JPH05171132A - Seal for carbon box - Google Patents

Abstract

PURPOSE:To provide a seal for a carbon box, excellent in abrasion resistance, low friction properties and sealing properties and capable of exhibiting stable and reliable sealing properties over a long period. CONSTITUTION:The objective seal 3 for a carbon box is equipped with a sealing part around a shaft 11 and in contact with the shaft 11 so that carbon powder in the carbon box 10 may be prevented from entering into bearing units 12 and the above sealing part is made of a lubricating rubber composition. This lubricating rubber composition contains a thermoplastic fluororesin as the first essential component, a fluororubber as the second essential component and a low-molecular fluorine-containing polymer as the third essential component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon box seal having a seal portion provided around the shaft and in contact with the shaft in order to prevent carbon powder in the carbon box from entering the bearing. ..

[0002]

2. Description of the Related Art In a carbon box for quantitatively discharging carbon powder, in order to prevent the carbon powder from entering a bearing portion of a shaft for stirring the carbon powder,
A carbon box seal is provided around this axis. A diene-based synthetic rubber is used for a seal portion which is a portion around the shaft of such a conventional carbon box seal and in contact with the shaft. In particular, in the carbon box of the electrophotographic apparatus, a seal is used to prevent the carbon powder from entering the bearing so that the carbon powder called toner does not leak out of the box and enter the bearing. It is well known that

[0003]

However, since the diene rubbers such as NBR, SBR and CR used for the seal portion of such a carbon box seal have a large sliding resistance, the shaft and the seal portion are not sealed. Grease or the like is applied between them. When grease is applied in this way, carbon powder adheres to this grease, or the grease is discharged over time and the sliding resistance gradually increases, causing problems such as stick-slip and damage. It was A method of reducing the tightening margin has been considered for the purpose of reducing the sliding resistance, but there is a problem that the sealing property is not sufficient.

Further, it has been proposed that a solid lubricant such as a Teflon type or a silicone type is added to a diene rubber to impart a low friction characteristic, but any solid lubricant added has a high hardness. However, there is a problem that the sealability becomes insufficient, the tensile strength and the tear strength are extremely lowered, and the wear resistance is inferior to that of the conventional product.

Silicon rubber and fluororubber have also been investigated as materials for such a carbon box seal, but their significance was not recognized.

Further, a lip shape having an edge has been considered for the purpose of reducing the sliding contact portion, but there is a problem that stability is lacked because grease is unlikely to intervene in the sliding portion.

In recent years, particularly in electrophotographic apparatuses, fine particles of carbon and color carbon have been used in order to obtain a clear image, and more accurate and highly reliable sealing characteristics are required. Also, speeding up is becoming more and more popular,
There is also a demand for improved low friction and wear properties for seals.

An object of the present invention is to provide a carbon box seal which is excellent in wear resistance, friction resistance and sealing properties and which is stable and reliable for a long period of time.

[0009]

A seal for a carbon box according to the present invention comprises a seal portion provided around the shaft and in contact with the shaft in order to prevent carbon powder in the carbon box from entering the bearing portion, At least the seal portion is formed from a lubricating rubber composition, and the lubricating rubber composition,
It is characterized by including a thermoplastic fluororesin which is the first essential component, a fluororubber which is the second essential component, and a low molecular weight fluoropolymer which is the third essential component.

In the present invention, the thermoplastic fluororesin which is the first essential component is a polymer having a carbon chain in the main chain and a fluorine bond in the side chain. Examples of such thermoplastic fluororesin include tetrafluoroethylene polymer (hereinafter abbreviated as PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (hereinafter abbreviated as PFA), tetrafluoroethylene / hexafluoro. Propylene / perfluoroalkyl vinyl ether copolymer (hereinafter abbreviated as EPE), tetrafluoroethylene / hexafluoropropylene copolymer (hereinafter abbreviated as FEP), tetrafluoroethylene / ethylene copolymer (hereinafter abbreviated as ETFE) , Trifluorochloroethylene polymer (hereinafter abbreviated as CTFE), trifluorochloroethylene / ethylene copolymer (hereinafter abbreviated as ECTFE), polyvinyl fluoride (hereinafter abbreviated as PVF), and polyvinylidene Is preferably 1 or more polymers selected from the group consisting of Ruoraido (hereinafter abbreviated as PVDF). In particular, ETFE, PFA and FEP are preferable in consideration of not forming fibers in the kneading step, ease of kneading such as meltability, and maintenance of rubber-like elasticity of the final product. In ETFE, MI value (melt index) is 300 ° C, 21
It is preferably 1 to 20 g / 10 min at 60 g.

Any of the above resins can be produced by various polymerization methods such as catalyst emulsion polymerization, suspension polymerization, catalyst solution polymerization, gas phase polymerization and ionizing radiation irradiation polymerization. The molecular weight should be 50,000 or less, preferably 5,000
Those having a value exceeding 0 and almost not exceeding 20000 are particularly desirable.

As a typical example corresponding to the above conditions, the above-mentioned PFA PF manufactured by Mitsui DuPont Fluorochemical Co.
AMP10, FEP Teflon FEP100 manufactured by Mitsui DuPont Fluorochemicals, ETFE Aflon COP manufactured by Asahi Glass Co., Ltd. CTFE, NEOFLON CTFE manufactured by Daikin Industries, KPV manufactured by Kureha Chemical Co., Ltd.
Examples include polymers and PVF Tedlar manufactured by DuPont.

In the present invention, the fluororubber is a polymer or copolymer of unit monomers containing one or more fluorine atoms on average, and has a glass transition point of room temperature or lower,
There is no particular limitation as long as it has a rubber-like singularity at room temperature, and a wide range can be exemplified.

Examples of the polymerization method of fluororubber include bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization, catalyst polymerization, ionizing radiation polymerization, and redox polymerization. Further, the molecular weight of the fluororubber is usually preferably 50,000 or more, and the one having a high molecular weight as much as possible obtains a good result. Therefore, it is more preferably 70,000 or more, particularly preferably 100,000 to 250,000. Use one.

Typical examples corresponding to the above conditions are tetrafluoroethylene / propylene copolymer Aflas manufactured by Asahi Glass Co., Ltd., vinylidene fluoride / hexafluoropropylene copolymer DuPont manufactured by Showa Denko Viton, and fluorine. Montefluos technoflon, which is a vinylidene fluoride / hexafluoropropylene / tetrafluoroethylene copolymer, Silastic LS, a fluorosilicone elastomer, Dow Corning, PNF, a phosphazene elastomer, PNF,
And a perfluoroelastomer such as Daiel Perflo manufactured by Daikin Industries, Ltd.

The composition obtained by mixing the above-mentioned fluororubber and thermoplastic fluororesin has characteristics as an elastic body. In the present invention, the low molecular weight fluoropolymer, which is the third essential component, is added in order to impart even more excellent sliding properties to such an elastic body.

In the present invention, the low molecular weight fluorine-containing polymer means tetrafluoroethylene (TFE), a fluoropolyether having a main structural unit —C _n F _2n —O— (n is an integer of 1 to 4), Structural unit

[0018]

[Chemical 1]

Among the polyfluoroalkyl group-containing compounds (having 2 to 20 carbon atoms) having, for example, those having a molecular weight of 50,000 or less. In order to impart excellent sliding properties, it is particularly preferable that the low molecular weight fluoropolymer has a molecular weight of 5,000 or less. Among such low molecular weight fluorine-containing polymers, those having an average particle diameter of 5 μm or less of the tetrafluoroethylene low-order polymer represented by the following formula are particularly preferable.

[0020]

[Chemical 2]

Examples of such materials include Vydalx AR manufactured by DuPont and Furuon Lubricant L169 manufactured by Asahi Glass Co., Ltd.

Next, (the n 1 to 4 integer) -C _n F _2n -O- mean molecular weight of 50,000 or less fluoropolyethers having a main structural unit of,

[0023]

[Chemical 3]

Examples include the following: Such polymers are those having a structural unit containing a functional group such as an isocyanate group, a hydroxyl group, a carboxyl group, and an ester group in order to improve the affinity (adhesion) with other compounding materials and additives. desirable.

Specific examples of such fluoropolyethers include the following.

[0026]

[Chemical 4]

These fluoropolyethers may be used alone or in combination. Further, a fluoropolyether having activated hydrogen as a functional group and an isocyanate compound having no polyfluoropolyether group may be used in combination. Further, a fluoropolyether having an isocyanate group, diamines not containing various fluoropolyether groups, triamines, or diols not containing various fluoropolyether groups,
A method of using triols together may be adopted.

In particular, it is preferable to use a fluoropolyether in combination so that the functional groups react with each other to increase the molecular weight. As such, it is likewise desirable to combine, for example, those having units containing isocyanate groups with those having units containing hydroxyl groups.

Examples of the polyfluoroalkyl group-containing compound include compounds having a polyfluoroalkyl group as shown below.

[0030]

[Chemical 5]

Those having the above polyfluoroalkyl group (having 2 to 20 carbon atoms) and having an average molecular weight of 50,000 or less include:

[0032]

[Chemical 6]

And the like, a polymer of a reaction product of a compound having a reactive group and a polyfluoroalkyl group with an ethylenically unsaturated compound having a group which reacts with the reactive group (eg, fluoroalkyl acrylate), and Examples thereof include a reaction product of a compound having a reactive group and a polyfluoroalkyl group with various polymers having a group that reacts with the reactive group, or a polycondensation product of the compound.

As with the above-mentioned fluoropolyalkyl group, the compound containing a polyfluoroalkyl group is a functional group having a high affinity, such as an isocyanate group, for improving the affinity (adhesion) with other compounding materials and additives. A compound having a unit containing a hydroxyl group, a mercapto group, a carboxyl group, an epoxy group, an amino group, a sulfone group, or the like is preferable.

These polyfluoroalkyl group-containing compounds may be used alone or in combination. Further, a polyfluoroalkyl group-containing compound having a reactive group having activated hydrogen and an isocyanate compound having no polyfluoroalkyl group may be used in combination. Also,
Adopting a method such as combining a polyfluoroalkyl group-containing compound having an isocyanate group with various polyfluoroalkyl group-free diamines, triamines or various polyfluoroalkyl group-free diols, triols, etc. May be.

The combination of functional groups is preferable from the viewpoint of increasing the strength, and specifically, it has a polyfluoroalkyl group having 2 to 20 carbon atoms and is selected from a hydroxyl group, a mercapto group, a carboxyl group and an amino group. Combination with a fluorine-containing polymer containing at least one kind, or 2 to 20 carbon atoms
A fluoropolymer having a polyfluoroalkyl group and having a unit containing an isocyanate group, and having 2 to 2 carbon atoms.
There may be mentioned a combination with a fluoropolymer having 20 polyfluoroalkyl groups and further having a unit containing a reactive group having activated hydrogen.

Among these low molecular weight fluoropolymers,
Use of tetrafluoroethylene polymer or fluoropolyether gives excellent results in lubricity,
In particular, it has been found that the use of tetrafluoroethylene polymers gives the most desirable results.

In the present invention, the compounding ratio of the fluororubber and the thermoplastic fluororesin is preferably such that the weight ratio of the fluororubber and the thermoplastic fluororesin is 50:50 to 95: 5. The blending weight ratio of the thermoplastic fluororesin is 5
If it exceeds 0/100, sufficient elasticity cannot be obtained for the intended composition, and if it is less than 5/100, sufficient abrasion resistance cannot be obtained.

The low molecular weight fluoropolymer is preferably 5 to 50 parts by weight based on 100 parts by weight of the total of the fluororubber and the thermoplastic fluororesin. This is because if the compounding ratio of the low molecular weight fluoropolymer is less than 5 parts by weight, sufficient sliding properties cannot be obtained, and if it exceeds 50 parts by weight, the rubber-like elastic properties are impaired.

Further, with respect to the above-mentioned lubricating rubber composition, 3
Abrasion resistance can be improved by adding a cured powder of a thermosetting resin that does not melt at 00 ° C. or a heat-resistant resin powder having a glass transition point of 300 ° C. or higher.

As the thermosetting resin powder, fine powder after thermosetting such as phenol resin and epoxy resin, and as the heat resistant resin having a glass transition temperature of 300 ° C. or higher, polyimide resin, aromatic aramid resin, etc. Fine powder can be used.

Among the commercially available resin powders, the hardened and ground product of the phenol resin is Bellbell H300, manufactured by Kanebo Co., Ltd.
The hardened and ground product of the polyimide resin is manufactured by Mikasa Sangyo Co., Ltd .:
As a pulverized product of PWA20 and an aromatic aramid resin, Asahi Kasei Corporation: MP-P, and as a thermosetting resin powder having a glass transition point Tg of 300 ° C. or higher, Ube Industries: Upilex S (Tg> 500), etc. is there.

The particle size of such thermosetting resin powder is 1
Those having a particle size of up to 15 μm are preferable from the viewpoint of maintaining rubber-like elasticity and facilitating the kneading process. The thermosetting resin powder is preferably added in an amount of 5 to 20% by weight with respect to the first to third essential components. If it is less than 5% by weight, there is no effect of improving wear resistance and
If the amount is more than 10% by weight, the rubber elasticity decreases, which is not preferable.

In addition to the above components, various additives may be added within the range not impairing the object of the present invention. For example, as a vulcanizing agent for fluororubber, isocyanurate, organic peroxide, etc., antioxidants such as sodium stearate, magnesium oxide, and calcium hydroxide, or acid acceptors, antistatic agents such as carbon, silica and It goes without saying that fillers such as alumina, other metal oxides, colorants, flame retardants and the like may be added as appropriate.

The method for mixing the above various raw materials is not particularly limited, and the generally used methods can be used for mixing. For example, the elastomer, which is the main raw material, and the other raw materials may be individually and sequentially or simultaneously mixed with a roll mixer or other mixer. At this time, it is desirable to provide a temperature controller to prevent heat generation due to friction.

When a roll mixer is used,
For finishing mixing, it is more preferable to tighten the roll interval to about 3 mm or less and perform thin threading.

The carbon box seal according to the present invention does not require a particularly limited means in the molding step, and can be subjected to primary vulcanization (for example, at 140 to 170 ° C. for 10 to 30 minutes by a normal press molding method). Pressure 5-10k
gf / cm ² ) and then secondary vulcanization (for example, 200 to
It may be molded at 300 ° C. for 2 to 20 hours without applying pressure to form a seal.

Further, only the lip-shaped portion or the lip-shaped portion, which is the tip of the seal and is in contact with the shaft, is molded with the above-mentioned lubricating rubber composition containing the first to third essential components. The other parts may be composite-molded with general synthetic rubber, plastic or metal.

As the general synthetic rubber at this time, vulcanized rubber such as nitrile rubber, chloroprene rubber, butadiene rubber, urethane rubber, styrene rubber, butyl rubber, acrylic rubber, silicone rubber, ethylene rubber, and fluorine rubber, or urethane, polyester. , Thermoplastic elastomers such as polyamide, vinyl chloride, polybutadiene, and soft nylon, and liquid elastomers such as liquid urethane and liquid butadiene.

[0050]

In the carbon box seal according to the present invention, the seal portion provided around the shaft and in contact with the shaft is formed of the lubricant rubber composition. This lubricating rubber composition is extremely excellent in abrasion resistance, low frictional property and sealing property. Therefore, it is possible to exhibit stable sliding characteristics without using grease as in the conventional case.

Therefore, in the carbon box seal according to the present invention, it is possible to prevent the occurrence of stick-slip and the like, which are problems caused by the conventional use of grease, and damage.

[0052]

【Example】

Examples 1 to 3 First, fluororubber was wound around a roll mixer adjusted to have a roll interval of about 5 to 10 mm, and sodium stearate, MT carbon, ETFE, TAIC and the like were sequentially added in the proportions shown in Table 1. Kneaded Then, the roll interval was adjusted to 1 mm, and mastication was performed about 10 times. For the purpose of preventing frictional heat at this time, cooling water was constantly passed through the roll to keep the roll temperature at 60 ° C or lower. Next, cooling water is stopped, steam is passed through the rolls, the rubber temperature is adjusted to 70 ° C or higher and 90 ° C or lower, and then the roll interval is returned to about 5 to 10 mm, and the low molecular weight fluoropolymer Was added little by little while kneading at the compounding ratio of each example shown in Table 1. Then, the roll interval was again narrowed to 1 mm and mastication was performed about 10 times.

Raw materials used in Examples and Comparative Examples are collectively shown below. The abbreviations are shown in []. In addition, the mixing ratio of each component is all% by weight, but (6)
The raw materials shown in (17) and (19) to (24) are% by weight based on 100 of the total weight of the raw materials shown in (1) to (5) and (18).

(1) Vinylidene fluoride / fluoropropylene copolymer [Technoflon] (Technoflon FOR420 manufactured by Asahi Monte Co., Ltd.) (2) Tetrafluoroethylene / propylene copolymer [AFLAS] (Asahi Glass / Nippon Synthetic Rubber Co., Ltd.) Made by: AFLA
S 150P) (3) Fluorosilicone type elastomer (Silastic LS manufactured by Dow Corning) (4) Tetrafluoroethylene / ethylene copolymer [ETFE] (Aflon COP manufactured by Asahi Glass Co., Ltd.) (5) Tetrafluoroethylene per Fluoroalkyl vinyl ether copolymer [PFA] (Mitsui DuPont Fluorochemical Co., Ltd .: PFA-MP10) (6) Low molecular weight fluoropolymer [low molecular weight TFE]
(Asahi Glass Co., Ltd .: Lubricant L169) (7) Low molecular weight fluorine-containing polymer [low molecular weight FPE (fluoropolyether)] (Japan Enimont Co .: Fomblin Z-Doll) (8) High molecular weight PTFE (Mitsui DuPont Fluoro) Chemical Co., Ltd .: Teflon 7J (9) Carbon (van der Wirt Co .: MT carbon) (10) Sodium stearate (general industrial material) (11) Organic peroxide (α, α′-bis (t-butyl) (Peroxy) diisopropylbenzene) (12) Polyfunctional monomer [TAIC] (triallyl isocyanurate) (13) Magnesium oxide (general reagent) (14) Calcium hydroxide (general reagent) (15) Phenolic resin (Kanebo Ltd.) (Bell Pearl H300) (16) Imide resin (Ube Industries, Ltd .: Upilex S) (17) Imide resin (Mikasa Sangyo Co., Ltd .: PWA20) (18) NBR (Nippon Synthetic Rubber Co., Ltd .: N237H) (19) HAF carbon (20) JSR AROMA (21) Anti-aging agent (22) Vulcanization accelerator CZ (23) Vulcanization accelerator TT (24) Sulfur 150 × 1 using the compound obtained in the above process
Primary vulcanization of a 50 x 2t sheet (170 ° C, 10 minutes,
It was obtained at a pressing pressure of 7 kgf / cm ² . Further, secondary vulcanization (230 ° C., 16 hours, free) was performed to perform vulcanization.

Further, a metal composite type seal as shown in FIG. 1 was produced. With reference to FIG. 1, this carbon box seal 3 has a seal portion 1 made of a rubber composition formed from the above compound inside, and a metal portion 2 is provided around this seal portion 1, and a seal portion is provided. 1 and metal part 2
Are compounded.

A friction test was conducted on the metal composite seal sample and the rubber test piece obtained as described above.
Sealability tests, non-stick and elastic properties were determined. Each test method is as follows.

(1) Friction test A metal composite seal was attached to a carbon box as shown in FIG. Referring to FIG. 2, this carbon box 1
A shaft 11 is provided in the shaft 0, and both ends of the shaft 11 are supported by bearings 12. The carbon box seal 3 is attached to the inside of the bearing 12. The shaft diameter at the end of the shaft 11 is 8.0 mm. While driving this shaft at a rotation speed of 500 rpm, check for carbon leakage with the goal of 2000 hours.
The torque was measured every 00 hours.

(2) Non-adhesion test In order to confirm the non-adhesiveness with the toner, the contact angle of each test piece surface to water was measured with a goniometer contact angle measuring machine. I judged that the sex was good.

(3) Elastic body property test JIS-K6301 was applied to the obtained sheet-shaped test piece.
The tensile strength at break, the tensile elongation at break, and the hardness (JIS-A) were measured according to.

The results obtained as described above are shown in Table 3. In Table 3, the sealability indicates the time at which leakage of carbon powder occurs in the friction test.

Examples 4 to 10 In the proportions shown in Table 1, mixing was carried out in the same manner as in Examples 1 to 3.
Molded and vulcanized. Further, the preparation of the test piece and the test method were also carried out in the same manner as in Examples 1 to 3. The measurement results are shown in Table 3.

Comparative Examples 1 to 5 In Comparative Examples 1 to 5, the raw materials were blended in the proportions shown in Table 1, and mixing, molding and vulcanization were performed in the same manner as in Examples 1 to 3. Further, the preparation of the test piece and the test method were also carried out in the same manner as in Examples 1 to 3. Table 3 shows the measurement results
It was shown to.

Comparative Examples 6 and 7 Comparative Examples 6 and 7 were prepared by blending the raw materials shown in Table 2,
Mixing, molding, and vulcanization were performed in the same manner as in Examples 1 to 3. The test pieces were prepared and tested in the same manner as in Examples 1-3. The measurement results are shown in Table 2.

[0064]

[Table 1]

[0065]

[Table 2]

[0066]

[Table 3]

As is clear from the results shown in Table 3, when the carbon box seal in which the seal portion was formed from the lubricating rubber composition according to the present invention was used, the friction torque was remarkably lower than that of the comparative example. Moreover, it can be seen that the sealing property is very excellent. It is also seen that the elastic body characteristics are excellent.

FIG. 2 shows an example in which the carbon box seal according to the present invention is used as the carbon box seal provided with the rolling bearing 12, but a carbon box provided with the resin bearing 22 as shown in FIG. Needless to say, the carbon box seal according to the present invention can also be applied.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment according to the present invention.

FIG. 2 is a sectional view showing an example in which an embodiment according to the present invention is attached to a carbon box.

FIG. 3 is a cross-sectional view showing another type of bearing in which the carbon box seal according to the present invention can be used.

[Explanation of symbols]

 1 Seal Part 2 Metal Part 3 Carbon Box Seal 10 Carbon Box 11 Shaft 12 Bearing 22 Resin Bearing

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C10M 107: 38 145: 24 149: 18) C10N 20:06 Z 8217-4H 30:06 40:02 50:08

Claims (7)

[Claims] 1. A seal for a carbon box, comprising a seal portion provided around the shaft and in contact with the shaft in order to prevent carbon powder in the carbon box from entering the bearing portion, wherein at least the seal portion is lubricated. A rubber composition, wherein the lubricating rubber composition comprises a thermoplastic fluororesin as a first essential component, a fluororubber as a second essential component, and a low molecular weight fluoropolymer as a third essential component. Including a carbon box seal. 2. The seal for a carbon box according to claim 1, wherein a cured powder of a thermosetting resin or a heat resistant resin powder having a glass transition point of 300 ° C. or higher is added to the lubricating rubber composition. 3. A group in which the thermoplastic fluororesin as the first essential component comprises a tetrafluoroethylene / ethylene copolymer, a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer and a tetrafluoroethylene / hexafluoropropylene copolymer. The carbon box seal according to claim 1, which is one or more selected from the group consisting of: 4. The second essential component has a molecular weight of 100,000 to 25.
The seal for a carbon box according to claim 1, which is a fluororubber. 5. A fluororubber as the second essential component is a tetrafluoroethylene / propylene copolymer, a vinylidene fluoride / hexafluoropropylene copolymer, a vinylidene fluoride / hexafluoropropylene / tetrafluoroethylene copolymer, The carbon box seal according to claim 1, which is one or more polymers selected from the group consisting of fluorosilicone-type elastomers and perfluoro-type elastomers. 6. The low molecular weight fluoropolymer as the third essential component is selected from the group consisting of tetrafluoroethylene polymers, fluoropolyethers and polyfluoroalkyl group-containing compounds which are polymers having a molecular weight of 50,000 or less. The seal for a carbon box according to claim 1, which is one or more kinds of polymers described above. 7. The seal for a carbon box according to claim 1, wherein the low molecular weight fluoropolymer which is the third essential component is a tetrafluoroethylene polymer having an average particle size of 5 μm or less.