Cohesive bulky carpet yarn of a polyamide continuous multifilament and a cut pile carpet

A pile yarn for a carpet and a cut pile carpet. A bulky yarn of a polyamide multifilament is fed to a false twisting and heat setting device where filaments in the yarn are thermally and partially adhered to each other while the yarn is false twisted. A bulky cohesive continuous multifilament yarn thus obtained has alternate twists therein along the lengthwise direction thereof and a latent torque therein, and after it is tufted on a substrate of a carpet as a pile yarn and after the piles are cut, the carpet is heat treated, preferably by means of saturated or superheated steam. The torque in the cut piles is developed to create true twists.

BRIEF DESCRIPTION OF THE INVENTION 
The present invention relates to a pile yarn for a carpet and a novel cut 
pile carpet. More specifically, the present invention relates to a 
cohesive bulky carpet yarn of a polyamide continuous multifilament which 
is preferable for use as a pile yarn in a cut pile carpet and a method for 
industrially manufacturing the same, and a cut pile carpet wherein the 
pile yarn is tufted and a process for manufacturing the same. 
BACKGROUND OF THE INVENTION 
Recently a bulky polyamide continuous multifilament yarn has been utilized 
in a tufted carpet, especially a cut pile carpet. In this case, when the 
bulky polyamide continuous multifilament yarn is used in a shaggy and 
saxong carpet, the bulky multifilament yarn which is obtained after a 
multifilament yarn receives a turbulent jet of heated fluid or a stuffing 
operation of fluid, generally receives additional twists between 30 T/m 
and 250 T/m, and then it is heat set by means of saturated steam, dry heat 
or the like so that the twists therein are set. Thereafter, the bulky yarn 
is utilized in a carpet as a pile yarn. 
Such a bulky yarn obtained after twisting and heat setting has both 
preferable bulkiness adjusted by heat setting and suitable coherency 
caused by twisting. As a result, when the yarn is utilized in a cut pile 
carpet, the filaments of each cut pile gather together to form a slender 
shape like a pencil (this will be called a pin-point effect hereinafter), 
and the carpet has good quality. However, the cohesive bulky yarn obtained 
after twisting and heat setting has some problems. One of the problems is 
that the manufacturing cost of the yarn is high because the yarn requires 
two additional separate operations, i.e., twisting and heat setting. 
Another problem is that the yarn loses the above-mentioned pin-point 
effect and the hand and appearance thereof becomes felt like after the cut 
pile carpet with pile yarns of the above-mentioned bulky yarn is utilized 
for a long duration because its coherency lowers gradually. 
To eliminate the above-mentioned problems, methods have been attempted 
wherein the twisting and heat setting operations of the bulky yarn for 
carpet pile yarn are omitted and another method is carried out to impart 
coherency to the yarn. For example, in U.S. Pat. No. 3,611,698, a bulky 
yarn is entangled by means of a fluid flow so that a high degree of 
interlace is imparted therein. In U.S. Pat. No. 3,968,638, a bulky yarn is 
also false twisted by means of a fluid jet after it is interlaced so that 
latent twists are imparted therein. However, due to these methods, it is 
difficult to impart to a bulky polyamide multifilament yarn having a thick 
denier, a uniform coherency along a lengthwise direction of the yarn by 
means of interlacing. In addition, highly entangling portions have an 
excessive coherency, and non-uniformity of dyeability or dyeing specks may 
occur. As a result, there is an additional problem in that the quality of 
a carpet is substantially degraded. 
In accordance with the method disclosed in another U.S. Pat. No. 3,971,200, 
the pile yarn is maintained in a non-twisted situation. As a result, the 
yarn may split and filaments composing the yarn may be slack. Since the 
whole yarn does not have sufficient coherency, the operabilities, 
especially tufting operabiity, of the yarn are low. 
The yarn disclosed in the above-mentioned U.S. Pat. No. 3,968,638 is not 
wholly as cohered as a true twisted yarn, and opened and entangled 
portions are alternately distributed along the yarn. In the opened 
portions of the yarn, splitting of the yarn and slacking may occur, and 
problems occur in that the yarn becomes entangled with machine parts or 
another yarn and the yarn is split by means of tufting needles while the 
yarn is being tufted. 
SUMMARY OF THE INVENTION 
The inventors of the present invention have studied various bulky cohesive 
polyamide multifilament yarns which can be utilized in a cut pile carpet 
as a pile yarn so that a bulky yarn can be provided which does not have 
any of the above-mentioned problems and which can form a cut pile carpet 
with a high quality. The inventors have accomplished the present invention 
after they found that a novel bulky polyamide multifilament yarn which is 
distinguished from the known bulky yarns can be obtained when a false 
twisting and thermal and partial adhering operation is introduced, which 
has never before been carried out in this field. 
More specifically, a cohesive bulky carpet yarn of a polyamide continuous 
multifilament according to the present invention is characterized in that 
the total crimp of the yarn is between 3% and 15%, that filaments 
composing the yarn are partially and thermally adhered to each other and 
the yarn has alternate twists so that S and Z twist portions are 
distributed randomly along the lengthwise direction of the yarn, and that 
the yarn has a coherent factor between 5 and 100 and a latent torque index 
between 20 T/m and 300 T/m. 
Another aspect of the present invention pertains to a cut pile carpet 
wherein the cohesive bulky carpet yarn of a polyamide continuous 
multifilament is utilized as a pile yarn. In a aspect of the present 
invention, a preferable embodiment is provided as a cut pile carpet 
comprising cut piles of a cohesive bulky poliamide multifilament yarn, 
wherein at least 50% of the filaments composing the cohesive bulky 
polyamide multifilament yarn are modified across sectioned filaments, each 
filament of which multifilament yarn has at least three projections in its 
cross section, and the filaments are thermally and partially adhered to 
each other and S and Z twists are randomly distributed along the 
lengthwise direction of the yarn, and the yarn has a latent torque 
therein. 
A further aspect of the present invention pertains to a method for 
manufacturing the cohesive bulky carpet yarn of a polyamide continuous 
multifilament yarn. 
A still further aspect of the present invention pertains to a process for 
manufacturing a cut pile carpet wherein a novel bulky carpet yarn of a 
continuous polyamide multifilament having partial and thermal adhesion and 
alternate twists is utilized as a pile yarn. 
The process of the present invention in this aspect comprises: a step of 
false twisting and thermal adhering a bulky yarn of a polyamide 
multifilament so that filaments composing the yarn are thermally and 
partially adhered to each other, and so that alternate twists are 
distributed in the yarn along the lengthwise direction of the yarn, 
whereby a cohesive bulky multifilament has a latent torque index between 
20 T/m and 300 T/m; a step of tufting the cohesive bulky multifilament 
yarn as a pile yarn on a substrate; a step of cutting the loops of the 
pile yarn so as to create cut piles; and a step of heat treating the cut 
piles by means of steam, dry heat or hot water so that true twists between 
20 T/m and 200 T/m are developed in each of the cut piles. 
It is preferable that the multifilaments composing the cohesive bulky 
polyamide yarn of the present invention are substantially made of 
aliphatic polyamide, for example nylon 6, nylon 66 or their copolymer, 
which easily increases its adhesion under the function of water molecules 
and has a tendency to thermally and partially adhere. It is also 
preferable that the total denier of the multifilament yarn is between 600 
de and 6000 de and that the thickness of each filament in denier of the 
multifilament yarn is between 6 de and 30 de. The cross sectional shape of 
each filament may be a regular circular shape, or a non-circular shape, 
such as triangular, square, cross or trilobal shape. The filament may have 
one or more hollows continuously formed therewithin along the lengthwise 
direction thereof. 
According to the present invention, it is possible to constitute the 
multifilament yarn with more than two kinds of filaments. For example, the 
yarn may be composed of two or more kinds of filaments which are different 
from each other in the polymers, the cross sectional shapes of the 
filaments, thicknesses in denier of the filaments, the thermal properties, 
the mechanical properties, the dyeabilities, and the like. In some cases, 
a part of the filaments may be a filament having an electric conductivity. 
These filaments may be doubled or blended. 
The bulky yarn of the present invention may have crimps of any shape; 
however, it is preferable that the yarn has non-helical crimps imparted by 
the turbulent jet of heated fluid, stuffing by fluid or mechanical 
stuffing. When the yarn has non-helical crimps, in the case wherein the 
bulky yarn is utilized as a pile yarn in a cut pile carpet, it is 
preferable that the total crimp is selected between 3% and 15%, more 
desirably between 5% and 10%, by varying the draft ratio while the yarn is 
being false twisted. This is because, if the total crimp exceeds 15%, the 
obtained carpet may be felt-like; and if the total crimp is less than 3%, 
the quality of the carpet may be low because the carpet is not voluminous. 
Accordingly, it is preferable for a cut pile carpet with a good quality to 
have a total crimp between 3% and 15%. 
According to the method of the present invention, the above-mentioned bulky 
yarn is fed to a false twisting and heat setting device so that false 
twists are imparted in the yarn and so that filaments composing the yarn 
become thermally and partially adhered to each other. Subsequently, the 
yarn is detwisted and taken up without removing the partial adhesion. In 
this case, it is highly preferable that false twists between 100 T/m and 
1000 T/m are imparted into the yarn by means of circulated air, and that 
then the false twists are heat set by means of saturated or superheated 
steam at a temperature higher than that where adhesion begins. The 
operating speed of the yarn is usually selected between 100 m/min and 2000 
m/min. However, if the above-mentioned false twisting and heat setting 
operation is carried out together with a spin-draw operation, the 
operating speed in the false twisting operation selected is between 1000 
m/min and 5000 m/min. 
As a result of the above-mentioned false twisting and heat setting 
operation, the portions where the thermal and partial adhesion occurs 
remains in the yarn as tight spots. To compensate the tight spots, twists 
in a reverse direction are created in the yarn. As a result, a bulky yarn 
with alternate twists, wherein filaments are thermally and partially 
adhered to each other and S and Z twists are distributed randomly along 
the lengthwise direction thereof, is obtained. The bulky yarn includes a 
latent torque which was imparted through the false twisting and thermal 
adhering operation; in other words the yarn has a latent torque index, 
which is measured in accordance with the test method explained 
hereinafter, of between 20 T/m and 300 T/m. 
The term "thermal and partial adhesion" in the present specification means 
a situation wherein a plurality of filaments are incompletely adhered to 
each other due to thermal adhesion. In other words, the degree of adhesion 
is not so high that the entire multifilament yarn is integrated in one 
body. Since the filaments are partially adhered, so that only the cohesion 
of the yarn can be maintained, the filaments can easily be separated from 
each other when a separating force is exerted on the yarn. 
The term "alternate twists" means that S and Z twist portions are randomly 
distributed along the lengthwise direction of the bukly yarn. Since the 
partial and thermal adhesion is created while the yarn is twisted due to 
the false twisting and thermal adhering operation, the adhered portions 
remain randomly in the bulky yarn as tight spots. As a result, when the 
yarn is detwisted, twists in an opposite direction are created to 
compensate for the tight spots, as if the yarn is overly detwisted. 
Accordingly, when the yarn is observed in its entirety, the yarn has a 
cohesion, as uniform as a true twisted yarn has, along the lengthwise 
direction thereof and has a substantially circular cross section. 
It is suitable that the coherency imparted to the bulky yarn by means of 
partial and thermal adhesion is between 5 and 100 in the coherent factor, 
which is measured in accordance with the test method explained 
hereinafter. If the coherent factor is smaller than 5, the coherency of 
the yarn is not sufficient so that the operabilities, especially tufting 
operability, are degraded, and the obtained cut pile carpet may be 
felt-like; in other words, the carpet may not have a good pin point 
effect. On the other hand, if the coherent factor exceeds 100, the 
coherency of the yarn is too high and the carpet is not voluminous. In 
addition, the hand of the carpet may be hard, and therefore such a high 
coherent factor is not desired. The coherent factor can be selected at a 
desired amount by varying the condition explained hereinafter, wherein the 
heat set takes place during the false twisting and thermal adhering 
operation. 
In the present invention, it is more preferable that the coherent factor be 
between 10 and 50. When the coherent factor between the above-mentioned 
range is utilized, since the bulky yarn is suitably voluminous and has a 
coherency, the cut pile carpet obtained will be the best in quality. It 
should be noted that when a bulky interlaced yarn disclosed in the 
above-mentioned U.S. Pat. No. 3,968,638 is utilized, the coherency is low 
and the handling operability is poor if a relatively low coherency is 
imparted to the yarn; for example, if the coherent factor is not more than 
15. On the other hand, the cohesive bulky multifilament yarn according to 
the present invention can maintain good coherency even if the coherent 
factor is between 5 and 15, because the yarn has alternate twists therein 
and maintains a circular cross section. As a result, the yarn has a good 
handling operability such as that of the yarn produced according to the 
known twisting and heat setting method. 
The degree of partial and thermal adhesion is expressed by an adherent 
ratio which is defined as a percentage of the number of adhered portions 
to the number of whole filaments. It is preferable that the adherent ratio 
be between 0.5% and 40%. More specifically, if the degree of adhesion is 
too large, i.e., the adherent ratio exceeds 40%, the bulky yarn has a hard 
hand, and a carpet having a good quality cannot be obtained. On the other 
hand, if the degree of adhesion is too small, i.e., the adherent ratio is 
smaller than 0.5%, the effect of the false twisting and thermal adhesion 
cannot be fully achieved, and in many cases, the yarn does not have either 
the desired coherent factor or the desired latent torque index. 
In addition, a cohesive bulky multifilament carpet yarn according to the 
present invention is required to have a latent torque between 20 T/m and 
300 T/m. The latent torque is measured in a method explained hereinafter 
and means the property by which true twists are developed in the bulky 
yarn when the bulky yarn is treated in steam or hot water while one end 
thereof is free and the bulky yarn is rotated about its axis. Accordingly, 
when the bulky yarn of the present invention is utilized to manufacture a 
carpet and when the carpet thus obtained is treated by means of steam or 
hot water, true twists are naturally developed in the pile yarn which has 
been cut, and therefore, each cut pile yarn stably coheres. 
When the latent torque index is less than 20 T/m, the bulky yarn does not 
have such a self-twisting effect, and therefore, the cut pile yarns do not 
cohere. On the other hand, if the latent torque index exceeds 300 T/m, the 
cut pile yarns cohere excessively, and therefore the hand of the carpet is 
degraded, and the quality of the carpet is low. 
It is preferable that the degree of the latent torque is between 20 T/m and 
200 T/m measured in the latent torque index. If a velour-like carpet is 
desired, a latent torque index between 20 T/m and 80 T/m is preferable. A 
latent torque index between 60 T/m and 200 T/m is preferable, when a hard 
twist like carpet is desired. 
The cohesive bulky yarn of a polyamide continuous multifilament according 
to the present invention has a sufficient amount of coherency due to the 
existence of both the partial and thermal adhesion and the alternate 
twists, and at the same time it has a substantially circular cross section 
which is similar to that of a true twisted yarn. As a result, good 
handling operabilities, especially tufting operability, can be obtained, 
and the productivity of a carpet can be increased. Since the yarn does not 
have strongly entangled portions due to the interlacing, the dyeability 
thereof is good. 
It should be noted that the bulky yarn of the present invention can provide 
a desired pile yarn having the desired appearance and hand by selecting 
the degree of the partial and thermal adhesion and the latent torque 
index. For example, when both the degree of the partial and thermal 
adhesion and the latent torque index selected are "large", the pile yarn 
becomes like a hard twist and the hand thereof becomes stiff. When the 
degree of the partial and thermal adhesion or the latent torque index 
selected is "small", the hand of the pile yarn becomes soft. 
It should also be noted that since the partial adhesion of the bukly yarn 
according to the present invention can be mechanically separated, if the 
pile yarns are mechanically treated after the bulky yarn is tufted on a 
carpet, a part of or all of the partial adhesion can be separated so that 
a carpet having a soft hand can be obtained. 
As mentioned above, a cut pile carpet, wherein a bulky cohesive 
multifilament yarn is manufactured in accordance with the conventionally 
known method, gradually loses its cohesive property due to the decrease of 
twists in the pile yarn after it is used for a long duration. On the other 
hand a carpet, wherein the bulky carpet yarn according to the present 
invention is utilized, will not lose the twists in the pile yarn even 
after it is used for a long duration. If the twists are lost, the carpet 
can recover its twists by being treated with steam or hot water because 
the pile yarn has latent torque therein. 
The above-mentioned bulky cohesive yarn of a polyamide multifilament can be 
productively and economically manufactured by feeding a bulky yarn of a 
polyamide multifilament to a false twisting and heat setting device, 
wherein false twists between 100 T/m and 1000 T/m are imparted to the yarn 
and the yarn is heat set so that the filaments are thermally and partially 
adhered to each other, and subsequently by taking up the yarn while the 
partial and thermal adhesion is left therein. 
The fed bulky yarn can be a polyamide multifilament yarn and crimps can be 
imparted therein in a known manner. Even more preferable, bulky yarns 
having non-helical crimps imparted by a heated air jet, a gear crimping or 
a stuffer box crimping, are suitable. For example, a bulky yarn can be 
utilized which is obtained after a polyamide multifilament yarn is fed 
into a heated fluid, so that loops or slacks are created in the filaments 
and is then opened under a predetermined draft ratio, such as disclosed in 
Japanese Patent Application Publication Nos. 24699/70 and 33430/71. When 
the draft ratio is low, and the loops and slacks are left in the bulky 
yarn, a spun-like and voluminous yarn having a soft hand can be obtained. 
It is also possible in the present invention that two or more kinds of 
bulky yarns are simultaneously utilized, and in some cases the bulky yarns 
may be different from each other in the shapes of the crimp, the 
thicknesses in denier, the modification ratios or the degree of the crimp, 
dyeabilities. It is preferable that the total crimp of the bulky yarn be 
between 3% and 15%. 
The total crimp of the bulky carpet yarn can be varied by changing the 
draft ratio while the yarn is being false twisted and thermally adhered. 
According to the present invention, if the total crimp of the bulky carpet 
yarn, i.e., the pile yarn, after it is false twisted and thermally 
adhered, is in a range between 3% and 15%, a cut pile carpet with a good 
quality can be obtained. 
In a process according to the present invention, the above-mentioned bulky 
cohesive multifilament yarn, which is obtained after the false twisting 
and thermal adhering operation, is utilized. The yarn is tufted on a 
substrate, e.g. fabrics of jute or split yarn, in a conventionally known 
manner, after it is dyed, if required. The density of the tufting may be 
changed in accordance with the thickness of the pile yarn. In general, it 
is preferable that the density be between 4 and 25 per one cm.sup.2. 
Thereafter, the loops of the pile yarn which have been formed by the 
tufting are cut, so that cut piles are formed. The cut piles are steam 
treated, the temperature of which is between 70.degree. C. and 100.degree. 
C.; dry heat, the temperature of which is between 100.degree. C. and 
160.degree. C.; or hot water, the temperature of which is between 
40.degree. C. and 100.degree. C., so that torque latently included in the 
pile yarn is developed and so that the cut piles are rotated so as to 
create true twists between 20 T/m and 200 T/m. The coherency of each cut 
pile depends on the number of the true twists therein. If the true twists 
are less than 20 T/m, the coherency of the cut pile is not sufficient and 
the surface of the carpet becomes felt-like. On the other hand, if the 
true twists are more than 200 T/m, the coherency is excessive and the hand 
thereof becomes stiff. 
The operation for developing the spontaneous true twist may take place 
together with the scouring operation or the dyeing operation. In some 
cases, the developing operation may take place separately. Before or after 
the operation for developing true twists, a mechanical operation, such as 
a rubbing operation or a raising operation, may be applied to the yarn so 
that adhesion between the filaments may be removed. 
With reference to the accompanying drawings, the present invention will now 
be explained in detail.

Referring to FIG. 1, a bulky yarn 1 withdrawn from a package P is wound 
around a feed roller 2 several times and is fed at a predetermined 
constant speed. It is preferable that a separate roller 3 disposed in 
parallel with the feed roller is grooved around the peripheral surface 
thereof so that the passage of the yarn 1 can be stable. A roller 4 which 
is freely rotatable is pressed on the surface of the feed roller 2 so as 
to nip the yarn 1 therebetween so that twists running back from the 
downstream thereof are prevented from running back to the upstream. 
Thereafter, the bulky yarn 1 is fed to a heater 5 where it is heated to a 
temperature higher than the softening point of the yarn. It is preferable 
that the heater 5 is of a non-contact type pipe heater as illustrated in 
FIG. 1 and that the yarn is directly heated by means of steam which can 
easily cause adhesion to a polyamide yarn. The yarn 1 leaves the heater 5 
then enters a false twist nozzle (air torque jet) 6 wherein a circulated 
gas flow is utilized where false twists are imparted to the yarn 1. The 
false twists run back along the yarn 1 in the heater 5 and reach the nip 
line between the feed roller 2 and the press roller 4. The number of the 
false twists imparted by the false twist nozzle 6 is required to be 100 
T/m and 1000 T/m. If the number of the twists is less than that range, the 
self-twisting effect due to the latent torque is low. On the other hand if 
the number of the twists is more than 1000 T/m, it is very difficult to 
stably impart twists to the yarn 1. 
It is possible that the heater 5 and the false twist nozzle 6 are connected 
to each other and the single and same heated gas supplied to both of the 
parts. However, in this case, since the yarn will be wound while it is 
hot, the quality of the obtained yarn may be degraded. It is preferable 
that the heater 5 and the false twist nozzle 6, are separately disposed as 
illustrated in FIG. 1 and that in the twist nozzle 6 the false twists are 
imparted while the yarn is cold by means of air at a normal temperature. 
It is also preferable that, if the heater is of pipe heater type and is 
supplied with saturated or superheated steam as a heating medium, the 
inner diameter d in mm of the inlet and outlet thereof satisfy the 
following equation: 
##EQU1## 
wherein De is the thickness in denier of a yarn to be heat treated. When 
the diameter d selected is in the range mentioned above, the filaments in 
the yarn can be thermally and partially adhered because the steam 
introduced into the heater does not escape freely through the inlet and 
outlet, so that the pressure in the heater is maintained high, and the 
yarn may not be damaged while it passes through the inlet and outlet 
because the inner diameter d of the inlet and outlet is larger than the 
diameter of the yarn. 
The means for imparting false twists to the yarn may be not only a false 
twist nozzle 6 as explained above, but also any other false twisting means 
such as a friction false twisting means. In the above-mentioned false 
twisting nozzle 6, the partially adhered portions in the bulky yarn, i.e., 
the tight spots, created within the heater 5 are not detwisted, so that 
they easily remain in the bulky yarn as alternate twists, i.e., S and Z 
twists; as a result, the nozzle 6 is preferable because the coherency of 
the bulky yarn is increased. 
The yarn thus false twisted is wound around a take up roller 7 several 
times and is advanced to a winder 10 where it is formed into a package. A 
separate roller 8, disposed rotatably and in parallel with the take up 
roller 7 is grooved around the peripheral surface thereof so that the yarn 
is stably advanced on the take up roller 7. It is preferable that a 
rotatable roller 9 is pressed against the take up roller 7 so as to nip 
the yarn therebetween so that the false twists are prevented from running 
into the winding means. 
In this method, when the heating conditions of the heater 5, i.e., the 
temperature and the pressure of steam, if steam is utilized as a heating 
medium, the number of false twists, the tension in the yarn while it is 
treated, are varied, the total crimp, the coherent factor, the latent 
torque index of the bulky carpet yarn thus obtained can be changed to the 
desired values. In general, in the method of the present invention, since 
the false twisting and thermally adhering operation takes place under a 
certain tension, the total crimp of the obtained carpet yarn is a little 
bit smaller than that of the feed yarn. Accordingly, the total crimp of 
the produced yarn is in a range between 3% and 15%, which range is 
preferable for a pile yarn of a cut pile carpet. 
In the embodiment of FIG. 1, a bulky multifilament yarn which has been 
previously manufactured through an operation for imparting crimps is fed 
to a false twisting and heat setting operation. It is possible that the 
operation for imparting crimps and the operation for false twisting and 
heat setting are continuously carried out as illustrated in FIG. 7. 
Furthermore, the operations for imparting crimps and for false twisting 
and heat setting may be carried out together with the operation for 
spinning and drawing as illustrated in FIG. 8. 
In accordance with the above-explained method of the present invention, 
only when a bulky polyamide multifilament yarn is passed through a false 
twisting and heat setting process, a bulky cohesive polyamide 
multifilament yarn which has suitable bulkiness, coherency and latent 
torque and which is preferable as a pile yarn for a cut pile carpet can be 
manufactured. Accordingly, the method is superior in productivity to the 
conventional method, wherein additional twisting and heat setting are 
carried out. Since the construction of the equipment is simple, the 
manufacturing cost according to the present invention can be lowered. When 
the method is compared with a method wherein a yarn is entangled by means 
of interlacing, no special nozzle for imparting entanglement to the yarn 
is required, and the produced yarn is free from dyeing specks. 
With reference to FIGS. 2 and 3, cut pile carpet yarns are illustrated 
wherein the bulky carpet yarn manufactured in accordance with the 
above-mentioned method is utilized. In FIGS. 2 and 3, the reference 
numerals 11 and 12 designate a pile and a substrate, respectively. In 
accordance with a process according to the present invention, just after 
the cut piles 11 are formed, as illustrated in FIGS. 2 and 5, alternate 
twists comprising S and Z twist portions are in the piles 11. The 
alternate twists are also illustrated in FIG. 9. However, after the 
operation for developing true twists is carried out by means of steam or 
hot water, true twists, i.e., S twists, the direction of which is the same 
as that of the false twists, i.e., S twists, are developed as illustrated 
in FIGS. 3, 6, 10 and 11. After the operation, there are tendencies that 
the length of the pile 11 is somewhat shortened from L.sub.1 to L.sub.2, 
and that on the other hand, the thickness of the pile 11 is somewhat 
increased from D.sub.1 to D.sub.2. If the thermal shrinkage ratio, the 
coherency and the latent torque index of the bulky yarn utilized for a 
pile yarn are adequately selected, the changes in size during the 
operation can be minimized. 
As illustrated in FIG. 12, which is a plan view of FIG. 11, the carpet thus 
obtained has a very excellent pin-point effect. 
According to the process of the present invention, during the operation for 
developing the true twists, if the conditions for treating, i.e., 
temperature and time duration, are varied locally, the coherency of the 
pile whose treating conditions are varied can be changed. Accordingly, 
even if the same bulky carpet yarn is tufted on a carpet as a pile yarn, a 
pattern can be applied to the carpet by locally changing the heat treating 
conditions. 
Naturally, it is possible to apply a pattern to a carpet by locally 
changing the kinds of density or cut length of bulky carpet yarns. In such 
a case, it is also possible to facilitate patterning by locally changing 
the operational condition for developing true twists. 
Methods for measuring the total crimp, the coherent factor, the latent 
torque index, the adherent ratio, the bulkiness and the number of loops 
utilized in this specification will now be explained in detail. 
(1) Total Crimp (TC) 
The total crimp indicates the degree of crimp of a yarn. A bulky yarn of 
one meter length is withdrawn from a package, and it is loaded under 0.1 
g/de for one minute. After the crimp is developed in boiling water for 30 
minutes while the test piece is in a free condition, the test piece is 
dehydrated, and then it is dried for one day and night under normal 
conditions. The test piece is loaded for one minute under 0.1 g/de and the 
length thereof l.sub.1 is measured. After the test piece is maintained in 
a free condition for three minutes, while it is loaded for one minute 
under 2 mg/de, the length of the test piece l.sub.2 is measured. Based on 
the measured data, the total crimp (TC) is calculated in accordance with 
the following equation. 
##EQU2## 
(2) Coherent Factor (CF) 
The coherent factor indicates the degree of coherency of a yarn. A yarn, 
ends of which are free, is located horizontally, and then the yarn is 
vertically separated into two portions along the axis thereof. The upper 
half portion of the yarn is picked up by a hook, and the remaining lower 
half portion of the yarn is vertically loaded under 0.2 g/de, the amount 
being calculated for the total denier of the yarn. The width W in cm 
between the upper and lower half portions is measured. The coherent factor 
(CF) is calculated in accordance with the following equation. 
EQU CF=100/W 
Note that the length of the test piece is equal to or more than 50 cm and 
the test piece is randomly sampled. If the coherent factor is large, the 
coherency of the yarn is high. 
(3) Latent Torque Index 
A bulky yarn of 30 cm length is sampled from a cheese, and a mark is put at 
one end of the yarn by means of an oily ink. The yarn is hung in saturated 
steam (about at 100.degree. C.) for five minutes while one end thereof is 
free, and the number of twists which are created by rotation of the yarn 
is counted. The number of the twists is converted into the number of the 
twists per meter which is called the latent torque index. If the index is 
large, the torque latently included in the yarn is high. 
(4) Adherent Ratio 
A microscopic photograph of the cross section of a yarn is taken, and the 
number of the portions where the boundary between the adjacent filaments 
is not clearly observed, which portions are considered as adhered 
portions, is counted. (Since the adhesion is caused by a point contact, if 
two or more portions of the yarn are not clear, two or more portions are 
counted individually.) The counting operation utilizing the cross 
sectional microscopic photograph is carried out over ten times with 
respect to the test pieces which are randomly sampled along the lengthwise 
direction of the yarn. The arithmetical average of the obtained numbers is 
calculated and is called the number of adhesions. The adherent ratio is 
calculated in accordance with the following equation. 
##EQU3## 
(5) Bulkiness 
A bulky continuous multifilament yarn is wound to form a skein, and after 
the skein is heat treated in boiling water for 30 minutes, while it is in 
a free condition, it is dehydrated and dried for one day and night under 
normal conditions, i.e., at the temperature of 20.degree. C. and the 
relative humidity of 65%. 
The yarn, after it is subjected to an operation for developing twists, is 
wound 100 times around a reel having a width of 10 cm, under a tension of 
4 mg/de. Utilizing the volume of the wound yarn V in cm.sup.3, which is 
calculated based on the thickness of the wound yarn layer and the width of 
the reel, and the weight of the yarn W in g, the bulkiness is calculated 
by the following equation. 
EQU Bulkiness=V/W (cm.sup.3 /g) 
(6) Number of loops 
A bulky continuous multifilament yarn 10 cm long is placed on a black mount 
and is sandwiched between the mount and a transparent plate glass. In this 
specification, the term "loop" is defined as a yarn portion projecting 
more than 0.5 mm high upwards or downwards from the periphery of the yarn 
while the yarn is sandwiched between the mount and the glass as mentioned 
above. The loops are counted and, then, the number of loops per cm is 
obtained. 
Examples of the present invention will now be explained. In Examples 1 and 
2, the tufting operability is judged on the number of the defects of the 
tuft, i.e., stitch damages caused by the fallen piles. If the number is 
less than 0.01 per one m.sup.2, the tufting operability is expressed with 
O. If the number is between 0.01 and 0.1 per one m.sup.2, the tufting 
operability is expressed with .DELTA.. If the number is more than 0.1 per 
one m.sup.2, the tufting operability is expressed with X. The appearance 
of a carpet is judged on the subjective tests effected by an expert. 
EXAMPLE 1 
A multifilament yarn of nylon 6 containing TiO.sub.2 as a delusterant of 
0.06% by weight, each filament of which yarn has a trilobal cross section, 
is impinged upon a wire net by means of a heated fluid jet nozzle. As a 
result, a bulky continuous multifilament yarn of nylon 6 having the 
following properties is manufactured, and it is fed to the false twisting 
and heat setting device, illustrated in FIG. 1, so that it is false 
twisted and heat set. 
______________________________________ 
Fed Bulky Yarn 
Thickness 2500 denier/136 filaments 
Total Crimp 15% 
Bulkiness 16 cm.sup.3 /g 
Number of Cimp 400/m 
Coherent Factor 100/14 
Latent Torque Index 
0 T/m 
______________________________________ 
In the above-mentioned example, the heater 5 was a pipe heater and had a 
length of 300 mm and an inner diameter of 5 mm. The inlet and outlet ends 
of the heater 5 were choked like an orifice, the inner diameter of which 
was 1.5 mm. Within the pipe heater 5, superheated steam, the temperature 
of which was 200.degree. C. and the pressure of which was between 2.0 
kg/cm.sup.2 and 3.0 kg/cm.sup.2, was introduced. On the other hand, the 
false twisting nozzle 6 was provided with a yarn passage of a pipe-shape 
having an inner diameter of 3 mm. An air inlet of a slit shape having a 
depth of 0.5 mm and a width of 3 mm was disposed tangentially to the yarn 
passage, so that a circulated air flow was created within the yarn 
passage. The treating speed was selected as 500 m/min, the overfeed ratio 
of the yarn while it was treated was selected as 5%. The pressure of the 
air at room temperature fed to the false twisting nozzle was variously 
changed and the tests were repeated. 
Various properties of the bulky yarns obtained through the tests were 
measured, and at the same time the yarns were tufted to substrates, i.e., 
jute fabrics, as pile yarns so that cut pile carpets were manufactured. 
The tufting machines were selected to be of a gauge of 5/32 inch, a pile 
stitch of 9 per inch and a pile height of 20 mm. The obtained carpets were 
dyed in boiling water so that the torque in the piles was developed. The 
appearances and hands of the carpets were judged on the above-mentioned 
criteria. The results are described in Table 1. 
TABLE 1 
__________________________________________________________________________ 
Data No. 1 2 3 4 5 6 7 
__________________________________________________________________________ 
Conditions 
Pressure of air 
Kg/cm.sup.2 
0 1.0 2.0 3.0 4.0 5.0 5.0 
Number of false twists 
T/m 0 80 150 380 450 500 500 
Pressure of steam 
Kg/cm.sup.2 
2.0 
2.0 2.0 2.0 2.0 2.3 3.0 
Bulky yarn 
Total crimp 
% 13.0 
9.0 7.0 7.0 6.5 6.0 4.3 
Bulkiness cm.sup.3 /Kg 
14 12 11 10 9.6 9.0 6.5 
Adherent ratio 
% 0 1.8 4.8 10 20 25 45 
Coherent factor 
-- 7.1 
12.0 18.2 
21.7 
28.6 33.3 66.7 
Latent torque index 
T/m 0 30 60 90 100 110 150 
Tufting operability 
x .DELTA. 
O O O O O 
Appearance of carpet 
poor 
good good 
good 
excellent 
excellent 
poor 
Hand of carpet Felt- 
Velvet- Hard 
twist like 
Too 
like 
like Stiff 
__________________________________________________________________________ 
In the Table 1, the test resulting in Data Nos. 2 through 6 were carried 
out in accordance with the present invention, and since the obtained bulky 
yarns had suitable coherencies, which were the second set of effects of 
the crimp and the latent torques, the carpets manufactured therefrom were 
characterized by superior qualities, both in appearance and hand, because 
the piles in the carpets stood vertically. On the other hand, in Data No. 
1 wherein the pressure of the air was selected to be zero so that no false 
twists were imparted to the yarn, low coherency was obtained in the yarn 
because the filaments were not adhered. In the test resulting in Data No. 
7, wherein the pressure of the steam was raised excessively, excessive 
adhesion was created to the filaments, and the bulky yarn became stiff as 
a string and the bulkiness thereof also became degraded. 
EXAMPLE 2 
Using the method of Example 1, the pressure of the air supplied to the 
false twisting nozzle 6 is selected at 5.0 kg/cm.sup.2, and the pressure 
of the steam supplied to the heater 5 was changed variously. The results 
are described in Table 2. 
In the test resulting in Data Nos. 8 and 9 wherein no steam and steam of 
low pressure were supplied to the heater, respectively, there was no 
adhesion, and therefore the coherency of the obtained bulky yarn was low. 
Since the latent torque index was also low, not only the tufting 
operability was degraded but also the obtained cut pile carpets were 
felt-like and the quality thereof was low. As the pressure of the steam 
was increased as described in the test resulting in Data Nos. 10 through 
12, there was suitable adhesion was caused, and the coherency and the 
latent torque index were increased. As a result, various types of carpet 
of high quality from a plush type carpet, wherein twists were small, to a 
hard twist type carpet were obtained. 
TABLE 2 
__________________________________________________________________________ 
Data No. 8 9 10 11 12 13 
__________________________________________________________________________ 
Conditions 
Pressure of steam 
Kg/cm.sup.2 
0 1.0 1.0 1.8 2.5 4.0 
Number of false twists 
T/m 500 500 500 500 500 500 
Bulky Yarn 
Total crimp 
% 16.0 13.0 
9.8 7.0 6.0 4.0 
Bulkiness cm.sup.3 /g 
16.5 14.8 
12.0 
10.5 9.0 7.0 
Adherent ratio 
% 0 0 2.5 10 25 5.0 
Coherent factor 
-- 3.6 4.5 5.9 12.5 33.3 14.3 
Latent torque index 
T/m 0 18 50 80 110 140 
Tufting operability 
x x O O O O 
Appearance of carpet 
poor poor 
good 
excellent 
excellent 
poor 
Hand of carpet Felt-like Good Too 
stiff 
__________________________________________________________________________ 
However, if the pressure of the steam was too excessive, as described in 
the test resulting in Data No. 13, there was excessive adhesion caused, 
and therefore the yarn cohered like a string and the hand of the carpet 
became hard. 
EXAMPLE 3 
A bulky polyamide multifilament yarn of 3200 de/272 fil which was composed 
of a nylon 6 filament having a trilobal cross section, the modification 
ratio of which was three and which had a total crimp of 14%, was fed to an 
air false twist nozzle at a speed of 500 m/min so that false twists of 300 
T/m were imparted into the yarn, and then the false twists were heat set 
and thermally and partially adhered by means of a pipe heater, having a 
length of 40 cm, where superheated steam, the industrial pressure of which 
was 2.0 kg/cm.sup.2 and the temperature of which was 200.degree. C., was 
utilized. A bulky cohesive multifilament yarn, having an adherent ratio of 
5%, a total crimp of 8% and a latent torque index of 50 T/m, and 
comprising alternate twists, i.e., S and Z twists, was obtained. The 
obtained bulky yarn was utilized as a pile yarn, and a cut pile carpet was 
manufactured in accordance with a tufting method. The conditions of the 
tufting machine were the same as those of the tufting machine utilized in 
Example 1. 
Since the pile yarn had good coherency due to the alternate twists, the 
tufting operability was very good. The operative efficiency was three 
times as good as that which was obtained for the bulky multifilament yarn 
having no twists. 
When the cut pile carpet was dyed in boiling water, it was uniformly dyed 
without any dyeing specks, and the torque in the pile yarn was developed 
so that true twists of about 50 T/m were developed in each cut pile and so 
that the piles became circular. As a result, a velour type carpet was 
obtained. 
The obtained cut pile carpet was placed on a busy corridor, and one month 
after the carpet was placed there, the coherency of the piles was observed 
and it was found that the piles maintained coherency which was almost the 
same as that when it was initially placed there. 
EXAMPLE 4 
Referring to FIG. 7, a continuous undrawn yarn of nylon 6 multifilament 
yarn 31 melt spun and wound around a bobbin 33 was prepared. The yarn was 
of 4800 denier/136 fil, and each filament had a trilobal cross section, 
the modification ratio was 3.5. The yarn 31 was withdrawn from the bobbin 
33 and was slightly prestretched between a feed roller 35 with a press 
roller 36 and a prestretch roller 37 with a rotatable separate roller 38. 
After the yarn 31 was wound around the prestretch and separate rollers 37 
and 38 several times, it was advanced to a draw roller 39 with a rotatable 
roller 40 and wound therearound several times. The ratio between the 
peripheral speeds of the feed and draw rollers 35 and 39, i.e., draw 
ratio, was 3.70. The draw roller 39 was heated at a temperature of 
185.degree. C. and had a peripheral speed of 1000 m/min. The yarn was 
subject to a texturing operation by means of a heated fluid jet nozzle 41 
which had a construction similar to that disclosed in FIG. 2 of Japanese 
Patent Application Laid-Open No. 31848/78 and which utilized steam, the 
temperature of which was 210.degree. C. and the pressure of which was 6.0 
kg/cm.sup.3. The yarn 31 was overfed to a roller 43 with a rotatable free 
roller 44 via a guide 42, the overfeed ratio of the yarn between the draw 
roller 39 and the roller 43 was 60%. The yarn 31 was drafted between the 
roller 43 and a draft roller 45 under various tensions in the yarn between 
0 g and 1000 g. The draft roller 45 had a rotatable separate roller 46 and 
a press roller 47. The characteristics of the yarn thus obtained under a 
draft tension of 300 g are as follows. 
______________________________________ 
Thickness of the yarn 1600 de 
Total crimp 14% 
Number of crimps 500/m 
Bulkiness 14 cm.sup.3 /g 
Coherent factor 7.1 
Latent torque index 0 T/m 
Number of Loops 20/cm 
______________________________________ 
The above-mentioned bulky continuous multifilament yarns were then 
continuously subjected to a false twisting and heat setting operation 
according to the present invention. A pipe heater 49 had a length of 400 
mm and an inner diameter of 10 mm. The inner diameter of the inlet and 
outlet of the heater was 1.1 mm, and the heater was supplied with 
superheated steam, the temperature of which was 200.degree. C. and the 
pressure of which was 2.3 kg/cm.sup.2. A false twisting nozzle 50 was the 
same as that utilized in Example 1. The overfeed ratio while the yarn was 
false twisted was 3.0%. The pressure of the compressed air fed to the 
false twisting nozzle 50 was 4.0 kg/cm.sup.2. An example of the obtained 
yarn, after it was subjected to an operation for developing twists, is 
illustrated in FIG. 13. 
The various properties of the bulky yarns obtained were measured and, at 
the same time, the yarns were tufted to substrates of a plain weave of 
polypropylene split yarn as pile yarns, and cut pile carpets were 
manufactured. The tufting machines were selected to be of a gauge of 1/10 
inch, a pile stitch of 9 per inch and a pile height of 15 mm. The obtained 
carpets were dyed in boiling water, and the appearances and hands thereof 
were judged based on the above-mentioned criteria. In the test resulting 
in Data Nos. 14 through 18, the tufting operability was good. The results 
are described in Table 3. 
In this example, it was observed that, when a bulky continuous 
multifilament yarn having loops therein is false twisted, and thermally 
and partially adhered in accordance with the present invention, the 
bulkiness of the bulky cohesive continuous multifilament yarn is increased 
due to the remaining loops and the yarn becomes soft to the touch. 
It is preferable that the total crimp of the bulky cohesive continuous 
multifilament yarn obtained should be between 3% and 12%, and that the 
number of loops of the yarn should be between 2 and 100. 
TABLE 3 
__________________________________________________________________________ 
Data No. 14 15 16 17 18 
__________________________________________________________________________ 
Conditions 
Draft tension 
g 0 100 300 500 1000 
Number of false twists 
T/m 650 650 650 650 650 
Pressure of steam 
kg/cm.sup.2 
2.3 2.3 2.3 2.3 2.3 
Bulky yarn 
Total crimp 
% 6.0 7.0 7.5 6.4 5.0 
Number of loops 
/cm 280 90 25 6 0 
Bulkiness cm.sup.3 /g 
9.5 8.0 7.5 7.0 6.0 
Adherent ratio 
% 14.0 
18.0 20.0 24.0 28.0 
Coherent factor 
-- 24.0 
33.0 30.0 28.0 16.0 
Latent Torque Index 
T/m 60 123 120 100 80 
Carpet 
Appearance of carpet 
good 
excellent 
excellent 
excellent 
good 
Hand of carpet low worsted spun yarn like 
a little 
pin- bit 
point stiff 
effect 
__________________________________________________________________________ 
EXAMPLE 5 
Referring to FIG. 8, a pair of nylon 6 multifilament yarns, wherein each 
filament had a trilobal cross section, were melt spun from a spinning 
nozzle 61 and cooled while they advanced within cooling chambers 62. After 
the yarn 60 was subjected to an finishing operation by means of a pair of 
finishing rollers 63, which were driven at a relatively low speed, the 
yarn 60 was turned by a turn-over roller 64 and taken up by means of a 
goddet roller 65. The peripheral speed of the goddet roller 65 was about 
770 m/min. A multifilament nylon 6 undrawn yarn of SB 3000 de/68 fil was 
obtained. A nozzle 66 for entangling filaments in a yarn was disposed 
between the goddet roller 65 and a feed roller 67 so that the finish 
imparted to the yarn 60 at the finishing rollers 63 was uniformly 
distributed between the filaments. The feed roller was heated at a 
temperature of 50.degree. C. The yarn was drawn between the feed roller 67 
and a pair of draw rollers 68 and 69, which were heated at a temperature 
of 195.degree. C., and the peripheral speed of which was 2500 m/min. The 
draw ratio was 3.43 and a drawn yarn having thickness of 875 de/68 fil was 
obtained. The obtained drawn yarn, which was preheated on the draw rollers 
68 and 69, was then subjected to a crimping operation by means of an air 
stuffing device 70, which had a construction similar to that disclosed in 
Japanese Patent Application Laid-open No. 45420/78 and wherein superheated 
steam, the temperature of which was 190.degree. C. and the pressure of 
which was 5 kg/cm.sup.2, was utilized. The above-mentioned crimping 
operation was effected while the yarn was overfed from the draw rollers 68 
and 69 to a delivery roller 74, since the peripheral speed of the delivery 
roller 74 was 2000 m/min. The over feed ratio was 25%. The bulky 
multifilament yarn thus obtained was then supplied into a pipe heater 71 
for thermally and partially adhering the false twists imparted to the yarn 
by means of a false twisting air nozzle 72 and run back along the yarn. 
The pipe heater 71 had a length of 600 mm and an inner diameter of 10 mm. 
The inner diameter of both the inlet and outlet of the heater 71 has 1.2 
mm; and the heater was supplied with superheated steam, the temperature of 
which was 195.degree. C. and the pressure of which was 3 kg/cm.sup.2. The 
false twisting air nozzle 72 was supplied with compressed air, the 
pressure of which was 4.0 kg/cm.sup.2. The bulky cohesive multifilament 
yarn thus obtained was taken up by means of a winding apparatus 73 
disclosed in U.S. Pat. No. 4,033,519. The winding speed of the apparatus 
73 was 1950 m/min. 
The properties of the obtained bulky cohesive continuous multifilament 
nylon 6 yarn and the carpet wherein the yarn was utilized were as follows. 
______________________________________ 
Thickness in denier of the yarn 
1000 de/68 fil 
Total crimp 6.0% 
Coherent factor 40 
Bulkiness 9.0 cm.sup.3 /g 
Adherent ratio 25 
Latent torque index 150 T/m 
Tufting operability 0.6/hr 
(Break down ratio of the tufting 
machine) 
Appearance of carpet excellent 
Hand of carpet worsted spun 
yarn like 
______________________________________ 
EXAMPLE 6 
A bulky polyamide multifilament yarn of 1600 de/136 fil which was composed 
of a nylon 6 filament having a Y shaped cross section, the modification 
ratio of which was two and which had a total crimp of 16%, was false 
twisted at a speed of 500 m/min by means of an air false twisting nozzle, 
so that false twists of 600 T/m were imparted to the yarn. The false 
twists were heat set and thermally and partially adhered by means of a 
pipe heater, having a length of 40 cm. The inner diameter of the inlet and 
outlet of the heater was 1.2 mm. In the heater, superheated steam, the 
industrial pressure of which was 2.0 kg/cm.sup.2 and the temperature of 
which was 220.degree. C., was utilized. A pile yarn of an alternate 
twisted yarn type, having an adherent ratio of 30%, a total crimp of 7% 
and a latent torque index of 150 T/m, was obtained. 
The pile yarn was tufted on a substrate by means of a tufting machine, the 
gauge of which was 1/10 inch, so that a cut pile carpet of hard twist 
having a pile stitch of ten per inch and a pile height of 20 mm was 
obtained. The tufting operability was very good, and the suspension ratio 
of the operation was decreased to that of one fifth of non-twisted pile 
yarn. 
When the cut pile carpet was treated in boiling water, true twists of about 
100 T/m were developed in each pile, and a carpet having a quality which 
was equal to that of a carpet utilizing a known cohesive bulky yarn was 
obtained through the twisting and heat set. 
The obtained cut pile carpet was placed on a busy corridor, and one month 
after the carpet was placed there, the coherency of the piles were 
observed and it was found that the piles maintained coherency which was 
almost the same as that of when it was initially placed there. 
With reference to FIG. 4, it is preferable that a cohesive bulky synthetic 
multifilament yarn, which is utilized as a pile yarn, is composed of 
filaments, at least 50%, preferably more than 80% of which are trilobal 
cross sectioned filaments, each of which has three projections A, and the 
filaments are thermally and partially adhered to each other. In the 
cohesive bulky synthetic multifilament yarn, since almost all the 
filaments are modified cross sectioned filaments having a trilobal cross 
section and three projections in its cross section, almost all the adhered 
portions B are located at the projections A, and the filaments are adhered 
to each other in point contact. As a result, although the whole yarn has a 
suitable coherency due to the adhesion, the hand of the yarn is not so 
stiff as the usual adhered yarn, but is very soft. 
The degree of adhesion should be determined based on the degree of 
coherency and hand which are required of a pile yarn. If a velour-like 
carpet is desired, it is preferable that the adherent ratio be between 
0.5% and 20%. If a hard twist like carpet is desired, it is preferable 
that the adherent ratio be between 20% and 40%. 
Please note that the pile yarn illustrated in FIG. 4 includes not only 
modified cross sectioned filaments 21 but also electrically conductive 
conjugate filaments 22 comprising a non-conductive constituent of Nylon 6 
and an electrically conductive constituent of Nylon 6 and carbon black so 
that the yarn can prevent electricity. 
The pile yarn utilized in a cut pile carpet has filaments partially and 
thermally adhered to each other as mentioned above. At the same time as 
illustrated in FIG. 5 the yarn has alternate twists, i.e., S and Z twist 
portions (designated by C and D in FIG. 5, respectively) distributed 
randomly along the lengthwise direction thereof. As a result, the whole 
yarn has a circular cross section, as a true twist yarn has, and is 
coherent. Furthermore, the yarn has a latent torque, i.e., the property to 
rotate by itself when it is heat treated while its one end is held and the 
other end is free. As a result, when the yarn 11 is tufted on a substrate 
12 to form piles, and when the piles are heat treated after the piles are 
cut, the true twists are developed and the filaments in each pile yarn 
cohere as illustrated in FIG. 6.