JP2007224448A - Electrically conductive conjugate fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide electrically conductive conjugate fiber excellent in fiber manufacturability and high-order process passableness and having high electrical conductivity. <P>SOLUTION: The electrically conductive conjugate fiber with triple sheath/core structure is characterized in that the melting point of polyethylene terephthalate constituting the cores is 240°C or lower, the polyamide constituting the sheathes covering the cores contains carbon black, and the sheath constituting the outermost layer consists of polylactic acid. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrically conductive conjugate fiber, and more particularly to an electrically conductive conjugate fiber having high electrical conductivity and excellent process passability in a yarn making process and a weaving process.

  Synthetic fibers made of polyester thermoplastic resins are widely used not only for clothing but also for industrial fields. However, these synthetic fibers have extremely high electrical resistance and have the fatal drawback of being easily charged with static electricity. In clothing, there are problems such as discomfort during detachment, clinging to the hem, and adhesion of dirt. When used as clothing, there are dangers of ignition to combustible gas and destruction of precision instruments. Various methods have been proposed so far in order to eliminate these defects caused by static electricity.

  Conventionally, a method for obtaining conductive fibers from a single polymer in which conductive carbon black is uniformly dispersed has been proposed. However, since these conductive fibers contain a large amount of carbon black, it is difficult to produce the fibers. There was a problem that the physical properties deteriorated remarkably. In order to solve these problems, there is a proposal to contain conductive carbon black in the core component polymer of the core-sheath composite type composite fiber and enclose it in a sheath made of a normal fiber-forming polymer (Patent Document 1). However, in this case, in order to maintain the fiber performance, the core portion is thickly surrounded by the non-conductive sheath, so that sufficient conductivity cannot be obtained.

  In order to solve this problem, a number of conductive composite fibers in which the conductive layer component containing carbon black is exposed on part or all of the fiber surface have been proposed (Patent Document 2). Since the conductive layer is exposed on the surface, there are various problems such as fluff in the yarn making and weaving process, peeling of the conductive layer component due to rubbing with the yarn path guides, and wear of the thread path guides.

In order to improve the passability in the yarn making and weaving process, the sheath thickness is set to 1/7 or less of the fiber diameter with respect to the core component containing the conductive particles, and the sheath component is dissolved in a solvent in the subsequent process. A method for producing a composite fiber in which a core component is exposed on the surface has been proposed (Patent Document 3). In this method, the process passability is certainly good, but it is difficult to always elute the sheath component uniformly, and the surface exposure state of the core component cannot be controlled uniformly, so there is a problem that the conductive performance varies. there were.
JP 55-1337 A (Claims) JP 2004-225214 A (Claim 1) JP-A-61-174469 (Claims)

  The present invention improves the wear of fuzz and yarn path guides in the yarn production and weaving process, which could not be achieved by the above prior art, and has excellent conductivity performance without variation in conductivity performance after elution treatment. An improved composite fiber is provided.

  The object of the present invention can be achieved by the following. That is, in a composite fiber having a triple core sheath structure, the melting point of polyethylene terephthalate forming the core is 240 ° C. or less, the polyamide forming the sheath covering the core contains conductive carbon black, and further forms the outermost layer. A conductive composite fiber whose sheath is made of polylactic acid.

  According to the present invention, it is possible to obtain a conductive conjugate fiber that is excellent in process passability in a yarn making process and a higher order process and has high conductivity.

  In the conductive conjugate fiber in the present invention, the core of the triple core sheath structure needs to be made of polyethylene terephthalate having a melting point of 240 ° C. or lower. The term “polyethylene terephthalate” as used in the present invention refers to ethylene terephthalate as the main repeating unit. Here, “mainly” means 60 mol% or more, preferably 70 mol% or more of all repeating units. By using polyethylene terephthalate as the core component of the composite fiber, it is possible to give the composite fiber sufficient mechanical properties, and by forming the melting point at 240 ° C. or less, the polyamide that forms the sheath and the outermost layer are formed. Thus, it is possible to stably produce yarn at the same spinning temperature as that of polylactic acid. The polyethylene terephthalate forming the core may have a melting point of 240 ° C. or lower, and examples thereof include polyethylene terephthalate obtained by copolymerizing a third component other than the terephthalic acid component and the ethylene glycol component. Here, as the third component, examples of the acid component include dicarboxylic acids such as isophthalic acid, cyclohexanedicarboxylic acid, adipic acid, dimer acid, and sebacic acid. On the other hand, examples of the glycol component include ethylene glycol and diethylene glycol. , Butanediol, neopentyl glycol, cyclohexanedimethanol, polyethylene glycol and polypropylene glycol, etc., but isophthalic acid is particularly preferred from the viewpoint of melting point lowering efficiency, and isophthalic acid is 5 with respect to the total acid content of polyethylene terephthalate. It is particularly preferred that the copolymerization is ˜30 mol%. Further, titanium dioxide as a matting agent, silica or alumina fine particles as a lubricant, hindered phenol derivatives as an antioxidant, and coloring pigments may be added as necessary.

  Next, in the conductive conjugate fiber of the present invention, the sheath covering the core needs to be formed of polyamide, and the polyamide needs to contain conductive carbon black. The conductive fiber of the present invention exhibits excellent conductivity by eluting and removing the outermost polylactic acid with an alkaline component after the yarn-making, weaving and knitting processes, and exposing the sheath containing the conductive carbon black to the fiber surface. . By using polyamide as the polymer that forms the sheath, even if the polylactic acid in the outermost layer is eluted with an alkali component, the polyamide in the sheath is not affected by the alkali component, so the elution ends when the outermost layer is eluted. However, there is no problem of carbon black falling off or non-uniform fiber cross section after elution due to elution variation. Therefore, it is possible to obtain a conductive composite fiber that is excellent in conductive performance and has no variation in conductive performance. As the polyamide in the present invention, polyamide-based thermoplastic resins such as nylon 6, nylon 66, nylon 10, nylon 12, and copolymers thereof can be preferably used. In addition, a heat-resistant agent, a fluidizing agent, and the like may be added to the polyamide referred to in the present invention as long as the conductive performance is not impaired.

In the present invention, the polyamide that forms the sheath needs to contain conductive carbon black. By containing conductive carbon black in the sheath, the sheath is exposed to the surface after the elution treatment of the outermost layer, and as a result, excellent conductivity can be exhibited. As the conductive carbon black used in the present invention, a conductive carbon black having an intrinsic volume resistance of 10 ⁻³ to 10 ² Ωcm is preferable. Specifically, furnace black, ketjen black, and acetylene black are preferably used. Can be used. The content of the conductive carbon black in the polyamide is preferably in the range of 15 to 50% by weight from the viewpoints of yarn production and conductivity.

  Furthermore, the sheath that forms the outermost layer of the conductive conjugate fiber of the present invention needs to be formed of polylactic acid. By coating the outermost layer with polylactic acid, it is possible to greatly suppress the spinneret stain during spinning, compared to the case where the sheath component containing carbon black is directly exposed on the surface, During high-order machining, wear of the hot plate, yarn path guide, and heel can be greatly reduced.

  The conductive conjugate fiber of the present invention may be used as it is without alkali elution treatment of the outermost layer polylactic acid, but by eluting the outermost layer with alkali and exposing the polyamide containing the carbon black component to the surface, It is possible to dramatically improve the conductive performance. Further, when the outermost layer is eluted, the entire surface of the yarn is covered with a conductive component, so that durability such as wear resistance and washing resistance is excellent.

  In polyester-based synthetic fibers, polyesters copolymerized with organic metal salts are generally used as elution components, but polylactic acid generally has a higher alkali elution rate than polyesters copolymerized with organic metal salts. Elution and removal can be easily performed, and no elution failure occurs. The polylactic acid referred to in the present invention preferably has a number average molecular weight of 50,000 to 100,000, more preferably polylactic acid composed of L-lactic acid having a purity of 95.0% to 99.5%. Such polylactic acid can maintain the strength in each production process, and can obtain appropriate biodegradability, so that the environmental load of the waste liquid after elution is small. Copolymerized polylactic acid obtained by copolymerizing other components having ester forming ability in addition to L-lactic acid or D-lactic acid may be used.

  Particularly preferable polylactic acid includes polylactic acid, which is a polyester mainly composed of L-lactic acid, and polyglycolic acid, which is a polyester mainly composed of glycolic acid, from the viewpoint of a high melting point and a low refractive index. . “L-lactic acid as a main component” means that 60% by weight or more of the constituent components is made of L-lactic acid, and is a polyester containing D-lactic acid within a range not exceeding 40% by weight. Also good. In addition, inorganic fine particles and organic compounds can be added as necessary as matting agents, deodorants, flame retardants, yarn friction reducing agents, antioxidants, and coloring pigments.

  The composite ratio of each component forming the conductive conjugate fiber of the present invention may be determined according to the use. However, the increase in the void portion of the woven / knitted fabric due to the change in the fineness after the alkali elution treatment, and the yarn making, weaving / knitting Considering the stability in the process, the composite ratio of the sheath component forming the outermost layer is preferably 5 to 20% by weight.

  In addition, the cross-sectional shape of the conductive conjugate fiber of the present invention needs to be a triple-core sheath structure, and not only a round cross-section but also a flat cross-section, a triangular cross-section, and a modified cross-section having a plurality of protrusions can be preferably exemplified. . The form of the triple core sheath may be concentric, or may be a structure in which the core is eccentric with respect to the sheath.

  The method for producing the conductive conjugate fiber of the present invention only needs to satisfy the composite form of the triple core sheath, and as an example, the core, sheath, and outermost component polymers are separately melted and introduced into the composite spin pack. There is a method of spinning from the discharge hole of the triple-core-sheath composite die, taking up the spun yarn at a predetermined speed, winding it once on a package, and drawing the obtained undrawn yarn with a drawing machine. . Further, the drawn yarn may be continuously heated and drawn without being wound once. For example, the drawn yarn is taken up at 1000 to 5000 m / min, and subsequently drawn and heat-set at 3000 to 6000 m / min. The method of doing is mentioned.

  The present invention is described in detail below. In addition, the evaluation in an Example followed the following evaluation methods.

A. Intrinsic viscosity [η]
A sample of 0.10 g was dissolved in 10 ml of orthochlorophenol and measured using an Ostwald viscometer at a temperature of 25 ° C.

B. Fabric surface resistance (Ω)
The surface electrical resistance of the fabric obtained in the Example mentioned later was measured using SURFACE REISTANCE CHECKER SRM-100 made by ZHI SHENG INDUSTRIAL, and evaluated with the common logarithm of the display resistance value (Ω). In addition, 7 or less was set as the pass.

C. Melting point A DSC-IB type manufactured by Perkin-E1mer was used and measured at a heating rate of 10 ° C./min, and the main peak temperature of the melting curve was taken as the melting point.

D. In order to obtain conductive conjugate fibers by the method of Examples described later, the yield of conductive conjugate fibers obtained from 1000 kg of chip raw materials is 100% or less 85% or more, and less than 85% to 70% or more Δ , Less than 70% was evaluated as x, and ◯ and Δ were regarded as acceptable.

E. Higher process passability In obtaining a fabric from a conductive conjugate fiber by the method of the embodiment described later, the guide frequency of the conductive conjugate fiber and the occurrence of fuzz and yarn breakage on the yarn path (per 1 kg of the conductive conjugate fiber) are 5 times. Less than was made into (circle), 6-10 times was set to (triangle | delta), 11 times or more was set to x, and (circle) and (triangle | delta) were set as pass.

F. Comprehensive evaluation When there is at least one item that is unacceptable among the fabric resistance value, the yarn-making property, and the high-order process passability, ×, either or both of the yarn-making property and the high-order process passability are △ The case where the resistance value was acceptable was evaluated as Δ, both the yarn-making property and the high-order process passability were evaluated as ○, the case where the fabric resistance value was acceptable was evaluated as ○, and ○ and Δ were regarded as acceptable.

Example 1
Polyethylene terephthalate chip (core component) having a melting point of 224.0 ° C. and an intrinsic viscosity [η] of 0.65, copolymerized with 12.7 mol% of isophthalic acid with respect to the total acid content, and conductive carbon black was 35 Separately, N6 chips (sheath components) melt-kneaded by a conventional method so as to be weight%, and poly-L-lactic acid chips (outermost layer components) having an optical purity of 98.0% and a number average molecular weight of 84,000 are separately provided. It was melt-extruded by a pressure melter and spun from a triple core sheath composite die at a spinning temperature of 255 ° C. The composite ratio of each component was 70% by weight of the core component, 20% by weight of the sheath component, and 10% by weight of the outermost layer component. The spun yarn was air-cooled, and after applying a spinning oil, it was wound up at a speed of 1500 m / min to obtain an undrawn yarn of a conductive conjugate fiber. The cross section of the obtained undrawn yarn was a composite state in which the components were arranged concentrically. After heating this unstretched yarn with a hot roller having a surface temperature of 88 ° C., passing it on a hot plate having a surface temperature of 160 ° C. while giving a stretching ratio of 2.7 times, winding it in a bobbin shape, A 28 dtex 3 filament conductive composite fiber was obtained. The spinning performance was as good as 93% yield.

  The obtained conductive conjugate fiber was twisted with a polyester fiber of 33 dtex 12 filaments under a condition of 300 T / m by a down twister. The resulting twisted yarns were both warp and horizontal using a water jet loom weaving machine at intervals of 80 per 84 dtex 72 filament polyester fiber, with a warp yarn density of 35 yarns / cm and a horizontal yarn density of 25 yarns / cm. A twill fabric was obtained. As the high-order process passability, the yarn breakage occurrence frequency was 3 times, which was a level that could be produced without problems.

  The obtained fabric was treated for 50 minutes in 80 ° C. warm water having a sodium hydroxide concentration of 30 (g / l) to elute the outermost polylactic acid. The common logarithm of the surface electrical resistance value of the fabric thus obtained had an excellent conductive performance of 6.

Example 2
A conductive conjugate fiber was obtained in the same manner as in Example 1 except that the composite ratio of the core component and the outermost layer component was changed to 75% by weight and 5% by weight, respectively. The spinning property was as good as 91% yield. Yarn processing and weaving were carried out in the same manner as in Example 1. As a result, the frequency of occurrence of yarn breakage in the high-order process was as good as 4 times. Furthermore, the common logarithm of the surface resistance value of the fabric obtained by carrying out the alkali treatment in the same manner as in Example 1 was 7, and the fabric had good conductive performance. The results are shown in Table 1.

Example 3
Except for changing the composite ratio of the core component and the outermost layer component to 60% by weight and 20% by weight, respectively, a conductive composite fiber is obtained by the same method as in Example 1, and further, the yarn is processed by the same method as in Example 1. A fabric was obtained by weaving. The yarn-making property was satisfactory with a yield of 88%, and the frequency of occurrence of yarn breakage in the high-order process was three times. Thereafter, alkali treatment was carried out in the same manner as in Example 1, and the common logarithm of the surface resistance value of the obtained fabric was 6, which had excellent conductive performance. The results are shown in Table 1.

Example 4
Using a polyethylene terephthalate chip having a melting point of 240 ° C., the copolymer amount of isophthalic acid of which is changed to 5.0 mol% based on the total acid content, as the core component, yarn production is performed in the same manner as in Example 1. Then, a conductive conjugate fiber was obtained, and a yarn was processed and woven in the same manner as in Example 1 to obtain a fabric. The yarn-making property was 90% in yield with no problem, and the yarn breakage occurrence frequency in the high-order process was also a good result of 3 times. When the alkali treatment was performed in the same manner as in Example 1, the logarithm of the surface resistance value of the obtained fabric was 6, and it had excellent conductivity. The results are shown in Table 1.

Example 5
The same as Example 1 except that the copolymerization amount of isophthalic acid was changed to 30.0 mol% with respect to the total acid content, a polyethylene terephthalate chip having a melting point of 182 ° C was used as the core component, and the spinning temperature was 250 ° C. The yarn was produced by the method described above to obtain a conductive conjugate fiber, and the yarn was processed and woven in the same manner as in Example 1 to obtain a fabric. The yarn-making property was 88% in yield with no problem, and the yarn breakage occurrence frequency in the high-order process was a good result of 4 times. When the alkali treatment was carried out in the same manner as in Example 1, the common logarithm of the surface resistance value of the obtained fabric was 6, and it had excellent conductivity. The results are shown in Table 1.

Comparative Example 1
The yarn was produced in the same manner as in Example 1 except that a polyethylene terephthalate chip having a melting point of 260 ° C., which was not copolymerized with the third component, was used as the core component and the spinning temperature was 270 ° C. Since the spinning temperature was high, polylactic acid was severely deteriorated and decomposed, making it impossible to produce yarn.

Comparative Example 2
The core and sheath components are the same polyethylene terephthalate and carbon black-containing nylon 6 as in Example 1, and each is melt-extruded in a separate pressure melter, the spinning temperature is 255 ° C., the composite ratio of each component is 80% by weight of the core component, A conductive fiber was obtained by the same method as in Example 1 except that the sheath component was 20% by weight, and the fiber was spun from a core / sheath composite base, and further, yarn was processed and woven by the same method as in Example 1 to obtain a fabric. In spinning, the frequency of occurrence of base stains was high, and the yield was 72%. Further, the yarn breakage occurrence frequency in the high-order process was as bad as 12 times, and it was not at a level capable of mass production.

  The conductive conjugate fiber of the present invention has high conductivity performance and durability, in addition to having excellent yarn-making properties and high-order passage properties that have never been seen before. In addition to being preferably used for dust clothes, surgical clothes, etc., it can be used for a wide range of applications such as brushes for OA equipment.

Claims (3)

  In a composite fiber having a triple core sheath structure, the melting point of polyethylene terephthalate forming the core is 240 ° C. or less, the polyamide forming the sheath covering the core contains conductive carbon black, and the sheath forming the outermost layer An electrically conductive conjugate fiber comprising polylactic acid.   The conductive composite fiber according to claim 1, wherein the composite ratio of the sheath component forming the outermost layer is 5 to 20% by weight.   The conductive composite fiber according to claim 1 or 2, wherein the polyethylene terephthalate forming the core is copolymerized with 5 to 30 mol% of isophthalic acid based on the total acid content.