JP2021055214A - Core-sheath type composite fiber - Google Patents

Abstract

To provide a core-sheath type composite fiber suitable for an electrical conduction brush for an electro-photographic apparatus which requires precision printing.SOLUTION: A core-sheath type composite fiber comprises a fiber formative polymer as a core component and a fiber formative polymer involving 20-30 wt.% of a carbon black as a sheath component, wherein the core-sheath type composite fiber is characterized by that the sheath component covers a fiber surface completely, a core-sheath conjugate ratio is 85/15-70/30, and its composite form satisfies any of (a) and (b); (a) 0.05<(Lmax-Lave)/R<0.20; (b) a rate of L satisfying (L-Lave)/R>0.05 is 10-20%.SELECTED DRAWING: Figure 1

Description

The present invention relates to a core-sheath type composite fiber. More specifically, the present invention relates to a core-sheath type composite fiber suitable for a conductive brush for an electrophotographic apparatus.

Conductive fibers are used in clothing applications as textiles for clean rooms and mixed fibers for carpets, and as fibers used for the purpose of removing static electricity and applying electric charges in parts incorporated in electrophotographic equipment. Not limited to industrial use, it is used in a wide range of fields.

In particular, in industrial applications, electrophotographic devices include a lubricant application brush that applies a lubricant to a photoconductor, a charging brush that charges the photoconductor, a toner supply brush that supplies toner to the photoconductor, and a toner that remains on the photoconductor. Various brushes such as cleaning brushes are used. Charging and toner supply to these photosensitive member, such as removal of the residual toner is electrostatically force is important, as the conductive fiber for the conductive brush, conductive specific resistance is 10 ² ~10 ¹² Ω · cm Sex fibers are commonly used. As such conductive fibers, conductive fibers in which conductive fine particles such as carbon black are contained to impart conductivity are generally used. For example, spinning with a conductive component as a sheath component and containing conductive fine particles. In order to compensate for the deterioration of properties and mechanical properties, some core-sheath composite fibers have been proposed in which a non-conductive component containing no conductive fine particles is used as a core component and the fiber surface is coated with a conductive component.

Patent Document 1 proposes conductive fibers having excellent high-order passability by reducing the variation in cross-section formation even when the conductive layer forms a concentric circular type cross section that completely covers the fiber surface. ing. Further, Patent Document 2 proposes a conductive fiber having latent crimp by forming an eccentric core sheath / side-by-side cross section. Further, Patent Document 3 proposes a conductive fiber having improved conductive performance and higher-order passability by forming a cross section in which a protruding conductive component is arranged on the fiber surface.

International Publication No. 2001/021867 Pamphlet (Claim 1) JP-A-2009-046785 (Claim 1) JP-A-2007-119975 (Claim 1)

However, with the evolution of electrophotographic apparatus, delicate images are required, and the required characteristics of conductive brushes for electrophotographic photography for conductive variations are becoming stricter year by year, and the same is true for fibers.

When the conductive fiber of Patent Document 1 is used for a conductive brush, it becomes difficult to form a stable conductive path in the concentric type, the resistivity in the longitudinal direction of the fiber is not stable, and the conductive variation of the brush increases. I can't get a delicate image.

Since the conductive fiber of Patent Document 2 expresses crimp, when the fiber is used for a conductive brush, the contact between the fiber and the photoconductor is not stable, the conductive variation of the brush increases, and a fine image is obtained. I can't get it.

Since the non-conductive layer occupies most of the fiber surface in the conductive fiber of Patent Document 3, there is a problem that the resistivity in the longitudinal direction of the fiber is not stable, the conductive variation of the brush increases, and a fine image cannot be obtained. It was.

In order to solve the above problems, the present invention provides a core-sheath type composite fiber having conductivity, small variation in conductivity in the longitudinal direction of the fiber, and a flat form, and is suitable for a conductive brush for an electrophotographic apparatus. It provides a mold composite fiber.

In the present invention for solving the above problems, the core-sheath type composite fiber of the present invention has the following constitution.
(1) The core component is a fiber-forming polymer, the sheath component is a fiber-forming polymer containing 10 to 50% by weight of carbon black, and the sheath component completely covers the fiber surface, and the core-sheath composite ratio (weight). A core-sheath type composite fiber having a ratio of 85/15 to 70/30, wherein the composite form satisfies the following conditions (a) and (b).
(A) 0.05 <(Lmax-Lave) / R <0.20
(B) The ratio of L such that (L-Lave) / R> 0.05 is 10 to 20%.
・ R is the radius of the inscribed circle on the surface layer of the sheath component ・ L = R−r
r is the distance from the center point of the inscribed circle of the sheath component surface layer to the boundary of the core sheath component when the inscribed circle of the sheath component surface layer is divided into 32 in the circumferential direction. The maximum value when the tangent circle is divided into 32 in the circumferential direction ・ Love is the average value when the inscribed circle on the surface layer of the sheath component is divided into 32 in the circumferential direction (2) The fiber-forming polymer is polyester. (1) The core-sheath type composite fiber according to the above.
(3) The core-sheath type composite fiber according to the previous item (1), wherein the fiber-forming polymer of the sheath component is polytrimethylene terephthalate.

The core-sheath type composite fiber of the present invention has conductivity, has a small conductivity variation in the fiber longitudinal direction, and has a flat shape, and is therefore suitable for a conductive brush for an electrophotographic apparatus that requires precise printing. It becomes a material.

Schematic cross-sectional view of a fiber showing an example of an embodiment of the present invention Schematic cross-sectional view of a fiber showing an example of an embodiment of a comparative example Schematic cross-sectional view of the fiber obtained in Comparative Example 4 It is a schematic diagram explaining the composite form of the fiber cross section.

Hereinafter, the present invention will be described in detail.

The core-sheath type composite fiber of the present invention is a core-sheath type composite fiber in which a conductive layer made of a fiber-forming polymer containing carbon black as a sheath component completely covers the fiber surface.

The fiber-forming polymer of the present invention is a polymer having known fiber-forming performance, such as polyamide, polyester, or polyolefin. As the polyamide, for example, nylon 6, nylon 66, nylon 610, nylon 12, and a copolymerized polyamide containing these as main components are well known. As polyesters, for example, polyethylene terephthalate, polybutylene terephthalate (hereinafter, PBT), polytrimethylene terephthalate (hereinafter, PPT), polylactic acid, and copolymerized polyesters containing these as main components are well known. Even if it is a polymer other than the above, it can be applied as a fiber-forming polymer forming the present invention as long as it has a fiber-forming performance. It is preferable that the polyester has excellent environmental stability, durability, and fiber forming ability. The core component is preferably a polyester-based polymer that does not contain carbon black, and a conductive fiber that can assist stretch deformation of the polyester containing carbon black as a sheath component, has excellent spinnability, and has excellent mechanical properties. Obtainable. As the polyester, for example, a copolymerized polyester, PBT, or PPT can be preferably used.

The fiber-forming polymer constituting the sheath component (conductive layer) of the present invention includes polyethylene terephthalate, PBT, PPT, polylactic acid, etc., but copolymerization is performed from the viewpoint of suppressing the decrease in fluidity and spinnability due to the inclusion of carbon black. Polyester, PBT and PPT are preferred. As the copolymerization component, for example, a dicarboxylic acid compound, a diol compound, a derivative such as a hydroxycarboxylic acid, an adduct, a structural isomer, an optical isomer, or the like may be used alone without impairing the gist of the present invention. If it is within the range, two or more of them may be used in combination. Of these, polyester containing PPT as a main component is preferable.

The content of carbon black of the present invention is 10 to 50% by weight based on the fibrogenic polymer constituting the sheath component. The core-sheath type composite fiber of the present invention is used in applications that require various conductivity. The carbon black content used for the sheath component (conductive layer) can be arbitrarily changed to adjust the surface resistivity according to the required application, but it is suitable when used for a brush for an electrophotographic apparatus6. In order to obtain conductivity having a low surface resistivity value of about 8 logΩ / cm level, 20 to 30% by weight is preferable.

It is important that the carbon black of the present invention does not impair the physical characteristics of the fiber such as toughness and does not agglomerate the carbon black when it is contained in the fiber-forming polymer. Furness black obtained by the furnace method, Ketjen black obtained by the Ketjen method, and acetylene black made from acetylene gas are preferable. Further, since there is no increase in filter pressure, yarn breakage, or decrease in toughness during spinning, the particle size of carbon black is preferably in the range of 1 to 500 nm, more preferably 5 to 400 nm.

The core-sheath composite ratio (weight ratio) of the core-sheath type composite fiber of the present invention is preferably 85/15 to 70/30 (core / sheath). Most preferably, it is 82/18 to 72/28 (core / sheath), and more preferably 80/20 to 75/25 (core / sheath). By setting the core-sheath composite ratio to 85/15 to 70/30 (core / sheath), the elongation and deformation behavior during spinning is good, the toughness is excellent, and excellent conductivity can be obtained, which is suitable for electrophotographic equipment. It is a raw thread suitable for brush raw thread.

In the core-sheath type composite fiber of the present invention, the sheath component (conductive layer) completely covers the fiber surface, and as illustrated in FIGS. 1 and 2, the thickness of the sheath component is not uniform, and the thickness of a part thereof is not uniform. It is a cross section that is large, that is, has a partial recess in the core component (non-conductive layer). In the case of a concentric type core-sheath type composite fiber in which the conductive layer described in Patent Document 1 completely covers the fiber surface when the fiber surface is not provided, for example, in order to obtain the surface resistivity of the conductive fiber suitable for a brush. Although it is necessary to reduce the thickness, it becomes difficult to form a stable conductive path, the surface resistivity in the fiber longitudinal direction is not stable, and the variation increases. As a result, the conductive variation of the brush increases, and a fine image cannot be obtained. When the conductive layer does not completely cover the fiber surface, for example, in the core-sheath type composite fiber in which the conductive layer described in Patent Document 3 is partially exposed on the fiber surface, the surface resistivity in the fiber longitudinal direction is not stable. If the surface resistivity is not stable, the conductive variation of the brush increases, and a fine image cannot be obtained.

Therefore, as in the present invention, by adopting a configuration in which the thickness of a part of the sheath component (conductive layer) is increased, electricity is stably passed through this part, so that the surface resistivity is stable and variation is suppressed. Will be done. As a result, when used in a brush for an electrophotographic apparatus, the brush has excellent conductivity and uniformity, and a delicate image can be obtained.

In the fiber cross section of the core-sheath type composite fiber of the present invention, the value obtained by subtracting the distance r from the center point of the inscribed circle to the boundary of the core-sheath component from the radius R of the inscribed circle on the surface layer of the sheath component is defined as L. Then, the individual value of L, the maximum value of L (Lmax), and the average value of L (Lave) measured by dividing the inscribed circle into 32 are measured, and the degree of size and the degree of spread of the thickness portion are measured. calculate. In the present invention, by setting the size of the thick portion and the degree of spread within a specific range, as described above, the raw yarn is excellent in conductivity and conductivity uniformity, and is the most suitable yarn for a brush for an electrophotographic apparatus. There may be a plurality of thick portions, but the smaller the number of thick portions, the more the decrease in toughness can be suppressed. Therefore, one thick portion is preferable.

The degree of the size of the thick portion is obtained by dividing the difference between the maximum value of L (Lmax) and the average value of L (Lave) by the radius R of the inscribed circle of the sheath component (conductive layer) surface layer in the fiber cross section (Lmax). It can be indicated by −Lave) / R, and the smaller the value, the smaller the size of the thick portion, and the larger the value, the larger the size of the thick portion. In the present invention, (Lmax-Lave) / R is greater than 0.05 and (Lmax-Lave) / R is less than 0.20. When it is 0.05 or less, the conductive variation increases and the conductive variation of the brush increases, and a delicate image cannot be obtained. If it is 0.20 or more, crimping occurs after brushing, the contact between the fiber and the photoconductor is not stable, the conductive variation of the brush increases, and the printed matter is blurred, so that a fine image cannot be obtained. .. (Lmax-Lave) / R is preferably greater than 0.10 and less than 0.15.

As for the degree of spread of the thickness portion, the difference between the individual value of L and the average value (Lave) of L is divided by the radius R of the inscribed circle on the surface layer of the sheath component (L-Lave) / R is 0.05 or more. It can be indicated by the ratio of L, and the smaller the value, the narrower the spread of the thick portion, and the larger the value, the wider the spread of the thick portion. The method of measuring R and r will be described later in the column of Examples. Further, the concentric type having no thick portion is 0. In the present invention, the proportion of L having (L-Lave) / R of 0.05 or more is 10% or more and 20% or less. When it is less than 10%, the thickness portion spreads less in the cross section of the fiber, it becomes difficult to form a stable conductive path, the conductive variation increases, the conductive variation of the brush increases, and a delicate image cannot be obtained. .. If it is larger than 20%, the eccentricity of the composite form becomes large, crimping occurs after brushing, the contact between the fiber and the photoconductor is not stable, the conductive variation of the brush increases, and the printed matter becomes blurred. I can't get a fine image. The degree of spread of the thick portion is preferably 15% or more and 20% or less.

In the core-sheath type composite fiber of the present invention, the carbon black content and the core-sheath ratio used for the sheath component (conductive layer) can be arbitrarily changed to adjust the surface resistivity according to the required application. The surface resistivity when used in a brush for an electrophotographic apparatus is preferably 6 to 8 logΩ / cm, and more preferably 6 to 7.5 logΩ / cm. By setting the surface resistivity within such a range, it is possible to obtain an excellent printed matter without blurring or stains.

When the core-sheath composite fiber of the present invention is used in a brush for an electrophotographic apparatus, the finer the single-thread fineness, the denser and more uniform the contact state with the photosensitive drum, and a good and stable electrostatic latent image. The single yarn fineness is preferably 10 dtex or less, more preferably 8 dtex or less, but not less than 1 dtex.

The toughness of the core-sheath type composite fiber of the present invention is preferably 18 or more, more preferably 20 or more. As a result, the brush has excellent process passability in high-order processing, and also has excellent durability when used as a brush for an electrophotographic apparatus. The toughness referred to in the present invention is obtained by the method described in the examples.

A conventionally known melt spinning method may be applied as a method for producing a core-sheath type composite fiber of the present invention. For example, it is designed to have the above-mentioned cross-sectional shape by melting a fiber-forming polymer containing carbon black in the sheath component and a fiber-forming polymer not containing carbon black in the core component in separate melt extruders. It is discharged from the composite spinneret, cooled, lubricated and wound once to obtain an undrawn yarn multifilament, which is then stretched so that the residual elongation is 20 to 70%, and further heat-treated on a heat plate. Examples include a method of going and winding.

The core-sheath type composite fiber of the present invention is used in applications requiring various conductivity, for example, from clothing applications to industrial applications such as dustproof clothing, antistatic wear, antistatic carpets, and conductive brushes for electrophotographic devices. It can be used for a wide range of purposes.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. Each characteristic value of the example was measured by the following method.

A. Fineness and single yarn fineness The fibers were squeezed for a length of 100 m, their weight (g) was multiplied by 100, and measurements were performed three times per level, and the average value was taken as the fineness (dtex). Further, the value obtained by dividing the fineness by the number of single yarns constituting the fiber was defined as the single yarn fineness (dtex).

B. Toughness Toughness is calculated from the following formula.
Toughness = strength x (elongation) ^1/2
The strength and elongation were measured according to JIS L1013 (2010, chemical fiber filament yarn test method).

C. Cross-sectional imaging, calculation of composite form condition (b) A block in which a single yarn is embedded in epoxy resin is cut with a microtome in the fiber cross-sectional direction perpendicular to the fiber axis direction to prepare a thin section. It was observed and photographed with transmitted light at a magnification of 3000 times with a KEYENCE microscope (VHX3000). By performing image analysis on the obtained fiber cross-sectional image, the radius R of the inscribed circle on the surface layer of the sheath component in the fiber cross section and the distance r from the center point of the inscribed circle to the boundary portion of the core-sheath component are L. (= R-r) is measured. The fiber cross section was divided into 32 in the circumferential direction, and the individual values of 32 L, the maximum value of L (Lmax), and the average value of L (Lave) were obtained. For each value of L, (L-Lave) / R was calculated, and the number of Ls at which (L-Lave) / R> 0.05 was divided by 32 to obtain the percentage. Cross-section samples at any three locations were measured, and the average percentage was taken.

D. Surface resistivity (logΩ / cm), standard deviation of surface resistivity The fibers were measured after being held in an atmosphere at a temperature of 25 ° C. and a humidity of 60% for 1 hour or longer. A probe consisting of two rod terminals (thickness φ2 mm, distance between rod terminals 20 mm) connected to the Toa DKK insulation resistance tester SM-8220 is installed so that the traveling thread is in contact with the probe, and the applied voltage is 100 V. The resistance value for a length of 4700 mm was measured with a mirror roller at a take-up speed of 70 mm / min and a sampling rate of 0.2 seconds. The value obtained by dividing the average (Ω) of the obtained values by the distance (20 mm) of the threads in contact between the rod terminals was defined as the surface resistivity (Ω / cm), and the standard deviation of the surface resistivity was obtained.

E. Evaluation of the presence or absence of crimps Ten skeins were prepared using a measuring machine with a frame circumference of 1.0 m, and dry heat treatment was performed at 190 ° C. for 15 minutes to evaluate whether or not the treated fibers had crimps. Table 1 shows the yarn properties of the fibers used and the crimp assessment results. The indicators related to crimp are as follows, and ◎ and ○ were evaluated as passing.
⊚: There is no crimp.
◯: There is a mixture of a portion where the crimp is present and a portion where the crimp is not present in the treated yarn.
X: Crimp is present in the entire yarn after treatment.
XX: There is a large crimp on the entire yarn after treatment.

F. Evaluation of Image Quality The obtained fibers were ^{woven into a pile having a density of 60,000 fibers / cm 2} , and a velvet-processed cloth was wound around a bias to obtain a cleaner brush. This was mounted on a dry copier and print evaluation was performed using test chart paper. Table 1 shows the results of the assessment of the yarn properties and image quality of the fibers used. The indicators related to image quality are as follows, and ◎, ○, and △ were evaluated as acceptable.
⊚: The printed matter is clean.
◯: Although the printed matter has 1 to 10 fine streaky stains, it is hardly noticeable.
Δ: Although there are 11 to 20 fine streaky stains on the printed matter, they are not so noticeable.
X: There are 21 or more streaky stains on the printed matter, which are conspicuous.

Example 1
(Adjustment of isophthalic acid copolymerized polyethylene terephthalate (hereinafter referred to as PET / I))
A polycondensation catalyst containing an 85% aqueous solution of phosphoric acid as a color inhibitor in a low weight obtained from 150 parts by weight of terephthalic acid, 16 parts by weight of isophthalic acid and 75 parts by weight of ethylene glycol by a normal esterification reaction. 0.06 part by weight of antimony trioxide and 0.06 part by weight of cobalt acetate tetrahydrate as a colorant were added to carry out a polycondensation reaction, and PET / I pellets having an intrinsic viscosity of IV0.65 and a melting point (Tm) of 222 ° C. Got When this was melt-spun, it was vacuum-dried at 130 ° C. for 24 hours before use.

(PPT manufacturing method and preparation of PPT component with carbon black (CB) added)
130 parts (6.7 mol parts) of dimethyl terephthalate, 114 parts (15 mol parts) of 1,3-propanediol, 0.24 parts (0.014 mol parts) of calcium acetate monohydrate, dihydration of lithium acetate 0.065 parts of trimethyl terephthalate and 0.134 parts of titanium tetrabutoxide were added to a low-weight compound obtained by adding 0.1 parts (0.01 mol parts) of salt and performing a transesterification reaction while distilling off methanol. Part was added, and a polycondensation reaction was carried out while distilling off 1,propanediol to obtain a chip-shaped prepolymer. The obtained prepolymer was further subjected to solid-phase polymerization under a nitrogen stream at 220 ° C. to obtain PPT pellets having an intrinsic viscosity of IV1.15 and a melting point (Tm) of 229 ° C.

After vacuum drying these PPT pellets at 150 ° C. for 10 hours, they are made into powders and granules in a nitrogen atmosphere, and the powders are mixed with furnace black (hereinafter, FCB, average particle size 31 nm), which is a kind of CB, in a nitrogen atmosphere. After mixing, melt-kneading was performed using a twin-screw extruder (shaft length L / shaft diameter D = 45). Here, FCB was kneaded at 280 ° C. after adjusting the FCB to 23.5% by weight in the resin composition of PPT and FCB obtained at the end of kneading. The gut-shaped resin composition discharged after kneading was cooled with tap water at 15 ° C. and then cut with a cutter to obtain pellets of a resin composition of PPT and FCB (hereinafter referred to as PPT-FCB). When this was melt-spun, it was vacuum-dried at 150 ° C. for 10 hours before use.

(Manufacturing of core-sheath type composite fiber)
With an extruder type melt extruder (shaft length L / shaft diameter D = 35), PPT-FCB is separately melted as the sheath component and PET / I is separately melted as the core component, and the spinning temperature is 260 ° C. and the diameter is 0.4 mm. , Threads are discharged from a round hole-shaped mouthpiece with 72 holes, the core-sheath composite ratio (weight ratio) is set to 80/20, and the thickness of the sheath component as shown in FIG. 1 is partially increased. Composite melt spinning was performed with a core-sheath type cross section in which the sheath component covers the entire surface of the fiber. After discharging, the fiber is cooled, an oil agent (effective component 15% by weight concentration) is attached as an effective component to the yarn so that the amount of adhesion is 1.5% by weight, and then the fiber is wound at a take-up speed of 1500 m / min. An undrawn yarn was obtained.

The obtained undrawn yarn was drawn through a heat roller at 80 ° C. so that the residual elongation was 50%, further heat-treated on a heat plate at 145 ° C., and wound up to have a total fineness of 225.3 dtex and a filament. Several 72 drawn yarns were wound up.

Table 1 shows the evaluation results of the obtained core-sheath type composite fiber. The surface resistivity was 7.48 logΩ / cm, the standard deviation of the surface resistivity was 0.03, and the toughness was 21.1, and no crimp occurred. It was also used as a cleaner brush for dry copiers, and the image quality was also good.

Example 2
The process was carried out under the same silk milling conditions and stretching conditions as in Example 1 except that the core-sheath composite ratio was 70/30.

Table 1 shows the evaluation results of the obtained core-sheath type composite fiber. The surface resistivity was 6.75 logΩ / cm, the standard deviation of the surface resistivity was 0.04, and the toughness was 18.8, and a small crimp was present in a part of the treated yarn. Further, it was used for a cleaner brush for a dry copier, and the image quality was at a level that could hardly be understood, although there were 1 to 10 fine streaky stains on the printed matter.

Example 3
The process was carried out under the same silk milling conditions and stretching conditions as in Example 1 except that the core-sheath composite ratio was set to 85/15.

Table 1 shows the evaluation results of the obtained core-sheath type composite fiber. The surface resistivity was 7.89 logΩ / cm, the standard deviation of the surface resistivity was 0.05, and the toughness was 20.4, and no crimp occurred. In addition, it was used for a cleaner brush for a dry copier, and although the printed matter had 11 to 20 fine streaky stains on the printed matter, it was not so noticeable.

Example 4
The procedure was carried out under the same silk milling conditions and stretching conditions as in Example 1 except that the number of holes was 36 and the core-sheath composite ratio was 75/25.

Table 1 shows the evaluation results of the obtained core-sheath type composite fiber. The surface resistivity was 6.85 logΩ / cm, the standard deviation of the surface resistivity was 0.03, and the toughness was 19.9, and no crimp occurred. It was also used as a cleaner brush for dry copiers, and the image quality was also good.

Example 5
The procedure was carried out under the same silk milling conditions and drawing conditions as in Example 1 except that the number of holes was 36.

Table 1 shows the evaluation results of the obtained core-sheath type composite fiber. The surface resistivity was 7.08 logΩ / cm, the standard deviation of the surface resistivity was 0.05, and the toughness was 20.5, and no crimp occurred. Further, it was used for a cleaner brush for a dry copier, and the image quality was at a level that could hardly be understood, although there were 1 to 10 fine streaky stains on the printed matter.

Comparative Example 1
As shown in FIG. 3, the silk milling conditions and drawing conditions were the same as those in Example 1 except that the cross section was changed so that the thickness of the sheath component was uniform.

Table 1 shows the evaluation results of the obtained core-sheath type composite fiber. The surface resistivity was 7.95 logΩ / cm, the standard deviation of the surface resistivity was 0.06, and the toughness was 21.0, and no crimp occurred. In addition, it was used for a cleaner brush for a dry copier, and the image quality was conspicuous with 21 or more streaky stains on the printed matter.

Comparative Example 2
The same silk-reeling conditions as in Example 1 except that the number of holes was 36, the core-sheath composite ratio was 70/30, and the composite form was changed to a cross section in which the width of the sheath component thickness was widened as shown in Table 1. It was carried out under stretching conditions.

Table 1 shows the evaluation results of the obtained core-sheath type composite fiber. The surface resistivity was 6.72 logΩ / cm, the standard deviation of the surface resistivity was 0.03, and the toughness was 18.9, and crimps were present in the entire yarn after the treatment. In addition, it was used for a cleaner brush for a dry copier, and the image quality was conspicuous with 21 or more streaky stains on the printed matter.

Comparative Example 3
The same silk-reeling conditions as in Example 1 except that the number of holes was 36, the core-sheath composite ratio was 85/15, and the composite form was changed to a cross section in which the spread of the sheath component thickness was narrowed as shown in Table 1. It was carried out under stretching conditions.

Table 1 shows the evaluation results of the obtained core-sheath type composite fiber. The surface resistivity was 7.36 logΩ / cm, the standard deviation of the surface resistivity was 0.07, and the toughness was 21.1, and no crimp occurred. In addition, it was used for a cleaner brush for a dry copier, and the image quality was conspicuous with 21 or more streaky stains on the printed matter.

Comparative Example 4
The core-sheath composite ratio was set to 70/30, and the cross section was changed to a cross section in which the thickness of the sheath component was increased as shown in FIG.

Table 1 shows the evaluation results of the obtained core-sheath type composite fiber. The surface resistivity was 6.61 logΩ / cm, the standard deviation of the surface resistivity was 0.03, and the toughness was 17.4, and crimps were present in the entire yarn after the treatment. In addition, it was used for a cleaner brush for a dry copier, and the image quality was conspicuous with 21 or more streaky stains on the printed matter.

Comparative Example 5
As shown in Table 1, the number of holes was 36, and the composite form was subjected to the same spinning conditions and stretching conditions as in Example 1 except that the cross section was changed in the size and spread of the sheath component thickness.

Table 1 shows the evaluation results of the obtained core-sheath type composite fiber. The surface resistivity was 7.10 logΩ / cm, the standard deviation of the surface resistivity was 0.04, and the toughness was 20.1. There was a large crimp on the entire yarn after the treatment. In addition, it was used for a cleaner brush for a dry copier, and the image quality was conspicuous with 21 or more streaky stains on the printed matter.

1: Sheath component 2: Core component 3: Inscribed circle on the surface layer of the sheath component

Claims (3)

The core component is a fiber-forming polymer, and the sheath component is a fiber-forming polymer containing 10 to 50% by weight of carbon black. The sheath component completely covers the fiber surface, and the core-sheath composite ratio (weight ratio) is 85. A core-sheath type composite fiber having a thickness of / 15 to 70/30, wherein the composite form satisfies the following conditions (a) and (b).
(A) 0.05 <(Lmax-Lave) / R <0.20
(B) The ratio of L such that (L-Lave) / R> 0.05 is 10 to 20%.
・ R is the radius of the inscribed circle on the surface layer of the sheath component ・ L = R−r
r is the distance from the center point of the inscribed circle of the sheath component surface layer to the boundary of the core sheath component when the inscribed circle of the sheath component surface layer is divided into 32 in the circumferential direction. The maximum value when the tangent circle is divided into 32 in the circumferential direction ・ Love is the average value when the inscribed circle on the surface layer of the sheath component is divided into 32 in the circumferential direction. The core-sheath type composite fiber according to claim 1, wherein the fiber-forming polymer is polyester. The core-sheath type composite fiber according to claim 1, wherein the fiber-forming polymer of the sheath component is polytrimethylene terephthalate.

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