Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-06-30
2002-08-06
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S506000
Reexamination Certificate
active
06429249
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to compositions containing a fluorocarbon thermoplastic random copolymer. More particularly, the invention relates to compositions containing a fluorocarbon thermoplastic random copolymer, zinc oxide, and an aminosiloxane. Such compositions are useful as coatings, sheets, or films where high temperature resistance is required.
BACKGROUND OF THE INVENTION
Fluororesins, including both fluorocarbon elastomers and fluorocarbon thermoplastics, are widely used in the form of sheet, film, coatings and laminates in various fields due to their characteristic properties such as good heat resistance, good chemical resistance and good weather resistance. These materials find applications as gaskets and seals in automotive fuel delivery, engine, and powertrain systems, tank and pipe liners, release layers on compression molds, layers on electrophotographic toner fuser rollers or belts, valve stem and rotating shaft sealant coatings, roller and bearing coatings, and sealants for porous materials such as ceramics and fabric, for example. In addition to their characteristic resistance to heat, chemicals, and weather, and depending upon the particular application, these fluororesin compositions may also need to provide appropriate frictional characteristics, abrasion and wear resistance, flexibility, processability, and adhesion to a particular substrate.
Polyfluorocarbon elastomers, such as vinylidene fluoride-hexafluoropropylene copolymers, are tough, wear resistant and flexible elastomers that have excellent high temperature resistance, but relatively high surface energies, which compromise applications where release properties are critical, for example as release layers on compression molds or outer layers on electrophotographic toner fuser members.
Fluorocarbon resins like polytetrafluoroethylene (PTFE) or fluorinated ethylenepropylene (FEP) are fluorocarbon thermoplastics which have excellent release characteristics due to very low surface energy. Fluorocarbon thermoplastic resins are, however, less flexible and elastic than fluorocarbon elastomers and often require high temperature curing for long time periods to sinter the polymer into a continuous and useful layer or sheet.
Both fluorocarbon elastomers and fluorocarbon thermoplastics have been used to prepare high temperature resistant surfaces. For example, U.S. Pat. No. 4,999,221 describes a process for powder coating a substrate with a fluoroplastic material to provide a heat resistant surface layer. U.S. Pat. Nos. 5,919,886 and 6,020,450 describe a room temperature curable fluoropolymer composition containing an organosilicon compound and a condensation accelerator having improved heat resistance and weatherability.
U.S. Pat. Nos. 5,948,479 and 6,068,931 describe composite materials for self-lubricating slide bearings containing a fluorothermoplastic composite overlayer on a porous metal bearing.
Fluororesin-containing compositions have also been successfully employed in various electrostatographic applications. For example, U.S. Pat. Nos. 4,568,275 and 5,599,631 disclose a fuser roll having a layer of fluorocarbon elastomer and a fluorinated resin powder. However, the fluorocarbon resin tends to phase separate from the fluorocarbon elastomer thereby diminishing performance.
U.S. Pat. No. 4,853,737 discloses a fuser roll having an outer layer comprising cured fluorocarbon elastomers containing pendant amine functional polydimethylsiloxane that are covalently bonded to the backbone of the fluorocarbon elastomer. However, the amine functional polydimethylsiloxane tends to phase separate from the fluorocarbon elastomer.
U.S. Pat. No. 5,582,917 discloses a fuser roll having a surface layer comprising a fluorocarbon-silicone polymeric composition obtained by heating a fluorocarbon elastomer with a fluorocarbon elastomer curing agent in the presence of a curable polyfunctional poly(C1-6 alkyl) siloxane polymer. However, the resulting interpenetrating network (IPN) has relatively high coefficient of friction and relatively low mechanical strength. After a period of use, the release property of the roller degrades and paper jams begin to occur.
U.S. Pat. No. 5,547,759 discloses a fuser roll having a release coating layer comprising an outermost layer of fluorocarbon resin uniquely bonded to a fluoroelastomer layer by means of a fluoropolymer containing a polyamide-imide primer layer. Although the release coating layer has relatively low surface energy and good mechanical strength, the release coating layer lacks flexibility and elastic properties and can not produce high quality of images. In addition, sintering the fluorocarbon resin layer is usually accomplished by heating the coated fuser member to temperatures of approximately 350° C. to 400° C. Such high temperatures can have a detrimental effect on the underlying base cushion layer which normally comprises a silicone rubber layer. It would be desirable to provide a fuser member with an overcoat layer comprising a fluorocarbon resin layer without depolymerizing the silicone base cushion layer on heating.
U.S. Pat. No. 5,595,823 discloses toner fusing members which have a substrate coated with a fluorocarbon random copolymer containing aluminum oxide. Although these toner fusing members have proved effective and have desirable thermal conductivity, they have a problem in that there can be toner contamination. The advantage of using the cured fluorocarbon thermoplastic random copolymer compositions is that they are effective for use with toner release agents which typically include silicone.
U.S. Pat. No. 6,035,780 describes a process to prepare a compatibilized blend of a fluoroelastomer and a polysiloxane useful for electrostatographic and liquid ink printing machine applications. The compatible blend is reportedly useful as a component of long-life fuser rolls, backing rolls, transfer and transfuse belts and rolls and bias charging and bias transfer rolls.
As evidenced by the above description, fluororesin compositions have been widely utilized in a variety of critical applications requiring resistance to severe or aggressive environments, abrasion and wear resistance, surface lubricity, release properties, and processability. However, it has been extremely difficult to provide a fluororesin composition which simultaneously provides most or all of these characteristics. It is toward a solution to this problem that the present invention is directed.
SUMMARY OF THE INVENTION
The present invention provides a composition that contains a fluorocarbon thermoplastic random copolymer that is easily processed into a coating or sheet having improved release properties, surface lubricity, and mechanical strength.
The present invention discloses a composition comprising a fluorocarbon thermoplastic random copolymer, a curing agent having a bisphenol residue, a particulate filler containing zinc oxide, and an aminosiloxane, the cured fluorocarbon thermoplastic random copolymer having subunits of:
—(CH
2
CF
2
)x—, —CF
2
CF(CF
3
)y—, and —(CF
2
CF
2
)z—,
wherein
x is from 1 to 50 or 60 to 80 mole percent,
y is from 10 to 90 mole percent,
z is from 10 to 90 mole percent,
x+y+z equals 100 mole percent.
The aminosiloxane is an amino functional polydimethyl siloxane copolymer comprising aminofunctional units selected from the group consisting of (aminoethylaminopropyl) methyl, (aminopropyl) methyl and (aminopropyl) dimethyl.
Optionally, the composition of the invention may further contain a fluorinated resin, the fluorinated resin is selected from the group of polytetrafluoroethylene or fluoroethylenepropylene having a number average molecular weight of between 50,000 and 50,000,000.
As will be demonstrated through examples, compositions comprising unfilled fluorocarbon thermoplastic random copolymer have poor mechanical strength and release properties. However, it has been surprisingly found in the present invention that the addition of zinc oxide filler and an aminosiloxane polymer to a fluorocarbon thermoplastic random copolymer provides a co
Anderson Charles C.
Chen Jiann H.
Lancaster Robert A.
Pavlisko Joseph A.
Kessler Lawrence P.
Nexpress Solutions LLC
Sanders Kriellion A.
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