JP2004011047A - Electrically conductive multifilament yarn and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide electrically conductive multifilament yarns exhibiting electrical resistance stable to temperature/humidity changes during the heat treatment step and the like during their production and/or during long-term use, slight in the variation of the electrical resistances of the respective single filaments comprised of the yarns, and affording stable and high-quality printed images when used as a brush for contact electrification or the like. <P>SOLUTION: The electrically conductive multifilament yarns comprise the single filaments as conjugate fibers with an electrically conductive microparticle-containing thermoplastic polymer as one component. The multifilament yarns is ≤30% in the rate of change in the logarithmic value of electrical resistance before and after subjected to hot water treatment, and the variation of the logarithmic values of the electrical resistance of the single filaments is ≤1.0 as standard deviation. <P>COPYRIGHT: (C)2004,JPO

Description

【００８２】
表１から明らかなように、実施例１〜８で得られた導電糸は、単繊維間の電気抵抗値の対数値の標準偏差も１．０以下であり、また熱水処理前後の電気抵抗値の対数値の変化率が小さく、熱水収縮率も小さいものであったので、長期間の使用においても安定した電気抵抗値を示し、これらの導電糸からなるブラシは、温湿度変化が大きい条件下で長期間使用しても画像が良好であった。
一方、比較例１〜４の繊維は、熱延伸条件及び弛緩熱処理条件が最適でなかったため、単繊維間の電気抵抗値の対数値の標準偏差も１．０を超え、また熱水処理前後の電気抵抗値の対数値の変化率が大きく、熱水収縮率も大きいものであったので、温湿度変化を受けるうちに電気抵抗値が低下するものとなり、これらの繊維からなるブラシは画像評価に劣るものであった。
【００８３】
実施例９〜１１
芯成分として、相対粘度２．５０（９６％硫酸を溶媒として，濃度１ｇ／ｄｌ，温度２５℃で測定）のナイロン６チップにカーボンブラック含有量が３０質量％となるようにマスターチップ（カーホ゛ンフ゛ラック３５質量％含有するナイロン６（相対粘度１．９５）チッフ゜）をブレンドしたものを用い、鞘成分には相対粘度２．５０（９６％硫酸を溶媒として，濃度１ｇ／ｄｌ，温度２５℃で測定）のナイロン６チップを用いて、表１に示した芯部と鞘部の質量比にて、エクストルーダー型溶融押出機に供給し、紡糸温度２５５℃で溶融し、孔径０．３５ｍｍの紡糸孔を４８個有する特開平１０−３３１０２５号記載の複合紡糸口金より吐出させて、捲取速度６００ｍ／分で未延伸糸を巻取った。次いで得られた未延伸糸を図１に示した熱延伸・弛緩熱処理機に供給し、表１の熱延伸・弛緩熱処理条件となるように、１５０℃のホットプレートを介して、最大延伸倍率の６０％で延伸し、次いで１７０℃のサドルヒーターにて弛緩熱処理を行い３３０ｄｔｅｘ／４８ｆのナイロン導電糸を得た。
【００８４】
【表２】

【００８５】
表２から明らかなように、実施例９〜１１で得られた導電糸は、単繊維間の電気抵抗値の対数値の標準偏差が１．０以下であり、また熱水処理前後の電気抵抗値の対数値の変化率が小さく、熱水収縮率も小さいものであったので、長期間の使用においても安定した電気抵抗値を示し、これらの導電糸からなるブラシは、温湿度変化が大きい条件下で長期間使用しても画像が良好であった。また、繊維表面に導電性粒子が存在しないため、繊維表面に凹凸がなく、感光ドラムとの接触をミクロレベルで均一化することができ、鮮明な画像を得ることができた。そして、印加電圧５Ｖ／ｃｍ程度の低電圧下においても好適な電気抵抗値を示した。
【００８６】
実施例１２
芯成分として、相対粘度２．５０（９６質量％硫酸を溶媒として、濃度１ｇ／ｄｌ、温度２５℃で測定）のナイロン６チップにカーボンブラック濃度が３０質量％となるようにマスターチップ〔カーボンブラック３５質量％を含有するナイロン６（相対粘度１．９５）チップ〕をブレンドしたものを用い、鞘成分には相対粘度１．３４〔フェノール／テトラクロロエタン＝１／１（質量比）混合溶液に濃度０．５ｇ／ｄｌ、温度２０℃で測定〕のポリエチレンテレフタレート（ＰＥＴ）を用いた。
これらを芯部／鞘部の質量比９５／５にて、エクストルーダー型溶融押出機に供給し、紡糸温度２９５℃で溶融し、孔径０．３５ｍｍの紡糸孔を４８個有する特開平１０−３３１０２５号記載の複合紡糸口金より吐出させて、捲取速度１０００ｍ／分で未延伸糸を巻取った。次いで得られた未延伸糸を延伸機に供給し、表面温度３０℃のローラと１５０℃のホットプレートを介して、最大延伸倍率の６０％（延伸倍率２．４倍）で延伸後、１７０℃のサドル型ヒーターにて弛緩熱処理を行い、２２０ｄｔｅｘ／４８ｆのナイロン導電糸を得た。
次に、得られた導電糸をパイル密度を１０００本／２．５４ｃｍ、パイル長７ｍｍ、生地幅１５ｍｍのパイルテープとして製織した後、直径６ｍｍの円筒面に螺旋状に巻き付けてブラシを作成した。その後、飽和蒸気で５分間起毛の熱処理をした。
【００８７】
実施例１３、比較例５〜６
芯部及び鞘部のポリマー種を表３に示すように変更した以外は、実施例１２と同様にして、紡糸・延伸・弛緩熱処理を行い、導電糸を得た。なお、表中、芯部に用いた共重合ナイロン６／６６は、ナイロン６成分にナイロン６６成分を１５モル％共重合した相対粘度２．９０の共重合ナイロン６／６６チップにカーボンブラック濃度が３０質量％となるようにマスターチップをブレンドしたものを用い、ＰＢＴは相対粘度１．３４〔フェノール／テトラクロロエタン＝１／１（質量比）混合溶液に濃度０．５ｇ／ｄｌ、温度２０℃で測定〕のポリブチレンテレフタレートにカーボンブラック濃度が３０質量％となるようにマスターチップをブレンドしたものを用い、鞘部のポリマーは芯部に用いられているポリマー（ナイロン６又共重合ナイロン６／６６又はＰＥＴ）でカーボンブラックを添加していないものを示す。
【００８８】
実施例１２〜１３、比較例５〜６で得られた導電糸の物性値及びブラシの特性値及び画像評価の結果を表３に示す。
【００８９】
【表３】

【００９０】
表３から明らかなように、実施例１２〜１３で得られた導電糸は、単繊維間の電気抵抗値の対数値の標準偏差が１．０以下であり、また熱水処理前後の電気抵抗値の対数値の変化率が小さく、熱水収縮率も小さいものであったので、長期間の使用においても安定した電気抵抗値を示し、これらの導電糸からなるブラシは、温湿度変化が大きい条件下で長期間使用しても画像が良好であった。また、繊維端面の形状において、芯部が存在せず、端面より内側に芯部が存在しており、さらに繊維表面に凹凸がないため、感光ドラムとの接触をミクロレベルで均一化することができ、鮮明な画像を得ることができた。そして、印加電圧５Ｖ／ｃｍ程度の低電圧下においても好適な電気抵抗値を示した。
一方、比較例５〜６の繊維は、熱延伸条件及び弛緩熱処理条件が最適でなかったため、単繊維間の電気抵抗値の対数値の標準偏差も１．０を超え、また、熱水処理前後の電気抵抗値の対数値の変化率が大きく、熱水収縮率も大きいものであったので、温湿度変化を受けるうちに電気抵抗値が低下するものとなり、さらには端面に芯部が存在することにより、これらの繊維からなるブラシは画像評価に劣るものであった。
【００９１】
【発明の効果】
本発明の導電マルチフィラメント糸は、温湿度変化を繰り返し受けても安定した電気抵抗値を示し、かつ、マルチフィラメント糸を構成する各単繊維の電気抵抗値のばらつきも少ないので、接触帯電用等のブラシとして用いると、安定、かつ良好な画像を得ることが可能である。そして、各種電子写真装置用ブラシに好適に使用することができる。
本発明の導電マルチフィラメント糸の製造方法によれば、上記のような導電マルチフィラメント糸を効率よく生産することが可能である。
【図面の簡単な説明】
【図１】一般的なポリエチレンテレフタレート導電糸をブラシとして使用したときの時間と電気抵抗値の関係を示すグラフである。
【図２】一般的なナイロン６導電糸をブラシとして使用したときの時間と電気抵抗値の関係を示すグラフである。
【図３】本発明の導電マルチフィラメント糸の製造方法の一実施態様を示す概略工程図である。
【図４】本発明の導電マルチフィラメント糸を構成する単繊維の沸水処理後の端面形状の一実施態様を示す模式図である。
【図５】本発明の導電マルチフィラメント糸を構成する単繊維の沸水処理後の端面形状の一実施態様を示すＳＥＭ写真である。
【図６】本発明の導電マルチフィラメント糸を構成する単繊維の一実施態様を示す断面図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a conductive multifilament yarn suitable for a developing brush, a contact charging brush, a cleaner brush, or a static elimination brush used in an electrophotographic apparatus (copier, facsimile, printer, etc.).
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an electrophotographic apparatus such as an electrophotographic copying machine, a non-contact type corona charging method has been adopted as an electrostatic latent image method formed on a photosensitive drum. However, in the corona charging method, it is considered that ozone generated from corona discharge deteriorates parts of the electrophotographic apparatus. This ozone is harmful to the human body. Furthermore, a high voltage must be used for corona discharge, and there is a risk of fire and the like.
[0003]
In order to solve this problem, a contact charging system using a low voltage without using corona discharge has been proposed in recent years. For example, a contact charging system using a conductive multifilament yarn as a contact charging brush has been proposed.
[0004]
Conventionally, cellulosic fibers are often used as conductive multifilament yarns. Further, among polyester and polyamide fibers widely used as synthetic fibers, many fibers containing conductive fine particles have been proposed.
[0005]
JP-A-57-6762 and JP-A-7-102437 disclose titanium oxide comprising two types of thermoplastic polymers (polyester and polyamide) having different melting points and having a conductive coating on the low melting point side. Conductive conjugate fibers have been proposed in which conductivity is improved by heat-treating the contained conjugate fiber at a temperature between both melting points. However, these conductive fibers have improved conductivity, but have a high hot water shrinkage of about 20%. Therefore, the conductive fibers are not suitable for use in a heat treatment step for producing a contact charging brush or a contact charging brush. And the resulting variation in electrical resistance caused these conductive yarns to be unsuitable for contact charging brushes.
[0006]
Japanese Patent Publication No. 1-29887 proposes a conductive cellulosic fiber in which a hydrophobic functional group is introduced into a cellulosic conductive yarn so that a stable electric resistance value can be exhibited with respect to a change in humidity.
[0007]
Japanese Patent Application Laid-Open No. 9-49116 discloses that two or more kinds of conductive fine particles are added to a fiber to reduce the variation in specific resistance by 10%. ³ Conductive cellulosic fibers reduced to within Ω · cm have been proposed.
[0008]
The two cellulosic fibers also did not sufficiently improve the stability to humidity and the variation in electric resistance. That is, since the contact charging brush or the like is processed or used in an environment in which the temperature and humidity change greatly, the change in the fiber morphology caused by the temperature and humidity change in the environment causes a change in the chain state of the conductive fine particles and the electric resistance. Appears as a change in value. Therefore, even if it has a suitable electric resistance value at the beginning of production, these values decrease during a heat treatment step or the like for a long time when a contact charging brush is produced, and the difference from the value at the beginning of production. However, it has not been possible to solve the disadvantage that the image quality becomes large and an image failure occurs.
[0009]
Furthermore, it has been found that, generally, in a conductive yarn made of a thermoplastic polymer such as polyamide or polyester, the electric resistance value varies for each single fiber constituting the multifilament. Then, it was found that such a variation in the electric resistance value for each single fiber was also a cause of difficulty in forming a uniform electrostatic latent image. That is, when the conductive yarn comes into contact with the photosensitive drum or the like, the contact is at a single fiber level, and therefore, since there is little variation in the electric resistance value between each single fiber, it is possible to further reduce the spots for energization and static elimination. It was found that a clearer image could be obtained.
However, a conductive multifilament yarn having a small variation in electric resistance value for each single fiber has not yet been proposed.
[0010]
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems, and shows a stable electric resistance value with respect to temperature and humidity changes in a heat treatment step or the like for a long time when a brush is made. An object of the present invention is to provide a conductive multifilament yarn which has a small variation in electric resistance value of a single fiber and can provide a stable and good image when used as a brush for contact charging or the like. .
[0011]
[Means for Solving the Problems]
The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have reached the present invention.
That is, the present invention provides the following (1) and (2).
(1) A conductive multifilament yarn composed of a single fiber which is a conjugate fiber containing a thermoplastic polymer containing conductive fine particles as a component, and a logarithmic value of an electric resistance value of the multifilament yarn before and after a hot water treatment. The conductive multifilament yarn characterized in that the rate of change of the filament is 30% or less, and the standard deviation of the logarithmic value of the electric resistance of the single fiber constituting the multifilament is 1.0 or less.
(2) Composite melt spinning using a thermoplastic polymer containing conductive fine particles to obtain an undrawn multifilament yarn, and then heating the undrawn multifilament yarn at a temperature of 50 to 200 ° C for 0.02 seconds or more. Under the following conditions, a hot stretching treatment is performed at a stretching tension of 1.0 g / dtex or less, and then a relaxation heat treatment is performed at a temperature of 70 to 200 ° C. at a tension of 0.5 g / dtex or less for 0.5 seconds or more. A method for producing a conductive multifilament yarn according to (1).
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
First, the brush for an electrophotographic apparatus according to the present invention refers to various brushes used for an electrophotographic apparatus such as a copying machine, a facsimile, and 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. Although the present specification mainly describes a contact charging brush, the conductive multifilament yarn of the present invention can be suitably used even when applied to the other brushes described above.
[0013]
The polymer forming the multifilament yarn of the present invention is not particularly limited as long as it is a fiber-forming thermoplastic polymer, and examples thereof include polyester, polyamide, polyethylene, and polypropylene. Among them, polyester and polyamide are preferable.
[0014]
More specifically, polyesters include, for example, polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, and those obtained by copolymerizing a dicarboxylic acid component, a diol component, or an oxycarboxylic acid component, or those obtained by blending the polyesters. Can be Further, aliphatic polyesters such as polylactic acid, polybutylene succinate, and polyε-caprolactam known as biodegradable polyesters may be used.
[0015]
Examples of the polyamide include nylon 6, nylon 66, nylon 69, nylon 46, nylon 610, nylon 12, polymeta-xylene adipamide, and copolymers or blends of these components.
[0016]
Each single fiber constituting the multifilament yarn of the present invention is a conjugate fiber containing a polymer containing conductive fine particles as one component. Examples of the conductive fine particles include, for example, carbon black, metal powder, and metal oxide. Among them, carbon black is preferable. The amount to be added is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, for polyester, for example, based on the total mass of the fiber. In the case of polyamide, the content is preferably 15 to 45% by mass, more preferably 20 to 35% by mass.
[0017]
In general, a conductive yarn made of polyamide or polyester adsorbs moisture of about 0.4 to 5% depending on environmental humidity. Therefore, 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. In a humidity region of about 70% or less, the dispersion state of the conductive fine particles is a main factor. .
[0018]
In addition, the dispersion state of the conductive fine particles also changes as the form of the fiber changes. That is, a change in fiber morphology caused by a heat treatment step at the time of making the brush or a change in temperature and humidity in the use environment causes a change in the dispersion state of the conductive fine particles and a change in the electric resistance value. This is because the release of residual strain based on the deformation received during spinning or drawing and the morphological change (thermal shrinkage difference) that the oriented molecules try to return to the minimum energy state are caused by the heat treatment process at the time of preparation and the temperature and humidity change of the use environment. Probably provoked.
[0019]
In general, a charging brush or a cleaner brush is formed by weaving conductive yarn as a pile and then spirally winding it around a cylindrical surface to form a brush. In order to prepare the pile, heat setting by hot water treatment is performed. Further, when used in a copying machine or the like as described above, the use environment is severe and the temperature and humidity change greatly.
[0020]
The hot water shrinkage of a conductive yarn spun 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 of the fiber before the brush is stabilized, the fiber shrinks during use or at the stage of heat setting, and the form is reduced. The change changes the state of dispersion of the conductive fine particles. The change in the dispersion state of the conductive fine particles causes a variation in the electric resistance value.
[0021]
This will be further described with reference to FIGS.
The graph of FIG. 1 shows a conventional general polyethylene terephthalate conductive yarn having an electric resistance of 10%. ^9.4 Ω polyethylene terephthalate conductive yarn was used as a fiber constituting a contact charging brush for an electronic copying machine, and the electrical resistance value of the constituting fiber was measured every hour until 48 hours after the use of the brush.
First, the electric resistance value is 10 ^9.4 Suppose that a polyester conductive yarn of Ω is used as a brush. During use of this brush, the electrical resistance of each of the fibers constituting the brush decreases, and before use, the electrical resistance of all the constituent fibers decreases by 10%. ^9.4 Changed from Ω to 10 ^9.0 , 10 ^8.8 , 10 ^8.6 It can be seen that the fiber has a plurality of electric resistance values approaching Ω.
[0022]
The graph in FIG. 2 shows a conventional general polyamide conductive yarn having an electric resistance of 10%. ^8.4 An electrical resistance value was measured by using a Ω nylon 6 conductive yarn as a contact charging brush for an electronic copying machine in the same manner as the polyester fiber of FIG.
First, the electric resistance value is 10 ^8.4 It is assumed that a Ω nylon 6 conductive yarn is used as a brush. During use of this brush, the electrical resistance of each of the fibers constituting the brush decreases, and before use, the electrical resistance of all the constituent fibers decreases by 10%. ^8.4 Changed from Ω to 10 ^8.0 , 10 ^7.8 , 10 ^7.6 It can be seen that the fiber has a plurality of electric resistance values approaching Ω.
[0023]
Such a phenomenon is a factor that causes an image failure. That is, when the polyester or polyamide-based conductive yarn obtained by spinning in a normal method, the stage of heat setting the brush, or subjected to wet heat treatment during use, from the electrical resistance value before the brush descend. Moreover, even if the fibers have the same electric resistance value before being made into a brush, there is a variation in the degree of reduction between the fibers, and the brush is made of fibers having different electric resistance values after use.
[0024]
From the graphs of FIGS. 1 and 2, the electric resistance of a general polyester or polyamide-based conductive yarn greatly decreases for a while after the start of use, and the width of the decrease in the electric resistance over time has increased. It turns out that it becomes small and is stabilized.
[0025]
Therefore, the conductive multifilament yarn of the present invention has the effect of reducing the change in electric resistance value due to the hot water treatment, and hardly causing an image failure even when used for a long time. Further, the variation in the electric resistance value of each single fiber constituting the multifilament is reduced, whereby a uniform electrostatic latent image can be formed.
[0026]
First, the rate of change of the logarithmic value of the electric resistance value of the multifilament yarn before and after the hot water treatment needs to be 30% or less. When the value of the expression (1) exceeds 30%, a change in the electric resistance value due to the hot water treatment is large, which causes an image failure.
When the electric resistance value before the hot water treatment is Rb and the electric resistance value after the hot water treatment is Ra,
[(LogRb−logRa) / logRb] × 100 (1)
Is 30% or less. In particular, the value of the formula (1) (= change rate) is preferably 20% or less, more preferably 10% or less, and most preferably 5% or less.
[0027]
The hot water treatment according to the present invention is performed according to JIS-L-1042 hot water immersion method, after immersing the obtained conductive multifilament yarn in hot water of 80 ° C. for 30 minutes and then dehydrating with a centrifugal dehydrator. What is dried (105 ° C).
[0028]
The electric resistance is measured as follows. From the yarn subjected to the hot water treatment and the yarn not subjected to the hot water treatment, 20 test pieces each having a length of 10 cm are taken every 100 m along the length direction. A voltage of 500 V is applied between the 10 cm test pieces (between both ends), and using a resistance value measuring instrument “SM-10E” manufactured by Toa Denpa Kogyo Co., Ltd. under the measurement environment of 20 ° C. and 20% RH. The electric resistance Rb before the hot water treatment and the electric resistance Ra (Ω / cm) after the hot water treatment are measured. In addition, it is set as the average value of 20 sample pieces.
[0029]
Next, in the conductive multifilament yarn of the present invention, it is necessary that the variation of the logarithmic value of the electric resistance value of the single fiber constituting the multifilament is not more than 1.0 standard deviation. That is, when the conductive yarn comes into contact with the photosensitive drum or the like, the contact is at a single fiber level, and therefore, since there is little variation in the electric resistance value between each single fiber, it is possible to further reduce the spots for energization and static elimination. And a clearer image can be obtained.
[0030]
In addition, the electric resistance value of each single fiber constituting the multifilament is measured in accordance with the above-described method for measuring the electric resistance value, and the standard deviation is calculated by using the number n as the number of single yarns constituting the multifilament.
[0031]
If the standard deviation exceeds 1.0, the difference in electric resistance between the single fibers becomes too large, and it is difficult to form a uniform electrostatic latent image. The standard deviation is further preferably 0.8 or less, more preferably 0.5 or less.
[0032]
Further, the hot water shrinkage of the conductive multifilament yarn is preferably 10% or less. Generally, the hot water shrinkage of the conductive multifilament yarn satisfying the expression (1) is often 10% or less, but when the hot water shrinkage exceeds 10%, heat is applied to the conductive multifilament yarn. When the shape of the single fiber changes, the dispersion state of the conductive fine particles changes, and the variation of the electric resistance value between the single fibers increases, and the standard deviation is set to 1.0 or less. To be difficult.
[0033]
The hot water shrinkage rate was set to a sample length of 100 cm, immersed in hot water of 80 ° C. for 30 minutes according to JIS-L-1042 hot water immersion method, dehydrated by a centrifugal dehydrator, and then dried (105 ° C), the sample length L (cm) at that time is measured, and calculated by the following equation.
Hot water shrinkage (%) = [(100−L) / 100] × 100
[0034]
Next, the shape of each single fiber constituting the conductive multifilament yarn of the present invention will be described. The single fiber constituting the multifilament yarn is a conjugate fiber containing a thermoplastic polymer containing conductive fine particles as one component. As the shape of the conjugate fiber, a core-sheath type conjugate fiber is preferable.
[0035]
First, it is preferable that only the sheath contains conductive fine particles and the core does not contain conductive fine particles. By using such a core-sheath conjugate fiber, the strength can be improved by the core containing no conductive fine particles. Specifically, the strength is preferably at least 1.0 cN / dtex, more preferably at least 1.5 cN / dtex, more preferably at least 2.0 cN / dtex. In addition, since the conductive fine particles need only be contained in the sheath portion, the cost can be reduced as compared with the case where the conductive fine particles are contained in the whole fiber.
[0036]
In order to prevent peeling of the core and the sheath and increase the strength, it is preferable that the polymer of the core and the sheath is the same. Although the conductive fine particles are contained only in the sheath as described above, the conductive performance can be sufficiently maintained because the conductive fine particles are present on the fiber surface.
[0037]
Furthermore, in order to maintain such strength and conductive performance, the core / sheath ratio is preferably 1/9 to 9/1, more preferably 3/7 to 9/1 in terms of mass ratio. If the ratio of the core is too small, it is difficult to obtain a fiber having high strength. On the other hand, if the ratio of the sheath portion is too small, when used as a contact charging brush for a long time, in each fiber constituting the brush, the sheath portion is liable to wear and the core portion is likely to be exposed. The fiber becomes only the core portion, and has no conductive property, so that an image trouble occurs.
[0038]
Next, the monofilament constituting the conductive multifilament yarn of the present invention is preferably a core-sheath type conjugate fiber in which conductive fine particles are contained only in the core.
By using such a conjugate fiber, since there is substantially no conductive fine particles on the fiber surface, there is no minute unevenness on the fiber surface, the surface has high smoothness, and the contact with the photosensitive drum or the like is uniform at a micro level. And a clear image can be obtained. Furthermore, a suitable electric resistance value can be exhibited even under a low voltage of about 5 V / cm.
[0039]
The thickness of the sheath is measured as follows. Twenty test pieces each having a length of 10 cm are collected at intervals of 100 m along the length direction of the conductive multifilament yarn, one single fiber is extracted from each test piece, and the cross section thereof is observed with an optical microscope. Four points are selected at equal distances (intervals) along the outer periphery of the cross-sectional shape, and the thickness of the sheath at that point is measured. The average value of these four points is defined as the value of one test piece, and the average value of 20 test pieces is defined as the thickness of the sheath in the present invention.
[0040]
The thickness of the sheath is preferably controlled to a thickness that does not reduce the conductivity of the core, and the thickness of the sheath not containing conductive fine particles is preferably 1 μm or less, more preferably 0 μm. 0.6 μm or less, and more preferably 0.4 μm or less. The core / sheath ratio of the core and the sheath is preferably 80/20 to 99.9 / 0.1, more preferably 90/10 to 99.5 / 0.5, by mass ratio. If the ratio of the sheath is larger than this, it is difficult to reduce the thickness of the sheath to 1 μm or less.
[0041]
Further, it is preferable that the electric resistance value is uniform at any position on the fiber surface, and for this purpose, it is preferable to make the distance between the core and the sheath (the thickness of the sheath) uniform. Among the core-sheath conjugate fibers, it is preferable that both the fiber cross section and the core portion cross section are circular and concentric core-sheath conjugate fibers.
[0042]
Further, the single fiber constituting the conductive multifilament yarn of the present invention is a core-sheath type conjugate fiber containing conductive fine particles in the core as described above, and in the shape of the fiber end face after the boiling water treatment, the core is Is preferred, and a core part is present inside the end face.
[0043]
With such a conjugate fiber, in the shape of the fiber end surface, there is no core containing conductive fine particles, and only the sheath contacts the photosensitive drum or the like. Can be made uniform at a micro level, and uniform charging can be performed. As a result, a clear image can be obtained, and a suitable electric resistance value can be exhibited even under a low voltage of about 5 V / cm.
[0044]
In order to form such a shape, it is preferable to use polymers having different hot water shrinkage rates for the core polymer and the sheath polymer, and to make the core polymer a highly shrinkable polymer. As a result, in the spinning, drawing, and heat treatment steps, residual strain due to the difference in heat shrinkage occurs. For this reason, it can be assumed that, by further performing a heat treatment on the obtained fiber, the residual strain is released, the core is largely shrunk, and a portion where the core does not exist on the fiber end face is generated.
[0045]
Therefore, as the combination of the core and sheath polymer components, polyamide (for example, nylon 6) is used for the core polymer, polyester (for example, polyethylene terephthalate, polylactic acid) is used for the sheath polymer, or polyamide is used for both core and sheath polymers. [For example, it is preferable to use nylon 6 for the core polymer and nylon 12 for the sheath polymer, use copolymer nylon (nylon 6/66) for the core polymer, and use nylon 6 for the sheath polymer].
[0046]
This will be described with reference to FIG. That is, in the shape of the fiber end surface after the boiling water treatment, the core portion 11 does not exist and the core portion 11 exists inside the end surface 13, which is particularly effective in charging effect. It can be performed uniformly. Although the detailed mechanism for this is not clear, in the case of a normal core-sheath composite fiber, the charging performance differs between the core and the sheath, and the portion where the core containing the conductive fine particles comes into contact, and the conductive fine particles In a portion where the sheath portion that does not contain the same contacts, the charging and discharging states of the photosensitive drum and the like are different, and the charging and discharging states are non-uniform. On the other hand, in the conductive yarn of the present invention, since the core does not exist on the end face, only the sheath contacts the photosensitive drum or the like. Since the core is covered with the sheath also on the fiber surface, there is no portion where the core is exposed to the outside, and all the portions that come into contact with the photosensitive drum or the like become the sheath. Thereby, uniform charging becomes possible, and a clear image can be obtained.
[0047]
The conductive multifilament yarn of the present invention is such that the single fiber is a core-sheath type conjugate fiber, the core contains only conductive fine particles, and the core portion does not exist in the shape of the fiber end surface after the boiling water treatment. As long as the core portion is present further inside, the portion 14 where the core portion of the fiber end surface does not exist, that is, the portion of only the sheath portion 12 is 0.1 mm along the fiber longitudinal direction inside the fiber end surface. It is preferably from 5 to 5 μm, more preferably from 0.2 to 3 μm, even more preferably from 0.3 to 2 μm. If the length of the portion 14 where the core of the fiber end surface does not exist is less than 0.1 μm, the core may come into contact with the photosensitive drum or the like, and it is difficult to obtain the above-described uniform charging effect. On the other hand, when the thickness exceeds 5 μm, the number of the sheath portions having no conductive property increases, and the conductive property and the static elimination performance are deteriorated.
[0048]
Here, the conductive multifilament yarn of the present invention defines the shape of the end face after the boiling water treatment. Here, the boiling water treatment means that a test piece (10 cm in length) is immersed in hot water at 100 ° C. for 5 minutes. The end face shape after the boiling water treatment is obtained by observing the both end faces of the test piece after the boiling water treatment by air drying with a SEM (scanning electron microscope) photograph. The length of the portion of the fiber end face where the core does not exist is obtained by taking out the single yarn constituting each test piece, measuring the length in the yarn length direction of the portion where the core does not exist on both end faces, and measuring the length of the test piece. The average value of 20 (40 measured values measured at both end faces) shall be taken.
FIG. 5 shows an SEM photograph showing the end face shape of the single fiber of the conductive multifilament yarn of the present invention after the boiling water treatment.
[0049]
The conductive multifilament yarn of the present invention refers to a fiber having a core inside the end face in the shape of the fiber end face after the above-mentioned boiling water treatment (immersion in hot water at 100 ° C. for 5 minutes). As long as the core portion is located further inside, in the shape before the boiling water treatment, the core portion may be present on the fiber end surface. Further, even if the core portion exists inside the end face from before the boiling water treatment, if the core part exists inside the end face in the shape of the end face after the boiling water treatment, the conductive yarn is defined by the present invention.
When the conductive multifilament yarn of the present invention is used as various brushes, it is woven as a pile tape and heat-treated after raising the brush (usually, for 5 to 10 minutes with saturated steam). In many cases, a shape in which a core is present inside is developed.
[0050]
Then, the thickness of the sheath portion that does not contain conductive fine particles is preferably 1 μm or less, more preferably 0.6 μm or less, in order to make the thickness of the sheath portion not to reduce the conductivity of the core portion. More preferably, it is 0.4 μm or less.
The core / sheath ratio of the core and the sheath is preferably 80/20 to 99.9 / 0.1, more preferably 90/10 to 99.5 / 0.5, by mass ratio. If the ratio of the sheath is larger than this, it is difficult to reduce the thickness of the sheath to 1 μm or less.
[0051]
And it is preferable that the electric resistance value is uniform at any position on the fiber surface. For this purpose, it is preferable to make the distance between the core and the sheath (the thickness of the sheath) uniform. Among the core-sheath composite fibers, it is preferable that both the fiber cross section and the core section are circular and concentric core-sheath composite fibers.
[0052]
Further, in the shape of the single fiber constituting the conductive multifilament yarn of the present invention, a conjugate fiber other than the core-sheath conjugate fiber may be used, and the component A containing conductive fine particles and the component B not containing A shape in which the component A is divided into a plurality of regions and continuously exists in the longitudinal direction of the fiber surface, and the component B occupies the region including the center of the fiber cross section and continuously exists in the longitudinal direction. (Shown in FIGS. 6A and 6B).
[0053]
In this case, the distance L on the fiber cross section between the adjacent divided components A is preferably 5 μm or less. The distance L on the fiber cross section between adjacent divided components A is more preferably 4 μm or less, and still more preferably 3 μm or less. The content of the conductive fine particles in the component A is preferably 18% by mass or more, more preferably 23% by mass or more.
[0054]
By using such a conjugate fiber, since there are a plurality of components containing conductive fine particles at a high concentration on the fiber surface, the conductive performance can be sufficiently increased, and the distance between the components is short. The electric resistance value of the fiber surface does not become non-uniform, and a good image without image disturbance can be obtained. Further, the amount of the conductive fine particles may be smaller than that in which the entire fiber contains the conductive fine particles, and the cost can be reduced.
[0055]
In the conductive multifilament yarn of the present invention, it is preferable that the logarithmic value of the electric resistance value in the yarn length direction of the multifilament is not more than a standard deviation of 0.3 or less, and the fineness of a single fiber is not more than 10 dtex.
[0056]
First, the electric resistance value of the multifilament in the yarn length direction is measured in the same manner as described above. At this time, the electric resistance value is measured at 500 points in the yarn direction of the multifilament, and each measurement is performed. The data is logarithmically converted, and the standard deviation is calculated by setting the number n to 500.
If the standard deviation exceeds 0.3, the variation in the electric resistance value in the yarn length direction becomes large, and it becomes difficult to produce a contact charging brush or the like having stable quality.
[0057]
Further, the fineness of the single fiber constituting the multifilament is preferably 10 dtex or less, more preferably 8 dtex or less, and more preferably 5 dtex or less. That is, the smaller the single fiber fineness, the denser and uniform the contact state with the photosensitive drum and the like, whereby the charging and the like can be performed more uniformly, and a stable and good electrostatic latent image can be obtained. If the single-fiber fineness exceeds 10 dtex, this effect is hard to be obtained, and a clear image is hard to be obtained, and streak-like stains are liable to be generated on a copy as the number of times of copying increases.
[0058]
The conductive multifilament yarn of the present invention has an electric resistance value of 10 in an atmosphere at a temperature and humidity of 20 ° C. and 20% RH. ⁴ -10 ¹¹ It is preferably Ω / cm. By setting the electric resistance value in this range, a fiber more suitable for various brushes used in an electrophotographic apparatus can be obtained. In particular, the electric resistance value in an atmosphere at a temperature and humidity of 20 ° C. and 20% RH is 10 ⁷ -10 ¹⁰ When it is Ω / cm, it can be a fiber suitable for a contact charging brush. Here, in the case of a contact charging brush, the electric resistance value is particularly 10 ¹¹ If it exceeds Ω / cm, it is difficult to obtain a uniform charge on the surface of the photosensitive belt drum. ⁴ In the case of a low resistance value of less than Ω / cm, when a defect such as a pinhole is present in the photosensitive band layer, a large current flows into the photosensitive band layer, and poor charging is likely to occur.
[0059]
The conductive multifilament yarn having the above characteristics can be obtained by the following manufacturing method. That is, after performing composite melt-spinning using a thermoplastic polymer containing conductive fine particles to obtain an undrawn multifilament yarn, (1) the undrawn multifilament yarn is heated at a temperature of 50 to 200 ° C for 0.02 seconds or more. Under a heating condition, a hot stretching treatment is performed at a stretching tension of 1.0 g / dtex or less. (2) Then, at a temperature of 70 to 200 ° C., a relaxation of 0.5 seconds or more at a tension of 0.5 g / dtex or less. Heat treatment is performed.
[0060]
First, by a conventionally known method, a master chip and a thermoplastic polymer containing conductive fine particles or conductive fine particles such as carbon black as described above are kneaded and melted by, for example, an extruder, extruded from a spinneret, and melt-spun. Do. Then, an undrawn multifilament yarn is obtained without being substantially drawn.
[0061]
At this time, as a method of kneading and melting the conductive fine particles and the thermoplastic polymer, the conductive fine particles can be directly kneaded using, for example, a biaxial extruder, but once the conductive fine particles are contained in a high concentration. It is preferable to mix and knead after preparing a master chip, since more uniform kneading can be performed.
[0062]
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 resin used. If the spinning temperature is too high, the thermoplastic polymer undergoes thermal decomposition, making smooth spinning difficult and resulting in poor filament properties. On the other hand, if the spinning temperature is too low, undissolved substances and the like remain, so that uniform kneading cannot be performed.
[0063]
The spun filament is cooled by cooling air at 0 to 100 ° C, preferably 15 to 40 ° C. If the cooling temperature is too low, it becomes difficult to control the temperature and workability. If the cooling temperature is too high, the cooling will be insufficient and the quality of the finally obtained filament will be inferior. Next, the cooled and solidified filament is once wound at 500 to 1500 m / min without being substantially stretched.
[0064]
Next, the undrawn multifilament yarn is subjected to heat drawing under the condition (1).
As described in JP-A-2000-160427, for example, when the addition rate of the conductive carbon particles in the conductive cellulosic fiber is sequentially increased from 0% by mass, the conductivity of the cellulosic fiber is increased around a certain increase rate. A phenomenon occurs in which the properties are rapidly improved (the specific resistance value is rapidly reduced). This is considered to be because when the concentration reaches a specific concentration, the distribution and chain state of the conductive carbon particles become good, and this greatly affects the conductivity. In this example, the relationship between the concentration of the conductive carbon particles and the specific resistance value is considered. However, the present inventors have found that the distribution and chain state of the conductive fine particles are greatly affected by the stretching / relaxation heat treatment conditions. It has been found that the variation in the conductive performance of the filament and the variation in the electric resistance value between each single fiber are affected.
[0065]
That is, if the conductive fine particles are densely and uniformly chained in each single fiber, there is no variation in the electric resistance value between each single fiber, and it is estimated that the conductivity of the multifilament is greatly improved. Is done.
[0066]
Normally, the conductive fine particles once distributed and chained uniformly in the undrawn yarn become fluid during the drawing due to the drawing tension. At this time, if the amount of heat is insufficient due to the short-time thermal stretching treatment, or if the stretching tension is high and uniform stretching is not performed, the chain state of the conductive fine particles becomes uneven. That is, since the degree of stretching varies between the single fibers constituting the multifilament, the chain state of the conductive fine particles becomes different for each single fiber constituting the multifilament, and the electric resistance value of each single fiber becomes different. Are different from each other.
Therefore, in the present invention, the electric conductivity is set so that the electric resistance value of each single fiber becomes equal and the change rate of the logarithmic value of the electric resistance value of the multifilament yarn before and after the hot water treatment becomes 30% or less. Specific heat stretching and relaxation heat treatment are performed so as to form a chain state of the conductive fine particles.
[0067]
First, it is necessary to perform hot stretching at a temperature of 50 to 200 ° C., a time of 0.02 seconds or more, and a stretching tension of 1.0 g / dtex or less. By setting the heat treatment time at the time of drawing to 0.02 seconds or more, a sufficient amount of heat can be given so that each single fiber is drawn equally. By setting the drawing tension to 1.0 g / dtex or less, each single fiber is slowly and uniformly drawn. The heat treatment time at the time of stretching needs to be 0.02 seconds or more, but is more preferably 0.05 seconds or more, and preferably 0.07 seconds or more. The stretching tension needs to be 1.0 g / dtex or less, but is more preferably 0.8 g / dtex or less, and is preferably 0.6 g / dtex or less.
The stretching speed is not particularly limited, but is preferably 500 m / min or less, more preferably 200 m / min or less, more preferably 100 m / min or less, in order to set the heat treatment time to 0.02 seconds or more. It is. However, it is preferably 50 m / min or more in consideration of productivity.
Here, the stretching tension is a value obtained by dividing the tension applied at the time of stretching by the final fineness (for example, 330 dtex in Example 1).
[0068]
Regarding the stretching temperature, the stretching is usually performed between the rollers. When the stretching is performed between the heating rollers, the roller temperature is set to 50 to 200 ° C., and when the stretching is performed by providing the heater between the rollers (FIG. 3). The temperature of the heater is set to 50 to 200 ° C. However, in these cases, when preheating is performed, it is preferable to preheat at a temperature of less than 100 ° C, and then to raise the temperature of the heating stretching roller or heater to 100 to 200 ° C, more preferably 120 to 170 ° C. It is preferable to stretch as follows.
In addition, the said heat processing time means the total of the time which passes through the heating zone of the said temperature range at the time of extending | stretching. That is, when performing preheating, the passage time includes the preheating zone.
If the temperature at the time of stretching is less than 50 ° 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 200 ° C., the undrawn multifilament yarn is melted, and winding with a roller or the like occurs.
[0069]
In the hot stretching process, the stretching ratio may be arbitrary. However, in order to give practical strength and elongation to the conductive multifilament yarn, the stretching ratio is set to the maximum stretching ratio (when the undrawn multifilament yarn is (The magnification at which the film is cut by stretching)). If the draw ratio is less than 50% of the maximum draw ratio, the elongation remains too high, and it tends to be difficult to obtain a conductive multifilament yarn having practical high elongation. If the draw ratio exceeds 80% of the maximum draw ratio, a conductive multifilament yarn having a uniform fineness in the yarn length direction may not be easily obtained.
[0070]
The heat stretching process is specifically performed as shown in FIG. FIG. 3 is a schematic process diagram showing one embodiment of the method for producing a conductive multifilament yarn of the present invention. First, the undrawn multifilament yarn 1 is drawn by the pulling roller 5 through the guide roller 2. Then, heat is given by a box-shaped heater 4 provided below the guide roller 2. The temperature of the box-shaped heater 4 is 50 to 200 ° C., and the time during which heat is applied is 0.02 seconds or more. The stretching is performed between the guide roller 2 and the tension roller 5. Further, a plurality of heating rollers may be used in place of the box-shaped heater 4 to perform a heat stretching process between the heating rollers. Also in this case, the temperature is set to 50 to 200 ° C., and the time during which heat is applied is 0.02 seconds or more. The tension (drawing tension) applied to the undrawn multifilament yarn during drawing is set to 1.0 g / dtex or less.
[0071]
Next, it is necessary to perform a relaxation heat treatment under the condition (2) after the thermal 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 are in a state in which the dense chain state has been relaxed are subjected to a specific temperature and time under a specific low tension. By performing the relaxation heat treatment, the single fiber is shrunk to form a dense chain again. Thereby, while improving conductivity, the dispersion | variation in the electric resistance value between single fibers can be reduced further. Further, it is possible to obtain thermal stability such that the change rate of the logarithmic value of the electric resistance value of the multifilament yarn before and after the hot water treatment is 30% or less.
[0072]
Normally, the heat treatment after drawing is performed in a tension state between the rollers, so that the thermal shrinkage of the fiber is reduced, but the effect of closely chaining the conductive fine particles again as described above is very poor.
[0073]
Therefore, in the present invention, it is necessary to perform a relaxation heat treatment at a tension of 0.5 g / dtex or less for 0.5 seconds or more. If the tension during the heat treatment exceeds 0.5 g / dtex, the yarn is subjected to a tension heat treatment, and the heat shrinkage of the fiber is reduced, but the conductive fine particles cannot be brought into a dense chain state again. The tension during the heat treatment needs to be 0.5 g / dtex or less, preferably 0.2 g / dtex or less, more preferably 0.1 g / dtex or less.
[0074]
If the relaxation heat treatment time is less than 0.5 seconds, the fibers cannot be sufficiently thermally shrunk, so that the effect of bringing the conductive fine particles into a dense chain state again is poor, and the electric resistance between the single fibers is reduced. The effect of reducing the variation in the value is also reduced. In addition, thermal stability cannot be imparted.
The relaxation heat treatment time requires 0.5 seconds or more, preferably 1 second or more, and more preferably 2 seconds or more.
[0075]
The relaxation heat treatment temperature is 70 to 200 ° C, preferably 100 to 190 ° C, more preferably 140 to 180 ° C. If the relaxation heat treatment temperature is lower than 70 ° C., the fibers cannot be sufficiently thermally shrunk, so that the relaxation heat treatment becomes insufficient and the above-described effects cannot be obtained. On the other hand, when the relaxation heat treatment temperature exceeds 200 ° C., heat fusion may occur, which is not preferable.
[0076]
Such relaxation heat treatment may be performed using the heat treatment device 6 (device having the saddle type heater 8 and the heating roller 9) shown in FIG. The multifilament yarn that has passed through the heat treatment device 6 is wound up by the traveler 7 to obtain a conductive multifilament yarn.
[0077]
【Example】
Next, the present invention will be specifically described with reference to examples.
Hot water shrinkage of the conductive multifilament yarn in the examples, electric resistance, change rate of logarithmic value of electric resistance, variation in electric resistance value in the yarn length direction, standard deviation of logarithmic value of electric resistance value of single fiber Is measured by the method described above.
The image evaluation was performed as follows. The obtained fiber was woven as a pile tape having a pile density of 1000 fibers / 2.54 cm, a pile length of 7 mm, and a cloth width of 15 mm, and was spirally wound around a cylindrical surface having a diameter of 6 mm to form a brush. Then, the hair was heat-treated with saturated steam for 5 minutes. After leaving this brush in an atmosphere of 25 ° C. and 20% RH for 1 hour, it is left in an atmosphere of 80 ° C. and 60% RH for 30 minutes. This is repeated five times as one processing. This process was performed once, performed twice, performed three times, performed four times, performed five times. Each brush was attached to a laser printer as a charging brush, and 1000 brushes each were used. And the sharpness of the image was evaluated on a scale of 5 as 5 being the most excellent.
The irregularities on the fiber surface were measured and evaluated as follows. The surface of the obtained conductive yarn was photographed by a SEM (scanning electron microscope) photograph, and the smoothness of the surface state was visually evaluated in the following three stages.
：: smooth △: slightly smooth ×: uneven and not smooth
Further, the measurement of the electric resistance value at an applied voltage of 5 V / cm was performed as follows. The conductive multifilament yarn of the present invention is sampled along the length direction in 20 test pieces each having a length of 10 cm every 100 m. A voltage of 50 V is applied between the 10 cm test pieces (between both ends), and using a resistance value measuring instrument “SM-10E” manufactured by Toa Denpa Kogyo Co., Ltd. under the measurement environment of 20 ° C. and 20% RH. The electric resistance (Ω / cm) at an applied voltage of 5 V / cm is measured. In addition, it is set as the average value of 20 sample pieces.
[0078]
Example 1
A nylon 6 chip having a relative viscosity of 3.50 (measured at a concentration of 1 g / dl and a temperature of 25 ° C. using 96% sulfuric acid as a solvent) is used as a core component, and a relative viscosity of 2.50 (using 96% sulfuric acid as a solvent and a concentration of 1 g / dl) is used. dl, measured at a temperature of 25 ° C.) blended with a master chip (a nylon 6 (relative viscosity 1.95) chip containing 35% by mass of carbon black) so that the carbon black content becomes 23% by mass. Is supplied to an extruder-type melt extruder as a sheath component, melted at a spinning temperature of 280 ° C., and a spinneret having 48 spinning holes with a hole diameter of 0.35 mm as a core-sheath composite ratio of 5/5 (mass ratio). The undrawn yarn was wound up at a winding speed of 600 m / min.
Next, the obtained undrawn yarn is supplied to the hot drawing / relaxation heat treatment machine shown in FIG. 3, and the hot draw / relaxation heat treatment conditions shown in Table 1 are applied via a hot plate at 150 ° C. to obtain the maximum draw ratio. The film was stretched at 60% and then subjected to relaxation heat treatment with a 170 ° C. saddle heater to obtain a 330 dtex / 48f nylon conductive yarn.
[0079]
Examples 2 to 8, Comparative Examples 1 to 4
Except that the addition amount of carbon black, the core-sheath ratio, and the heat stretching / relaxation heat treatment conditions were changed as shown in Table 1, and only Examples 5 to 8 used a spinneret having 96 spinning holes with a hole diameter of 0.20 mm. In the same manner as in Example 1, spinning, stretching and relaxation heat treatment were performed to obtain a conductive yarn, and a brush was prepared.
[0080]
Table 1 shows the characteristic values of the conductive yarns and brushes obtained in Examples 1 to 8 and Comparative Examples 1 to 4 and the results of image evaluation.
[0081]
[Table 1]

[0082]
As is clear from Table 1, the conductive yarns obtained in Examples 1 to 8 also had a standard deviation of the logarithmic value of the electric resistance between the single fibers of 1.0 or less, and the electric resistance before and after the hot water treatment. Since the rate of change of the logarithm of the value was small and the hot water shrinkage rate was also small, it showed a stable electric resistance value even during long-term use, and the brush made of these conductive yarns has a large change in temperature and humidity. The image was good even after long-term use under the conditions.
On the other hand, for the fibers of Comparative Examples 1 to 4, the standard deviation of the logarithmic value of the electric resistance value between the single fibers also exceeded 1.0 because the hot drawing conditions and the relaxation heat treatment conditions were not optimal, and before and after the hot water treatment. Since the rate of change of the logarithmic value of the electrical resistance value was large and the hot water shrinkage ratio was also large, the electrical resistance value decreased while undergoing changes in temperature and humidity, and brushes made of these fibers were used for image evaluation. It was inferior.
[0083]
Examples 9 to 11
As a core component, a nylon 6 chip having a relative viscosity of 2.50 (measured at a temperature of 25 ° C. with a concentration of 1 g / dl using 96% sulfuric acid as a solvent) was mixed with a master chip (Carbon Black) so that the carbon black content was 30% by mass. A blend of 35% by mass of nylon 6 (relative viscosity 1.95) was used, and the sheath component was measured at a relative viscosity of 2.50 (concentration of 1 g / dl using 96% sulfuric acid as a solvent at a temperature of 25 ° C.). ) Was supplied to an extruder-type melt extruder at a mass ratio of the core portion and the sheath portion shown in Table 1 at a mass ratio shown in Table 1, and melted at a spinning temperature of 255 ° C. to form a spinning hole having a hole diameter of 0.35 mm. The undrawn yarn was wound at a winding speed of 600 m / min by discharging from a composite spinneret described in Japanese Patent Application Laid-Open No. H10-331025 having 48 pieces. Next, the obtained undrawn yarn is supplied to the hot drawing / relaxation heat treatment machine shown in FIG. 1, and the hot draw / relaxation heat treatment conditions shown in Table 1 are applied via a hot plate at 150 ° C. The film was stretched at 60% and then subjected to relaxation heat treatment with a 170 ° C. saddle heater to obtain a 330 dtex / 48f nylon conductive yarn.
[0084]
[Table 2]

[0085]
As is clear from Table 2, the conductive yarns obtained in Examples 9 to 11 had a standard deviation of the logarithmic value of the electric resistance value between the single fibers of 1.0 or less, and the electric resistance before and after the hot water treatment. Since the rate of change of the logarithm of the value was small and the hot water shrinkage rate was also small, it showed a stable electric resistance value even for long-term use, and the brush made of these conductive yarns has a large change in temperature and humidity. The image was good even after long-term use under the conditions. Further, since there were no conductive particles on the fiber surface, there was no unevenness on the fiber surface, the contact with the photosensitive drum could be made uniform at a micro level, and a clear image could be obtained. And, it showed a suitable electric resistance value even under a low voltage of about 5 V / cm.
[0086]
Example 12
As a core component, a master chip [carbon black] was prepared so that a nylon 6 chip having a relative viscosity of 2.50 (measured at a temperature of 25 ° C. at a concentration of 1 g / dl using 96 mass% sulfuric acid as a solvent) had a carbon black concentration of 30 mass%. Nylon 6 (relative viscosity: 1.95) chips containing 35% by mass] are blended. The sheath component has a relative viscosity of 1.34 [phenol / tetrachloroethane = 1/1 (mass ratio) mixed solution. 0.5 g / dl, measured at a temperature of 20 ° C.] polyethylene terephthalate (PET).
These are supplied to an extruder-type melt extruder at a core / sheath mass ratio of 95/5, melted at a spinning temperature of 295 ° C., and have 48 spinning holes with a hole diameter of 0.35 mm. The undrawn yarn was discharged from the composite spinneret described in No. 1 and wound at a winding speed of 1000 m / min. Next, the obtained undrawn yarn is supplied to a drawing machine, drawn at 60% of the maximum drawing ratio (drawing ratio 2.4 times) through a roller having a surface temperature of 30 ° C and a hot plate having a surface temperature of 150 ° C. Was subjected to relaxation heat treatment with a saddle-type heater to obtain a 220 dtex / 48f nylon conductive yarn.
Next, the obtained conductive yarn was woven as a pile tape having a pile density of 1000 yarns / 2.54 cm, a pile length of 7 mm, and a cloth width of 15 mm, and was spirally wound around a cylindrical surface having a diameter of 6 mm to form a brush. Then, the hair was heat-treated with saturated steam for 5 minutes.
[0087]
Example 13 and Comparative Examples 5 to 6
A spinning, stretching and relaxation heat treatment was performed in the same manner as in Example 12 except that the polymer type of the core and the sheath was changed as shown in Table 3, to obtain a conductive yarn. In the table, the copolymer nylon 6/66 used for the core portion was prepared by copolymerizing nylon 66 component with nylon 6 component at 15 mol%. A master chip was blended so as to have a concentration of 30% by mass, and PBT had a relative viscosity of 1.34 [phenol / tetrachloroethane = 1/1 (mass ratio) mixed solution at a concentration of 0.5 g / dl and a temperature of 20 ° C. Measurement], using a master chip blended with polybutylene terephthalate so as to have a carbon black concentration of 30% by mass. The polymer in the sheath was the polymer used in the core (nylon 6 or copolymerized nylon 6/66). Or PET) without carbon black.
[0088]
Table 3 shows physical property values, brush characteristic values, and image evaluation results of the conductive yarns obtained in Examples 12 to 13 and Comparative Examples 5 to 6.
[0089]
[Table 3]

[0090]
As is clear from Table 3, the conductive yarns obtained in Examples 12 and 13 had a standard deviation of the logarithmic value of the electric resistance between the single fibers of 1.0 or less, and the electric resistance before and after the hot water treatment. Since the rate of change of the logarithm of the value was small and the hot water shrinkage rate was also small, it showed a stable electric resistance value even for long-term use, and the brush made of these conductive yarns has a large change in temperature and humidity. The image was good even after long-term use under the conditions. In addition, in the shape of the fiber end surface, there is no core portion, the core portion exists inside the end surface, and there is no irregularity on the fiber surface, so that contact with the photosensitive drum can be made uniform at a micro level. And a clear image could be obtained. And, it showed a suitable electric resistance value even under a low voltage of about 5 V / cm.
On the other hand, in the fibers of Comparative Examples 5 to 6, the standard deviation of the logarithmic value of the electric resistance value between the single fibers exceeded 1.0 because the hot drawing conditions and the relaxation heat treatment conditions were not optimal, and the fibers before and after the hot water treatment. Since the rate of change of the logarithmic value of the electrical resistance value was large and the hot water shrinkage rate was also large, the electrical resistance value decreased while undergoing temperature and humidity changes, and there was a core on the end face As a result, brushes made of these fibers were inferior in image evaluation.
[0091]
【The invention's effect】
The conductive multifilament yarn of the present invention exhibits a stable electric resistance value even when repeatedly subjected to changes in temperature and humidity, and has a small variation in electric resistance value of each single fiber constituting the multifilament yarn. When used as a brush, it is possible to obtain a stable and good image. And it can be suitably used for brushes for various electrophotographic devices.
According to the method for producing a conductive multifilament yarn of the present invention, it is possible to efficiently produce the above conductive multifilament yarn.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between time and electric resistance when a general polyethylene terephthalate conductive yarn is used as a brush.
FIG. 2 is a graph showing the relationship between time and electric resistance when a general nylon 6 conductive yarn is used as a brush.
FIG. 3 is a schematic process diagram showing one embodiment of a method for producing a conductive multifilament yarn of the present invention.
FIG. 4 is a schematic view showing one embodiment of an end face shape of a single fiber constituting a conductive multifilament yarn of the present invention after a boiling water treatment.
FIG. 5 is a SEM photograph showing one embodiment of the end face shape of the single fiber constituting the conductive multifilament yarn of the present invention after the boiling water treatment.
FIG. 6 is a cross-sectional view showing one embodiment of a single fiber constituting the conductive multifilament yarn of the present invention.

Claims (9)

A conductive multifilament yarn composed of a single fiber that is a composite fiber containing a thermoplastic polymer containing conductive fine particles as a component, and a rate of change of a logarithmic value of an electric resistance value of the multifilament yarn before and after hot water treatment. Is 30% or less, and the standard deviation of the logarithmic value of the electric resistance value of the single fiber constituting the multifilament is 1.0 or less. The conductive multifilament yarn according to claim 1, wherein the hot water shrinkage of the multifilament is 10% or less. The conductive multifilament yarn according to claim 1 or 2, wherein the logarithmic value of the electric resistance value in the yarn length direction of the multifilament has a standard deviation of 0.3 or less. The conductive multifilament yarn according to any one of claims 1 to 3, wherein the single fiber is a core-sheath composite fiber, and only the sheath contains conductive fine particles. The conductive multifilament yarn according to any one of claims 1 to 3, wherein the single fiber is a core-sheath type conjugate fiber, and only the core contains conductive fine particles. The single fiber is a core-sheath type composite fiber, and the core contains conductive fine particles only.In the shape of the fiber end face after the boiling water treatment, the core does not exist and the core exists inside the end face. The conductive multifilament yarn according to claim 1, wherein The conductive multifilament yarn according to any one of claims 1 to 6, wherein the fineness of the single fiber is 10 dtex or less. The conductive multifilament yarn according to any one of claims 1 to 7, wherein the electric resistance value in an atmosphere at a temperature and humidity of 20 ° C and 20% RH is 10 ⁷ to 10 ¹⁰ Ω / cm. After performing composite melt spinning using a thermoplastic polymer containing conductive fine particles and obtaining an undrawn multifilament yarn, the undrawn multifilament yarn is heated to a temperature of 50 to 200 ° C. under a heating condition of 0.02 seconds or more, A hot stretching treatment is performed at a stretching tension of 1.0 g / dtex or less, and a relaxation heat treatment is performed at a temperature of 70 to 200 ° C. at a tension of 0.5 g / dtex or less for 0.5 seconds or more. A method for producing a conductive multifilament yarn according to claim 1.

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