JP2003293225A - High-strength conjugate fiber and mesh cloth - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-strength and high-modulus conjugate fiber seldom causing fibrillation or sheath-core splitting, and to provide a mesh cloth comprising the same. <P>SOLUTION: The sheath/core-type conjugate fiber is such one that the core component consists of an aromatic polyester with melt anisotropy (A-polymer) and the sheath component has a sea/island structure and the sheath component ratio is 0.2-0.7. The sea component constituting said sheath component consists of polycyclohexanedimethylene terephthalate (B-polymer) ≥0.8 dl/g in intrinsic viscosity [η], while the island component consists of an aromatic polyester with melt anisotropy (C-polymer), and the island component ratio in the sheath component is 0.02-0.5. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite fiber, and more specifically to a composite fiber and a mesh cloth which have good weavability, high strength, and excellent durability and abrasion resistance. The fields of application thereof are screen gauze, filters, base fabrics for printed circuit boards, mesh-shaped conveyor belts, papermaking belts, dryer canvases, and the like.

[0002]

2. Description of the Related Art With the recent rise of the information technology (IT) industry, molding and printing of precision electronic parts using screen printing technology have become more important, and higher precision and lower cost are required. . Examples include flat display panel (FDP) formation, multilayer capacitor formation, filling hole filling method (hollow through), electrode printing, dam printing, liquid crystal sealing printing, solar cell printing, mobile phone character printing, and the like. Above all, it has been proposed to use fused anisotropic aromatic polyester fibers for improving the performance of screen gauze.

Melt anisotropic aromatic polyester fibers are known to have a high strength and a high elastic modulus, but these fibers are easily rubbed due to their highly oriented molecular chains in the fiber axis direction. There was a problem that fibrillation occurred. There is also known a method of using a core-sheath type composite fiber having a melt anisotropic polyester as a core component and polyphenylene sulfide (hereinafter abbreviated as PPS) as a sheath component, but the PPS of the sheath component is not stretched (oriented crystal). Therefore, there is a problem that the sheath is very fragile and the sheath is likely to be peeled or dropped. Therefore, in order to solve such problems,
Japanese Unexamined Patent Publication (Kokai) No. 5-230715 proposes a composite fiber in which a core component is a melt anisotropic aromatic polyester and a sheath component is a blend polymer of PPS and a melt anisotropic aromatic polyester.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
As proposed in Japanese Patent Publication No. 5, it is a fact that fibril resistance and abrasion resistance are significantly improved by using a blend polymer of PPS and melt anisotropic aromatic polyester as a sheath component. When the weaving density is increased and the bending ratio is increased, the PPS in the sheath component is brittle, so that the sheath is likely to crack at the bent portion. Further, when a particle-containing paste or the like is printed on a screen gauze using the mesh cloth, there is a problem that sheath peeling occurs. Therefore, JP-A-2002-130
In JP-A-30, it is also proposed to use polyethylene naphthalate (PEN) as a sheath component. However, PEN has a lower melting point than PPS, and the heat treatment temperature is P
There is a problem that the heat treatment takes time because it has to be lower than that of PS.

The object of the present invention is to solve the above-mentioned problems, and it is a composite having high strength and high elastic modulus in a short time efficiently, and having excellent fibrillation resistance, abrasion resistance and sheath peeling resistance. Providing fibers and mesh cloth.

[0006]

That is, the present invention provides a core-sheath type composite fiber having a core component made of a melt anisotropic aromatic polyester (A polymer) and a sheath component having a sea-island structure. Is 0.2 to 0.7, and the sea component constituting the sheath component is made of polycyclohexanedimethylene terephthalate (B polymer) having an intrinsic viscosity [η] of 0.8 dl / g or more, and the island component is melted. A composite fiber comprising an anisotropic aromatic polyester (C polymer) and having an island component ratio in the sheath component of 0.02 to 0.5.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The term "melt anisotropy" as used in the present invention means to exhibit optical anisotropy (liquid crystallinity) in the melt phase.
For example, the sample can be certified by placing it on a hot stage, heating it up in a nitrogen atmosphere, and observing the transmitted light of the sample. The melt anisotropic aromatic polyester (A polymer) used as the core component in the present invention has a repeating constitutional unit derived from an aromatic diol, an aromatic dicarboxylic acid, an aromatic hydroxycarboxylic acid or the like. Those comprising a combination of repeating structural units shown in Chemical formulas 1 and 2 are preferable.

[Chemical 1]

[Chemical 2]

More preferably, the polymer is composed of the combination (5), (8), (9) of the above repeating constitutional units, and more preferably, the polymer corresponding to (5) It is an aromatic polyester in which the component Q) is 4 to 45 mol%.

[Chemical 3]

Melting point of melt anisotropic aromatic polyester (M
P) is preferably 230 to 300 ° C., more preferably 2
It is 40-280 degreeC. The melting point referred to here is a differential scanning calorimeter (DSC: TA300 manufactured by Mettler, for example).
0) is the peak temperature of the main endothermic peak (J)
IS K7121). Specifically, after taking 10 to 20 mg of a sample in a DSC device and enclosing it in an aluminum pan, 100 mL / min of nitrogen was flown as a carrier gas at 20 ° C. /
The endothermic peak when the temperature is raised in minutes is measured. If a clear endothermic peak does not appear in the above 1st Run depending on the type of polymer, the temperature is raised to 50 ° C higher than the expected flow temperature at a heating rate of 50 ° C / min, and kept at that temperature for 3 minutes or more. After completely melting, 5 at a rate of 80 ° C / min
It is recommended to cool to 0 ° C. and then measure the endothermic peak at a temperature rising rate of 20 ° C./min.

The melt anisotropic aromatic polyester (A polymer) used as the core component in the present invention includes polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyarylate, polyamide, as long as the effect of the present invention is not impaired. Polyphenylene sulfide, polyether ester ketone, fluororesin, etc. may be added. It may also contain various additives such as inorganic substances such as titanium oxide, silica and barium oxide, carbon black, colorants such as dyes and pigments, antioxidants, ultraviolet absorbers and light stabilizers.

The conjugate fiber of the present invention is characterized in that polycyclohexanedimethylene terephthalate (hereinafter abbreviated as PCT) is used as the sea component (B polymer) constituting the sheath component, and PCT is used as the sea component. As a result, the heat treatment temperature can be set higher, and high-strength fibers can be obtained in a short time. In addition, it may be modified with a diol other than cyclohexanedimethanol or a dicarboxylic acid other than terephthalic acid as long as the effect of the present invention is not impaired. In addition, polyolefin, polycarbonate, polyarylate, polyamide, polyphenylene sulfide,
You may add polyetheresterketone, a fluororesin, etc.

The melting point of PCT used in the present invention is preferably 270 ° C. or higher, more preferably 275 to 290 ° C., from the viewpoint that the heat treatment described later can be carried out efficiently.
If the melting point of PCT is less than 270 ° C., it may stick during heat treatment.

PCT, which is the sea component (B polymer) in the sheath component used during spinning, has an intrinsic viscosity [η] = 0.4-
1.2 is preferable, and more preferably [η] =
It is 0.6 to 1.0. The intrinsic viscosity [η] referred to in the present invention is an intrinsic viscosity measured at 30 ° C. by dissolving a sample in phenol: 1,1,2,2-tetrachloroethane = 1: 1.

As the island component (C polymer) constituting the sheath component of the conjugate fiber of the present invention, the same melt anisotropic aromatic polyester as the A polymer can be used.
The polymers may be the same or different. Preferably, the melting point (MP) of B polymer + 80 ° C or lower, MP-
Polymers at 10 ° C or higher are preferred. Further melt viscosity η1
0 to 60 Pa · s is preferable, and more preferably 20 to 5
It is 0 Pa · s. When the melt viscosity is less than 10 Pa · s, industrial production may be difficult. When the melt viscosity is more than 60 Pa · s, the spinnability is poor and the wire diameter fluctuation tends to be large, which makes it difficult to satisfy the required quality. There is. The melt viscosity η in the present invention means the temperature T (the melting point MP is 280
T = MP + 10 ° C above ℃, 290 below
C.) and the melt viscosity measured at a shear rate of 1000 sec ⁻¹ .

The sheath component ratio in the composite fiber of the present invention is 0.
It is 2 to 0.7, and preferably 0.3 to 0.5.
If the sheath component is less than 0.2, the core is likely to be exposed and fibrillation is likely to occur. If it exceeds 0.7, the strength may be insufficient. The term "sheath component ratio" as used in the present invention means the cross-sectional area ratio (B + C) / (A + B + C) of the composite fiber. The cross-sectional area ratio is obtained from a micrograph of the fiber cross-section, but it can also be obtained from the volume ratio of the discharge amounts of the core component and the sheath component during the production.

The melt-anisotropic aromatic polyester fiber can obtain excellent performance without being stretched, but the undrawn yarn made of a polymer having no melt anisotropy is in the unoriented state, and thus the physical properties are remarkably inferior. The strength is extremely low. Further, a polymer having no melt anisotropy has a low adhesiveness to a melt anisotropic polyester and has a problem that it is easily peeled off. From the above, according to the present invention, by constructing the sheath component with a blend (sea-island component) made of a polymer having no melt anisotropy and a polymer having no melt anisotropy, it is possible to enhance the strength of the sheath component and at the same time to form a core component. It is intended to improve the adhesiveness of. The sheath component of the core-sheath type composite fiber of the present invention has a sea-island structure. The sea-island structure means a state in which tens to hundreds of islands are present in the sea component serving as a matrix in the cross section of the fiber. B polymer and C
The number of islands can be adjusted by changing the mixing ratio of polymers, melt viscosity, and the like. In the present invention, B polymer and C
It can be obtained by chip-blending the polymer or mixing the melts of both components with a static mixer or the like.

The island component ratio in the sheath component of the conjugate fiber of the present invention is expressed by the produced conjugate fiber cross-sectional area ratio C / (B + C), and the island component ratio is 0.02-0.5.
It is preferably 0.1 to 0.3. Island component ratio is 0.02
If it is less than the above range, the effect of enhancing the strength of the sheath component, the adhesiveness with the core component, and the like cannot be expected, and as will be described later, the adhesion between fibers becomes severe during heat treatment, resulting in poor processability. on the other hand,
When it exceeds 0.5, the spinnability is deteriorated, and the tendency for the wire diameter variation to increase becomes remarkable, making it difficult to satisfy the required quality.
Furthermore, the melt anisotropic polyester (C) as an island component is likely to be exposed on the fiber surface, resulting in insufficient fibril resistance. The island component ratio can also be determined by the mixing ratio of the sea component and the island component at the time of manufacturing. The diameter of the island component is more preferably 0.1 to 2 μm.

Further, in the present invention, if necessary, B
Coloring agents can be included in the polymer and / or C polymer. The colorant may be contained in both the sea component and the island component, or may be contained in either one of them.
The contents may differ between the two components. Preferably, the colorant is contained in an amount of 0.1 to 2% by mass of each polymer. If it is less than 0.1% by mass, the coloring effect may be insufficient, and if it exceeds 2% by mass, the polymer may have a thickening effect and poor filterability. Especially for C polymers, C
It is preferable that the coloring agent is contained in an amount of 0.1 to 2% by mass based on the mass of the polymer, because the coloring agent is less likely to drop off due to abrasion.

As the colorant, carbon black, pigments (including titanium oxide, etc.) and heat resistant dyes can be used, and those having a particle size of 10 to 1000 mμ are preferably used. The colorant may be mixed by directly adding a predetermined amount to the B polymer and / or the C polymer,
High-concentration master chips may be diluted by a blending method during fiber production. Further, the B polymer and the C polymer may contain other polymers and various additives to the extent that the effects of the present invention are not impaired.

The conjugate fiber of the present invention can be spun by a known method. The cross-sectional shape of the obtained fiber is not particularly limited, but for example, the shape shown in FIG. 1 is preferable.

Although the conjugate fiber of the present invention has sufficient strength just by spinning, it has a low degree of polymerization of PCT in the sheath component and is brittle because it is not stretched (not oriented and crystallized). Peeling off or falling off easily occurs. Further, PCT having a high degree of polymerization, which is considered to be capable of imparting sufficient strength to the sheath component simply by spinning, has no spinnability and is practically impossible to spin. Therefore, the obtained fiber is subjected to solid phase polymerization by heat treatment in an atmosphere of an inert gas such as nitrogen or in an atmosphere of an oxygen-containing active gas such as air, or under reduced pressure, and oriented crystallization of PCT in the sheath component. By increasing the degree, the above problems can be solved. In addition, by performing solid-state polymerization by heat treatment, the degree of polymerization of PCT, which is a sheath component, increases, and the intrinsic viscosity [η] increases to 0.8 or more. In the present invention, the form of the fiber used for solid phase polymerization may be either filament or cut fiber.

In the case of the conventional core-sheath type composite fiber, the sheath component hardly contributes to the strength.
I had no choice but to reduce the sheath component. As a result, the sheath component is peeled off during abrasion or passing through the weaving process, and the core component is exposed to cause fibrillation. According to the present invention, since the sheath component also contributes to the improvement in strength, even when the sheath component ratio is increased, the strength is 14 cN / dtex or more and the elastic modulus is 400 cN /.
An excellent conjugate fiber having a dtex or more can be obtained.

The heat treatment atmosphere is preferably a low humidity body having a dew point of -80 ° C or lower. Preferred heat treatment conditions include a temperature pattern in which the temperature is gradually increased from the melting point of the core component of −40 ° C. or lower to the melting point of the sheath component or lower. The heat treatment time is preferably 2 to 40 hours, more preferably 3 to 15 hours.

The heat can be supplied by a method using a gaseous medium, a method utilizing radiation by a heating plate, an infrared heater, etc., an internal heating method utilizing high frequency and the like. The treatment shape may be a mould-like shape, a tow-like shape (for example, it is placed on a metal net or the like), or continuous treatment between rollers.

In the present invention, the intrinsic viscosity [η] of PCT solid-phase polymerized by heat treatment is 0.8 dl / g or more, preferably 0.8 to 1.5 dl / g, and more preferably 1. It is 0 to 1.3 dl / g. When the intrinsic viscosity [η] is less than 0.8, the strength of the sheath component is insufficient and desired wear resistance cannot be obtained.

According to the present invention, the core component is a melt-anisotropic aromatic polyester and the sheath component is a blend polymer of PCT and a melt-anisotropic aromatic polyester, whereby the peeling of the sheath due to microgluing during solid-phase polymerization is reduced. In addition, by increasing the heat treatment temperature, it is possible to improve the efficiency of solid-state polymerization, and by further increasing the degree of polymerization and crystallizing PCT of the sheath component, performance such as high strength, high elastic modulus, dimensional stability, etc. The composite fiber which retains, improves the surface fibrillation and the abrasion resistance which are the defects of the fiber made of the melt anisotropic aromatic polyester, and remarkably improves the defects such as the sheath crack and the sheath peeling in the core-sheath composite fiber. , And a mesh cloth can be obtained.

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. The measured values in this example are measured by the following method. [Melt viscosity MV] Shear rate r = 1000 sec ⁻¹
It measured using the Toyo Seiki Capillograph 1B type on the conditions of. [Logarithmic viscosity ηinh] A sample was dissolved in pentafluorophenol in an amount of 0.1% by mass (60 to 80 ° C), and the relative viscosity (ηre was measured using a Ubbelohde viscometer in a constant temperature bath at 60 ° C.
1) was measured and calculated by ηinh = ln (ηrel) / c. Note that c is the polymer concentration (g / dl). [Intrinsic viscosity] A sample was dissolved in phenol: 1,1,2,2-tetrachloroethane = 1: 1 and measured at 30 ° C according to a standard method. [Strength] According to JIS L 1013, test length 20 cm,
The breaking strength and elongation were determined under the conditions of an initial load of 0.1 g / d and a tensile speed of 10 cm / min, and an average value of 5 or more points was adopted. [Linear fluctuation%] Outer diameter measuring device M-46 manufactured by ZIMMER
Using 09A / 2, the linear shape of a filament having a length of 100 m at a yarn speed of 20 m / min was continuously recorded, the maximum (max) and the minimum (min), and the average value (x) were measured, and the value was obtained from the following formula. Linear variation (%) = ± ((max-min) / 2x) × 1
00 The larger the linear fluctuation, the more the peeling and dropping of the sheath component occur.

<Example 1> As the core component (A polymer), the constitutional units (P) and (Q) shown in Chemical formula 3 were 65 /
Melt anisotropic aromatic polyester (MP
= 260 ° C., η = 40.2 Pa · s, ηinh = 4.0
1 dl / g) was used. As a sheath component (B polymer), PCT (THERMX manufactured by Eastman Chemical Company)
6761; MP = 285 ° C., [η] = 0.91 dl / g, η
= 200 Pa · s), the same melt anisotropic aromatic polyester as the A polymer was used as the C polymer, and blended so that the island component ratio was 0.1. The core component and the sheath component were melted by separate extruders and spun at a spinning temperature of 310 ° C. and a winding speed of 700 m / min so that the area ratio of the core and the sheath was 2: 1. The spinning tone was good and 320 dtex / 6f composite fiber was obtained. The spun raw yarn is separated into 53 dtex
2 hours at 250 ° C, then 2 more
Heat treatment was performed at 70 ° C. for 4 hours in a nitrogen gas atmosphere. The heat-treated yarn obtained had the following properties.

Average wire diameter: 70 μm Tensile strength (DT): 17.6 cN / dtex Tensile elongation (DE): 3.1% Elastic modulus (YM): 500 cN / dtex Sheath component ratio: 0.33 Warp A plain weave was also used as the weft and a weft to obtain a 100 mesh screen gauze. No fluff or fibrils were generated during the weaving process, which was good. Furthermore, as a result of printing a ceramic-containing paste using this screen gauze, no peeling of the sheath occurred even after printing 1000 times. The sheath component of the conjugate fiber immediately after spinning is phenol: 1,1,2,2-tetrachloroethane = 1:
After dissolving in 1, the insoluble melt anisotropic polyester was removed by filtration, [η] of the dissolved PCT was measured (30 ° C.), and it was 0.79 dl / g. Furthermore, when the [η] of the sheath component (PCT) after heat treatment was measured by the same method, it was 1.1 dl / g. The results are shown in Table 1.

<Examples 2 and 3> Composite fibers were produced in the same manner as in Example 1 except that the sheath component ratio and the island component ratio were changed as shown in Table 1. (Table 1)

<Example 4> After the spinning, the heat treatment time was 250.
A composite fiber was produced in the same manner as in Example 1 except that the treatment was performed in a nitrogen gas atmosphere at 270 ° C. for 2 hours and at 270 ° C. for 10 hours. (Table 1)

<Comparative Example 1> PEN was used as the B polymer of the sheath component.
Spinning and heat treatment were carried out in the same manner as in Example 1 except that ([η] = 0.61 dl / g, η = 300 Pa · s) was used. Peeling of the sheath occurred at the time of setting. (Table 1)

Comparative Example 2 PEN was used as the B polymer of the sheath component.
([Η] = 0.61 dl / g, η = 300 Pa · s) was used, and a composite fiber was produced in the same manner as in Example 1 except that the heat treatment temperature was changed to 240 ° C. for 2 hours and 255 ° C. for 4 hours. did. (Table 1)

<Comparative Example 3> PEN was used as the B polymer of the sheath component.
([Η] = 0.61 dl / g, η = 300 Pa · s) was used, and a composite fiber was prepared in the same manner as in Example 1 except that the heat treatment temperature was changed to 240 ° C. for 2 hours and 255 ° C. for 12 hours. Manufactured. (Table 1)

<Comparative Example 4> A straight chain polyphenylene sulfide (melt viscosity 110 Pa · s:
A composite fiber was produced in the same manner as in Example 1 except that the spinning temperature was 300 ° C.) and the spinning temperature was 305 ° C. Using this filament for warp and weft to make a plain weave,
A 100 mesh screen gauze was obtained. No fluff or fibrils were generated in the weaving process, which was good. However, as a result of printing the ceramic-containing paste using this screen gauze, the sheath peeled off after printing about 100 times, making it unusable. (Table 1)

<Comparative Example 5> Spinning and heat treatment were carried out in the same manner as in Example 1 except that only PCT was used as the sheath component. However, agglomeration between fibers occurred during the heat treatment stage, and the sheath was peeled off during unwinding. There has occurred. (Table 1)

<Comparative Examples 6 and 7> Composite fibers were produced in the same manner as in Example 1 except that the sheath component ratio and the island component ratio were changed as shown in Table 1. (Table 1)

[0038]

[Table 1]

The composite fiber obtained by the present invention is excellent in strength and elastic modulus, and has a wire diameter variation rate of less than 4%.
No peeling or dropping of the sheath component and the core component occurred. There was no problem in the weaving process, and a product with excellent performance was obtained. on the other hand,
Comparative Example 6 had a large variation in wire diameter and did not satisfy the required quality. Further, in Comparative Example 7, since the sheath component ratio was large, the fiber strength was low. Further, the composite fiber of Comparative Example 7 had a yarn breakage trouble in the weaving process.

[0040]

According to the present invention, it is possible to obtain a composite fiber and a mesh cloth which have high strength and high elastic modulus in a short time efficiently, and which are excellent in fibrillation resistance, abrasion resistance and sheath peeling resistance. be able to.

[Brief description of drawings]

FIG. 1 is a typical cross-sectional schematic diagram of the cross-sectional shape of the conjugate fiber of the present invention.

[Explanation of symbols]

A: Melt anisotropic aromatic polyester (A polymer) B: Polycyclohexane dimethylene terephthalate (B
Polymer) C: Melt anisotropic aromatic polyester (C polymer)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) D21F 7/08 D21F 7/08 AF term (reference) 2H114 AB04 DA56 EA02 EA03 FA06 4L041 AA07 BA04 BA05 BA13 BA14 BA16 BA24 BA34 BA38 BA46 BC18 BC20 BD01 BD06 BD14 BD20 CA07 CA10 DD03 DD14 4L048 AA20 AA29 AA37 AA48 AB10 4L055 CE27 CE30 CF30 EA15 EA19 EA20 EA25 FA30

Claims (6)

[Claims] 1. A core-sheath type composite fiber having a core component composed of a melt anisotropic aromatic polyester (A polymer) and a sheath component having a sea-island structure, wherein a sheath component ratio is 0.2 to 0.7. The sea component constituting the sheath component is made of polycyclohexanedimethylene terephthalate (B polymer) having an intrinsic viscosity [η] of 0.8 dl / g or more, and the island component is a melt anisotropic aromatic polyester (C polymer). ), And the island component ratio in the sheath component is 0.02 to 0.5. 2. The composite fiber according to claim 1, wherein the melting point of polycyclohexanedimethylene terephthalate (B polymer) is 270 ° C. or higher, and the intrinsic viscosity [η] is 0.8 to 1.5 dl / g. 3. The melt viscosity η of the island component (C polymer) is 1
The composite fiber according to claim 1 or 2, which has a viscosity of 0 to 60 Pa · s. 4. The tensile strength is 14 cN / dtex or more, and the elastic modulus is 400 cN / dtex or more.
The conjugate fiber according to any one of 1 to 3. 5. A mesh cloth made of the composite fiber according to claim 1. 6. A screen gauze made of the mesh cloth according to claim 5.