U.S. patent number 3,596,458 [Application Number 04/618,469] was granted by the patent office on 1971-08-03 for spun yarn of elastic fiber and preparation thereof.
This patent grant is currently assigned to Asahi Kasei Kogyo Kabushiki Kaisha. Invention is credited to Fumio Nakajima, Hiroshi Nakano, Hideo Takai.
United States Patent |
3,596,458 |
Nakano , et al. |
August 3, 1971 |
SPUN YARN OF ELASTIC FIBER AND PREPARATION THEREOF
Abstract
A spun yarn of a 100 percent elastic fiber or of an elastic
fiber blended with a hard fiber. The yarn is prepared by stretching
and heat setting a multifilament yarn or tow of the elastic fiber,
stretch breaking, drawing, if necessary, and twisting. The blended
yarn is prepared by, after the stretch breaking of the basic
elastic fibers and before the drawing, blending with hard fiber
roving. The yarn is prepared by employing a modified direct
spinning machine equipped with top and bottom aprons in a stretch
breaking zone between the back roll and the intermediate roll; the
aprons being driven by the revolution of the intermediate roll.
Inventors: |
Nakano; Hiroshi (Suita-shi,
JA), Takai; Hideo (Fuji-shi, JA), Nakajima;
Fumio (Yoshiwara-shi, JA) |
Assignee: |
Asahi Kasei Kogyo Kabushiki
Kaisha (Osaka, JA)
|
Family
ID: |
26383502 |
Appl.
No.: |
04/618,469 |
Filed: |
February 24, 1967 |
Foreign Application Priority Data
|
|
|
|
|
Jul 6, 1966 [JA] |
|
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41/43692 |
|
Current U.S.
Class: |
57/2; 57/12;
57/254; 57/309; 139/420R; 19/.46; 57/225; 57/255; 57/315 |
Current CPC
Class: |
D01H
1/00 (20130101); D02G 3/328 (20130101); D02G
3/324 (20130101); D01H 2700/24 (20130101) |
Current International
Class: |
D01H
1/00 (20060101); D02G 3/22 (20060101); D02G
3/32 (20060101); D01g 001/08 (); D02g 003/04 () |
Field of
Search: |
;57/2,3,58.91,140,14BL,139,152,157,160,163,156
;19/.30,.32,.35,.39,.43,.56 ;139/420 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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235,598 |
|
Oct 1961 |
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AU |
|
681,859 |
|
Mar 1964 |
|
CA |
|
467,251 |
|
Sep 1935 |
|
GB |
|
996,874 |
|
Jun 1965 |
|
GB |
|
885,971 |
|
Jan 1962 |
|
GB |
|
Primary Examiner: Watkins; Donald E.
Claims
We claim:
1. A method of producing a spun yarn consisting of 100 percent of
an elastic staple fiber, said method comprising preliminarily
stretching and heat setting a tow of 100 percent elastic filaments,
stretch breaking the stretched and heat-set tow, drawing the
resulting elastic staple fiber, directly spinning the elastic
staple fiber to a spun yarn, mixing said spun yarn with additional
textile materials to convert same to a mixed state and then
subjecting the said spun yarn in a low-tensioned state to free
relaxation by treatment with a member selected from the group
consisting of steam and boiling water to thereby impart to the
blended yarn excellent elasticity and high bulkiness resulting from
the shrinking of the elastic fiber during the relaxation.
2. A method according to claim 1 wherein the mixed state to which
the spun yarn is converted is in the form of a core spun yarn.
3. A method according to claim 1 wherein the mixed state to which
the spun yarn is converted is in the form of a covered yarn.
4. A method according to claim 1 wherein the mixed state to which
the spun yarn is converted is in the form of a fabric.
5. A method of producing an elastic, bulky blended spun yarn of
elastic staple fiber and hard fiber, said method comprising
stretching and heat setting a tow of 100 percent elastic filaments,
stretch breaking the stretched and heat-set tow, blending same with
a hard fiber roving, drawing the thus blended materials, directly
spinning same to a spun yarn, mixing said spun yarn with other with
additional textile materials to convert same to a mixed state, and
then subjecting the said spun yarn in a low-tensioned state to free
relaxation by treatment with a member selected from the group
consisting of steam and boiling water to thereby impart to the said
blended spun yarn excellent elasticity and high bulkiness resulting
from the shrinking of the elastic fiber during the relaxation.
6. A method according to claim 5 wherein the mixed state to which
the spun yarn is converted is in the form of a core spun yarn.
7. A method according to claim 5 wherein the mixed state to which
the spun yarn is converted is in the form of a covered yarn.
8. A method according to claim 5 wherein the mixed state to which
the spun yarn is converted is in the form of a fabric.
9. A method of producing a spun yarn consisting of 100 percent of
an elastic staple fiber, said method comprising preliminarily
stretching and temporarily heat setting a tow of 100 percent
elastic filaments, stretch breaking the stretched and heat-set tow,
drawing the resulting elastic staple fiber, directly spinning the
elastic staple fiber to a spun yarn and subjecting said spun yarn
to a post treatment.
10. A method according to claim 9 wherein said post treatment
comprises subjecting the said spun yarn in a low-tensioned state to
free relaxation by treatment with a member selected from the group
consisting of steam and boiling water to thereby impart to the said
spun yarn excellent elasticity and high bulkiness resulting from
the shrinking of the elastic fiber during the relaxation.
11. A method according to claim 10 and further comprising mixing
said spun yarn with additional textile materials to convert same to
a mixed state in the form of a core spun yarn before subjecting
same to said free relaxation.
12. A method according to claim 10 and further comprising mixing
said spun yarn with additional textile materials to convert same to
a mixed state in the form of a covered yarn before subjecting same
to said free relaxation.
13. A method according to claim 10 and further comprising mixing
said spun yarn with additional textile materials to convert same to
a mixed state in the form of a fabric before subjecting same to
said free relaxation.
14. A method of producing an elastic, bulky blended spun yarn of
elastic staple fiber and hard fiber, said method comprising
stretching and heat setting a tow of 100 percent elastic filaments,
stretch breaking the stretched and heat -set tow, blending same
with a hard fiber roving, drawing the thus blended materials and
directly spinning same to a spun yarn.
15. A method according to claim 14 further comprising subjecting
the said spun yarn in a low-tensioned state to free relaxation by
treatment with a member selected from the group consisting of steam
and boiling water to thereby impart to the said blended spun yarn
excellent elasticity and high bulkiness resulting from the
shrinking of the elastic fiber during the relaxation. 16A method
according to claim 15 and further comprising mixing said spun yarn
with additional textile materials to convert same to a mixed state
in the form of a core spun yarn before subjecting same to said
free relaxation. 17. A method according to claim 15 and further
comprising mixing said spun yarn with additional textile materials
to convert same to a mixed state in the form of a covered yarn
before subjecting same to said
free relaxation. 18. A method according to claim 15 and further
comprising mixing said spun yarn with additional textile materials
to convert same to a mixed state in the form of a fabric before
subjecting same to said free relaxation.
Description
The present invention relates to a spun yarn of an elastic fiber
having excellent elastic elongation of more than 100 percent and a
quick recovery from stretching to an elongation which is less than
its breaking elongation, and a blended spun yarn of said elastic
fiber with any of the known hard fibers.
Spandex is the first synthetic elastomeric fiber industrially
utilized and is now used in the forms of bare yarn, covered yarn or
core-spun yarn. However, the spandex fibers actually employed in
these fields are all filament yarns, and no spandex spun yarn has
been developed up to now. Furthermore, most of the spandex filament
yarns used in these fields are of fine denier such as, for example,
140 d, 70 d and 40 d, and these fine-denier yarns are extremely
expensive thereby preventing expansion of the market therefor.
Accordingly, a principal object of the present invention is to
provide a cheap fine-denier spandex spun yarn. That is, the market
price of the coarser yarn of, for example, 3,000 d or 5,000 d is
less than about one third of the price of the above-mentioned finer
yarn, and the price difference between the two was more than 5
dollars per pound as of Aug., 1966. Therefore, if it were possible
to manufacture a finer yarn from this inexpensive coarser yarn with
a reasonable spinning cost of, for example, less than 1 dollar per
pound, it is beyond question that the market for spandex would be
greatly expanded.
The second object of the present invention is to provide single
covered spandex yarn or core-spun yarn having greatly reduced
kinking properties. A highly twisted spandex yarn tends to produce
kinking due to the high elasticity thereof. Therefore, in the
covered yarn field, spandex is always supplied in the form of
double covered yarn and no single covered yarn has been used. For
the same reason, in preparing core-spun yarn, a steaming treatment
has generally been used to prevent such kinking despite a lowering
of the excellent elasticity. To the contrary, the present spandex
spun yarn, used to cover yarn or core-spun yarn, is twisted in the
spinning process in a direction opposite that of the twists
thereafter given in the core-spinning or -covering process, so that
this counter twist reduces or makes negligible the kinking
properties of the core-spun yarn or single covered yarn under some
conditions of twist multiplication.
The third object of the present invention is to provide a blended
spun yarn of an elastic fiber and a hard fiber (natural or manmade
fiber) with an optional blending ratio. Hitherto, the content of
the elastic fiber in a blended spun yarn as far as has been
reported to date is limited on the order of less than 30 percent as
described in U.S. Pat. No. 3,007,227. Therefore, this novel blended
spun yarn having no limitation in the blending ratio of elastic
fiber affords a new kind of product and contributes towards rapid
development of new markets for spandex fiber.
The aforesaid and other objects will become apparent to those
skilled in the art from a consideration of the following
specification and claims. The principle of the method is to employ
a direct spinning system; i.e. a multifilament yarn or a tow of
elastic fiber becomes spun yarn through the consecutive steps of
breaking, drawing and twisting in one process.
In a conventional spinning system requiring a carding process such
as the cotton-spinning system, worsted spinning system, modified
system thereof, woolen spinning system etc., or in the conventional
spinning system or the tow to top converter system requiring the
drawing of thick slivers, it is impossible to make a pure spun yarn
of elastic fiber or blended spun yarn of elastic fiber with an
unlimited blending ratio for the following reasons. That is, in the
first place, since very pliant elastic fibers are apt to adhere to
the top end of the metallic wire, carding action is poor. In the
second place, in the drawing process or roving process comprising
drawing a sliver constructed of several thousands or several ten
thousands of fibers, it is difficult to pick up a single fiber out
of the sliver and to draw away each fiber relatively, because
frictional resistance between the pliant fibers is large and it
tends to cause stretching of fibers having an extremely small
Young' s modulus. Therefore, in these spinning systems, an elastic
fiber can be carded or drawn only in the case when it is blended
with a larger proportion of a hard fiber having a considerably high
Young' s modulus in order to make the elastic fiber move together
with said hard fiber. In other words, the spinning of the elastic
fiber is limited only to the case where the proportion of the
elastic fiber is considerably low. In this connection, U.S. Pat.
No. 3,007,227 describes as follows (In processing the fiber blends
on conventional textile machinery, it has been found more practical
to employ between 10 percent and 25 percent of the elastic fiber in
the blend, although special equipment may be selected to more
readily accommodate broader ranges of the elastic fibers. If the
proportion of the elastic fiber in the blend is raised,
sufficiently beyond 30 percent, fiber-processing operations into
yarn become more difficult to control and the resulting yarn and
fabric quality suffers: for example, when 50 percent elastic fiber
is used.)
A direct spinning system employed for the manufacture of the
present spun yarn of elastic fiber is described below while
illustrating the accompanying drawings.
FIG. 1 is a cross-sectional view of the direct spinning machine
which is conventional.
FIG. 2 is the correlation between the distance (ho) from back roll
to intermediate roll and draft ratio of the spandex spun yarn
prepared by using the apparatus as shown in FIG. 1.
FIG. 3 shows a part of a direct spinning machine equipped with a
pair of endless aprons and employed in the practice of this
invention.
FIG. 4 is a cross-sectional view of the direct spinning machine
particularly useful in the practice of this invention.
FIG. 5 is a staple diagram representing the correlation between
fiber length and content in the spun yarn of elastic fiber prepared
by using the apparatus shown in FIG. 4.
FIG. 6 is the correlation between the effective coefficient of
fiber strength in yarn strength and the fiber number in cross
section of yarn prepared by using elastic fiber (a) or hard fiber
(b).
In FIG. 1, multifilament yarn 2 released from bobbin 1 is fed, via
back roll 6, to a breaking zone A, and is stretch broken between
said back roll 6 and intermediate roll 7, the surface speed of the
roll 7 being 10 to 20 times faster than the speed of roll 6. Thus a
mass of broken and transformed fibers 3 is then sent to the
subsequent draft zone B, in which it is drawn to a desired denier
yarn between intermediate roll 7 and front roll 9 having a surface
speed several times faster than that of roll 7. The yarn 4 come out
of the front roll 9 and is passed through a pigtail 10, twisted to
a desired twisting condition by means of revolving spindle 12, and
wound up, via ring and traveller 11, on a cop as spun yarn 5. In
case the elastic fiber is blended with a hard fiber, roving 14 of
hard fiber is released from another bobbin 13, passed over a guide
roll 15, and fed to the intermediate roll 7 and blended therein
with the elastic fibers 3. In the other method, after passing over
the guide roll 15, said roving 14 of hard fiber is fed to cradle 8
and blended with the elastic fiber therein. Some of the
conventional direct spinning machines may possess a gear with edges
in the breaking zone A, or a floating control roll and a single
apron as a substitute for cradle 8 in the draft zone B. However,
the principal action of these modified machines on the fiber is the
same as that of the machine shown in FIG. 1. When the total denier
of elastic fibers in the draft zone is too coarse and therefore a
considerable high draft ratio is required to draw them to a desired
yarn denier, the already described difficulty of sliver drawing
also occurs here. Therefore, it is desirable to adjust the draft
ratio in the breaking zone so that the draft ratio in the
subsequent draft zone is less than 10, preferably less than 5.
Although spun yarn of elastic fiber can be prepared by using the
conventional direct spinning machine illustrated in FIG. 1, it is
difficult or impossible to obtain as good a quality yarn, as will
be obtained if the special pretreatment described hereinafter is
applied to the elastic fiber. It is most preferable to employ the
direct spinning machine equipped with a special apron apparatus
concerning the present invention as shown in FIG. 4.
The first reason why it is difficult to obtain a good quality yarn
with the machine shown in FIG. 1 is as follows: Compared with hard
fiber having smaller breaking elongation and poor recovery from
stretching, the elastic fiber used for the preparation of the
present spun yarn possesses at least 100 percent breaking
elongation and quick recovery from stretching to an elongation
which is less than its breaking elongation. In order to obtain spun
yarn having excellent elasticity using the elastic fiber and to
prevent yarn breaking strength from being reduced by slipping
between fibers in the yarn, it is necessary to employ a fiber of at
least 0.5 inch minimum length, more than 1 inch average length and
3 inches as the preferable average length. When the average length
of the fiber exceeds 4 inches and the total denier of the fiber is
coarse, the drawing operation in the draft zone is quite difficult
to carry out. Since the breaking elongation of spandex fiber, for
example, is in general in a range of 400 --800 percent, the broken
length of the fiber will be about 20 inches (3 inches .times.(5
-9)), taking the fiber length under no load as 3 inches. In this
connection, the distance (gauge length) between the back roll 6 and
the intermediate roll 7 will be determined by using the following
equation: L / ho=D log D-1 / e D (1+.epsilon.) wherein D is draft
ratio; ho stands for distance between back roll and intermediate
roll; .epsilon. means the breaking elongation of elastic fiber and
L is the stretched fiber length which has been forwarded by the
intermediate roll until it is broken. Taking the conditions of
.epsilon.=6 and L =20 inches, the correlation between ho and D is
shown in FIG. 2. (Correctly speaking, L plus one-half of ho should
be 20 inches, but for the sake of simple calculation L is taken as
20 inches.) According to this FIG. 2, even a large draft ratio of
20 gives only a narrow roll distance of about 2.6 inches in case of
3 inch fiber length. If the average free length of the fiber is
less than 2 inches, this roll distance will be much smaller than
that of the above case. Therefore, in the direct spinning system
shown in FIG. 1, approximately 1,000 ends of fibers must be
distributed in relatively a small zone. As already described, the
elastic fiber possesses a large frictional resistance acting
between fibers, so that an end of a fiber tends to be forwarded
with the movement of the end of another fiber thereby causing a
number of ends to be simultaneously caught by the intermediate
roll, and stretched and broken in the breaking zone. That is, an
evenly spun yarn can not be obtained in this method. Indeed, the
above may be avoided by further widening the roll distance to give
a considerably larger distribution of fiber ends, but it may also
result in the necessity of employing a longer fiber length, (e.g.
providing ho =4 and D =20, free fiber length should be 4 inches as
shown in FIG. 2), which in turn causes a different problem in the
draft zone as previously stated.
Therefore, one solution concerning the present invention for
obtaining a better quality yarn with the direct spinning machine as
shown in FIG. 1 is to subject the elastic fiber to a heat-setting
treatment prior to feeding it into said machinery. That is, the
elastic fiber is heat set in a stretched state to reduce its
breaking elongation and increase its Young' s modulus. For example,
if the elastic fiber is previously modified to have 200 percent of
breaking elongation, a fiber having a 3 inch free length should be
broken at a stretched fiber length of 9 inches (3 inches .times.3).
In this case, from the above said equation, ho will be 4.1 inches
when D is 20. This condition means a good distribution of fiber
ends. Furthermore, a longer free fiber length such as 4 inches can
be successfully employed, because the fiber is of high Young's
modulus, so that little trouble is found in the drawing step in the
draft zone. In this case, ho is 5.4 inches, so that it gives a
quite favorable distribution of fiber ends. Spun yarn thus prepared
from the pretreated fiber possesses a high Young' s modulus and low
breaking elongation. However, this spun yarn may conveniently be
converted to the state in which it has the original properties as
possessed by the unmodified elastic fiber, by subjecting the yarn
to a relaxation treatment under free loading conditions (for
example, in skein or in the form of woven fabric or knitted fabric)
in boiling water or a steam box. This recovery may be somewhat
influenced by the stretching ratio and heating temperature employed
in the pretreatment, but almost complete recovery can be obtained.
Some of the testing results in case of spandex fiber is shown in
the following table 1. ##SPC1## Remark: Young 's modulus shows the
value of tension gram in 250 percent extension of 530 d spandex
multifilament yarn.
The second reason why a good quality spun yarn is hard to obtain by
the direct spinning machine as shown in FIG. 1 is hereinunder
described.
The elastic fiber employed in the present invention possesses a
quick recovering property from various degrees of stretching, so
that the fiber ends broken in the stretch-breaking zone spring back
to form hook ends. This hook not only obstructs the even drawing of
the fiber, but also often gets entangled with adjacent fibers to
obstruct its movement as a single fiber, and cause many fibers to
be stretched and broken simultaneously. In this case, as shown in
FIG. 3, it is preferable to employ a pair of endless aprons placed
between the back roll and the intermediate roll and driven with a
speed which is faster than the surface speed of the back roll and
slower that the surface speed of the intermediate roll, to prevent
the spring back of broken fiber ends and, to reform the hook of
fiber end therewith if such occurs.
In order to obtain the best quality spun yarn of elastic fiber, it
is recommended to employ the direct spinning machine as shown in
FIG. 4. In this figure, the area between back roll 29 and
intermediate roll 31 is the stretch-breaking zone A, and the area
between the intermediate roll 31 and front roll 38 is the draft
zone B. Multifilament yarn 22 of elastic fiber is released from
bobbin 21 passed through back roll 29, and introduced via each
tensor 30 into the clearance between top apron 33 and bottom apron
35, these aprons being driven by intermediate roll 31 rotating with
a surface speed several times faster than that of back roll 29. The
elastic fiber having a large breaking elongation is thus stretched
by means of faster moving aprons 33 and 35. The clearance between
the tensors 30 (top and bottom) and the spring for the press roll
34 are adjusted so as to give slipping to the stretched fiber
before breaking. The stretched elastic fiber is further advanced
while slipping to the intermediate roll 31, where it is nipped by
the roll 31, stretched in a desired draft ratio and broken. After
passing through the roll 31, the stretch-broken elastic fiber
immediately shrinks by its own elasticity to a predetermined free
fiber length, and the thus obtained fiber 24 is, while being
carried on the bottom apron 35, sent to cradle roll 36 and drawn in
a desired denier yarn 25 in the draft zone provided between the
cradle roll 36 and front roll 38. This yarn 25 is then passed
through pigtail 39, twisted by revolution of the spindle, and
wound, via ring and traveller 40, on cop 41 as a spun yarn 26. As
clearly known from the above, the elastic fiber in the
stretch-breaking zone is stretched fully by a pair of faster moving
apron means and fed to the intermediate roll 31 as it is.
Therefore, the fiber length being forwarded by the intermediate
roll before the fiber is brought to its breaking elongation, is
considerably small and almost the same with that of hard fiber.
Consequently, it is possible to select and fix the distance between
the back roll and intermediate roll in a considerable size.
Furthermore, by controlling the spring pressure of press roll 34
and the clearance between the top and the bottom tensors 30, it is
possible to change the extent of stretch and the position of
slipping of the fiber placed between the aprons. Therefore, the
breaking point can be concentrated in a desired position or
distributed throughout the apron, and the fiber length can be
controlled in any desired size desired. These are exemplified in
FIG. 5. When the elastic fiber is stretch broken in such a way, the
spring back of the fiber end can be effectively controlled by the
top and bottom aprons, so that no troubles are involved in this
regard as compared with the case using the machinery as shown in
FIG. 1. Thus, a better quality yarn can be spun in accordance with
this invention.
When it is required to prepare a blended spun yarn of elastic fiber
and hard fiber, the same apparatus as shown in FIG. 4 is
conveniently employed with a slight modification thereon. That is,
another roving 43 consisting of hard fiber alone is released from
another bobbin 42, passed over guide roll 44 and blended with
elastic fiber 24 at the cradle roll 36. For convenience in varying
the blend ratio or yarn count, it is possible to place roll 45 in a
position between the guide roll 44 and the cradle roll 36 so that
the hard fiber roving is drawn by the surface speed difference
between the roll 45 and the cradle roll 36. However, since it is
difficult to place some apparatus for controlling floating short
fibers in the roving in the position between the cradle roll 36 and
the roll 45, the draft ratio in this area must not exceed 5, the
preferable draft ratio being 1 to 3.
In this type of blending system, mixing of each fiber is in general
no so good. However, the spun yarn has an elasticity and these
characteristic properties are brought by the elastic fiber
employed. Therefore, the elastic fiber apt to be concentrated in
the center of the yarn and the hard fiber will be distributed at
the periphery, and thus complete mixing of the fibers is
unnecessary in this case.
When it is required to give high elasticity to the blended spun
yarn, this may be accomplished by adjusting the clearance between
the top and the bottom tensors 37 of the cradle in the draft zone
B, such that the elastic fiber can be nipped (however, slippable on
the brink of breaking) and the hard fiber can be slipped
therebetween. Thus, by adjusting the clearance between tensors, any
elastic spun yarn having 0 to more than 100 percent of elasticity
may be prepared at will.
As will be clearly understood, the present spun yarn of elastic
fiber can be easily prepared by using the methods and the apparatus
described hereinabove.
The present spun yarn of elastic fiber is a distinctive product and
differs from any of the known spun yarns of hard fibers. The
following are the reasons therefor.
Firstly, spun yarn containing 30 to 100 percent, by weight, of
elastic fiber having more than 100 percent elastic elongation,
extremely small Young' s modulus and excellent quick recovery from
various degrees of stretching to an elongation less than its
breaking elongation, has never been prepared, though filament yarn
of elastic fiber has been heretofore known. As mentioned above, the
present spun yarn of elastic fiber is hardly prepared or cannot be
prepared at all by merely using a conventional spinning system, and
in order to obtain a better quality spun yarn it is necessary to
modify the elastic fiber beforehand by giving a special heat-set
treatment thereto or to employ a modified direct spinning system
equipped with a certain device. That is, in case of hard fiber, its
spun yarn is obtained as a matter of course by using any
conventional spinning system or conventional direct spinning
system, so far as its filament yarn exits. However, in the case of
an elastic fiber, it is not the same as that in the case of hard
fiber to obtain its spun yarn, even if its filament yarn
exists.
Secondly, since elastic fiber possesses an extremely small Young' s
modulus, each fibers in the twisted spun yarn sticks to one another
to cause a considerable frictional resistance between the fibers,
and therefore when such a spun yarn is stretched, there hardly
occurs any slipping between the fibers. To the contrary, in case of
a hard fiber, in order to maintain a satisfactory yarn tensile
breaking strength, spun yarn must be comprised of more than 50 ends
of fibers. If the fiber number in cross section of the yarn is less
than 50 ends, the said yarn strength abruptly decreases due to
slippage between the fibers. Therefore, even thinking over fiber
length, fiber denier, and twist multiplier, 30 ends are the minimum
limit for practical use. Furthermore, even if the spun yarn of hard
fiber possesses a satisfactory tensile strength under the best of
conditions, it cannot be free from the slipping at the time of
breaking the fiber. Therefore, it is impossible to bring the
effective coefficient of fiber strength in yarn strength (i.e. yarn
tensile strength/single fiber strength .times. fiber number in
cross section of yarn) to 100 percent, the mean value being 50 to
60 percent and the maximum value being 70 percent. Contrary to the
above, in the spun yarn of elastic fiber, no decrease in the yarn
strength is detected for the above-said reasons even in a product
having 15 fiber ends in cross section of spun yarn, and the
effective coefficient of fiber strength in yarn strength is almost
100 percent. In this regard, the correlation between the effective
coefficient and the fiber number in cross section of yarn is shown
in FIG. 6, wherein, (a) represents the curve for elastic fiber and
the (b) the curve for hard fiber. From these curves, it will be
seen that the minimum fiber number in cross section of the present
spun yarn is to maintain the yarn strength is quite different from
the corresponding value of the conventional hard spun yarn, and
that the maximum effective coefficients are quite different from
each other.
Thirdly, when fibers are stretch broken in a direct spinning
system, there is a big difference between elastic fiber and hard
fiber in their respective stretch-breaking phenomenon. That is, in
case of hard fiber, though the maximum fiber length may be
controlled by using a particular breaker, it is impossible to
prevent the occurrence of short fibers, the minimum fiber length
thereof being about several mm., for the following reasons. They
are the facts that the breaking of the fiber occurs throughout the
breaking zone, and since the breaking elongation (.epsilon., in the
aforesaid equation) of hard fiber is less than 0.4, in general
0.2--0.3, the L value becomes almost zero. On the contrary, in the
case of elastic fibers, the breaking elongation of the fiber is in
general 400--800 percent and therefore .epsilon. is in a range
between 4 and 8 and L can be a considerably larger value. Thus, in
the present spun yarn of elastic fiber, the minimum fiber length is
quite long as compared with the case of hard fiber and the short
fiber content is extremely small as a result.
The following examples will serve to illustrate the spun yarn of
elastic fiber, preparation thereof and the useful effects obtained
in this invention.
EXAMPLE 1
Employing multifilament yarn (5,000 d/ 500 fil.) of spandex elastic
fiber having 300 percent breaking elongation, 0.2 g/d Young' s
modulus (stress in 100 percent extension), and 98 percent recovery
from 100 percent extension, pure spandex spun yarn of 400 d having
40 ends of fiber in cross section was obtained by using the direct
spinning machine as shown in FIG. 4, under the following
conditions.
Stretch-breaking zone
draft ratio 10
distance between back roll and intermediate roll 9 inch
Draft zone
draft ratio 1.2
Twist `26 T/inch Employing the same conditions as stated above,
except that the draft ratio in the draft zone is increased to 3.4,
another pure spandex spun yarn of 150 d having 15 ends of fiber,
and 31 T/inch was prepared. Mechanical properties of these spun
yarns are shown in table 2. ##SPC2##
As clearly seen from the above table 2, the breaking elongation of
spun yarn after spinning decreased and the Young' s modulus
slightly increased compared with that of multifilament yarn,
because the elastic fiber is subjected to the stretch-breaking
treatment. However, by the after boiling treatment, such as dyeing,
the inner structural strain of the fiber was removed and the said
breaking elongation and Young' s modulus were restored to the
normal conditions. However, the Young' s modulus of the thus
after-treated yarn was slightly lowered compared to that of the
original material filament yarn. It might be due to the twists in
the finished spun yarn. Even in the spun yarn constructed with 15
ends of fibers, the breaking strength (g / d) was almost identical
with that of material filament yarn. Thus, the effective
coefficient of fiber length in yarn strength was 100 percent.
EXAMPLE 2
Pure spandex spun yarn (400 d, 26 T/inch S twist) prepared by the
method of example 1, was employed as a core yarn and acrylic fiber
roving (fiber denier 2 d , fiber length 2 inches) was used as a
sheath fiber. Stretching the core yarn with a draft ratio of 2,
core-spinning was carried out. Thus obtained core-spun yarn
possessed 49 percent of elastic fiber content, 22 Nm (metric count)
of yarn count (i.e. corresponding to 410 d) , and 12.2 T/inch of Z
twist. Since the twist direction of pure spandex spun yarn was S
while the twist direction of core spinning was Z, twisting torques
of the yarn disappeared. The kink number of the thus prepared
core-spun yarn was 26 and this product was found to be useful for
the following knitting or weaving process. For the sake of
comparison, similar core spinning was carried out with nontwist
filament yarn (210 d ) of elastic fiber and acrylic fiber roving,
and consequently the kink number of core-spun yarn obtained was 52.
This core-spun yarn had to be steam set to decrease the kink number
to 20 for the subsequent process.
EXAMPLE 3
Employing the direct spinning machine shown in FIG. 4,
multifilament yarn (5,000 d / 500 fil.) of spandex elastic fiber
having 300 percent breaking elongation, 0.2 g / d (stress in 100
percent extension) Young' s modulus, and 98 percent recovery from
100 percent extension, was stretch broken in the stretch-breaking
zone with the conditions of 7.45 draft ratio and 9 inches distance
between the back roll and intermediate roll. Another roving
consisting of 2 d fiber denier, 2 inches fiber length acrylic fiber
and having 0.1 g/m sliver weight, was continuously fed to cradle
roll in the draft zone, and blended with the elastic fiber come out
from the stretch-breaking zone. Then the blended yarn is drawn with
a draft ratio of 2.24 to give a desired yarn count of one
thirteenth Nm (metric count), twisted (23 twist/inch) by revolution
of spindle and wound up on a cop. The breaking strength and the
breaking elongation of this product were 683 g and 107 percent,
respectively. After subjecting to free relaxation in boiling water,
these values changed to 558 g and 277 percent. The spun yarn
obtained by this example comprised 43 percent spandex fiber and the
remaining percent hard fiber. Excellent elasticity and good
recovery from stretching were found on the spun yarn (after
spinning) within the limit of 50 percent extension and on the
relaxed spun yarn (after relaxation in boiling water) within the
limit of 150 percent extension, respectively.
The term "elastic fiber" used herein refers to the synthetic fiber
having elasticity due to construction with soft segment and hard
segment such as spandex fiber having urethan group as a bonding
group or the fiber having urea group or acid amide group as a
bonding group, and includes fibers formed by extruding or cutting
natural rubber synthetic rubber. Therefore, this elastic fiber has
the following characteristic mechanical properties.
breaking elongation more than 100 percent (generally 400--800
percent) elastic recovery from
high stretching more than 90 percent (generally more than 95
percent)
Young' s modulus less than 0.5 g/d (generally 0.03 --0.1 g/d
wherein the elastic recovery from high stretching is indicated by
the percentage of recovered stretch to the net stretched length of
the fiber just after being stretched to one-half of breaking
elongation thereof, kept it for one minute, and then released from
stretching and the Young' s modulus represents the stress when the
fiber is 100 percent extended.
The term "hard fiber" used herein refers to fibers having less than
50 percent breaking elongation, and including natural fiber such as
cotton, wool, linen, jute and silk, regenerated cellulosic fiber
such as viscose, cuprammonium, and acetate, and synthetic fiber
consisting of homopolymers such as polyamide, polyacrylonitril,
polyester, polyvinylchloride, and polyvinylalcohol or consisting of
copolymers thereof.
The present invention has been described in detail with particular
reference to preferred embodiments thereof, but it will be
understood that variations and modifications can be effected within
the spirit and scope of the invention as described hereinabove and
as defined in the appended claims.
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