 5,000 to 60,000
psi: (a) plas~icized polyvinyl chloride, (b) low density
polyethylene, (c) thermoplastic rubber, (d) ethylene-ethyl
acrylate copolymer, (e) ethylene-butylene copolymer, (f)
polybutylene and copolymers thereof, (g) ethylene-propylene
copolymers, (h) chlorinated polypropylene, (i~ chlorinated
polybutylene, or (j) mixtures of these thermoplastics.
Although the ethylene-vinyl acetate copolymer has
the desired elastic modulus, one problem with this material
is that it has a relatively low melting point. To ob-
viate this problem and increase the heat resistance of the
fiber, the molecules of the copolymer are cross-linked.
Cross-linking may be achieved either during the manufacture
3 I~ 3982-O-USA
~ ~. ~
~9;~1~
of the fiber or subsequently. Conventional irradiation
tecl-niques may be employed or the molecules of the polymer
may include moieties which react under selected conditions
with other molecules to effect cross-linking. As l~ill be
discussed below in detail, it is desirable to use certain
additives ~hich greatly enhance cross-linking. Only partial
cross-linking is desired so that the material retains the
required elastic properties. Ordinarily, cross-linking
increases the melting point of tihe material so that it is
200F or greater.
The fiber of this invention makes an excellent carpet
yarn when twisted together with other monofilament fibers
of my invention and bulked. Such yarn, tufted or other-
wise formed into a pile fabric, forms a plush pile surface
having a hand similar to that of pile surfaces formed from
conventional nylon carpet yarns. It also has the other
necessary physical properties ~o serve as a carpet yarn.
PHYSICAI, PROPERTIES OF FIBER
My fiber has good hand, resists matting, wears well,
and is tuftable or may otherwise be processed using con-
ventional carpet making techniques. All these properties
are necessary for the fiber to give satisfactory per-
ormance in carpets. Moreover,it has good anti-static
properties and is easy to clean because of its large
diameter.
~ I~ 3982-0-USA
Hand
~ land is simply how the fiber feels. I~hen considering
the hand of any fiber, one must take into account the
speciic textile construction in which the hand is being
judged Since I believe my fiber will be used mainly in
carpe~ yarn, I have built into it those physical properties
which will impart good hand to the fiber in a pile construc-
tion. In such a construction the fiber acts under loads
like an upright column. In other words, when one touches
the fiber, a downward force is exerted on the upright fibers.
At a critical load the fibers will buckle or bend. The
more rigid or stiff the fibers, the greater the load required
to bend the fibers. Good hand is associated ~ith fibers
that are pliant.
Although other factors affect the hand of pile fabrics,
the chief factor is the fiber stiffness which is a function
of the material properties of the fiber, the geometry of
the fiber, and the manner in which load is applied to the
fiber. In general terms, one may compare the hand of
diferent fibers by comparing the stiffness parameter (Kf)
of the fibers, where each ~iber has a uniform cross-section
and is composed of the same material throughout. This stiff-
ness parameter is the product of the elastic modulus (Ef)
of the fiber and the area moment of inertia (If) of the
fiber:
Kf = Ef x If
ID 39~2-O-US/\
i~ 218
Historically, man-made fibers have been engineered so
that the physical properties of such fibers are about the
same as textile fibers ound in nature, for example,
cotton or wool. Natural textile -fibers are generally thin,
having a diameter less than about 2 mils, and have a high
elastic modulus (Ef), for example, a modulus greater than
about 200,000 psi. Thus, synthetic fibers are thin and
have a high modulus. Such thin, high modulus fibers have
a stiffness parameter (Kf) generally ranging between about
1 x 10 5 and about 1 x 10-8 lbs-in2. In general, any
fiber having a stiffness factor (Kf) witllin this range will
feel soft and pliant. Note, because conventional fibers
have a relatively high elastic modulus, usually well above
200,000 psi, they must have a relatively lol- moment of
inertia, otherwise they would feel too stiff.
Under normal loading conditions, ibers bend about
a neutral axis where the moment of inertia will be a minimum
value. The moment of inertia (If) about this neutral axis
is calculated using the following equation:
20If = S y2dA
where dA is any incremental area of the fiber's cross-
section and y is the distance any such incremental area is
from the neutral axis. The above equation illustrates that
the moment of inertia of the fiber is a function of the
Z5 fiber's cross-sectional configuration. Thus, the hand of
a fiber may be altered by changing the cross-sectional
configuration of the fiber. Specific examples of fibers
having different cross-sectional con~igurations and the
6 IU ~a~ A
specific equations for calculating the moments of inertia
for such fibers are ~iven in a paper presented at the 47th
annual meeting of the AST~I, Vol 44, (1944).
The cross-sectional configuration of my fiber is not
critical so long as the moment of inertia falls within the
range of from about 400 x 10 to about 7,000 x 10-14 in4.
However, my fiber preferably has a generally circular cross-
section. For fibers with a uniform circular cross-sectional
configuration, the moment of inertia (If) may be calculated
by the following formula:
~d4
If = . __
64
where d is the fiber diameter. Consequently, to have the
required moment of inertia (If), such a fiber would have
a diameter in a range of from about 3 to about 6 mils, pre-
ferably from about 4 to abou~ 5 mils. In terms of denier,
my iber usually has a denier of from 25 to 150 for fibers
made of material having a specific gravity in the range of
rom about 0.90 to about 1;4.
Table I belol~ compares the stiffness parameter (Kf) of
conventional nylon and polypropylene fibers and the fibers
of my invention, all having circular cross-sections. Note
the (Kf) of all the fibers are within the range of from
about l x 10-5 to about 1 x 10-8 lb-in2, but the diameter,
.,
and consequently the If, for my fiber ~lmLD) is significant-
ly larger than conventional fiber and the (Ef) of my fiber
is substantially lower than conventional fiber.
ID 398~-O-USA
~1~
T AnLE I
Comparative Values of Kf for Conventional
Fibers and the Fiber o~ thc Prescnt Inv~ntion
Fib r (in)(in4)~10~l4(lb/in2)(lb-in2)xlO~8
Nylon 0.0014.908 250,000 1.227
0.0014.9n8 sn() ~ nnn ~ 4
0.001524.850 250,000 6.212
0.001524.850 500,000 12.425
Polypropylene 0.002 78.539 250,000 19.635
0.00278.539 300,000 23.562
0.003397.607 250,000 99.402
lmLD 0.003397.607 5Q,000 19.SS0
0.003397.607 25,000 9,9~10
0.003397.607 5,000 1.988
0.0041256.637 50,000 62.831
0.0041256.637 25,000 31.416
0.0041256.637 5,000 6.283
0.0053067.961 50,000 153.~98
0.0053067.961 25,000 76.6~99
0.0053067.961 5,000 15.339
0.0066361.725 50,000 31~ .086
0.0066361.725 25,000 159.043
0.0066361.725 5,000 31.8086
',,"7q,, ~
w ~ -
8 --
~IATTING RESISTANCE
_
Resistance to matting is a complex phenomenon due to
a combination of several factors, including the ability of
tlle fibers to recover on being deformed and their ability
to avoid becoming entangled with each other. I~rhen a fiber
is elongated beyond its yield point it will plastically
deform until it breaks. During matting the fiber is bent,
elongating or straining portions of tlle fiber. For good
matting resistance, one consideration is tilat the fiber
should not yield substantially when bent. In other words,
when the force causing the fiber to bcnd is released, the
fiber should spring back to its origlnal shape or very close
to it. The manner in which the bending force is applied
will affect the fiber's recovery. For example~ a fiber will
recover differently where a load is exer~ed only momentarily
compared to a load maintained for a long duration.
The elastic properties o my fiber and its large di-
ameter impart matting resistance to my fiber. Because my
fiber has a large diameter it will be strained much more
under normal matting conditions than conventional fibers.
~Iy experiments indicate that my fiber will be elongated or
strained up to about 25% o, its original length. ~lowever,
my fiber can be fabricated so that it will not in tension
permanently deform more than 10 percent, preferably no
more than 5 percent, at elongations up to about 25% at
strain rates in the range of from about 5 to about 50 min 1
Conventional fibers will be elongated or strained up to
about 10 percent in normal use. For my fiber to have a
9 ID 3982-O-US
matting resist~nce equivalent to conventional fiber its
permanent deformation at 25 pe~cent strain must be about
equ:ll to con~el1tional ~lber's ~-crm;ll1cl1t de'~-o~lll;ltiCIl ;It 1(1
percent strain. 1able II sets fortl1 d..ta ~ icl1 in~icates
this to be t]le case. Perrnanent deformatioll was determined
by AST~1 test metl1ocl Dl774-72 on monofilament fibers.
TABLE II
% Permlnent Deformation
Sample @ 25~ strain @ 10% strain
lmLD (0% gel) 6 . 55 .
lmLD (31~o gel) 4.40
lm~D (36% gcl) 3.80
lmLD (50% gel) l.50
Polypropylelle 2.95
Nylon l.95
~ Iy fibers also resist matting because tl1ey tend to
avoid becoming cntaTIglecl with eacl1 othcr. Ihis is due to
their large cliame~ers. The smaller the fiber cliameter an~1
the closer thc fibers are packed togctllcr tl1e greater the
frictional forces holcling the ~ibers together or in a matted
conclition. Since the carpets using my fibcr ~ill generally
have fewer fib:~rs per square inch Of carpet
backing th~ll conventional carpets anc1 tliesc arc lar~er
diameter filoers the frictional forces are substantially
-- lower than conventional carpets, al1cl tl1ereforc they tend
to resist mattillg.
. ., , ~ .
,/ .. 1 0
My fiber was used in pile carpet that was subjected
to a tetrapod walker test and comparecl Witll nylon carpet.
Table III sets forth the test results whicll indicate that
under such dynamic matting conditions rny fiber is equiva-
lent to nylon.
TET~APOD WALKER TEST RESULTS
TABLE_III
Total Pile l-leight (mils)
Cycles/0 6,345 20,130 85/530 164,000 444,820 687,620
SAMPLE
EVA(20~1rad) 466 468 460 440 431 396 406
Nylon 450 439 441 444 447 437 404
,
1-5 Carpets of my fiber and nylon fiber ~ere also sub-
jected to static loads. Carpet using my fiber did not
perform as well as nylon fiber, but it was satisfactory.
l~lear Resistance
To attain good wear, i.e., avoid loss of fiber from
the carpet, the fiber must be able to withstand pulling
and repeated rubbing. The material of my fiber is in-
herently weaker than the material used in conventional
fibers. Consequently, one would susl)ect that my fiber
would not be able to withstand wear. However, because my
fiber is substantially ~hicker than conventional fiber,
there is more material present. Because of this additional
material my -fiber wears as well as conventional fiber.
ll ID 3982-O-US~ ~
Specifically, carpets wear out mainly w]len fibers
are lost because they are broken by l)eillg pullecl or abraded.
~lally cliffelellt types of fotccs tcll(l to ~ 11 Lil~els Llolll
the backing. Thus in use the fibers are subjectecl to stress.
Stress (a) is the tensile force (F) acting on the fiber
divided by the cross-sectional area (~) of the fi~er:
E~
a
Since the forces actin~ on conve~tiolull nyloll Libels
and my fibers will under most circumstances be equal, if
the cross-sectional area of my fiber were equal to that of
conventional fiber my fiber would break or not wear as well as
nylon fiber. ~owever, this is not the case. ~Iy fiber,
since it has a substantially larger diameter tllan conven-
tional fiber, has a much larger area. Tllus, altl~ougll the
stress (a) that my fiber can witlls~clllcl to yiel~ or fracture
is lower than that of nylon, tlle larger area (A) of my fiber,
when multiplied by the stress (a), yields an equivalent
force (F) to deform or break the fiber.
In abrasive wear, rubbing action forces tiny clirt
particles to cut through fibers. Nylon, being a harcl
material, is not reaclily cut by tllese particles. In con-
trast, the material I use in my fiber is substantially
softer than nyloll. lhus, in abrasive wear, clirt particles
will cut througll my fiber ~ith less clifficulty. Because
more material is present, my fiber, however, will wear as
well as nylon fiber which is relatively thin.
12
Tuftability
For ~he fiber to be tufted or otherwise be llandled
durin~ processill~ it m~lst ha~re a certaill inel~sticit~ and
strength. If the fiber is too elastic it ~ill act li~e a
rubber bancl. Thus, instead of a tufting needle forcing the fiber
through the carpet backing~ the needle will simply stretch
the fiber. ~n release of the needle, the fiber ~ill spring
back into its original state and a tuft will not be formed.
I have found th~t if the elastic modulus exceeds 5,000 psi
my fiber ~ill be sufficiently inelastic ror tuftin~. rl~e
fiber also should have enough strength so that it .on't
break during tufting or ot]ler carpet making processes. I
llave found that if my fiber has an ultimate tensile strength
of at least 5,000 psi it will be suitable for most carpet
making processes. ~loreover, lubricant can be use~ to re- -
duce frictional forces leacling to bre.l~.lge.
PILE FABRIC
In accordance Wit]l my invention, a pile fabric is
made using the above described monofilament fiber. The
monofilament fiber is bulked by conventional textile pro-
cesses, for example, knit-deknitting or stuffer box llro-
cesses Approximately 15 to 50 such fibe-rs are t-isted
together an~l thell ~ul~ed to form a carpet yarn. ~lso, my
~25 fiber may be blended with conventional flbers, such as con-
tinuous nylon fiber. Preferably, there are from 0.5 to 2.0
t~ists per linear inch of yarn. Tl~is yarn has a cl~nier
ranging bet-~een 1,500 an~ ~,000.
13
,- .
. . . ~ ;
; :
:.
Althou~ll tlle yarll of my fiber is sul~stallti.~
ferent from -thc type of yarn normally used in carpet maXing
processes, it can be tufted througll conventional carpet
backings to form a pile fabric. In accordance l~ith this in-
S vention, such a pile fabric ~ill have for comparablc carpetconstructions substantially fe~er fibers per square inch of
bacXing thall conventional pile carpets made of nylon yarn.
lor ~ood cove-ra~e, the milli~UIII numbel of mollo:ril;llllcllt fibcrs
- l~ill be 4,000 per square inch of backing and the minimum pile
height l~ill be one-eight of an inch~ In contrast, the min-
irnu~n number of monofilament fibers used in con~elltional
nylon carpets is api~ro~imately 20,000 per sqllare i.llCh of
backlng.
Because there are fewer fibers in a square
inch of carpet backing for my yi:le fabric, tllis pile fabric
will feel sli~htly cooler to the touch than nylon pile fabrics.
The reasoll for tllis is that thcre are less dead air spaces,
and consequelltly, the fabric is a poorer insulator than con-
ventional carpets. Thus, wllen the hand touclles this carpet,
more heat from t]le han~ flo~s into this carpet than conven-
tional carpcts. Ilence thc cooler tOUC]I.
The pile fabric of my invention also has a slightly
smoother feel than conventional nylon pile fabrics. This
is maillly due to the reduced number of fibers in a square- - 25 ~--~inch of bac~ing. Because fewcr fibers arc present, tlle co-
eficient of friction of the pi]e fabric of my inventioll is
less than the coefficient o friction of convcntional nylon
pilc fabrics.
14
,~1~9,%1~
The lower coef~icient of friction and poorer insulating
properties of my fabric actually provide an advantage,
namely, reduction of carpet burns. Carpet burns are caused
by rapidly rubbing one's skin against the pile. Carpets
having a high coefficient of friction and good insulating
properties are more likely to produce a carpet burn. The
reason is that the higher coefficient of friction ~roduces
more heat which, due to the carpet's good insulating pro-
perties, is no-t conducted away from the skin.
METHOD OF MAKIN~ THE FIBER
In accordance with my meth.od of making the fiber, the
polymer material is extruded using conventional e~uipment
such as described in a paper presented by D. Poller and
O. L. Riedy, "Effect of Monofilament Die Characteristics
on Processability and Extrudate Quality," 20th Annual SPE
Conference, 1964, paper XXII-2. Thus, this invention
contemplates a method of making a fiber of polymeric material
having an elastic modulus of from 5,000 to fi0,000 psi, an
area moment of inertia of from 400 x 10 14 to 7,000 x 10 14
in4, and a stiffness parameter of from 1 x 10 5 to 1 x 10 8
lbs-in . The method comprises the sequential steps of extruding
the polymeric material through an orifice to form a molten
monofilament, drawing the molten monofilament while in the
li~uid state to reduce its diameter to the range of fron~ ~ to
2U mils, rapidly cooling the drawn, molten monofilament to form
a solid monofilament, and drawing the solid monofilament to
reduce its diameter to the range of from 3 to 6 mils. Then,
the drawn, solid monofilament is heated to a temperature above
100F but below its melting point while the monofilament is
under tension to prevent the diameter of the monofilament from
shrinking substantially.
The raE)id cooling can be achieved by feedincl the molten
- 15 -
.
monofilament into a water bath maintained at a temperature
in the range of from ambient to 150F.
Specifically, the polymeric material is drawn -through
an orifice having an area in the range of from about 8 x 10 5
to 70 x 10 5 in2. Preferably the temperature of the molten
polymer is below about 550F. This extrusion step forms a
molten monofilament which is drawn in the liquid state to
reduce its diameter to the range of from about 4 to about 20 mils,
preferably from about 7 to about 9 mils. This drawn monofilament
is than rapidly coolea to form a solid monofilament. Cooling
may be achieved by simply feeding the molten monofilament into
a water bath maintained at a temperature in the range of from
about ambient to about 150~F., as set out above. The monofilament
is
- 15a -
then drawn in the solid state to reduce its diameter to the
range of from about 3 to about 6 mils. This drawing stcp is
conducted at a temperature belbw about 100F, The drawn
solid monofilament is then subsequently heated to a temper-
ature above about 100F but below the melting point of thepolymeric material to heat set the fiber. This heating step
is conducted with the monofilament in tension to prevent the
diameter of the monofilament from shrinking substantially.
Heat setting is desirable in order to increase the shrink
resistance of the fiber. Preferably, the fiber is twisted
together prior to heat setting. Optionally, the fiber may
be heat set during the bulking process. For example~ in the
knit-denitting process the knitted sock would be held in
tension and heated.
To improve the heat resistance of the fiber, it is pre-
ferable to partially cross-link the molecules of the poly-
meric material. Most preferably this is achieved by irradi-
ating the fiber with an electron beam either as yarn or in
carpet form. The dosage of radiation should be sufficient
to cross-link to the molecules to the extent that they have
a gel content greater than 30% but less than 90%. The pre-
ferred gel content is 45-55%. Gel content of the ethylene-
vinyl acetate fiber is determined according to the following
procedure.
,. .. ..... . .
Fibers are wound around a metal wire screen and
subjected to solvent elution in hot xylene near
the boiling point for 24 hrs. Gel content is
then calculated using the formula:
Wf
% gel = - x 100
where lYo is the initial weight of the sample and
~Yf is the final weight after elution.
16 ID 3~2-O-USA
, . ,
In addition to irradiating the fi~er, cross-linking
may be achieved by t]ie a(ldition of peroxides to the poly-
meric material. For e~ample, a vinyl silane graftcd by a
pero~ide to the polyethylelle chain ser~es as a cross-link-
ing mech.lllisnl.
In accordance ~it]l my invention, the polyllleric materialmay be partially cross-linked prior to the dra~n solid mono-
filament being heat set. This ~ould permit the fiber to be
heat set at higher temperatures, and therefore, increase
its shrink resistance. Preferably, in the first cross-
linking step the polymeric material is cross-link~cl to thc
extent that the gel content is no greater than about 15%,
and in the second cross-lin~ing step the polymeric material
is partially cross-linked to the e~tent that the ~el con-
tent is no greatcr tllan 90%.
To en}lance cross-linking there are distributed through-
out the polymeric material fine particles of silicon dioxide
or titanium ciioxi~le. The particle si~c of t]lcsc o~i~les
ranges between lOO angstroms and 1 micron and tne amount used
ZO IS belo1~ 1 volume percent. lhis small amount of o~ide im-
proves the efficiency of the irradiation step. For e~ample,
a polymeric material irradiated at a dosage of 10 megarads
(MR) w~ill have a gel content of 25-2&%. lVhell tllis same
pol~ner includes 0.2 volume % silicon dio~ide and is ir-
- radiated at the sallie dosa~et the ~el contellt i.s 4~-45g.
This increase in gel content represents a substantial in-
crease in the melting point of thc polylneric material. Also
th~ a~ldition of poly-fllnctional monomels improves cross-
17
~ 2~L~ ~ ~
linking. For example, triallyl cyanurate or allyl acylate,alone or in combination with the oxides, are additives which
enhance the cross-linking yield for a given radiation dosage.
In general, due to the large fiber diameter, my fiber
can be loaded Wit}l fillers to higher levels than conventional
carpet fibers. Specifically, pigments may be used to color
my fiber. Such pigments may be dispersed throughout the
molten polymeric material prior to e~trusion. These pigments
will normally have a particle size in the range of from about
1 to about 25 microns. The amoun~ of pigment normally ranges
between about 1/2 and about 20% of the tbtal weight of the
blend.
According to my invention~ initially pellets of color
concentrate are prepared. These color concentrate pellets
are blended in the extruder with non-colored pellets. The
colored and non-colored pellets are then melted and mixed
together thoroughly. It is also possible to color my fiber
with a dispersed dye, but under some conditions this type
of dye tends to bleed out of the fiber. Cross-linking
subsequent to dyeing tends to fix this dye.
In addition to coloring agents, it is possible to in-
clude in the fiber flame retardants, antistatic agents, or
antisoiling agents. One flame retardant of particular
interest is hydrated magnesia. Hydrated magnesia will re-
lease its water rapidly at a temperature above about 500~.This permits the hydrated magnesia to be blended with the
molten ethylene-vinyl acetate copolymer ~ithout release of
its water, since this copolymer may be extruded at temper-
18 ID 3982-Q-USA
atures below 500F. Generally, because I use lower melting
point polymeric material in the fiber manufacture, additives
W]liC]I are sensitive to high temperaturcs, and therefore, can-
not be used in conventional nylon fiber, migllt be used in my
fiber, which comprises a lo~er melting point polymer.
Because of the large diameter of the fiber, the ex-
trusion and cooling equipment used in the manufacture of
the fiber are inexpensive. This savings in equipment cost
plus the use of low cost polymer result in a fiber which is
inexpensive relative to nylon. Tllis is the principal ad-
vantage of my fiber. Typical equipment for making my fiber
is shown in the drawings and described in the accompanying
description.
DESCRIPTION OF THE DRAWINGS
Figure 1 is a side elevational view of an extruder
and draw-line used in spinning the fiber of my invention.
Figure la is a front elevational vlew of the spinneret
plate.
Fibure lb is an enlarged fragmentary view of the ori-
fice$ in the spinneret plate.
Figure 2 is a conventional draw-winding apparatus for
drawing or stretching the fiber at temperatures below 100F.
Figure 3 is a side elevational vie~ of the apparatus
used to heat the fiber under tension.
Figure 4 is a graph showing the stress-strain curves
for various conventional fibers as well as the fiber of my
nvent lon .
ID 3982-O-USA
~ 2
DETAILED DESCRIPTION OF THE DRA~INGS
The fiber of my invention is made using a convention-
al extruder 10 which includes a hopper 12 into which pel-
lets of polymeric material are deposited, an extruder bar-
rel 14 where the pellets are melted, a static mixer 15, and
a spinneret pla~e 16 through which the molten polymeric
material is forced.
In accordance with my invention, the molten polymer
is drawn through orifices or holes having an area in range
of from 8 x 10-5 to 70 x 10-5 in2. Figure la shows the
spinneret plate 16 w]lich includes three rows 17a, 17b, and
17c of aligned holes. As shown in Figure lb, the holes
making up the central row 17b are offset at an angle of
about 60 with respect to the holes in top and bottom rows
17a and 17c. The spacings between the top row 17a and the
- center row 17b and the bottom row 17c and the center row
17b are each approximately 0.065 inch. The spacing between
adjacent holes in any one row lS approximately 0.075 inch.
The holes may be straight or tapered at an angle of approxi-
mately 15 to 30. Each hole has a diameter of 0.016 inch.
The melted polymeric ma~erial leaves the spinneret
plate 16 as a plurality of molten streams 18 of polymer
which continuously flows downwardly into a water bath 20.
When the molten polymer strikes the water in the bath 20,
it is chilled rapidly and becomes a continuous solid mono-
~ilament fiber ~1. This fiber passes around a pair of
guides 22 and 2~ and through a guide plate 26 into the nip
oE a pair of rollers 28 and 30. These rollers 28 and 30
ID 3982-O-US~
.,
5~ ~
pull on the fiber to draw the molten polymer streams 18
so that each stream has a diameter of about 6 to about 15
mils. On leaving the rollers 28 and 30 the solid monofila-
ments pass through a fiber guide/breaking system 32 and are
~rapped about spools 34 mounted on a winder 36.
When a spool 34a is loaded, lt is removed from the
winder 36 and placed on the draw winding apparatus 38 shown
in Figure 2. The lead ends of the fibers 21 on the spool
34a are unwound, guided about two drawing godets 40 and 42,
and ~rapped around a second spool 44. These godets 40 and
42 turn at different angular velocities so the fiber 21
coming off the spool 34a is stretched. This drawing or
stretching operation is conducted at temperatures below
100F. The fiber 21 is drawn so that it has a diameter in ---`
the range of from 3 to 6 mils.
As shown in Figure 3, the fiber 21 from the second
spool 44 is then pulled through a heater 46 and heated to
a temperature above 100F but below the melting point of
the fiber 21. When copolymers of ethylene and vinyl acetate
are employed to make the fiber 21, the preferred temperature
of the heater is in the range from about 150 to about 200F.
The fiber 21 from the spool 44 first passes through a pair
of draw rolls 48 and 50 ~hich pull the fiber over a pre-
- heater 52 and feed the fiber into the nip of an input feed
roll assembly 54. The fiber passes through the heater 46
and over a feed roll 56 to the takeup spool 58. The tension
on the fiber 21 as it passes through the heater 46 is suf-
ficient to prevent the fiber from shrinking. The fiber 21,
ID 3982-O-USA
21
2~
ho~ever, is not stretched so its diameter rcmains in the
range of from 3 to 6 mils.
STRESS-STRAIN CURVES
Figure 4 contrasts the stress-strain curves of the
fiber of my invention with that of conventional carpet
fibers. Stress and strain or elongation were measured ac-
cording to ASTM standard method ~lo. D2256-69. The Curve A
represents my fiber. In contrast to my fiber J the conven-
tional fibers have higher ultimate tensile strengths ~nd
will elongate substantially less at higher stress levels.
The toughness or wearability of the fibers correlates to
the area under the stress-strain curves. Note the area
under Curve A is about the same as the area under the stress-
strain curves of the conventional fibers. I`he fiber of the
stress-strain Curve A was made according to Example 1.
Examples of alternate fibers are also provided.
EXA~IPLES OF FIBERS
Example 1
~ Some ethylene-vinyl acetate fibers were produced in
; the form of bulked continuous filament yarn which contained
40 filaments. No coloring agent or additives were added
during extrusion. T}le polymer pellets were commercially ob-
tained from U.S. Industries, Inc., under the designation
NA294, a 5% vinyl acetate, ethylene-vinyl acetate copolymer,
having a melt index of 2Ø The copolymer was extruded on
a 3/4 inch single screw extruder through a 40 hole spinneret.
22 ID 39~2-O-USA
The spinneret had 0.013" diameter holes having a 30 taper.
- The extruded fibers were drawn in the liquid phase to a
diameter o 0.0073 inch and solidified in a parallel row
on a chill roll. The temperature profile in the extrudeT
increased from 340F at the hopper zone to 480F at the
exit zone. The extruder screw speed was 15 rpm and the
screw was driven at 6.0 amps. The line speed on the take
up was 28 feet per minute. The yarn was then draw/textured
on a Pinlon machine. In order to-do this, the yarn was
.
treated with a silicone finish and then drawn and textured.
The draw ratio was 3:1, with the final filament diameter -~--
being 0.0041 - 0.0043 inch ~69-76 denier). Tlie yarn was
then cross-linked on a 3 MeV electron beam machine at a
dosage of 10 Mrad. (Gel content by elution in xylene = 28%). -
~15 The mechanical properties of this fiber were as follows:
diameter of 0.0041 in. ~69 denier), 10% offset yield stress
of 8780 psi (0.74 gpd), ultimate tensile strength of 13,200
psi (1.13 gpd), elastic modulus of 35,70Q psi, and elongation
to fracture of 85%.
20 ~ Example 2
The ethylene vinyl acetate copolymer (5% vinyl acetate)
described in Example 1 was spun into yarn composed of 20
continuous filaments. Twelve yarn ends were spun from a
single spinneret. This ~rial was conducted on a commercial
~mono~ilament production line in which extrusion and drawing
were done in-line. The yarn was spun on a 1.5 inch, single
screw extruder. The hopper of the extruder was filled with
NA294 ethylene vinyl acetate pellets (U.S.I. Chemicals) and
ID 3982-O-USA
23
_ _ , , . , _ . _ _ _ . _ . _ _ . ~ .. . . . . . .... . . . . . .
!~ ' ~,
a prepared color concentrate. The pellet to concentrate
weight ratio was lO:l. The color concentrate pellets con-
tained 5 ~eight percent o~ light green pigment (Harwick).
Fibers were spun through a commercial monofilament die at
5 a ~hroughput of 31 lb/hr and guenched in a water bath which
contained some surface finish agent in emulsion form. The
extruder screw was operating at lO0 rpm, and the gear pump
was operating at 30 rpm. A Fluid Dynamics~ filter (X13)
was installed between the gear pump and the spinneret. A
; 10 pressure transducer, mounted before the filter, recorded a
pressure of 1600-1800 psi throughout the run. The tempera- -~
ture profile in the extruder was as follows: Zone 1 = 380F,
Zone 2 = 440F, Exit = 440F, Spinneret = 440F. The yarns
were drawn in a par~llel array in a single stage between
15 godet rolls to a 3.3:1 ratio. The feed rolls rotated at
23.7 m/min, and the take up rolls rotated at 78.3 m/min. ~ -
The final yarn denier was 2650 ~approximately 132 den/fil).
The yarn (not individual fibers) was tested for mechanical
properties. The yarn had a tensile strength of 0.87 g/den
Z0 ~10,200 psi), an elastic modulus of 3.4 g/den ~27,200 psi),
and an elongation to fracture of I13%-. This yarn was bulked
differently than that of Example 1. The yarn was twisted
0.75 turns per inch, then knit on a commercial machine into
a long tube. This tube was subjected to electron beam ir-
25 radiation to a dosage of 10 Mrad and deknit. The deknit
yarn had a substantial crimp and was subsequently tufted
into carpet. The gel content measured on the yarn was 28%.
24 ID 3982-O-USA
r
Example 3
Fiber was made from ethylene-vinyl acetate copolymer
(USI designation NA294 - 5% vinyl acetate and 95% low
density polyethylene, ~I=2) in identical fasllion to that
made in Example 1, except the additives listed in Table 4
~ere added during extrusion. This fiber was then exposed
to electron beam irradiation. The following gel yields
were obtained on drawn fiber (3:1 draw ratio) after 48
hours extraction in hot xylene:
~ 10 -,
TABLE IV
, ., , ,_ _ ,
Electron
Additive Beam DosageGel Content
(wt. %) (Mrad) %
,___ _ .. ,.~ . .,,., ,,,,.. ,_
None 10 28
SiO2(0.48) 10 44.1
Ti02(1.8) 10 48.7
TAC (1.0) 10 45.5
,
The higher gel levels improve certain carpet properties
such as resilience and shrinkage resistance. At these gel
concentrations, the mechanical properties are not substan-
- tially different than those presented in Example 1.
Example 4
An EVA copolymer, containing 9% vinyl acetate and
having a melt index of 3.0, l~as made into the new type of
yarn. The fibers were colored by incorporating pigment at
ID 3~82-O-USA
a level of 0.5% in the melt. Extrusion ~as done on a one-
inch, single screw e~trucler, using a screen pack (mesh sizes
of 40-60^60-40) and a 40 hole spinneret with a hole diameter
of 0.015 inch. The temperature profile in the extruder in-
creased from the hopper zone to the exit zone from 340 to500F at the die. The screw speèd on the extruder was 20 rpm
and the screw was driven at 7.0 amps. The line speed on the
take up was 38 fpm. Under these conditions, the fiber dia-
meter was 0.009 inch. Tlle yarn was then draw/textured on
a Pinlon machine. To do this the yarn was treated with a
silicone finish and then drawn and textured. The draw ratio
was set at 4:1, with the final filament diameter being 0.005
inch (100 denier). The yarn was cross-linked on a 3 MeV
electron beam machlne at a dosage of 10 Mrad. The mechanical
properties of the ne~ fibers are as follows: Diameter = 0.005 in.
~100 denier), 10% offset yield stress = 7710 psi, ultimate ten-
sile strength = 10,300 psi, elastic modulus = 39,300 psi, elon-
gation to fracture = 79.4%.
.
26 - ID 3982-O-USA
.
