JP2008144300A - Electrically conductive multifilament yarn - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrically conductive multifilament yarn having a low change in electrical resistivity and rigidity to a temperature-humidity change in a heat treatment process in a brush production or long-term use, and excellent electrical resistivity and shape stability in use as a brush for contact electrification and cleaning and carrying out excellent electrification or cleaning for a long period of time. <P>SOLUTION: The electrically conductive multifilament yarn includes a single fiber composed of nylon 12 containing conductive fine particles, has a shrinkage percentage in hot-water of ≤10%, a variation quantity of logarithmic value of electrical resistivity of ≤0.3 in each environment of at 10°C at 30% RH, at 20°C at 65% RH, and at 40°C at 90% RH, and a percentage change of Young's modulus of ≤30%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to 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 (copying machine, facsimile, printer, etc.).

  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 and photosensitive drum cleaning brushes. Also, many polyester and polyamide fibers widely used as synthetic fibers have been proposed that contain conductive fine particles.

  Patent Documents 1 and 2 propose a composite fiber composed of two types of thermoplastic polymers (polyester and polyamide) having different melting points and containing a titanium oxide having a conductive film in the polymer on the low melting point side. Yes. However, although these conductive fibers have improved conductivity, the hot water shrinkage rate is as high as about 20%. Therefore, the shape of the conductive fiber is not limited when it is used for a heat treatment process or a contact charging brush. In addition, the electrical resistance value varied due to the change of the form, which was unsuitable for the contact charging brush using these conductive yarns.

  Patent Document 3 proposes a conductive cellulose fiber in which a hydrophobic functional group is introduced into a cellulose conductive yarn so that a stable electric resistance value can be expressed against changes in humidity.

Patent Document 4 proposes a conductive cellulosic fiber in which variation in specific resistance value is reduced to within 10 ³ Ω · cm by adding two or more kinds of conductive fine particles to the fiber.

  The above two cellulosic fibers also have not been sufficiently improved in stability against humidity and variation in electric resistance value. That is, contact charging brushes and the like are processed or used in an environment with large changes in temperature and humidity. Therefore, the change in the fiber form caused by the change in temperature and humidity in the environment causes a change in the chain state of the conductive fine particles, and the electric resistance value. Appears as a change.

  Therefore, even if it has a suitable electrical resistance value at the beginning of the production, these values decrease during the heat treatment process and the long-term use when creating the contact charging brush, However, it was impossible to solve the drawback that the image difference became large and an image failure occurred.

  Moreover, in patent document 5, in order to obtain the electroconductive multifilament yarn which shows the stable electrical resistance value with respect to the temperature-humidity change in the heat treatment process at the time of brush preparation, etc. or long-term use, undrawn yarn is made into specific conditions There has been proposed a method of performing a relaxation heat treatment after the heat stretching treatment.

  However, since polyamide and polyester, which are polymers that form multifilaments, absorb moisture over time, it is inevitable that the electrical resistance value changes due to the influence of adsorbed water under high humidity conditions.

JP 57-6762 A JP 7-102437 A Japanese Patent Publication No. 1-229887 JP-A-9-49116 JP 2003-105623 A

  The present invention solves the above-described problems, and the change in electrical resistance and rigidity is small with respect to temperature and humidity changes during the heat treatment process during brush production and long-term use, and the brush for contact charging and cleaning When used as, it is a technical problem to provide a conductive multifilament yarn that is excellent in electrical resistance and form stability and can be charged and cleaned for a long period of time.

The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above problems.
That is, the present invention is a conductive multifilament yarn composed of a single fiber made of nylon 12 containing conductive fine particles, the hot water shrinkage is 10% or less, 10 ° C., RH 30%, 20 ° C., Conductive multifilament, characterized in that the change in logarithmic value of electrical resistance in each environment of RH 65%, 40 ° C., and RH 90% is 0.3 or less and the change rate of Young's modulus is 30% or less The main point is yarn.

  The conductive multifilament yarn of the present invention exhibits a stable electrical resistance value for a long time even when repeatedly subjected to temperature and humidity changes, and the change in rigidity is small, so that when used as a brush for contact charging, a good image is obtained for a long time. It is possible to obtain stably. Further, even when used for a cleaning brush, good cleaning can be performed for a long time, and it can be suitably used for various brushes for an electrophotographic apparatus.

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 in 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 cleaner. A brush or a brush for static elimination is mentioned. The conductive multifilament yarn of the present invention can be suitably used for all of these electrophotographic brushes, and among them, can be suitably used for contact charging brushes.

  The multifilament yarn of the present invention is composed of a single fiber made of nylon 12 containing conductive fine particles.

  Examples of the conductive fine particles include carbon black, metal powder, metal oxide, and the like. Among these, carbon black is preferable. The content is preferably 15 to 45% by mass of the fiber mass, more preferably 20 to 35% by mass. If the content of the conductive fine particles is less than 15% by mass, it is difficult to obtain the conductivity necessary for the intended use. On the other hand, when the content of the conductive fine particles exceeds 45% by mass, the spinnability is remarkably lowered and it becomes difficult to obtain fibers.

  The single fiber constituting the conductive multifilament yarn of the present invention is preferably made of only nylon 12 in which the conductive fine particles as described above are dispersed substantially uniformly. That is, it is possible to obtain uniform conductive performance by using a single-component type as described above, rather than a composite fiber made of nylon 12 containing conductive fine particles and nylon 12 containing no conductive fine particles. It is easy and preferable.

  Generally, the conductive yarn made of polyamide adsorbs about 0.4 to 5.0% of moisture due to environmental humidity. Therefore, although the electric resistance value of the conductive yarn is related to both the dispersion state of the conductive fine particles and the electric resistance value of the adsorbed water, the dispersion state of the conductive fine particles is a main factor in a humidity region of approximately 70% or less. .

  Further, the dispersion state of the conductive fine particles also changes when the fiber form changes. That is, the change in the fiber form caused by the heat treatment process at the time of creating the brush and the change in temperature and humidity in the usage environment causes a change in the dispersion state of the conductive fine particles, causing a change in the electrical resistance value. This is due to the release of residual strain based on deformation received during spinning or stretching, and the change in shape (thermal contraction difference) in which oriented molecules return to the minimum energy state, depending on the heat treatment process at the time of creation and the temperature and humidity changes in the usage environment. It is thought to be triggered.

  In general, charging brushes and cleaner brushes are made by weaving conductive yarn as a pile and then spirally wound around a cylindrical surface to form a brush. However, in order to prepare the pile, heat setting is performed by hot water treatment. Further, when used in a copying machine or the like as described above, the use environment is severe and a large temperature and humidity change is received.

  The hot water shrinkage of the conductive yarn spun and stretched by a normal method is as high as about 10 to 50%. Therefore, when such a fiber is used, even if the dispersion state of the conductive fine particles in the fiber before making the brush is stable, it is in a stage where it is heat set as a brush or shrinks during use. By changing, the dispersion state of the conductive fine particles changes. Due to the change in the dispersion state of the conductive fine particles, the electric resistance value varies. Such a phenomenon is a cause of image failure.

  Therefore, the conductive multifilament yarn of the present invention reduces changes in electrical resistance value and stiffness due to wet heat treatment, and is excellent in electrical resistance value and stability of form even when used for a long period of time. When used as a contact charging brush, a good image can be obtained for a long period of time, and when used as a cleaning brush, a good cleaning effect can be obtained for a long period of time.

  The polymer forming each single fiber of the multifilament yarn of the present invention needs to be nylon 12. Nylon 12 is hydrophobic and has a low moisture content of about 1% even when the environment changes, and has excellent shape stability. Therefore, the multifilament yarn made of these single fibers is resistant to changes in temperature and humidity. It shows stable electrical resistance and rigidity.

  And the hot water shrinkage | contraction rate of the electrically conductive multifilament yarn of this invention is 10% or less, and it is preferable that it is 6.0% or less especially.

  When the hot water shrinkage rate exceeds 10%, the shape of the single fiber changes when heat is applied to the conductive multifilament yarn, and the dispersion state of the conductive fine particles changes, resulting in a large variation in electrical resistance value. Therefore, it is not preferable.

Note that the hot water shrinkage rate is 100 cm, and the sample is immersed in hot water at 80 ° C. for 30 minutes according to the hot water immersion method of JIS-L-1042, dehydrated with a centrifugal dehydrator, and then dried (20 Air-dry at 15 ° C. for 15 hours), measure the sample length L (cm) at that time, and calculate by the following formula.
Hot water shrinkage (%) = [(100−L) / 100] × 100

  The amount of change in the logarithmic value of the electrical resistance value in each environment of 10 ° C., RH 30%, 20 ° C., RH 65%, 40 ° C., and RH 90% is shown as the stability of the electrical resistance value of the conductive multifilament yarn of the present invention. Is 0.3 or less, and preferably 0.2 or less. When the amount of change in the logarithmic value of the electrical resistance value of the multifilament yarn exceeds 0.3, the electrical resistance value changes greatly due to environmental changes. When these multifilament yarns are used in a charging brush, a uniform image can be obtained over a long period of time. It will be something that cannot be obtained.

  In the present invention, the electrical resistance value is measured as follows. First, 20 test pieces of 10 cm are collected every 100 m along the length direction of the multifilament yarn, and left for 15 hours in each environment. Applying a voltage of 500 V between the test pieces (between both ends) and using a resistance measuring device “SM-10E” manufactured by Toa Denpa Kogyo Co., Ltd. in each environment, the electrical resistance value (Ω / cm) Are measured, and the average value of 20 sample pieces is taken as the electric resistance value.

  The amount of change in the logarithmic value of the electric resistance value is obtained by calculating the difference between the largest value and the smallest value in each environment by logarithmically converting the electric resistance value measured in each environment.

  Next, in the conductive multifilament yarn of the present invention, the change rate of Young's modulus in each environment of 10 ° C., RH 30%, 20 ° C., RH 65%, 40 ° C., and RH 90% is 30% or less, especially 20% or less. It is preferable that When the change rate of Young's modulus exceeds 30%, the stiffness changes due to environmental changes and the shape change increases, and at the same time, the dispersion state of the conductive fine particles also changes, resulting in a large variation in electrical resistance value.

  The Young's modulus of the conductive multifilament yarn in the present invention was determined by using Shimadzu Autograph DSS-500 according to the method described in JIS-L-1013 after being left for 15 hours in each environment. It is calculated from the initial tensile resistance measured at 25 cm and a pulling speed of 30 cm / min.

The change rate of Young's modulus is calculated by the following equation.
Change rate of Young's modulus (%) = [(Young's modulus at 10 ° C., RH 30% −- 40 ° C., Young's modulus at RH 90%) / 20 ° C., Young's modulus at RH 65%] × 100

  That is, the change rate of the Young's modulus in the present invention is a standard state in an environment of 20 ° C. and RH 65%, and a Young's modulus in a low temperature and low humidity state (under an environment of 10 ° C. and RH 30%) and a high temperature. The difference in Young's modulus in a high-humidity state (under an environment of 40 ° C. and RH 90%) is regarded as the magnitude of change and divided by the Young's modulus in the standard state.

  Furthermore, the conductive multifilament yarn of the present invention preferably has a variation (standard deviation) in logarithmic value of the electrical resistance value in the yarn length direction of the multifilament yarn of 0.3 or less.

  As for the electrical resistance value in the yarn length direction of the multifilament, the electrical resistance value is measured after being left in an environment of 20 ° C. and RH 65% for 15 hours in the same manner as described above. At this time, the electric resistance value is measured at 500 points in the yarn length direction of the multifilament, each measurement data is logarithmically converted, and the standard deviation is calculated by setting the n number to 500. When the standard deviation exceeds 0.3, the variation in the electric resistance value in the yarn length direction becomes large, and when it is made into a product such as a brush, it becomes difficult to make a product having a uniform electric resistance value. It tends to be inferior in static elimination performance.

  Further, the cross-sectional shape of each single fiber constituting the conductive multifilament yarn of the present invention is not particularly limited, and not only a round cross-sectional shape but also a square or triangular polygonal shape or a hollow shape. Good.

  And the electroconductive multifilament yarn of this invention can be obtained with the following manufacturing methods. First, in a conventionally known method, the above-described conductive fine particles such as carbon black or the master chip containing conductive fine particles at a high concentration and nylon 12 are kneaded and melted with an extruder or the like, extruded from a spinneret, Perform melt spinning. And an unstretched multifilament yarn is obtained, without extending | stretching substantially.

  As a method of kneading and melting the conductive fine particles and nylon 12, the conductive fine particles can be directly kneaded using, for example, a biaxial extruder, but a master chip containing a high concentration of conductive fine particles in advance is used. It is preferable to knead after preparation because it enables more uniform kneading.

  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 200 ° C. to 260 ° C. since the melting point of nylon 12 used is 180 ° C. When the spinning temperature is high, the nylon 12 is thermally decomposed, and smooth spinning becomes difficult and the physical properties of the filament obtained are inferior. On the other hand, if the spinning temperature is too low, undissolved materials remain, and uniform kneading cannot be performed.

  The spun filament is cooled and solidified by cooling air, and then wound once at 500 to 1500 m / min without substantially stretching. Then, the unstretched multifilament yarn is subjected to heat stretching at a temperature of 50 to 160 ° C. under a heating condition of 0.02 seconds or more and a stretching tension of 1.0 g / dtex or less.

  Usually, conductive fine particles once uniformly distributed and chained in the undrawn yarn are subjected to stretching tension at the time of drawing, whereby the chain state of the conductive fine particles becomes fluid. At this time, if it is less than 0.02 seconds, the amount of heat due to the heat stretching treatment is insufficient, uniform stretching is not performed, and the hot water shrinkage of the multifilament is increased. On the other hand, when the stretching tension exceeds 1.0 g / dtex, uniform stretching is not performed, and the chain state of the conductive fine particles becomes non-uniform, resulting in variation in conductive performance.

  By setting the heat treatment time during drawing to 0.02 seconds or more, a sufficient amount of heat can be applied so that uniform drawing is performed in the yarn length direction. Further, even when the stretching tension is 1.0 g / dtex or less, the film is slowly and uniformly stretched.

  The heat treatment time during stretching is 0.02 seconds or more, more preferably 0.05 seconds or more, and the stretching tension is 1.0 g / dtex or less, more preferably 0.8 g / dtex or less. The stretching speed is preferably 500 m / min or less in order to make the heat treatment time 0.02 seconds or more.

  The stretching tension refers to a value obtained by dividing the tension applied during stretching by the final fineness (for example, 220 dtex in Example 1).

  In addition, stretching is usually performed between rollers. When stretching between heating rollers, the roller temperature is set to 70 to 160 ° C, and when stretching is performed by providing a heater between the rollers, the temperature of the heater is set to 70 to 160 ° C. It is preferable to do.

  The heat treatment time during stretching refers to the total time for passing through the heating zone in the above temperature range during stretching. That is, when preheating is performed, the passage time including the preheating zone is set.

  If the temperature during stretching is less than 70 ° C. or the time is less than 0.02 seconds, stretching cannot be performed with a sufficient amount of heat, and uniform stretching becomes difficult. On the other hand, when the temperature at the time of drawing exceeds 160 ° C., the undrawn multifilament yarn is melted and roller winding or the like occurs.

  At the time of hot drawing, the draw ratio is not particularly limited, but in order to give practical strength and elongation to the conductive multifilament yarn, the draw ratio is set to the maximum draw ratio (undrawn multifilament yarn is cut by drawing). The magnification is preferably 40 to 80%.

  Next, it is preferable to perform relaxation heat treatment after heat stretching or continuously after 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 a relaxation heat treatment, the fibers are contracted to form a dense chain state. Thereby, while being able to obtain uniform conductivity, the hot water shrinkage rate of the multifilament yarn can be reduced.

  Usually, since the heat treatment after stretching is performed in a tension state between the rollers, the hot water shrinkage rate of the fiber is lowered, but the effect of making the conductive fine particles in a dense chain state as described above is very 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 g / dtex or less. When the tension during the heat treatment exceeds 0.5 g / dtex, the fiber is subjected to tension heat treatment and the hot water shrinkage of the fiber is lowered, but the conductive fine particles cannot be brought into a dense chain state. The tension during the heat treatment is 0.5 g / dtex, preferably 0.2 g / dtex or less, and the heat treatment time is preferably 0.5 seconds or more, more preferably 1.0 seconds or more.

  The relaxation heat treatment temperature is preferably 70 to 160 ° C, and more preferably 100 to 150 ° C. If the relaxation heat treatment temperature is less than 70 ° C. or the relaxation heat treatment time is less than 0.5 seconds, the fiber cannot be sufficiently thermally contracted, so that the effect of bringing the conductive fine particles into a dense chain state becomes poor. On the other hand, if the relaxation heat treatment temperature exceeds 160 ° C., heat fusion may occur, which is not preferable.

Next, the present invention will be specifically described with reference to examples.
The variation of the hot water shrinkage rate, electrical resistance value, logarithmic value of electrical resistance value, Young's modulus, change rate of Young's modulus, logarithmic value of electrical resistance value in the yarn length direction of the conductive multifilament yarn in the examples is It is measured by the above method.

Example 1
Master chip (35% by mass of carbon black is contained in a nylon 12 chip having a relative viscosity of 1.05 (96% sulfuric acid as a solvent, measured at a concentration of 1 g / dl, measured at a temperature of 25 ° C.) at a carbon black concentration of 25% by mass. Nylon 12 chips (relative viscosity 1.45)) are blended and then fed into an extruder type melt extruder, melted at a spinning temperature of 220 ° C., and discharged from a spinneret having 96 spinning holes with a diameter of 0.20 mm. The undrawn yarn was wound at a take-up speed of 800 m / min. Next, the obtained undrawn yarn is supplied to a drawing and relaxation heat treatment machine, and is heated to 60% of the maximum drawing ratio through a hot plate at 140 ° C. (drawing temperature) so as to satisfy the heat drawing and relaxation heat treatment conditions shown in Table 1. Then, relaxation heat treatment was performed with a saddle heater at 140 ° C. (relaxation heat treatment temperature) to obtain a 220 dtex / 96 f multifilament yarn.

Examples 2-3 and Comparative Examples 2-4
Spinning, stretching, and relaxation heat treatment were performed in the same manner as in Example 1 except that the carbon black content, heat stretching, and relaxation heat treatment conditions were changed as shown in Table 1, and multifilament yarns were obtained.

Example 4
Using a spinneret having 48 spinning holes having a hole diameter of 0.35 mm, the undrawn yarn was wound at a take-up speed of 800 m / min, and the obtained undrawn yarn was supplied to the same drawing and relaxation heat treatment machine as in Example 1. A multifilament yarn of 330 dtex / 48f was obtained in the same manner as in Example 1 except that the conditions were changed so as to satisfy the heat drawing / heat relaxation treatment conditions shown in Table 1.

Examples 5-6
Spinning, stretching, and thermal relaxation treatment were performed in the same manner as in Example 4 except that the content of carbon black and the thermal stretching and relaxation heat treatment conditions were changed as shown in Table 1 to obtain a multifilament yarn.

Comparative Example 1
A multifilament yarn was obtained in the same manner as in Example 1 except that nylon 6 having a relative viscosity of 2.5 was used instead of nylon 12 to perform spinning, drawing, and relaxation heat treatment.

  Table 1 shows the characteristic values and evaluation results of the multifilament yarns obtained in Examples 1 to 6 and Comparative Examples 1 to 4.

  As is clear from Table 1, the conductive multifilament yarns obtained in Examples 1 to 6 have a small hot water shrinkage rate, and each environment of 10 ° C., RH 30%, 20 ° C., RH 65%, 40 ° C., and RH 90%. The amount of change in the logarithmic value of the electrical resistance value below is 0.3 or less, the rate of change in Young's modulus is 30% or less, and the standard deviation of the logarithmic value of the electrical resistance value in the yarn length direction is also small. Even when used for a long period of time under conditions with a large change in humidity, stable electrical resistance and form stability were exhibited.

  On the other hand, since the multifilament yarn of Comparative Example 1 uses nylon 6, the change amount of the logarithmic value of the electrical resistance value and the change rate of the Young's modulus were large. Further, the multifilament yarn of Comparative Example 2 had a large hot water shrinkage because the drawing and relaxation heat treatment time was short, and the multifilament yarn of Comparative Example 3 had too much tension during the drawing and relaxation heat treatment. , The uniform stretching is not performed, the chain state of the conductive fine particles becomes non-uniform, and the multifilament yarn of Comparative Example 4 has a short hot and slack heat treatment time and the tension is too large, so the hot water shrinkage rate is large, The chain state of the conductive fine particles became non-uniform, and each multifilament yarn had a large amount of change in the logarithmic value of the electric resistance value, and the standard deviation of the logarithmic value of the electric resistance value in the yarn length direction was also large.

Claims (2)

A conductive multifilament yarn composed of a single fiber made of nylon 12 containing conductive fine particles, having a hot water shrinkage of 10% or less, 10 ° C, RH30%, 20 ° C, RH65%, 40 ° C, A conductive multifilament yarn characterized in that a change amount of a logarithmic value of an electric resistance value in each environment of RH 90% is 0.3 or less and a change rate of Young's modulus is 30% or less. The conductive multifilament yarn according to claim 1, wherein the variation of the logarithmic value of the electric resistance value in the yarn length direction of the multifilament yarn has a standard deviation of 0.3 or less.