U.S. patent application number 11/137319 was filed with the patent office on 2006-09-28 for poly(butylene terephthalate) sewing thread.
Invention is credited to Elke Gebauer, Frank Kauer, Frank Leimback, Joachim Mondl, Clemens Schomberg.
Application Number | 20060213176 11/137319 |
Document ID | / |
Family ID | 36973555 |
Filed Date | 2006-09-28 |
United States Patent
Application |
20060213176 |
Kind Code |
A1 |
Gebauer; Elke ; et
al. |
September 28, 2006 |
Poly(butylene terephthalate) sewing thread
Abstract
The present invention provides a sewing thread formed from
poly(butylene terephthale) multifilament yarns, the sewing thread
being characterized in that the sewing thread has an elastic
recovery at 20% elongation of greater than or equal to 60%, a
method of producing same, and the use of same. In the present
invention a PBT yarn designates a yarn composed of a polyester that
uses butylene terephthalate (tetramethylene terephthalate)
repeating units as principal repeating units and that contains the
butylene terephthalate repeating units in an amount of 50 mol-% or
more, preferably 70 mol-% or more, even more preferably by 90 mol-%
or more. The yarn made from PBT can contain a third component as an
other acid component and/or glycol components and or other
additives or colours in a total amount of 50 mol-% or less.
Inventors: |
Gebauer; Elke; (Bad
Hersfeld, DE) ; Schomberg; Clemens; (Bad Hersfeld,
DE) ; Mondl; Joachim; (Bad Hersfeld, DE) ;
Kauer; Frank; (Neuenstein, DE) ; Leimback; Frank;
(Bebra, DE) |
Correspondence
Address: |
DOUGHERTY, CLEMENTS, HOFER & BERNARD
1901 Roxborough Road, Suite 300
Charlotte
NC
28211
US
|
Family ID: |
36973555 |
Appl. No.: |
11/137319 |
Filed: |
May 25, 2005 |
Current U.S.
Class: |
57/243 |
Current CPC
Class: |
D02G 3/46 20130101 |
Class at
Publication: |
057/243 |
International
Class: |
D02G 3/02 20060101
D02G003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 22, 2005 |
DE |
10 2005 013 186.7 |
Claims
1. Sewing thread comprising one or more multifilament yarns,
wherein one or more of said multifilament yarns comprise(s)
poly(butylene terephthalate).
2. Sewing thread according to claim 1, wherein said poly(butylene
terephthalate) multifilament yarn is made of a polyester comprising
butylene terephthalate repeating units as principal repeating units
in an amount of 50 mol-% or more.
3. Sewing thread according to claim 2, wherein said polyester
comprises 70 mol-% or more butylene terephthalate.
4. Sewing thread according to claim 2, wherein said polyester
comprises 90 mol-% or more butylene terephthalate.
5. Sewing thread according to claim 2, wherein said polyester
comprises further repeat units from components selected from the
group containing aliphatic, alicyclic and aromatic dicarboxylic
acids, other than terephthalic acid; aliphatic, alicyclic and
polyether glycols, other than butylene glycol.
6. Sewing thread according to claim 1, wherein said poly(butylene
terephthalate) multifilament yarn comprises additives and/or
colours.
7. Sewing thread according to claim 1, wherein said multifilament
yarns are plied together.
8. Sewing thread according to claim 1, wherein said multifilament
yarns are false twisted or air textured.
9. Sewing thread according to claim 1, wherein said multifilament
yarns are sheathed with natural or synthetic fibres.
10. Sewing thread according to claim 1, wherein said multifilament
yarns are bonded together.
11. Sewing thread according to claim 1, wherein the sewing thread
has an elastic recovery from a 20% elongation of greater than or
equal 60% and an elongation at break of greater than or equal to
25%.
12. Sewing thread according to claim 1, wherein the sewing thread
has a breaking strength of from 20 to 50 cN/tex and an elongation
at break of from 25 to 100%.
13. A method of producing a plied sewing thread, comprising the
steps of: doubling and twisting multifilament yarns, whereby at
least one of the multifilament yarns is made from poly(butylene
terephthalate), having titer of greater than or equal 20 dtex to
give a doubled, tripled or quadrupled twisted thread, dyeing the
resultant thread, and coating the dyed thread with a sewing thread
lubricant and/or a smoothing agent and/or a binder or a mixture
thereof.
14. A method of producing a plied sewing thread, comprising the
steps of: twisting a multifilament yarn made from poly(butylene
terephthalate) and having titer of from 20 to 550 dtex to give from
200 to 1800 T/m in S-direction, jointly twisting two or three of
the resultant S-twisted yarns to give from 180 to 1600 T/m in
Z-direction, dyeing the resultant Z-twisted thread, and coating the
resultant dyed thread with a sewing thread lubricant and/or a
smoothing agent and/or a binder or a mixture thereof.
15. A method of producing a core spun sewing thread, wherein a
sheath of natural or synthetic fibers is wrapped around a
multifilament yarn made from poly(butylene terephthalate).
16. A method of producing an air-intermingled sewing thread,
comprising the steps of: feeding a first multifilament yarn made
from poly(butylene terephthalate) through an air texturing jet to
form a core yarn, and feeding a second multifilament yarn through
the same said air texturing jet at a higher overfeed than said core
yarn.
17. A method of producing a bonded sewing thread, comprising the
steps of: plying two or more multifilament yarns, whereby one or
more of said multifilament yarns are made from poly(butylene
terephthalate), and bonding them together with a polymeric
binder.
18. Use of poly(butylene terephthalate) for manufacturing at least
one multifilament yarn of a sewing thread.
19. Use of multifilament yarns made from poly(butylene
terephthalate) for manufacturing a plied, core-spun, intermingled
or bonded sewing thread.
20. Use of poly(butylene terephthalate) sewing thread according to
claim 13 for sewing seams in stretch fabrics.
Description
BACKGROUND
[0001] 1) Field of the Invention
[0002] The present invention relates to a poly(butylene
terephthalate) (PBT) sewing thread, and to sewn elastic articles
prepared using the PBT sewing thread.
[0003] 2) Prior Art
[0004] Sewing threads are known in various structures: a plied
sewing thread, a core yarn, an intermingled sewing thread, or a
bonded sewing thread.
[0005] EP 0 569 890 A discloses a plied sewing thread. This sewing
thread structure is a plied yarn, whereby this plied yarn has at
least two, though preferably three, multifilament yarn components.
Each yarn component constituting the plied yarn is likewise given
initial twisting prior to twisting, whereby the pre-twisting of
each multifilament yarn component with respect to its direction is
opposite to the direction of twisting.
[0006] EP 0 569 891 A discloses a core spun sewing thread. Here, a
multifilament first yarn component is spun over by a second yarn
component consisting of spun yarns from natural or synthetic
fibers.
[0007] EP 0 295 601 A describes a sewing thread consists of
multifilament synthetic fibers, having the structure of an
air-intermingled sewing thread, such that a multifilament first
core thread component is intermingled by means of an air stream
with a second effect thread component.
[0008] EP 0 919 649 A discloses a bonded sewing thread made of
synthetic multifilaments, whereby the sewing thread has at least
two yarn components, whereof the individual filaments are in each
case aligned parallel to one another. Both these yarn components
are twisted with one another, whereby to achieve the required
thread cover both yarn components twisted with one another over
their entire surface are provided with a polymer coating.
[0009] The above described known sewing threads are used only in a
limited way for sewing elastic articles. When a stretch fabric is
sewn with a sewing thread having no elasticity, the stretchability
of the fabric in the seamed portions is poor, and the full
advantage of the stretch fabric is not utilized. Moreover, when an
excessive force is applied to the seams of a sewn stretch fabric,
the fabric has a disadvantage that the sewing thread is easily
broken.
[0010] Accordingly, when elasticity is required in the seams, the
following has been practiced: the elasticity of the seams is
obtained by forming seams having a structure of a multi-thread
chain stitch, an overlock stitch or a zigzag stitch. However, these
seams have the following drawbacks: a special sewing machine is
required in order to form the structures; formation of the seams
requires much time; a large amount of a sewing thread is used; and
the seams have a poor appearance. Moreover, the elasticity of the
fabric in the seamed portions is often unsatisfactory.
[0011] Japanese Patent Publications (Kokai) No. 01-260030 and
02-026945 disclose the use of an elastic fiber, such as a
polyurethane based yarn, covered by a soluble yarn such as a
polyvinyl alcohol yarn as a elastic sewing thread. After the
stretch fabric is sewn, the soluble yarn is dissolved and
removed.
[0012] European Patent 1 188 852 A1 discloses a stretchable sewing
thread using poly(trimethylene terephthalate) (PTT). PTT has the
disadvantage that the melt spinning speeds need to be low (about
1,500 m/min) to prevent crystallization in the spun yarn, that
leads to unstable packages. In addition PTT sewing threads need to
be wound on a package with a specific low density and wet treated
at 90.degree. C. in order to obtain a uniform relaxed yarn that
does not shrink during the dyeing process and that gives a uniform
dyed sewing thread.
[0013] European Patent 1 479 802 A also discloses sewing threads
having good elasticity, again based on PTT.
SUMMARY OF THE INVENTION
[0014] An object of the present invention is to provide a
stretchable sewing thread suitable for forming a highly stretchable
lock stitch, and a sewn article prepared from a stretch fabric and
having seams with excellent appearance and elasticity.
[0015] An additional object is to provide a stretchable sewing
thread that does not have the problems associated with the prior
art solutions.
[0016] The present inventors have discovered that a sewing thread
containing at least one multifilament yarn made from poly(butylene
terephthalate) (PBT) provides high stretchability and enables
sewing of seams with excellent appearance and elasticity, that are
specifically well suited for stretch fabrics.
[0017] Furthermore, the present inventors have found that sewing
threads containing at least one multifilament yarn made from PBT
solve the problems mentioned above, and thus achieved the present
invention. That is, the present invention provides a sewing thread
comprising one or more multifilament yarns, wherein one or more of
the multifilament yarns comprise(s) poly(butylene
terephthalate).
[0018] Quite unexpectedly, the present inventors have found, that
although PBT multifilament yarns have a lower elastic recovery
compared to PTT multifilament yarns, the final dyed sewing threads
have comparable elastic recovery and seam elongations. Therefore,
the use of a PBT sewing thread is preferable to PTT sewing threads
since its elasticity is not reduced during the dyeing and finishing
steps of the sewing thread process.
[0019] In the broadest sense, the invention is directed to sewing
thread comprising one or more multifilament yarns, wherein one or
more of said multifilament yarns comprise(s) poly(butylene
terephthalate).
DETAILED DESCRIPTRION
[0020] In the present invention a PBT yarn designates a yarn
composed of a polyester that uses butylene terephthalate
(tetramethylene terephthalate) repeating units as principal
repeating units and that contains the butylene terephthalate
repeating units in an amount of 50 mol-% or more, preferably 70
mol-% or more, even more preferably by 90 mol-% or more. The yarn
made from PBT can contain a third component as an other acid
component and/or glycol components and or other additives or
colours in a total amount of 50 mol-% or less.
[0021] Poly(butylene terephthalate) is synthesized by reacting
terephthalic acid or its functional derivatives with butane diol in
the presence of a catalyst, usually titanium compounds under
suitable reactions conditions. In the course of the synthesis,
other diacids and diols may also be added to form a
copolyester.
[0022] Examples of the third components to be added include
aliphatic dicarboxylic acids such as oxalic acid and adipic acid,
alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid,
aromatic dicarboxylic acids such as isophthalic acid and sodium
sulfoisophthalate; aliphatic glycols such as ethylene glycol,
1,2-propylene glycol and tetramethylene glycol, alicyclic glycols
such as cyclohexanedimethanol, aliphatic glycols each having an
aromatic group such as 1,4-bis(.beta.-hydroxyethoxy)benzene,
polyether glycols such as polyethylene glycol and polypropylene
glycol, aliphatic oxycarboxylic acids such as (.omega.-oxycaproic
acid and aromatic oxycarboxylic acid such as p-oxybenzoic acid.
Moreover, a compound having one or three or more ester-forming
functional groups such as trimethylol propane or pentaeryrthritol
may also be employed so long as the resultant polymers are
substantially linear.
[0023] The poly(butylene terephthalate) yarn used in the present
invention is generally a yarn produced by melt spinning the
poly(butylene terephthalate) polymer. The PBT yarn may also be a
yarn produced by separately synthesising polyesters other than PBT
such as poly(trimethylene terephthalate) (PTT), poly(ethylene
terephthalate) (PET), polyamides and blending the polymers; the
yarns may also be produced by composite spinning (sheath core,
side-by-side).
[0024] The PBT yarn may contain delustering agents such as titanium
dioxide, stabilizing agents such as phosphoric acid,
ultraviolet-ray absorbers such as hydoxybenzophenone derivative,
flame retardants, antistatic agents, pigments, solvents,
fluorescent brighteners, nucleating agents, infrared-ray absorbers,
defoaming agents and the like and mixtures thereof.
[0025] The PBT yarn forming the sewing thread of the invention can
be obtained by any of the following methods: a method wherein the
PBT polymer is melt spun, the yarn is wound at a speed between 700
and 5000 m/min to give an undrawn yarn and the undrawn yarn is
drawn and twisted; a one step direct drawing method in which a
spinning step and a drawing step are combined; and a high speed
spinning method in which the winding speed is set at 5000 m/min or
more. The preferred process is spinning the yarn at speeds >1500
m/min and drawing and relaxing it at a ratio between 1.2 to 2.3 to
achieve the desired balance of physical properties.
[0026] The cross sectional shape of a filament forming the
multifilament yarn may be polygon-shaped, for example round shaped,
triangle-shaped, L-shaped, T-shaped, trilobal, Y-shaped, W-shaped,
eight-leaf-shaped, flat shaped, dog-bone-shaped, multi-leaf-shaped,
hollow hole-shaped, and indefinitely shaped. Of these
cross-sectional shapes, a round-shaped cross section is
particularly preferred.
[0027] The filamentary yarn can be a flat drawn yarn that is
obtained by any one of the above various spinning and drawing
methods, a false twisted yarn (including a draw textured yarn from
PBT partially oriented yarn, (POY) a twisted false twisted yarn
(for example, a yarn obtained by twisting in the S or Z direction,
false twisting in the Z or S direction) and an air-jet texturized
yarn. Forming a sewing thread from a flat drawn yarn or a false
twisted yarn is preferred to obtain excellent properties.
[0028] The total yarn size of the poly(butylene terephthalate)
multifilament yarn is preferably from 20 to 550 dtex.
[0029] A poly(butylene terephthalate) multifilament flat drawn
yarn, especially suitable to produce a stretchable PBT sewing
thread, is characterized in that the multifilament yarn has a
tenacity between 25 cN/tex and 50 cN/tex, preferably between 30 and
40 cN/tex. It is also characterized as a yarn having an elongation
at break between 30 to 60%, preferably between 40 and 50%. It is
also characterized to have an elastic recovery from 20% elongation
of equal to or greater than 60%, even more preferably equal to or
greater than 75%.
[0030] The PBT sewing thread of the present invention has a
breaking strength between 20 to 50 cN/tex, preferably between 30 to
40 cN/tex; and a breaking elongation between 25 to 100%, preferably
between 40 to 50%. When the breaking strength is less than 20
cN/tex an insufficient seam strength results. On the other hand,
when the breaking strength exceeds 45 cN/tex, the sewing thread
shows a low breaking elongation, and the seam stretchability of the
fabric sewn articles becomes poor.
[0031] Furthermore, the sewing thread of the present invention
shows an elastic recovery from a 20% elongation of 60% or more,
preferably from 70 to 85%. When a stretchable fabric is sewn using
a sewing thread that shows an elastic recovery in the range
mentioned above, the stretchable fabric shows an extremely
excellent recovery performance.
[0032] The sewing thread of the present invention can be a plied
sewing thread, a core yarn, an intermingled sewing thread, or a
bonded sewing thread. The inventive sewing thread comprises at
least a multifilament PBT yarn or spun yarns of PBT staple
fibers.
[0033] A plied sewing thread can be made by first twisting the
multifilament yarn, the number of twists is preferably 200 to 2000
turns/meter (T/m). Examples of the number of doubling are 2-ply
thread obtained by doubling and twisting two yarns, 3-ply thread
obtained by doubling and twisting three yarns, 2.times.3-ply thread
obtained by doubling and twisting three 2-ply threads each of which
has been obtained by doubling and twisting two yarns. It is
desirable that the number of final twisting be from 0.7 to 0.8
times that of first twisting to suppress the formation of a kinky
yarn as much as possible. Moreover, the direction of final twisting
should fundamentally be the Z direction. However, for sewing
threads such as one for a two-needle lock stitch, both S twisting
and Z twisting are preferably applied. At least one of the
multifiament yarns must be PBT, the others yarns may be PTT, PET,
polyamide or a combination of these.
[0034] A core spun sewing thread can be made by sheathing the PBT
multifilament yarn with fibers of natural or synthetic origins. Two
or more of these sheathed single yarns are twisted together to form
a sewing thread. Examples of natural fibers are cotton fibers, and
examples of synthetic fibers are PBT, PET, PTT and polyamides.
[0035] Air-intermingled sewing threads can be made by texturing of
two multifilament yarns, by feeding the filament material into the
texturing jet at a higher speed than it is withdrawn therefrom. The
excess of the feed speed over the withdrawal speed, expressed as a
percent of the withdrawal speed, is termed the overfeed. In the
process the yarns which are to be mixed with each other are fed
into the texturing jet at different rates of overfeed. The feed
yarn strand which will constitute the core filaments of the yarn
will usually be fed into the texturing jet at an overfeed of from 3
to 10%, while the feed yarn strand which will constitute the effect
filaments of the yarn according to the invention will usually be
overfed at from 10 to 60%. The core yarn is a multifilament PBT
yarn, and the effect yarn may be PBT, PET, PTT or a polyamide
multifilament yarn.
[0036] Bonded sewing threads can be made by twisting two or more
multifilament yarns together and bonding them with a polymer
coating, such as an aqueous emulsion of linear polyurethane. At
least one of the multifilament yarns must be a PBT yarn, and the
other yarns PBT, PET, PTT or a polyamide multifilament yarn.
[0037] The sewing thread is preferably dyed by rewinding the thread
on a package dye tube and dyeing by standard methods. In order to
improve the cohesiveness or integrity and sewing performance of a
sewing thread, a solution containing a sewing performance improver,
a smoothing agent and a binder may be circulated around the yarn
package having been scoured after dyeing so that the agents are
allowed to adhere thereto. Examples of the sewing performance
improver and the smoothing agent include silicone compounds,
polyethylene-based emulsions and wax compounds. Examples of the
binder include polyester-based resins, polyurethane based resins
and acrylate based resins.
[0038] A stretch fabric in the present invention signifies a fabric
that shows an extensibility in the warp and/or weft direction of
from 5 to 200%. The extensibility herein is obtained by the
following procedure: two samples having dimensions of 140
mm.times.165 mm (tensile side.times.constraint side) with the
tensile side of one sample taken in the warp direction of the
fabric and that of the other sample taken in the weft direction are
prepared; each sample is pulled at a rate of 60 cm/min so that a
tensile elongation curve is obtained; the elongation of the fabric
sample to which a stress of 2 kg per 5 cm width is applied is
measured from the curve. Examples of fabric include a woven fabric,
a knitted fabric and a nonwoven fabric. Of the fabrics, a woven
fabric and a knitted fabric are especially preferred. Means for
applying stretch to these fabrics include a procedure that utilizes
the stretch of yarns forming the fabric, a procedure that utilizes
the stretch of the texture of the fabric, and a procedure that
utilizes a combination of the above two techniques.
[0039] Specific examples of the stretch fabric of the present
invention include clothes showing an extensibility of from 10 to
25% such as shirts, blouses, working clothes, uniforms, slacks,
jackets, suits and coats, clothes showing an extensibility of from
20 to 40% such as sports jackets, training wear, play wear,
T-shirts, underwear and sweaters, and clothes showing an
extensibility of from 40 to 200% such as foundation garments,
leotards, swimwear, skiwear and skate wear. Although the sewing
thread of the invention can be used for sewing all these stretch
fabrics, use of fabrics showing an extensibility of 20% or more,
particularly 40% or more is preferred because the seams are
excellent in elasticity and the sewn articles thus obtained do not
constrain the wearers and show excellent wearability.
[0040] In addition, the seams made using the inventive sewing
thread, in particular double lock stitch seams, have excellent seam
elasticity, which is also present when there is no excess yarn
length or only minimal excess yarn length of the sewing thread in
such a seam, whereby the high elasticity of the inventive sewing
thread and in particular the high elongation of same ensures that
after repeated strength loading and after repeated overloading of
the seam there is no unwanted gaping of the seam, as the sewing
thread adapts to the elasticity of the stretch fabric.
Test Methods
Tensile Strength and Elongation
[0041] Using a Statimat, a tensile elongation curve is obtained
under the conditions of a sample length of 100 mm and a tensile
speed of 600 mm/min, and the stress at 5% elongation and a 30%
elongation, the breaking strength (cN/tex) and the breaking
elongation (%) are measured.
Yarn and Thread Elastic Recovery
[0042] An initial load of 0.05 cN/dtex is applied to the thread,
and a stress-strain measurement is performed by elongating the
thread at a constant rate of 100 mm/min until a preset test load is
reached, at which point the test elongation is recorded. The yarn
is relaxed and the permanent elongation is determined. The yarn is
then elongated again to a higher test load. This procedure is
repeated by increasing the test load level in steps of 25 cN until
the yarn fails. The elastic recovery at each test load level is
calculated from the following formula: elastic recovery (%)=elastic
elongation/test elongation.times.100 wherein elastic elongation
designates the difference between test and permanent elongation.
E.g. a permanent elongation of 1.1% after test elongation of 15.1%
corresponds to an elastic elongation of 14% (=15.1%-1.1%) and an
elastic recovery of 92.6% (=14%/15.1%.times.100) at 15.1%
elongation. The elastic recovery at 20% elongation is obtained
through interpolation between two measurement points adjacent to
20% elongation. Specific Viscosity
[0043] A polymer is dissolved in dichloroacetic acid at 55.degree.
C. at a concentration of 0.1 g/cc. The solution thus obtained is
transferred to an Ubbelhode viscometer, and measured at 25.degree.
C. The specific viscosity (SV) is calculated from the following
formula: SV=T/T.sub.0-1 Where T is the drop time of the sample
solution and T.sub.0 is the drop time of the solvent.
EXAMPLE 1
[0044] A poly(butylene terephthalate) (SV=1.1) was spun at a
spinning temperature of 260.degree. C. and a winding speed of 3000
m/min to give a POY yarn. The yarn was then drawn by a draw twister
to give a drawn yarn of 95 dtex 32 filaments, the drawn yarn showed
a breaking strength of 35 cN/tex and a breaking elongation of 44%
and an elastic recovery from 20% elongation of 78%.
[0045] The PBT flat yarn thus obtained was first twisted to give
760 T/m (S direction). Three of such twisted PBT flat yarns were
final twisted together to give 570 T/m (Z direction) to produce a
3-ply thread. The 3-ply thread was then wound on a perforated
plastic bobbin, dyed in a dyeing bath at 100.degree. C. using a
disperse dye. The dyed thread was lubricated using silicone
oil.
[0046] The sewing thread thus obtained showed a breaking strength
of 30 cN/tex, a breaking elongation of 44%, an elastic recovery
from 20% elongation of 84%. Sewing elastic knitwear made of PET and
Lycra.RTM., with a fabric elongation at break of 96%, with this
sewing thread and stretching it, revealed a seam elongation of 60%.
The seam showed an excellent appearance even after stretching the
sewn fabric several times to an extent of 30%.
EXAMPLE 2
[0047] Using the procedure of Example 1, PBT was spun at 1180
m/min. The 91 dtex drawn yarn had a tenacity of 34.7 cN/tex, an
elongation at break of 29.5% and an elastic recovery from 20%
elongation of 80%.
[0048] A dyed plied sewing thread was produced by the procedure of
Example 1. The dyed sewing thread had a breaking strength of 32.3
cN/tex, a breaking elongation of 37%, an elastic recovery from a
20% elongation of 82%.
COMPARATIVE EXAMPLE 1
[0049] A dyed 3-ply sewing thread made from poly(ethylene
terephthalate), SV of 0.95, multifilament yarn, 95 dtex 32
filaments, was produced according to the procedure in Example 1.
The sewing thread had a tenacity of 63 cN/tex and an elongation of
22.5%. The thread elastic recovery from 20% elongation was close to
0. Sewing elastic knitwear made of PET and Lycra.RTM., with an
elongation at break of 96%, with this sewing thread and stretching
it, revealed a maximum elongation of only 29.7%.
COMPARATIVE EXAMPLE 2
[0050] A dyed 3-ply sewing thread made from poly(ethylene
terephthalate), SV of 0.95, multifilament yarn, 95 dtex 24
filaments, was produced according to the procedure in Example 1.
The multifilament yarn had a tenacity of 46.4 cN/tex and an
elongation at break of 45.3%. The elastic recovery from 20%
elongation was only 45%. Sewing elastic knitwear made of PET and
Lycra.RTM., with an elongation at break of 96%, with this sewing
thread and stretching it, revealed a maximum elongation of only
55%. The seam was overextended even after stretching the sewn
fabric to an extent of 30% and deformed the fabric.
COMPARATIVE EXAMPLE 3
[0051] A poly(trimethylene terephthalate), PTT (SV=1.1) was spun at
a winding speed of 1180 m/min. The yarn was then drawn by a draw
twister to give a drawn yarn of 64 dtex 32 filaments, the drawn
yarn showed a breaking strength of 36 cN/tex and a breaking
elongation of 49.8% and an elastic recovery from 20% elongation of
95%.
[0052] The PTT flat yarn thus obtained was doubled and first
twisted to give 650 T/m (S direction). Two of such twisted PTT flat
yarns were final twisted together to give 600 T/m (Z direction) to
produce a 2-ply thread. The 2-ply thread was then wound on a
perforated plastic bobbin, dyed in a dyeing bath at 100.degree. C.
using a disperse dye. The dyed thread was lubricated using silicone
oil.
[0053] The sewing thread thus obtained showed a breaking strength
of 29.1 cN/tex, a breaking elongation of 51.4%, an elastic recovery
from 20% elongation of 90%. Sewing elastic knitwear made of PET and
Lycra.RTM., with a fabric elongation at break of 96%, with this
sewing thread and stretching it, revealed a seam elongation of
65%.
[0054] An attempt was made to spin the PTT polymer at higher
spinning speeds (3000 mpm), but the spun yarn package build was
poor and the drawing of the spun yarn was unacceptable.
INDUSTRIAL APPLICABILITY
[0055] The stretchable PBT sewing thread of the present invention
is excellent in sewing performance, and that makes a seam excellent
in appearance and stretchability, and that exhibits excellent
adaptability to sewing a stretchable fabric. Although the PBT
multifialment yarn has a lower elastic recovery at 20% elongation
compared to PTT multifilament yarns, the final dyed sewing threads
have comparable elastic recovery and seam elongations. The use of a
PBT sewing thread is therefore preferable to PTT sewing threads
since its elasticity is not reduced during the dyeing and finishing
steps of the sewing thread process.
[0056] Thus it is apparent that there has been provided, in
accordance with the invention, a sewing thread, a process of using
sewing thread, and use of sewing thread, that fully satisfied the
objects, aims and advantages set forth above. While the invention
has been described in conjunction with specific embodiments
thereof, it is evident that many alternatives, modifications and
variations will be apparent to those skilled in the art in light of
the foregoing description. Accordingly, it is intended to embrace
all such alternatives, modifications and variations as fall within
the spirit and broad scope of the appended claims.
* * * * *