JPH08260249A - Conjugate fiber for screen gauze and screen gauze - Google Patents

Abstract

PURPOSE: To obtain a fiber for screen gauze, having a high strength and a high elastic modulus and substantially not causing the fibrillation and core- sheath separation of the fiber, and to obtain the screen gauze. CONSTITUTION: This conjugate fiber for screen gauze is composed from a core component (A polymer) comprising a melt-anisotropic aromatic polyester and a sheath component comprising a sea component (B polymer) comprising a bending thermoplastic polymer and an island component (C polymer) comprising a melt-anisotropic aromatic polyester, and has a sheath component ratio of 0.25-0.75, a tensile strength of >=15g/d and an elastic modulus of >=400g/d.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen gauze composite fiber and a screen gauze having good weavability, high strength, and excellent durability and dimensional stability.

[0002]

2. Description of the Related Art In order to realize high-density and high-precision printing with a screen gauze, it is required that high tension gauze can be applied, that the dimensional change is small, and that the elastic recovery force is large. Although screen gauze using fibers made of flexible polymers such as nylon and polyester is widely used, such screen gauze has low strength and elastic modulus and does not always have good dimensional stability. It was From the above, a screen using a melt anisotropic polyester having high strength and high elastic modulus is disclosed in Japanese Patent Application Laid-Open No. 2-8064.
No. 0 and JP-A-3-220340 are proposed.

[0003]

Although the screen made of only melt-anisotropic polyester fiber has no problem in terms of strength and elastic modulus, it is a rigid polymer and its surface is easily fibrillated. The fibrils generated in Step 1 hindered the ink permeability and hindered high-precision printing, and thus could not be put to practical use. Further, it has been proposed to use sea-island fibers containing a melt-anisotropic polyester as an island component and polyethylene terephthalate as a sea component, but the strength of such fibers is about 12 g / d, and mechanical strength such as strength is high. It was not satisfactory in terms of performance. Further, JP-A-3-220340 discloses a screen gauze using a core-sheath type composite fiber having a melt anisotropic polyester as a core component and a flexible polymer as a sheath component. In order to increase the strength of the fiber, it is necessary to reduce the ratio of the sheath component as much as possible, and the core is exposed due to the eccentricity at the time of production, which makes production on an operating scale extremely difficult. In addition, since the flexible polymer of the sheath component is not stretched (not oriented and crystallized), it is very brittle, and there is a problem that the sheath is likely to be peeled off or fallen off.

The present invention provides a composite fiber for screen gauze and a screen gauze which have a high strength and a high elastic modulus, and in which the core and the sheath are less likely to be peeled off and the fibril resistance is excellent.

[0005]

According to the present invention, a core component (A polymer) is a melt anisotropic aromatic polyester and a sheath component is a sea component (B polymer) composed of a flexible thermoplastic polymer. It is composed of an island component (C polymer) composed of a melt anisotropic aromatic polyester and has a sheath component ratio of 0.25 to 0.25.
0.75, island component ratio 0.25-0.5, tensile strength 15g /
The present invention relates to a composite fiber for screen gauze and a screen gauze having an elastic modulus of 400 g / d or more.

The melt anisotropy referred to 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 aromatic polyester used in the present invention is an aromatic diol,
It is composed of repeating constitutional units such as aromatic dicarboxylic acid and aromatic hydroxycarboxylic acid, and is preferably composed of a combination of repeating constitutional units shown in the following chemical formula 1.

[0007]

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Particularly preferably, a polymer comprising a combination of repeating constitutional units shown in the following chemical formula 2 is preferable. In particular,
(A) and (B) is a polymer containing 65% by weight or more of the repeating constitutional units, and particularly the component (B) is 4 to
An aromatic polyester of 45% by weight is preferred.

[0009]

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The melting point (MP) of the preferred melt anisotropic polyester is 260 to 360 ° C., more preferably 270 to 350.
° C. The melting point here means the differential scanning calorie (DS
C: Peak temperature of the main endothermic peak observed with, for example, TA3000 manufactured by mettler (JIS K7121). Specifically, DSC (eg, Mettler TA3000)
After taking 10 to 20 mg of a sample in an apparatus and enclosing it in an aluminum pan, 100 cc / min of nitrogen was passed as a carrier gas, and 2
The endothermic peak when the temperature is raised at 0 ° C./min is measured. When a clear endothermic peak does not appear in the above 1st Run depending on the type of polymer, the temperature is raised to a temperature 50 ° C higher than the expected flow temperature at a heating rate of 50 ° C / min, and at that temperature, 3 After completely melting for a minute, the temperature is cooled to 50 ° C. at a rate of 80 ° C./minute, and then the endothermic peak may be measured at a temperature rising rate of 20 ° C./minute.

In the melt anisotropic aromatic polyester used as the A polymer in the present invention, polyethylene terephthalate, modified polyethylene terephthalate, polyolefin and polycarbonate are used as long as the effects of the present invention are not impaired.
, Polyarylates, polyamides, polyphenylene sulfides, polyetherester ketones, and fluororesin thermoplastic polymers may be added. It may also contain various additives such as inorganic substances such as titanium oxide, kaolin, silica and barium oxide, carbon black, colorants such as dyes and pigments, antioxidants, ultraviolet absorbers and light stabilizers.

The sea component (B polymer) is not particularly limited as long as it is a flexible thermoplastic polymer, and is a polyolefin, polyamide, polyester, polyarylate, polycarbonate, polyphenylene sulfide, polyester. Examples thereof include ether ketone and fluororesin. Particularly preferred are polyphenylene sulfide (PPS), polyethylene naphthalate and a semiaromatic polyesteramide represented by the following chemical formula 3. By using a flexible thermoplastic polymer as a sea component, the fibril resistance and abrasion resistance are greatly improved. The term "flexible polymer" as used in the present invention means a polymer having no aromatic ring on the main chain and an aromatic ring on the main chain, and having 4 or more atoms on the main chain between the aromatic rings. Refers to existing polymers.

[0013]

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The C polymer may be the same melt anisotropic aromatic polyester as the A polymer, and the A polymer and the C polymer may be the same or different.
Preferably, the melting point (MP) of B polymer + 80 ° C. or lower,
Polymers of MP-10 ° C or higher are preferred.

The sheath component ratio in the composite fiber of the present invention is 0.
It is set to 25 to 0.75, preferably 0.3 to 0.6.
In the case of ordinary core-sheath type composite fibers, the sheath component hardly contributes to the strength. Therefore, in order to obtain a high-strength fiber, the sheath component ratio had to be reduced. Therefore, the sheath component is peeled off during abrasion and the weaving process, and the core component is exposed to cause fibrillation, which causes troubles. According to the present invention, since the sheath component also contributes to the improvement in strength, it is possible to obtain an excellent conjugate fiber having a strength of 15 g / d or more even when the ratio of the sheath component is increased. If the sheath component ratio is less than 0.25, the core is likely to be exposed, and if it exceeds 0.75, the strength is insufficient. The sheath component ratio referred to in the present invention indicates the cross-sectional area ratio A / (A + B + C) of the composite fiber. The cross-sectional area ratio can be determined from a micrograph of the fiber cross-section, but it can also be determined by the volume ratio of the discharge amounts of the core component and the sheath component during production.

The melt-anisotropic polyester fiber can obtain excellent performance without being stretched, but the unstretched yarn made of a flexible polymer is in a non-oriented state, and thus the physical properties are remarkably deteriorated.
The strength was extremely low. Further, the flexible polymer has a low adhesiveness with the melt anisotropic polyester, and has a problem that it is easily peeled off. From the above, the present invention increases the strength of the sheath component and at the same time improves the adhesiveness with the core component by configuring the sheath component with a blend (sea-island component) composed of melt anisotropic polyester and a flexible polymer. It is an attempt to raise it. 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. The number of islands can be adjusted by changing the mixing ratio of the B polymer and the C polymer, the melt viscosity, and the like. It can be obtained by chip blending B polymer and C polymer, or by mixing the melts of both components with a static mixer or the like.

The island component ratio in the sheath component is 0.25 in the cross-sectional area ratio C / (B + C) of the produced sheath-type composite fiber.
Must be 0.5. If it is less than 0.25, the strength may not be sufficient, and if it exceeds 0.5, the melt anisotropic polyester (C) is likely to be exposed on the fiber surface, resulting in insufficient fibril resistance. In some cases, the island component and the sea component may be reversed. The island component ratio is
Although it can be determined from a micrograph of the cross section of the fiber, it can also be determined by the volume ratio of the discharge amounts of the core component and the sheath component during production. The diameter of the island component is preferably about 0.1 to 2 μm.

The conjugate fiber of the present invention can be spun by a known method, for example, using the nozzle shown in FIG.
The cross-sectional shape of the obtained fiber is not particularly limited, but for example, the shape shown in FIG. 2 is a preferable example.

Further, in the present invention, preferably, the B polymer and / or the C polymer may contain a colorant. The colorant may be contained in both the sea component and the island component, or may be contained in either one of them, and the content ratio may be different between the two components. Preferably, each polymer
Coloring agents corresponding to 0.1 to 2% by weight are included.
If it is less than 0.1% by weight, the coloring effect may be insufficient, and if it exceeds 2% by weight, the thickening effect and the filterability may be poor. It is preferable that the C polymer contains a colorant in an amount of 0.1 to 2% by weight based on the weight of the C polymer, because the colorant does not easily come off due to abrasion.

Carbon black, pigments (including titanium oxide, etc.) and heat resistant dyes can be used as the colorant, and those having a particle size of 10 to 1000 mμ are preferably used. As a method for mixing the colorant, a predetermined amount may be added directly to the B polymer and / or the C polymer, or a high-concentration master chip may be diluted by a blending method at the time of 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 already has sufficient strength and elastic modulus just by spinning, but its performance can be further improved by relaxation heat treatment or tension heat treatment.
The heat treatment can be performed in an atmosphere of an inert gas such as nitrogen, in an atmosphere of an oxygen-containing active gas such as air, or under reduced pressure. The heat treatment atmosphere is preferably a low humidity body having a dew point of -80 ° C or lower. A preferable heat treatment condition is a temperature pattern in which the temperature is sequentially raised from the melting point of the core component of −40 ° C. or lower to the melting point of the sheath component polymer or lower. The processing time is several minutes to several tens of hours depending on the purpose.

Heat is supplied by a method using a medium such as gas,
Method of utilizing radiation by heating plate, infrared heater, etc.,
There are a method of contacting with a heat roller, a heat plate and the like, an internal heating method using high frequency and the like. The treatment is performed under tension or without tension depending on the purpose. The treatment shape may be a mould-like shape, a tow-like shape (for example, placed on a metal net or the like), or continuous treatment between rollers. The tension heat treatment is preferably performed at a temperature not higher than the melting point of the core component of −80 ° C. with a tension of 1 to 10% of the cutting strength, and this treatment further improves various performances, particularly the elastic modulus.

Since the core-sheath type composite fiber of the present invention has a high strength and a high elastic modulus and is excellent in fibril resistance, it can be made to have a high tension, and also has a good elastic recovery and dimensional stability. The application of the gauze used for thin metal wires is also possible. The effect of the present invention can be more remarkably obtained when a monofilament having an average wire diameter of 5 to 70 μm, particularly an average wire diameter of 35 μm or less is used. When a high-density screen of 350 mesh or more using such a fiber is produced from polyethylene terephthalate fiber or the like, it can be easily cut by a slight abnormal tension in the weaving process or stretched by tension because of its small elastic modulus. Problem arises. Therefore, 400
Stainless steel fine wires were used for gauze of mesh or more, but stainless fine wires were not suitable for large-sized substrates due to poor elastic recovery rate, resulting in high cost. Since the conjugate fiber of the present invention has a high strength of 155 g or more at about 30 μm, it is possible to manufacture a high-density screen or a large substrate. If the strength is less than 15 g / d and the elastic modulus is less than 400 g / d, it becomes extremely difficult to provide a high-density screen of 400 mesh or more or a large substrate. Strength 18g / d
As described above, fibers having an elastic modulus of 500 g / d or more are more preferable.
A fabric such as a woven fabric mixed with other fibers may be used as long as the effect of the present invention is not impaired. The screen gauze obtained by the present invention can stably perform fine and clear printing in the field of screen printing such as pattern printing, character printing, name plate printing or color printing. .

[0024]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. [Melt viscosity MV] It was measured using a Toyo Seiki Capillograph 1B type under the conditions of 300 ° C. and a shear rate r = 1000 sec ⁻¹ . [Logarithmic viscosity ηinh] Sample was converted to pentafluorophenol
Dissolve 0.1% by weight (60-80 ° C) and measure the relative viscosity (ηrel) using an Upperode-type viscometer in a constant temperature bath at 60 ° C.
It was calculated by ηinh = ln (ηrel) / c. Note that c is the polymer concentration (g / dl). [Strength] In accordance with JIS L 1013, the breaking strength and elongation were determined under the conditions of a test length of 20 cm, 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. [Wire diameter variation%] Using a ZIMMER outer diameter measuring device M-4609A / 2, the wire diameter of a filament having a length of 100 m was continuously recorded at a yarn speed of 20 m / min, and the maximum (max) and minimum (min) were recorded. And the average value (x) were measured and determined from the following formula. Wire diameter fluctuation (%) = ± ((max-min) / 2x) × 100 The larger the wire diameter fluctuation, the more the peeling and dropping of the sheath component occur. [Guide wear] Using a tie tester manufactured by Daiei Kagaku Kikai Co., Ltd., 6 monofilaments were passed through each of the 3 comb guides arranged at an angle of 120 degrees, and a load of 1 g / d was applied to each filament. The hairs were reciprocated at a stroke length of 3 cm and a speed of 95 times / minute, and the number of times fluff (peeling, fibrillation) occurred was measured.

<Example 1> The A polymer contains a melt anisotropic aromatic polyester (MP = 281 ° C., in which the structural units (A) and (B) shown in Chemical formula 2 are 73/27 mol%. MV = 42
5poise, ηinh = 4.38dl / g) was used. As the sheath component, as the B polymer, linear polyphenylene sulfide (melted clay 1100 poise ⁻¹ : temperature 300 ° C.), C polymer
As the above, a melt anisotropic aromatic polyester similar to the above A polymer was used and blended so that the island component ratio was 0.33. The core component and the sheath component were melted by separate extruders and spun at a spinning temperature of 305 ° C. and a winding speed of 680 mm / min from the spinneret having the structure of FIG. 1 so that the weight ratio of the core and the sheath was 2: 1. .
The spinning tone was good and a fiber of 48 / 6f was obtained. The spun raw yarn was separated into 8d monofilaments, which were heat-treated in a nitrogen gas atmosphere at 250 ° C. for 2 hours, at 260 ° C. for 2 hours, and at 268 ° C. for 6 hours. The heat-treated yarn obtained had the following properties.

Average wire diameter: 27 μm Tensile strength (DT): 20.2 g / d Tensile elongation (DE): 3.1% Elastic modulus (YM): 522 g / d Core component ratio: 0.33 This filament Is used as a warp and weft to make a plain weave,
A 400 mesh screen gauze was obtained. No fluffing or fibrillation occurred in the weaving process, and there were very few irregularities in the weft gap.

Comparative Example 1 A core-sheath type composite fiber was obtained in substantially the same manner as in Example 1 except that only B polymer was used as the sheath. The performance of the obtained heat treated yarn is shown. Average wire diameter: 27 μm Tensile strength (DT): 14.1 g / d Tensile elongation (DE): 2.8% Elastic modulus (YM): 420 g / d Core component ratio: 0.35 Sheath in the fiber-splitting process When the filament before heat treatment was observed under a microscope, many small irregularities were present. A 400-mesh screen gauze was produced from this filament, but the resulting screen was not suitable for practical use due to peeling and dropping of the sheath during the weaving process.

<Example 2, Example 3, Comparative Example 2, Comparative Example 3> A composite fiber was produced in the same manner as in Example 1 except that the sheath component ratio and the island component ratio were changed. The results are shown in Table 1.

[0029]

[Table 1]

The composite fiber of the present invention was excellent in strength and elastic modulus, and had a wire diameter variation rate of less than 4%, and the sheath component and the core component were not substantially peeled or dropped. Screen
There was no problem in the manufacturing process of the gauze, and a product with excellent performance was obtained. On the other hand, Comparative Example 2 has good strength, elastic modulus, and wire diameter variation, but has a large island component ratio and a large amount of molten anisotropic polyester is exposed on the fiber surface, and thus has low fibril resistance due to guide wear. Met. Further, in Comparative Example 3, a fiber having a low strength was obtained because of a large sheath component ratio.
A screen gauze was produced using such fibers, but a yarn breakage problem occurred during the weaving process.

[0031]

According to the present invention, a high-density screen having high strength, good weavability, durability and dimensional stability.
Can be provided.

[Brief description of drawings]

FIG. 1 is a specific example of a base used in the present invention.

FIG. 2 is a specific example of the cross-sectional shape of the core-sheath type composite fiber obtained by the present invention. In the figure, A is an A polymer, B is a B polymer, and C is a C polymer.

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[Procedure amendment]

[Submission date] March 30, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

[0009]

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Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location D03D 9/00 D03D 9/00 15/00 15/00 A

Claims (2)

[Claims] 1. A core component (A polymer) is a melt anisotropic aromatic polyester, and a sheath component is a sea component (B polymer) composed of a flexible thermoplastic polymer and a melt anisotropic aromatic polyester. Composed of island component (C polymer)
Sheath component ratio 0.25 to 0.75, island component ratio 0.25 to 0.
5. A composite fiber for screen gauze having a tensile strength of 15 g / d or more and an elastic modulus of 400 g / d or more. 2. A core component (A polymer) is a melt anisotropic aromatic polyester, and a sheath component is a sea component (B polymer) composed of a flexible thermoplastic polymer and a melt anisotropic aromatic polyester. Composed of island component (C polymer)
Sheath component ratio of 0.25 to 0.75, tensile strength of 15 g / d or more,
A screen using a core-sheath type composite fiber having an elastic modulus of 400 g / d or more.