U.S. patent application number 09/772620 was filed with the patent office on 2002-08-01 for interpenetrating polymer network of polytetra fluoroethylene and silicone elastomer for use in electrophotographic fusing applications.
Invention is credited to Badesha, Santokh S., Gervasi, David J., Heeks, George J., Henry, Arnold W., Riehle, George A..
Application Number | 20020102410 09/772620 |
Document ID | / |
Family ID | 25095672 |
Filed Date | 2002-08-01 |
United States Patent
Application |
20020102410 |
Kind Code |
A1 |
Gervasi, David J. ; et
al. |
August 1, 2002 |
INTERPENETRATING POLYMER NETWORK OF POLYTETRA FLUOROETHYLENE AND
SILICONE ELASTOMER FOR USE IN ELECTROPHOTOGRAPHIC FUSING
APPLICATIONS
Abstract
The present invention relates to electrostatographic fuser
system members such as fuser rolls or belts having an outer surface
layer comprising an interpenetrating polymer network comprising
polytetrafluoroethylene and a cured polysiloxane elastomer, and a
method for making such fuser system members.
Inventors: |
Gervasi, David J.; (West
Henrietta, NY) ; Riehle, George A.; (Webster, NY)
; Heeks, George J.; (Rochester, NY) ; Henry,
Arnold W.; (Pittsford, NY) ; Badesha, Santokh S.;
(Pittsford, NY) |
Correspondence
Address: |
Michael J. Tully
Perman & Green, LLP
425 Post Road
Fairfield
CT
06430
US
|
Family ID: |
25095672 |
Appl. No.: |
09/772620 |
Filed: |
January 30, 2001 |
Current U.S.
Class: |
428/421 ;
264/204; 428/447 |
Current CPC
Class: |
Y10T 428/31663 20150401;
G03G 15/2057 20130101; Y10T 428/3154 20150401 |
Class at
Publication: |
428/421 ;
428/447; 264/204; 430/124 |
International
Class: |
D01F 001/00; B32B
027/00; B32B 009/04 |
Claims
What is claimed is:
1. A fuser system member comprising a supporting substrate and an
outer surface layer, said outer surface layer comprising an
interpenetrating polymer network comprising polytetrafluoroethylene
and a cured polysiloxane elastomer.
2. A process for manufacturing a fuser system member comprising: a)
forming an intimate blend of a major amount of an unsintered and
unfibrillated particulate polytetrafluoroethylene resin dispersion,
a hydrocarbon liquid, a curable polysiloxane and a curing system
for said polysiloxane; b) forming said blend into an extrudable
shape; c) biaxially extruding said blend through a die into a
shaped product having a randomly fibrillated structure; d)
evaporating said hydrocarbon liquid; e) subjecting said shaped
product to curing conditions to cure said polysiloxane; and f)
applying said shaped product to a supporting substrate to form a
fuser member having an outer surface comprising said shaped
product.
3. The process of claim 2 wherein said step (f) is conducted prior
to step (e).
4. The process of claim 2 wherein said shaped product comprises a
film.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to an interpenetrating polymer network
for use as release layer coatings for fuser and transport belts
used in electrostatographic printing apparati.
[0003] 2. Description of Related Art
[0004] In a typical electrostatographic reproducing apparatus, a
light image of an original to be copied is recorded in the form of
an electrostatic latent image upon a photosensitive member and the
latent image is subsequently rendered visible by the application of
electroscopic thermoplastic resin and pigment particles which are
commonly referred to as toner. The visible toner image is then in a
loose powdered form and can be easily disturbed or destroyed. The
toner image is usually fixed or fused upon a support which may be
the photosensitive member itself or other support sheet such as
plain paper.
[0005] The use of thermal energy for fixing toner images onto a
support member is well known. To fuse electroscopic toner material
onto a support surface permanently by heat, it is usually necessary
to elevate the temperature of the toner material to a point at
which the constituents of the toner material coalesce and become
tacky. This heating causes the toner to flow to some extent into
the fibers or pores of the support member. Thereafter, as the toner
material cools, solidification of the toner causes the toner to be
firmly bonded to the support.
[0006] Typically, the thermoplastic resin particles are fused to
the substrate by heating to a temperature of between about
90.degree. C. to about 200.degree. C. or higher depending upon the
softening range of the particular resin used in the toner. It is
undesirable, however, to increase the temperature of the substrate
substantially higher than about 250.degree. C. because of the
tendency of the substrate to discolor at such elevated
temperatures, particularly when the substrate is paper.
[0007] Several approaches to thermal fusing of electroscopic toner
images have been described. These methods include providing the
application of heat and pressure substantially concurrently by
various means, such as a roll pair maintained in pressure contact,
a belt member in pressure contact with a roll, and the like. Heat
may be applied by heating one or both of the rolls, plate members
or belt members. The fusing of the toner particles takes place when
the proper combination of heat, pressure and contact time are
provided. The balancing of these parameters to bring about the
fusing of the toner particles is well known in the art, and can be
adjusted to suit particular machines or process conditions.
[0008] During operation of a fusing system in which heat is applied
to cause thermal fusing of the toner particles onto a support, both
the toner image and the support are passed through a nip formed
between the roll pair or plate or belt members. The concurrent
transfer of heat and the application of pressure in the nip affects
the fusing of the toner image onto the support. It is important in
the fusing process that no offset of the toner particles from the
support to the fuser member take place during normal operations.
Toner particles that offset onto the fuser member may subsequently
transfer to other parts of the machine or onto the support in
subsequent copying cycles, thus increasing the background or
interfering with the material being copied there. The referred to
"hot offset" occurs when the temperature of the toner is increased
to a point where the toner particles liquefy and a splitting of the
molten toner takes place during the fusing operation with a portion
remaining on the fuser member. The hot offset temperature or
degradation of the hot offset temperature is a measure of the
release property of the fuser roll, and accordingly it is desired
to provide a fusing surface which has a low surface energy to
provide the necessary release. To ensure and maintain good release
properties of the fuser roll, it has become customary to apply
release agents to the fuser roll during the fusing operation.
Typically, these materials are applied as thin films of, for
example, silicone oils to prevent toner offset.
[0009] One of the earliest and most successful fusing systems
involved the use of silicone elastomer fusing surfaces, such as a
roll with a silicone oil release agent which could be delivered to
the fuser roll by a silicone elastomer donor roll. The silicone
elastomers and silicone oil release agents used in such systems are
described in numerous patents and fairly collectively illustrated
in U.S. Pat. No. 4,777,087 to Heeks et al.
[0010] While highly successful in providing a fusing surface with a
very low surface energy to provide excellent release properties to
ensure that the toner is completely released from the fuser roll
during the fusing operation, these systems suffer from a
significant deterioration in physical properties over time in a
fusing environment. In particular, the silicone oil release agent
tends to penetrate the surface of the silicone elastomer fuser
members resulting in swelling of the body of the elastomer causing
major mechanical failure including debonding of the elastomer from
the substrate, softening and reduced toughness of the elastomer
causing it to chunk out and crumble, contaminating the machine and
providing non-uniform delivery of release agent. Furthermore, as
described in U.S. Pat. No. 4,777,087, additional deterioration of
physical properties of silicone elastomers results from the
oxidative crosslinking, particularly of a fuser roll at elevated
temperatures.
[0011] A more recent development in fusing systems involves the use
of fluoroelastomer as fuser members which have a surface with a
metal containing filler, which interact with polymeric release
agents having functional groups, which interact with the metal
containing filler in the fluoroelastomer surface. Such fusing
systems, fusing members and release agents, are described in U.S.
Pat. No. 4,264,181 to Lentz et al. U.S. Pat. No. 4,257,699 to Lentz
and U.S. Pat. No. 4,272,179 to Seanor. Typically, the
fluoroelastomers used are (1) copolymers of vinylidenefluoride,
hexafluoropropylene, and (2) terpolymer or vinylidenefluororide,
hexafluoropropylene and tetrafluoroethylene. Commercially available
materials include: Viton.TM. E430, Viton GF and other Viton
designations as trademarks of E.I. Dupont deNemours, Inc. as well
as the Fluorol.TM. materials of 3M Company. The preferred curing
system for these materials is a nucleophilic system with a
bisphenol crosslinking agent to generate a covalently crosslinked
network polymer formed by the application of heat following base
dehydrofluorination of the copolymer. Exemplary of such fuser
member is an aluminum base member with a
poly(vinyldenefluoride-hexafluoropropylene) copolymer cured with a
bisphenol curing agent having lead oxide filler dispersed therein
and utilizing a mercapto functional polyorganosiloxane oil as a
release agent. In those fusing processes, the polymeric release
agents have functional groups (also designated as chemically
reactive functional groups) which interact with the metal
containing filler dispersed in the elastomer or resinous material
of the fuser member surface to form a thermally stable film which
releases thermoplastic resin toner and which prevents the
thermoplastic resin toner from contacting the elastomer material
itself. The metal oxide, metal salt, metal alloy or other suitable
metal compound filler dispersed in the elastomer or resin upon the
fuser member surface interacts with the functional groups of the
polymeric release agent. Preferably, the metal containing filler
materials do not cause degradation or have any adverse effect upon
the polymer release agent having functional groups. Because of this
reaction between the elastomer having a metal containing filler and
the polymeric release agent having functional groups, excellent
release and the production of high quality copies are obtained even
at high rates of speed of electrostatographic reproducing
machines.
[0012] While these fluoroelastomers have excellent mechanical and
physical properties in that they have a long wearing life thereby
maintaining toughness and strength over time in a fusing
environment, they have to be used with expensive functional release
agents and must contain expensive interactive metal-containing
fillers.
[0013] More recently, advances have been made in attempts to
incorporate the property benefits of both the fluoroelastomers and
the silicone elastomers into fusing system surfaces. For example,
U.S. Pat. No. 6,035,780 discloses compatibilized blends of
fluoroelastomer and polysiloxane elastomer which can be fabricated
into films and surfaces having good release and low surface energy
properties.
[0014] U.S. Pat. No. 5,141,788 to Badesha et al. describes a fuser
member comprising a supporting substrate having an outer layer of a
cured fluoroelastomer having a thin surface layer of a
polyorganosiloxane having been grafted to the surface of the cured
fluoroelastomer in the presence of a dehydrofluorinating agent for
the fluoroelastomer and having the active functionality from a
hydrogen, hydroxy, alkoxy, amino, epoxy, vinyl acrylic, or mercapto
group.
[0015] U.S. Pat. No. 5,166,031 to Badesha et al. is directed to a
fuser member comprising a supporting substrate having an outer
layer of a volume grafted elastomer which is a substantially
uniform integral interpenetrating network of a hybrid composition
of a fluoroelastomer and a polyorganosiloxane which is formed by
dehydrofluorination of the 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.
[0016] Polytetrafluoroethylene is a well known material which has
superior low surface energy and release properties and is used
primarily as a coating for cooking surfaces, such as frypans,
baking pans and the like. However, this material is not elastomeric
in nature and is in fact a relatively brittle, difficult-to-process
and solvent insoluble thermoplastic which renders it unsuitable per
se for use in fabricating fuser release surfaces.
SUMMARY OF THE INVENTION
[0017] The present invention provides a fuser system member
comprising a supporting substrate and an outer surface layer, said
outer surface layer comprising an interpenetrating polymer network
comprising polytetrafluoroethylene (PTFE) and a cured polysiloxane
elastomer.
[0018] The invention also provides a process for manufacturing a
fuser system member comprising (a) forming an intimate blend of a
major amount of an unsintered and unfibrillated particulate
polytetrafluoroethylene dispersion resin, a hydrocarbon liquid, a
curable polysiloxane and a curing system for said polysiloxane; (b)
forming said blend into an extrudable shape; (c) biaxially
extruding said blend through a die into a shaped product having a
randomly fibrillated structure; (d) evaporating said hydrocarbon
liquid; (e) subjecting said shaped product to curing conditions to
cure said polysiloxane; and (f) applying said shaped product to a
supporting substrate to form a fuser member having an outer surface
comprising said shaped product.
[0019] The fuser system surfaces prepared in accordance with the
invention combine the fusing advantages of fluoropolymer and
silicone elastomer fusing surfaces. The fusing surfaces possess the
conformability and release characteristics that are required of
fusing substrates while simultaneously possessing the strength and
durability of the PTFE. The silicone component of the formulation
contributes to the conformance and flex of the material while the
PTFE provides film strength and non-swell characteristics. The
composite IPN surface also provides a more limited swell in common
fusing fluids, which is an advantage over materials composed of
silicone only.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The polysiloxane component which may be used as a component
of the IPN composition of this invention is one or a mixture of
curable polysiloxanes selected from dialkylsiloxanes wherein the
alkyl groups are independently selected and contain from 1 to about
20 carbon atoms, alkylarylsiloxanes wherein the alkyl groups
contain from 1 to about 20 carbon atoms and the aryl group contains
from 6 to about 20 carbon atoms, diarylsiloxanes wherein the aryl
groups are independently selected and contain from 6 to about 20
carbon atoms, substituted alkyl groups such as chloropropyl,
trifluoropropyl, mecaptopropyl, carboxypropyl, aminopropyl and
cyanopropyl, substituted alkenyl groups such as vinyl, propenyl,
chlorovinyl and bromopropenyl and mixtures thereof. Examples of
commercially available copolymeric silxane materials include Dow
Corning Silastic.TM. 590 series, 9280 series, 9390 series, 3100
series, MOX4 series, Q-7 series, Sylgard.TM. series, 730 series, GP
series, NPC series, LCS series, LT series and TR series; General
Electric SE series, including SE-33, FSE, 2300, 2500, 2600 and 2700
and Wacker silicones Elastosil.TM. LR, Electroguard.TM. series,
c-series, SWS series, S-series, T-series and V-series.
[0021] Preferred polysiloxanes are those containing free radical
reactive functional groups containing at least one unsaturated
carbon to carbon double bond groups such as vinyl or alkenyl
groups.
[0022] Crosslinking agents include any of the known free radical
initiator compounds such as peroxides, for example, hydrogen
peroxide, alkyl or aryl peroxide and the like; persulfates, azo
compounds, for example AIBN, and like compounds as well as mixtures
thereof, which initiator compounds are present in amounts of from
about 0. 1 to about 10 wt % of the curable polysiloxane.
[0023] Alternatively, the polysiloxane may be a condensation
curable polysiloxane based on a polydiorganosiloxane having
terminal hydrolyzable groups, e.g., hydroxy or alkoxy and a
catalyst which promotes condensation curing, such as the materials
disclosed in U.S. Pat. No. 3,888,815, the complete disclosure of
which patent is incorporated herein by reference.
[0024] In another embodiment, the polysiloxane may be a
hydrolylicatly condensable silane having the formula
Y--Si--(OX).sub.3 where each X is independently selected from the
group consisting of hydrogen, alkyl radicals, hydroxyalkyl
radicals, and hydroxyalkoxyalkyl radicals, and Y is an alkyl
radical, OX where X is as previously defined, or an amino or
substituted amino radical. These materials used to form an IPN
network are more completely disclosed in U.S. Pat. No. 4,250,074,
the complete disclosure of which is incorporated herein by
reference.
[0025] Curable blends of two polysiloxanes such as a polysiloxane
containing free radical reactive functional groups and a second
polysiloxane may also be used, such as disclosed in U.S. Pat. No.
6,035,780, the complete disclosure of which is incorporated herein
by reference.
[0026] The polytetrafluoroethylen (PTFE) component of the
composition may comprise unsintered and unfibrillated resin in the
form of a dispersion such as available from Dupont under the trade
designation TEFLON.RTM. 6 and 6C and from Imperial Chemical
industries under the names FLUON.RTM. CD1, CD123 or CD-525.
[0027] Preferably, the composition contains the PTFE as the major
polymeric component, i.e., it contains at least 50 wt % of PTFE
based on the polymer content. Preferably the polysiloxane
constitutes from about 1 to 30 wt % of the polymer content of the
composition.
[0028] The composition may also contain from about 1520 volume
percent of one or more filler materials which impart additional
desired physical properties to the fuser surface, such as thermal
conductivity, increased durometer harness and electrical
conductivity. Suitable fillers include carbon black, antimony
oxide, antimony doped tin oxide, iron oxide, aluminum oxide, silica
and like materials.
[0029] The substrate for the fuser member of the fuser system
assembly may be a roll, belt, flat surface or other suitable shapes
used in the fixing of thermoplastic toner images to a suitable
substrate. The substrate may take the form of a fuser member, as
pressure member or a release agent donor member, and may be
composed of metal or a flexible belt material derived from a
thermoplastic, thermoset or elastomeric resin such as polyamide or
polyimide resins and cured polysiloxane or diolefin elastomers. A
film of the IPN composition may be laminated to or wrapped around
the substrate using suitable adhesives which will form a firm bond
between the IPN film and the metal or resinous substrate. Suitable
adhesives include silicone elastomers, fluoroelastomers, epoxy
resins, acrylic resins and the like. Alternatively, where the
substrate is in the form of a roll, the IPN composition may be
extruded or molded into the shape of a cylindrical collar which is
adapted to fit snugly around the cylindrical base, with or without
the use of an intermediate adhesive.
[0030] The thickness of the IPN outer surface of film of the fuser
member may range from about --5-- to --60---micrometer, more
preferably from about --15-- to -25--micrometers.
[0031] The outer surface of the fuser member is prepared by first
forming an intimate mixture of a PTFE polymer dispersion and a
minor amount of the curable polysiloxane polymer. Preferably minor
amounts of a suitable organic liquid such as a C.sub.4-C.sub.20
alkane or kerosene are included in the mixture to facilitate
blending and act as a lubricant. A crosslinking agent and
crosslinking catalyst is also added to the mixtures.
[0032] In the second step of the process of this invention, the
blend is compacted into a preform shape adapted to the
configuration necessary for the process of biaxial fibrillation as
described in U.S. Pat. No. 3,315,020.
[0033] Is the third step of the process of this invention, paste
extrusion of the preformed blend is carried out in the known manner
of biaxial fibrillation as described in U.S. Pat. No.
3,315,020.
[0034] In the fourth step of the process of this invention, the
hydrocarbon liquid contained in the blend is evaporated, and
simultaneously therewith or later the catalyst for the siloxane
crosslinking reaction is activated thereby generating a cured
silicone elastomer and polytetrafluoroethylene
semi-interpenetrating polymer network in the form of the biaxially
fibrillated extrudate.
[0035] Where films are prepared, the resulting extrudate is
preferably calendared by known methods to produce a film having a
thickness in the range of about --50-- to about
-125-micrometers.
[0036] Films of molded cylindrical shapes may then be applied to
and adhered to supporting substrates to form the fuser system
members of the present invention. The curing step described above
may be carried out after application of the outer surface release
layer to the substrate.
[0037] Films and other shapes made in accordance with this
invention may be generally prepared by the process disclosed in
U.S. Pat. No. 4,945,125, the complete disclosure of which patent is
incorporated herein by reference.
* * * * *