JP2012001823A - High elastic modulus fiber with uniform structure and manufacturing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide highly strong and highly elastic modulus fiber of molten liquid crystalline polyester fiber without using a conventional method of performing high degree polymerization by means of heat treatment.SOLUTION: In composite fiber made of core component of molten liquid crystal polyester and sheath component of polystyrene with a melt flow rate (MFR) of 1 g per 10 minutes or larger or block copolymer including polystyrene block and polyolefin block, a method of manufacturing molten liquid crystal polyester by removing the sheath component by a solvent is adopted, thereby obtaining liquid crystalline polyester fiber having a uniform structure without any portion devitrifying in a fiber axis direction when observed with an optical microscope.

Description

  The present invention relates to a high modulus fiber having a uniform structure.

The melted liquid crystalline polyester fiber is excellent in various properties such as low hygroscopicity and chemical resistance, and depending on the production method, a fiber having a high elastic modulus can be obtained, and therefore, application in a wide range of fields is expected.
Conventionally, the higher the degree of polymerization, the higher the melting point and the lower the spinnability of the molten liquid crystalline polyester, so that the degree of polymerization is increased and the elastic modulus is increased by fiberizing and heat-treating a polymer having a low degree of polymerization ( For example, see Patent Documents 1 and 2.) However, such a method has a great time and cost for heat treatment, and is difficult to apply to general purpose applications.

  In addition, since melted liquid crystalline polyester is made into a fiber by melt spinning, a composite fiber can be produced relatively easily. Specifically, a core sheath having liquid crystal polyester as a core component and another polymer as a sheath component. A fibrillated fiber obtained by spinning a composite fiber or a polymer-blended dissimilar polymer has been proposed (see, for example, Patent Documents 3 to 5). However, it is difficult to obtain a high modulus fiber by these methods.

Japanese Patent Publication No. 55-002008 JP 60-239600 A JP-A-1-229815 Japanese Patent No. 3266712 Japanese Patent No. 3301672

  An object of the present invention is to provide a high elastic modulus fiber in a melted liquid crystalline polyester fiber without using a conventional method for increasing the degree of polymerization by heat treatment.

  As a result of intensive studies to obtain the above-mentioned fibers, the present inventors have obtained a liquid crystal obtained by leaching the sheath polymer after fiberizing by a core-sheath compound spinning method using a liquid crystal polyester polymer as a core component. The inventors have found that the polyester fiber has a high elastic modulus and have reached the present invention.

  That is, the present invention is a block composed of polystyrene or a polystyrene block and a polyolefin block whose core component is molten liquid crystalline polyester, sheath component is 230 ° C., and melt flow rate (MFR) at a load of 2.16 kgf is 1 g / 10 min or more. This is a method for producing a molten liquid crystalline polyester fiber obtained by removing a sheath component with a solvent in a composite fiber composed of a copolymer.

  The present invention also relates to a molten liquid crystalline polyester fiber obtained by the above production method, wherein the fiber axis method has a uniform structure without a portion devitrified when observed under an optical microscope. is there.

Further, the present invention is a fiber obtained by the above production method, and in a state where heat treatment at 200 ° C. or higher is not performed after melt spinning, the refractive index n _{// in the} direction parallel to the fiber axis and the direction perpendicular to the fiber axis a liquid crystalline polyester fiber, wherein the average refractive index which is calculated by the following equation from the refractive index n _⊥ of is 1.711 or more.

  In the core-sheath type composite fiber in which the core component of the present invention is a molten liquid crystalline polyester and the sheath component is made of polystyrene or a block copolymer, the sheath component is dissolved and removed with a solvent, and has a high degree of molecular orientation. Fiber can be obtained.

Hereinafter, the present invention will be described in detail. The molten liquid crystallinity (anisotropy) referred to in the present invention is to show optical liquid crystallinity (anisotropic) in the melt phase. For example, it can be recognized by placing the sample on a hot stage, heating and heating in a nitrogen atmosphere, and observing the transmitted light of the sample.
The molten liquid crystalline polyester used in the present invention is composed of repeating structural units such as aromatic diol, aromatic dicarboxylic acid, and aromatic hydroxycarboxylic acid, for example, those composed of a combination of repeating structural units shown in Chemical Formulas 1 to 2 below. preferable.

  Of these, a polymer comprising (5), (6), (7) and (9) among the combinations of repeating structural units represented by Chemical Formula 1 and Chemical Formula 2 is preferred.

  In particular, a polymer composed of a combination of repeating structural units shown in the following chemical formula 3 is preferred, specifically a polymer having a portion composed of repeating structural units of (A) and (B) of 65% by mass or more, particularly (B) An aromatic polyester having a component of 4 to 45% by mass is preferred.

  The melting point of the wholly aromatic polyester suitably used in the present invention is preferably in the range of 250 to 360 ° C, more preferably 260 to 320 ° C. The melting point referred to here is the main absorption peak temperature measured and observed with a differential scanning calorimeter (DSC; “TA3000” manufactured by METTLER) according to the JIS K7121 test method. Specifically, after taking 10-20 mg of sample in the DSC apparatus and sealing it in an aluminum pan, nitrogen is flowed as a carrier gas at 100 cc / min, and the endothermic peak is measured when the temperature is raised at 20 ° C./min. . Depending on the type of polymer, if a clear peak does not appear at 1st run in DSC measurement, the temperature is increased to 50 ° C higher than the expected flow temperature at a temperature increase rate of 50 ° C / min, and the temperature is increased for 3 minutes. After complete melting, the sample is cooled to 50 ° C. at a temperature decrease rate of −80 ° C./min, and then an endothermic peak is measured at a temperature increase rate of 20 ° C./min.

  In addition, the molten liquid crystalline polyester used as a core component in the present invention includes polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, polyether ether ketone, as long as the effects of the present invention are not impaired. You may add thermoplastic polymers, such as a fluororesin. Further, it may 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 sheath component in the conjugate fiber of the present invention should not interfere with the spinnability of the molten liquid crystalline polyester. Easily alkali-reduced modified polyethylene terephthalate and water-dispersible modified polyethylene terephthalate used in the production of ultrafine fibers are often used for reasons such as being leached with water and good spinnability. In terephthalate, the degree of orientation of the molten liquid crystalline polyester component is the same as when spinning with the molten liquid crystalline polyester alone. The reason is considered that the solidification temperature of polyethylene terephthalate is close to the solidification temperature of the molten liquid crystalline polyester, so that the composite spinning is almost the same as the case of spinning with polyethylene terephthalate alone.
On the other hand, in the present invention, the solidification temperature of the polymer is lowered by making the sheath component improving the degree of orientation of the melted liquid crystalline polyester of the core component into a block copolymer composed of polystyrene or a polystyrene block and a polyolefin block described later. However, the melted liquid crystalline polyester side of the core component solidifies first and the spinning stress is concentrated, and as a result, the orientation is reduced at a lower winding speed than the fiber obtained by spinning with the molten liquid crystalline polyester alone. A fiber having a high degree and Young's modulus can be obtained.
On the other hand, with the decrease in the solidification temperature of the sheath component, there is a concern that the wound fibers are stuck and the single fiber separation property is deteriorated, but in the present invention, the strength of the fiber itself is sufficiently increased by high-speed spinning. By making it high, it is possible to improve the single fiber separation property.

The polymer used as the sheath component in the present invention is a block copolymer composed of polystyrene or a polystyrene block and a polyolefin block.
By making these polymer components a. Satisfied high-speed spinnability; b. Good single fiber separation, c. Soluble in solvents based on limonene derived from plants that are less harmful to the human body, d. The filament composed of the core component from which the sheath component has been removed has a high degree of molecular orientation, has a low boiling water shrinkage, and becomes a fiber that can be used as it is, e. In addition, since these sheath components and solvents can be recovered and reused for the same application, it is environmentally friendly and can be reduced in cost.

  In the present invention, from the viewpoint of spinning stability in composite spinning, the MFR of the sheath component needs to be 1 g / min or more, preferably 3 g / min or more, more preferably 5 g / min or more to 150 g / min. Is less than a minute. High MFR means that the molecular weight of the polymer of the sheath component is small, and that only a certain molecular weight range satisfies the high-speed spinnability. MFR in the present invention was measured under the conditions of 230 ° C. and a load of 2.16 kgf in accordance with the JIS K7210 test method.

  The core component and the sheath component in the conjugate fiber of the present invention can satisfy all of the ae at the same time only within a specific ratio range. Preferably, the core component is 50% or more and 95% or less, the sheath component is 50% or less and 5% or more, more preferably the core component is 58% or more and 92% or less, and the sheath component is 42%. The core component is 65% or more and 90% or less, and the sheath component is 35% or less and 10% or more.

  In the composite fiber of the present invention, various additives such as inorganic substances such as titanium oxide, silica and barium sulfate, carbon black, colorants such as dyes and pigments, antioxidants, ultraviolet absorbers, and light stabilizers as necessary. May be included.

  The present invention is characterized in that the melt composed of the core component and the sheath component is subjected to composite spinning by being extruded by a composite spinning nozzle. The composite spinning nozzle can be a core-sheath type composite fiber using a core-sheath type composite spinning nozzle. The present invention is characterized by enabling higher orientation than fibers obtained by spinning a molten liquid crystalline polyester polymer alone. Spinning with a molten liquid crystalline polyester polymer alone is usually carried out at a spinning speed of 500 to 4000 m / min, but the orientation of the molten liquid crystalline polyester does not change within this range. On the other hand, the spinning speed for producing the conjugate fiber of the present invention is preferably in the range of 1500 to 4000 m / min. In the present invention, since a block copolymer component composed of polystyrene or a polystyrene block and a polyolefin block having a lower solidification temperature than a molten liquid crystal polyester component is used in composite spinning, the molten liquid crystalline polyester component is first solidified and stressed. Concentrate to form a highly oriented fiber structure. Furthermore, by controlling the molten liquid crystalline polyester component not to be exposed on the fiber surface by designing a composite spinning nozzle, a filament with good yarn quality is unlikely to form even at spinning speeds exceeding 4000 m / min. It becomes. Thus, in the present invention, it is a good requirement that not only productivity and cost, but also the single fiber separation of the sheath component is improved by high speed spinning.

  In the present invention, the fiber cross-sectional shape is controlled by removing the sheath component from the composite fiber with a solvent. Conventional weight loss processing of polyethylene terephthalate fibers requires a long time (around 60 minutes) at a high temperature (around 100 ° C.) using a sodium hydroxide solution. In the present invention, carbon tetrachloride or plant-derived The sheath component can be removed by treatment with limonene as a main component at a low temperature (around 40 ° C.) and a short time (around 15 minutes).

  The molten liquid crystalline polyester fiber from which the sheath component of the composite fiber of the present invention is removed by solvent has a uniform structure with no devitrified portion in the fiber axis method when observed under an optical microscope.

Further, the melt liquid crystalline polyester fiber from which the sheath component of the composite fiber of the present invention is removed is a refractive index n _{// in the} direction parallel to the fiber axis and the fiber axis in a state where heat treatment at 200 ° C. or higher is not performed after melt spinning. the average refractive index which is calculated by the following equation from a vertical direction of the refractive index n _⊥ to is preferably not 1.711 or more. The higher the average refractive index, the higher the density and crystallinity, and a higher elastic modulus can be expected. Specifically, the average refractive index is preferably 1.711 or more, more preferably 1.712 or more.

  In addition, the melted liquid crystalline polyester fiber from which the sheath component of the composite fiber of the present invention is removed has a characteristic of high molecular orientation. Evaluation of molecular orientation is usually performed by measuring birefringence. The molten liquid crystalline polyester fiber obtained by the present invention preferably has a birefringence of 0.380 or more, and more preferably 0.385 or more. Molten liquid crystalline polyester fibers with improved molecular orientation have high crystallinity as well as birefringence, and have sufficient strength and high heat resistance, so that they can be used in a wide range of applications including tension members.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by this Example. In the following examples, the average refractive index, fiber fineness, and elastic modulus are those measured by the following methods.

[Fiber strength Elastic modulus cN / dtex]
In accordance with JIS L1013, the strength and elastic modulus were measured 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.

[Average refractive index]
Using an interference microscope (Interfaco manufactured by Carl Zeiss), an immersion liquid having a refractive index of 1.97 is used for the parallel direction of the fiber, and an immersion liquid having a refractive index of 1.57 is used for the vertical direction. The refractive index (n _// ) and the vertical refractive index (n _⊥ ) were measured, and the average refractive index was calculated according to the following formula.

[Examples 1 to 3, Comparative Examples 1 to 4]
(1) Molten liquid crystalline polyester (“A920RX” manufactured by Polyplastics Co., Ltd., hereinafter referred to as LCP) as a core component, and polystyrene (Example 1, “HH32” manufactured by PS Japan, hereinafter referred to as PS) as a sheath component As a block copolymer, Kuraray Co., Ltd. “Septon 2063” (Example 2, hereinafter referred to as SEPS-1), “Septon 2002” (Example 3, hereinafter referred to as SEPS-2), “Septon 2104” (Comparative Example) 1, hereinafter referred to as SEPS-3), water-dispersible polyester (Comparative Example 2, "EASTONE S112" manufactured by Eastman, hereinafter referred to as E-PET), and dimethyl (I) 5-sodium sulfoisophthalate Polyethylene glycol (II) having a molecular weight of 2000 mol% and a molecular weight of 2000 mol of all acid components constituting the polyester The polyoxyethylene glycidyl ether (III) represented accounted for 10% by mass of the total copolymerized polyester, and the remaining polyester (terminated viscosity 0.58 dl / g) was terephthalic acid and ethylene glycol (comparative). Example 3, hereinafter referred to as R-PET). In Comparative Example 3, the copolymer polyester contains 5% by mass of an oxidative degradation inhibitor (“Sianox 1790” manufactured by American Siamid Inc.) based on the total amount of the polyethylene glycol and polyoxyethylene glycidyl ether. We used what to do.

(2) In Examples 1 to 3 and Comparative Examples 1 to 3, composite spinning was performed using LCP as the core component of the composite fiber and six types of polymers listed in Table 1 as the sheath component. The polymer of each component of the core-sheath was melted at a cylinder temperature of 310 ° C. and 290 ° C., respectively, the temperature of the core-sheath composite nozzle was 310 ° C., and the discharge amount of the core and sheath component in the composite spinning was 5 g / min, 2 g / min, Winding was performed at a spinneret diameter of 1 mm and a winding speed of 2500 m / min.
Further, as Comparative Example 4, melt spinning with LCP alone was wound at a cylinder temperature of 300 ° C., a nozzle temperature of 310 ° C., a discharge rate of 7 g / min, a spinneret diameter of 1 mm, and a winding speed of 2500 m / min.
With respect to the spinnability, the case where the prototype yarn was obtained at the set winding temperature was marked as “◯”, and the case where the yarn was broken on the spinning line during winding and the prototype yarn was not obtained was marked as “X”.
(3) Next, carbon tetrachloride for Example 1, D-LIMONENE for Examples 2, 3 and Comparative Example 1, water for Comparative Example 2, and 3% aqueous sodium hydroxide solution for Comparative Example 3 Ingredients were removed. For Examples 1 to 3 and Comparative Examples 1 to 3, the strength, elastic modulus, and average refractive index after removal of the sheath component were measured and calculated. In Comparative Example 4, the strength, elastic modulus, and average refractive index of the yarn after winding were measured and calculated. The results are shown in Table 1.

  The molten liquid crystalline polyester fiber obtained by the production method of the present invention has high birefringence and high crystallinity, and has sufficient strength and high heat resistance, so that it can be used in a wide range of applications including tension members.

Claims (3)

  It is composed of a melt liquid crystalline polyester as the core component, a sheath component as 230 ° C., a melt flow rate (MFR) at a load of 2.16 kgf of 1 g / 10 min or more, or a block copolymer composed of a polystyrene block and a polyolefin block. A method for producing a molten liquid crystalline polyester fiber obtained by removing a sheath component with a solvent in a composite fiber.   A molten liquid crystalline polyester fiber obtained by the production method according to claim 1, wherein the fiber axis method has a uniform structure without a portion devitrified when observed under an optical microscope. A fiber obtained by the production method according to claim 1 and having a refractive index n // in a direction parallel to the fiber axis and a direction perpendicular to the fiber axis in a state where heat treatment at 200 ° C or higher is not performed after melt spinning. A melted liquid crystalline polyester fiber having an average refractive index of 1.711 or more calculated from the refractive index n⊥ according to the following formula.