JP2001271218A - Semiconductive fiber and its use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductive fiber or its nonwoven texture with much improved electric resistance of especially small dispersion and independence of an electric resistance from an impressed voltage. SOLUTION: This semiconductive fiber is characterized by comprising a thermoplastic resin (e.g. fluorine-based resin) fiber containing an electroconductive carbon black (e.g. <=100 nm particle diameter, <=0.5% hydrogen content and <=101 Ω.cm volume resistance value) spun in a substantially undrawn state. The fiber is a nonwoven texture and is produced, for example, by a melt-blown method. The nonwoven texture is effectively used, for example, as a member for removal of electricity of a toner copy image apparatus and/or a member for electrification.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly improved semiconductive fiber, and more particularly to a semi-conductive fiber having improved electric resistance and an electric resistance independent of an applied voltage. The fiber is made into a non-woven structure, which is effectively used as a member for static elimination and / or a member for charging in a toner-copy image apparatus.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open No. 7-5745 discloses a semiconductive fiber containing a conductive carbon black and the use of the fiber as a charging brush (member) of a toner copying machine. It is known. The same publication specifies the fibers (brush-like, flocking-like, non-woven fabric-like examples) particularly with a water absorption of 0.2% or less. on the other hand,
As the semiconductive fiber, for example, a fiber-coated, woven or non-woven fiber base and a metal fiber or a carbon-containing conductive polymer coated on its surface are used as the semiconductive fiber. Japanese Patent Application Laid-Open No. Hei 7-20681 is used as a device which is used facing away from the body.

[0003]

SUMMARY OF THE INVENTION According to the present invention, a technique which is not known in the prior art including the above is used to repeatedly apply electric resistance and voltage without variation, and to change the resistance even with a higher voltage. It has been found as a result of intensive studies for the purpose of obtaining a semiconductive fiber having no (voltage independent) non-conductive. The means for achieving this task are as follows.

[0004]

That is, the present invention provides a first aspect of the present invention.
Wherein the semiconductive fiber is a thermoplastic resin fiber containing conductive carbon black (hereinafter simply referred to as CB powder) spun in a substantially undrawn state. . The invention according to claims 2 to 5 is also provided as an invention dependent on claim 1. Claim 6 is also provided as one of the effective uses of the semiconductive fiber. The present invention is described in more detail in the following embodiments.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The thermoplastic resin as a matrix resin is not particularly limited as long as it is basically a thermoplastic resin having a fiber forming ability. For example, polyester such as polyethylene terephthalate and polybutylene terephthalate, nylon (6, 66, 610, 11, 12)
Etc.), polyolefins such as polyethylene, polypropylene, and copolymers of ethylene / propylene, fluororesins, polyetheretherketone, and polyethersulfone. However, among them, a fluororesin is preferred. The reason for this is that the effect of the present invention, that is, in terms of electrical resistance and voltage independence without variation, the improvement effect appears larger than other resins, and, for example, charging or discharging while contacting a moving partner. When adopting such a usage form,
There is a danger that this will jump at the contact and cause poor contact,
This is because the resistance to wear and damage is also excellent.

Specific examples of the fluorine-based resin include a single polymer such as polyvinylidene fluoride and poly (trifluorochloroethylene), a binary copolymer of ethylene and trifluorochloroethylene or tetrafluoroethylene, and tetrafluoride. Ethylene and 6
Binary copolymers of propylene fluoride, terpolymers of tetrafluoroethylene, perfluoroalkylvinyl ether and propylene hexafluoride, etc. can be exemplified. Among these, a more preferable polymer is a copolymer represented by the binary copolymer.

As the conductive carbon black (hereinafter simply referred to as CB powder) which imparts semi-conductivity by kneading with the thermoplastic resin, first, various physical properties (particle size, specific surface area, DBP absorption amount, etc.) (PH value, electrical characteristics, volatile components, etc.), and it is preferable to select and use those effective for the present invention. Among these, as physical properties, the particle size is 100 nm or less, preferably 80 nm or less,
Furthermore, it is 50 nm or less and the hydrogen content is 0.5
Hereinafter, a volume resistivity of about 10 ¹ Ω · cm or less, and more preferably preferably CB powder having the following 10 ⁰ Ω · cm. This is because, at least in the case of CB powder that deviates from these physical properties, the fiber molding itself tends to be not smoothly performed (yarn breakage, inclusion of bubbles, etc.), and the addition of a smaller amount of CB powder leads to This is because it becomes difficult to obtain a fiber having a low electric resistance.

There are various types of CB powder (acetylene black, thermal black, furnace black, channel black, etc.) depending on the production method (raw material, combustion conditions). A CB powder having a volume resistance value of 0.5% or less and a volume resistance value of 10 ¹ Ω · cm or less is often found in acetylene black obtained by thermal decomposition (heat generation) using acetylene as a raw material.

[0009] Semi-conductivity can be imparted by kneading CB powder into the above-mentioned thermoplastic resin and melt-spinning it into fibers to obtain semi-conductivity. In other words, it is essential that the film is not substantially stretched. Here, the fiber that is not substantially drawn (not drawn) is not a fiber that is discharged from a die and cooled to form a solid state, and then actively drawn and drawn. Therefore, since it is not the stretching according to the present invention to be stretched (so-called draw) while in the molten state which does not yet become the solid state,
The draw is to say that it is OK. However, it does not mean that the film is not stretched at all, and a slight stretch (for example, about 30% or less) is allowed. The effect of this non-stretching is considered as follows. First, the CB powder originally dispersed uniformly in the resin becomes non-uniform by stretching, and changes to a localized dispersion state. Further, CB powder dispersed with a certain structure is broken by stretching. It is considered that the fibers in such a dispersed state show large variations in electric resistance and also lead to an increase in voltage dependency.

[0010] The electric resistance of the semi-conductive thermoplastic resin fiber A containing substantially undrawn CB powder is as follows:
By changing the powder content, for example, 10 ² to 10 ¹³ Ω
-It can be easily changed in the range of cm, and the number of digits of the resistance value which is an indicator of the variation is within ± 0.5, and further within ± 0.2. That is, for example, 1
0 ⁵ Ω · cm o - da - if the fiber of, where to take even try 10 ^{5 (. ± 0} 5 ^{or less)} is that it is accommodated in Ω · cm.

Next, the means for producing the specified semiconductive thermoplastic resin fiber will be described. First, CB powder corresponding to imparting a desired electric resistance value to the thermoplastic resin is mixed. For example, a particle diameter of several tens nm, a volume resistance value of 10 ¹ to 10
If one wishes to obtain fibers having a volume resistivity of 10 ² to 10 ¹³ Ω · cm using an acetylene black of ⁻¹ Ω · cm,
The mixing amount of the black is about 5 to 20% by weight. Preferably, the mixing means for the two powders is first sufficiently mixed using a high mixer or the like, and the resulting mixed powder is mixed for 2 hours.
It is extruded into a gut while being melt-kneaded by a screw extruder and cut into chips. This is preferably used as a raw material for melt spinning.

Next, the desired chips are formed into a desired fiber by using the obtained chips. The form is monofilament, multifilament, and its thickness depending on the purpose of use.
The cross-sectional shape and the like are determined. This is generally performed by changing the base (number of holes, size, shape). When the liquid is discharged from the die, the liquid is taken out while cooling at substantially the same speed as the discharge speed, that is, substantially without stretching, but it is better to slightly apply the drawer. This is because it is easy to obtain a stable fiber having less variation in electric resistance.

On the other hand, in the case of use in a nonwoven fabric as described in claim 4, for example, the obtained continuous filament is collected or deposited in a nonwoven form continuously or in a separate step. It is made by a so-called spunbond method. However, a method is desired in which a substantially non-oriented fiber is produced at the same time as a nonwoven structure at a time by the following method. Since it can be fiberized almost completely in an undrawn state, a more uniform electric resistance (without variation)
And excellent in voltage-independence. That is, the method is a meltblowing method. The method comprises:
In general, a die in which a number of holes having a diameter of less than 1 mm are arranged in a row with a pitch of about 0.5 mm between holes is used as a die, and slits are provided so that a heated gas of 300 ° C. or more can be blown out from both sides of each hole at a high speed. . The molten resin discharged from each hole is blown off by the high-speed heating gas to be in a fibrous form. This is directly received on a collecting surface 20 to 50 cm away from the hole and cooled to form a nonwoven web.
In addition, this method is basically manufactured under the above conditions,
Since the B powder is contained, the melted thermoplastic resin becomes slightly heavier and it is difficult to blow it out smoothly, or there is a risk of clogging of the base hole. It is desired to take into consideration such as making the particle size smaller.

The volume resistance value of the nonwoven structure obtained as described above can be basically changed by the content of the CB powder, but also by the fineness and the basis weight. Similar to the continuous fiber, it is preferable to form them in consideration of these factors so that they are in the range of 10 ² to 10 ¹³ Ω · cm and the number of digits is within ± 0.5. The nonwoven structure obtained by setting the conditions in such a range also works favorably in various uses similarly to the above-mentioned fibers.

In the case where the fibers or the fibers are used in a non-woven structure, they may be subjected to a heat treatment before use. This is in a substantially non-stretched state, but depending on the type of the CB powder to be mixed and the like, there may be a case where it is slightly worse in terms of, for example, voltage independence. This is because it is possible to improve the fiber or the non-woven structure in such a situation as well as the non-woven structure by the subsequent heat treatment. The heat treatment conditions are lower than the melting point (M) or softening point (S) of the matrix resin, but the upper limit temperature is about M (or S) -30 ° C, and the lower limit temperature is M (or S) It is preferable that the temperature is set within about 1/3 of the temperature and within this range. The time varies depending on the temperature and the like, but is generally within about 10 minutes and about 5 minutes. The heating means may be a method such as passing a heating roll or continuously blowing hot air.

Since the obtained semiconductive thermoplastic fiber has excellent electric resistance characteristics as described above, it is used in various forms and various applications as a member for static elimination or charging. For example, the fiber cut into a predetermined size is sandwiched between horizontally long metal grippers and attached to a printing machine to remove static electricity from a printing paper, from a film, from a variety of electrical components (products), and from other electrical components. There are a use as a member, a use as an electromagnetic wave shield member, and a use as a dust collecting member (utilization of charging and static elimination actions). Another more effective use is a member for static elimination and / or a member for charging of a toner-copy image apparatus as described in claim 6.

The use of the toner-copying image apparatus as a member for removing and charging is as follows. In general, the apparatus is provided with a charger for charging the photosensitive drum in advance and a charge remover for removing electricity before charging. In the color multiple transfer system in which copying is performed using an intermediate transfer belt, the belt is also provided with a charger and a static eliminator. These chargers and static eliminators have contacts, and it is said that the fibers themselves of the present invention or the nonwoven fabric thereof are used for the contacts. This contact is generally used in the form of a brush as described above, and is processed and attached in an appropriate form. However, more preferred is use in non-woven tissues. When used in a non-woven structure, unlike in a brush-like structure, firstly, it can contact the photosensitive drum or the intermediate transfer belt more uniformly, so that it can be charged or discharged efficiently. Ozone generation should be reduced because the danger of discharge is small. This is because abrasion at the tip due to sliding contact is reduced, which is advantageous in that bias voltage changes due to aging, and that the life of the contact is extended.

In addition, the above-mentioned fibers or non-woven fabrics
In general, the same amount of the same CB powder is mixed with the same resin to form the same mono- or multi-filament, which is molded as a base. However, this may be a mixed form composed of various combinations depending on the purpose of use. The thickness of the non-woven tissue ranges from a thin cloth to a thick felt.

A charger for the toner-copier image device;
When the contacts in the static eliminator are used in a non-woven structure, they are preferably used in the form of a single non-woven fabric formed under the same conditions. The attachment by this may be a method of simply cutting the nonwoven fabric appropriately, sandwiching the nonwoven fabric with a metal holding tool, and bringing the cut surface into contact with the photosensitive drum or the intermediate transfer belt,
Rather, it is better to fold the nonwoven fabric two or three times, sandwich the nonwoven fabric between the grippers, and bring the folds into contact. This means that when the nonwoven fabric is simply cut and brought into contact with the cut surface, the nonwoven fabric acts in the same manner as the above-mentioned use in a brush shape, and the effect of the use in the nonwoven fabric does not tend to be maximized. Because there is.

When used as the nonwoven fabric, the nonwoven fabric may be adhered to a metal roller and contacted while rotating. Regardless of the use form, such as a brush form, a non-woven structure form, or an application, generally, the required volume resistance value is different between static elimination and electrification, and electrification is set to be larger than static elimination. The range is 10 ⁴ to 10 ¹³ Ω · c for charging.
m, for static elimination, it is selected in the range of about 10 ² to 10 ⁵ Ω · cm.

[0021]

The present invention will be described in more detail with reference to the following examples together with comparative examples. Incidentally, the volume resistance value (Rv) (Ω · cm) referred to in this example.
Is measured by the following method and calculated by calculation. However, the insulation resistance value of the filament is R (Ω),
A Hiresta resistance meter manufactured by Hewlett-Packard Co., Ltd. was used, while that of the nonwoven fabric was measured using a resistance meter “Hiresta HA probe” manufactured by Mitsubishi Chemical Corporation. In the case of fiber (filament) ..Multi-filament consisting of 64 monofilaments converged to 10 cm
The insulation resistance value was measured under an applied voltage of 100 V while being in close contact with the two electrodes separated from each other, and was calculated by substituting Rv = R × (S / 10). Here, S is the cross-sectional area of the monofilament. ◎ In the case of non-woven structure: weight per unit area A (g / cm ² ), thickness t
(Cm) is placed on a stage, and a ring-shaped probe having an electrode area of 19.6 cm ² is adhered to one side of the non-woven fabric, and the insulation resistance is measured under an applied voltage of 110 V.
= (R / t) x (electrode area) x (1-porosity). However, the porosity is (1−A / t × density of monofilament).

(Example 1) First, a copolymer (neoflon FEP, NP-22, manufactured by Daikin Industries, Ltd.) of tetrafluoroethylene and propylene hexafluoride (average particle size: 100 nm) was powdered into CB powder (acetylene). Black, average particle size 40 nm, hydrogen content 0.03 to 0.05%, volume resistivity 10 ^-1 Ω · cm order) 10 wt% are added and primary mixed with a high mixer, then this mixed powder While melt kneading the body with a twin screw extruder (barrel temperature 225 to 330 ° C),
It was extruded in a gut shape without performing a stretching operation, and this was cut to obtain a pellet.

On the other hand, 64 nozzles having a hole diameter of 0.3 mm
1 with a base (temperature 380 ° C)
Prepare a screw extruder (barrel temperature 225-350 ° C)
The pellet is supplied thereto, and the pellet is discharged at a discharge rate of 1540 g / hour.
in) The film was cooled and wound up by stretching at 5% to obtain a bundle of 64 filaments. The fineness of one filament of this filament was 18d.

Then, the insulation resistance was measured at 100 points over 500 m of this, and the volume resistance was obtained. The volume resistance was found to be in the range of 10 ^4.32 to ^10.4.9 Ω · cm, and there was no variation. The desired semiconductive fibers could be obtained. Although the filament was stretched by 5%, it can be seen from the results of the volume resistance values that the filament was obtained substantially without stretching, as can be seen from the comparative examples described later.

Example 2 The same copolymer as in Example 1 was used for powder of a copolymer of ethylene and tetrafluoroethylene (neoflon ETFE, EP-610 manufactured by Daikin Industries, Ltd.).
B powder was added in an amount of 11.7% by weight and primary mixed with a high mixer.
While being melt-kneaded at 5 to 300 ° C.), it was extruded in a gut shape without performing a stretching operation, and was cut into pellets. Then, spinning was performed under the same conditions as in Example 1 to obtain a bundle multifilament consisting of 65 filaments. The fineness of one filament of this filament was 18.8 d. Then, the insulation resistance value of the obtained multifilament was measured at 100 locations over 500 m, and the volume resistance value was obtained from the measurement.
As a result, 10 ^3.50 to 10 ^{3 . A} desired semiconductive fiber having a range of ⁹⁴ Ω · cm and no variation was obtained. Although the multifilament is stretched to about 5% similarly to the previous example, it can be seen from the result of the volume resistance value that the multifilament is obtained substantially without stretching.

Embodiment 3 First, 500 nozzles having a hole diameter of 0.3 mm are arranged in a line at a pitch of 1.2 mm, and a melt blown die (die temperature 310) having slits through which high-speed hot air is blown from both sides of each hole. C) at the tip (barrel temperature: 180-300 ° C) and a movable collecting table (having mesh holes) arranged 10 cm below the die. Then, hot air at 280 ° C. is blown out from the slit at 700 Nm ³ / hr, and supply to the extruder is started by using the pellet obtained in Example 2 to the extruder, and the discharge speed is 0.4 g / min and the width is 0.4 g / min. It was blown out in a non-woven shape at about 600 mm and collected on the collecting table.
At the time of this collection, a non-woven web was wound while appropriately sucking with a vacuum pump provided at the lower part of the collection table and wound up.
Then, the wound product was passed through a nipplorer and pressed to adjust the thickness to 0.3 mm to obtain a desired semiconductive woven fabric.

The filament (mono) constituting the obtained semiconductive nonwoven fabric has a fineness of 100 nm and a density of 1.7.
3 g / cm ³ and the basis weight of the nonwoven fabric is 200 g / c
It was m ^2. Then, 10 m of the nonwoven fabric was cut out, the position was changed, and the insulation resistance at 100 locations was measured, and the volume resistance was calculated and obtained. As a result, 10 ^3.12 to 10 ^3.
A desired semiconductive nonwoven fabric having a range of ³¹ Ω · cm and no variation was obtained.

Example 4 18.5% by weight of the same CB powder as in Example 1 was added to polyethylene terephthalate (intrinsic viscosity 0.72) powder, and the mixture was primarily mixed with a high mixer. The mixed powder is supplied to a twin screw extruder (barrel temperature of 225 to 30).
At 0 ° C), the mixture was extruded in a gut shape without performing a stretching operation while being melted and kneaded, and cut into pellets to obtain pellets.
The pellets were melt blown using the nonwoven fabric apparatus of Example 3 under the same conditions to produce a semiconductive woven fabric.

The thickness of the obtained semiconductive non-woven fabric is 0.1 mm.
4mm, the fineness of the filaments (things)
8 μm, density 1.34 g / cm³, The basis weight of the nonwoven fabric
Is 100 g / cm²Met. And 10m of the non-woven fabric
Cut out and randomly change positions to insulate 100 locations
The resistance value was measured to determine the volume resistance value. Result 10
^3.2-10^3.5Ωcm
It was possible to obtain a semiconductive non-woven fabric having no irregularities.

(Comparative Example 1) A multifilament was obtained by spinning under the same conditions as in Example 1 except that the draw speed was 100 m / min and the stretching ratio was doubled. The fineness of one filament of this filament was 18d. Then, the obtained multi-filament is 100 m
Insulation resistance values were measured at various locations, and the volume resistance values were determined from these values. As a result ¹⁰ 6.27 ^{~10 1 3.15 Ω} · c
It can be seen that there is variation in the range of m, and that there is a large difference from the substantially no stretching in Example 1.

(Example 5) The voltage dependence of the multifilaments of Example 1 and Comparative Example 1 was examined under the following conditions. Each of the filaments was cut into 20 cm, and the two filaments were placed in close contact with two electrodes separated by 10 cm. Under an applied voltage of 500 V, the insulation was performed every hour for an application time of 30 to 120 minutes. The resistance was measured and converted into a volume resistance value, which was shown in the graph of FIG. It can be seen that the electrical resistance does not change in Example 1, whereas the electrical resistance changes greatly in Comparative Example 1.

[0032]

As described above, the present invention has the following advantages.

It has become possible to obtain a semiconductive fiber having an electric resistance characteristic with even more uniformity.

Further, for example, a great improvement was seen in the electric resistance characteristics under repeated voltage application, and the continuous use was possible for a long time with stable performance quality.

It is expected that a more excellent member for charging or static elimination will be used more frequently in various fields of application. For example, the obtained semiconductive fiber is made into a non-woven structure,
It is effective to use this as a contact of a charge and / or static eliminator of a toner-copying image device.

[Brief description of the drawings]

FIG. 1 is a graph showing a voltage dependency test of Example 5.

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Claims (6)

[Claims] 1. A semi-conductive fiber, which is a thermoplastic resin fiber containing a conductive carbon black spun in a substantially undrawn state. 2. The conductive carbon black has a particle size of 100.
2. The semiconductive fiber according to claim ¹ , having a hydrogen content of 0.5% or less and a volume resistivity of 10 ¹ Ω · cm or less. 3. The semiconductive fiber according to claim 1, wherein said thermoplastic resin is a fluororesin. 4. A non-woven structure having a volume resistance value in a range of 10 ² to 10 ¹³ Ω · cm and a variation in the number of digits within ± 0.5. The semiconductive fiber according to claim 1. 5. The semiconductive fiber according to claim 4, wherein said nonwoven fabric is produced by a meltblowing method. 6. The use of the semiconductive fiber according to claim 4, which is a member for static elimination and / or a member for charging in a toner-copying image apparatus.