U.S. patent application number 17/269010 was filed with the patent office on 2021-10-21 for acrylic yarn package.
The applicant listed for this patent is Toray Industries, Inc.. Invention is credited to Takashi Kawamoto, Tetsuya Murakami, Fumito Oshima.
Application Number | 20210323786 17/269010 |
Document ID | / |
Family ID | 1000005736172 |
Filed Date | 2021-10-21 |
United States Patent
Application |
20210323786 |
Kind Code |
A1 |
Oshima; Fumito ; et
al. |
October 21, 2021 |
ACRYLIC YARN PACKAGE
Abstract
An acrylic yarn package prevents winding yarn collapse during
transportation when an acrylic yarn having a high total fineness is
wound around a core bobbin. The acrylic yarn package includes an
acrylic yarn wound around a bobbin and having a total fineness of
8000 dtex or more. The acrylic yarn on the package has a yarn width
of 0.22 mm/1000 dtex or more and hardness of 60 or more.
Inventors: |
Oshima; Fumito; (lyo-gun,
Ehime, JP) ; Kawamoto; Takashi; (lyo-gun, Ehime,
JP) ; Murakami; Tetsuya; (lyo-gun, Ehime,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Toray Industries, Inc. |
Tokyo |
|
JP |
|
|
Family ID: |
1000005736172 |
Appl. No.: |
17/269010 |
Filed: |
August 20, 2019 |
PCT Filed: |
August 20, 2019 |
PCT NO: |
PCT/JP2019/032407 |
371 Date: |
February 17, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B65H 55/00 20130101;
B65H 2701/313 20130101 |
International
Class: |
B65H 55/00 20060101
B65H055/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 29, 2018 |
JP |
2018-160115 |
Claims
1-4. (canceled)
5. An acrylic yarn package comprising an acrylic yarn wound around
a bobbin and having a total fineness of 8000 dtex or more, wherein
the acrylic yarn on the package has a yarn width of 0.22 mm/1000
dtex or more and hardness of 60 or more.
6. The acrylic yarn package according to claim 5, wherein a total
amount of the acrylic yarn is 120 kg or more.
7. The acrylic yarn package according to claim 5, wherein the
acrylic yarn has a coefficient of static friction of 0.13 or
more.
8. The acrylic yarn package according to claim 5, wherein the
acrylic yarn on the package has a yarn width of 0.22 to 0.54
mm/1000 dtex, a yarn shift ratio of 15 to 59%, and a taper angle of
6 to 14.degree..
9. The acrylic yarn package according to claim 6, wherein the
acrylic yarn has a coefficient of static friction of 0.13 or
more.
10. The acrylic yarn package according to claim 6, wherein the
acrylic yarn on the package has a yarn width of 0.22 to 0.54
mm/1000 dtex, a yarn shift ratio of 15 to 59%, and a taper angle of
6 to 14.degree..
11. The acrylic yarn package according to claim 7, wherein the
acrylic yarn on the package has a yarn width of 0.22 to 0.54
mm/1000 dtex, a yarn shift ratio of 15 to 59%, and a taper angle of
6 to 14.degree..
12. The acrylic yarn package according to claim 9, wherein the
acrylic yarn on the package has a yarn width of 0.22 to 0.54
mm/1000 dtex, a yarn shift ratio of 15 to 59%, and a taper angle of
6 to 14.degree..
Description
TECHNICAL FIELD
[0001] This disclosure relates to an acrylic yarn package, and an
acrylic yarn package having a good package shape and less troubles
during transportation and unwinding. In particular, the package is
suitable as an acrylic precursor yarn package used for production
of carbon fibers.
BACKGROUND
[0002] Polyacrylonitrile long fibers have been used not only as
clothing but also precursors of carbon fibers in recent years, and
many improvement techniques have been disclosed to obtain carbon
fibers having excellent performance and increase their
productivity.
[0003] The carbon fibers are obtained by winding an acrylonitrile
fiber yarn as a precursor once in a yarn-making process of spinning
the acrylonitrile fiber yarn, and then sending the acrylonitrile
fiber yarn to a carbonization process in which the fiber is heated
in an air atmosphere at 200 to 300.degree. C. to convert the fiber
into an oxidized fiber (oxidation process), and the oxidized fiber
is further heated to 300 to 3000.degree. C. in an inert atmosphere
such as nitrogen, argon, or helium to convert the oxidized fiber
into a carbon fiber (carbonizing process). The carbon fibers are
widely utilized as reinforcing fibers for composite materials in
aerospace applications, sports applications, and general industrial
applications and the like.
[0004] The carbon fiber generally includes a multifilament composed
of filaments having 1000 or more monofilaments as one yarn unit,
but because of a difference in production yarn speed between a
yarn-making process and a carbonization process as a subsequent
process, an acrylic yarn as a raw material is generally wound once
in the yarn-making process, and then sent to the carbonization
process. To increase productivity in the carbonization process, it
is effective to increase the amount of an acrylic yarn that can be
processed per one time. However, the acrylic yarn is usually wound
around a core bobbin so that, if a large amount of yarn is wound
around one bobbin, the bobbin may sag in a vertical direction
during transportation of the bobbin to the carbonization process,
or bulge in side surfaces may increase, to result in winding yarn
collapse causing unwinding failure in the carbonization
process.
[0005] Japanese Patent Laid-open Publication No. 11-263534
describes a technique for defining winding conditions such as a
taper angle and winding tension in an acrylic yarn package for
precursors of carbon fibers to obtain a good package shape during
winding. However, JP '534 describes no winding yarn collapse during
transportation. Japanese Patent Laid-open Publication No. 2002-3081
describes a technique for obtaining a good package shape by taking
a specific yarn width and yarn shift ratio for a thick acrylic yarn
of 33000 dtex or more. However, unless moisture is applied to the
yarn before winding to improve the bundling property, deterioration
in the package shape and trouble during unwinding cannot be
completely prevented. This causes a problem that winding yarn
collapse occurs even during transportation. Because of the
application of moisture, the technique has the problem that the
running cost increases and it is not suitable for long-distance
movement due to an increase in mass.
[0006] Furthermore, Japanese Patent Laid-open Publication Nos.
Sho51-23322 and 2005-273106 describe techniques for defining the
hardness of a package for fibers having a total fineness of several
tens to several hundreds dtex to prevent winding yarn collapse
during transportation. However, those techniques cannot be directly
applied to an acrylic yarn package for precursors of carbon fibers
having a high total fineness exceeding 1000 dtex.
[0007] It could therefore be helpful to provide an acrylic yarn
package that prevents winding yarn collapse during transportation
when an acrylic yarn having a high total fineness is wound around a
core bobbin.
SUMMARY
[0008] We thus provide an acrylic yarn package including an acrylic
yarn wound around a bobbin and having a total fineness of 8000 dtex
or more, wherein the acrylic yarn on the package has a yarn width
of 0.22 mm/1000 dtex or more and hardness of 60 or more.
[0009] Our acrylic yarn package has a good package shape and
prevents collapse during transportation of an acrylic yarn package
having a high total fineness to a next process when the acrylic
yarn is wound around a core bobbin.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic view showing an acrylic yarn
package.
[0011] FIG. 2 is a schematic view showing an acrylic yarn package
having warpage occurring in its center.
DESCRIPTION OF REFERENCE SIGNS
[0012] 1: Acrylic yarn package [0013] 2: Core bobbin [0014] 3:
Acrylic yarn [0015] 4: Acrylic yarn [0016] 5: Straight line
connecting both ends of upper part of package [0017] 6: Curve
following upper part of package [0018] L: Yarn traverse width
[0019] k1, k2: Bulge length in side surfaces [0020] S: Yarn shift
length [0021] T: Yarn width [0022] U: Warpage [0023] .theta.: Taper
angle [0024] .alpha.: Line perpendicular to core bobbin axis
direction
DETAILED DESCRIPTION
[0025] We considered the problems associated with a carbon fiber
precursor acrylic thick yarn package having a good package shape
without collapsing even during transportation when an acrylic yarn
having a high total fineness is wound around a core bobbin as the
above problems, and discovered that improvements are possible by
setting the yarn width and hardness of the package to a certain
level or higher.
[0026] The carbon fiber precursor acrylic yarn is composed of a
so-called acrylic polymer, for example, preferably a polymer
obtained by polymerizing 90% by mass or more of acrylicnitrile and
less than 10% by mass of a comonomer. Examples of the comonomer
include at least one selected from acrylic acid, methacrylic acid,
itaconic acid, and methyl ester, ethyl ester, propyl ester, and
butyl ester of these acids; alkali metal salt, ammonium salt, or
allyl sulfonic acid, methallyl sulfonic acid, alkali metal salts
thereof and the like.
[0027] Such an acrylic polymer can be obtained by using a known
polymerization method, for example, a polymerization method such as
emulsion polymerization, suspension polymerization, or solution
polymerization. When an acrylic fiber is produced from these
polymers, a polymer solution containing a solvent selected from,
for example, dimethyl acetamide, dimethyl sulfoxide (DMSO),
dimethylformamide, aqueous solutions of nitric acid, zinc chloride,
and sodium rhodanide is used as a spinning raw yarn, and spinning
is performed by a wet spinning method or a dry spinning method.
[0028] The spun yarn is then subjected to bath draw, but the
spun-out yarn may be directly subjected to the bath draw, or the
spun-out yarn may be washed with water once to remove the solvent,
followed by subjecting the spun yarn to the bath draw. In such a
bath draw, the spun yarn is preferably drawn about 2 to 6 times in
a drawing bath at 50 to 98.degree. C. After drawing, an oil agent
is preferably applied to the spun yarn, and the spun yarn is
subjected to drying and densification with a hot roller or the
like. Then, the spun yarn is subjected to steam drawing, and then
wound around a core bobbin to form a package.
[0029] When such a package is formed, a plurality of yarns may be
combined, and then wound. It is effective to carbonize
multifilament yarns at one time to improve productivity of carbon
fibers. Therefore, the total fineness of the wound yarn is 8000
dtex or more. The moisture percentage of the yarn is preferably 3%
or less to avoid an increase in mass during transportation. The
total amount of the acrylic yarn obtained by subtracting bobbin
mass and the amount of moisture from the mass of the entire package
is preferably large, preferably 120 kg or more, and more preferably
200 kg or more to reduce the set number of the acrylic yarn in a
carbonization process to improve efficiency.
[0030] It is important that the hardness of a bobbin end measured
by a durometer is 60 or more to eliminate winding yarn collapse
during transportation. If the hardness is less than 60, the package
is apt to loosen, which can cause winding yarn collapse during
transportation and yarn drop during unwinding to occur. The
hardness of 60 or more can be achieved by setting the tension of
the yarn during winding to an appropriate value. A large amount of
yarn is commonly wound while a large tension is gradually
attenuated, but the value may be an appropriate value depending on
the fineness of the yarn and the number of filaments.
[0031] It is necessary to wind the acrylic yarn on the package with
the yarn width of the acrylic yarn set to 0.22 mm/1000 dtex or
more. If the yarn width is smaller than 0.22 mm/1000 dtex, the
thickness of the yarn becomes large so that a gap causing yarn slip
occurs between a yarn and another yarn adjacent to the yarn, which
can cause winding yarn collapse during transportation. If the yarn
width is more than 0.54 mm/1000 dtex, the yarn convergency
deteriorates, which may cause trouble such as yarn drop and
monofilament wrapping to occur during unwinding in the
carbonization process, whereby the yarn width of the acrylic yarn
on the package is preferably 0.22 mm to 0.54 mm/1000 dtex. The
method of setting the yarn width on the package within the above
range is not particularly limited, but when the yarn is wound with
a winder, a method of winding the yarn after causing a group of
free rollers for bundling to pass at a certain level or more is
suitably used.
[0032] When the coefficient of static friction between the acrylic
yarns is less than 0.13, a bulge in side surfaces may occur during
winding even if the yarn width and the hardness are controlled to
specific conditions to prevent the winding yarn collapse.
Therefore, the coefficient of static friction is preferably 0.13 or
more by applying an appropriate type and amount of an oil
agent.
[0033] It is preferable to set a yarn shift ratio to 15 to 59% and
a taper angle on the package to 6 to 14.degree.. The yarn shift
ratio is a ratio of a yarn shift length S to a yarn width T in two
yarns passing through the closest points on the package in
parallel. That is, this yarn shift ratio is obtained by
(S/T).times.100 shown in FIG. 1. This will be conceptually
described using FIG. 1. An acrylic yarn 4 is a yarn passing through
the closest point on an acrylic yarn package 1 in parallel to an
acrylic yarn 3. The yarn shift ratio is a ratio of the yarn shift
length S between the acrylic yarn 3 and the acrylic yarn 4 to the
yarn width T. The yarn width T and the yarn shift length S are
values measured by methods to be described later.
[0034] As shown in FIG. 1, the taper angle is an angle (A) between
a straight line perpendicular to the axis of a core bobbin 2 (line
.alpha. perpendicular to the axis direction of the core bobbin) and
the direction of the acrylic yarn 4 to be wound.
[0035] The yarn shift ratio and the taper angle can usually be
controlled by setting the number of revolutions of a winder spindle
per thread traverse, i.e., a so-called winding ratio to appropriate
values. If the winding ratio is an integer, the yarn passes through
the exactly same yarn passage before and after one traverse,
whereby the yarn passage before and after one traverse can be
shifted by setting the fractional portion of the winding ratio to
an appropriate value, to control the yarn shift ratio. The taper
angle can be controlled by setting the size of the entire winding
ratio including an integer portion to an appropriate value.
[0036] If the yarn shift ratio is less than 15%, the package has
large undulations. Even if a winding tension is increased, the
hardness may be decreased, which can cause the winding yarn
collapse to occur during transportation. When the yarn shift ratio
is more than 59%, a contact surface between an inner layer yarn and
an outer layer yarn is small so that the pressing of the outer
layer yarn during winding causes the inner layer yarn to slip, to
push out the inner layer yarn, which causes a bulge in side
surfaces. Therefore, the yarn shift ratio is 15% to 59%, whereby
both the hardness and the end face shape can have good values.
[0037] If the taper angle is less than 6.degree., the yarn drop
during unwinding is likely to occur. If the taper angle is more
than 14.degree., the bulge in side surfaces is large so that the
taper angle is preferably 6 to 14.degree.. When the yarn is wound
with a constant winding ratio, the taper angle linearly decreases
as the diameter of the package wound around the core bobbin
increases, whereby the yarn can be wound while the taper angle is
kept within a certain range by changing the winding ratio during
winding depending on the winding amount of the yarn. For example,
by providing a mechanism such that spindle drive and traverse drive
are made to be independent from each other, the number of
revolutions of the spindle is detected, calculation is performed to
provide the set winding ratio, and then the number of revolutions
of the traverse drive is controlled, the winding ratio can be
freely set depending on the wilding amount in the winding
process.
EXAMPLES
[0038] Hereinafter, our yarn packages will be described in detail
with reference to Examples and Comparative Examples. Measurement
methods used in Examples and Comparative Examples will be described
below.
Total Fineness
[0039] A sample yarn of 20 m was collected from a package to be
measured, and a total fineness was determined by a method according
to JIS L1013: 2010.
[0040] Coefficient of Static Friction
[0041] A sample yarn of 1.5 m was collected from a package to be
measured, and wrapped around the collected package. At this time,
the sample yarn was wound around the center of the package along
the circumferential surface of the package. After the sample yarn
was wound so that a contact angle with the package was 540.degree.,
a weight of 150 g was attached to each of both ends of the sample
yarn. Then, the mass of the weight on one end side of the yarn was
increased, and a mass of the weight when the yarn started to slip
on a package was measured. A coefficient of static friction was
calculated from the following formula:
Coefficient of static friction (.mu.s)=3/.pi..times.Ln(T1/150)
[0042] .pi.: Circumference ratio
[0043] T1: Mass of weight (g) when yarn starts to slip.
Yarn Width
[0044] Using a caliper, the yarn width of the acrylic yarn on the
package was measured at a total of five points of places within 2
cm from both ends of the package (both ends), a center of the
package, a place between one of both the ends and the center, and a
place between the other end and the center, and a value obtained by
dividing the measured value with the total fineness was taken as
the yarn width.
Yarn Shift Ratio
[0045] For two yarns passing through the closest points on the
package in parallel, a yarn shift length (S) shown in FIG. 1 was
measured at a total of five points of both ends of the package, a
center of the package, a place between one of both the ends and the
center, and a place between the other end and the center using a
caliper, and a value obtained by dividing the average value with
the yarn width was taken as the yarn shift ratio.
Taper Angle Range
[0046] While the wound package was subjected to unwinding, an angle
(.theta.) between a straight line (.alpha.) perpendicular to the
axial direction of a core bobbin 2 shown in FIG. 1 and the
direction of a yarn 4 to be wound was measured at the center of the
package every 10 kg until all the yarns were discharged, and the
range of the measured value was taken as a taper angle range.
Hardness
[0047] Using HARDNESS TESTER "Type C" (for Cellular Rubber &
Yarn Package) manufactured by KOBUNSHI KEIKI CO., LTD., values were
measured at two places within 2 cm from both ends of the package,
and the average value thereof was taken as the hardness of the yarn
package.
Winding Yarn Collapse during Transportation
[0048] An acrylic yarn package was set at a trolley with a spindle,
and one acrylic yarn package subjected to a transportation
vibration test according to JIS Z 0232: 2004 once to determine the
presence or absence of winding yarn collapse according to the
following two levels: Good: No increase of 5.0 mm or more of bulge
in side surfaces and no increase of 10 mm or more of warpage.
[0049] Poor: Increase of 5.0 mm or more of bulge in side surfaces
and increase of 10 mm or more of warpage.
[0050] A distance (U) between a straight line 5 connecting both
ends of an upper part of the package shown in FIG. 2 and the
farthest point on a curve 6 following the upper part of the package
was measured, and taken as warpage U.
Bulge in Side Surfaces
[0051] Bulge length in side surfaces (k1, k2), which was a height
of a point where a side surface of the package bulges on the
outermost side, with respect to a yarn traverse width (L) on the
outermost surface of the package, as shown in FIG. 1 was measured
on each of both the side surfaces of the package, and the average
value thereof was taken as bulge in side surfaces.
Trouble During Unwinding
[0052] When the package was set on a creel, and the entire amount
was subjected to unwinding, those that did not cause yarn drop or
monofilament wrapping were taken as good, and those that caused
yarn drop or monofilament wrapping were taken as poor.
Example 1
[0053] Using a 19% DMSO solution of an acrylic polymer having an
intrinsic viscosity [.eta.] of 1.80 and containing 99.6% by mass of
acrylonitrile and 0.4% by mass of itaconic acid as a raw spinning
solution, and a spinneret having 6000 pores, semi-wet spinning was
performed in a coagulation bath containing 30% of DMSO and 70% of
water at 8.degree. C. to obtain a coagulated yarn. The coagulated
yarn was drawn 2.8 times in hot water while being washed with
water. Furthermore, the remaining DMSO was washed with water until
the DMSO amount became 0.01% or less in the yarn, and a
silicone-based oil agent was then applied, followed by drying and
densification at 150 to 160.degree. C. Subsequently, the yarn was
drawn 4.3 times in pressurized steam, and then dried again. Two
6000-filament yarns were combined, and a 12000-filament yarn having
a total fineness of 13300 dtex was wound around an FRP core bobbin
having an outer diameter of 145 mm with a winder so that the total
amount of the acrylic yarn obtained by subtracting the bobbin mass
and the amount of moisture from the mass of the entire package was
120 kg in a yarn width, a yarn shift ratio, and a taper angle range
shown in Table 1. The amount of moisture was determined by
collecting a yarn of about 12 m to be wound in advance, measuring a
moisture percentage by a method according to JIS L1013: 2010, and
multiplying the moisture percentage by the amount of the wound
yarn.
[0054] As a result, as shown in Table 1, a good package which did
not cause winding yarn collapse during transportation was
provided.
Examples 2 to 5 and Comparative Examples 1 to 4
[0055] An acrylic yarn was wound in a yarn width, a yarn shift
ratio, and a taper angle range shown in Table 1 in the same manner
as in Example 1 except that the total weight of the acrylic yarn
obtained by subtracting a bobbin mass and an amount of moisture
from the mass of an entire package was set to 240 kg, and a yarn
width during winding, and a winding ratio and tension of a winder
were changed.
[0056] As a result, as shown in Table 1, Examples 2 to 5 provided a
good package that did not cause winding yarn collapse during
transportation, but Example 4 caused a high yarn shift ratio of 60%
or more during winding, to result in a small contact surface
between an inner layer yarn and an outer layer yarn so that the
outer layer yarn pressed the inner layer yarn during winding, and
the inner layer yarn slid and was pushed out, to result in a
package having a large bulge in side surfaces. Example 5 caused a
large yarn width of 0.55 mm/1000 dtex or more to result in poor
yarn convergency so that yarn drop and monofilament wrapping
occurred during unwinding in a carbonization process. Comparative
Examples 1 to 3 had hardness of less than 60 as compared to Example
2, and caused winding yarn collapse during transportation.
Comparative Example 4 had a yarn width of less than 0.22 mm/1000
dtex as compared to Example 2, and caused winding yarn collapse
during transportation.
Examples 6 and 7
[0057] A yarn was wound in a yarn width and a yarn shift ratio
shown in Table 1 in the same manner as in Example 2 except that the
amount of an oil agent deposited was adjusted to change the
coefficient of static friction of the yarn. As a result, as shown
in Table 1, a good package that did not cause winding yarn collapse
during transportation was provided. Example 6 had a low coefficient
of static friction of less than 0.13 and caused yarn lateral
sliding during winding, to result in a package having large bulge
in side surfaces.
Example 8
[0058] A 24000-filament yarn having a total fineness of 26600 dtex
was wound in a yarn width and a yarn shift ratio shown in Table 1
in the same manner as in Example 2 except that four 6000-filament
yarns were combined.
[0059] As a result, as shown in Table 1, a good package that did
not cause winding yarn collapse during transportation was
provided.
Example 9
[0060] A 24000-filament yarn having a total fineness of 29100 dtex
was wound in a yarn width and a yarn shift ratio shown in Table 1
in the same manner as in Example 8 except that a drawing ratio in
pressurized steam was 3.9.
[0061] As a result, as shown in Table 1, a good package that did
not cause winding yarn collapse during transportation was
provided.
Example 10
[0062] A 36000-filament yarn having a total fineness of 26600 dtex
was wound in a yarn width and a yarn shift ratio shown in Table 1
in the same manner as in Example 2 except that six 6000-filament
yarns having a monofilament fineness of 0.74 dtex were
combined.
[0063] As a result, as shown in Table 1, a good package that did
not cause winding yarn collapse during transportation was
provided.
TABLE-US-00001 TABLE 1-1 Coefficient Yarn Yarn Taper Total Winding
of static width shift angle fineness amount friction [min/ ratio
range Hardness [dtex] [kg] [-] 1000 dtex] [%] [.degree.] [-]
Example 1 13300 120 0.15 0.40 54 7 to 13 75 Example 2 13300 240
0.15 0.40 54 7 to 13 75 Example 3 13300 240 0.14 0.37 19 7 to 13 64
Example 4 13300 240 0.15 0.40 60 7 to 13 74 Example 5 13300 240
0.16 0.67 50 7 to 13 70 Example 6 13300 240 0.10 0.38 50 7 to 13 74
Example 7 13300 240 0.22 0.40 54 7 to 13 78 Example 8 26600 240
0.15 0.26 57 7 to 13 77 Example 9 29100 240 0.17 0.30 40 7 to 13 81
Example 10 26600 240 0.16 0.29 28 7 to 13 79 Comparative 13300 240
0.15 0.37 10 7 to 13 59 Example 1 Comparative 13300 240 0.15 0.40
54 3 to 16 55 Example 2 Comparative 13300 240 0.15 0.40 54 7 to 13
55 Example 3 Comparative 13300 240 0.16 0.21 50 7 to 13 65 Example
4
TABLE-US-00002 TABLE 1-2 Bulge in side surfaces Numerical Trouble
Winding yarn collapse during value during transportation [mm]
Determination unwinding Example 1 Good 14 Very good Good Example 2
Good 20 Good Good Example 3 Good 18 Good Good Example 4 Good 26
Poor Good Example 5 Good 24 Good Poor Example 6 Good 28 Poor Good
Example 7 Good 21 Good Good Example 8 Good 24 Good Good Example 9
Good 22 Good Good Example 10 Good 22 Good Good Comparative Poor 22
Good Good Example 1 Comparative Poor 29 Poor Poor Example 2
Comparative Poor 22 Good Good Example 3 Comparative Poor 23 Good
Good Example 4 No winding yarn collapse: good Less than 15 mm: very
good No trouble: good Winding yarn collapse: poor Less than 25 mm:
good Trouble: poor 25 mm or more: poor
* * * * *