Stock material or miscellaneous articles – Composite – Of fluorinated addition polymer from unsaturated monomers
Reexamination Certificate
2000-11-15
2003-07-29
Zacharia, Ramsey (Department: 1773)
Stock material or miscellaneous articles
Composite
Of fluorinated addition polymer from unsaturated monomers
C428S422000, C428S447000, C428S448000, C399S320000, C427S208200, C427S336000, C427S384000, C427S402000
Reexamination Certificate
active
06599628
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of bonding a fluoro-containing compound to a silicone rubber substrate with a primer composition comprised of an organic based titanate compound and an alkoxysilane compound, as well as to a bonded composite of the foregoing materials.
2. Discussion of Related Art
In the art of electrophotography/electrostatography, heat-softenable toners are widely used in imaging methods wherein electrically charged toner is deposited imagewise on a dielectric or photoconductive element bearing an electrostatic latent image. Following development of the latent image with the toner, the toner is transferred in image-configuration to a surface of an image receiving medium such as, for example, paper or transparent film. The toner image is then fixed in place upon the medium to yield the final image.
A typical method of fixing toner in place on the medium involves applying heat to the toner once it is on the image receiving medium surface to soften it and then allowing or causing the toner to cool. One such fusing method comprises passing the toner-bearing medium sheet through the nip formed by a pair of opposing rolls, at least one of which (usually referred to as a fuser member or roll) is heated and contacts the toner-bearing surface of the receiver sheet in order to heat and soften the toner. The other roll (usually referred to as a pressure member or roll) serves to press the receiver sheet into contact with the fuser roll. The fuser member and pressure member may also take the form of a flat plate or belt.
A fuser member can comprise, for example, a rigid core covered with a resilient material, particularly a silicone rubber. In addition, in electrophotographic fuser systems, fuser members are commonly made with an overcoat layer of a polyfluorocarbon resin or polyfluorocarbon elastomer. Fluorocarbon resins like polytetrafluoroethylene (PTFE) or a copolymer of PTFE and perfluoroalkylvinylether, or fluorinated ethylenpropylene have excellent release characteristics due to very low surface energies, high temperature resistance, and excellent chemical resistance. Polyfluorocarbon elastomers, such as vinylene fluoride-hexafluoropropylene copolymers, are tough, flexible elastomers that have excellent high temperature resistance.
However, due to the low surface energies of the silicone rubber and the fluoro-containing material overcoat, it is very difficult to obtain a good bond between these layers. This is a particular problem in the area of fuser members for electrophotographic and electrostatographic devices where strong adhesion between a silicone rubber and a fluoroelastomer topcoat is necessary for long-term, reliable operation.
U.S. Pat. No. 5,595,823 describes a fuser member useful for heat-fixing an electrographic toner to a substrate. The fuser member has a core and an outer layer. The outer layer includes a cured fluorocarbon random copolymer and particulate filler of aluminum oxide and a material selected from the group consisting of alkali metal oxides, alkali metal hydroxides, and combinations thereof. In a specific embodiment, a silicone rubber layer is coated upon a stainless steel substrate core, the core being primed with a uniform coat of a metal alkoxide type primer, Dow 1200 Prime Coat primer, marketed by Dow Corning Corporation of Midland, Mich., which is described to contain light aliphatic petroleum naptha (85 weight percent), tetra (2-methoxyethoxy)-silane (5 weight percent), tetrapropyl orthosilicate (5 weight percent), and tetrabutyl titanate (5 weight percent).
U.S. Pat. No. 5,599,631 describes a fuser member having as its outermost layer a substantially homogeneous composite comprising: a) a continuous phase of a fluorocarbon elastomer selected from vinylidene fluoride based fluoroelastomers containing hexafluoropropylene and terpolymers of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene; and b) a discontinuous phase of a fluorinated resin having a molecular weight between about 4,000 and 25,000. Again, it is indicated that a silicone rubber intermediate layer may be applied to a core primed with Dow 1200 primer.
U.S. Pat. No. 5,973,067 describes a primer composition for promoting the adhesion of thermosetting rubbers to substrates having exceptionally inert surfaces, such a nickel, stainless steel and organic resins. The composition comprises: (A) 100 parts, by weight, of an organosilicon compound selected from the group consisting of (1) alkenyltrialkoxysilane and (2) mild hydrolyzates of (1); (B) 0.01-200 parts, by weight, of a platinum compound; (C) 0.1-100 parts by weight of an organic titanic acid ester; and optionally (D) a solvent.
The foregoing patents thus describe primer compositions intended to assist in bonding a silicone rubber to a metal surface.
U.S. Pat. No. 5,238,708 describes a primer composition, and a method for its use to improve adhesion between a silicone substrate and a subsequently applied paint film. The primer composition consists essentially of a mixture of an alkoxysilane, an organotitanate and a tin salt of a carboxylic acid, each component being present in a specific critical molar proportion. Although this patent mentions the use of the primer to enhance adhesion between a silicone rubber and a paint overcoat, it does not indicate that the paint should contain a fluoro-containing compound. Further, it is not taught that the solvent of the primer is a solvent that swells the silicone rubber.
U.S. Pat. No. 3,671,483 discovered that a solution containing a tetraalkyltitanate and a particular silane which has at least one group of the formula CH
2
CH
2
—Si(OOCCH
3
)
3
in its molecule is useful as a primer in adhering a silicone rubber to epoxy and polyurethane.
U.S. Pat. No. 4,681,636 discloses a primer composition particularly suitable for bonding fluorosilicone rubber to a substrate. This primer comprises a solution of a t-butyl peroxy-functional silane, a reactive organosilicon compound having at least two alkoxy groups and an organotitanate ester. U.S. Pat. No. 4,749,741 describes primers suitable for promoting adhesion between silicone rubber and plastics or metals. These primers comprise a solution of an unsaturated organotitanate ester and either an organosilicon compound having at least two alkoxy groups or an organohydrogensiloxane (or silane).
Until now, primers used in bonding a overcoat to a silicone rubber still suffer from adhesion failures between the layers during operation as fuser members. What is still desired, then, is development of a primer that can achieve enhanced bonding strength between a fluoro-containing compound overcoat and a silicone rubber substrate.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to develop a composite of a silicone rubber and a fluoro-containing material in which the bond between the layers is very strong. It is a still further object of the present invention to develop a fuser member containing such composite member for a copying device.
It is a further object of the present invention to develop a primer composition to achieve the desired enhanced bond strength between a silicone rubber and a fluoro-containing material.
These and other objects of the present invention are achieved herein by a composite structure comprising a layer of silicone rubber that is bonded to an overlying layer containing at least one fluoro-containing compound, the bond effected via a primer composition on a surface of the layer of silicone rubber, wherein the primer composition is comprised of at least an organic titanate and an alkoxysilane.
In a further embodiment of the invention, the invention pertains to a fuser member comprising a core overcoated with a first layer of silicone rubber that is bonded to an overlying layer containing at least one fluoro-containing compound, the bond effected via a primer composition on a surface of the layer of silicone rubber, wherein the primer composition is comprised of at least an organic titanate and an alkoxysilane.
In a furt
Finsterwalder Robert N.
Russell, Jr. James G.
Schmitt Sandra L.
Oliff & Berridg,e PLC
Xerox Corporation
Zacharia Ramsey
LandOfFree
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