JPH08272208A - Conductive fluororubber roll - Google Patents

Abstract

PURPOSE: To provide a conductive fluororubber roll which has good workability for kneading, enables die molding at low temp. and has low hardness and no foamability by adding a conductive powder to a low hardness fluororubber and molding. CONSTITUTION: This conductive fluororubber roll is produced by mixing and kneading. (A) 100 pts.wt. of polyol-crosslinked fluororubber, (b) 10-100 pts.wt. of liquid fluororubber, (C) 0.1-10 pts.wt. of polyol crosslinking agent having at least one OH group sililated in one molecule and (D) 5-1000 pts.wt. of conductive powder and then hardening the obtained fluororubber compsn. to form a fluororubber layer on a core metal. The obtained rubber layer has <=10<10> Ω.cm volume resistivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive fluororubber roll, particularly a fluororubber composition having electroconductivity, which is useful for a static eliminating roll, a transfer roll, a charging roll, a developing roll, a fixing roll and the like of a copying machine. The present invention relates to a conductive fluororubber roll using.

[0002]

2. Description of the Related Art Since fluororubber is an elastomer excellent in heat resistance, chemical resistance, mechanical strength, etc., it is industrially used in a wide range of fields mainly in the automobile and machine industries. However, fluororubber has high hardness even in the polymer itself before cross-linking, and has high green strength near room temperature, so skill is required for kneading work when a large amount of powder filler is added for the purpose of reinforcement and cost reduction. However, the obtained fluororubber has a disadvantage that it is not possible to obtain a molded product having a low hardness, and the use thereof is limited, and particularly when a conductive powder is added for the purpose of improving conductivity. Is poor in workability because the conductive effect cannot be obtained unless added in a large amount, and it becomes difficult to mass-produce industrially. There is a drawback that you cannot get it. However, lowering the hardness of rubber rolls has a great impact on the cleanliness of images on office equipment, abrasion of rubber rolls, and longer life. It is desired to develop a conductive fluororubber that takes advantage of characteristics such as resistance stability of the above.

Therefore, various attempts have been made to improve this fluororubber polymer by blending it, for example, by kneading an additive having a siloxane bond to lower the hardness and improve the roll workability and mold releasability. However, since the silicone component is not compatible with fluororubber, the composition obtained has the risk of bleeding of the silicone component and storage stability. There is also a problem that the molded product has a risk of bleeding of the silicone component and the mechanical properties are remarkably deteriorated. This is also the case when other synthetic rubbers are added to the fluororubber, and blending with various polymers and co-crosslinking have been attempted for the purpose of cost reduction (see JP-A-60-101135). Since the molded products are inferior to the original physical and chemical properties of fluororubber, there are very few examples in which they have been industrially put to practical use.

[0004]

Therefore, this fluororubber is called a low molecular weight liquid fluororubber that can be added to fluororubber, is stable at room temperature and is liquid, and has the same molecular structure as fluororubber. Polymers are industrially used for improving the processability and lowering the hardness of fluororubber. For this liquid fluororubber, please refer to Daiel G101.
[Taikin Industry Co., Ltd. product name] and Viton LM [Showa Denko-Jupon Co., Ltd. product name] are commercially available.
This product is industrially unusable even if it is crosslinked and rubber-like, and it is effective even if added in a small amount.
If added in a large amount, it will foam and become unmoldable, so there is a limit to the reduction in hardness of fluororubber. Further, it has been attempted to reduce the hardness by using a polyol-crosslinked fluororubber and a liquid fluororubber (see JP-A-6-293850).
No studies have been conducted on its application to electrical conductivity or rolls.

On the other hand, as a conductive rubber material for rolls, a silicone rubber mixed with a conductive powder is most commonly used. This silicone rubber is a rubber having a low hardness and easy to knead. It is also easy to do, even if a large amount of conductive powder is added to obtain conductivity, roll work is easy and the obtained rubber cured product has low hardness and can be made into flexible rubber. It can be cured without using sulfur, and it has excellent heat resistance and weather resistance, so it is not necessary to add antioxidants and antioxidants, and there is no contamination by unreacted crosslinking agents or additives. Because there is no
It can be preferably used in an environment that requires conductivity. However, since most of this silicone rubber swells in organic solvents and oils, it is difficult to use it in the environment in which it is used. There is also a problem that contact failure occurs when the insulating layer is formed on the electrical contact.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a conductive fluororubber roll which solves the above disadvantages and drawbacks. 100 parts by weight of cross-linked fluororubber, B.I. Liquid fluororubber 10 to 100 parts by weight, C.I. 0.1 to 10 parts by weight of a polyol crosslinking agent in which at least one OH group in one molecule is silylated, D.I. The volume resistivity of cured fluororubber composition consisting of 5 to 1,000 parts by weight of conductive powder is
It is characterized in that a fluororubber layer of 10 ¹⁰ Ωcm or less is provided on a core metal.This conductive fluororubber composition can be crosslinked at low temperature and contains a large amount of liquid fluororubber. It has an advantage that a low hardness molded article of fluororubber which does not foam even when added is obtained.

[0007]

The conductive fluororubber roll of the present invention is, as described above, a polyol crosslinked fluororubber, a liquid fluororubber,
It is obtained by curing a predetermined amount of a mixture of a polyol crosslinking agent in which at least one OH group in one molecule is silylated and a conductive powder. The polyol-crosslinked fluororubber as the component A used here is a highly fluorinated elastic copolymer, which includes an elastic copolymer of vinylidene fluoride and hexafluoropropene, pentafluoropropene, and trifluoropropene. Examples thereof include elastic copolymers with one or more kinds of ethylene, vinyl fluoride, perfluoro (methyl vinyl ether), perfluoro (propyl vinyl ether), and the like. Among these, vinylidene fluoride-hexafluoro A propene binary elastic copolymer and vinylidene fluoride-tetrafluoroethylene-hexafluoropropene ternary elastic polymer are said to be preferable. Further, this polyol-crosslinked fluororubber preferably has a viscosity at 100 ° C. of 1,000 poise or more in order to obtain sufficient properties such as elasticity, and more preferably a rubber-like polymerized fluororubber. .

The liquid fluororubber used as the component B is used as a hardness reducing agent for the fluororubber used as the component A. The addition of the liquid fluororubber enables the hardness of the fluororubber to be lowered. , This is vinylidene fluoride-
Hexafluoropropene binary elastic copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropene ternary elastic polymer and other low molecular weight polymers, 1
The viscosity at 00 ° C is 500 poises or less, preferably 200 poises or less, and when the viscosity at 100 ° C exceeds 500 poises, the hardness lowering effect is reduced. It is usually used for improving the processability of fluororubber and cannot be crosslinked by itself. Liquid fluororubber is commercially available as specific product names such as G101 (previously) and Viton LM (previously), and can be easily obtained. However, this compounding amount is 100 parts by weight of fluororubber as the A component. Against department
If it is less than 10 parts by weight, the kneading workability with the fluororubber does not improve so much, in addition, the hardness of the fluororubber does not decrease so much, and if it is more than 100 parts by weight, on the contrary, the kneading workability deteriorates due to sticking. This is required to be in the range of 10 to 100 parts by weight, since this tends to cause foaming during crosslinking, and the preferred range is 20 to 80 parts by weight.

Next, the silylated polyol crosslinking agent as the C component used here is an O in a molecule such as a polyhydroxy aromatic compound and a fluorine-containing polyaliphatic compound.
At least one H group is silylated, and
Those described in 6-73258 are preferably used.
Specifically, bisphenol A, bisphenol B, bisphenol AF, 1,3,5-trihydroxybenzene, hydroxyresorcin, 2-t-butylhydroquinone, 2-methylresorcin, 1,5-dihydroxynaphthalene, 2,7-dihydroxy. Naphthalene, 2,2-bis (4-hydroxyphenyl) butane, 3,3,5,5
- tetrachloro bisphenol A, _{4,4-dihydroxydiphenyl, CF 2 (CF 2 CH 2} OH) 2, HOCH 2 (CF 2) 4 OCF (CF 3) C
H ₂ OH, CF ₂ (CFHCF ₂ CH ₂ OH) ₂ , and (CF ₂ ) ₃ (CFHCF ₂ CH ₂ OH) ₂ are silylated OH groups, and bisphenol A is particularly preferable. Bisphenol B,
Examples thereof include bisphenol AF and hydroquinone in which at least one OH group is silylated.

The silylating agent has the formula

Embedded image And X is —H, which is reactive with an OH group,
Functional groups such as —Cl, —OH, and —NHR ₁ (R ₁ is an organic group or an organic group containing silicon), R ¹ , R ² , and R ³ are O.
An organic group that does not react with the H group or an organic group containing silicon,
Specifically, _{-CH 3, -CH 2 CH 3,} -CH 2 CH 2 CH 3, -C 6 H 5, -CHC
_{H 2, -CH 2 CH 2 CF} 3, -CHC (CH 3) 2, -Si (CH 3) Although such ₃ is illustrated, in particular -CH ₃ is Of these, -CH ₂ CH _3, -C ₆ H
₅ , -CH ₂ CH ₂ CF _{3 and the} like are preferable.

Among the above silylating agents, hexamethyldisilazane is preferable because of its easy reaction, and it can be silylated by reacting it with a polyhydroxy compound at room temperature. At this time, it is preferable that all the OH groups in the polyhydroxy compound are silylated, as long as at least one OH group in the molecule is silylated, but the OH groups in the molecule are completely silylated. If not, the vulcanization characteristics and mold releasability are poor, and foaming may occur. The silylated polyol crosslinking agent is particularly represented by the following formula

Embedded image What is shown by is illustrated.

If the amount of the silylated polyol cross-linking agent is less than 0.1 parts by weight based on 100 parts by weight of the fluororubber, the resulting fluororubber cured product will have inferior physical properties. However, this does not give an advantage in physical properties, and rather causes the risk of bleeding.
It may be in the range of up to 10 parts by weight, but the preferred range is
The amount is 0.5 to 5 parts by weight.

In this reaction, a catalyst may be added, and this catalyst has the formula

Embedded image (Where X is P or N, Y is halogen, R ⁵ , R ⁶ ,
R ⁷ and R ⁸ are compounds each represented by a monovalent hydrocarbon group), or a compound of the formula [(R ⁹ ) ₃ P═N = P (R ¹⁰ ) ₃ ] Y (where Y is halogen, R ⁹ and R ¹⁰ are (Monovalent hydrocarbon group)
The onium salt or iminium salt represented by can be used. These act as a crosslinking accelerator,
Specific examples of these are disclosed in JP-A-59-206451 and JP-A-60-6.
No. 5048 and JP-A No. 62-30143 may be used. The onium salt is preferably benzyltriphenylphosphonium chloride or bromide, and the iminium salt is bisbenzyldiphenylphosphine iminium chloride. However, the addition amount of these may be 0.1 to 10 parts by weight, preferably 0.2 to 3 parts by weight.

In this reaction, it is preferable to add a metal compound such as magnesium oxide, calcium oxide, lead oxide, calcium hydroxide, barium stearate, sodium stearate or the like as an acid acceptor, and these are used alone. Alternatively, two or more kinds may be combined, but
The blending amount may be 1 to 20 parts by weight.

The conductive powder added as the D component in the present invention is an important component for making the conductive fluororubber roll conductive, and for example, conductive carbon black,
Examples include graphite powder, carbon fiber powder, metal powder, metal short fiber powder, oxides of tin and indium, or inorganic powder such as glass, alumina and mica coated with metal. From the viewpoint of stability, conductive carbon black is particularly desirable, and specific examples thereof include acetylene black, conductive furnace black, super conductive furnace black, extra conductive furnace black, and conductive channel black. The compounding amount of this product is 100% fluororubber.
If it is less than 5 parts by weight, it is difficult to obtain conductivity, and if it is more than 1,000 parts by weight, kneading becomes difficult, and the obtained fluororubber cured product may lose flexibility. However, the preferable range is 10 to 800 parts by weight. The dispersion of these powders,
In order to reinforce and improve wettability, it may be treated with a silane-based or titanate-based surface treatment agent before use.

Since it is desirable to completely disperse each of these components by kneading, these are conventionally used two rolls for rubber, kneader, pressure kneader,
You can work with a Banbury mixer, etc.,
Since liquid rubber is added to this and workability is improved as compared with conventional fluororubber, kneading can be easily performed without using a special device. Known fillers and colorants may be added to this composition, and as the filler, silica, alumina, red iron oxide, clay, calcium carbonate, titanium oxide, polytetrafluoroethylene powder, various heat-releasing fillers are used. And the like, silica is preferred from the viewpoint of reinforcement, but since the present invention is intended to impart conductivity, the addition amount is preferably small, and 10 parts by weight or less. However, this may be treated with a silane-based or titanate-based surface treatment agent for the same reason as the conductive powder.

Since this composition uses a silylated polyol cross-linking agent, it has good vulcanization characteristics, is productive even at a lower temperature (160 ° C. or lower) than usual, and cures without foaming. Therefore, the molding conditions may be selected at 130 to 200 ° C. for 5 minutes to 2 hours, preferably 130 to 160 ° C. for 5 minutes to 30 minutes depending on the size of the roll to be molded, the wall thickness, the molding method, and the like. . Further, in order to stabilize the formed roll, secondary vulcanization may be performed at 200 to 250 ° C. for about 1 to 72 hours.

It should be noted that this molding apparatus may be a conventionally used rubber processing machine, and therefore, examples thereof include die molding by a rubber press, HAV by an extruder and molding by steam crosslinking. In each case, since low-temperature crosslinking is possible and workability is good, it can be easily processed without using any special device.

Further, aluminum, iron, SU of this product
Regarding the adhesion of S etc. to the roll core metal, in the integral molding by press, the fluororubber primer which uses the commercially available silicon compound having an amino group as an adhesive component is applied to the core metal before molding. It can be easily fixed by using an epoxy adhesive for post-adhesion of the molded product, and if polishing is necessary, it can be processed without any problem with the equipment used for ordinary rubber polishing. be able to.

[0020]

EXAMPLES Next, synthesis examples, examples and comparative examples of the cross-linking agent used as a reference example used in the present invention will be described. (Reference example: Synthetic example of cross-linking agent) To a solution of 16.1 g (0.1 mol) of silylating agent (hexamethyldisilazane) and 10 g of toluene, 33.6 g (0.1 mol) of bisphenol AF was added and mixed and stirred. At room temperature, the reaction started, gas was generated along with the smell of ammonia, and dissolution of powder bisphenol AF was observed. This is because the silylating agent hexamethyldisilazane decomposes to generate ammonia and bisphenol AF It can be presumed that the OH group of 1 is silylated. After the dissolution was completed, the product obtained by removing the toluene and volatile components under reduced pressure became white crystals.

Examples 1 to 3 Vinylidene Fluoride-Hexafluoropropene Binary Copolymer FC2145 [trade name of Sumitomo 3M Co., Ltd.]
(Rubber-like, viscosity cannot be measured) is used as liquid fluororubber as component B as Daiel G101 (viscosity at 60 ° C is 5
00 Poise) (supra), and the silylated polyol cross-linking agent as the C component is the one obtained in the above-mentioned reference example,
As the conductive powder as the D component, acetylene black as the conductive carbon 1 [trade name of Denki Kagaku Co., Ltd.],
Ketjen EC [trade name of Akzo Co.] was blended as the conductive carbon 2 in the blending amount shown in Table 1, and these were kneaded with a two-roll rubber roll. I was able to get things.

Then, in making a 2 mm thick rubber sheet using this composition, molding was carried out at 150 ° C. for 20 minutes, and a good fluororubber molded product without foaming was obtained. Was subjected to secondary crosslinking at 230 ° C. for 24 hours, and the physical properties of this product were measured. The results shown in Table 1 below were obtained. At this time, when the amount of conductive carbon black added was increased, the hardness gradually increased, but the resistance value rapidly decreased, and this rubber sheet was left in silicone oil at room temperature for 24 hours. The volume change rate at that time was 5% or less.

Next, this material was molded into a roll. The roll shaft used was an aluminum rod with an outer diameter of 15 mm, and a primer for fluororubber FC5150 [trade name of Sumitomo 3M Co., Ltd.] was applied with a brush. After air-drying for 1 hour, the primer layer is peeled off with a width of 1 mm in order to make it conductive with the rubber, and then the rubber layer is molded to the same thickness as the rubber sheet using a mold so that the rubber layer becomes 2 mm. When a rubber roll was prepared by polishing with a rubber grinder to a rubber thickness of 1.5 mm, a conductive fluororubber roll was easily obtained.

Examples 4 to 5 The conductive carbon blacks used in Examples 1 to 3 were mixed in the amounts shown in Table 1 by changing the type and the amount added, and kneading in the same manner as in Examples 1 to 3. Then, the composition was molded and the physical properties of this composition were measured, and the results shown in the following Table 1 were obtained. In addition, since the addition amount of carbon black was smaller than that of Examples 1 and 2, the resistance value was low and the increase in hardness was also small, and this was electrically conductive in the same manner as in Examples 1 to 3. When a flexible fluororubber roll was molded, it could be easily integrally molded and showed conductivity.

[0025]

[Table 1]

Example 6 Using the same material as in Example 1, a pipe-shaped molded product having an inner diameter of 15 mm and an outer diameter of 19 mm was manufactured under the same molding conditions as in Example 1 to produce a conductive fluororubber. To insert into a similar roll shaft and conduct electricity, apply epoxy adhesive Hibon 3591 [Hitachi Chemical Co., Ltd. product name] only to the end of the contact surface between rubber and shaft, and dry at 120 ° C. When the adhesive was cured by leaving it in the machine for 2 hours, a good rubber roll having conductivity between the rubber and the shaft was obtained.

Comparative Example 1 Without adding the conductive carbon black in Example 1,
A composition was made in the same composition as in Example 1 except that 3 parts by weight of MT carbon [trade name of Harbor Company], which is a filler often used for reinforcing fluororubber, was added, and a fluororubber molded body was made from this to obtain its physical properties. Table 2 to be described later
The result was as shown in Table 1. The hardness was extremely low, but it was not conductive.

Comparative Examples 2 to 3 Conductive carbon black was added without adding the liquid fluororubber used in Examples 1 and 2, and roll kneading was performed. The fluororubber molded product showed conductivity as shown in Table 2 described later, but it was high in hardness and poor in rubber elasticity.

Comparative Example 4 Silylated bisphenol AF used in the examples
When a compound shown in Table 2 was used as a non-silylated bisphenol AF by a processing method according to the example, this compound foamed and the crosslinking was insufficient, and the physical properties of the sample were measured. I couldn't. Therefore, the molding conditions were extended to 150 ° C for 40 minutes, but the foaming could not be suppressed, and the temperature was 160 ° C, 20 minutes, 170 ° C, 2 minutes.
I tried molding in 0 minutes, but it was in the same foamed state, and it was difficult to work regardless of molding conditions.

Comparative Example 5 The conductive carbon black in Example 1 was not added,
A composition containing 40 parts by weight of the MT carbon filler (described above) used to reinforce the fluororubber was molded and the results are shown in Table 2.
Although it showed a small increase in hardness as shown in, it did not show any conductivity.

[0031]

[Table 2]

Comparative Example 6 Conductive silicone rubber KE3603U [trade name of Shin-Etsu Chemical Co., Ltd.] and crosslinking agent C-3 [trade name of Shin-Etsu Chemical Co., Ltd., paste containing 20% dicumyl peroxide] 4 parts by weight was added to make a silicone rubber sheet under the molding conditions of 170 ° C. for 10 minutes and immersed in silicone oil at room temperature for 24 hours.
Therefore, it was confirmed that this material is unsuitable as a copier roll that comes into contact with silicone oil.

Reference Example FIG. 1 shows displacement-load curves of the fluororubber used in Example 2 and the fluororubber used in Comparative Example 2 having substantially the same volume resistance (measured by an autograph). With the fluororubber used in the present invention, displacement of the rubber occurs with a small load to obtain a fluororubber having the same resistance. In other words, it can be seen that the nip width as a rubber roll is easy to take and that it has elasticity.

[0034]

The present invention relates to a conductive fluororubber roll, which has a hardness of 10 points or more lowered by the addition of a liquid fluororubber, and since the polyol crosslinking agent is silylated, the fluororubber has a low temperature. Since it is possible to crosslink with, and by adding it, it is possible to prevent foaming due to the addition of liquid fluororubber, so it is possible to easily obtain a low hardness molded article of fluororubber. It also has conductivity, so it can eliminate static electricity. Roll, transfer roll, charging roll,
The advantage is that a conductive fluororubber roll that is useful as a fixing roll can be easily obtained.

[Brief description of drawings]

FIG. 1 shows displacement-load curves of the fluororubber used in Example 2 shown in the reference example and the fluororubber used in Comparative example 2.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03G 15/02 101 G03G 15/02 101 15/16 103 15/16 103 15/20 101 15/20 101 21/06 H01B 1/20 Z // H01B 1/20 G03G 21/00 340

Claims (2)

[Claims] 1. A. First Embodiment 100 parts by weight of polyol-crosslinked fluororubber, B. Liquid fluororubber 10 to 100 parts by weight, C.I. 0.1 to 10 parts by weight of a polyol crosslinking agent in which at least one OH group in one molecule is silylated, D.I. A conductive rubber comprising a core rubber and a fluorine rubber layer having a volume resistivity of 10 ¹⁰ Ω · cm or less obtained by curing a fluorine rubber composition containing 5 to 1,000 parts by weight of conductive powder. Rubber roll. 2. The conductive fluororubber roll according to claim 1, wherein the conductive fluororubber roll is selected from static electricity removing rolls for office machines, transfer rolls, charging rolls, developing rolls and fixing rolls.