JP2006169665A - Sea-island-type fiber, method for producing the same, method for producing ethylene-vinyl alcohol-based copolymer component fiber, and fiber sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide sea-island-type fiber spinnable without causing spinning defects, and enabling the fiber itself to be formed with an ethylene-vinyl alcohol copolymer as island component without causing fusing or stiffening. <P>SOLUTION: The sea-island-type fiber is such that an ethylene-vinyl alcohol-based copolymer represents the island component and a readily extractable resin ≤200°C in melting point extractable within 60 min in a 3 wt.% aqueous caustic soda solution at 70°C represents the sea component, wherein the readily extractable resin is preferably an aliphatic polyester resin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a sea-island fiber and a method for producing the same, a method for producing an ethylene-vinyl alcohol copolymer component fiber using the sea-island fiber, and a fiber sheet containing the ethylene-vinyl alcohol copolymer component fiber.

  Since the ethylene-vinyl alcohol copolymer fiber has high hydrophilicity and a certain degree of chemical resistance, it is suitably used as a separator constituting fiber of, for example, an alkaline primary battery or an alkaline secondary battery. As such an ethylene-vinyl alcohol copolymer fiber, a relatively thick fiber having a fineness exceeding 0.55 dtex has been conventionally used, but the fineness of the ethylene-vinyl alcohol copolymer fiber is small. If it is thin, not only can the electrical insulation performance of the separator be improved, but also the electrolyte retainability is excellent and the thickness of the separator can be reduced. Combined fibers were long-awaited.

  As a response to such a demand, “battery separator paper comprising 2-45% by weight of ethylene-vinyl alcohol copolymer fibers having a single fiber fineness of 0.0001 to 0.5 d” is proposed. (Patent Document 1). In order to obtain this ethylene-vinyl alcohol copolymer fiber, it is disclosed that it is preferable to spin the sea-island fiber containing the ethylene-vinyl alcohol-based copolymer as an island component, and then remove the sea component of the sea-island fiber, It is disclosed that an easily alkali-reducing polyester polymer is preferable as the sea component, more specifically, 2.5 mol% of the total acid component in which 5-sodium sulfoisophthalic acid (I) constitutes the copolymer polyester, The structural unit obtained from polyethylene glycol (II) having a molecular weight of 2000 and polyoxyethylene glycidyl ether (III) occupies 10% by weight of the total copolymer polyester, and the remainder is composed of structural units obtained from terephthalic acid and ethylene glycol. Co-polyester (inherent viscosity 0.58 dl / g) was used. It is. Furthermore, it discloses that it was immersed in a 6% NaOH aqueous solution (80 ° C.) for 30 minutes to remove the sea component to obtain an ethylene-vinyl alcohol copolymer fiber.

  However, in order to spin sea island fibers having such a copolymer polyester as a sea component and an ethylene-vinyl alcohol copolymer as an island component, it is necessary to set the spinning nozzle temperature to about 300 ° C., When the sea-island fibers are spun at such a temperature, there is a problem that the ethylene-vinyl alcohol copolymer is thermally decomposed and gelled in the spinning nozzle to cause spinning failure. Even if sea island fiber can be spun, if the copolymer polyester is removed under the conventional conditions, the ethylene-vinyl alcohol copolymer may be fused or solidified to obtain a thin ethylene-vinyl alcohol copolymer fiber. In spite of the spinning of sea-island fibers, only thick ethylene-vinyl alcohol copolymer fibers can be obtained, and when a nonwoven fabric is produced by a wet method, poor dispersion tends to occur. It was.

  On the other hand, the applicant of the present application proposes a “composite fiber comprising a biodegradable polymer component and a hard-to-removable polymer component as a removal agent for the biodegradable polymer component”, Biodegradable polymer components include starch-based, chitosan-based, natural polymer-based polymer components, aliphatic polyester-based, fermentation-produced polymer components, ε-caprolactone, lactic acid-based, glycol-based, modified polyvinyl alcohol Chemically-synthesized materials such as those based on polyolefin are disclosed, and polyolefin-based, nylon-based, polyester-based, ester-based elastomers, olefin-based elastomers, urethane-based elastomers, etc. are disclosed as polymer components that are difficult to remove from alkaline solutions ( Patent Document 2).

JP 2001-76702 A (Claim 1, paragraph numbers 0011 to 0013, paragraph numbers 0034 to 0038, etc.) JP-A-8-188922 (Claim 1, paragraph numbers 0012 to 0014, etc.)

  However, it does not disclose an ethylene-vinyl alcohol copolymer as a difficult-to-removable polymer component, and does not recognize any problems with sea-island fibers using an ethylene-vinyl alcohol copolymer as an island component. It was.

  As described above, the present invention has a problem that arises when sea-island type fibers containing an ethylene-vinyl alcohol copolymer as an island component, that is, spinning can be performed without causing poor spinning, and fusion and solidification can occur. Sea-island fiber that can form ethylene-vinyl alcohol copolymer island component fiber without using the same, method for producing the same, method for producing ethylene-vinyl alcohol copolymer island component fiber using the sea-island fiber, and ethylene-vinyl It aims at providing the fiber sheet containing an alcohol copolymer island component fiber.

  The invention according to claim 1 of the present invention is that “extractable within 60 minutes in 3% by weight aqueous sodium hydroxide solution having an ethylene-vinyl alcohol copolymer as an island component and a melting point of 200 ° C. or lower and a temperature of 70 ° C. A sea-island type fiber characterized in that the extracted resin is a sea component. "

  The invention according to claim 2 of the present invention is “the sea-island fiber according to claim 1, wherein the easily extractable resin is made of an aliphatic polyester”.

  The invention according to claim 3 of the present invention is “a method for producing the sea-island type fiber according to claim 1 or 2 by a melt spinning method, wherein the spinning nozzle temperature is 250 ° C. or less. , Manufacturing method of sea-island type fiber. "

  The invention according to claim 4 of the present invention is as follows: “The sea-island type fiber according to claim 1 or 2 is immersed in an aqueous caustic soda solution of 3 wt% or less at a temperature of 60 to 70 ° C. for 60 minutes or less. Is a process for producing an ethylene-vinyl alcohol copolymer island component fiber, characterized in that the easily extractable resin is extracted and removed.

  The invention according to claim 5 of the present invention is “a fiber sheet comprising an ethylene-vinyl alcohol copolymer island component fiber formed from the sea-island fiber according to claim 1 or 2”. . "

  According to the invention of claim 1 of the present invention, since an easily extractable resin having a melting point of 200 ° C. or less is used as a sea component, spinning can be performed at a spinning nozzle temperature of 250 ° C. or less, and an ethylene-vinyl alcohol copolymer is formed in the spinning nozzle. Can be spun well since it does not thermally decompose and gel. In addition, the sea component can be removed in a short time with a low-temperature and low-concentration alkaline solution, so that a thin ethylene-vinyl alcohol copolymer island component can be obtained without fusing or solidifying the ethylene-vinyl alcohol copolymer. Fibers can be obtained, and a nonwoven fabric with excellent texture that is uniformly dispersed by a wet method can be produced.

  According to the invention according to claim 2 of the present invention, since the aliphatic polyester is biodegradable, the environment is not destroyed even if it is left or discarded after being removed and neutralized with an acid. It's easy to do.

  According to the invention of claim 3 of the present invention, since the spinning nozzle temperature is 250 ° C. or less, the sea-island can be stably produced without thermally decomposing the ethylene-vinyl alcohol copolymer in the spinning nozzle. Mold fiber can be spun.

  According to the invention of claim 4 of the present invention, since the sea component is removed under milder conditions than before, the ethylene-vinyl alcohol copolymer is thin without being fused or solidified. An ethylene-vinyl alcohol copolymer island component fiber can be obtained. Moreover, when a nonwoven fabric is produced by a wet method using this ethylene-vinyl alcohol copolymer island component fiber, a uniformly dispersed nonwoven fabric having excellent texture can be produced.

  According to the invention of claim 5 of the present invention, since the thin ethylene-vinyl alcohol copolymer island component fiber is included, electrical insulation, separation performance, liquid retention performance, wiping performance, hiding performance, hydrophilicity, etc. The fiber sheet is excellent in various performances and can be thin. Therefore, separators for alkaline secondary batteries, separators for electric double layer capacitors, separators for lithium ion secondary batteries, gas or liquid filter materials, laminate base materials, electrode support materials, wiping materials, It can be suitably used for medical substrate applications, fixing roll cleaning sheet applications in electrophotographic apparatuses, and the like.

  The sea-island fiber of the present invention comprises an ethylene-vinyl alcohol copolymer as an island component so as to be excellent in hydrophilicity and chemical resistance. The ethylene-vinyl alcohol copolymer of the present invention is not particularly limited, but has an ethylene content of 30 to 70 mol% (preferably 40 to 60 mol%) from the viewpoint of hydrophilicity and chemical resistance. Preferably there is. Any of random, block and graft copolymers may be used. Such an ethylene-vinyl alcohol copolymer can be obtained, for example, by saponifying an ethylene-vinyl acetate copolymer. In addition, it is preferable that the saponification degree of a vinyl alcohol unit is 95 mol% or more so that it may be excellent in hydrophilicity. The average molecular weight of the ethylene-vinyl alcohol copolymer is preferably 500 to 5000 from the viewpoint of spinnability and the like.

  The sea component of the sea-island fiber of the present invention has a melting point of 200 ° C. or lower (preferably 185 ° C. or lower) so that the ethylene-vinyl alcohol copolymer does not gel when spinning. Can be removed in a short time with a low-temperature and low-concentration alkaline solution, and a thin ethylene-vinyl alcohol copolymer island component fiber can be obtained without fusing or solidifying the ethylene-vinyl alcohol copolymer. And an easily-extractable resin that can be extracted within 60 minutes in a 3% by weight aqueous caustic soda solution at a temperature of 70 ° C. Preferably, it consists of an easily extractable resin that can be extracted within 30 minutes in a 3% by weight aqueous caustic soda solution at a temperature of 70 ° C.

  The easily extractable resin is not particularly limited as long as it satisfies the above conditions, but is preferably made of an aliphatic polyester. This is because the aliphatic polyester is biodegradable, and is easy to process without being destroyed even if it is left or discarded after being removed and neutralized with an acid. More specifically, as the aliphatic polyester, for example, a polymer or copolymer of α-hydroxy acid such as glycolic acid or lactic acid, ω-hydroxyalkanoate polymer such as ε-caprolactone or β-propiolactone, or Of β-hydroxyalkanoates such as copolymers, 3-hydroxypropionate, 3-hydroxybutyrate, 3-hydroxyheptanoate, 3-hydroxyoctanoate, 3-hydroxyvalylate, 4-hydroxybutyrate Degeneration of diol and dicarboxylic acid such as polymer or copolymer, polyethylene azelate, polybutylene oxalate, polybutylene succinate, polybutylene adipate, polybutylene sebacate, polyhexamethylene sebacate, polyneopentyl oxalate Examples include coalescence or copolymer Can. Among these, lactic acid is preferable because it has good spinnability and hydrolyzability in an aqueous caustic soda solution.

  The “melting point” in the present invention refers to a temperature giving a maximum value of a melting endothermic curve obtained by heating from room temperature at a heating rate of 10 ° C./min using a differential scanning calorimeter. In addition, “extractable” means that a tow of 110 dtex obtained by bundling spun fibers is immersed in a 3% by weight aqueous caustic soda solution at a temperature of 70 ° C. for 60 minutes, and the tow mass is 5% of the original tow mass. It means the following.

  The fineness of the sea-island fiber of the present invention is not particularly limited, and what is important is the fineness of the ethylene-vinyl alcohol copolymer island component fiber generated by removing the sea component, so the diameter of the island component in the cross section It is preferable that (circular cross-section equivalent value) is 5 μm or less (preferably 2 μm or less). Also, the fiber length is not particularly limited, and it may be a continuous long fiber or a cut short fiber, but the thin ethylene-vinyl alcohol copolymer island component fiber is uniformly dispersed. Since it is preferable to form the nonwoven fabric by a wet method, the fiber length is preferably 20 mm or less, more preferably 0.1 to 15 mm. In addition, if the sea-island type fiber is formed by removing the sea component of the sea-island fiber, the ethylene-vinyl alcohol-based copolymer island-component fiber is cut. A nonwoven fabric in which the combined island component fibers are uniformly dispersed can be produced. Also, the number of island components, the cross-sectional shape of the sea-island fiber, the cross-sectional shape of the island component, whether the diameter of the island component is one kind, or is the island component continuous in the length direction of the sea-island fiber? There is no particular limitation on how. Furthermore, the volume ratio between the sea component and the island component is not particularly limited, but since the sea component is removed, the smaller the amount, the better. On the other hand, when the amount is too small, the island components are fused or solidified. Since it becomes difficult to obtain a thin ethylene-vinyl alcohol copolymer island component fiber, the volume ratio of the sea component to the island component is preferably 60 to 10:40 to 90, and 50 to 20:50 to 80 is more preferable.

  Such a sea-island type fiber of the present invention is produced by a composite melt spinning method, a mixed melt spinning method, or a composite melt spinning or mixed melt spinning of island components and / or sea components at the time of composite melt spinning. In this case, the spinning nozzle temperature can be set to 250 ° C. or lower. This is because if the spinning nozzle temperature exceeds 250 ° C., the island-component ethylene-vinyl alcohol copolymer will gel, making it difficult to spin stably. More preferably, the spinning nozzle temperature is 240 ° C. or lower.

  The sea-island fiber of the present invention has the above-described configuration, but if the sea-island fiber of the present invention is used, sea components can be removed under milder conditions than before, without fusing or solidifying, An ethylene-vinyl alcohol copolymer island component fiber can be produced. More specifically, it is immersed in an aqueous caustic soda solution of 3% by weight or less at a temperature of 60 to 70 ° C. for 60 minutes to extract and remove an easily extractable resin as a sea component, thereby removing ethylene-vinyl alcohol-based copolymer. Combined island component fibers can be produced. Preferably, it is immersed in a 2 to 3% by weight aqueous caustic soda solution at a temperature of 60 to 70 ° C. for 30 to 45 minutes to extract and remove the easily extractable resin as a sea component. If necessary, a hydrolysis accelerator may be added to the aqueous caustic soda solution. Examples of the hydrolysis accelerator include neolate NCB (registered trademark, manufactured by Nikka Chemical Co., Ltd., special quaternary ammonium salt).

  The removal of the sea component from the sea-island type fiber can be performed in a fiber state such as a state where the sea-island type fiber is wound around a bobbin or the like or dispersed in a caustic soda aqueous solution. It can also be performed after the sheet is formed. However, when the sea component is removed after the fiber sheet is formed, the sea component is removed to form a fiber sheet having a rough structure even though the sea component is included even though the thin ethylene-vinyl alcohol copolymer island component fiber is included. Therefore, it is preferable to remove the sea component in the fiber state to produce a thin ethylene-vinyl alcohol copolymer island component fiber, and to form a fiber sheet using the island component fiber.

  Since the fiber sheet of the present invention contains the ethylene-vinyl alcohol copolymer island component fiber formed from the sea-island type fiber as described above, electrical insulation, separation performance, liquid retention performance, wiping performance, hiding performance, It is excellent in various performances such as hydrophilicity, and the fiber sheet can be thin. Therefore, separators for alkaline secondary batteries, separators for electric double layer capacitors, separators for lithium ion secondary batteries, gas or liquid filter materials, laminate base materials, electrode support materials, wiping materials, It can be suitably used for medical substrate applications, fixing roll cleaning sheet applications in electrophotographic apparatuses, and the like.

  Examples of the fiber sheet of the present invention include woven fabrics, knitted fabrics, and non-woven fabrics. Among these, non-woven fabrics are suitable because various performances can be imparted by the production method. In particular, it is preferably a wet nonwoven fabric with a thin and dense structure that can make use of the fineness of the ethylene-vinyl alcohol copolymer island component fiber of the present invention. The content of the ethylene-vinyl alcohol copolymer island component fiber of the present invention is not particularly limited because it varies depending on the intended use, purpose of use, etc. of the fiber sheet, but the ethylene-vinyl alcohol copolymer island is not particularly limited. In order to utilize the hydrophilic property and chemical resistance of the component fiber, it is preferably contained so as to occupy 2 mass% or more of the fiber sheet. Further, the fibers other than the ethylene-vinyl alcohol copolymer island component fibers are not particularly limited because they vary depending on the intended use and purpose of the fiber sheet.

  The fiber sheet of the present invention can be produced by a conventional method, and a suitable wet nonwoven fabric is formed by forming a fiber web containing the ethylene-vinyl alcohol copolymer island component fiber of the present invention by a conventional method. Adhering with a binder such as an emulsion or powder, adhering with an adhesive fiber (may be an ethylene-vinyl alcohol copolymer island component fiber) contained in the fiber web, These can be used in combination. Generally, when sea components are removed after forming a fiber sheet using sea-island type fibers, the structure becomes rough. When such a structure is allowed or preferred, the sea-island type fiber is used to form a fiber sheet. The sea component can also be removed after the formation. In addition, after forming a fiber sheet using a sea island type fiber, a sea component can be removed, and also a water stream can be made to act and densify a structure | tissue. Furthermore, the fiber sheet of the present invention may be subjected to post-treatment such as hydrophilization treatment (for example, sulfonation treatment, fluorine gas treatment, plasma treatment, surfactant application treatment, etc.) so as to suit various applications. it can.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

Example 1
As a sea component, a lactic acid polymer having a melt index (MI) at 190 ° C. of 10 to 15 (12.5 ± 2.5) (melting point: 177 ° C., 3% by weight aqueous caustic soda solution at 70 ° C. in 45 minutes) Available, Toyota Motor Corporation U'Z-4) is prepared, and the ethylene component of the ethylene-vinyl alcohol copolymer having an MI of 14 at 190 ° C (ethylene content: 47 mol%, Kuraray Co., Ltd.) is prepared as an island component. Manufactured, registered trademark: EVAL EP-G 110).

  Next, the sea component and the island component are supplied at a volume ratio of 50:50 to a sea island spinning nozzle (nozzle diameter: 0.3 mm) in which the temperature of a normal sea island type composite melt spinning apparatus is set to 240 ° C. After discharging at a speed of 5 g / min, it was wound up at 800 m / min to obtain an undrawn yarn (number of islands: 25, cross-sectional shape: circular). This undrawn yarn could be stably spun because the ethylene-vinyl alcohol copolymer was not thermally gelled.

  Thereafter, the tow, in which the undrawn yarn was converged to a fineness of about 600 dtex, was drawn 3.5 times while passing through a hot bath at a temperature of 90 ° C. to obtain a drawn yarn.

  Subsequently, the tow which converged this drawn yarn to a fineness of about 200,000 dtex was cut into a length of 3 mm by a guillotine cutter to obtain drawn short fibers.

  And this stretched short fiber was immersed in a 3% by weight aqueous caustic soda solution (neorate NCB (registered trademark, Nikka Chemical Co., Ltd., hydrolysis accelerator) 3 g / L added) at a temperature of 70 ° C. for 30 minutes, and the sea component Then, an ethylene-vinyl alcohol copolymer island component fiber (fiber length: 3 mm, cross-sectional shape: circular) having a fiber diameter of 3 μm was obtained. The ethylene-vinyl alcohol copolymer island component fibers were not fused or solidified, and were completely separated into individual fibers.

  20% by mass of this ethylene-vinyl alcohol copolymer island component fiber and a core-sheath type fiber having a core component of polypropylene and a sheath component of polyethylene (fineness: 1.5 dtex, fiber length: 5 mm, manufactured by Chisso Corporation, ES Fiber) After forming a wet fiber web by a conventional wet method using 80 mass%, it is supplied to a dryer set at a temperature of 140 ° C. to melt only the sheath component of the core-sheath fiber, and then fused. When a nonwoven fabric was produced, a dense fused nonwoven fabric with excellent texture could be produced.

(Comparative Example 1)
As the sea component, polyethylene terephthalate having an intrinsic viscosity (η) of 0.65 (melting point: 245 ° C., cannot be extracted with a 3 wt% sodium hydroxide aqueous solution at a temperature of 70 ° C., Toray Co., Ltd. T-900E) is prepared. The same ethylene-vinyl alcohol copolymer as in Example 1 was prepared.

  Next, the sea component and the island component are supplied at a volume ratio of 50:50 to a sea island spinning nozzle (nozzle diameter: 0.3 mm) in which the temperature of a normal sea island type compound melt spinning apparatus is set to 300 ° C. After discharging at a speed of 5 g / min, it was wound up at 800 m / min to obtain an undrawn yarn (number of islands: 25, cross-sectional shape: circular). This undrawn yarn could not be stably spun because the ethylene-vinyl alcohol copolymer was thermally decomposed and gelled after a while.

Therefore, the undrawn yarn spun before the ethylene-vinyl alcohol copolymer is gelled is drawn in the same manner as in Example 1 and is cut to obtain drawn short fibers after the temperature is reached. Although it was immersed in a 6% by weight aqueous caustic soda solution at 80 ° C. for 30 minutes, the sea component could not be removed. Therefore, when the sea component was removed over 90 minutes by further extending the time, the ethylene-vinyl alcohol copolymer island component fibers were fused together, and the ethylene-vinyl alcohol copolymer separated completely into individual fibers. Polymer island component fibers could not be obtained. Further, the drawn short fibers were immersed in a 3% by weight aqueous caustic soda solution at a temperature of 70 ° C. to remove the sea component, but the sea component could not be completely removed no matter how much it was immersed. It is possible to obtain only those in which ethylene-vinyl alcohol copolymer island component fibers are bonded to each other, and it is not possible to obtain ethylene-vinyl alcohol copolymer island component fibers that are completely separated into individual fibers. It was.

Claims (5)

An ethylene-vinyl alcohol copolymer is used as an island component, and an easily extractable resin that can be extracted within 60 minutes in a 3% by weight sodium hydroxide aqueous solution having a melting point of 200 ° C. or lower and a temperature of 70 ° C. is used as a sea component. Sea island type fiber. The sea-island fiber according to claim 1, wherein the easily extractable resin is made of aliphatic polyester. A method for producing a sea-island type fiber according to claim 1 or 2, wherein the sea-island type fiber is produced by a melt spinning method, wherein the spinning nozzle temperature is 250 ° C or lower. The sea-island type fiber according to claim 1 or 2 is immersed in an aqueous solution of caustic soda of 3 wt% or less at a temperature of 60 to 70 ° C within 60 minutes to extract and remove an easily extractable resin as a sea component. A process for producing an ethylene-vinyl alcohol copolymer island component fiber characterized by A fiber sheet comprising an ethylene-vinyl alcohol copolymer island component fiber formed from the sea-island fiber according to claim 1 or 2.