Colored bicomponent filaments have a particulate colorant dispersed throughout one of the fiber domains while another of the fiber domains is colorant-free. More specifically, the filaments have at least two distinct components arranged longitudinally coextensive with one another. The arrangement of the components may be a sheath/core structure or a side-by-side structure. One of the components contains a colorant and the other one does not (i.e., is colorant free). The colorant-free component is most preferably formed of a polymeric material which is incompatible with the particulate colorant, whereas the colorant-containing component is most preferably formed of a polymeric material which is compatible with the particulate colorant.

FIELD OF THE INVENTION 
The present invention relates generally to the field of bicomponent 
synthetic polymer fibers. More particularly, the present invention relates 
to colorant-containing bicomponent fibers. 
BACKGROUND AND SUMMARY OF THE INVENTION 
As used herein the term" bicomponent fiber" means a fiber having at least 
two distinct, and possibly more, components or domains in intimate 
adherence along their length. These components are distinct due to the 
polymer used and/or due to the additives present. The term "filament" 
means a fibrous strand of indefinite length. The term "staple" means a 
fibrous strand of short length. The term "fiber" means filaments, staple, 
or both. The colored bicomponent fibers of the present invention have 
Munsell Values between about 2.5/ to about 8.5 and Munsell Chromas greater 
than about/0.5. (Kelly et al, The ISCC-NBS Method of Designating Colors 
and a Dictionary of Color Names, National Bureau of Standards Circular 
553, pages 1-5 and 16 (1955), incorporated hereinto by reference.) The 
term "colorant" means a solid particulate pigment which may be 
incorporated into a spinnable polymer to obtain colored filaments. 
The incorporation of additives in so-called "neat" thermoplastic polymeric 
host materials (that is, polymeric materials containing no additives) so 
as to achieve desired physical properties is well known. Thus, the art has 
conventionally incorporated colorants, stabilizers, delusterants, flame 
retardants, fillers, antimicrobial agents, antistatic agents, optical 
brighteners, extenders, processing aids and other functional additives 
into polymeric host materials in an effort to "engineer" desired 
properties of the resulting additive-containing polymeric host material. 
Such additives are typically added any time prior to shaping of the 
polymeric material, for example, by spinning or molding (e.g., extrusion, 
injection, or blow-molding) operations. 
The incorporation of colorant additives in filaments formed by 
melt-spinning a polymeric material has presented unique challenges. For 
example, the amount of particulate pigment dispersed in a concentrate 
which is added to the polymeric material must be sufficiently high to 
impart satisfactory color density, but must not be so high as to interrupt 
the spinning process. One prior proposal for incorporating colorant 
additives in thermoplastic polymeric materials is disclosed in U.S. Pat. 
No. 5,236,645 to Frank R. Jones on Aug. 17, 1993 (the entire content of 
which is expressly incorporated hereinto by reference). 
According to the Jones '645 patent, additives are introduced into a 
thermoplastic melt by feeding at least one additive in an aqueous vehicle 
containing a dispersant to form an aqueous additive stream to a vented 
extruder which is extruding a thermoplastic. The aqueous portion of the 
aqueous additive stream is thereby volatilized within the extruder and is 
removed therefrom via an extruder vent. As a result, a substantially 
homogeneous system containing the thermoplastic, dispersant and the 
additive is obtained which may thereafter be spun into a filament by 
melt-extrusion through filament-forming orifices in a spinneret associated 
with a spin pack assembly. 
Some colorants are known to be unsuitable for use with certain polymeric 
systems--for example, due to degradation of the colorants at the 
processing temperatures of the polymeric systems, the degradation of the 
colorants due to the chemical environment of the resin (e.g., reductive 
nature of many polymeric melts) or the abrasiveness of the colorant per se 
or a combination of these three phenomena. Thus, it would be highly 
desirable if synthetic polymeric fibers could be provided which are 
colored by the incorporation of colorants which, until now, have not been 
considered potential colorant candidates for such purpose. It is towards 
fulfilling such a need that the present invention is directed. 
Broadly, the present invention provides colored bicomponent filaments 
wherein the colorant is dispersed throughout one of the fiber domains 
while another of the fiber domains is colorant-free. The 
colorant-containing component will most preferably occupy between about 10 
to about 90% of the fiber cross-section, while the colorant-free domain 
will occupy between about 90 to about 10% of the fiber cross-section. The 
colorant-free domain will cover at least about 50% of the fiber's outer 
surface, and most preferably will cover the entirety of the fiber's outer 
surface so that it encapsulates or surrounds entirely the 
colorant-containing domain.

DETAILED DESCRIPTION OF THE INVENTION 
To promote an understanding of the principles of the present invention, 
descriptions of specific embodiments of the invention follow and specific 
language describes the same. It will nevertheless be understood that no 
limitation of the scope of the invention is thereby intended, and that 
such alternations and further modifications, and such further applications 
of the principles of the invention as discussed are contemplated as would 
normally occur to one ordinarily skilled in the art to which the invention 
pertains. 
The present invention provides colored bicomponent filaments wherein the 
colorant is dispersed throughout one of the fiber domains while another of 
the fiber domains is colorant-free. More specifically, the present 
invention provides a filament having a least two distinct components 
arranged longitudinally coextensive with one another. The arrangement of 
the components may be a sheath/core structure or a side-by-side structure. 
One of the components contains a colorant and the other one does not 
(i.e., is colorant free). 
Regardless of whether the components are arranged sheath/core or 
side-by-side, the colorant-free component should occupy at least 50% of 
the external surface of the fiber. More preferably, the colorant-free 
component will occupy more than 50% of the external surface of the fiber 
so that the colorant-containing component is at least partially 
encapsulated thereby. Most preferably, the colorant-free component 
entirely encapsulates the colorant-containing component (i.e., the 
colorant-free component occupies 100% of the external surface of the 
fiber) so that the fiber is a sheath/core structure--namely, having the 
colorant-containing component as the core which is surrounded entirely by 
a colorant-free sheath. The core may be centered (concentric) or offset 
(acentric). Furthermore, the fiber cross-section may be round or may be 
non-round, for example, a trilobal cross-sectional configuration. 
Virtually any melt-spinnable polymer may be employed in the practice of the 
present invention. Classes of suitable polymeric materials include 
polyamides, polyesters, acrylics, olefins, maleic anhydride grafted 
olefins, and acrylonitriles. More specifically, nylon (especially nylon-6 
or nylon 6,6), polyolefins (such as polypropylene, polyethylene and the 
like) and polyesters are especially preferred. 
The distinct fiber components may be formed of the same class of polymeric 
material or may be formed of different classes of polymeric materials. In 
any event, as noted previously, one of the components will contain a 
colorant, while the other component will be colorant-free. In a 
particularly preferred embodiment, the fibers of this invention are 
symmetrical sheath/core structures whereby the colorant-free sheath is 
formed of a nylon (e.g., nylon-6) and the colorant-containing core is 
formed of polypropylene. 
The colorants employed in the present invention may be virtually any solid 
particulate colorant. The colorant will most preferably be insoluble in 
the colorant-containing polymeric material at its processing conditions 
(but dispersible therein) and compatible therewith (e.g., no subject to 
degradation at processing conditions of the colorant-containing polymeric 
material). Moreover, the colorant is most preferably one which is 
incompatible with the polymeric material forming the fiber's colorant-free 
domain--e.g., in terms of adverse reactions occurring between the 
polymeric material of the colorant-free domain and the colorant and/or 
colorant degradation at the polymeric material's processing conditions 
(e.g., temperatures). Thus, according to the present invention, such 
particulate colorants may be dispersed in a compatible polymeric material 
(e.g., polypropylene) and formed into a core component of a bicomponent 
fiber which is surrounded by a sheath component formed of a polymeric 
material (e.g., nylon) which is incompatible with the colorant. Most 
preferably, the colorants are particulate organic pigments. 
Some advantages, however, also ensue from incorporating a colorant in an 
incompatible polymeric material and then providing such a mixture as a 
core of a sheath/core bicomponent fiber. That is, even though some adverse 
chemical reactions and/or colorant degradation may be experienced, by 
surrounding the colorant-incompatible polymeric material with a sheath 
component, such reactions and/or colorant degradations are significantly 
minimized. 
Thus, for example, the fibers of the present invention exhibit improved UV 
light resistance and bleachfastness. As used herein, and in the 
accompanying claims, the terms "UV light resistance" and "bleachfastness" 
are meant to refer to a bicomponent filament having a colorant-containing 
and colorant-free domains which, in the case of UV light resistance after 
1275 kilojoules of UV light exposure, and in the case of bleachfastness 
after exposure to the bleachfastness test to be described in greater 
detail below, respectively have a CIE La*b* total color difference 
relative to unexposed filaments at least 50% as compared to the total 
color difference when subjected to the same conditions of a monocomponent 
filament which consists only of a polymeric material which is the same as 
the polymeric material forming the colorant-free domain of the bicomponent 
filament, but having the same overall colorant loading homogeneously 
dispersed therein as the colorant-containing domain of the bicomponent 
filament. 
The bleachfastness test that is employed according to the present invention 
refers to the testing of knitted flat jersey fabrics which are cut into a 
4".times.4" square. The fabric is then completely immersed in a 100 ml. 
solution of 5.25% sodium hypochloride in water. After the fabric is 
completely wetted out, excess solution is blotted off and the fabric is 
hanged for 24 hours at 70.degree. F. and 65% relative humidity. The fabric 
is then rinsed in a mild detergent, rinsed with water and dried for an 
additional 24 hours. Color changes are then measured using a 
spectrophotometer under D5000 daylight illumination. Total color 
difference is recorded using the CIE La*b* system relative to the 
unbleached fabric. 
The particulate colorants are incorporated into the colorant-containing 
polymeric component in any amount required to achieve the desired filament 
coloration. Preferably, however, the colorant will be present in the 
colorant-containing component in an amount of at least about 0.005 wt. %, 
and more preferably between about 0.05 wt. % to about 0.10 wt. %. The 
amount of the colorant present will depend in large part upon the 
particular colorant that is selected and the particular color of the 
filament that may be desired. 
The particulate colorants must, of course, be spinnable with the polymeric 
materials in which they are incorporated. That is, the colorants must not 
be so large in size that they clog or block the spin plate orifices 
(thereby causing spinning breaks). Thus, for most applications, the 
particulate colorants will have a mean particle size of less than about 10 
.mu.m, preferably less than about 5 pLm, and will typically be between 
about 0.1 .mu.m to about 2 .mu.m. 
The ratio C.sub.c :C.sub.f of the colorant-containing component to the 
colorant-free component, respectively, can vary within wide ranges. For 
example, the ratio C.sub.c :C.sub.f is preferably less than about 90:10 
and typically about 70:30. 
The filaments of this invention may be usefully employed in a number of 
end-use applications. For example, the filaments of this invention may be 
formed into textile fabrics (e.g., apparel fabrics, household fabrics and 
the like) according to techniques well known in this art. Furthermore, the 
filaments may be formed into carpet yarns, in which case a trilobal 
sheath/core structure is particularly preferred. More specifically, fibers 
for the purpose of carpet manufacturing have linear densities in the range 
of about 3 to about 75 denier per filament (dpf) (denier=weight in grams 
of a single fiber with a length of 9000 meters), and typically between 
about 15-25 dpf. 
The invention will be further illustrated by way of the following Examples 
which disclose specific embodiments of this invention, but which are 
non-limiting with respect thereto. 
EXAMPLES 
The present invention will be further illustrated and understood from the 
following non-limiting Examples. 
Example 1 
40 grams of 25% by weight concentrate of Red 194 (Rhodafin Red RRN-AE 30 
from Hoechst-Celanese Corporation of Charlotte, N.C.) in polyethylene was 
combined with 1960 grams of polypropylene. This mixture was placed in the 
extruder that supplies the core of the fibers. Temperatures in the core 
extruder zones were 165.degree. C., 180.degree. C., 200.degree. C., 
220.degree. C. and 240.degree. C. The polymer line between the extruder 
and the polymer metering gear pump was heated to 240.degree. C. Nylon 6 
(2.7 relative viscosity, bright, BS-700F from BASF Corporation, of Mt. 
Olive, N.J.) was placed in the sheath extruder. Temperatures in the sheath 
extruder zones were 245.degree. C., 265.degree. C., 270.degree. C., and 
275.degree. C. The polymer line between the extruder and the polymer 
metering gear pump was heated to 275.degree. C. as was the spin beam that 
held the metering pumps and the spin pack. The speed of the polymer 
metering gear pumps was adjusted such that about 20% of the core mixture 
was delivered to the core of each filament and the remaining 80% was the 
nylon 6 sheath. The sheath and core polymers were directed through a 56 
filament spin pack similar to that described in U.S. Pat. No. 5,344,297 to 
Hills so as to produce a fiber cross section similar to that illustrated 
in FIG. 16 therein (i.e., a sheath-core trilobal fiber). The 56 filament 
yarn subsequently had a lubricating oil applied, and was thereafter 
processed through three pairs of heated, driven rolls. The first pair of 
rolls was operated at 80.degree. C. and 500 meters per minute. . The 
second pair or rolls was operated at 130.degree. C. and 510 meters per 
minute. . The final pair of rolls was operated at 140.degree. C. and 1597 
meters per minute. The yarn was then taken up on a tension controlled 
winder. In a subsequent step, the yarn was heated and textured (or 
"bulked"). 
No difficulties were seen in spinning the yarn. As extruded, the yarn had a 
clear red appearance. 
Example 2 
The conditions of Example 1 were repeated except the core component was 
nylon 6 (BS-700F) instead of polypropylene. Also, the core extruder 
temperatures were 245.degree. C., 255.degree. C., 265.degree. C., 
270.degree. C., and 275.degree. C.; and the polymer line was heated to 
275.degree. C. 
No difficulties were seen in spinning the yarn. As extruded the yarn had a 
slight blue overtone to the red color which became a purer red as the yarn 
sat overnight. 
Example 3 (Comparative) 
Example 2 was repeated except the nylon 6 in the core extruder contained no 
colorant and the sheath extruder used a mixture of 40 grams of the 25% 
concentrate of Red 194 (i.e., as described in Example 1) in 7,960 grams of 
nylon 6. The resulting yarn contained 0.1 wt. % of the colorant per linear 
length of the yarn. 
No difficulties were seen in spinning the yarn. As extruded, the yarn had a 
slight blue overtone to the red color which became a purer red as the yarn 
sat overnight. Color seemed darker and a little browner when later 
examined. 
Example 4 (Comparative) 
Example 2 was repeated except the mixtures used in both the core and sheath 
extruders was 40 grams of the 25% concentrate of Red 194 (i.e., as 
described in Example 1) in 9,960 grams of nylon 6. The resulting yarn 
contained 0.1 wt. % of the colorant per linear length of the yarn. 
No difficulties were seen in spinning the yarn. As extruded, the yarn had a 
slight blue overtone to the red color which became a purer red as the yarn 
sat overnight. Color seemed darker and a little browner when later 
examined. Overall appearance of this yarn was very similar to that in 
Example 3. 
Example 5 
Example 1 was repeated except the core mixture was 4 grams of the Red 194 
concentrate in 1996 grams of polypropylene. 
Example 6 
Example 2 was repeated except the core mixture was 4 grams of the Red 194 
concentrate in 1996 grams of nylon 6. 
Example 7 (Comparative) 
Example 3 was repeated except the sheath mixture was 4 grams of the Red 194 
concentrate in 7,996 grams of nylon 6. 
Example 8 (Comparative) 
Example 4 was repeated except the mixture for both extruders was 4 grams of 
the Red 194 concentrate in 9,996 grams of nylon 6. 
Example 9 
Example 1 was repeated except the core mixture was 200 grams of the Red 194 
concentrate in 1800 grams of polypropylene. 
Example 10 
Example 2 was repeated except the core mixture was 200 grams of the Red 194 
concentrate in 1800 grams of nylon 6. 
Example 11 (Comparative) 
Example 3 was repeated except the sheath mixture was 200 grams of the Red 
194 concentrate in 7,800 grams of nylon 6. 
Example 12 (Comparative) 
Example 4 was repeated except the mixture for both the core and sheath 
extruders was 200 grams of the Red 194 concentrate in 9,800 grams of nylon 
6. 
The yarns from Examples 1-12 above were knitted into single jersey circular 
knit fabrics. These fabrics were mounted on cards and accelerated 
weathering was performed as suggested in AATCC procedure 16--1987 (option 
E). The tensile properties of the unexposed and weathered yarns were 
determined using the procedure given by ASTM D 2256. The resulting data 
appears in Table 1 below. 
TABLE 1 
__________________________________________________________________________ 
Effect of accelerated weathering on tensile properties 
Tenacity (grams force per denier) 
Breaking Elongation (percent extension) 
Weathering 
unexposed 
425 
850 
1275 
2125 unexposed 
425 KJ 
850 KJ 
1275 Kj 
2125 KJ 
__________________________________________________________________________ 
Example 1 
2.36 1.73 
1.64 
1.05 
0.34 43.6 43.1 
36.3 
22.1 
8.8 
Example 2 
2.18 1.72 
1.35 
0.80 
0.02 44.1 48.7 
29.6 
16.7 
3.3 
Example 3 
2.52 1.29 
1.14 
0.42 
0.04 52.5 28.9 
22.4 
10.6 
4.4 
Example 4 
2.63 1.39 
1.23 
0.83 
0.07 43.7 29.8 
24.8 
16.2 
5.3 
Example 5 
2.73 1.42 
1.10 
0.41 
untestable 
57.0 34.3 
23.8 
9.7 
untestable 
Example 6 
2.08 1.44 
1.27 
0.41 
untestable 
43.0 36.9 
30.5 
10.5 
untestable 
Example 7 
2.41 1.61 
1.13 
0.22 
untestable 
54.2 36.7 
22.9 
7.5 
untestable 
Example 8 
2.40 1.76 
1.47 
0.67 
untestable 
47.9 35.0 
24.7 
13.6 
untestable 
Example 9 
2.44 1.83 
1.67 
1.30 
0.60 39.4 55.6 
43.8 
30.8 
14.1 
Example 10 
2.28 1.74 
1.42 
0.85 
0.15 52.4 53.4 
42.7 
18.8 
7.4 
Example 11 
2.27 1.05 
1.00 
0.50 
0.11 48.0 21.7 
20.1 
10.6 
7.0 
Example 12 
2.53 1.11 
0.95 
0.65 
0.28 49.1 24.1 
18.6 
13.9 
8.8 
__________________________________________________________________________ 
"untestable" means that the yarn had degraded so badly that it could not 
be mounted in tensile testing equipment. 
A spectrophotometric measurement of the exposed and unexposed materials was 
made and the total color difference between the exposed and unexposed 
materials was calculated under the CIE L*a*b* system. (For details of 
these calculations see, for example, Billmeyer, Principles of Color 
Technology, 2.sup.nd edition (1981), expressly incorporated hereinto by 
reference.) Color measurement is calculated for D5000 daylight 
illumination. The lower the value of the total color difference (.DELTA.E) 
the less the color of the material has changed for a typical observer. The 
values of the total color difference for the four degrees of weathering 
are given in Table 2. 
TABLE 2 
______________________________________ 
Total Color Difference After Accelerated Weathering 
Color Change of Fabric Relative to Unexposed Fabric 
425 KJ 
850 KJ 1275 KJ 2125 KJ 
______________________________________ 
Example 1 2.05 2.41 1.91 3.19 
Example 2 18.42 19.65 19.55 19.76 
Example 3 34.75 44.41 45.61 49.88 
Example 4 34.58 43.41 44.84 48.67 
Example 5 13.75 13.8 7.18 6.21 
Example 6 10.85 11.49 9.98 9.01 
Example 7 26.47 28.15 22.8 22.21 
Example 8 27.72 29.07 21.52 20.8 
Example 9 0.6 1.1 1.58 2.92 
Example 10 4.96 2.79 4.83 4.16 
Example 11 5.95 7.02 8.6 9.56 
Example 12 3.46 3.88 5.14 5.8 
______________________________________ 
Two different effects are believed to be seen in this data. The first 
effect seen is the loss of the colorant as the weatherometer exposure 
degrades the colorant. The second effect that is seen is the "browning" of 
the fibers (especially Examples 3, 4, 7, 8, 11, and 12) due to a 
degradation mechanism while the pigment was at high temperature and 
exposed to air as the fibers left the spin pack and is revealed with a 
loss of the red colorant. 
Accompanying FIGS. 1 and 2 are graphs of the reflectance values of the 
fabrics made from Examples 1-4, and 9-12, respectively. The curves are 
created from measurements performed at every 20 nm of the visible spectrum 
from 400 to 700 nm. The different characteristics of the appearance of the 
pigment to the polymer matrix and position in the fiber can be seen. 
Example 13 
200 grams of a bleach sensitive yellow pigment concentrate (C.l. Pigment 
Yellow 150) was mixed with 4600 grams of polystyrene (PS 2820 from BASF 
Corporation, Mount Olive N.J.). That mixture is extruded into the 25% by 
weight core of a trilobal carpet yarn (58 filaments 1300 denier). 
Extrusion temperatures for the core extruders are 170.degree. C., 
185.degree. C., 223.degree. C., and 245.degree. C. Polymer lines and the 
spin beam are all maintained at 270.degree. C. Sheath polymer is uncolored 
nylon 6 (BS-700F from BASF Corp. of Mount Olive, N.J.). The sheath 
extruder temperatures are 240.degree. C., 250.degree. C., 260.degree. C., 
265.degree. C., and 270.degree. C. 
Example 14 
200 grams of a bleach sensitive yellow pigment concentrate, C-005, is mixed 
with 19,000 grams of nylon 6 (BS-700F from BASF Corporation of Mount Olive 
N.J.). That mixture is extruded into a 58 filament 1300 denier trilobal 
carpet yarn. The extruder temperatures are 240.degree. C., 250.degree. C., 
260.degree. C., 265.degree. C., and 270.degree. C. All polymer lines are 
maintained at 270.degree. C. 
When the yarns form Examples 13 & 14 knitted into single knit jersey 
fabrics and exposed to bleach Example 13 has no significant color change. 
The fabric from Example 14 turns from a bright yellow to a very dull 
appearing gray color. 
While the invention has been described in connection with what is presently 
considered to be the most practical and preferred embodiment, it is to be 
understood that the invention is not to be limited to the disclosed 
embodiment, but on the contrary, is intended to cover various 
modifications and equivalent arrangements included within the spirit and 
scope of the appended claims.