JPH02277811A - Hollow polyester fiber having high tenacity and modulus - Google Patents

Abstract

PURPOSE:To provide the subject hollow fiber spun in such a manner as to get a specific hollowness, having high strength and modulus and suitable to a tire-reinforcing material, a conveyor belt reinforcing material, a reinforcing material for a thermoplastic composite, etc. CONSTITUTION:The objective fiber having a hollowness of 2-45% on the cross- section, a breakage strength of >=14 g/d and an initial tensile modulus of >=210g/d can be produced by melt-spinning an ethylene terephthalate polyester having an intrinsic viscosity of 0.5-2.0 in such a manner as to form a hollow fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Applications) The present invention relates to an ethylene terephthalate polyester fiber having unprecedented high strength and high elastic modulus properties.

More specifically, the present invention relates to polyester fibers useful for applications such as tire reinforcing materials, conveyor belt reinforcing materials, and thermoplastic composite reinforcing materials.

(Prior Art) Conventionally, methods for obtaining high strength and high elastic modulus polyester fibers have been disclosed, for example, in JP-A-63-12715, JP-A-63-99322, JP-A-63-1967ti, and JP-A-63-1967ti. Publication No. 1986-1.96712, Japanese Patent Publication No. 63-1983
-196713 etc. have been proposed. Unexamined Japanese Patent Publication 1986
Publication No. 12715 discloses that a polymer having an intrinsic viscosity IV of 1.2 or more is dissolved in a trifluoroacetic acid/methylene chloride mixed solvent to prepare a spinning stock solution, which is then spun into an undrawn yarn.
It has been shown that high strength and high modulus polyester fibers can be obtained by hot drawing. JP-A No. 63-99322 discloses that a spun undrawn material is subjected to a swelling treatment and then stretched to a total draw ratio of 6 times or more to obtain a high-strength, high-modulus polyester fiber. ing. In JP-A No. 63-196711, the authority viscosity IV is 1.2.
It has been shown that high-strength, high-modulus polyester fibers can be obtained by spinning the above polymers under specific conditions, subjecting the undrawn product to swelling treatment, and then subjecting it to multistage hot drawing.

Moreover, in JP-A-63-196712, the intrinsic viscosity I
By spinning and drawing a polymer with a V of 1.2 or more under special conditions, the number of folded molecular chains is reduced and the number of tie molecules connecting crystals is significantly increased, resulting in a fiber structure with high strength and high modulus of elasticity. It is disclosed that JP-A No. 63-196713 discloses that the intrinsic viscosity [1
is 0.5 or more and less than 1.2 to obtain an undrawn yarn with a birefringence of 0.002 to 0.060 by melt-spinning, which is then subjected to swelling treatment and then multistage hot stretching to produce high strength and high elasticity. This paper describes a method for producing polyester fibers.

(Problems to be Solved by the Invention) In general, it is preferable that high strength is required for fibers for industrial materials, such as fibers for tire cords that reinforce rubber, but the current polyethylene terephthalate fibers for tire cords The cutting strength is about 9 (g/d), the initial tensile modulus is 130 to 150 (g/d), and 13
Polyethylene terephthalate fibers with an initial tensile modulus of less than 0 (g/d) have a small reinforcing effect on rubber, so
Not commonly used.

Under these circumstances, as described above, many techniques have been proposed for improving the performance of ethylene terephthalate polyester fibers. However, the proposed method has the following problems.

First, the method described in JP-A-63-12715 requires dissolution of the polymer and recovery of the solvent, and furthermore, the productivity is low considering the spinning speed and other factors.

In addition, the method described in JP-A-63-99322 yields polyester fibers with high strength and high elastic modulus when the intrinsic viscosity IV of the undrawn yarn is as high as 1.45, but
When V is about 0.95, although this is a good value compared to conventional polyethylene terephthalate fibers for industrial materials, it cannot be said that the effects of swelling treatment/high-magnification stretching are sufficiently produced.

JP-A-63-196711 and JP-A-63-19
In principle, all the methods described in Publication No. 6712 aim to achieve high strength and high elastic modulus by increasing the number of tie molecules by using a polymer with an intrinsic viscosity 1v of 1.2 or more. There is. However, as the intrinsic viscosity IV of the polymer increases, the melt viscosity also increases;
Higher temperature spinning conditions and spinning equipment with higher pressure resistance are required. Furthermore, in order to obtain undrawn yarn with a relatively low birefringence of 0.002 to 0.06, limited spinning conditions are required. Productivity is lower compared to spinning.

The method described in JP-A-63-196713 is as follows:
A polymer with a normal intrinsic viscosity (IV≦1.0) is melt-spun to obtain a relatively low-oriented undrawn yarn with a double refractive index of 0.002 to 0.06, which is then subjected to swelling treatment. High strength and high elastic modulus are achieved by stretching under specific conditions.However, although the cutting strength and initial tensile modulus are better than conventional polyethylene terephthalate fibers for industrial materials, the application 30 (g/d), which is the limit value of cutting strength and initial tensile modulus estimated by humans.
, 500 (g/d), it cannot be said that the effects of swelling treatment/high-magnification stretching are fully brought out.The present invention aims to solve the problems that cannot be achieved with the conventional techniques, and solve the problems that cannot be achieved with the conventional techniques. We have achieved high strength and high modulus of ethylene terephthalate polyester fiber, which could not be achieved with conventional ethylene terephthalate polyester fibers. The purpose is to provide a strong, high modulus ethylene terephthalate polyester fiber.

(Means for Solving the Problems) Means for solving the above problems, that is, the present invention is made of ethylene terephthalate polyester having an intrinsic viscosity IV of 0.5 to 2.0, and has a hollowness ratio of 2 to 2. It is a high-strength, high-modulus polyester hollow fiber characterized by having 45% hollow fiber, a fiber cutting strength of 14 g/d or more, and an initial tensile modulus of 210 g/d or more.

In the present invention, the ethylene terephthalate polyester polymer is melt-spun and then stretched at as high a ratio as possible, so that the polymer chains constituting the fibers of the present invention are aligned as much as possible in the fiber axis direction. As a means for such stretching, treating undrawn polyester yarn with a swelling agent enables high-magnification stretching and improves the fiber properties of the resulting drawn yarn. However, it cannot be said that the cutting strength that is commensurate with the increase in the draw ratio due to the swelling treatment has been developed. It was discovered through research by the inventors of this application that this is a defective portion. As a result of intensive research into removing such defective parts, we were surprised (
Significantly, it has been found that a significant improvement in cut strength is achieved by forming hollow fibers during the melt spinning step.

The polyester constituting the fiber of the present invention is one in which 85 mol% or more of its repeating units are composed of ethylene terephthalate units, and in particular polyethylene terephthalate produced from teretutaric acid or its functional derivative and ethylene glycol is the main target. do. however,
15 mol% of part of terephthalic acid or its functional derivative, which is an acid component constituting polyethylene terephthalate.
For example, isophthalic acid, adipic acid, sebacic acid,
Azelaic acid, naphthalic acid, p-oxybenzoic acid, 2
．． Replacement with at least one difunctional acid such as 5-dimethylterephthalic acid, or a functional derivative thereof, or a portion of the glycol component ethylene glycol with less than 15 mol % of eg diethylene glycol, 1. It may also be a copolymer in which a small amount of dihydric alcohol such as 4-butanediol is replaced with one type, and polyester antioxidants, flame retardants,
It is also possible to contain adhesion improvers, erasing agents, coloring agents, etc.

Although the upper limit of the intrinsic viscosity rv of the ethylene terephthalate polyester used in the present invention is not particularly limited, it is desirable that IV is less than 2.0, taking into account the melt viscosity and related spinning equipment and spinning conditions. .

It should be noted that if the intrinsic viscosity IV of the ethylene terephthalate polyester used is less than 0.5, it will be difficult to produce the high-strength, high-modulus polyester fiber that is the object of the present invention.

The method of the present invention spins hollow fibers using a polymer with an intrinsic viscosity of IV, which is normally used in the production of fibers for industrial materials, and further improves the effectiveness of conventional methods applied to the production of high-strength, high-modulus polyester fibers. A new manufacturing method was achieved by Fukagawa. That is, after swelling an undrawn yarn having a hollow part at the center of the cross section of the fiber, multi-stage hot stretching results in a high strength of 210 (g/d) or more of 14 (g/d).
It has been discovered that the above-mentioned high elastic modulus can be obtained at the same time, leading to the present invention. Hereinafter, the method for producing the novel ethylene terephthalate polyester fiber of the present invention and the characteristics of the fiber will be described in more detail.

Intrinsic viscosity treated with vacuum drying! A raw material polyester having a V of less than 2.0 is melt-extruded at a temperature higher than the melting point of the polymer, preferably lower than the melting point of the polymer (both higher than the melting point of the polymer by 20° C. or higher).

The melt extrusion method is not particularly limited, but an extruder type extruder, a piston type extruder, a twin screw kneading type extruder, etc. are used. A melted polymer is discharged from a melt extruder through a spinneret having a plurality of spinning holes arranged in a shape that allows the fiber after stretching to have a hollowness ratio of 2 (%) or more and less than 45 (%). The shape of the spinning hole is not particularly limited, but it is preferably C-shaped and annular with a cutout at one point. It is important to set the spinning conditions by considering these factors, such as the spinning temperature and the temperature and flow rate of the cooling air stream that is blown onto the yarn immediately after discharge.

Even if the undrawn yarn is subjected to swelling treatment so that the hollowness ratio of the fiber after drawing is less than 2 (%), and then subjected to multi-stage hot drawing, the non-uniformity of the structure within the cross-section of the fiber cannot be resolved and the physical properties cannot be improved. It becomes difficult.

In addition, undrawn fibers with a hollowness ratio of 45% or more after drawing may cause anisotropy in the fiber cross section during the cooling and solidification process immediately after being discharged, and it is difficult to form hollow parts. There are problems such as oxidation, which ultimately becomes an obstacle to achieving high physical properties.

Therefore, the hollowness ratio needs to be 2 (%) or more and less than 45 (%), preferably 5 (%) or more and less than 40 (%).

The undrawn polyester yarn melted and discharged in this way is cooled and solidified, and after being coated with an appropriate amount of oil, it is taken off by a take-off roller that controls the yarn speed.

The take-up speed is not particularly limited, but it is set so that the natural stretching ratio NE of the undrawn yarn is 200 (%) to 250 (%) after considering the spinning hole dimension and polymer discharge conditions. It is preferable to do so.

If the natural stretch ratio is less than 200 (%), the effect of improving the stretchability by the subsequent swelling treatment will be small, and as a result, it will be difficult to improve the physical properties. When the natural draw ratio exceeds 250 (%), the spinning state becomes extremely unstable and it becomes difficult to suppress the formation of irregularities in the longitudinal direction of the yarn.

After the yarn is once wound up, or following spinning, it is immersed in an fg liquid that swells the polyester. Any swelling solution may be used as long as it swells the fiber without dissolving the fiber itself and enables high-magnification stretching, but an acetone/water system (water content O~50ν01χ) is particularly suitable. preferable.

The swelling treatment time is set so that the appearance of the yarn turns white and crystallization is completed at a constant temperature of 0°C or higher, preferably 10°C or higher. The processing speed can be controlled by changing the processing temperature and the swelling agent concentration in the swelling solution.

The thus-swelled undrawn polyester yarn is drawn at a temperature of 90° C. or lower and at the maximum magnification at which deformation and thinning are predominant in the drawing heater. If the stretching heater temperature exceeds 90°C, thermal crystallization proceeds before stretching, which impairs stretchability, which is not preferable.

Following the low-temperature stretching, high-temperature stretching is performed within a temperature range of 150 to 250°C. Multi-stage stretching is preferred for high-temperature stretching, and first, stretching is carried out at a temperature range of 150 to 200°C and at least 95% of the maximum stretching ratio. Here, the maximum stretching ratio is 100
It refers to the maximum stretching ratio at which a sample of 0 m or more can be continuously and stably reeled.

Next, it is preferable to carry out stretching at a temperature as high as possible in the temperature range of 200 to 250'C.

(Function) The characteristics of the polyester fiber of the present invention will be explained with reference to the drawings. FIG. 1 is a diagram showing a cross section of a polyester fiber of the present invention, and FIG. 2 is a diagram showing a cross section of a polyester fiber of a comparative example.

As shown in FIG. 2, the central part of the fiber cross section of the comparative example appears blackened, indicating that there is a large density difference between the inner and outer layers within the fiber cross section. Because the central part of the cross section of the fiber is blackened, the density of the central part of the cross section is significantly lower than that of the outer layer, and the central part of the cross section has a relatively rough void shape.
It is presumed that the fiber properties of this part are quite low since it contains structural units.

On the other hand, FIG. 1 shows a cross section of the polyester fiber of the present invention, and there is no blackened portion in the cross section of the fiber as seen in the photograph of the cross section of the polyester fiber of the comparative example. In other words, the blackened area at the center of the cross section of the fiber is thought to be a phenomenon that occurs as a result of the swelling agent penetrating into the fiber during the swelling process. It is judged that the outbreak has been suppressed. This is presumed to bring about performance improvement effects such as high strength and high elastic modulus.

(Examples) Examples are shown below, but the present invention is not limited to these examples. The method of measuring physical property values used for evaluation of the present invention is as follows.

<Measurement method of intrinsic viscosity IV> In the present invention, the intrinsic viscosity [V] of the ethylene terephthalate polyester is the intrinsic viscosity [η] measured at 30°C using a P-chlorophenol/tetrachloroethane-3/1 mixed solvent. ] was converted into the intrinsic viscosity IV of phenol/tetrachloroethane=60/40 using the following formula.

IV=0.8325 Fineness measuring device DENIERCOMPUT [! The fineness (denier, d) of single fibers was measured using RDC-11B model.

However, the fiber measurement sample length was 501n11.

(Measurement method of fiber strength) The tensile strength (strength) of fibers is determined according to JIS-L-1013 (1
In accordance with 7.5.1 of 981), in a test room under standard conditions, a constant speed extension type universal tensile tester TE manufactured by Toyo Baldwin ■ was used.
Tensile strength of single fibers was measured using NSILON UT) l-DI.

However, the measurement conditions were as follows: using a 5 kgf tensile load cell,
The sample was pulled at a gripping interval of 10 CII and a tensile speed of 110 Cl/min (an extension rate of 100% of the gripping interval per minute) and a recording paper feed rate of 100 CII/min, and the load (gf) when the sample was cut was measured. The tensile strength (g
f/d) was calculated and set as strength (g/f).

Measuring method of initial tensile modulus of fiber> The initial tensile modulus of fiber (initial tensile modulus) is
[, -1013 (1981), 7.5.1, the test was carried out using the same method as the above method for measuring fiber strength, and a load-elongation curve was drawn on the recording paper. From this figure, JIS-L-
1013 (1981), 7.10, the initial tensile modulus (gf/d) was calculated and set as the initial tensile modulus (g/f).

Cross-sectional observation method of fibers> After embedding the sample in resin and cutting it to a thickness of several tens of microns using a microtome,
Observe under a magnification of 2x, or insert a sample into a through hole filled with black Toughcell cotton, cut with a razor blade, and observe under a magnification of 200 to 600x using an optical microscope.

Example 1 A polyethylene telescrate raw material polymer with an intrinsic viscosity IV of 1.0 was produced using an extruder type small spinning machine.
Under the conditions of 95°C single hole discharge IF 0.75g/win, the third
C-shaped spinning pore (a/b = 0.22, a
=0.40mm, b =1.80mm, c =0.18
mn+), 20"C, 0,
After cooling and solidifying with a quench air flow of 3m/1lin,
Approximately 1 (%) oil agent is applied and the speed is 200+s/m1ri.
I wound up the yarn. Natural stretching ratio of the obtained yarn: 23
It was 5 (%).

The undrawn yarn was immersed in acetone (containing 1.Qvol x of water) at 50'C for 3 minutes, and then the treatment system was soaked at 80'C.
Stretching was performed 3.75 times at a temperature of C (stretching speed 1,
On/a+in), the maximum stretching ratio of 95 at 185°C
%, and then three stages of stretching at 245°C.

The hollowness ratio of the obtained drawn yarn was 12.5 (%), the fiber physical properties were 2.8 denier, the cutting strength was 14.1 (g/d), the initial tensile modulus was 220 ('g/d), and the fiber limit was Viscosity 0.
It was 88.

Example 2 Natural stretching was carried out under the same spinning and winding conditions as in Example 1 using a spinneret with a dimension a/b of 0.14 for a C-shaped annular spinning pore with a missing part at one location. The magnification is 238 (%
) was obtained, and the undrawn yarn was immersed in acetone for swelling treatment under the same conditions as in Example], followed by multistage hot stretching. The hollowness ratio of the obtained drawn yarn was 23.
3 (%), its fiber fineness is 2.9 denier, and its cutting strength is 15.1. (g/'d), initial tensile modulus 238 (
g/d), and the intrinsic viscosity of the fiber was 0.88.

Comparative example 1. Dimensions a/b and c of a C-shaped circular spinning pore with a cutout at one location are 0.08 and 0.40 m, respectively.
An undrawn yarn with a natural draw ratio of 210 (%) was obtained under the same spinning and winding conditions as in Example 1 using a spinneret changed to M. The undrawn yarn was immersed in acetone to undergo swelling treatment under the same conditions as in Example 1, and then subjected to multistage hot stretching. The obtained drawn yarn is a deformed yarn with a C-shaped cross section and has a fiber fineness of 2.9 denier and a cutting strength of 10.1 (g
/d), the initial tensile modulus was 150 (g/d), and the intrinsic viscosity of the fiber was 0.88.

Comparative Example 2 A polymer with an intrinsic viscosity Iv of 1.0 was melted and discharged using a spinneret with a normal circular cross section and a spinning pore with a diameter of 0.3 m, and a natural stretching ratio of 237 (%) was applied at a speed of 250 m/min.
) was wound up. The yarn was subjected to swelling treatment under the same conditions as in Example 1, and then subjected to multi-stage hot stretching. The resulting drawn yarn had a fiber fineness of 2.8 denier and a cutting strength of 13.
4 (g/d), the initial tensile modulus was 197 (g/d), and the limiting viscosity of the fiber was 0°87.

Example 3 Intrinsic viscosity IV1. Using a small extruder type spinning machine, the polyethylene terephthalate raw material polymer of
Undrawn yarns with various hollow ratios were prepared under the same spinning and winding conditions as in Example 1, except that dimensions a and C of the C-shaped annular spinning hole shown in FIG. 3 with missing circular portions were changed. Each undrawn yarn was immersed in acetone to undergo swelling treatment under the same conditions as in Example 1, and subsequently subjected to multi-stage hot drawing.

The physical properties of the obtained drawn yarns having various hollow ratios are shown in Experiments Nα1 to Nα5 in Table 1 below. Experimental floor 5 had a hollow ratio of 48%.
However, it was difficult to spin and draw the yarn, and a satisfactory yarn could not be obtained.

Table 1 (Effects of the Invention) The fibers of the present invention have high physical properties never seen before, such as a breaking strength of 14 (g/d) or more and an initial tensile modulus of 210 (g/d) or more. It is a polyester fiber and is extremely useful as an industrial material.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a cross section of the fiber of the present invention, and FIG. 2 is a diagram showing a cross section of a drawn system obtained in Comparative Example 2. FIG. 3 shows an example of a cross-sectional view of a C-shaped annular spinneret hole having a cutout at one location for obtaining hollow fibers. a: Width of the spinning hole b: Diameter of the outer circle of the spinning hole of the hollow circular polymer C: Spinning gap of the hollow internal polymer Patent applicant Toyobo Co., Ltd. No. I! ! 1 early 2 figures early 3 figures

Claims (1)

[Claims] (1) Made of ethylene terephthalate polyester with an intrinsic viscosity IV of 0.5 to 2.0, and a hollow ratio of 2 to 2 in the cross section.
45% hollow fiber, fiber cutting strength 14g/d
A high-strength, high-modulus polyester hollow fiber having the above properties and having an initial tensile modulus of 210 g/d or more. However, the hollowness ratio is a value determined by the following formula. Hollowness ratio = (hollow area of fiber cross section/total area of fiber cross section including hollow portion) x 100