JP2007204888A - Molten liquid crystal-forming polyester conjugate fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molten liquid crystal-forming polyester conjugate fiber having a high strength and a high elasticity and also excellent in friction durability and flexing durability. <P>SOLUTION: This conjugate fiber constituted with a molten liquid crystal-forming polyester and flexible thermoplastic polymer is provided by having 40 to 90 wt.% conjugating ratio of the molten liquid crystal-forming polyester, constituting the component for forming the surface layer of the conjugate fiber with a mixture of the molten liquid crystal-forming polyester and the flexible thermoplastic polymer and also satisfying TB>TA+10°C by taking the melting point of the molten liquid crystal-forming polyester as TA and the melting point of the flexible thermoplastic polymer as TB. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a melted liquid crystal forming polyester composite fiber having high strength and high elastic modulus and excellent in friction durability and bending durability.

  The molten liquid crystal forming polyester fiber has a significantly high strength and elastic modulus compared to general-purpose fibers because the rigid molecular chains are highly oriented in the fiber axis direction, and further by performing heat treatment near the melting point, The degree of polymerization of the molten liquid crystal-forming polyester can be increased in the form of a fiber to further improve the performance.

  During this heat treatment, the molten liquid crystal forming polyester forms a more complete crystal and the melting point itself can be shifted to a higher temperature. Therefore, depending on the type of polyester and the heat treatment conditions, it can be heat treated to a melting point that exceeds the melting point of the raw material by about 50 ° C. As a result, the polymerization reaction can be promoted to develop high strength.

  However, it is known that only a weak intermolecular force acts in the fiber cross-sectional direction, resulting in a structure with low friction durability. Further, since kink bands are easily generated by bending and tend to localize, the bending durability is low.

  In order to remedy these drawbacks, a core-sheath type composite fiber composed of a flexible polymer such as polyethylene naphthalate in which the core component is a melt liquid crystal forming polyester and the sheath component is oriented and crystallized has been proposed (patent) Reference 1). In addition, as a core-sheath type composite fiber with improved interfacial peeling and improved friction durability, the core component is a molten liquid crystal-forming polyester, and the sheath component is a sea component composed of a flexible thermoplastic polymer and a molten liquid crystal-forming polyester. A core-sheath type composite fiber composed of an island component (see Patent Document 2), a core-sheath type composite fiber composed of a melt liquid crystal forming polyester as a core component and polycyclohexanedimethanol terephthalate as a core component (Patent Document) 3) has been proposed.

  In this way, it is a fact that friction durability and bending durability are improved by making a composite structure with an improved core component. However, when heat treatment is performed in a package shape, it is generally used as a flexible thermoplastic polymer. Polyethylene naphthalate, polyphenylene sulfide, etc. used commonly have lower or equivalent melting points than molten liquid crystal forming polyesters, so there is an upper limit on the temperature of heat treatment to increase the degree of polymerization, and the potential strength level of molten liquid crystal forming polyesters On the contrary, if heat treatment is performed near the melting point of the melt-forming liquid crystal forming polyester, the fiber surface is fused and irregularities are formed at the contact point with the adjacent yarn, resulting in friction durability and bending durability. It has the problem of being lowered. In addition, the heat treatment temperature is limited, and high strength and high elastic modulus cannot be achieved.

Furthermore, the island component is a melted liquid crystal forming polyester, the sea component is a flexible thermoplastic resin such as polyphenylene sulfide, and the island component is dispersed throughout the cross section of the fiber to suppress interfacial delamination (patent Reference 4), a technique for improving the degree of polymerization of molten liquid crystal forming polyester in a short time by using molten liquid crystal forming polyester as a core component and a sheath component as a polymer having a melting point higher than that of the core component has been proposed. (See Patent Document 5).
Japanese Patent Laid-Open No. 04-272226 (Claim 1) Japanese Patent Laid-Open No. 08-260249 (Claim 1) JP 2002-317334 A (Claim 1) JP 2003-239137 A (Claim 4) Japanese Patent Laid-Open No. 06-057534 (Claim 1)

  As described above, it is a fact that friction durability and bending durability are improved by using a composite structure with an improved sheath component. However, when heat treatment is performed in a package shape, polyethylene naphthalate, polyphenylene sulfide, etc., which are generally used as flexible thermoplastic polymers, have a melting point lower than or equal to that of molten liquid crystal forming polyester. When heat treatment is performed in the vicinity of the melting point of polyester, the fiber surface is fused and irregularities are formed at the contact point with the adjacent yarn, and fibrils are generated starting from the irregularities, resulting in reduced friction durability and bending durability. Has the problem. In addition, the heat treatment temperature is limited, and high strength and high elastic modulus cannot be achieved.

  An object of the present invention is a composite fiber composed of a molten liquid crystal forming polyester and a flexible thermoplastic polymer, wherein the composite ratio of the molten liquid crystal forming polyester is 40 to 90% by weight, and the composite fiber The component forming the surface layer is composed of a mixture of the molten liquid crystal forming polyester and the flexible thermoplastic polymer, the melting point of the molten liquid crystal forming polyester is TA, and the melting point of the flexible thermoplastic polymer is TB. Sometimes achieved by a composite fiber characterized by satisfying TB> TA + 10 ° C.

  The present invention makes it possible to avoid softening and melting during heat treatment of a flexible thermoplastic polymer, which has been a problem until now, while achieving high strength and high elastic modulus while improving friction durability and bending durability. It has been possible to provide excellent fibers and monofilaments for screen bags using the fibers.

  The molten liquid crystal forming polyester used in the present invention refers to a polyester that exhibits optical anisotropy (liquid crystallinity) when heated and melted. It can be identified by placing a sample made of molten liquid crystal forming polyester on a hot stage, heating and heating in a nitrogen atmosphere, and observing the transmitted light of the sample with a polarizing microscope.

  Examples of the melt liquid crystal forming polyester include (a) a polymer of aromatic oxycarboxylic acid, (b) a polymer of aromatic dicarboxylic acid and aromatic diol, and aliphatic diol, (c) (a) and (b). And the like. Moreover, a conventionally well-known method can be used for the polymerization prescription of molten liquid crystal forming polyester.

  Here, examples of the aromatic oxycarboxylic acid include hydroxybenzoic acid, hydroxynaphthoic acid, and the like, or alkyl, alkoxy, halogen-substituted products thereof and the like.

  Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, naphthalene dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylethanedicarboxylic acid, and the like, or alkyl, alkoxy, and halogen substituted products thereof. It is done. Examples of the aromatic diol include hydroquinone, resorcin, dihydroxybiphenyl, naphthalene diol, and the like, or alkyl, alkoxy, and halogen substituted products thereof. Examples of the aliphatic diol include ethylene glycol, propylene glycol, butanediol, neopentyl glycol and the like.

  Furthermore, as a composition ratio of the said structural unit, it is preferable that an aromatic oxycarboxylic acid unit is 30-100 mol% of the whole, and it is more preferable that it is 50 mol% or more. The aromatic dicarboxylic acid, aromatic diol, and aliphatic diol may not be included in the composition, but when included, each is preferably 50 mol% or less, more preferably 30 mol% or less. Further, it is preferable that the content ratio of the aromatic dicarboxylic acid and the content ratio of the aromatic diol and the aliphatic diol coincide with each other at 5 mol% or less.

  The flexible thermoplastic polymer used in the present invention refers to a thermoplastic polymer that does not exhibit melt liquid crystal forming properties. Examples of the flexible thermoplastic polymer include vinyl polymers such as polyester, polyamide, polyolefin, and polystyrene, polycarbonate, polyimide, polyphenylene sulfide, polyphenylene oxide, polysulfone, polyether ketone, polyether ether ketone, aliphatic polyketone, semi-polymer, and the like. Aromatic polyester amide, polyester ether ketone, fluororesin and the like can be mentioned. The flexible thermoplastic polymer of the present invention may contain other copolymer components in a proportion of 20 mol%, more preferably 10 mol% or less.

  The molten liquid crystal forming polyester and the flexible thermoplastic polymer used in the present invention include various metal oxides, inorganic substances such as kaolin and silica, colorants, matting agents, difficulty, and the like within the range not impairing the effects of the present invention. A small amount of additives such as a flame retardant, an antioxidant, an ultraviolet absorber, an infrared absorber, a crystal nucleating agent, a fluorescent brightener, and a terminal group blocking agent may be contained.

  The composite fiber of the present invention is a fiber in which the above-mentioned molten liquid crystal forming polyester and a flexible thermoplastic polymer are combined inside a single fiber, and the component forming at least the surface layer of the composite fiber is the molten liquid crystal forming property. It is composed of a mixture of polyester and the flexible thermoplastic polymer. Preferably, a composite fiber that forms a structure in which a molten liquid crystal-forming polyester and a flexible thermoplastic polymer are uniformly mixed over the entire cross section of the fiber cross section, and a mixing ratio of the molten liquid crystal forming polyester in the cross section (hereinafter referred to as “mixing ratio”) , Referred to as “LCP ratio”), and a surface layer component occupying the surface layer of the fiber, such as at least the sheath component of the core-sheath composite fiber or the sea component of the sea-island composite fiber, The composite fiber comprised from the mixture of molten liquid crystal-forming polyester and this flexible thermoplastic polymer is mentioned. In this case, the LCP ratio of the composite component other than the surface layer component such as the core component or the sea component is preferably higher than the LCP ratio of the surface layer component because a high strength and high elastic modulus fiber can be obtained.

  Uniformly mixed composite fibers have the advantage that they can be manufactured at a relatively low cost, and composite fibers composed of components with different LCP ratios can further improve strength, elastic modulus, friction durability, and bending durability. Have

  The mixed structure can be confirmed by observing the cross section of the fiber, usually the mixed state is a sea island state composed of a dispersed layer that is an island part and a continuous layer that is a sea part. In rare cases, both components have a sea-sea structure with a dispersed layer and a continuous layer. In the present invention, at least in the component that forms the surface layer, it is preferable that the dispersion layer is composed of a melt liquid crystal forming polyester and the continuous layer is composed of a flexible thermoplastic polymer, and the dispersion layer forms a melt liquid crystal in the entire cross section of the composite fiber. More preferably, the conductive polyester and the continuous layer are composed of a flexible thermoplastic polymer. As a result, the inherent high mechanical properties of the molten liquid crystal forming polyester, which is a dispersion layer, are exhibited as described later, and at the same time, a flexible thermoplastic polymer, which is a continuous layer, is placed on the fiber surface for friction durability. And bending durability can be remarkably improved.

  In this sense, in the fiber cross section of the composite fiber of the present invention, the total arc length of the flexible thermoplastic polymer exposed on the fiber surface with respect to the fiber outer peripheral length is preferably 60% or more. Thereby, the exposure of the molten liquid crystal forming polyester to the fiber surface is reduced, and fibrillation due to friction and bending can be prevented. For this purpose, the total arc length of the flexible thermoplastic polymer exposed on the fiber surface with respect to the fiber outer peripheral length in the fiber cross section is more preferably 80% or more.

  The composite ratio of the molten liquid crystal forming polyester constituting the composite fiber of the present invention is 40 to 90% by weight. If it is less than 40% by weight, it is difficult to obtain the fiber of high strength and high elastic modulus, which is the object of the present invention. If it exceeds 90% by weight, the characteristics of friction durability and bending durability of the flexible thermoplastic polymer can be obtained. It becomes difficult to express. This ratio may be changed within the above range depending on the target performance of the conjugate fiber. For example, when high strength and high elastic modulus are required, such as a screen filament monofilament, the molten liquid crystal forming polyester is preferably in the range of 50 to 90% by weight, more preferably 60 to 85% by weight. is there.

  On the other hand, the mixing weight ratio of the flexible thermoplastic polymer constituting the conjugate fiber of the present invention is preferably 10 to 60% by weight. By setting the content to 10% by weight or more, the characteristics of friction durability and bending durability can be fully expressed, and the high strength and high elastic modulus that the melted liquid crystal forming polyester potentially has can be realized. It becomes difficult.

  The composite fiber of the present invention needs to satisfy TB> TA + 10 ° C., where TA is the melting point of the molten liquid crystal forming polyester, which is a constituent component, and TB is the melting point of the flexible thermoplastic polymer. This melting point is determined by measuring the melting point of the composite fiber. As a result, the molten liquid crystal-forming polyester can be heat-treated without melting the flexible thermoplastic polymer to increase the degree of polymerization, thereby achieving high strength and high elastic modulus. When heat treatment is performed in order to improve the strength and elastic modulus of the molten liquid crystal forming polymer, the higher the heat treatment temperature is, the more desirable it is to carry out the polymerization reaction in a reasonable time. On the other hand, as the heat treatment temperature is increased, the melting point of the molten liquid crystal forming polymer moves to a higher temperature, so that the heat treatment can be performed at a higher temperature, and the degree of polymerization can be further improved. By making such a treatment possible, the composite fiber of the present invention is significantly improved in deformation and fusion of the fiber surface when heat-treated in the form of a package, and friction durability and bending durability caused by unevenness of the fiber surface. The fall of property can be further suppressed. For this purpose, it is preferable that TB> TA + 20 ° C.

  The melting point TA of the molten liquid crystal forming polyester is preferably in the range of 220 to 360 ° C, more preferably 280 to 350 ° C, in such a melting point range and in terms of heat-spinning and heat resistance. More preferably, it is 310-340 degreeC.

  Further, the type is not limited as long as the melting point of the flexible thermoplastic polymer satisfies the above conditions, but it is preferable to use polyether ether ketone because it has excellent heat resistance, chemical resistance, and mechanical properties. .

  In addition, melting | fusing point of the composite fiber in this invention can be analyzed with the measuring method described in the Example. Two peaks, a melted liquid crystal forming polyester and a flexible thermoplastic polymer, are observed, and each peak can be identified by measuring the melting point of each single component. If it is unclear, after identifying each compound component, it is identified by a method of removing only one component using a solvent or the like and measuring the melting point of the other component.

  An example of the manufacturing method of the composite fiber of this invention is shown below.

  A spun fiber can be obtained by melt spinning using a known mixing device, spinning device or the like so as to obtain the above-described composite structure. This fiber already has sufficient strength and elastic modulus after being spun, but usually the degree of polymerization is increased by heat treatment to improve performance.

  The heat treatment can be performed in an inert gas atmosphere, an active gas atmosphere containing oxygen such as air, or under reduced pressure. In order to prevent deterioration of the fiber, it is preferable to perform the treatment in an inert gas atmosphere. Furthermore, the heat treatment atmosphere is preferably a low-humidity gas having a dew point of −40 ° C. or less. As the heat treatment conditions, the initial temperature is from room temperature to the melting point (TA ′) − 50 ° C. of the raw material of the melt liquid crystal forming polyester, and then from TA′−40 ° C. to the melting point (TB ′) of the raw material of the flexible thermoplastic polymer. It is preferable to carry out with a temperature pattern in which the temperature is raised sequentially. The heat treatment time is from several minutes to several tens of hours depending on the target performance.

  The heat supply in the heat treatment includes a method using a medium such as a gas, a method using radiant heat from a heating plate, an infrared heater, etc., a method in contact with a heat roller, a heat plate, etc., an internal heating method using high frequency, etc. Can be used. Further, the heat treatment is performed under tension or non-tension depending on the purpose, and the shape can be processed in a package, crushed shape, tow shape (for example, placed on a metal net or the like), or continuously between rollers. . In particular, the package shape is suitable for heat treatment of long fibers, and can be processed at a high temperature for a long time as compared with continuous processing between rollers, and the cost is further reduced. The form of the fiber can be either filament or cut fiber.

  The composite fiber of the present invention may be in any form such as multifilament, monofilament, staple fiber, cut fiber. Moreover, it can utilize as fiber structures, such as a textile fabric, a knitted fabric, a nonwoven fabric, and a braid. Since it is a fiber having high strength, high elastic modulus, excellent friction durability and bending durability as in the present invention, it is suitable as a monofilament.

  The monofilament in the present invention can be applied to screen applications using conventional polyethylene terephthalate fibers or the like. The screen ridge in the present invention is a screen used for graphic printing or electronic circuit board printing on ceramic, glass, woven fabric, CD / DVD surface, etc., and a conventionally known method can be used as its production method. . Since the conjugate fiber in the present invention has excellent strength, elastic modulus and dimensional stability, it is particularly preferable to apply it to a high-density screen or a large substrate. In this case, the average fiber diameter is preferably 5 to 100 μm, more preferably 10 to 50 μm, and the cross section is preferably circular. A screen mixed with other fibers may be used as long as the effects of the present invention are not impaired.

  In addition, the composite fiber of the present invention is used in the fields of general industrial materials, building materials, sports applications, dustproof clothing, rubber reinforcing materials, electrical materials, acoustic materials, etc., and is particularly suitable for use in the form of textiles. Is. For these applications, the preferred fineness range of the composite fiber is 10 to 10000 dtex as a multifilament, or 0.1 to 100 dtex as a single yarn.

  Next, the present invention will be described in more detail with reference to specific examples, but the present invention is not limited thereto. In addition, the measuring method of the physical property quoted in the Example is shown below.

A. Melting | fusing point The peak temperature of the endothermic peak observed on the conditions of the temperature increase rate of 16 degrees C / min is measured with a differential scanning calorimeter (DSC2920 type | mold by Perkin-Elmer).

B. High elongation, elastic modulus Measured using Tensilon UCT-100 manufactured by Orientec, according to JIS L1013, except that the sample length is 100 mm and the tensile speed is 50 mm / min.

C. Cross-sectional observation of fiber A fiber sample was embedded in an epoxy by a conventional method, a section was collected with an ultramicrotome, and observed with a transmission electron microscope H-800 manufactured by Hitachi.

D. Friction durability evaluation Threaded (heat treated yarn) at a contact angle of 100 ° on a 3 mm satin metal bar, suspended at a load of 3.0 cN / dtex, given a reciprocating motion at a stroke length of 30 mm and a speed of 100 times / min. Measure the number of strokes until peeling, fibrils occur.

E. Unraveling When the unraveling speed is 100 m / min, it can be solved with almost no resistance. ○, there is a light fusion, there is a local resistance but the unraveling is △, at this speed, the fusion is Is marked with x if the thread breakage occurred and could not be unraveled.

Examples 1-5
As melted liquid crystal forming polyester, p-hydroxybenzoic acid unit is composed of 60 mol% of the whole, 4,4′-dihydroxybiphenyl unit is 20 mol%, terephthalic acid unit is 10 mol%, and isophthalic acid unit is 10 mol%. Polyester ether ketone resin PEEK90G (melting point: 344 ° C., hereinafter referred to as PEEK) manufactured by Victrex was used as a melt liquid crystal forming polyester (hereinafter referred to as LCP1) at a temperature of 0 ° C. and a flexible thermoplastic polymer. In a pellet form, LCP1 and PEEK were mixed at a weight ratio of 60/40, then melted and kneaded with an extruder, using a nozzle with a nozzle diameter of 0.30 mm, a nozzle length of 0.65 mm, and 10 holes, The yarn was discharged at a spinning temperature of 370 ° C. at 6 g / min. The discharged yarn was solidified in the atmosphere, and only one solidified yarn was wound at a speed of 600 m / min to obtain a 10 dtex monofilament. The spinning yarn was heated in a nitrogen gas atmosphere at an initial temperature of 240 ° C. for 3 hours, then at 4 ° C./hr to a final ultimate temperature of 310 ° C., and further subjected to heat treatment for 10 hours. The heat treatment was performed in the form of a package, and the conjugate fiber of Example 1 was obtained.

  In Example 2, a composite fiber was obtained under the same conditions as in Example 1 except that the final temperature for heat treatment was 320 ° C.

  In Example 3, as the molten liquid crystal forming polyester, a molten liquid crystal forming polyester having a melting point of 278 ° C. composed of 73 mol% of p-hydroxybenzoic acid units and 27 mol% of 6-hydroxy-2-naphthoic acid units ( Hereinafter, a composite fiber was obtained under the same conditions as in Example 1 except that LCP2 was used and the final temperature of the heat treatment was 270 ° C.

  In Example 4, a core for sheath-core composite fiber was used, LCP1 was used as the core component, and LCP1 and PEEK were mixed at a composite weight ratio of 30/70 as the sheath component. 30 and other conditions including heat treatment were the same as in Example 1 to obtain a composite fiber.

  In Example 5, the core component was mixed with LCP1 and PEEK at a composite weight ratio of 70/30, and the sheath component was mixed with LCP1 and PEEK at a composite weight ratio of 30/70. Other conditions A composite fiber was obtained under the same conditions as in Example 4.

  Table 1 shows the physical properties of the conjugate fibers of the present invention shown in Examples 1 to 5.

  The conjugate fiber of the present invention had no inter-fiber fusion after heat treatment and good unwinding properties. When observed with an optical microscope, the conjugate fiber was not uneven. Moreover, it had high strength and high elastic modulus and excellent friction durability, and had excellent physical properties as a monofilament for a screen cage. Furthermore, when melting | fusing point was measured, it confirmed that it was TB> TA + 10 degreeC in all the levels of the Example.

Comparative Examples 1-4
In Comparative Example 1, a composite fiber was obtained by performing heat treatment under the same conditions as in Example 1 except that only LCP1 was used without using a flexible thermoplastic polymer and the spinning temperature was 340 ° C.

  In Comparative Example 2, LCP2 was used as the molten liquid crystal forming polyester, 2,6-polyethylene naphthalate (hereinafter referred to as PEN) having a melting point of 267 ° C. was used as the flexible thermoplastic polymer, and the final temperature of heat treatment was 260 ° C. A heat treated yarn was obtained under the same conditions as in Example 1 except that.

  In Comparative Example 3, a heat treated yarn was obtained under the same conditions as in Example 1 except that the final temperature of heat treatment was 270 ° C.

  In Comparative Example 4, a core / sheath composite fiber base was used, LCP2 was used as the core component, polycyclohexanedimethanol terephthalate (hereinafter referred to as PCT) having a melting point of 293 ° C. was used as the sheath component, and the core / sheath had a weight ratio of 65 / 35, and a heat treated yarn was obtained under the same conditions as in Example 1 except that the final temperature of heat treatment was 270 ° C.

  The fibers shown in Comparative Examples 1 to 4 had inter-fiber fusion after heat treatment, and fibrils were generated during unwinding. Although Comparative Example 1 has a high strength and a high elastic modulus, since only the melted liquid crystal forming polyester is present on the fiber surface, the friction durability is extremely low. In Comparative Example 2, since the heat treatment temperature was insufficient, the strength and elastic modulus were slightly low, and the friction durability was also low due to the effect of fusion between fibers. In Comparative Example 3, it was difficult to obtain a filament due to frequent yarn troubles during unwinding. In Comparative Example 4, although fibers having high strength and high elastic modulus were obtained, there was fusion between fibers after heat treatment, and interface peeling occurred during unraveling, resulting in low friction durability. Therefore, the fibers mentioned in Comparative Examples 1 to 4 were not practically usable as screen filament monofilaments.

Claims (5)

  A composite fiber composed of a molten liquid crystal forming polyester and a flexible thermoplastic polymer, wherein the composite ratio of the molten liquid crystal forming polyester is 40 to 90% by weight, and a component that forms a surface layer of the composite fiber Is composed of a mixture of the molten liquid crystal forming polyester and the flexible thermoplastic polymer, and when the melting point of the molten liquid crystal forming polyester is TA and the melting point of the flexible thermoplastic polymer is TB, TB> TA + 10 ° C. A composite fiber characterized by satisfying   2. The composite fiber according to claim 1, wherein the liquid crystal-forming polyester forms a dispersion layer and the flexible thermoplastic polymer forms a continuous layer in the vicinity of the surface layer of the cross section of the composite fiber.   The composite fiber according to claim 1 or 2, wherein the flexible thermoplastic polymer is polyetheretherketone.   The composite fiber according to any one of claims 1 to 3, wherein the composite fiber is a monofilament.   A screen bottle made of the composite fiber according to claim 4.