JPH04272226A - High-tenacity high-modulus conjugate fiber - Google Patents

Abstract

PURPOSE:To obtain the subject fiber having high strength and modulus and improved abrasion resistance, compressive fatigue resistance, etc., by using a core component consisting of an aromatic polyester capable of forming an optically anisotropic molten phase and a sheath component consisting of an oriented and crystallized flexible polymer. CONSTITUTION:The objective fiber is composed of (A) a core component consisting of an aromatic polyester capable of forming an optically anisotropic molten phase and (B) a sheath component consisting of an oriented and crystallized flexible polymer. The component A is preferably a polymer containing >=65wt.% of segments composed of the units of formula I and formula II, especially an aromatic polyester containing 5-45wt.% of the component of formula II. The component B is preferably polybutylene terephthalate, polyethylene terephthalate, etc. when the component A is a copolymer of the units of formula I and formula II.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to high-strength, high-modulus fibers with excellent fatigue resistance and dyeability. The fibers of the present invention are used not only for general industrial materials, but also for sports, protective clothing, etc. It is also widely used in the field.

0002

[Prior Art] Research and development of molten liquid crystal polymers has been active, and high strength and high elastic modulus fibers made by melt spinning these polymers are known (for example, Japanese Patent Application Laid-Open No. 1986-17
Publication No. 4408).

0003

[Problems to be Solved by the Invention] According to the above-mentioned fiberization method, that is, spinning from molten liquid crystal, it is possible to obtain organic fibers having significantly higher strength and elastic modulus than conventional general-purpose synthetic fibers. 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, the strength of the fiber,
In order to increase the elastic modulus, 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.

On the other hand, nylon fibers and polyester fibers made of flexible polymers exhibit relatively excellent durability against bending deformation and friction, but their mechanical properties such as tensile strength and elastic modulus are inferior to those of liquid crystal fibers. Then it is noticeably lower. To solve these problems, composite fibers can be considered, for example, in which the sheath component is a flexible polymer such as polyester or nylon, and the core component is a liquid crystal polymer, but the liquid crystal polymer in the core component cannot be stretched substantially. As a result, the sheath component polymer was in an unoriented and substantially non-crystallized state, and its original performance was not exhibited, and the core-sheath peeled off due to simple abrasion, making it unusable for practical use.

[0005] The present inventors have conducted extensive research into oriented crystallization of a sheath component made of a flexible polymer without stretching, and have discovered the present invention. Hereinafter, the present invention will be explained in more detail and specifically.

[0006]

[Means for Solving the Problems] The present invention provides a high-strength, high-elastic modulus comprising a core component of an aromatic polyester capable of forming an optically anisotropic melt phase and a sheath component of a flexible polymer having oriented crystallization. It is a composite fiber.

The aromatic polyester capable of forming an anisotropic melt phase as used in the present invention is a polymer obtained from an aromatic diol, an aromatic dicarboxylic acid, an aromatic hydroxycarboxylic acid, etc., and exhibits optical anisotropy in the melt phase. It shows orientation (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.

[0008]

[Chemical formula 1]

[0009] Further, the above-mentioned repeating component may be copolymerized with 10 mol% or less of other components. Particularly preferably, the portion consisting of the following repeating structural units (E) and (F) is 65
Aromatic polyesters in which the component (F) accounts for 5 to 45% by weight are particularly preferred.

0010

[Case 2]

[0011] Component A may contain other polymers or additives as long as its strength is not substantially reduced. The flexible polymer referred to in the present invention is a polymer having fiber-forming ability such as polyolefin, polyamide, polyester, polyarylate, polycarbonate, polyphenylene sulfide, and polyester ether ketone. As a preferable sheath component, at the spinning temperature of the core component,
It is a polymer that can be composite-spun without decomposition, etc. When a copolymer of [E] and [F] is used as the core component, polybutylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polyester Ether ketones, etc. Additives commonly used in these sheath component polymers (
(pigments, carbon, heat stabilizers, ultraviolet absorbers, lubricants, fluorescent whitening agents, etc.) may also be included.

[0012] A preferred composite ratio of the composite fiber according to the present invention is in the range of B/(A+B) = 0.05 to 0.6, where A is the cross-sectional area of the core component and B is the cross-sectional area of the sheath component. be. 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. If the area ratio is less than 0.05, the covering by the sheath component will not be sufficient, and a portion of the core may be exposed or the sheath component may peel off easily due to friction or wear. If it exceeds this, the ratio of the core component decreases, resulting in a decrease in strength and elastic modulus, which may deviate from the spirit of the present invention.

In the present invention, the term "orientated crystallization" of the sheath component polymer means that when the fibers are arranged in parallel and wide-angle X-ray diffraction is performed, there is no halo or ring-shaped diffraction pattern, but clearly microcrystals. The purpose is to provide a fiber diagram showing the orientation of the fibers. A wide-angle X-ray diffraction image of a fiber with significantly low oriented crystallinity shows a diffuse amorphous halo, and as oriented crystallization progresses, the amorphous halo becomes concentrated in the equator direction. The appearance of such anisotropy is thought to be due to the formation of a structure called an oriented intermediate phase, which develops and shifts to an oriented crystallized structure. In order to clarify the oriented crystallization referred to in the present invention, as a practical and simple method for determining the degree of crystal orientation, the following fc has been proposed by Kure, Kubo et al.
It can be shown as That is, the half-width H of the intensity distribution measured along the Debye ring of the strongest reflection on the equator line is determined and calculated using the following equation. fc=(180-H)/180 Oriented crystallization as used in the present invention refers to fc of 0.7 or more.

[0014] Oriented crystallized fibers are obtained by the following method. Composite fibers can be obtained by known methods, for example in FIG.
The fibers are spun using the following equipment. The cross-sectional shape may be any shape as shown in FIG. 2, as long as the sheath component substantially covers the surface. The spinning temperature is preferably 10° C. or more higher than the higher melting point of each component of the core and sheath. In order to obtain a high degree of orientation, the core component preferably has a shear rate (γ) of 103 sec-1 or more during discharge. More preferably 104sec-1
That's all. The shear rate (γ) referred to in the present invention refers to the nozzle diameter r (cm) and the polymer discharge amount per single hole Q (cm).
3/sec), it is calculated as γ=4Q/πr3(sec-1).

According to studies conducted by the present inventors, the core component hardly undergoes reorientation due to the spinning draft (D), and only the sheath component, which is a flexible polymer, undergoes rapid orientation due to the draft. The spinning draft (D) according to the present invention is a value expressed by the following formula. D=Vt/Vo, where Vo: discharge speed of polymer exiting the nozzle (m/
(min) Vt: Spin take-up speed (spinning speed) (m/min) In order to obtain the fiber of the present invention, it is preferable that D>30. Furthermore, in order to obtain a composite fiber in which the sheath component of the present invention is oriented and crystallized, the spinning speed is an important factor, and although it varies depending on the oriented crystallization speed of the sheath component polymer, for example, in the case of polyethylene terephthalate, Vt > 4000 m. /min, polyethylene naphthalate has a Vt>5000 m/min, and polyphenylene sulfide has a Vt>2500 m/min.

The composite fiber of the present invention already has sufficient strength and elastic modulus after being spun, but its performance can be further improved by relaxing heat treatment or tension 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. The heat treatment atmosphere is preferably a gas having a dew point of -40°C or lower. Preferred temperature conditions include a pattern in which the temperature is gradually increased from below the melting point of the sheath component and below the melting point of the core component -40°C. The processing time can range from several seconds to several tens of hours depending on the desired performance.

[0017] When heat is supplied using a medium such as gas, a method using radiation from a heating plate, an infrared heater, etc., a method by contacting with a heat roller, a plate, etc., an internal heating method using high frequency, etc. etc. Processing is carried out under tension or without tension, depending on the purpose. The shape of the treatment is skein-like, cheese-like, tow-like (for example, placed on a wire mesh, etc.),
Alternatively, continuous processing between rollers is performed. The fibers can be either filaments or cut fibers. The tension heat treatment is conveniently carried out at a temperature of at least 60° C. below the melting point of the core component and at a tension of 10 to 50% of the cutting strength, which further improves the elastic modulus and fatigue resistance.

In the present invention, the core component is made of a molten liquid crystal polymer, and the sheath component is made of a flexible polymer that has been crystallized in an oriented manner. This fiber has significantly improved surface fibrillation, abrasion resistance, compression fatigue resistance, weather resistance, etc., which are the biggest drawbacks of fibers made of liquid crystal polymers.

Examples of industrial applications using the fiber of the present invention include the following. 1. Items used for resin reinforcement (composite with carbon and glass fibers) 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. Items used for rubber reinforcement Materials for rubber reinforcement of tires, belts, various timing belts, and hoses 3. Items used in pulp form 1) Wear materials (mixed with other fibers, reinforcing resin), brake linings, clutch facings, bearings 2) Other packing materials, gaskets, filter materials, abrasive materials 4. Paper used in cut fiber, chopped yarn form (insulating paper, heat-resistant paper), vibrating material for speakers, cement reinforcing material, resin reinforcing material5. Filaments, spun yarns used in the form of yarn Control cables, heater wire core yarns, tension members (optical fibers, headphone cords, etc.), ropes, cords, ropes, life lines, fishing lines, nets 6. Items used in woven or knitted form Screen gauze, conveyor belts, yacht sails, tents, membranes, bulletproof vests, safety gloves, safety nets, heat-resistant and flame-resistant clothing, protective equipment such as aprons, rubber reinforcement base fabrics, automobiles, trains, Examples include the lining of ships, airplanes, spacecraft, etc.

[0020] Fibrillation as referred to in the present invention means that the yarn is passed through three titanium guides under a tension of 100 g.
The amount of fibrils adhering to the guide when running at m/min for 1 hour was evaluated as × for a large amount, ○ for no fibrils, and Δ for an intermediate amount. The fatigue resistance and strength retention rate referred to in the present invention means that yarns of approximately 1500 dr (500 dr The strength retention rate after 250,000 times of processing was evaluated using the belt bending test method.

[0021] The abrasiveness referred to in the present invention refers to
Align the 0 wires, twist the inversion rotating body and the pulley at the other end 1.5 times, set it in a figure 8 shape, and apply a load of 3 kg to the pulley.
Interfiber abrasion, which calculates the number of times it takes to twist and break the yarn by reciprocating it with a reversing rotating body, and applying a load of 1/10 g/d to a round grindstone with a diameter of 10 cm (rotation speed: 100 times/min, contact angle: 100 The grinder wear test was evaluated in terms of the number of times it took to cut (degrees) and the number of cuts. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

[0022]

[Example] Example 1 The above structural units (E) and (F) are 73/27 as core components.
A fully aromatic polyester polymer with a mole % ratio was used. The physical properties of this polymer are: ηinh=5.6 dl/g Mp=279°C. Logarithmic viscosity (ηinh) was determined as follows. Dissolve 0.1% by weight of the sample in pentafluorophenol (60 to 80°C), and use an Ubbelohde capillary viscometer (for example, "Polymer Science Experimental Methods" edited by the Society of Polymer Science and Technology) in a constant temperature bath at 60°C.
Measured with Tokyo Kagaku Doujin P179 (1986) Tokyo). The solvent flow time is 107 seconds. ηinh=[ln(ηrel)]/C The melting point (Mp) of the core polymer is TA-
This is the endothermic peak temperature determined by 3000DSC.

As the sheath component, [η] (intrinsic viscosity measured using an Upperohde viscometer in a constant temperature bath at 30°C using a mixed solvent of equal amounts of phenol and tetrachloroethane) =
Using 0.72 dl/g of polyethylene terephthalate, composite spinning was carried out at a temperature of 310° C. using a 50-hole spindle shown in FIG. 1 at a weight ratio of core component to sheath component of 3:1. The nozzle diameter is 0.25 mmφ, and the winding speed is 4500 m/min.
A filament of 0 denier was obtained. γ=21.7×10
3sec-1, D=111 times, Vt=4500m/min, and the obtained fiber performance is strength (DT): 9.3g/d elongation (DE)
:2.3% Elastic modulus (IM) :480g/d cross-sectional area ratio
:0.25 Nodule strength (KT) :5.
6 g/d Loop strength (LT): 7.3 g/d. A rectangular sample with a thickness of about 0.5 mm was prepared by arranging this material in parallel, and a wide-angle X-ray diffraction photograph was taken. Polyethylene terephthalate, the sheath component, clearly showed an oriented crystallized fiber pattern, and the fc measured from the intensity distribution in the azimuthal direction of the (-1,1,0) plane was 0.81.

Comparative Example 1 Using the same core-sheath components as in Example 1, spinning draft D=2
A 250 denier filament was obtained in essentially the same manner, except that the winding speed was 5x and the winding speed was 3500 m/min. The properties of the obtained fibers are as follows: Strength (DT): 8.2 g/d Elongation (DE)
: 1.9% Elastic modulus (IM) : 447 g/d cross-sectional area ratio
:0.25 Nodule strength (KT) :2.
3 g/d Loop strength (LT): 4.7 g/d. When a wide-angle X-ray diffraction photograph was taken of this product in the same manner as in Example 1, the diffraction of polyethylene terephthalate consisted of a ring-shaped pattern consisting of diffuse amorphous halos. The fc measured from the intensity distribution in the azimuthal direction of 2θ=21°, which gives the maximum intensity, was 0.52, indicating that oriented crystallization was not sufficiently performed. In terms of performance, the knot strength and loop strength were significantly inferior.

Example 2 The same molten liquid crystalline polymer as in Example 1 was used as the core component, and [η] was used as the sheath component (in a constant temperature bath at 30°C using a mixed solvent of equal amounts of parachlorophenol and tetrachloroethane). Polyethylene naphthalate (intrinsic viscosity measured using an Upperohde viscometer) = 0.68 dl/g was used, the weight ratio of the core component and the sheath component was 3:1, a 50-hole cap was used, and the composite was heated at a temperature of 318°C. spun. Winding speed 630
A filament of 250 denier was obtained at 0 m/min. The spinning draft was D=173 times. The performance of the obtained fibers is as follows: Strength (DT): 10.2 g/d Elongation (DE
): 2.3% Elastic modulus (IM): 502 g/d cross-sectional area ratio
:0.25 Nodule strength (KT) :6.
2g/d Loop strength (LT): 8.7g/d. Wide-angle X-ray diffraction was performed in the same manner as in Example 1 to determine fc, which was 0.93. This yarn was placed on a net and heated at 230° C. for 10 hours and at 270° C. for 10 hours by blowing heated N2 gas from above. No change in fc was observed even after heat treatment. Table 1 shows the physical properties of the obtained fibers.

Comparative Example 2 Using the same core and sheath components as in Example 2, the winding speed was 1000 m.
A 250 denier filament was obtained in essentially the same manner except that it was run at 1/min. The performance of the obtained fibers is as follows: strength (DT): 8.8 g/d elongation (DE)
:2.2% Elastic modulus (IM) :438g/d cross-sectional area ratio
:0.25 Nodule strength (KT) :3.
2g/d Loop strength (LT): 5.9g/d. Wide-angle X-ray diffraction of this product shows that the diffraction of polyethylene naphthalate, which is a sheath component, forms a ring-shaped halo, and the fc obtained by the same method as Comparative Example 1 is 0.46.
Met. This yarn was heat treated in the same manner as in Example 2. Slight adhesion between the yarns occurred during the heat treatment, and the sheath component was peeled off during the process, resulting in some fluffy areas. In wide-angle X-ray diffraction of this fiber, the diffraction of polyethylene terephthalate is ring-shaped, indicating that it is crystallized but not oriented. Table 1 shows the performance of the obtained fibers.

[0027]

[Table 1]

In Comparative Example 2, the sheath component was not oriented and crystallized, so it was brittle and had adhesive parts, so the expected performance was not exhibited, probably because the sheath component peeled off due to wear or the like.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an example of a spinning device used for producing composite fibers of the present invention.

FIG. 2 is a cross-sectional view of a typical composite fiber of the present invention.

Claims (1)

[Claims] 1. A composite fiber whose core component is an aromatic polyester capable of forming an optically anisotropic melt phase and whose sheath component is a flexible polymer that is oriented and crystallized.