JP2003167462A - Heating roll for fixing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating roll for fixing having excellent durability and resistance against stress cracks. <P>SOLUTION: A fluorocarbon resin coating layer (3) having 5 to 20% elastic limit and 1 to 3 melt flow rate (MFR) is applied on the surface of a rubber elastic body (2) formed on the periphery of a hollow cylindrical core metal (1), and then calcined. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a fixing roll used in a fixing portion of a copying machine or the like, and more particularly, to a heating roll.

[0002]

2. Description of the Related Art Conventionally, an adhesive layer made of an addition reaction type self-adhesive silicone rubber is provided on the surface of a silicone rubber elastic layer provided on the outer circumference of a hollow cylindrical cored bar (hereinafter referred to as "core"). When adhered, melt flow rate (MF
R) is 2.0 or less, a fluororesin-coated elastic roller (hereinafter, referred to as “roll”) formed by coating a fluororesin made of tetrafluoroethylene-hexafluoroethylene-hexafluoropropylene copolymer (FEP) as the outermost layer portion (Abbreviated) is known. (JP-A-6-126896
However, the above-mentioned configuration has the following inconveniences. That is, in a roll that is exposed to high temperatures during the fixing operation, since the degree of expansion and contraction of the fluororesin coating layer is originally smaller than that of the silicone rubber of the inner layer, the coating layer cannot follow the silicone rubber layer, and as a result, However, there was a problem in durability and stress crack resistance, such as cracking on the surface of the coating layer when used for a long time. Further, the fluororesin used is tetrafluoroethylene-
Since it is a hexafluoropropylene copolymer (FEP),
There was still room for improvement regarding the heat resistance, abrasion resistance and non-adhesiveness of the roll.

[0003]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a fixing heating roll having excellent durability and stress crack resistance.

[0004]

The present inventors have found that among the physical properties of the fluororesin coated on the rubber coating layer on the core metal, particularly when the elastic limit and the melt viscosity are within certain ranges,
It was clarified that the above-mentioned problems of durability and stress crack resistance can be solved.

Thus, according to the present invention, the elastic limit on the surface of the rubber elastic body provided on the outer periphery of the hollow cylindrical core metal is 5%.
Provided is a heating roll for fixing, which is obtained by coating a fluororesin having a melt viscosity (MFR) of 1 to 3 at 20% and baking the coating.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view of a fixing roll of the present invention. FIG. 2 is a cross-sectional view of FIG. 1 and 2, (1) is a core metal, (2) is a rubber elastic body formed on the outer periphery of the core metal (1), and (3) is fluorine coated on the surface of the elastic body (2). It is a resin coating layer.

A feature of the present invention is that a fluororesin having a melt viscosity (MFR) of 1 to 3 and an elastic limit of 5% to 20% is adopted with respect to the physical properties of the fluororesin. Generally, the melt viscosity (MFR) of fluororesins
Regarding, regarding the fluororesin grade, there are a low melting type, a medium melting type, and a high melting type. (JIS
As a result of various tests, the inventors of the present invention have found that a low melting type fluororesin having a melt flow rate of 3 or less is superior in durability and stress crack resistance to other types. I found it. At that time, it was also found that if the elastic limit of the fluororesin is made the same as the elastic limit of the rubber elastic body of the inner layer, the durability and stress crack resistance are additively improved. That is, it has been found that the elastic limit needs to be in the range of 5% to 20%. After all, it is a low melting type with a melt flow rate of 3 or less and an elastic limit of 5% to 20%.
It was found that the above fluororesin is the most suitable. Then, these fluororesins are typically coated on the surface of the rubber elastic layer in the state of powder coating or dispersion. Of course, it is conceivable to coat the tube or the film-shaped fluororesin, but the coating method is superior in adhesiveness to the rubber elastic layer as compared with the case of coating the tube. Further, it has an advantage that the thickness can be finely adjusted and the productivity is good when the specifications of the thickness are different.
The coating thickness of the fluororesin layer at this time is not particularly limited, and may be appropriately selected from the range adopted in this field, that is, the range of 0.03 mm to 0.5 mm. Further, as a kind of the above-mentioned fluororesin to be coated, PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) which is superior in heat resistance, non-adhesiveness and low frictional property as compared with the conventionally adopted FEP. Alternatively, PTFE (polytetrafluoroethylene) is preferable. On the other hand, the rubber elastic layer (2) may be made of a usual rubber material such as silicone rubber,
The surface may be subjected to a primer treatment in advance.

The method for manufacturing the fixing heating roller of the present invention will be described below. In the present invention, a rubber elastic body is extruded on the outer periphery of the core metal using, for example, an extruder, and the surface of the elastic body layer is coated with a fluororesin by spraying or the like to form a fluororesin layer. Here, aluminum is the most suitable material for the core metal, and the size of the core metal itself has a length in the axial direction of 250 mm to 400 mm,
An outer diameter of about 6 mm to 30 mm is used. Roughening treatment such as sand blasting is performed on the outer periphery of the core metal in advance, and the primer NO. If an adhesive such as No. 23 (manufactured by Shin-Etsu Chemical Co., Ltd.) is applied, stable interfacial adhesion with the rubber elastic layer is secured during extrusion molding. Then, the interfacial adhesion is further enhanced by the subsequent vulcanization and heat treatment. This vulcanization treatment is not limited to once, and the secondary vulcanization treatment further improves the adhesive strength. The condition of the first vulcanization treatment is that the temperature is 150 ° C to 30 ° C.
The temperature is 0 ° C. and the treatment time is from 5 minutes to 60 minutes.
The conditions for secondary vulcanization are as follows: the temperature is 180 ° C to 220 ° C,
The processing time may be appropriately selected from the range of 4 hours or more.
Here, in order to smooth the surface of the rubber elastic layer, surface polishing is performed with a pressure roll. After that, the fluororesin is coated on the rubber elastic layer whose surface has been polished and dried, and finally, the fluororesin layer is baked at a temperature of about 200 ° C. to 250 ° C. to form a fixing heating roller to which the fluororesin is fixed. can get. In the present invention, the elastic limit and MFR follow the following measuring methods. Elastic limit: A tensile test is performed with a JIS K6251 dumbbell shape, and the change in tensile strength is read from the fracture chart to determine the elastic limit. MFR: JIS K7210 (test temperature 372 ° C, test load 5.00kgf)

[0009]

[Example] "Primer NO.23" was used as an adhesive on the outer circumference of an aluminum cored bar having an outer diameter of 28 mm and a length of 315 mm.
After coating (manufactured by Shin-Etsu Chemical Co., Ltd.), 100 parts of unvulcanized silicone rubber "KE951U" (manufactured by Shin-Etsu Chemical Co., Ltd.) was used as a vulcanizing agent, "C-23" (Shin-Etsu Chemical Co., Ltd. 2) and 3 parts of "C-3" (manufactured by Shin-Etsu Chemical Co., Ltd.) are added to the outer periphery of the core metal by an extrusion molding machine at a discharge rate of 300 g / min. Extrusion and coating (coating thickness: 5 mm). afterwards,
After vulcanization at 200 ° C for 60 minutes, the rotation speed is 2400 rp
The surface of the silicone rubber elastic layer is polished with a pressure roll having an outer diameter of 30 mm and an outer diameter of 30 mm so that the surface roughness Ra is 0.2 μm or less. Then, the surface of the elastic layer was subjected to a primer treatment (“TSE326” as a treating agent (manufactured by Toshiba Silicone Co., Ltd.), and further, the elastic limit was 10% and the melt viscosity (MFR) (melt flow rate) was 2%. A PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) resin dispersion of 0.0 is coated by spraying, and then 300 ° C to 35 ° C.
By firing at 0 ° C. for 20 minutes, a fixing heating roller provided with a fluororesin coating layer having a roll outer diameter of 33 mm was obtained. The thickness of the fluororesin coating layer of the fixing heating roller was 50 μm. A peripheral speed of 100 mm / sec was applied between the silicone rubber layer and the fluororesin coating layer of this roll under a system-distributed load with a total pressure of 120 N.
When a free running test was performed at 200 ° C and 1500 hours,
It was confirmed to have sufficient interface durability (adhesive strength 1000 gf / cm2). By the way, in the above example, the same is applied except that a usual fluororesin (a fluororesin PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) having an elastic limit of 3% and a melt viscosity (MFR) of 10 is coated and used. When the roll obtained was subjected to a rotation test from the above, not only the outermost fluororesin layer was partially peeled off, but also cracks were generated on the surface. The strength was only 700 gf / cm2.

According to the present invention, it is possible to provide a fixing heating roller which is excellent in durability with respect to the inner rubber elastic layer and stress crack resistance.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a fixing heating roll of the present invention.

2 is a cross-sectional view of FIG.

[Explanation of symbols]

1 core 2 rubber elastic body 3 Fluororesin coating layer

Continued front page    F term (reference) 2H033 AA23 BB03 BB05 BB13 BB14                       BB26                 3J103 AA02 AA13 AA21 AA51 BA01                       EA02 EA03 EA07 FA12 GA02                       GA57 HA04 HA43 HA54

Claims (2)

[Claims] 1. The elastic limit of 5% to 20% and melt viscosity (M
A heating roll for fixing, which is obtained by coating a fluororesin having an FR of 1 to 3 and then baking it. 2. The fluororesin is PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) or PTFE (polytetrafluoroethylene).
The fixing heating roll according to claim 1.