JP2001098125A - Semiconductive thermoplastic fluorine resin composition and use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductive fluorine resin composition having further more stabilized electric resistivity and the use thereof. SOLUTION: The semiconductive thermoplastic fluorine resin composition includes 70-95 pts.wt. of a thermoplastic fluorine resin and 30-5 pts.wt. of an electroconductive carbon black of <=0.25 hydrogen content, >=10 ml/5 g of hydrogen chloride absorption. This fluorine resin composition is formed to a substantially undrawn, endlessly tubular, semiconductive film and the resultant film is designed for an effectively use as a multiple transcription conveying belt in a tandem type color copying machine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductive thermoplastic fluororesin composition exhibiting a particularly stable electric resistance characteristic, and to its use as a multiple transfer conveyor belt of, for example, a tandem type color copier.

[0002]

2. Description of the Related Art Polyimide containing conductive carbon black, an endless tubular film formed of a fluororesin, for example, an intermediate transfer belt of a color copying machine, or a multiple transfer conveying belt of a tandem type color copying machine. Although partially used, it has already been put to practical use. When the two are compared, the polyimide film molded article is particularly superior in heat resistance and mechanical properties, but the fluororesin film molded article is superior in terms of releasability. This excellent releasability is an important factor for, for example, functional members of a copying machine (for a paper transport roll, an intermediate transfer belt, a multiple transfer transport belt, etc.). In other words, the excellent releasability remarkably acts on the sheet transportability (paper separation), the transferability of the toner, the non-contamination of the non-image portion toner, and the like.

[0003] In the case of a copying machine, for example, a multi-transfer belt in a tandem system or an electrical resistance characteristic (especially stability) which is a very important factor when used as an intermediate transfer belt regardless of the system. about,
The case of a fluororesin film molded article is inferior, and this point has been pointed out in the past and strong improvement is required. Specifically, the inferiority is that the surface resistance (volume resistance) decreases with the repetition of the voltage applied to the belt. The change in the resistance changes the amount of charge stored in the belt, and as a result, lowers the toner image quality.
This is a fatal drawback, especially for color copying.
In addition, a similar phenomenon is observed particularly when the environment is encountered in a high temperature and high humidity environment.

[0004] Because of the above-mentioned problems, attempts have been made to improve this problem. For example, JP-A-8-224802
In Japanese Patent Application Laid-Open Publication No. H10-157, the problem of reduction of the volume resistivity is a problem, and in order to solve the problem, 97 to 75% by weight of a fluororesin is used.
And primary particles are hollow and have a specific surface area of at least 800 m ² / g and a DBP oil absorption of 300 ml / 100 g or more, and 3 to 25% by weight of carbon black, and the surface resistivity of the front and back surfaces is 1 × 10 ⁰ to 10 ^A seamless belt having a resistivity of ¹⁵ Ω / □ and a volume resistivity of 1 × 10 ⁹ to 10 ¹¹ Ω · cm is disclosed and used for intermediate transfer.

[0005]

SUMMARY OF THE INVENTION In the present invention, various studies have been made on a solution to the above-mentioned problem by completely new means different from the above-mentioned publication. As a result, it was possible to solve the problem with even greater improvement, leading to the present invention. The solution is as follows.

[0006]

That is, according to the present invention, there is provided a thermoplastic fluororesin 70 to 9 as described in claim 1.
5 parts by weight, hydrogen content 0.25% or less, hydrochloric acid adsorption amount 10
(Ml / 5g) or more conductive carbon black 30 to 5
And a semiconductive thermoplastic fluororesin composition characterized in that the composition contains at least one part by weight. And the composition is
It is easy to process into various molded articles, for example, molding into an endless tubular film in a substantially unstretched state (Claim 3) and processing this as a belt, for example, a tandem type color copier (Claim 4). In addition, as the thermoplastic fluororesin as the matrix resin constituting the composition, the use of a fluorocopolymer having a melting point of 200 to 320 ° C. is preferable (claim 2). Hereinafter, the present invention will be described in more detail with the following embodiments.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The thermoplastic fluororesin (hereinafter simply referred to as fluororesin) is a polymer which can be plasticized by heat and molded into various shapes. is there. Polyvinylidene fluoride (melting point 170 ° C), polyvinyl fluoride (melting point 200-
210 ° C.), a binary copolymer of ethylene and tetrafluoroethylene (hereinafter abbreviated as ETFE) (melting point 2
60 ° C.), a binary copolymer of ethylene and trifluoroethylene chloride (melting point: 245 ° C.) (hereinafter abbreviated as ECTFE), a binary copolymer of ethylene tetrafluoride and perfluoroalkyl vinyl ether (melting point: 310 ° C) (hereinafter P
FA) and a binary copolymer of ethylene tetrafluoride and polypropylene hexafluoride (melting point: 260 ° C.). Above all, it is easy to mold the obtained composition into any shape (shape, size, thickness, etc.), and it has good heat resistance, bending resistance, etc. and is easy to balance as a whole. A copolymer having a melting point of 200 to 310 ° C. is preferable (claim 2). Among the previous examples, PF
A and ETFE are more preferred. In addition, the melting point of the fluororesin is illustrated as a guide. This is because it changes depending on the molecular weight, the copolymerization ratio and the like. or,
Generally, the fluororesin is provided as a powder, but there is no restriction on the particle size and particle shape.

Next, conductive carbon black (hereinafter simply abbreviated as CB) which is mixed with the fluororesin to form a composition will be described. Generally, the characteristics of CB obtained by the starting material and the production method combined therewith are various, and therefore, the varieties are tens of types. The characteristics are generally expressed by blackness, coloring power, DBP oil absorption, volatile content, PH value, toluene extraction, sieve residue, ash, bulk density, specific surface area, and particle size. The inventors of the present invention have paid particular attention to these characteristics and have studied in detail to solve the above problems, but none of them has been able to solve them with sufficient satisfaction. This is considered to be due to the fact that the fluorocarbon resin and CB originally have incompatible properties. Therefore, it was reconsidered from the following viewpoints that should be cleared. That is, the desired electrical resistance characteristics can be exhibited by adding as little CB as possible. And that the fluororesin is well adsorbed on CB 2
Is a point. As a result, unexpectedly, it was possible to solve the problem all at once by focusing on two factors, that is, the hydrogen atom remaining in the CB and the hydrochloric acid adsorption property of the CB.

That is, the above results show that it is better that the CB contains as little hydrogen as possible. The higher the adsorptivity to hydrochloric acid, the better. Therefore, it is sufficient to select a CB satisfying these conditions.
It is also understood that a numerical limit is taken into consideration, and the amount of hydrogen is 0.25% or less, more preferably 0.20% or less, and further preferably 0.15% or less. And the adsorption amount for hydrochloric acid is CB5
10 ml or more per g, more preferably 13 ml or more,
Furthermore, it is said that it is 15 ml or more. The CB conforming to such conditions has a small variation in the electric resistance value of the CB itself, and maintains a stable quality within a range of, for example, one digit.

The mechanism of action of CB having the above-mentioned properties on a fluororesin is considered as follows. In other words, in a CB having a low hydrogen content, the structure formed between carbons is not hindered by hydrogen atoms, so that the structure is more effectively developed, and as a result, a CB having a lower electric resistance is obtained. When such CB is mixed with a fluororesin, a composition having a desired electric resistance can be obtained with a smaller amount of addition, and a higher level of dispersion can be obtained.
This also means that there is little change in the intrinsic properties of the fluororesin. On the other hand, in the case of CB having excellent hydrochloric acid adsorption properties, the fluororesin binds a large number of fluorine atoms of the same family with chlorine of hydrochloric acid, so that a higher affinity with the CB is generated and the CB is easily adsorbed. As a result, the resin has a structure of the CB.
It becomes possible to disperse in a state where it is firmly adhered to. With such a dispersed state, the electric resistance does not change regardless of whether the applied voltage is repeated or whether the apparatus is placed under high temperature and high humidity.

The fluororesin and CB are mixed to obtain a semiconductive composition. Here, the mixing ratio of the two components may be appropriately determined in consideration of the desired appearance of semiconductivity, moldability, and the deterioration of various physical properties of the fluororesin itself. This is described in claim 1. That is, the resin 70-
95, preferably 80 to 93 parts by weight, CB30
-5, preferably 20-7 parts by weight. The semiconductivity provided by such a composition is approximately 10 ⁸ to 10 ¹⁵ Ω / □ in surface resistance, and 10 ⁶ to 10 in volume resistance.
^{It is in} the range of ¹⁵ Ω · cm.

The composition may be obtained as a simple mixture of the powders of the above components. However, since the composition is actually subjected to various moldings, the mixed powder is prepared in advance, for example, by two-axis molding. It is preferable to melt and knead the mixture with an extruder to form pellets and to prepare a composition. In addition, at the time of this composition, if necessary, various conventionally known additives may be added, but the amount thereof should not interfere with the operation and effect of the present invention. For example, as an example of the additive, the addition of an effective one from various reinforcing agents for the purpose of imparting appropriate hardness to a slightly flexible fluororesin and also increasing the strength can be exemplified.

The composition takes various forms depending on the purpose of use. For example, a coating agent, a filling agent (sealing agent), a mold (equipment part), a web sheet (thick and thin), an endless tubular sheet (thick and thin), etc. which require semi-conductivity. It is.
Among these forms, the sheet may be in a stretched state or in a non-stretched state, but in order to maintain more stable electric resistance characteristics, the sheet in a substantially non-stretched state.
Be good. Further, when the sheet is made into a thin material, that is, a thin endless tubular film having a thickness of about 50 to 300, or even 100 to 250 μm, the non-stretching effect is large. The term "substantially non-stretching" here means that it should not exceed the above-mentioned range of stable electric resistance and should not cause a change in the quality of, for example, toner images. . Therefore, slight stretching may be performed as long as such adverse effects are not substantially present. Substantially no stretching in this sense.

The various forms of use are made by means suitable for each. For example, in the case of a substantially non-stretched endless tubular film, the above-prepared pellets are supplied to a screw-type single-screw extruder having an annular die at a discharge port (a barrel temperature of about 200 to 350 ° C., The die is set to a temperature equal to or slightly lower than the temperature of the tip of the barrel), melted and extruded from the die, and immediately transferred to an external cooling die (also called a chill mandrel) arranged side by side at the tip of the die. While being inserted and cooled, it is drawn without substantially stretching (substantially the same speed as the feeding speed).

The endless endless tubular film may be cut into, for example, a slice and mounted on a roll core for use in delivery of various articles.
This may be used in the form of a belt. In particular, use in a belt form is for an intermediate transfer (type), which is an important functional member of a copying machine (including a printer), and for multiple transfer conveyance in a tendum type color copying machine. Both can be used as more effective belts in the case of a color copier.

For each application, the range of semi-conductivity actually required is different and can be determined by selecting a range suitable for each. For example, the range of use as a multiple transfer conveying belt of a tendum type color copier is described. In this case, the surface resistance is 10
^{12 ~10 14 Ω} / □, a volume resistance of ¹⁰ 10 ^{to 10 12}
It is better to select one in the range of Ω · cm. That is, in this range of the belt, the color on the four photosensitive drums
The visualized image is more stably and effectively transferred to the paper faithfully, and is conveyed successively and multi-copied, and even if the applied voltage or the use environment changes largely in the middle, If color unevenness occurs, or toner
There is no dirt or no sharpness in the image.

Here, for reference, the transfer / conveying portion (main portion) of the tendum type color copying machine will be described with reference to FIG. In the figure, reference numeral 1 denotes a multiple transfer / conveyance belt which is stretched around two rotating rollers 2 and rotates in the direction of the arrow. Numeral 3 denotes photosensitive drums for black (B) -red (M) -yellow (Y) -blue (C) toners, which are horizontally arranged at an equal pitch (this order is not fixed). 4
Are four corotron chargers provided on the back surface of the belt facing the photosensitive drum, and charge the belt by receiving a DC voltage supplied from a power source of 5 (toner image on the photosensitive drum). And the opposite charge). Reference numeral 6 denotes a copy sheet, and reference numeral 7 denotes a fixing device. The sheet is sent to the photosensitive drum 3 on the belt, and the reverse charge stored in the belt attracts a toner-visible image on the photosensitive drum via the sheet, and is sequentially transferred to the sheet. The sheet is sent to the fixing device to complete copying.

In the case of using the sheet molded body, there may be a case where the electric resistance is slightly unstable immediately after molding. In such a case, it is also preferable that the electrical treatment (for example, application of a voltage) is performed to relax and stabilize before actual use.

[0019]

Next, the present invention will be described in more detail with reference to examples together with comparative examples. The hydrochloric acid absorption, the hydrogen content, and the surface resistance (volume resistance) referred to in the text and in this example were measured as follows. ● The hydrochloric acid adsorption amount was determined by weighing 5.0 g of dry CB powder in accordance with JIS K818 according to JIS K1469-1984.
Hydrochloric acid (1+
It is adsorbed by 5) and is shown in ml / 5g. The hydrogen content (%) is a value obtained by measuring the total hydrogen content in the CB by a generally performed elemental analysis method. ● Surface resistance value (hereinafter Rs) and volume resistance value (hereinafter Rv)
Uses the endless tubular film obtained in each example as a sample
500 ohm resistance meter manufactured by Mitsubishi Chemical Co., Ltd. according to SK6911
It is a value measured under application of a voltage of V.

(Example 1) (corresponding to claim 1) As a fluororesin, 88 parts by weight of ETFE (Aflon type COP-55AXT, manufactured by Asahi Glass Co., Ltd., melting point: 260 ° C.) powder and hydrochloric acid adsorption amount: 16.7 (Ml / 5g), CB powder containing 0.04% hydrogen (the average particle size is about 4
2 nm, DBP oil absorption 190 ml / 100 g) and 12 parts by weight were previously mixed in a high mixer, and the mixed powder was supplied to a twin-screw extruder (barrel temperature 200 to 320 ° C.) and melt-kneaded. The mixture was pelletized to obtain a semiconductive thermoplastic fluororesin composition (hereinafter referred to as pellet in Example 1).

(Embodiment 2) (corresponding to claim 3) A single screw extruder having a crosshead die (an annular die having an inner diameter of 244.36 mmφ and a nozzle width of 1.5 mm) (controlled at a temperature of 300 ° C.) at a discharge port. (Barrel temperature 220-320
(Controlled at ゜ C), and extruded while being in contact with a chill mandrel (inner diameter 244.36 mmφ, length 130 mm controlled at 40 ° C.) juxtaposed with the head die, the same speed as the extrusion speed. To obtain an endless endless tubular film.

Thickness of the obtained endless endless tubular film
The height is 150 ± 15 μm, the inner diameter is 240 ± 0.2 μm,
No flow marks or rough skin on the front and back
It was smooth. And Rs is 3.20 × 10¹²
Ω / □, Rv is 1.23 × 10 ¹⁰Ω · cm.

Then, using the endless tubular film,
Check the change of electric resistance against applied voltage under the condition of
did. That is, a voltage of 500 V is applied to the film for 5 minutes.
And stop the application. This ON / OF is repeated 100 times
Was. As a result, Rs was 2.80 × 10 in 20 times.¹²Ω /
□, 2.68 × 10 for 50 times ¹²Ω / □, 75 times 2.
71 × 10¹²Ω / □, 2.69 × 10 for 100 cycles^{1 2}
Ω / □ (Rv at this time is 3.94 × 10¹⁰Ω ・ cm)
With little change but practically no change
You can see that.

(Comparative Example 1) (when CB out of the range is used) Hydrochloric acid adsorption amount 6.5 (ml / 5 g), hydrogen amount 0.5% C
Except for using B powder (average particle size is about 22 nm), mixing and pelletizing are performed under the same conditions as in Example 1, and then extruded using the pellets under the same conditions as in Example 2, An endless endless tubular film was obtained.

The thickness and the inner diameter of the obtained endless tubular film were not different from those of Example 2, but the surface was slightly rough, and the surface was not entirely smooth. Further, Rs is 1.2 × 10 ¹⁴ Ω / □, and Rv is 5.2.
× 10 ¹² Ω · cm. This result indicates that in the CB which is not the present invention, sufficient dispersion is hardly performed, and the desired electric resistance is increased without obtaining the desired electric resistance. In other words, the CB shows that it is difficult to disperse with a stronger affinity and has poor conductivity.

Further, using the endless tubular film described above,
Under the same conditions as in Example 2, the change in electrical resistance with applied voltage
I checked. As a result, Rs was 7.81 × 10 in 20 times.
¹³Ω / □, 8.13 × 10 at 50 times ¹²Ω / □, 75
1.24 × 10 times¹²Ω / □, 9.81 × at 100 times
10^{1 1}Ω / □ (Rv at this time is 7.92 × 10⁹Ω
cm). Each time a voltage is applied and charging is repeated,
It can also be seen that the air resistance changes in a lower direction and is not stable.

(Embodiment / Comparative Example) The endless tubular film formed in Example 2 and Comparative Example 1 was cut into a width of 300 mm, and this was mounted as a multi-transfer transport belt of a tendum type (quadruple) color copying machine. Then, a color copying test was performed under the following conditions. ◎ Test manuscript: Black, red, yellow and blue lines of 3 mm width are 10 m long
A4 size (solid) color originals prepared by sequentially arranging at m intervals. Voltage applied to four corotron chargers provided on the back surface of the belt facing four photosensitive drums.
00 to 700 V (because the voltages applied to the respective chargers are not the same). However, the voltage and current of the power supply of each charger are 2.5
kv-20 μA. ◎ Copy order: black-red-yellow-blue ◎ Number of copies: 60,000 (1500, 3000, 600
抜 き Extraction check every 0, 10,000, 30,000 and 60,000 sheets) 抜 き Extraction check items: Observation of each color density unevenness, white spots, color misregistration (line cut-sharpness) and stains on non-image parts with the naked eye And compared.

As a result, in Example 2, each of the copy sheets
Density unevenness, white spots, color misregistration and stains on non-image areas
Was not seen at all and was copied with extremely beautiful image quality. one
On the other hand, in Comparative Example 1, the respective colors are around 1500 to 3000,
In particular, large drops were observed in the color density,
Non-image toner stain was also observed. And at this point
Then, the copy was topped, the belt was removed, and Rs was measured.
However, 2.3 × 10 ¹²It is Ω / □ and changes greatly
It turns out that there is.

[0029]

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

As compared with the conventional semiconductive fluororesin provided by CB, a semiconductive fluororesin having remarkably high and stable electric resistance characteristics can be obtained.

The moldability is excellent, and various forms can be obtained.
For example, in general, it was not easy to mold a fluorocarbon resin containing CB into an endless tubular film having more stable electric resistance characteristics with high thickness accuracy and smooth front and back surfaces. It's even easier.

In the case of the endless tubular film, for example, a multi-transfer / transport belt of a tendum type color copying machine,
Use of the copying machine for an intermediate transfer belt has become more effective, and copying with better image quality can be stably performed.

[Brief description of the drawings]

FIG. 1 is a schematic view of a multiple transfer / conveying portion of a tendum type color copying machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multiple transfer conveyance belt 3 (BCYC) photosensitive drum 4 Corotron charger 6 Copy paper

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G03G 15/01 114 G03G 15/01 114A 15/16 15/16 (72) Inventor Koichi Nakai 163 Morikawaramachi, Moriyama-shi, Shiga Prefecture Address Gunze Co., Ltd. Research and Development Department Shiga Research Laboratory (72) Inventor Takayuki Hirota 163 Morikawaharamachi, Moriyama-shi, Shiga Prefecture Gunze Co., Ltd. Research and Development Department Shiga Research Laboratory F-term (reference) 2H030 BB42 BB44 2H032 BA09 BA18 3J049 AA01 BF07 BH04 CA10 4F071 AA26 AA27 AA84 AB03 AE15 AF37 AH17 BC01 BC05 BC12 4J002 BD121 BD131 BD141 BD151 BD161 DA036 FD116 GH00 GJ02 GM00 GM01

Claims (4)

[Claims] 1. A thermoplastic fluororesin of 70 to 95 parts by weight, a hydrogen content of 0.25% or less, and a hydrochloric acid adsorption amount of 10 (ml / 5
g) 30 to 5 parts by weight of the above-mentioned conductive carbon black, which is a semiconductive thermoplastic fluororesin composition. 2. The method according to claim 1, wherein the thermoplastic fluororesin has a melting point of 200 to 200.
The semiconductive thermoplastic fluororesin composition according to claim 1, which is a fluorocopolymer at 320 ° C. 3. A substantially non-stretched semiconductive endless tubular film formed from the semiconductive thermoplastic fluororesin composition according to claim 1 or 2. 4. Use of the substantially non-stretched semiconductive endless tubular film molding according to claim 3 as a multiple transfer conveying belt of a tandem type color copier.