JPH03137226A - High strength, high modulus fiber with excellent fatigue resistance - Google Patents

Abstract

PURPOSE:To provide the title fiber useful for friction materials, etc., consisting of a polymer made up of specific recurring unit as the sheath component and another polymer capable of forming anisotropic molten phase as the core component. CONSTITUTION:The objective fiber consisting of (A) as the core component A, an aromatic polyester capable of forming anisotropic molten phase and (B) as the sheath component, a polymer with recurring constituent of formula I (R1 to R4 are each H, alkyl or halogen) accounting for >=80wt.% of the total constituent units with the cross section area for the component B accounting for 5-40% of that for said fiber. For example, it is preferable that the polyester for the core component be made up of recurring constituents of formulas II and III, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a high-strength, high-modulus fiber with excellent fatigue resistance.

(Prior art) 1- Various techniques for obtaining organic high-strength, high-modulus fibers have been studied, and in order to increase the strength and modulus of elasticity, traps have been developed to highly orient polymer molecular chains in the direction of the fiber axis. It is known to be effective. For example, in spinning nylon fibers and polyester fibers, it is possible to increase the tensile strength and tensile modulus of the resulting drawn yarn by changing the draw ratio in the drawing step. This is due to stretching,
This is because the degree of molecular orientation of the crystalline and amorphous portions constituting the fiber increases.

In addition, it is well known that para-oriented aramid fibers (such as Kevlar) can achieve high elastic modulus and strength by simply discharging them from a spinneret, removing the solvent, and winding them without going through a stretching process. (For example, Japanese Patent Publication No. 47-2489)
. This is also thought to be because the spinning stock solution forms a liquid crystal structure under specific conditions, and when it is discharged from the hole of the spinneret, the liquid crystals are aligned in the fiber axis direction due to frictional stress (polymer molecular chains become highly oriented). .

Recently, by melt-spinning aromatic family-based copolyester polyester (bolyarylate) that forms liquid crystals when heated and melted, forming highly oriented fibers, and then proceeding with solid phase polymerization by heating for a long time, It is also known that fibers with high strength and high elastic modulus can be obtained (for example, JP-A-61
-174408).

(Problems to be Solved by the Invention) According to the above-mentioned fiberizing method, especially spinning from liquid crystal, organic fibers having significantly higher strength and elastic modulus than conventional general-purpose synthetic fibers can be obtained. In both cases, the polymer molecular chains are highly oriented in the fiber axis direction. On the other hand, in the cross-sectional direction perpendicular to the fiber axis, only weak intermolecular forces act, resulting in a mechanically weak fiber structure. in this way,
In order to increase the strength and elastic modulus of fibers, when the degree of orientation of polymer molecular chains is extremely improved, fibrils develop in the fiber axis direction. Since the interaction between fibrils is small, durability becomes a problem in applications where the material is subjected to repeated bending deformation or frictional loads.

Nylon fibers and polyester fibers exhibit relatively excellent durability against bending, deformation, and friction, but their tensile strength and
Mechanical properties such as elastic modulus are significantly lower than liquid crystal fibers.

In the field of industrial materials such as ropes, hoses, cords, belts, sewing threads, and fishing nets, fiber materials with higher strength and elasticity than conventional general-purpose polymer fibers (vinylon, acrylic, nylon, polyester, etc.) are required, and in response to this demand. Various high-performance fiber materials have been developed, but all of them have problems in terms of durability with respect to fatigue.

The present inventors have conducted extensive research into fibers that have excellent fatigue resistance such as bending deformation and friction while maintaining the above-mentioned high strength and high modulus, and have discovered the present invention.

The present invention will be described in more detail and specifically below.0 (Means for Solving the Problems) The present invention is characterized in that the core component A is an aromatic polyester capable of forming an anisotropic melt phase, and the sheath component B is an aromatic polyester capable of forming an anisotropic melt phase. % or more of the following structure (I) is a composite fiber consisting of a polymer 4-mer consisting of repeating units, and the area ratio B/(A + B) of the B component in the cross section of the fiber is 0.05 to 0. , 4, and is a high-strength, high-modulus fiber with excellent fatigue resistance.

The aromatic polyester capable of forming an anisotropic melt phase as used in the present invention refers to polymers obtained from aromatic diols, aromatic dicarboxylic acids, aromatic hydroxycarboxylic acids, etc., which exhibit optical anisotropy in the melt phase. (liquid crystallinity).

Such characteristics can be easily recognized by heating a sample on a hot stage in a nitrogen atmosphere and observing the transmitted light.

The anisotropic melt component A used in the present invention consists of a combination of repeating components shown below.

5-6- Component B is a polymer in which 80 or more by weight consists of repeating units of the following structure (I).

Particularly preferred are polymers in which the proportion of repeating structural units of (uL (III)) shown below is 65% by weight or more, particularly R1 in which the component (I [I) is 5 to 45%].
．． &, As a specific example of R3, R4, -CH5
.

-CH2CH3, -CH2CH2CH3, -CH2CH
3, -F, -Ql, Br.

Examples include Ha-H. Particularly preferred is an aromatic polyester in which R1 to R4 are -H.

Component A may contain other polymers or additives as long as its strength is not substantially reduced.

7- It may contain polymers and additives, but its melting point is 18
It is preferable that it is 0-320 degreeC.

The composite fiber referred to in the present invention is one in which the core component consists of the above-mentioned A component and the sheath component consists of the above-mentioned B component, and the area ratio of the sheath component (B component) in the cross section is B/(A + B). It is in the range of 0.05 to 0.4, preferably 0.05 to 0.3. The area ratio is determined from the areas of the core and sheath portions determined from a microscopic photograph of the cross section of the fiber structure 8. If the area ratio is less than 0.05, the cover by the sheath component will not be sufficient, and the sheath component will be exposed or easily peeled off due to friction and abrasion.

On the other hand, if it exceeds 0.4, the ratio of the core component decreases, resulting in a decrease in strength and elastic modulus, which deviates from the gist of the present invention.

Composite fibers can be obtained by spinning in a known manner, for example in the apparatus shown in FIG. The preferable conditions for the core component are that the spinning temperature is at least 10°C higher than the higher melting point of each component A, B, and the shear rate (Te) at the time of discharge to obtain a high degree of orientation. It is preferable to make it 103BeC'' or more.

The shear rate (r) referred to in the present invention refers to the nozzle diameter r (cn
l), polymer discharge amount per single hole is Q (77sec
) is calculated when

The cross-sectional shape of the composite fiber is a simple core-sheath type, as well as a Various types are possible, as shown in Figure 2.

The conjugate fiber of the present invention has molecular chains aligned in the fiber axis direction during spinning and extrusion and already exhibits sufficient strength and elastic modulus, but the performance can be further improved by heat treatment and stretching heat treatment. The heat treatment can be carried out in an inert atmosphere such as nitrogen, an active atmosphere containing oxygen such as air, or under reduced pressure.

Preferred temperature conditions are M, where MP is the melting point of component A.
A pattern in which the temperature is gradually increased from below MP-40°C within the range of P-60°C to MP+20°C is more preferable. The processing time can range from several seconds to several tens of hours depending on the desired performance.

When heat is supplied using a medium such as gas, there are methods such as using radiation from a heating plate, infrared heater, etc., methods by contacting with a heat roller, plate, etc., and internal heating methods using high frequency, etc. .

Processing is carried out under tension or without tension, depending on the purpose. The shape of the treatment may be a skein, a cheese, a tow (for example, placed on a wire mesh, etc.), or continuous treatment between rollers. The fiber can be either a filament or a cut fiber.

It is convenient to carry out the stretching at a temperature that is 60° C. or more lower than the melting point of component A and a cutting elongation of 10 to 60 inches.

Although the elastic modulus is improved by this treatment, the present invention uses a molten liquid crystal polymer for the core component and a polymer of the structural formula (I) for the sheath component, thereby increasing the maximum of the fiber made of the molten liquid crystal polymer as the core component. It maintains the characteristics of high strength, high modulus of elasticity, dimensional stability, and heat resistance, while significantly improving the major drawbacks of surface fibrillation, compression fatigue resistance, and abrasion resistance.

Examples of industrial applications using the fiber of the present invention include the following.

1. For resin reinforcement (composite with carbon and glass fiber) K
Things used Skis, golf club and gateball heads and shafts, tennis and badminton racket frames,
Helmets, bats, glasses frames, printed circuit boards,
Primary or secondary structures such as motor rotor slots, insulators, pipes, high-pressure vessels, automobiles, motorcycles, two-wheeled vehicles, trains, ships, airplanes, spacecraft, etc. 2 Things used for rubber reinforcement Tires, belts , Various timing belts, rubber reinforcing materials for hoses 3, Items used in valve shapes 1) Wear materials (mixed with other fibers, reinforcing resin), brake linings, clutch facings, bearings 2) Other packing materials, Gaskets, filter media, abrasive materials4, cut fibers Used in chopped yarn form Paper (insulating paper, heat-resistant paper), vibration materials for speakers, cement reinforcing materials, resin reinforcing materials5, filaments, spun yarn Used in yarn form Tension members (optical fibers, etc.) Loafs, cords, cables, lifelines, fishing lines, wire extensions6, woven or knitted items Bulletproof vests, safety gloves, safety nets, heat-resistant and flame-resistant clothing, aprons, etc. Protective equipment, Examples include the lining of automobiles, trains, ships, airplanes, spacecraft, etc.

Fibrillation according to the present invention means passing the yarn through three titanium guides under a tension of 100 m/ml.
The amount of fibrils adhering to the guide when the fibrils were shortened for 1 hour at n was evaluated as 1 for a large number of fibrils, 0 for no fibrils at all, and Δ for an intermediate.

The fatigue resistance strength retention rate referred to in the present invention is 1500 dr.
(500 drx 3 yarns), first twist 280 T/m
.

A double yarn with a ply twist of 280 T/m was made into a cord, and the cord was embedded in rubber and evaluated by the strength retention rate after being processed 250,000 times using a belt bending test method.

The abrasiveness referred to in the present invention refers to 10 sample yarns lined up,
Twist the yarn 1.5 times between the reversing rotating body and the pulley at the other end, set it in a figure 80 shape, apply a load of 3 wheels to the pulley, wear the yarn back and forth on the reversing rotating body, and calculate the number of times it takes to break. A diameter of 10o with inter-wear and a load of 1/10t/d applied.
A grinder abrasion test was conducted using a ++ round whetstone (rotation speed: 13-100 minutes, contact angle: 100 degrees), which was determined by the number of times until the material broke.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited thereby.

Example I As component A, the structural units (n) and (III) are 73/
A wholly aromatic polyester polymer having a predominant molar ratio of 27 was used. As for the physical properties of this polymer, the logarithmic viscosity (η1nh) was determined as follows.

Dissolve the sample in pentafluorophenol (60 to 80°C) in a constant temperature bath at 60°C using an Ubbelohde capillary viscometer (for example, the Polymer Society of Japan, ed. 6 Polymer Scientific Experimental Methods 1, Tokyo Kagaku Doujin P179 (I986), Tokyo). ). The solvent flow time is 107 seconds.

The melting point (Mp) of Polymer A is TA-3 manufactured by Mettler.
This is the endothermic peak temperature determined by 000DSC.

Component B consists of a structure in which all of the structural units of (I) are -H at 280°C and at 1000 s.
A polymer having a viscosity of 400 voids at ec'' was used.

The composite ratio (weight ratio) of component A and component B is 7/3, which is the first
The material was discharged from the 100-hole nozzle shown in the figure at a spinning temperature of 320°C. Winding speed is 500m/min and 500dr/1
A filament of 00f was obtained.

This spinning yarn is wound around a perforated aluminum bobbin at a density of 0.62
? /cc, 3 hours at 240℃, 2 hours from 260℃
Heat treatment was performed in a trench at 80°C for 4 hours and from 280°C to 285°C for 10 hours.

The physical properties of the obtained fibers are shown in Table 1.

Examples 2 to 5 Various heat treatment systems were obtained in essentially the same manner as in Example 1, except that the composite ratio of polymers A and B in Example 1 was varied and the yarn denier was changed. The results are listed in Table 1.

Comparative Example 1 The A component of Example 10 was used alone (B component O) and was spun under the same spinning conditions and heat treated.

None of the examples of the invention caused any fibrillation, indicating a significant improvement in the fiber surface.

The effect of the present invention is most evident in fatigue resistance. This is presumably because the presence of the sheath component suppresses the compression fatigue of the core component.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of essential parts of an example of a spinneret for obtaining the conjugate fiber of the present invention, and FIG. 2 is an example showing the cross-sectional shape of the conjugate fiber of the present invention.

Claims (1)

[Claims] The core component A is an aromatic polyester capable of forming an anisotropic melt phase, and the sheath component B is 80% by weight or more of the following structure (I)
is a conjugate fiber made of a polymer consisting of repeating units, and the area ratio of component B to the cross section of the fiber is B/(A
A composite fiber characterized in that +B) is 0.05 to 0.4. ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(I) In the formula, R_1, R_2, R_3, and R_4 are hydrogen, an alkyl group, or a halogen atom.