Stock material or miscellaneous articles – Composite – Of fluorinated addition polymer from unsaturated monomers
Reexamination Certificate
1998-12-16
2003-07-01
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Composite
Of fluorinated addition polymer from unsaturated monomers
C428S422000, C428S447000, C525S100000, C525S101000, C525S102000, C525S104000, C399S333000
Reexamination Certificate
active
06586100
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to polymeric compositions suitable for coating articles such as toner fusing members. More particularly, the invention relates to a fluorocarbon-silicone polymeric composition.
BACKGROUND OF THE INVENTION
In certain electrostatographic imaging and recording processes, for instance, in electrophotographic copying processes, an electrostatic latent image formed on a photoconductive surface is developed with a developer which is a mixture of carrier particles, e.g., magnetic particles, and a thermoplastic toner powder which is thereafter fused to a receiver such as a sheet of paper. The fusing member can be a roll, belt or any surface having a suitable shape for fixing thermoplastic toner powder images to a substrate. The fusing step commonly consists of passing the substrate, such as a sheet of paper on which toner powder is distributed in an image-wise pattern, through the nip of a pair of rolls, at least one of which is heated. Where the fusing member is a belt it is preferably a flexible endless belt which passes around a heated roller.
A persistent problem in this operation is that when the toner is heated during contact with the heated roll or belt it may adhere not only to the paper but also to the fusing member. Any toner remaining adhered to the member can cause a false offset image to appear on the next sheet and can also degrade the fusing member. Other potential problems are thermal degradation and abrasion of the member surface which results in an uneven surface and defective patterns in thermally fixed images.
Toner fusing rolls have a cylindrical core which may contain a heat source in its interior, and a resilient covering layer formed directly or indirectly on the surface of the core. Roll coverings are commonly fluorocarbon polymers or silicone polymers, such as poly(dimethylsiloxane) polymers, of low surface energy which minimizes adherence of toner to the roll. Frequently release oils composed of, for example, poly(dimethylsiloxanes), are also applied to the roll surface to prevent adherence of toner to the roll. Such release oils may interact with the roll surface upon repeated use and in time cause swelling, softening and degradation of the roll. Silicone rubber covering layers which are insufficiently resistant to release oils and cleaning solvents are also susceptible to delamination of the roll cover after repeated heating and cooling cycles.
Toner fusing belts are composed of a continuous flexible material having a smooth surface and superior resistance to heat. The belt substrate can be metallic or polymeric. The surface of the belt is composed of a thinly coated, low surface-energy polymer such as a fluorocarbon or a silicone-polymer.
Fusing members with a surface coating of a fluoroelastomer, especially vinylidene fluoride based fluoroelastomers, possess excellent heat, oil and chemical resistance as well as good fatigue and wear characteristics. However, fluoroelastomers with these excellent chemical and mechanical properties have a propensity to interact with toners, especially in comparison with polydimethylsiloxane surfaces, causing premature offset.
U.S. Pat. No. 4,264,181 discloses fusing members coated with a metal-filled elastomer surface obtained by nucleophilic-addition curing of a mixture of a metal filler and a vinylidene fluoride-hexafluoropropylene copolymer. Mixtures of the fluoroelastomers with silicone rubbers were mentioned (column 8, lines 26-29) but no specific examples of suitable silicones are taught. The surface coatings disclosed are used in conjunction with functionally substituted polymeric release agents capable of interacting with the metal component.
U.S. Pat. No. 4,853,737 (incorporated herein by reference) discloses a roll useful in electrostatography having an outer layer comprising cured fluoroelastomers containing pendant polydiorgano-siloxane segments that are covalently bound to the backbone of the fluoroelastomer. Unlike the current invention, the silicon content described in this patent must be kept very low in practice to avoid incompatibility.
U.S. Pat. No. 5,141,788; U.S. Pat. No. 5,166,031; and U.S. Pat. No. 5,695,878 disclose a fuser member comprising a supporting substrate having an outer layer of a volume grafted elastomer which is a substantially uniform integral interpenetrating network (hereinafter IPN) of a hybrid composition of a fluoroelastomer and a polyorganosiloxane, where said volume graft has been formed by dehydrofluorination of said fluoroelastomer by a nucleophilic dehydrofluorinating agent, followed by addition polymerization by the addition of an alkene or alkyne functionally terminated polyorganosiloxane and a polymerization initiator. The disadvantage of this is that it usually involves at least two extra reaction steps to produce higher silicone contents without phase separation. Also the resulting network structure forms a higher silicone concentration on the surface through stratification and as such has poorer wear resistance.
U.S. Pat. No. 5,534,347 discloses toner fusing rolls having an oil barrier layer composed of a substrate coated with a fluorocarbon-silicone polymeric composition which is obtained by concurrently curing a fluorocarbon copolymer, a nucleophilic fluorocarbon-curing agent and a heat curable polyfuctional poly (C
1-6
alkyl)arylsiloxane polymer. This patent does not describe a release layer as the surface energy of the resulting material was too high.
Similarly, U.S. Pat. No. 5,582,917 discloses toner fusing members having a surface layer comprising a substrate coated with a fluorocarbon-silicone polymeric composition obtained by concurrently curing a fluorocarbon copolymer, a nucleophilic fluorocarbon curing agent and a heat curable polyfunctional polymethylsiloxane polymer. The disadvantage of these last two patents is in the production methods needed to manufacture these materials. In these patents, mechanical mixing is described as being necessary to eliminate phase separation of the silicone from the fluorocarbon phases. In general the two phases are forced into intimate contact with the possibility of some measure of reaction within both of the phases. This reaction effectively eliminated the tendency for bulk phase separation. However the processability, if practiced as described, would decrease the shelf life of the dry material.
U.S. patent application Ser. No. 09/156,831 describes solution blending silicones with fluorocarbon elastomers to obtain good release coatings. These coatings have the advantage of fluorocarbon strength and the good release of silicones. Unfortunately only moderate amounts of silicone can be combined with the fluorocarbon elastomer before large scale phase incompatability occurs. Such incompatability negatively impacts image and release qualities.
The materials in the '347 and '917 patents above are suitable for most applications; however, as the trend in electrophotographic processes is to increase the process speed and achieve longer component life, those materials are no longer acceptable. Thus, there is still a need for manufacturable coating compositions based on fluorocarbon copolymers which resist abrasion, interact minimally with toners and resist offset while retaining the advantageous mechanical and chemical properties characteristic of fluoroelastomers. This requires materials having higher silicone content for better intrinsic release properties, and fewer surface defects for toner attachment. In addition, there is a need to control the coating surface properties without recourse to additional processing steps such as grinding or polishing.
SUMMARY OF THE INVENTION
The present invention relates to a fuser member polymeric composition containing a fluorocarbon-silicone interpenetrating network, comprising:
a) a first polymer comprising a fluorocarbon elastomer;
b) a second polymer selected from a curable polyfunctional poly(C
(1-6)
alkyl)siloxane polymer; a curable polyfunctional poly(C
(1-6)
alkyl)arylsiloxane polymer; and combinations thereof;
c) a functi
Chen Jiann H.
Davis Stephen V.
Pickering Jerry A.
Chen Vivian
NexPress Solutions LLC
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