JP2008185803A - Polyamide conductive thread and brush for electrophotographic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyamide conductive thread suitably used for a cleaning brush for an electrophotographic device, especially, which excels in electric characteristics due to reformed polymer, and which satisfactorily removes transfer residual toner even by one conductive brush, so that an excellent image can be obtained, and which reduces the size of the device and cost, and to provide the brush for the electrophotographic device. <P>SOLUTION: The polyamide conductive thread is a multifilament comprising single fibers composed of a polymer (A) containing electrically conductive particulates by 15 to 45 mass% in polyamide containing a sulfonic acid group, and its resistivity value in atmosphere that temperature and humidity are 25°C and 45%RH is 10<SP>3</SP>to 10<SP>10</SP>Ωcm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a polyamide conductive yarn suitable for various brushes such as a contact charging brush and a photosensitive drum cleaning brush used in an electrophotographic apparatus (copier, facsimile, printer, etc.), and particularly suitable for a cleaning brush. The present invention relates to a brush for an electrophotographic apparatus using at least a part of the polyamide-based conductive yarn and the polyamide-based conductive yarn of the present invention.

  2. Description of the Related Art Conventionally, in electrophotographic apparatuses such as electrophotographic copying machines, cellulosic fibers are often used as conductive yarns used for contact charging brushes, photosensitive drum cleaning brushes, and the like (for example, Patent Document 1). In addition, many polyester and polyamide fibers widely used as synthetic fibers have been proposed that contain conductive fine particles (for example, Patent Document 2).

  Among them, the cleaning brush is important for obtaining a good image, and has a function of removing transfer residual toner. Since the transfer residual toner includes toner having a polarity opposite to the original toner charging polarity, it is difficult to maintain a good cleaning performance by applying a bias to one conductive cleaning brush.

  That is, when the normal charging polarity of the toner is negative, the transfer residual toner is mainly negative, but some toner is inverted to positive by a transfer bias. When cleaning negatively charged toner, a positive voltage is applied for cleaning, but in this case, toner that is reversed to positive cannot be cleaned.

In Patent Document 3, two conductive brushes are used. First, an AC superimposed DC voltage is applied with the upstream conductive brush, the toner charging polarity is aligned, and the downstream conductive brush is used for cleaning. Yes. In Patent Document 4, a DC voltage is applied to the upstream brush. In both cases, two conductive brushes and two types of high-voltage power supplies are required, making it difficult to reduce the size and cost of the apparatus.
JP 2000-355823 A JP 2003-105623 A JP-A-8-248849 Japanese Patent Laid-Open No. 2004-053893

  The present invention solves the above-mentioned problems, and is a polyamide-based conductive yarn suitable for use in a cleaning brush for an electrophotographic apparatus in particular, and has excellent electrical characteristics because the polymer is modified. Polyamide-based conductive yarns that can transfer residual toner well with a single conductive brush, so that good images can be obtained, and the size and cost of the apparatus can be reduced. It is another object of the present invention to provide a brush for an electrophotographic apparatus.

As a result of intensive studies aimed at solving the above problems, the present inventors have reached the present invention.
That is, the gist of the present invention is the following (1) and (2).

(1) A multifilament composed of a single fiber made of a polymer (A) containing 15 to 45% by mass of conductive fine particles in a polyamide containing a sulfonic acid group, and having a temperature and humidity of 25 ° C. and 45% RH Polyamide-based conductive yarn having a specific resistance value in the atmosphere of 10 ³ to 10 ¹⁰ Ω · cm.
(2) A brush for an electrophotographic apparatus using at least a part of the polyamide conductive yarn described in (1).

  Since the polyamide-based conductive yarn of the present invention is made of a polyamide containing a sulfonic acid group, it has excellent electrical characteristics, and even with a single conductive brush, the transfer residual toner can be cleaned well. Therefore, it is particularly suitable for use as a cleaning brush for an electrophotographic apparatus.

  In addition, the brush for an electrophotographic apparatus of the present invention uses the polyamide-based conductive yarn of the present invention for at least a part, so that it has excellent electrical characteristics and can obtain a good image for a long period of time. It is also possible to reduce the size and the price.

Hereinafter, the present invention will be described in detail.
First, the brush for an electrophotographic apparatus referred to in the present invention is various brushes used for an electrophotographic apparatus such as a copying machine, a facsimile, a printer (for example, a laser beam printer), for example, a developing brush, a contact charging brush, and a static eliminating brush. Examples include brushes, cleaning brushes, and toner supply brushes. The polyamide-based conductive yarn of the present invention can be suitably used for a cleaning brush among others.

  Examples of the polyamide forming the polyamide conductive yarn of the present invention include nylon 6, nylon 66, nylon 69, nylon 46, nylon 610, nylon 12, nylon 11, polymetaxylene adipamide, and the like. Is preferred.

  And the polyamide which forms the electroconductive yarn of this invention contains a sulfonic acid group in the above polyamide components. As described above, when the sulfonic acid group is contained in the polyamide component, the polymer is modified and the electrical characteristics are improved.

  In the present invention, the polyamide having a sulfonic acid group is a polyamide in which a sulfonic acid group-containing compound is mixed (blended) in the polyamide, or a sulfonic acid group-containing compound is copolymerized, so that the sulfonic acid group is contained in the polyamide molecule. May be any of those introduced.

  Especially, since the effect of polymer modification is high, it is preferable that the sulfonic acid group-containing compound is copolymerized. Furthermore, it is preferable that 1.0 to 20.0 mol% of the sulfonic acid group-containing compound is copolymerized.

  When the copolymerization amount of the sulfonic acid group-containing compound of the polyamide conductive yarn of the present invention is less than 1.0 mol%, the modification of the polymer becomes insufficient and the effect of excellent electrical characteristics is reduced. On the other hand, if the copolymerization amount of the sulfonic acid group-containing compound exceeds 20.0 mol%, the operability during melting and spinning deteriorates, which is not preferable.

  Examples of the sulfonic acid group-containing compound include sulfoalkali metal salts such as 5-sulfoisophthalic acid, 4-sulfoisophthalic acid, 2-sulfo-para-crezoxyacetic acid, 3-sulfobenzoic acid, and 4-sulfoacetic acid.

  In addition, as long as the modification | denaturation effect of the polymer of this invention is not impaired, you may contain another copolymerization component, various additives, etc.

  Each single fiber constituting the conductive yarn (multifilament) of the present invention contains conductive fine particles. Examples of the conductive fine particles include carbon black, metal powder, metal oxide and the like, and among them, carbon black (acetylene black, ketjen black, etc.) is preferable. The amount to be added is preferably 15 to 45 mass%, more preferably 20 to 35 mass%.

  Conventionally, conductive fibers in which conductive fine particles are uniformly dispersed are difficult to manufacture, and the strength of the obtained fibers is low, resulting in high costs. In other words, carbon black is usually used as the conductive fine particles, but since carbon black has a lower specific heat than thermoplastic resin, the cooling rate after spinning is faster than that of fibers not containing carbon black. The phenomenon that occurs. This phenomenon becomes more prominent as the carbon black content increases. However, due to the high cooling rate, fiber breakage occurs during fiber stiffening and drawing, making it difficult to manufacture, and even if it is obtained, it becomes a low-strength fiber. It was.

  In the present invention, in consideration of such a phenomenon, the properties of the modified polyamide are taken into consideration, and the conditions for the spinning and drawing processes are appropriately selected, whereby the modified polyamide containing conductive fine particles is contained. The fiber which consists only of was able to be obtained.

  That is, in the spinning process, the shape of the spinneret, the spinning speed, and the cooling conditions are optimized to stabilize the fiber shape and prevent stiffening of the fiber due to rapid cooling. By optimizing conditions such as temperature, fibers having practical strength could be stably obtained.

  Thus, the polyamide-based conductive yarn of the present invention is a multifilament composed of a single fiber composed of a polymer (A) containing 15 to 45% by mass of conductive fine particles in a polyamide containing a sulfonic acid group. Each single fiber has a single layer structure in which only the polymer (A) is a constituent polymer and no other non-conductive resin is used.

  As a result, even if the shape of the fiber changes due to use, there is no change in the conductive performance, the conductivity as a whole of the fiber is excellent, and the uniformity of the conductivity is excellent, and it is also advantageous in terms of cost. it can.

Furthermore, the polyamide based conductive yarn of the present invention has a specific resistance value of 10 ³ to 10 ¹⁰ Ω · cm in an atmosphere having a temperature and humidity of 25 ° C. and 45% RH. By setting the specific resistance value within this range, it is possible to obtain fibers suitable for various brushes used in electrophotographic copying machines, electrophotographic printers, and the like.

When the specific resistance value exceeds 10 ¹⁰ Ω · cm, it is difficult to uniformly charge the surface of the photosensitive drum when used as a charging brush for an electrophotographic copying machine, an electrophotographic printer or the like. On the other hand, if the specific resistance value is less than 10 ³ Ω · cm, when there is a defect such as a pinhole in the photosensitive belt layer, a large current flows and a charging failure tends to occur.

  In addition, the polyamide conductive yarn of the present invention is not particularly limited in the cross-sectional shape of the single yarn, and is not only a round shape, but also a polygonal shape such as a triangle or a quadrangle, or a deformed cross-sectional shape such as a flat shape. Also good. Moreover, you may have a hollow part.

  Further, the total fineness (fineness of multifilament) is preferably 50 to 600 dtex, the single fiber fineness is 0.5 to 20 dtex, and the number of single fibers is preferably 10 to 100.

  The polyamide-based conductive yarn of the present invention is a two-step method in which an unstretched yarn is wound once after spinning and then subjected to stretching in a stretching step. After spinning, the unstretched yarn is continuously stretched without being wound once. Any of the one-step methods for performing may be adopted.

  The method for producing the polyamide-based conductive yarn of the present invention will be described with reference to an example of a method for producing by a two-step method.

  First, a sulfonic acid group-containing compound is added at the time of polymerization of nylon 6 to obtain nylon 6 having a sulfonic acid group introduced into the molecule, which is formed into a chip (referred to as chip 1). As a method for kneading and melting the conductive fine particles and nylon 6, the conductive fine particles can be directly kneaded using, for example, a biaxial extruder, but once the master containing the conductive fine particles in a high concentration is used. It is preferable to knead the chips after making them, because more uniform kneading can be performed. Therefore, a chip (referred to as chip 2) containing conductive fine particles at a high concentration in nylon 6 having a sulfonic acid group introduced into the molecule obtained as described above is prepared. For example, the polymer (A) is obtained by kneading and melting with an extruder, and the polymer (A) is extruded from a spinneret to perform melt spinning. And an unstretched multifilament yarn is obtained, without extending | stretching substantially.

  The method of melt spinning is not particularly limited, and can be performed by a conventional method. The spinning temperature is preferably in the range of Tm + 10 to Tm + 80 ° C. with respect to the melting point Tm of the polymer (A). If the spinning temperature is high, the thermoplastic polymer undergoes thermal decomposition, which makes smooth spinning difficult and the physical properties of the resulting filaments inferior. On the other hand, if the spinning temperature is too low, undissolved materials remain, and uniform kneading cannot be performed.

  Then, at the time of spinning, the slit shape of the spinneret is selected so as to obtain the cross-sectional shape to be obtained, and spinning is performed. The spun filament is cooled with cooling air of 0 to 100 ° C, preferably 15 to 40 ° C. If the cooling temperature is too low, the temperature control and workability will be difficult, and if it is too high, the cooling will be insufficient and the yarn quality of the filament finally obtained will be inferior.

Next, the cooled and solidified filament is temporarily wound at 500 to 1500 m / min without being substantially drawn.
And although an unstretched multifilament yarn is stretched, it is preferable to perform thermal stretching, in which stretching is performed while heat treatment. The stretching temperature is preferably 50 to 200 ° C., and the stretching ratio is preferably 50 to 80% of the maximum stretching ratio (the ratio at which the unstretched multifilament yarn is cut by stretching). If the draw ratio is less than 50% of the maximum draw ratio, the elongation remains too much, so that there is a tendency that it is difficult to obtain a conductive multifilament yarn having substantial strong elongation. When the draw ratio exceeds 80% of the maximum draw ratio, it tends to be difficult to obtain a conductive multifilament yarn having a uniform fineness in the yarn length direction.

  Further, it is preferable to perform the heat stretching so that the heat treatment time during the heat stretching is 0.02 seconds or more. By setting the heat treatment time during stretching to 0.02 seconds or more, a sufficient amount of heat can be applied so that each single fiber is equally stretched, and the fibers are slowly and uniformly stretched. As a result, even if the content of the conductive fine particles is relatively high and the fiber has high rigidity, it becomes possible to perform uniform stretching without causing yarn breakage during stretching.

  Specifically, the heat stretching process is performed as shown in FIG. FIG. 1 is a schematic process diagram showing one embodiment of the method for producing a conductive multifilament yarn of the present invention. First, the unstretched multifilament yarn 1 is drawn through the guide roller 2 to the tension roller 4. The temperature of the box heater 3 provided below the guide roller 2 is set to 50 ° C. to 200 ° C., and the time during which heat is applied is set to 0.02 seconds or more. Stretching is performed between the guide roller 2 and the pulling roller 4. Instead of the box-type heater 3, a plurality of heating rollers may be used to perform a heat stretching process between the heating rollers. Moreover, it is preferable that the tension | tensile_strength (drawing tension | tensile_strength) loaded on an undrawn multifilament yarn at the time of extending | stretching shall be 1.0 cN / dtex or less.

  Next, it is preferable to perform relaxation heat treatment after the hot stretching or continuously after the stretching. In this relaxation heat treatment step, the conductive fine particles that are uniformly arranged in the previous heat stretching step but in which the dense chain state has been relaxed are subjected to a specific low tension at a specific temperature and time. By performing the relaxation heat treatment, the single fibers are contracted to form a dense chain again. Thereby, while improving electroconductivity, the dispersion | variation in the electrical resistance value between single fibers can also be reduced more.

  Usually, the heat treatment after stretching is performed in a tensioned state between the rollers, so that the heat shrinkage rate of the fiber is lowered, but the effect of bringing the conductive fine particles into a dense chain state again as described above is extremely high. poor.

  Therefore, in the present invention, it is preferable to perform a relaxation heat treatment for 0.5 seconds or more with a tension of 0.5 cN / dtex or less, and among them, the tension is preferably 0.2 cN / dtex or less, more preferably 0.1 cN / dtex. It is as follows. When the tension during heat treatment exceeds 0.5 cN / dtex, the yarn is subjected to tension heat treatment, and the thermal shrinkage of the fiber is reduced, but it is difficult to make the conductive fine particles into a dense chain state again. .

  Further, the relaxation heat treatment time is preferably 0.5 seconds or more, more preferably 1 second or more, and further preferably 2 seconds or more. If the time is less than 0.5 seconds, the fibers cannot be sufficiently heat-shrinked, so that the effect of bringing the conductive fine particles into a dense chain state again becomes poor, and the variation in the electric resistance value between the single fibers is reduced. The effect is also reduced. Also, thermal stability cannot be imparted.

  The relaxation heat treatment temperature is preferably 70 to 200 ° C, more preferably 100 to 190 ° C, and further preferably 140 to 180 ° C. When the relaxation heat treatment temperature is less than 70 ° C., it is difficult to sufficiently heat-shrink the fiber, so that the relaxation heat treatment becomes insufficient and it becomes difficult to achieve the above-described effects. On the other hand, if the relaxation heat treatment temperature exceeds 200 ° C., heat fusion may occur, which is not preferable.

  Such relaxation heat treatment may be performed using the heat treatment apparatus 6 (an apparatus having the saddle type heater 5 and the heating roller 7) shown in FIG. The multifilament yarn that has passed through the heat treatment apparatus 6 is wound up by the traveler 8 to obtain a conductive multifilament yarn.

Next, the brush for an electrophotographic apparatus of the present invention will be described.
The brush of the present invention uses at least a part of the polyamide-based conductive yarn of the present invention, and the proportion of the polyamide-based conductive yarn of the present invention in the brush is preferably 50% by mass or more, It is preferable to consist only of the polyamide-based conductive yarn of the present invention. The form of the brush is not particularly limited, but after weaving the fiber of the present invention into a pile fabric, the pile fabric is cut into a tape shape and wound around the surface of a cylindrical shaft in a spiral shape to form a brush. The thing which was done is mentioned. In addition, the fibers of the present invention are cut into short fibers and bonded to the fabric surface by flocking, and the fabric is similarly taped and wound around the surface of the shaft in a spiral shape to form a brush.

  Then, the brush of the present invention has a heat set by hot water treatment in order to open the fibers on the brush surface and prepare the brush surface after winding the pile fabric or the like spirally around the surface of the shaft as described above. Preferably it is done.

Next, the present invention will be described specifically by way of examples.
The measurement method and evaluation of various values in the examples and comparative examples were performed as follows.
[Resistivity]
Twenty test pieces having a length of 10 cm were collected at intervals of 100 m along the length direction of the conductive yarn of the present invention. Using a resistance measuring device “SM-10E” manufactured by Toa Denpa Kogyo Co., Ltd. under a measurement environment of 25 ° C. and 45% RH, applying a voltage of 50 V between 10 cm test pieces (between both ends) The electrical resistance value R (Ω) was measured, the specific resistance value (ρ) (Ω · cm) of 20 test pieces was obtained by the following formula, and the average value was taken as the specific resistance value.
Specific resistance (ρ) (Ω · cm) = R (Ω) × (S / L)
In the formula, R represents the electrical resistance value (Ω) of the test piece, S represents the cross-sectional area (cm ² ) of the test piece, and L represents the length (10 cm) of the test piece. However, here, S = Dtex / (1000000 × d), where Dtex is a value obtained by directly replacing the total decitex number of the conductive yarn as mass (g), and d is the fiber density.
[Cleaning evaluation]
Weaving a pile tape with a pile density of 1000 / 2.54 cm, a pile length of 7 mm, and a fabric width of 15 mm using only the obtained polyamide-based conductive yarn, and then spiraling on a cylindrical surface with a diameter of 6 mm A brush having a diameter of 14 mm was created.
The brush was mounted as a cleaning brush for an electrophotographic copying machine, and cleaning was performed under the conditions of a negatively charged OPC drum, negatively charged toner, a process speed of 100 mm / sec, a brush rotation speed of 60 rpm, a counter rotation with respect to the drum, and a bite of 1 mm.
At this time, the toner amount before passing the cleaning brush (Pw) and the toner amount after passing (Aw) were measured and calculated as cleaning property (Vc) = Aw / Pw.
When Vc was less than 0.1, it was evaluated as ◯, and when it was 0.1 or more, it was rated as x.
[Evaluation of spinning and drawing operability]
The operation was carried out continuously for 24 hours, and the following three-stage evaluation was made based on the number of yarn breakage per spindle.
○: The total number of yarn breaks during spinning and drawing is 0 to 2 times Δ: The total number of yarn breaks during spinning and drawing is 5 times or less, or any number of yarn breaks is 3 or more ×: Spinning and drawing The total number of thread breaks at the time is 6 times or more

Example 1
Copolymerization of 3.0% by mass of 5-sulfoisophthalic acid, nylon 6 having a relative viscosity of 2.54 (measured at a concentration of 1 g / d1 and a temperature of 25 ° C. using 96% sulfuric acid as a solvent), carbon black as conductive fine particles Of 23 mass%. Then, it is supplied to an extruder type melt extruder, melted at a spinning temperature of 255 ° C., discharged from a spinneret having 96 spinning hole diameters of 0.35 mm, and undrawn yarn is wound at a take-up speed of 600 m / min. I took it.
Next, the obtained undrawn yarn was supplied to a heat drawing machine and heated with a box heater (drawing temperature 150 ° C.) at 150 ° C. so that the heat treatment time was 0.1 seconds and the drawing tension was 0.5 cN / dtex. The film was stretched at 60% of the maximum stretching ratio, then supplied to a relaxation heat treatment machine and heated with a vertical heater (relaxation heat treatment temperature 170 ° C.) at 170 ° C., with a heat treatment time of 3 seconds and a tension of 0.05 cN / dtex. Thermal relaxation treatment was performed to obtain a 220 dtex / 96 f polyamide conductive yarn.

Examples 2-9, Comparative Examples 1-3
Except that the copolymerization amount of 5-sulfoisophthalic acid and the carbon black content were changed as shown in Table 1, spinning / drawing / relaxation heat treatment was performed in the same manner as in Example 1 to obtain a polyamide-based conductive yarn. .

  Table 1 shows the characteristic values and evaluation results of the polyamide conductive yarns obtained in Examples 1 to 9 and Comparative Examples 1 to 3.

As is clear from Table 1, the polyamide-based conductive yarns obtained in Examples 1 to 9 each have a specific resistance value in the range of 10 ³ to 10 ¹⁰ Ω · cm, and have a cleaning property (Vc). It was less than 0.1, and the cleaning property of the brush made of polyamide conductive yarn was good.
On the other hand, since the polyamide conductive yarn of Comparative Example 1 was a polyamide containing no sulfonic acid group, the specific resistance value was 10 ^6.6 Ω · cm, but the cleaning property (Vc) was inferior. The polyamide conductive yarn of Comparative Example 2 had a specific resistance value of 10 ¹³ Ω · cm because the carbon black content was too small, and was inferior in cleaning properties. The polyamide conductive yarn of Comparative Example 3 was inferior in operability during spinning and drawing because the carbon black content was too large.

It is a schematic process drawing which shows one embodiment of the manufacturing method of the polyamide-type electroconductive yarn of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Undrawn yarn multifilament yarn 2 Guide roller 3 Box-type heater 4 Pulling roller 5 Vertical heater 6 Heat treatment device (device having vertical heater 5 and heating roller 7)
7 Heating roller 8 Traveler

Claims (4)

A multifilament composed of a single fiber made of a polymer (A) containing 15 to 45% by mass of conductive fine particles in a polyamide containing a sulfonic acid group, in an atmosphere having a temperature and humidity of 25 ° C. and 45% RH Polyamide-based conductive yarn having a specific resistance value of 10 ³ to 10 ¹⁰ Ω · cm. The polyamide conductive yarn according to claim 1, wherein the polyamide containing a sulfonic acid group is a polyamide obtained by copolymerizing a sulfonic acid group-containing compound in an amount of 1.0 to 20.0 mol%. The polyamide conductive yarn according to claim 1 or 2, wherein the polyamide is nylon 6. A brush for an electrophotographic apparatus using at least a part of the polyamide-based conductive yarn according to claim 1.