JP2010168696A - Conductive conjugated fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive conjugated fiber which has a sufficient conductive performance and a sufficient strength, has excellent durability to repeated use, is little in unevenness, and can substantially enhance the fiber density of conductive fiber tip portions in the end portion of a brush, when used in an image-forming apparatus such as an electrophotography type copying machine or a printer. <P>SOLUTION: This conductive conjugated fiber is such that a core component comprising a stereocomplex type polylactic acid containing conductive fine particles is perfectly covered with a non-conductive sheath component comprising a thermoplastic polymer. In this fiber, the core component has a cross-sectional shape having two or more sharp projections, and the minimum thickness Vi of the non-conductive component formed between the outer peripheral portion of the sheath portion and the outer peripheral portion of the core portion is 0.5-5 μm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a conductive core-sheath type composite fiber having a stereocomplex polylactic acid containing conductive particles as a core component and a non-conductive component made of a thermoplastic polymer as a sheath component, The present invention relates to a conductive core-sheath composite fiber having excellent durability and suitable for a brush used in an image forming apparatus such as a laser printer, and a conductive brush using the same.

  Thermoplastic resins such as polyethylene, polyamide, and polyester are used in many applications as fiber products, but they have the drawback of being easily charged due to their poor antistatic properties, and thus many studies on conductive fibers have been made. .

  As one of the methods, there is a method of coating the surface of the fiber with a conductive substance. The conductive fiber thus obtained has good initial conductive performance, but wear resistance when worn, and further resistance to resistance. Since the washing and chemical resistance are insufficient, there is a problem that it becomes a source of dust generation when used in dust-proof clothing.

  In addition, a method in which a conductive material powder is dispersed in a thermoplastic resin to form a core component, and a fiber-forming thermoplastic resin is coated as a sheath component to form a core-sheath forming fiber, followed by electric discharge machining at a high voltage ( For example, Japanese Patent Laid-Open No. 63-219624. In the composite fiber, when the core component is not covered with the sheath component, troubles such as fuzz in the yarn making and weaving process, wear of the yarn guides, and loss of the function due to the conductive material dropping off during use. It is the cause of the occurrence.

  Further, in the image forming apparatus, for example, a conductive brush including the conductive fiber is used as a current-carrying medium to the charging drum or the static elimination drum. In this case, the tip of the brush may make more uniform contact. Although extremely important, no method has yet been found to achieve this. Also, when these conductive fibers are used for cleaning brushes provided to remove residual toner on the photoconductor, the residual toner remains because the contact of the brush to the photoconductor is not uniform. There was a problem of getting worse.

  On the other hand, synthetic fibers using thermoplastic resins such as polyethylene, polyamide, and polyester are difficult to be decomposed even after being used and left in nature, causing various problems in terms of protecting the global environment. . For example, these daily apparel are difficult to disassemble and are partly recycled after use, but most of them require treatment such as incineration, so that their disposal is limited.

  Furthermore, these synthetic fibers are made from petroleum, and as a result of mass consumption, the problem of depletion of fossil resources has been raised. Under such circumstances, the development of polymer materials that decompose in the natural environment is eagerly awaited, and research and development of various polymers such as aliphatic polyesters, and attempts to put them into practical use are active. Attention has been focused on polymers that are degraded by microorganisms, that is, biodegradable polymers.

On the other hand, most of the conventional polymers are made from petroleum, but by consuming a large amount of petroleum resources, carbon dioxide that has been stored in the earth since the geological era is released into the atmosphere, which further increases global warming. There is a concern that it will become serious. However, if a polymer can be synthesized using plant resources that grow by taking in carbon dioxide from the atmosphere, it is possible not only to suppress global warming by carbon dioxide circulation, but also to solve the problem of resource depletion at the same time. . For this reason, attention has been focused on polymers made from plant resources, that is, biomass polymers.
Based on the above, biodegradable polymers using biomass attract great attention and are expected to replace conventional polymers made from petroleum resources.

  In particular, polylactic acid is currently the most popular polymer for biomass utilization. Polylactic acid is a polymer made from lactic acid obtained by fermenting starch extracted from plants, and has the best balance of mechanical properties, heat resistance, and cost among polymers using biomass. Has been used. However, there is a problem that mechanical properties and heat resistance are inferior to those of conventional synthetic fibers.

A conductive composite fiber composed of polylactic acid containing conductive carbon and a polyester resin has been proposed (for example, JP 2008-196073 A).
However, in the composite fiber, since a part of the conductive component is exposed on the fiber surface, the function is caused by the conductive material falling off during use during the yarn and weaving process, the fuzz and the thread guides being worn, and the use. Troubles such as lowering have occurred.

JP 63-219624 A JP 2008-196073 A

  The object of the present invention is to solve the above-mentioned problems of the prior art, have sufficient conductive performance and strength, have excellent durability against repeated use, and electrophotographic copying machines and printers. When used in an image forming apparatus such as the above, an object of the present invention is to provide a conductive composite fiber that can substantially increase the fiber density at the tip of the conductive fiber at the brush end and has few spots.

  As a result of diligent investigations to achieve the above object, the present inventors have dispersed a conductive material powder in stereocomplex polylactic acid as a core component, and a core coated with a fiber-forming thermoplastic resin as a sheath component. The inventors of the present invention have reached the present invention by investigating that a desired conductive conjugate fiber can be obtained by making the core shape of the sheath-type conjugate fiber different.

  Thus, according to the present invention, a core component made of stereocomplex polylactic acid containing conductive fine particles is a conductive composite fiber completely covered with a non-conductive sheath component made of a thermoplastic polymer. The component has a cross-sectional shape having two or more sharp protrusions, and the minimum thickness Vi of the nonconductive component formed by the sheath component outer peripheral portion and the core component outer peripheral portion is 0.5 to 5 μm. An electrically conductive conjugate fiber is provided.

  According to the present invention, it has excellent durability against repeated use, and when used in a brush, it is possible to substantially increase the fiber density at its end, and a conductive composite fiber with few spots is obtained. Therefore, it can be suitably used for an image forming apparatus such as an electrophotographic copying machine or a printer. It is environmentally friendly because it is biodegradable.

Sectional drawing for demonstrating the example of the fiber cross-sectional shape of the electroconductive composite fiber of this invention. Sectional drawing for demonstrating the example of the fiber cross-sectional shape in other embodiment of the electroconductive composite fiber of this invention. The perspective view which shows an example of the pile fabric which comprises the electroconductive brush of this invention. The front view and side view which show an example of the cross section of the pile fabric which comprises the electroconductive brush of this invention. The side view which shows the creation example of the electroconductive brush of this invention.

  The core component of the conductive fiber of the present invention contains a conductive substance, and as the conductive substance, known substances such as conductive carbon black and conductive metal compounds can be used. Examples of the conductive carbon black include oil furnace type “Ketjen Black EC” (manufactured by Japan EC), “Conductex 975”, “Conductex SC” (Colombian) and acetylene type “DENKA”. In addition to known conductive carbon black such as “Black” (manufactured by Denka), thermal black, channel black, ketjen black and the like can be used.

  On the other hand, as the conductive metal compound, metal particles, metal oxide or metal compound particles, or particles having these films can be used. Examples of the metal particles include silver, nickel, copper, iron, aluminum, and alloys thereof. Particles having a metal oxide or metal oxide film include tin oxide obtained by mixing and firing antimony oxide as a second component, zinc oxide containing aluminum oxide as a second component, and conductivity such as tin oxide and zinc oxide. Inorganic particles such as titanium oxide, magnesium oxide, silicon oxide, and aluminum oxide having an oxide film can be used. As the metal oxide, copper iodide, copper sulfide, zinc sulfide, cadmium sulfide, or the like can be used. Among these, stannic oxide and zinc oxide excellent in whiteness are preferably exemplified. The stannic oxide here includes stannic oxide containing a small amount of an antimony compound, and conductive metal composites in which the surface of titanium oxide particles is coated with stannic oxide. Zinc oxide also includes zinc oxide containing a small amount of aluminum oxide, lithium oxide, indium oxide, and the like. These conductive materials are usually used as fine powder dispersed in a matrix polymer.

  The blending ratio of these conductive substances varies depending on the kind of particles, the particle diameter, the conductivity and the properties and crystallinity of the matrix polymer, but is usually preferably 15 to 80% by weight. If the blending amount is too small, the conductivity tends to decrease, and if it is too large, uniform dispersion in the polymer becomes difficult, and the yarn forming property tends to decrease.

As the stereocomplex type polylactic acid constituting the core component, a mixture of poly L-lactic acid and poly D-lactic acid is used.
Poly L-lactic acid and poly D-lactic acid, which are homopolymers of polylactic acid, have a melting point of about 180 ° C., but in the case of a copolymer of D-lactic acid and L-lactic acid, the proportion of any component is 10 mol. If it is about%, the melting point is about 130 ° C., and the spinnability is lowered, which is not preferable.

  Therefore, as polylactic acid, L / D or D / which is the content ratio (molar ratio) of L-lactic acid and D-lactic acid indicated by the content ratio of L-lactic acid or D-lactic acid when polymerizing using lactide as a raw material. L is preferably 90/10 or more, more preferably 95/5 or more, and even more preferably 97/3 or more.

  The weight average molecular weight (Mw) of the polylactic acid described above is not particularly limited, but is preferably 60000 or more and 200000 or less. When Mn of polylactic acid is smaller than 60000, the meltability is likely to deteriorate due to low viscosity at the time of melting. Moreover, when the number average molecular weight of polylactic acid is larger than 200000, it will become a high viscosity at the time of a melt | dissolution, and a yarn-making property will deteriorate easily.

By mixing the above polylactic acid homopolymer, the melting point becomes 200 to 230 ° C., the strength in a high temperature atmosphere is increased, and sufficient strength and durability can be exhibited when used for a brush or the like. .
The mixing ratio of poly D-lactic acid / poly L-lactic acid is preferably 40/60 to 60/40, more preferably 45/55 to 55/45, and even more preferably 50/50.

  As the thermoplastic polymer used as the sheath component, polyester, polyolefin, or a copolymer thereof is preferable, and polyethylene terephthalate is particularly preferable. In addition, organic antistatics such as polyalkylene glycols, block polyether esters and block polyether amides containing surfactants such as organic sulfonic acids or their metal salts, organic phosphoric acids or their metal salts in the core-sheath component polymer. The sex component may be dispersed in an amount of 5% or less.

The composite fiber of the present invention is characterized in that the cross-sectional shape thereof has a cross-sectional shape having a sharp protrusion having two or more core components, as illustrated in FIGS.
That is, the composite fiber of the present invention has an atypical cross section to bring the conductive portion closer to the surface layer, improve the cross-sectional conductivity and surface conductivity of the fiber, and has excellent durability for repeated use. When used in a brush, the fiber density at the end can be substantially increased.

Furthermore, in the present invention, the minimum thickness Vi of the non-conductive component formed by the core component outer peripheral portion and the sheath component outer peripheral portion formed by the sharp protrusions needs to be 0.5 to 5 μm.
When the minimum thickness Vi of the non-conductive component is smaller than 0.5 μm, the core and the sheath are peeled off, or a portion where the sheath component does not cover the core component is generated and the conductive material is dropped, and the conductive performance This causes problems such as lowering the temperature and causing contamination. On the other hand, when the minimum thickness Vi of the non-conductive component is larger than 5 μm, the conductivity is lowered and a sufficient function as a conductive brush is not exhibited.

  In the composite fiber cross section, the area occupied by the core component (A) is preferably 5 to 30%. When the area is smaller than 5%, the antistatic property may be inferior. On the other hand, when the area exceeds 30%, the mechanical properties, dust resistance, and durability of the fiber may be deteriorated.

  In order to manufacture a conductive brush using the conductive core-sheath composite fiber of the present invention, first, a pile fabric using the fiber as a pile yarn is manufactured. As a manufacturing method of a pile fabric, it can manufacture using a publicly known method. For example, in the case of a pile woven fabric, a cloth such as a moquette / velvet shown in FIG. 3 can be manufactured by a known method. In this case, the conductive conjugate fiber may be used only for at least the pile yarn. On the other hand, in the case of a pile knitted fabric, a fabric such as a double raschel tricot can be produced by a known method. In addition, when manufacturing a pile fabric, 2 or more types of fibers can also be used together, for example, in the range which does not impair the performance of a conductive brush, normal polyester fiber is added to the conductive composite fiber of this invention. A pile fabric may be manufactured.

  3 to 5 show examples of conductive brushes using the conductive conjugate fiber of the present invention, FIG. 3 is a perspective view showing an example of a pile fabric constituting the conductive brush, and FIG. 4 shows the conductive brush. FIG. 5 is a side view showing an example of a conductive brush according to the present invention. FIG. In FIG. 4, 1 is a warp yarn of a pile fabric, 2 is a weft yarn, 3 is a base fabric, 4 is a coating layer applied as required, and 5 is a pile yarn. Moreover, 6 in FIG. 5 shows a pile fabric, 7 shows a support | pillar.

  In order to manufacture the conductive brush of the present invention, for example, as shown in FIG. 4, the fabric of the pile fabric manufactured by the above method is spirally wound around a support to obtain a brush shape. Thereafter, napping treatment and shearing treatment are performed to obtain a conductive brush for an image forming apparatus. Moreover, it is good also as an electroconductive brush which fixed the pile fabric to the plane.

The cross-sectional electrical resistance value (temperature 20 ° C., humidity 40 to 70% RH) of the conductive composite fiber in the conductive brush is preferably 10 ² to 10 ¹¹ Ω / cm. Preferably, it is 10 ⁸ to 10 ¹⁰ Ω / cm at a temperature of 25 ° C. and a humidity of 40% RH. Although it differs depending on the type of image forming apparatus, it is not preferable because it is difficult to obtain uniform charging, static elimination and cleaning effects even if it is lower or higher than this.

  Since the pile yarn made of the conductive conjugate fiber of the present invention satisfies the above conditions, it exhibits a sufficient function as a conductive brush that can be suitably used for an image forming apparatus such as a laser printer.

  Hereinafter, an example is given and the composition and effect of the present invention are explained in detail. In addition, the physical property in an Example is measured with the following method.

(B) Cross section internal electrical resistance value Ag doutite (silver particle-containing conductive resin paint, manufactured by Fujikura Kogyo Co., Ltd.) on both cross sections of the fiber whose both ends are cut in the cross section direction so that the length in the fiber axis direction is 10 cm. On the electrically insulating polyethylene terephthalate film, a DC voltage of 1.7 kV was applied using the Ag doubite-attached surface on the electrically insulating polyethylene terephthalate film under the conditions of a temperature of 25 ° C. and a relative humidity of 40%. The current value was determined, and the electrical resistance value Ω / cm was calculated according to Ohm's law.

(B) Durability of conductive brush JIS L1096 8.17.3 In the friction strength test of the C method (taper criminal method), the load was 4.90 N and the wear wheel No. The wear durability of the conductive brush was measured with CS-17 and 500 frictions. When the surface was wiped with a white cotton cloth, it was evaluated by the color transfer of carbon to the cotton cloth.
A: Almost no color shift and good B: Slight color shift
C: Blackening and fading

[Example 1]
17.5 parts by weight of conductive carbon black, L-D of 98.7 / 1.3, which is the content ratio of L-lactic acid and D-lactic acid, and L / D of 1.3 / 98.7 1 using a conductive resin composition comprising 82.5 parts by weight of a stereocomplex polylactic acid mixed with a poly (D-lactic acid) of 50/50 as a core component and polyethylene terephthalate as a sheath component ( The core-sheath type composite fiber having the cross-sectional shape shown in (b) was spun by melt spinning, and then drawn 1.9 times to obtain a multifilament yarn of 250 dtex / 40 filaments. The performance of the obtained fiber is shown in Table 1.
Next, a pile fabric (velvet) using this fiber as a pile yarn was manufactured, and a conductive brush was prepared. At this time, the pile fabric was designed to have a pile density of 5,000 pieces / cm ² and a pile length of 5 mm. The results are shown in Table 1.

[Comparative Example 1]
In Example 1, it implemented like Example 1 except having changed the fiber cross-sectional shape so that a conductive component might be exposed to the fiber surface, as shown to (A) of FIG. The results are shown in Table 1.

  According to the present invention, since the core component does not come out on the surface, there is no trouble such as dropping off of the conductive part, and it has excellent durability against repeated use. Therefore, electrophotographic copying machines, printers, etc. The image forming apparatus can be suitably used.

Vi Minimum thickness of non-conductive component 1 Warp yarn 2 Weft yarn 3 Base fabric 4 Coating layer 5 Pile yarn 6 Pile fabric 7 Strut

Claims (3)

  A conductive core-sheath composite fiber in which a core component made of stereocomplex polylactic acid containing conductive fine particles is completely covered with a nonconductive sheath component made of a thermoplastic polymer, the core component being 2 It has a cross-sectional shape having one or more sharp protrusions, and the minimum thickness Vi of the nonconductive component formed by the outer periphery of the sheath component and the outer periphery of the core component is 0.5 to 5 μm. Characteristic conductive core-sheath type composite fiber.   The conductive core-sheath composite fiber according to claim 1, wherein the thermoplastic polymer is mainly polyethylene terephthalate.   An electroconductive brush for an electrophotographic image forming apparatus, comprising the electroconductive core-sheath composite fiber according to claim 1.