JPS63159518A - Polyester fiber - Google Patents

Abstract

PURPOSE:To provide the titled fiber composed of polyethylene terephthalate, having a specific stress-elongation curve measured by the tensile test of the fiber and excellent dimensional stability and fatigue resistance and suitable for rope, tire cord, etc. CONSTITUTION:The objective polyester fiber is composed of a polyethylene terephthalate and has the following properties. The yield stress (Ys) is >=4.5g/d at the yield point (Yp) defined by the crossing point of a part having steep gradient including the rising part at the initial stage of tensile test with a part near the breakage of the fiber and having low gradient in a stress-elongation curve measured by the tensile test of the fiber. The elongation (E2) between the yield point and the breakage is >=50% of the elongation (E1) up to the above yield point, the initial tensile resistance (Mi) is >=100g/d and the terminal modulus (Mt) is <=10g/d.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is a polyester fiber having a thermally stable fiber structure, which is particularly suitable for industrial material use, and has dimensional stability,
and regarding polyester fibers with outdated fatigue resistance.

[Prior art]

Polyester fibers have the characteristics of high strength and high elastic modulus, and are therefore widely useful in various industrial material applications. For example, it is used for rubber reinforcing materials such as tire cords, power transmission belts, and conveyor belts, seat belts, fishing nets, sewing threads, cover sheets, etc.

However, polyester fibers generally have dimensional stability,
Since it has the drawbacks of poor fatigue resistance and poor fatigue resistance, improvements in these properties are required in order to further expand its use in the future. Conventional polyester fibers and methods with improved dimensional stability and fatigue resistance are disclosed in, for example, JP-A-51-5G019 and JP-A-5G-5803.
This has been proposed in Publication No. 1, etc. The former describes a method for producing polyester fibers with excellent dimensional stability by hot drawing undrawn yarns with a relatively high degree of orientation.
The latter proposes a polyester fiber with excellent dimensional stability and fatigue resistance obtained by hot drawing an undrawn yarn having a birefringence of 9×10 −3 to 70×10 −3 orientation.

Furthermore, the polyester fiber of the present invention is characterized by exhibiting a unique SS curve when subjected to a tensile test. Japanese Patent Publication No. 55-3447, Japanese Patent Application Publication No. 161119-1987, Japanese Patent Publication No. 57-161-1
This method has also been proposed in Japanese Patent Application Laid-open No. 54410, Japanese Patent Laid-Open No. 13718/1983, and the like.

[Problems to be solved by the present invention]

The above-mentioned JP-A-51-5g019 and JP-A-51-5g-
Publication No. 58031 is an excellent proposal for improving dimensional stability. According to JP-A-58031, the fatigue resistance is also improved at the same time, but this is due to relatively small deformation during tire running, for example, the model test described in the specification is about 0°6 God. This is a fatigue test in a low stress range up to
It can be seen that the target is cyclic fatigue in the following minute deformation area.

The purpose of the present invention is to improve fatigue resistance not only in the above-mentioned extremely small deformation range, but also in general industrial materials such as sewing thread, rope, etc.
Fishing nets, conveyor belts, etc., and tire cords can also be used as bias tires that undergo relatively large deformations, and are mainly used to improve resistance to repeated bending and/or elongation-compression fatigue with a strain of less than a few percent. It's about doing. As described above, an effective technique for significantly improving dimensional stability and improving fatigue properties including a relatively large deformation area as intended by the present invention has not been proposed to date.

Therefore, the object of the present invention is to provide a polyester fiber characterized by a stable 'a' structure that is useful as T& fibers for various industrial materials.

[Means for solving problems]

The present invention is a polyester fiber consisting essentially of polyethylene terephthalate, which has a yield point stress (Ys) of 4.5 g/d or more in the stress elongation curve determined by the FASFT tensile test. In addition, the shear ratio (E2) from the yield point to the skewer (E1) until the yield point is 50% or more, the initial tensile resistance (Mi) is 1003/d or more, and the terminal modulus (E1) is 50% or more. It is a polyester fiber characterized in that Mt) is 10 g/d or less. It also has the following fiber structure parameters.

Birefringence △rl≧160X10-3 density
ρ ≧1, 395g/cm3 crystal orientation
fc≧0.92 Degree of amorphous molecular orientation F≦0.90 DSC melting point Tm≧255' It is characterized by having fiber properties such that the degree of breakage (E) is 10% or less and the dry heat shrinkage rate measured at 150'c is 3% or less.

The polyester fibers of the present invention consist essentially of ethylene terephthalate and may contain less than 10% of ester-forming components. Examples of ester-forming components include terephthalic acid, ethylene glycol, and ethylene oxide components, as well as aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, and diphenyldicarboxylic acid, and diol components such as propylene glycol and butylene glycol. There are copolymerized polymers in which the latter component is copolymerized, or mixed polymers in which a polymer obtained from the former component and the latter component is melt-mixed with polyethylene terephthalate.

The polyester fiber of the present invention has a yield point stress (Y
s) is 4.5 g/d or more, and the elongation rate (E
2) is 50% or more, and the initial tensile resistance (
M i ) is 1008/d or more, and the terminal modulus (Mt) is 103/d or less. In order to clarify the above definition, Fig. 1 shows Example-2 of the present invention in the Examples described below.
This will be explained using this as an example. In general, the SS curve of a polyester m-fiber consists of a high slope portion including a rise at the initial stage of tension, and a relatively low slope portion near the cut. The intersection of the two, that is, the bending point of the SS curve, is defined as the yield point (Yp), and the stress at this point is the yield stress (Ys).
It is. Depending on the fiber, the above-mentioned bending point may be unclear and it may be difficult to determine the yield point, but in this case, it is determined as the intersection of the tangent to the rising part at the initial stage of tension on the SS curve and the straight line drawn from the straight part near the cutting point. Ta.

The polyester fiber of the present invention has the above-mentioned yield point stress of 4.5 g.
It is characterized by appearing at high stress of /d or more.

In addition, the elongation rate E1 from the start of tension to the yield point is 9.6
% or less, usually 4.8 to 7.2%.

The offshore ratio E2 from the yield point to the cutting point is 50% of the above E1.
That is, it is about 2.4% or more, usually 3 to 12%, and is characterized by a higher elongation of $E2 after the yield point than conventional polyester fibers.

The polyester fiber of the present invention has a high initial tensile resistance Mi determined from the SS curve of 100 g/d or more, and a low terminal modulus Mt of 10 g/d or less.

The initial tensile resistance M1 is based on the definition of JIS L1017 and the water method. The terminal modulus Mt is determined by 2.0% from the cutting elongation on the 88 curve in the fiber tensile test.
The stress increment between the point on the curve subtracted by 4% and the cutting point is 2.4
It refers to the value divided by X10-2. The specific conditions for the tensile test to obtain the SS curve are as follows.

Take a sample in the form of a cold, leave it in a temperature and humidity controlled room at 20℃ and 65% RH for more than 24 hours, and then
TL-4L” type tensile testing machine (manufactured by Toyo Baldwin)
The measurement was carried out using a sample length of 25 cm and a tensile speed of 30 cm/+nin.

;;Collection of octopus;! The same applies to the strength and elongation measurement described below.

Polyester fibers having the above characteristics of SSTM line are
It can be seen from the curves in FIG. 1 that the area surrounded by the SS curve is larger than expected from the numerical values of strength and elongation. Polyester fibers with such curves exhibit excellent durability even in fatigue tests when subjected to relatively large deformations.

Polyester fibers exhibiting such an SS curve also have significantly improved dimensional stability. That is, a polyester fiber that satisfies the above SS curve has both excellent fatigue resistance and dimensional stability, but its fiber structure is characterized by the following parameters.

Birefringence Δn≧160X10-3 density
ρ ≧1, 3958/cm3 crystal orientation f
c≧0.92 Degree of amorphous molecular orientation F≦0.90 DSC melting point Tm≧255°C Birefringence is 160×10−3 or more, usually 170×10−
3 or more, indicating that the orientation has progressed sufficiently. It has a density of 1.395 or more, which is higher than normal polyester fibers, and a high degree of crystallinity.

The degree of crystal orientation is sufficiently high as in ordinary polyester, while the degree of amorphous molecular orientation is characterized by low orientation, as in the case of polyester fibers produced by high-speed spinning and hot drawing as shown in the above-mentioned known examples. Furthermore, the melting point of the 'a fiber of the present invention measured by DSC is 260° C. or higher, which is higher than that of the polyester fiber described in No. 1, which proves that it is thermally stable.

Furthermore, the polyester fiber of the present invention characterized by the above SS curve and fiber structure parameters has a strength of 5 g/
d or more, the cutting elongation is 10% or more, and the dry heat shrinkage rate measured at 150°C is 3% or less, which is low shrinkage.

A polyester fiber that satisfies the SS curve of the present invention can satisfy the above-mentioned fiber structure parameters and fiber properties.

The fiber of the present invention can be produced by the following new method.

In order to produce the polyester fiber of the present invention, a polyester polymer consisting essentially of polyethylene terephthalate has an intrinsic viscosity (Iv) of 0.6 or more, preferably 0.7.
Use the above. It is preferable to use an extruder type spinning machine for melt spinning the polymer. The spinning speed is 7000 m/min or more, preferably 7500 m/min.
The speed is higher than min. 1 oc directly below the spinneret
A heating atmosphere of at least tn and at least 1 m above the melting point of the polymer, preferably above the spinning temperature, is created by providing a heat insulating cylinder, a heating cylinder, etc. After passing through the above heating atmosphere, the spun yarn is quenched and solidified with cold air, and then, after being applied with an oil agent, it is taken off by a take-off roll that controls the spinning speed. Since the present invention performs high-speed spinning at 7000 m/min or more, the spinning back must be precisely checked, and the average pore diameter must be 10 to prevent foreign matter from entering the melt polymer.
It is preferable to use a stainless steel nonwoven fabric filter having pores of 71 μm or less, preferably 7 μm or less. Control of the heating atmosphere immediately below the spinneret is also important in order to maintain stringiness during high-speed spinning. The taken-off undrawn yarn is once wound up by a winding machine. At this time, the undrawn yarn is birefringent or 80×10−
3 or more, usually 100XIO-3 or more, which is highly oriented. The undrawn yarn is then hot drawn at a temperature of 180'C or higher, preferably 230C or higher. Stretching ratio is 1.0
The range is 5 to 1.4 cultures. In the undrawn yarn, no clear yield point was observed in the SS curve, and the strength was 5. g/d, and the modulus is also less than 1002/d. Further, when the undrawn yarn is cold-stretched or hot-stretched at a temperature of less than 180°C, the terminal modulus becomes an SS curve of IJ/r1 or more, and the density is also less than 1.395 g/cc. The dry heat shrinkage rate exceeds 3%, and sufficient improvement in fatigue resistance cannot be achieved. On the other hand, when the undrawn yarn is heat-treated at a draw ratio of less than 1.05 without substantial drawing, the yield point of the SS curve ball is unclear and the strength is 58/
or the initial tensile resistance is less than 100 g/d, making it unsuitable as a fiber for industrial materials. The fiber thus obtained has the characteristics of the polyester fiber 'vM of the present invention.

Next is implementation 1! The explanation will be based on the following, except for the above-mentioned methods for measuring the fiber properties of the present invention: a, ttt structural parameters, and a.

(a) Birefringence Birefringence was determined using a POH-type wide light microscope manufactured by Nippon Kogaku Kogyo Co., Ltd. and the usual Bellick compensator method using the D line as a light source.

(b) Density Measurement was performed at 25° C. using a density gradient tube prepared with carbon tetrachloride as one liquid and n-hebutane as a light liquid.

(c) Crystal orientation was measured using an X-ray generator (RU-200PL) manufactured by Rigaku Denki Co., Ltd. using CuKα as a radiation source. Equatorial line interference (01
0) from the half-width HO of the intensity distribution curve of the surface using the following equation.

fc=(180Q-H[1)/180G(d) Amorphous molecular orientation sample is 0.2 of fluorescent agent "MikephorεTN"! f
After being immersed in a fi% aqueous solution for 5 g at 55°C, it was thoroughly washed and air-dried to prepare a measurement sample. Using a FOM-1 polarization photometer manufactured by JASCO Corporation, the relative intensity of polarized fluorescence was measured at an excitation wavelength of 365 nm and a fluorescence wavelength of 420 nm.
Obtained from Miko Tsukishiki.

F=1-B/A However, A: Relative intensity of polarized fluorescence in the direction of the fiber axis B: Relative intensity of polarized fluorescence in the direction perpendicular to the pJ fiber axis (e) DSC melting point DSC-IB model manufactured by Perkin-E1mer, Measurement was performed using a heating rate of 10 ml, a sample ff of 14.0 mg, and a sensitivity of 4 mcal/S-Ryl 2'7-L, and the main peak temperature of the melting curve was defined as the melting point (T m ).

(f) Dry heat shrinkage rate △S A sample was taken in the form of a skein, and after being left in a temperature and humidity controlled room at 20°C and 65% RH for 24 hours or more, a load equivalent to 0°18/d of the sample was applied and measured. Samples of length LO are processed under tension in an oven at 150° C. for 30 minutes. The treated sample was air-dried, left in the above-mentioned temperature and humidity control room for 24 hours or more, and the above-mentioned load was applied again to calculate the measured length LO using the following formula.

Dry heat shrinkage rate (%) = (L-LO)/L.

×100 [Example-1] Polyethylene terephthalate having an intrinsic viscosity (IV) of 0.85 was melt-spun using an extruder type spinning machine. A stainless steel nonwoven fabric filter with an average pore size of 5 μm was incorporated into the spinning pack to filter the melt polymer. The die used had a hole diameter of 0.23 mmφ and 36 holes, and the polymer temperature was 295°C.

A 15 cm heating cylinder was attached directly below the mouthpiece, and the atmosphere inside the cylinder was heated to 280°C.

The ambient temperature is the ambient temperature measured at a position 10 cm below the mouth surface and 1 cm away from the outermost thread. A uniflow type chimney with a length of 120 cm was attached below the heating section, and cold air was blown at 20°C at a rate of 30 m/min perpendicularly to the yarn to cool it.

The yarn spun from the spinneret passes through a heating cylinder atmosphere, is rapidly cooled and solidified, is coated with an oil agent, and is then undrawn after controlling the yarn speed using a take-up roll that rotates at a predetermined speed. It was wound as a thread.

Next, the undrawn yarn is 120"C in the first stage and 2nd stage in the 2nd stage.
The film was stretched in two stages at a temperature of 30°C. The first stage stretching ratio was 80% of the total stretching ratio, and the remainder was stretched in the second stage.

The spinning speed, total draw ratio, drawing temperature, etc. were varied to form the yarn, and the discharge amount was varied in accordance with the spinning speed and the draw ratio so that the collar of the drawn yarn was approximately 250 denier.

The spinning conditions, the obtained drawn yarn properties, and the fiber structure parameters are shown in Table 1.

Next, four of each of the obtained drawn yarns were combined to form a yarn of approximately 10
00 denier, and the upper twist and the lower twist were applied in opposite directions for 707/10 cm each to obtain a 1000/2 raw cord. This raw cord was applied with an adhesive and heat treated in a conventional manner using a dipping machine manufactured by Ritzler Corp. to obtain a dipped cord.

Heat treatment at 250°C for 140 seconds, 5% stretch at 9
). Next, the dip cord was embedded in rubber and vulcanized at 155°C for 20 minutes, and the fatigue resistance of the restored cord was determined according to JIS L1017 3°2.2.2.
Disc fatigue strength was evaluated using the Gutdrich method. Expansion rate 12.5%, compression rate 8%, rotation speed 240 O
The tenacity retention rate after treatment at rpm for 48° was determined and shown in Table 1.

It can be seen that the polyester fiber of the present invention is characterized by a unique SS curve and fiber structure parameters, and as a result, it has a low shrinkage rate, that is, good dimensional stability, and has excellent fatigue resistance when made into a cord.

〔Effect of the invention〕

The polyester fiber of the present invention has excellent dimensional stability and good durability against repeated fatigue that is subjected to relatively large deformation strain, so it can be used for bias tires for passenger cars and light trucks, tire cords, ropes, fishing nets, sewing threads, various cover sheets, etc. It is useful for belts, and particularly improves the durability of the above products.

[Brief explanation of the drawing]

FIG. 1 shows the SS of the present invention example-2, which is an embodiment of the present invention.
Show a curve.

Claims (3)

[Claims] (1) A polyester fiber consisting essentially of polyethylene terephthalate, in the stress-elongation curve determined by a fiber tensile test, the yield stress (Ys
) is 4.5 g/d or more, and the elongation rate from the yield point to breakage (E2) is 4.5 g/d or more, and the elongation rate (E2
) is 50% or more, and the initial tensile resistance (M
i) is 100 g/d or more, the terminal modulus (Mt
) is 10 g/d or less. (2) The polyester fiber according to claim 1, wherein the polyester fiber satisfies the following fiber structure parameters at the same time. Birefringence △n≧160×10＾-＾3 Density ρ≧1.395g/cm＾3 Crystal orientation fc≧0.92 Amorphous molecular orientation F≦0.90 DSC melting point Tm≧255°C (3) The strength (T/D) of the polyester fiber is 5 g/d or more, the elongation at break (E) is 10% or more, and the dry heat shrinkage rate measured at 150°C is 3% or less. The polyester fiber according to claim 1.