JPS6039428A - Polyester sewing machine yarn - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

The present invention relates to a sewing thread made of polyester fiber that has excellent sewability and beautiful seams. Traditionally, sewing machine threads made of polyester fibers have excellent strength and robustness, so they are widely used in place of cotton sewing threads to satisfy the Wash and Wear properties of polyester fabrics to be sewn. However, compared to cotton sewing thread, high-speed lockstitching performance is poor, and
There were many skipped stitches and there were problems with sewing. The purpose of the present invention is to
To provide a polyester fiber sewing thread that solves the above-mentioned problems with sewing threads made of polyester fibers, has excellent high-speed sewing properties in both lock stitches and chain stitches, and has less skipped stitches and less occurrence of puckering. It is something to do. That is. The gist of the present invention is that in a solvent with an inherent viscosity of [p-chlorophenyl/tetrachloroethane=3/1 (gray Li ratio)]
℃] is 0.50 or more (preferably 0.58
~1.0) and 85% or more (preferably 95%) of the constituent units
The above) consists of an ethylene component and a terephthalic acid component,
In addition, the birefringence in the cross section of the fiber satisfies the following formula [1] (preferably formula [2]), and Δn −Δn B < O...[1] Δn −ΔnB≦−1 ,0X 10-8...
... [2] Mu (However, △n JL: Birefringence index of the fiber at the position where r / R = 0.9 Δn B ; Birefringence index of the fiber at the position where r / R'' = 0.0: Radius r of the fiber cross section: distance from the central axis of the fiber cross section 1lIii) Furthermore, the birefringence Δn of the fiber is 180X10-8 or more (preferably 1
95X10-3 or more), a fiber length period of 160A or more (preferably 170λ or more) by small-angle X-ray diffraction, and a specific gravity of 1.390 or more, and is a polyester sewing thread using dry heat shrink polyester fiber. The polyester fiber that constitutes the present invention has a unique birefringence distribution in the fiber cross section that is reversed compared to ordinary thermoplastic polymer fibers, with the inner layer having a higher birefringence than the outer fiber layer. It has a birefringence distribution. In addition, the fiber length period is 160λ or more (preferably 170λ or more), which is longer than ordinary high-strength polyester fibers, the cutting elongation is 10 inches or less, and the fiber birefringence Δn is 180X10-" or more ( Preferable L<U195X10-1
Moreover, the orientation angle of the (100) plane determined by wide-angle X-ray diffraction is 8° or less, indicating a very high degree of crystal orientation, and the microstructure also tends to correspond to a super-stretched structure. There is. In addition, the specific gravity is 1.390 or higher, and the constant length heating thermal stress peak temperature is 210°C or higher. The dry heat shrinkage rate SHD is 15% or less, indicating physical properties that have been sufficiently subjected to stretching heat treatment. Furthermore, the cutting strength DT of the fiber, which is the most important practical performance, is 10,976 or more, which is significantly improved compared to the strength of conventional high-strength polyester fiber, which is at most 9.5 f/d. From the above, it can be said that the high-strength polyester fibers constituting the sewing thread of the present invention have a completely new microstructure compared to conventional high-strength polyester fibers. Furthermore, the molecular weight of the wood itself does not need to be extremely high; an intrinsic viscosity of 0.51 or more, preferably about 0.58 to 1.0, is sufficient. Of course, it is preferable that the molecular weight of the polymer be higher, but the most important feature of the polyester fiber of the present invention is that it has an improved microstructure. Conventional method for producing high-strength polyester fibers and Tokuko Sho 5
3-1367), a method using thick denier seven filaments (Japanese Patent Application Laid-Open No. 51-15021), a method in which high molecular weight polyester is spun and then multistage stretched (USP 3).
No. 651198), a method of delaying cooling solidification during spinning, and the like have been proposed. However, in a low denier filament like the polyester fiber of the present invention, the distribution of birefringence within the fiber cross section is poor. The idea of satisfying the requirements for a high-strength fiber by providing a unique birefringence distribution in which the inner layer has a higher birefringence than the outer layer has never been proposed. The above-mentioned unique microstructure has an intrinsic viscosity of 0.51 or more,
It is preferably 0.58 to 1.00, and is effectively exhibited when using a polyester in which at least 85 units of the constituent units are polyethylene terephthalate, and is particularly effective in increasing strength and improving fatigue resistance. is demonstrated. This is because in the case of polyester fibers whose main component is polyethylene terephthalate, in the conventional method, the refractive index distribution within the fiber cross section of low-denier high-strength filaments tends to be higher in the fiber outer layer than in the inner layer. This is thought to be because the stringability and stretchability are inhibited, making it difficult to increase the number of tie molecular chains that substantially contribute to high strength. In addition, in the present invention, monofilament Denny A'-1) Z35d
It also has the following characteristics. This is because when the single fiber denier becomes large, it becomes difficult to develop a uniform stretching stress concentration in the inner layer portion of the yarn, and this becomes a factor that inhibits the stretchability. . The degree of crystal orientation of conventionally known high-strength polyester filaments is 10 in terms of the orientation angle (OA) of the (100) plane.
'', the degree of crystal orientation f c (formula [3] below) is less than 95 inches, whereas in the case of the high-strength polyester fiber in the present invention, the orientation angle of the (100) plane is less than 8 inches, and the crystal orientation When expressed in degrees (fc), it is 95 degrees or more, and has an extremely high degree of crystal orientation. Further, the constant length heating thermal stress peak temperature, which is a measure of the stretching heat history, is 210°C or higher. This is a major feature of the polyester fiber in the present invention. In particular, the peak temperature is less than 210°C. It becomes difficult to express the unique distribution of birefringence within the fiber cross section, which is a feature of the present invention. When using high-strength fibers as sewing thread, mechanical properties at high temperatures are one of the most important factors in terms of practical performance. Mechanical property evaluation at high temperatures is quite difficult, and even when tests are actually conducted, troubles such as polymer deterioration before measurement tend to occur, resulting in problems with measurement accuracy and reproducibility. The present inventors evaluated the temperature dependence of dynamic viscoelasticity and mechanical temperature fractional characteristics as a measure representative of the mechanical properties of fibers at high temperatures using a flattened sheet with a sinusoidal strain of 110 c/s. As a result, the temperature (Ta) at which the loss tangent (Tanδ) is maximum
1 If it is a normal high strength polyester fiber, the high A160
Although the temperature (Ta) of the present invention is lower than 160°C, the polyester fiber of the present invention exhibits a high value of 160°C or higher. T blur,
This indicates the rigidity of the polymer in the amorphous portion, and the higher the Ta value, the smaller the degree of deterioration of mechanical properties at high temperatures. Therefore, it can be said that the mechanical properties at high temperatures of the high-strength polyester fibers constituting the sewing thread of the present invention are superior to conventionally known high-strength polyester fibers. Namely, the sewing thread of the present invention does not melt even under high-speed sewing conditions where conventional polyester milling thread would easily melt, and has the highest rotational speed of current lockstitch threads.
Even if sewing is continued for 30 seconds at 000 rpm, no uncut parts occur. Next, the birefringence distribution within the fiber cross section according to the present invention will be explained in more detail. △n −Δn B < 0 ・・・・・・・・・[1]
Preferably △n -Δn≦-1, Ox 10-s...
...[2] Mu B [where Δn and ΔnB are as described above] is selected. In formulas (1) and (2), ΔnA represents Δn of the yarn outer layer, and ΔnB represents Δn of the yarn inner layer. The inner layer has a very unique microstructure in which Δn is smaller than that of the inner layer. The distribution of birefringence within the fiber cross section of conventional polyester fibers tends to be higher in the outer layer than in the inner layer, and the cutting strength is only about 9.5 f/d at most. Furthermore, the fact that the birefringence within the cross section of the fiber has a distribution in which it increases from the inner layer toward the outer layer is considered to be a factor that inhibits stringiness in the spinning and drawing steps. Therefore, we conducted intensive research on spinning and drawing technology and obtained the following knowledge. In other words, if the stretching stress can be concentrated in the center of the yarn by, for example, stretching the surface layer of the yarn while locally heating it during the stretching process, the stretching deformation pattern will be very mild, and the maximum stretching ratio can be reached. This can be improved compared to normal stretching methods. In addition, the phenomenon that ``drawing stress concentrates on the surface layer of the yarn, causing strain defects, and the fiber strength is significantly lower than the theoretical strength'', which has been pointed out with conventional drawn yarns, is suppressed, and the final surface fiber The internal microstructure is the superstretched structure proposed by C1ark et al. [References: W, N, Taylor+ Jr-* E, S
, C1ark. Polym, Eng, Sc! ,, 18.518 (19
78)), and it becomes possible to obtain polyester fibers with superior tensile strength and breaking strength compared to conventional high-strength fibers for industrial materials. On the other hand, as seen in Tokusekki Publication No. 51-15021. It is known that thick denier polyester monofilaments with a single filament denier of 1000 d or more have a substantially uniform internal structure, except for the low orientation of polymer chain segments near the surface of the filament.
As clearly stated in the published specification, even though the method is suitable for low denier filaments, it cannot provide equivalent properties to thick denier monofilaments. Further, the cutting strength of the monofilament described in this publication is only 8.49/d at most, which is completely different from the low denier high strength filament as intended by the present invention. The present invention was completed as a result of further research based on the above findings. Next, a method for producing polyester fibers having the above characteristics will be briefly explained, but the present invention is not limited to the following method. In producing the polyester fiber of the present invention, the spinning and drawing process, especially the drawing process, is important. That is, 1. For example, when undrawn yarn with a birefringence of 0.002 to 0.060 obtained by melt-spinning polyester with IV≧0.58 is drawn continuously after spinning or once wound up and then stretched, the undrawn yarn is It is preferable to carry out the first drawing at a total draw ratio of 40 or more between the drawn yarn first supply roller and the roller maintained at 100°C or less, and if necessary, perform the first drawing with the undrawn yarn second supply roller. A high-temperature pressurized steam jetting nozzle is provided between the loaf and the nozzle temperature is set to 200° C. or higher to jet high-temperature steam, and the stretching point is fixed near the high-temperature pressurized steam jetting nozzle. Furthermore, when performing the second stage stretching, the ambient temperature provided between the first stretching roller and the second stretching roller is 170 to 420.
°C in a slit heater (a heating device that has a slit as a yarn running path, and heats the yarn while running through the slit in a non-contact manner: ambient temperature refers to the temperature inside the slit) The yarn is allowed to pass therethrough for a period of 0.3 seconds or more, and then subjected to a second drawing roller. At that time, a temperature gradient is provided in the slit heater, and the atmospheric temperature at the yarn inlet is set to 170°C or higher, and the atmospheric temperature at the exit is set to 420°C.
℃ or less, and the yarn is 0 in an atmosphere of 200 to 420℃.
．． It is preferable to allow the thread to pass through so that it can remain there for 3 seconds or more. In addition, after the completion of two-stage stretching, it can be stretched continuously at 230 to 165°C, either continuously without winding or after winding.
It is also possible to further improve the dimensional stability by performing a relaxation process of 096 or less. The polyester that is the raw material for the polyester sewing thread contemplated in the present invention has an intrinsic viscosity of 0.50 or more, preferably 0. .65-1.20
At least 85 moles of the structural units, preferably at least 95 moles, are composed of ethylene terephthalate, and other structural units that can be mixed in small amounts include diethylene glycol and other polyethylene glycols having 1 to 10 prime members. , hexahydro-p-xylylene glycol, isophthalic acid, dibenzoic acid, p-tert-phenyl-4,4'-dicarboxylic acid, aromatic dicarboxylic acids such as hexahydroterephthalic acid, aliphatic dicarboxylic acids such as adipic acid , hydroxy acids such as hydroxyacetic acid, and the like, and such polyester materials are made into fibers by ordinary melt spinning methods. Such polyesters may contain matting agents, pigments, light stabilizers, heat stabilizers, and antioxidants as required. Antistatic agents, dyeability improvers, adhesion improvers, etc. can be blended, and all can be used, except those that have a serious adverse effect on the properties of the present invention depending on how they are blended. The polyester yarn thus obtained can be made into sewing thread as flat yarn, woolly textured yarn or staple fiber through one conventional process. In this case, it is possible to use the polyester sewing thread of the present invention in combination with other sewing machine threads other than the present invention by means of blending or doubling. It is preferable to use 30% by weight or more of the amount of . Below, methods for measuring the main parameters used to measure the structural characteristics and physical properties of the fibers constituting the present invention will be described. Measuring method of intrinsic viscosity> Measurement is carried out in a mixed solvent consisting of 75% by weight p-chlorophenol and 25% by weight tetrachloroethane. The polymer is dissolved in the solvent at room temperature and the viscosity measurements are carried out in an Ostwald-Fenske capillary viscosity needle at 30°C. Intrinsic viscosity is the limit value at which the natural logarithm of the ratio of solution viscosity to solvent viscosity divided by the concentration of the polymer solution in grams of polymer per 100 g of solution approaches zero yield. Measuring method of birefringence (Δn〉) Nikon polarized LT am P OH type Life Co., Ltd. Bereck convensator was used, and a spectral light source activation device (Toshiba 5LS-3-B type) was used as the light source (Na light source)
. Place nine samples cut at an angle of 45'' with respect to the fiber axis of 5 to 6aI length, with the cut side facing up.Place the sample slide glass on a rotating stage, and place the sample slide so that the sample is against the polarizer. Adjust the stage by rotating it once so that the angle is 45°, insert the analyzer, and make a dark field, then set the compensator to 30 and count the number of stripes (n pieces).Turn the compensator in the right direction. After turning the compensator to the null point where the sample first becomes darkest (a), turn the compensator counterclockwise and measure the compensator scale (b) where the sample first becomes darkest. /
1o scale), return the compensator to 30, remove the analyzer, measure the diameter d of the sample, and calculate the birefringence (△n) based on the following formula [4] (average of 20 measurements). value). Δnyo r/d...Song [4] rNitoraptiont=nλo-) lλo:=5
89.3mμ #: C/100 in the Nira 4F compensator manual
From 00 and i, 1 = (a-b) (: difference in convensator readings) <Method for measuring 61 distribution in fiber cross section> Central refractive index obtained using a transmission quantitative interference microscope (
nl, O and nllO) and outer layer refractive index (nU20.9
and n7, 0.9), the unique molecular orientation of the fibers of the present invention becomes clear and can be associated with the excellent strength of the fibers of the present invention. Transmission stationary interference microscope (
For example, the distribution of the average refractive index observed from the side surface of the fiber can be measured by the interference fringe method obtained using an interference microscope Interfaco (manufactured by Carl Zeiss Jena, East Germany). This method can be applied to fibers with a circular cross section. The refractive index of a fiber is characterized by the refractive index (nl) for polarized light vibrating parallel to the fiber axis and the refractive index (nl) for polarized light vibrating perpendicular to the fiber axis. All measurements described here used a xenon lamp as the light source. It is carried out with the refractive index (nl and nl) obtained using green light with an interference filter wavelength of 544 mμ under polarized light. The following n O and n are determined from the measurement of n/ and nl.
o, 9 will be explained in detail, but nl (nl, 0 and n, 1, 0.9) can also be measured in the same way. The fibers to be tested use optically flat slide glasses and cover glasses, and
．． Refraction "F" that gives a shift in interference fringes within the range of 2 to 1 wavelength
- (nE) in a mounting medium that is inert to the fibers. The refractive index (nB) of the mounting medium is
This is the value measured at 20'C using Atsube's refracting needle with a light source of 44 mμ). This mounting medium is, for example, a mixture of liquid paraffin and bromnaphthalene.
It can be adjusted to have a refractive index of 48 to 1.65. A single fiber is immersed in this mounting medium. This interference fringe pattern is photographed, magnified 1000 to 2000 times, and analyzed. As shown in Figure 1, the refractive index of the fiber encapsulant is nB, and the average refractive index of the fiber between 3/-8" is n7.
, the thickness between S' and S' is t. If the wavelength of the light beam used is λ, the distance between parallel interference fringes in the background (corresponding to lλ) is Dn, and the deviation of the interference fringes due to the fiber is dn, the optical path difference is dn. It is expressed as L =, , 2 = (n 7 - n B ) t.If the refractive index of the sample is ns, the refractive indices n1 and n2 of the sealed liquid are: n B < n 1 n g < n 2 The pattern of interference fringes as shown in Fig. 1 is evaluated using the following. L2nl ・/=L 1- L 2 ``”””' [5] Therefore, [
5] Based on the optical path difference at each position from the center to the outer periphery of the fiber, the distribution of the average refractive index (nl) of the fiber at each position can be calculated. The thickness can be determined by calculation assuming that the obtained fiber has a circular cross section. However, due to variations in manufacturing conditions or accidents after manufacturing, there may be cases where the cross section is not circular. In order to eliminate this inconvenience, it is appropriate to use a portion to be measured where the displacement of the interference fringes is symmetrical with the fiber axis as the axis of symmetry. The measurement is performed between θ and 0.9R, where R is the radius of the fiber. I
By performing this at intervals of R, the average refractive index at each position can be calculated. Since the distribution of nl can be determined in the same way, the birefringence distribution can be determined using the following formula % formula % [6]. Δn (r/R) is obtained by measuring at least 3 filaments, preferably 5 to 10 filaments, and averaging the following: <Method for measuring strength and elongation properties of fibers> Tensilon manufactured by Toyo Baldwin Co., Ltd. was used, sample length (gauge length) was 100 mm, elongation speed was -100 mm/min, recording speed was 500 mm/min, and initial load was 1/30 f/d. The S-8 curve of single fiber was measured under the following conditions and the cutting strength (, r/dL cutting elongation (%
), the initial elastic modulus (f/d) was calculated. The initial elastic modulus is
It was calculated from the maximum slope near the origin of the SS curve. For the calculation of each characteristic value, measurements of at least 5 filaments, preferably 10 to 20 filaments are averaged. <Measurement method of fiber long period LP by small-angle X-ray diffraction> Small-angle X
The measurement of the ray scattering pattern is carried out using, for example, an X-ray generator manufactured by Rigaku Corporation (RU-3H type). For measurements, the tube voltage was 45 KV and the tube current was 70 mA. CuKα (monochromatic with copper anticathode and nickel filter)
λx=1.5418λ) is used. Attach the single fiber samples to the sample holder so that they are parallel to each other. It is appropriate that the thickness of the sample is 0.5 to 1.0 degrees. X-rays are incident perpendicularly to the fiber axes of the fibers arranged in parallel to produce P S P C (made by Rigaku Denki).
Po5ition 5intensive Propo
-rtional Counter) system. An overview of this system can be found in 5. For example, [Polmer Jour]
nal. Vol. 13, 501 (1981)). The measurement conditions were a 0.3ffφ x 0.21111φ medium pinhole collimator. Distance between sample and probe: 400 m Number of MCA (multichannel analyzer) measurement channels: 256 Measurement time: 600 seconds. Data processing is performed by subtracting the air scattering intensity from the measured scattering intensity using moving average processing, and by reading the maximum intensity position, the long-period small-angle scattering angle 2
From α, calculate the fiber long period according to the following formula [7].
See Figure 2 (A) l (B): In the figure, 1 is the sample, 2 is the P
SPC probe% 3 is position analyzer, 4
5 indicates the MCA, and 5 indicates the display section]. λx=1.5418A The moving average processing is calculated according to the following formula. However, in the above formula, I(S)N and I(S)i are the measured scattering intensities (intensities minus the air scattering intensity) of channel numbers N and i, respectively. K is the moving average number of points adopted (here = 7), N-K)
0. N+≦256 <Method for measuring orientation angle (OA)> The orientation angle (OA) of the fibers can be measured using, for example, X manufactured by Rigaku Denki Co., Ltd.
Line generator (RU-31), fiber measuring device (FS-3)
, a goniometer (SG-7) and a scintillation counter. For measurement, CuKα (wavelength λ = 1.5418A >) monochromated with a nickel filter is used. For measurement of orientation angle, 20 of (100) plane reflection is used. 2θ of reflection used is It is determined from the diffraction intensity curve. The X-ray generator is operated at 45 KV% 70 mA, and the fiber sample is attached to the fiber measuring device so that the single yarns are parallel to each other. The thickness of the sample is 0.5 kV. It is appropriate to set the goniometer to the 2θ value determined by preliminary experiments.
Inject the beam (beam vertical transmission method). Scan the azimuth direction from -30" to +30°, and record the diffraction intensity on recording paper with a scintillation counter. Furthermore, -180" and +
Record the diffraction intensity of 180". At this time, the scanning speed is 4"/m, the chart speed is 1.0m/sit, the time connutant is 2 seconds or 5 seconds, and the collimator 1 and the φ% V sieving are 1" in both the length and width of the slit. To calculate the orientation angle from the obtained diffraction intensity curve, +180
Take the average value of the diffraction intensities obtained in step 6 and draw a horizontal line. Drop a perpendicular line from the top of the peak to the base line, and find the midpoint of its height. Draw a horizontal line through the midpoint. The distance between the intersection of this horizontal line and the diffraction intensity curve is measured, and the value obtained by converting this value into an angle (°) is defined as the orientation angle (OA). <Mechanical temperature dispersion> Using Rheovibron manufactured by Toyo Sokki Co., Ltd., initial thread length 4
On. Measurement is performed under the conditions of a temperature increase rate of 2° C./min and a sine frequency of 110 Hz during measurement, and the temperature (Tα) at which the loss tangent tan δ = E/ -E// is maximum is determined. However, in the above formula, E' is the storage modulus (dyne/C
A) bE'' is the loss modulus (dyne/i). [For details - Memoirs of the Facul
Ty of Engineering-neering Kyushu
University + vol, 23+ 41
(1963)] The complex elasticity 4KE is calculated by the following formula. However, h A: Coefficient due to the amplitude factor (Arnpl: Factor) during tanδ measurement (see Table 1) D: Dynamic FOTCe Dial value L
−、Sample length (study) S; Sample cross-sectional area (d) Table 1 Loss modulus E" is E'= I El sin δ...
・・・・・・

Calculated using [9]. <Single yarn denier> Measured according to JIS-L1073 (1977). <Dry heat shrinkage rate> Measured according to JIS-L1073 (1977) K at 160°C. <Specific Gravity> Create a density gradient tube made of n-hebutane and carbon tetrachloride, place a sufficiently defoamed sample into the density gradient tube whose temperature is controlled to 30℃±0.1℃, and leave it for 5 hours. The sample position in the subsequent density gradient tube was read on the scale of the VB gradient tube, converted to a specific gravity value from the density gradient tube scale using a standard glass float - specific gravity calibration, and measured at n = 4. . As a general rule, specific gravity values continue to four decimal places. Fixed length heating thermal stress peak temperature〉 Section length 4.5 side, heating rate 20℃/min, initial load 0.05f
/d, measure the thermal contraction stress from room temperature to the melting temperature, and find the temperature at which the thermal stress is maximum. [For details, see Textile Re5earch Jour
nal, vol-4'L732 (1977). Unless otherwise specified, "parts by weight" and "% by weight" are shown. Example 1 Polyethylene terephthalate having an intrinsic viscosity shown in Table 2 was used as a raw material, and spinning was carried out under the conditions shown in the same table. An undrawn yarn having a birefringence shown in the table was obtained. During spinning, an appropriate amount of spinning oil was applied to the surface of the yarn before taking off the undrawn yarn. The obtained undrawn yarn was drawn under the conditions shown in Table 3. A drawn yarn having the quality shown in Table 4 was obtained. Table 2 Table 3 Table 4 Next, after piling the 10 drawn yarns according to the present invention shown in Example 1 in Table 4, first twisting was applied to the three yarns, and then ply twisting was performed. It was then dyed at 130°C to make sewing thread. Use this sewing thread to make 65cm polyester. When 4 layers of 35 inch rayon plain fabric (fabric weight 150 f/d) were layered and sewn at a sewing speed of 5000 rpm, 3 consecutive layers were sewn.
I was able to sew for 5 seconds without thread breakage. On the other hand, when the sewing thread obtained in the same manner as above using the drawn thread of Comparative Example 1 in Table 4 was subjected to the &I test in the same manner as above, it was found that the sewing thread stopped 21 seconds after the start of sewing. I broke the thread.

[Brief explanation of drawings]

FIG. 1 (A) is a schematic diagram showing the interference fringes seen when the fiber of the present invention is observed from the lateral direction with an interference microscope, and FIG. 1 (B)
Figure 2 (A) is a schematic diagram showing the arrangement of the sample and film surface, etc. in small-angle X-ray diffraction measurement using the PSPC system, and Figure 2 (CB) shows the small-angle X-ray diffraction pattern of the fiber of the present invention. It is a schematic diagram. Applicant: Toyobo Co., Ltd.

Claims (9)

[Claims] (1) A polyester having an intrinsic viscosity of 0.50 or more (value measured at 30°C in a solvent with Cp-chlorophenol/tetrachloroethane = 3/1 (weight ratio)) and in which 85 moles or more of repeating units are ethylene terephthalate. is a fiber material, and the birefringence within the cross section of the fiber satisfies the following formula [1]. Δn −Δn B < 0 ・・・・・・・・・[1]
(However, ΔnA: birefringence index of the fiber at the position of r/R=0.9 Δn s: birefringence index of the fiber at the position of r/R=O−0 R: radius of the fiber cross section r: the birefringence index of the fiber at the position of r/R=0.9 (distance from the central axis) Furthermore, the birefringence Δn of the fiber is 180X10-3 or more,
The fiber length period determined by small-angle X-ray diffraction is 160λ or more, the IA specific gravity is 1.390 or more, and the dry heat shrinkage rate is 15 inches or less. A polyester sewing thread characterized by using polyester fibers having a single yarn denier of 35 denier or less. (2) A polyester sewing thread according to claim 1, which uses polynisder fiber having an intrinsic viscosity of 0.65 to 1.20. (3) The polyester sewing thread for polyester fibers, which has a birefringence Δn of 195×1 G″-s or more, as set forth in claim 1 or ti2. (4) A polyester sewing thread using a polyester fiber having (ΔnA−ΔnB) of −1, Ox 10 −8 or less, as set forth in any one of claims j11 to 3. (5) In any one of claims 1 to 4,
A polyester sewing thread using polyester fibers having a long fiber period of 1roA or more as measured by small-angle X-ray diffraction. (6) In any one of claims 1 to 5,
A polyester sewing thread using polyester blown fibers having a breaking elongation of 10- or less. (7) In any one of claims 1 to 6,
A polyester sewing thread using polyester fibers having a cutting strength of 10 f/d or more. (8) In any one of claims 1 to 7,
The orientation angle of the (100) plane determined by wide-angle X-ray diffraction is 8
Polyester sewing thread using polyester fibers that are less than 30%. (9) A polyester sewing thread using polyester fiber a having a temperature (Tα) of 160° C. or higher according to any one of claims 1 to 8. αQ In any one of claims 1 to 9,
A polyester sewing thread using polyester fibers whose constant length temperature rise thermal stress peak temperature is 210°C or higher.