JP2006336141A - Electrically conductive crimped yarn and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide electrically conductive crimped yarn affording uniform and clear printed images by the use as electrically conductive yarn for the brush of image formation equipment, and to provide a method for producing the crimped yarn. <P>SOLUTION: The method for producing the electrically conductive crimped yarn comprises carrying out a false-twist texturizing of sheath/core conjugate fiber with a twist multiplier of below 0.85 at a temperature lower than the respective melting points of both core and sheath polymers, wherein the conjugate fiber is composed of an electrically conductive substance-containing polymer as the core and an electrically conductive substance-free polymer as the sheath with the core fully covered with the sheath. The electrically conductive crimped yarn thus obtained is provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a conductive crimped yarn. More specifically, a brush used in an image forming apparatus such as a laser printer, for example, a static elimination brush for neutralizing the photosensitive drum surface after image transfer, a charging brush for charging the photosensitive drum surface, and residual toner on the photosensitive member. The present invention relates to a method for producing a conductive crimped yarn that can be suitably used as a cleaning brush for removal.

  As the fibers for brushes used in electrophotographic recording type dry copying machines, facsimiles, printers, etc., vinylon conductive yarns, nylon conductive yarns or polyester conductive yarns containing cellulose fibers or conductive carbon are used (for example, Patent Documents 1 to 4).

  Conventionally, the conductive yarn remains as a straight filament yarn and is used as a raised fiber of a cut pile knitted fabric or a raised fabric raised by tufting or raising, and further used as a conductive brush. Most of them.

  However, when the conductive brush is brought into contact with a photosensitive drum or the like, it becomes a point contact, so that there are discharge spots, charged spots and cleaning spots, and there is a problem that a uniform and clear printed image cannot be obtained. For this reason, a method of increasing the napping density of a pile knitted fabric or the like is conceivable, but this method also has a limit.

JP-A-9-491117 JP 2000-355823 A JP 2000-160427 A JP 2003-66669 A

  In view of the above-described background art, the present invention provides a crimped conductive yarn used for a brush, whereby the tip of a fiber constituting the conductive yarn is bent or curved, and the contact area with a photosensitive drum or the like is increased. It was considered that the above problem could be solved by the effect of increasing the area of charge removal, charging and cleaning.

However, when trying to apply crimping to the above-mentioned conductive yarn to false twisting, there are many problems that the quality of the conductive yarn is significantly reduced or the yarn is broken at the time of processing. A characteristic crimped yarn could not be obtained.
Accordingly, an object of the present invention is to provide a conductive crimped yarn that can be used as a conductive yarn for a brush of an image forming apparatus to obtain a uniform and clear printed image, and a manufacturing method thereof.

  As a result of repeated studies to solve the above problems, the inventor of the present invention has made conductive fibers composed of a composite fiber containing a polymer containing a conductive substance as a constituent component, and the fibers are melted when false twisting is applied thereto. It has been found that there is a problem of wearing or peeling off from other components constituting the composite fiber. In addition, since a polymer containing a conductive substance generally has a low melting point or a low viscosity for the purpose of improving the dispersibility of the conductive substance in the polymer, Due to heat and stress, not only the composite fiber in which the polymer component is exposed on the fiber surface but also the composite fiber in which the polymer component is not exposed on the fiber surface, the polymer component covering the polymer fiber is damaged. Was found to be due to elution on the surface and causing the above problems.

  Thus, according to the present invention, there is provided a core-sheath composite fiber in which a polymer containing a conductive substance is arranged in the core part, a polymer not containing a conductive substance is arranged in the sheath part, and the core part is completely covered by the sheath part. There is provided a method for producing a conductive crimped yarn, characterized in that false twisting is performed at a processing temperature lower than the melting point of the polymer of the core and sheath at a twisting coefficient of 0.85 or less.

  In addition, the core is composed of a core-sheath composite fiber in which a polymer containing a conductive substance is disposed in the core part, a polymer not containing a conductive substance is disposed in the sheath part, and the core part is completely covered with the sheath part. An electrically conductive crimped yarn characterized by being subjected to false twisting of 0.85 or less is provided.

  According to the production method of the present invention, a conductive crimped yarn having a high quality crimp can be stably produced. Further, according to the conductive crimped yarn of the present invention, a uniform and clear printed image can be obtained by using it as a conductive yarn for a brush of an image forming apparatus.

  The conductive crimped yarn of the present invention is a core-sheath composite in which a polymer containing a conductive substance is arranged in the core part, a polymer not containing a conductive substance is arranged in the sheath part, and the core part is completely covered by the sheath part It is composed of fibers. With such a structure, when used as a brush or the like, the conductive material does not drop and the conductive performance does not deteriorate. In general, a low melting point or low viscosity polymer is used as a polymer constituting the core part for the purpose of improving the dispersibility of the conductive material, and crimping is imparted to the composite fiber in which the polymer is exposed on the surface. When the false twisting is performed at a sufficient temperature, there is a problem that the polymer melts and the fibers are fused. On the other hand, since the core part of the conjugate fiber of the present invention is completely covered with the sheath part, the above-mentioned problem is unlikely to occur.

  Even if the thickness of the sheath portion is too small, the sheath portion may be damaged by heat or tightening stress during false twisting, and the core portion may be exposed by false twisting. On the other hand, when the thickness of the sheath portion is too large, the conductive performance tends to decrease. Therefore, it is preferable that the “minimum thickness” at which the thickness of the sheath portion is the smallest in the fiber cross section is 2 to 6 μm.

  Specifically, as the cross section of the composite fiber, as shown in FIG. 1 (a), a cross section in which a circular core is covered with a sheath, or a core as shown in (b) to (d). Although the part has the protrusion which adjoins the surface of the core-sheath composite fiber, the thing which has a cross section like (b)-(e) is preferable at the point which exhibits high electroconductivity. In the above (b) to (d), the core portion has three, four, and six protrusions, but the number of protrusions is not limited to this, and 3 to 16 protrusions are preferable. More preferably, it is 3-8.

  Examples of the polymer constituting the core in the present invention include polyolefins such as polyethylene, polypropylene, polystyrene, and polybutadiene, polyamides such as nylon-6 and nylon 6,6, and copolymerized polyamides containing these as a main component, polyethylene terephthalate, and poly Examples thereof include polyesters such as butylene terephthalate or copolymer polyesters containing these as main components, and among them, polyolefins, particularly polyethylene, are preferable. Two or more of these may be used in combination.

  As the conductive substance to be contained in the core, conductive carbon black, a conductive metal compound, or the like can be used. Examples of the carbon black include acetylene black, oil furnace black, thermal black, channel black, and ketjen black. On the other hand, as the conductive metal compound, a conductive metal oxide is mainly used, and stannic oxide and zinc oxide having excellent whiteness are particularly preferable. Here, stannic oxide includes stannic oxide containing a small amount of antimony compound, and conductive metal composite obtained by coating the surface of titanium oxide particles with stannic oxide containing a small amount of antimony compound. It is. Zinc oxide also includes conductive zinc oxide in which a small amount of aluminum oxide, lithium oxide, indium oxide and the like are dissolved. These can be used by being dispersed in a polymer constituting the core as a fine powder.

  On the other hand, examples of the polymer constituting the sheath include polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides such as nylon-6 and nylon-6,6, etc., and a small amount of a third component is copolymerized therewith. It may be a copolymer. Of these, polyethylene terephthalate having an intrinsic viscosity of 0.50 to 0.70 is preferable from the standpoint of yarn production. Moreover, you may make the said polymer contain arbitrary additives, for example, a matting agent, a coloring agent, antioxidant, a dyeability improving agent, an antistatic agent etc. as needed.

  In the production method of the present invention, it is important that the yarn comprising the above-described core-sheath composite fiber is false twisted at a processing temperature lower than the melting point of the polymer of the core part and the sheath part with a twist coefficient of 0.85 or less. It is. This makes it possible to stably produce high quality conductive crimped yarn that has not been obtained conventionally.

  That is, as described above, a polymer having a lower melting point or a lower viscosity than the sheath part is generally used for the core part of the composite fiber, and false twisting is particularly required at a temperature higher than the melting point of the polymer of the core part and the sheath part. If false twisting is performed at a temperature higher than the core having a low melting point from the viewpoint, the core melts and the cross-sectional shape of the composite fiber is deformed, the sheath is damaged, or the core and the sheath are peeled off. Problems occur. Further, when the false twisting coefficient is larger than 0.85, the tightening stress due to twisting is remarkably increased, the fiber cross section is crushed and deformed, and the sheath part is easily broken. As a result, not only the quality of the conductive crimped yarn but also the conductive performance is significantly reduced.

  In the present invention, the yarn comprising the core-sheath composite fiber to be false twisted may be POY (highly oriented undrawn yarn) or FOY (drawn yarn). Further, the false twisting of the present invention may be one in which POY is stretched false twisted or FOY false twisted. However, false twisting of FOY is preferable because deformation of the fiber cross section is less likely to occur.

  In order to produce POY that is a composite fiber as described above, for example, the core and sheath polymers are melted, discharged from a composite spinneret, cooled, and oiled, and then 500 to 2,000 m / min. Wind the undrawn yarn once at a speed. It can be obtained by placing the wound undrawn yarn on a drawing machine and drawing about 1.5 to 5 times.

Further, by performing heat treatment again after false twisting, not only can the crimping rate be further adjusted, but also the untwisting torque and thermal shrinkage can be lowered.
The lower the melting point of the polymer constituting the core part, the lower the crimping rate can be adjusted, and the higher the fineness of the conductive yarn, the higher the false twisting, the crimping can be imparted.

  According to the production method of the present invention described above, a conductive crimped yarn having a high quality without deformation of the cross section of the fiber and having no sheath damage is subjected to false twisting with the false twisting coefficient described above. Obtainable. In addition, when this conductive crimped yarn is used as a conductive brush of an image forming apparatus, the tip of the core-sheath composite fiber has a bent or curved shape due to crimping, compared with a conventional straight conductive yarn, The contact area between the fiber tip and the photosensitive drum and the like is increased, and the area of charge removal, charging, and cleaning is increased. As a result, a uniform and clear printed image can be obtained.

  Even if the crimp rate of the conductive crimped yarn is too high, the orientation and arrangement of the naps are liable to be disturbed when a napped fabric for a brush is used. For example, the toner to be cleaned accumulates inside the brush. Cheap. On the other hand, even if the crimp rate is too low, the above-described effects due to crimping cannot be sufficiently exhibited. Accordingly, the crimp rate is preferably 2 to 8%.

Moreover, the cross-sectional electrical resistance value of the conductive crimped yarn is preferably 10 ² to 10 ¹¹ Ω / cm. Although it varies depending on the type of image forming apparatus, it is easy to obtain uniform charging, static elimination, and cleaning effects by setting the cross-sectional electric resistance value within the range.

  In order to obtain a conductive brush using the conductive crimped yarn, for example, a raised fabric using the conductive crimped yarn at least in a raised portion is attached and attached to a flat surface, or this is spiraled to a support (shaft). Wrapped into a brush shape. Thereafter, napping treatment and shearing treatment are performed to obtain a conductive brush for an image forming apparatus.

Hereinafter, the present invention will be described in more detail with reference to examples. The evaluation method is as follows.
(1) Intrinsic viscosity of polyester Measured at 25 ° C. using orthochlorophenol.
(2) Print image quality A test chart issued by the Electrophotographic Society was copied, and sensory evaluation was performed by five people on the uniformity and clearness of the print image quality with one printing.

[Example 1]
Conductive polymer chips (melting point 130 ° C.) obtained by adding 30 parts by weight of furnace-based conductive carbon black to 70 parts by weight of polyethylene (Sumitomo Chemical Sumikasen G-807) and melting and mixing, inherently A polyethylene terephthalate chip (manufactured by Teijin Fiber Limited) having a viscosity of 0.64 and a melting point of 256 ° C. was spun using a composite spinneret at a spinning temperature of 290 ° C. and a take-up speed of 1200 m / min to obtain an undrawn yarn. This unstretched yarn was heat-drawn at a preheating of 100 ° C., a heat setting temperature of 180 ° C. and a draw ratio of 3.1 times, and a drawn yarn of a core-sheath composite fiber having a cross section of FIG. Obtained. In addition, the minimum thickness of the sheath part of this core-sheath composite fiber was 3 μm.

  Next, 8 drawn yarns were combined, and using a false twisting machine equipped with a spindle type twisting device, the working temperature was 125 ° C., the number of false twists was 1741 T / m (temporary twisting factor 0.83), False twisting was performed at a speed of 100 m / min to obtain a conductive crimped yarn of 250 dtex 40 filaments having a crimp rate of 7%. Although the cross section of the composite fiber constituting the crimped yarn was observed with a microscope, it had a substantially uniform cross section, and no damage to the sheath was observed.

Further, a twisted yarn of 100 T / m is applied to the crimped yarn, a napped fabric is prepared using a pile loom, and this is slit into a 20 mm wide tape and wound around a metal shaft in a spiral shape. A conductive brush was prepared by cutting and making the height constant.
When this conductive crimped yarn brush was used in an image forming apparatus, the printed image was excellent in both uniformity and sharpness.

[Comparative Example 1]
A conductive brush was prepared and used in an image forming apparatus in the same manner as in Example 1 except that the combined drawn yarn was not subjected to false twisting. The obtained printed image was inferior to the printed image of Example 1 in both uniformity and sharpness.

  According to the production method of the present invention, a conductive crimped yarn having a high quality crimp can be stably produced. Further, according to the conductive crimped yarn of the present invention, a uniform and clear printed image can be obtained by using it as a conductive yarn for a brush of an image forming apparatus. For this reason, both the conductive crimped yarn and the method for producing the same of the present invention have extremely high industrial utility value.

It is a figure which shows the example of the cross-sectional shape of the composite fiber which comprises the electrically conductive crimped yarn of this invention.

Explanation of symbols

1 Core part 2 Sheath part 3 Minimum thickness of sheath part

Claims (7)

  A thread comprising a core-sheath composite fiber in which a polymer containing a conductive substance in the core part, a polymer not containing a conductive substance in the sheath part is arranged, and the core part is completely covered by the sheath part, A process for producing a conductive crimped yarn, characterized in that false twisting is performed at a processing temperature lower than the melting point of the polymer of the sheath at a twisting coefficient of 0.85 or less.   2. The conductive crimped yarn according to claim 1, wherein a joint portion close to the surface of the core-sheath conjugate fiber is provided in the core portion of the core-sheath conjugate fiber, and a distance from the proximity portion to the surface is 2 to 6 μm. Production method.   The method for producing a conductive crimped yarn according to claim 1 or 2, wherein the false twisting is performed by a spindle type twisting device.   It consists of a core-sheath composite fiber in which a polymer containing a conductive substance in the core part and a polymer not containing a conductive substance in the sheath part are arranged, and the core part is completely covered by the sheath part. Conductive crimped yarn having a false twisting process of 85 or less.   The conductive crimped yarn according to claim 4, wherein the core portion of the core-sheath composite fiber has a joint portion close to the surface of the core-sheath composite fiber, and the distance from the proximity portion to the surface is 2 to 6 µm. .   The conductive crimped yarn according to claim 4 or 5, wherein the crimp rate is 2-8.   The electroconductive brush which uses the electroconductive crimped yarn in any one of Claims 4-6 for at least one part.

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