Thermally stable fuser member

A fuser member for use in an electrostatographic printing machine has at least one layer of an elastomer composition comprising a silicone elastomer and a mica-type layered silicate, the silicone elastomer and mica-type layered silicate forming a delaminated nanocomposite with silicone elastomer inserted among the delaminated layers of the mica-type layered silicate.

Attention is hereby directed to Application Ser. No. 08/556,554 (now 
abandoned) titled "INTERMEDIATE TONER TRANSFER MEMBER" having the 
inventors, Santokh S. Badesha, Arnold W. Henry, and Robert J. Gruber, 
which is filed concurrently with the present application. A 
continuation-in-part application, U.S. Ser. No. 08/870,742, of parent 
application U.S. Ser. No. 08/556,554 was filed on Jun. 6, 1997. 
CROSS REFERENCE TO RELATED APPLICATIONS 
BACKGROUND OF THE INVENTION 
The present invention relates to a silicone elastomeric fuser member for 
use in electrostatographic printing apparatus. In particular, it relates 
to silicone elastomers that are thermally stable and swell resistant. 
In electrostatographic reproducing apparatus commonly used today a 
photoconductive insulating member is typically charged to a uniform 
potential and thereafter exposed to a light image of an original document 
to be reproduced. The exposure discharges the photoconductive insulating 
surface in exposed or background areas and creates an electrostatic latent 
image on the member which corresponds to the image contained within the 
original document. Alternatively, a light beam may be modulated and used 
to selectively discharge portions of the charged photoconductive surface 
to record the desired information thereon. Typically, such a system 
employs a laser beam. Subsequently, the electrostatic latent image on the 
photoconductive surface is made visible by developing the image with 
developer powder referred to in the art as toner. Most development systems 
employ developer which comprised both charged carrier particles and 
charged toner particles which triboelectrically adhere to the carrier 
particles. During development the toner particles are attracted from the 
carrier particles by the charged pattern of the image areas of the 
photoconductive insulating area to form a powder image on the 
photoconductive area. The toner image may be subsequently transferred to a 
support surface such as copy paper to which it may be permanently affixed 
by heating or by the application of pressure. The present invention 
relates to the fusing of the toner image on a support. 
The use of thermal energy for fixing toner onto a support member is well 
known. In order to fuse electroscopic toner material onto a support 
surface permanently by heat, it is 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 material causes 
the toner material to be firmly bonded to the support. 
Several approaches to thermal fusing of electroscopic toner images have 
been described in the prior art. These methods include providing the 
application of heat and pressure substantially concurrently by various 
means: a roll pair maintained in pressure contact; a flat or curved plate 
member in pressure contact with a roll; a belt member in pressure contact 
with a roll; and the like. During operation of the fusing system of the 
two rolls, the support member to which toner images are electrostatically 
adhered is moved through the nip formed between the rolls with the toner 
image contacting the fuser roll thereby to effect heating of the toner 
images within the nip. Typical of such fusing devices are two roll systems 
wherein the fusing roll is coated with an adhesive material, such as 
silicone rubber or other low surface energy elastomer as, for example, 
tetrafluoroethylene resin sold by E. I. DuPont de Nemours under the trade 
name of Teflon. The silicone rubber which can be used as the surface of 
the fuser member can be classified into several groups according to the 
vulcanization method and temperature, i.e., room temperature vulcanization 
silicone rubber hereinafter referred to as RTV silicone rubber, and high 
temperature vulcanization type silicone rubber, referred to as HTV rubber. 
All these silicone rubbers or elastomers are well known in the art and are 
commercially available. 
It is important in the fusing process that no offset of the toner particles 
from the toner image support to the fuser member takes place during normal 
operations. The so called "hot offset" occurs when the temperature of the 
toner is raised to a point where the toner particles liquify and a 
splitting of the molten toner takes place during the fusing operation with 
a portion remaining on the fuser member. The 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. While many materials may 
initially function with good release properties with continued use, they 
tend to be contaminated with paper fibers, debris and toner as a result of 
hot offset of toner, thereby increasing the surface energy of the roll and 
perpetuating the destruction of release performance. Once the roll becomes 
contaminated the hot offset temperature starts to reduce and may reach a 
level near or below the minimum temperature necessary to fuse the toner to 
the fuser roll. 
Toner release agents such as silicone oil, in particular polydimethyl 
silicone oil is applied on the fuser roll to a thickness of about 1 micron 
to act as a toner release material. These materials possess a relatively 
low surface energy and are suitable for use in the heated fuser roll 
environment. In practice, a thin layer of silicone oil is applied to the 
surface of the heated roll to form an interface between the roll surface 
and the toner image carried on the support material. Thus, a low surface 
energy, easily parted layer is presented to the toners that pass through 
the fuse nip and thereby prevents toner from offsetting to the fuser roll 
surface. Further information concerning the fusing process may be found in 
U.S. Pat. No. 4,763,158 to Schlueter which is hereby totally incorporated 
by reference. 
Fuser members such as fuser rolls may take several different forms such as 
those wherein a metallic cylindrical sleeve such as aluminum is heated by 
a heating element disposed in the center of the aluminum sleeve which is 
covered by an intermediate layer of a silicone elastomer and a relatively 
thin fusing layer of a hydrofluoroelastomer such as an FKM elastomer. This 
configuration of a fuser member while capable of performing satisfactorily 
does exhibit a hardening of the silicone elastomer in the intermediate 
layer and a consequent degradation in life and performance. This hardening 
occurs because the silicone elastomer lacks sufficient thermal stability 
to maintain its physical properties over time at elevated temperatures 
such as the fusing temperature and beyond. In particular, it is believed 
that the silicone elastomer hardens because of thermal oxidative 
crosslinking of the silicone elastomer by oxygen reacting with methyl 
groups along the silicone chain, which in addition to leading to oxidative 
degradation by the application of heat in the presence of oxygen also 
liberates undesirable amounts of formaldehyde. The attack by oxygen is 
believed to create free radicals which by further reaction eventually 
results in a silicon-oxygen-silicon crosslink. This additional crosslink 
with oxygen as a bridge in the crosslinking network with the methyl groups 
of the elastomer stiffen the elastomeric network resulting in hardening of 
the silicone elastomer which thereafter becomes brittle and loses its 
toughness and conformance, shows more wear, reduces its elongation and 
fatigue life, and results in a higher modulus. In addition, the 
interfacial bonding between the silicone elastomer and the 
hydrofluoroelastomer deteriorates, adding to performance difficulties. As 
a result of this thermal instability and consequent hardening, a smaller 
fuser nip between the fuser roll and the pressure roll may occur resulting 
in reduced dwell time within the fuser nip, and, therefore, poorer fix of 
the toner to the paper which in turn may lead to paper handling 
difficulties. Furthermore, since the harder fuser roll does not conform as 
well to the pressure roll, the level of gloss in the final fused copy may 
be reduced which is a particularly negative aspect for color printing. 
In an alternative embodiment of a fuser member and typically a roll, the 
fusing surface is actually made from the silicone elastomer which may 
indeed be a thin surface coating on a thicker silicone elastomer layer on 
a heated aluminum core. When using such a silicone elastomer fusing 
surface, a silicone oil release agent is typically delivered to the fuser 
oil by a silicone elastomer donor roll. For further discussion of the 
elastomers and the silicone oil release agents, attention is directed to 
U.S. Pat. No. 4,777,087 to Hicks et al. These systems and in particular, 
the combination of the silicone elastomer fuser roll and the silicone oil 
release agent are highly successful in providing a fusing surface with a 
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 however may 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 fusing 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 to the print 
substrate. 
It is accordingly desirable to provide a silicone elastomer composition for 
use in a fusing member whether it be a fusing surface layer or an 
intermediate support layer in a fuser member for an electrostatographic 
printing apparatus. 
The following three documents relate to nanocomposites, the disclosures of 
said three documents being totally incorporated herein by reference: 
Shelly D. Burnside and Emmanuel P. Giannelis, "Synthesis and Properties of 
New Poly(Dimethylsiloxane) Nanocomposites," CHEMISTRY OF MATERIALS, vol. b 
7, no. 9, pp. 1597-1600 (September 1995); 
A set of fifteen slides (including the cover page) titled "Synthesis, 
Characterization, and Properties of Siloxane Nanocomposites," presented by 
Shelly D. Burnside and Emmanuel P. Giannelis at the American Chemical 
Society Northeastern Regional Meeting in Rochester, New York on Oct. 23, 
1995; and 
A set of eighteen slides (including the cover page) titled "Polymer Matrix 
Nanocomposites," presented by Emmanuel P. Giannelis at the American 
Chemical Society Northeastern Regional Meeting in Rochester, N.Y. Oct. 25, 
1995. 
SUMMARY OF THE INVENTION 
In accordance with a principle aspect of the present invention, a thermally 
stable, swell resistant, fuser member for use in an electrostatographic 
printing apparatus comprising at least one layer of an elastomer 
composition including a silicone elastomer and a mica-type layered 
silicate, said silicone elastomer and mica-type layered silicate forming a 
delaminated nanocomposite with silicone elastomer inserted among the 
delaminated layers of the mica-type layered silicate. 
In a further aspect of the present invention, the mica-type layered 
silicate has a high aspect ratio structure. 
In a further aspect of the present invention, the silicone elastomer is 
cured from a polyorganosiloxane having the formula: 
##STR1## 
where R is hydrogen or substituted or unsubstituted alkyl, alkenyl or aryl 
having less than 19 carbon atoms, each of A and B may be any of methyl, 
hydroxy or vinyl groups and 
EQU 0&lt;m/n&lt;1 and m+n&gt;350. 
In a further aspect of the present invention, the mica-type layered 
silicate has a particle size having a maximum length of from about 1 
micrometer to about 10 micrometers. 
In a further aspect of the present invention at least one layer of the 
fuser member is a surface layer of from about 10 mils to about 100 mils in 
thickness. 
In a further aspect of the present invention the at least one layer of the 
fuser member is an intermediate layer of from about 50 mils to about 100 
mils in thickness. 
In a further aspect of the present invention, the fuser member is a 
cylindrical roll which is internally heated by a heating element disposed 
in the center and the surface layer is a heated toner fusing surface 
layer. 
In a further aspect of the present invention, the toner fusing surface 
layer is an FKM hydrofluoroelastomer layer from about 1 to about 5 mils in 
thickness and there is an intermediate silicone elastomer composition from 
about 50 mils to about 100 mils in thickness. 
There is also provided a method of making a thermally stable, swell 
resistant fuser member comprising at least one layer of an elastomer 
composition comprising a silicone elastomer filled with a mica-type 
layered silicate forming a delaminated nanocomposite with the silicone 
elastomer intercalated among the delaminated layers of the mica-type 
layered silicate comprising mixing with mechanical shear a 
polyorganosiloxane with a mica-type layered silicate to delaminate the 
layers of the mica-type layered silicate and to intercalate the 
polyorganosiloxane among the delaminated layers of the mica-type layered 
silicate, adding with mechanical shear to said polyorganosiloxane 
intercalated delaminated layers an amount of a crosslinking agent and a 
catalyst sufficient to crosslink said polyorganosiloxane to a silicone 
elastomer, shaping the silicone elastomer intercalated delaminated 
nanocomposite and curing the shaped silicone elastomer intercalated 
delaminated nanocomposite to form said at least one layer of the fuser 
member.

DETAILED DESCRIPTION OF THE INVENTION 
To facilitate a greater understanding of the present invention, the 
following terms shall be interpreted to have the following meanings. 
Thermal stability shall refer to the ability of an elastomer to maintain 
its physical properties over time at one or more elevated temperatures and 
is expressed as a ratio of a property value at a particular time and 
temperature over the property value at time T.sub.0 and room temperature. 
In particular, it refers to stability of physical properties at fusing 
temperature and beyond in an electrostatographic printing apparatus. The 
lesser the reduction in the property over time at T.sub.1, T.sub.2, or 
T.sub.3 the greater the thermal stability. The term mica-type layered 
silicate (referred herein as "MTS") shall mean a leaf or sheet like 
laminated phyllosilicate mineral, typically natural or synthetic complex 
hydrous silicates based on aluminum, magnesium, sodium, potassium, 
calcium, lithium and iron silicates, having flat, six-sided monoclinic 
crystals, low hardness and perfect or near perfect basal cleavage. 
Typically they have a high degree of flexibility, elasticity and toughness 
and have laminae of the order of 10 angstroms in thickness which under 
mild shear can be delaminated or exfoliated. Typical examples include the 
principle mica-types of the general formula 
EQU W.sub.2 (X,Y).sub.4-6 Z-.sub.8 O.sub.20 (OH,F).sub.4 
where W is usually potassium; X, Y are aluminum, magnesium, iron or lithium 
and Z- is silicon or aluminum and include muscovite, phlogopite, biotite, 
and lepidolite. Other materials falling within the general designation of 
MTS include montmorillonite, bentonite, hectorite, vermiculite and 
saponite. Commercially available materials include montmorillonite, 
bentonite and hectorite which are available from Southern Clay Products, 
Gonzales, Texas. The term intercalated and the phrase intercalated 
phenomenon shall refer to the insertion of polymer chains among the 
individual layers of the mica-type layered silicates. The term 
nanocomposite is intended to define a delaminated or exfoliated mica-type 
layered silicate which has a silicone elastomer inserted into, between, 
and among several layers of the layered silicate, wherein each layer of 
the mica-type layered silicate has a thickness on a nanometer (10.sup.-9 
meter) scale. The term aspect ratio shall refer to the ratio of the length 
to thickness of the mica-type layer silicates and the term high aspect 
ratio shall define a large dimensional ratio of the MTS. 
Turning now to FIG. 1, this figure shows a fuser roll for use in the 
present invention. Although the fuser member shown in FIG. 1 is in the 
form of a roll, it is to be understood that the present invention is 
applicable to fuser members of other shapes, such as plates or belts. In 
FIG. 1, the fuser roll 10 is composed of a core 11 having coated thereon a 
thin layer 12 of the elastomer according to the present invention. The 
core 11 may be made of various metals such as iron, aluminum, nickel, 
stainless steel, etc., and various synthetic resins. Aluminum is preferred 
for the core 11, although it is not critical. The core 11 is hollow and 
the heating element 13 is generally positioned inside the hollow core to 
supply the heat for the fusing operation. Heating elements suitable for 
this purpose are known in the prior art and may comprise a quartz heater 
made of a quartz envelope having a tungsten resistance heating element 
disposed internally therein. The method of providing the necessary heat is 
not critical to the present invention, and the fuser member can be heated 
by internal means, external means or a combination of both. All heating 
means are well known in the art for providing sufficient heat to fuse the 
toner to the support. The composition of layer 12 will be described in 
detail below. 
The fuser roll 10 is shown in a pressure contact arrangement with a backup 
or pressure roll 14 which comprises a metal core 15 with a layer 16 of a 
heat-resistant material. In this assembly, both the fuser roll 10 and the 
pressure roll 14 are mounted on shafts which are biased so that the fuser 
roll 10 and pressure roll 14 are pressed against each other under 
sufficient pressure to form a nip 18. It is in this nip that the fusing or 
fixing action takes place. It has been found that the quality of the 
copies produced by the fuser assembly is better when the nip is formed by 
a relatively hard and unyielding layer 16 with a relatively flexible layer 
12. In this manner, the nip is formed by a slight deformation in the layer 
12 due to the biasing of fuser roll 10 on the pressure roll 14. The layer 
16 may be made of any of the well known materials such as 
polytetrafluoroethylene, polyfluoroalkoxy resin, fluorinated 
ethylene-propylene copolymer or silicone rubber. 
A sheet of support material 19 such as paper bearing thereon toner image 20 
passes between the fuser roll 10 and the pressure roll 14 and the toner 
image thereon is fused. 
FIG. 2 illustrates an alternative embodiment wherein intermediate the thin 
layer 12 and the supporting core 11 is a thicker intermediate high 
temperature resistant elastomeric layer 22 which may be of any suitable 
material such as the silicone elastomer of the present invention. 
The mica-type layered silicate may be present in an amount ranging for 
example from about 1% to about 50% by weight, preferably from about 5% to 
about 20% by weight, more preferably up to about 10% by weight, and 
especially from about 5% to about 10% by weight, based on the weight of 
the elastomer composition. The silicone elastomers used in accordance with 
the present invention are typically polyorganosiloxanes and include fluoro 
and vinyl substituted polyorganosiloxanes. 
A preferred group of elastomers include the curable silicone elastomers 
such as the commercially available condensation curable and addition 
curable materials. The typical curable polyorganosiloxanes are represented 
by the formula: 
##STR2## 
wherein R is hydrogen or substituted or unsubstituted alkyl, alkenyl or 
aryl having less than 19 carbon atoms, each of A and B may be any of 
methyl, hydroxy or vinyl groups and 
EQU 0&lt;m/n&lt;1 and m+n&gt;350. 
The condensation curable polyorganosiloxanes are typically silanol 
terminated polydimethylsiloxanes such as: 
##STR3## 
where n" is 350 to 2700. The terminating silanol groups render the 
materials susceptible to condensation under acid or mild basic conditions 
and are produced by kinetically controlled hydrolysis of chlorosilanes. 
Room temperature vulcanizable (RTV's) systems are formulated from these 
silanol terminated polymers with a molecular weight of 26,000 to 200,000 
and they may be crosslinked with small quantities of multifunctional 
silanes which condense with the silanol group. Crosslinking agents which 
are suitable for purposes of the present invention include esters of 
orthosilicic acid, esters of polysilic acid and alkyl trialkoxy silanes. 
Specific examples of suitable crosslinking agents for the condensation 
cured materials include tetramethylorthosilicate, tetraethylorthosilicate, 
2-methyoxyethylsilicate, tetrahydrofurfurylsilicate, ethylpolysilicate and 
butylpolysilicate, etc. During the crosslinking reaction, an alcohol is 
typically split out leading to a crosslinked network. We particularly 
prefer to use condensed tetraethylorthosilicate as a crosslinking agent in 
the composition of the invention. The amount of the crosslinking agent 
employed is not critical as long as a sufficient amount is used to 
completely crosslink the active end groups on the disilanol polymer. In 
this respect, the amount of crosslinking agent required depends on the 
number average molecular weight of the disilanol polymer employed. With 
higher average molecular weight polymers there are fewer active end groups 
present and thus a lesser amount of crosslinking agent is required and 
vice versa. Generally, with the preferred alpha omega hydroxy polydimethyl 
siloxane having a number average molecular weight of between about 26,000 
to about 100,000 we have found that between 6 to 20 parts by weight of 
condensed tetraethylorthosilicate per 100 parts by weight of disilanol 
polymer to be suitable. 
A particularly preferred embodiment of the present invention relates to a 
liquid addition cured polyorganosiloxanes achieved by using siloxanes 
containing vinyl groups at the chain ends and/or scattered randomly along 
the chain along with siloxanes having anything more than two silicon 
hydrogen bonds per molecule. Typically these materials are cured at 
temperatures of from about 100.degree. C. to 250.degree. C. 
Typical materials are represented by the formula: 
##STR4## 
where A", B" and R" are methyl or vinyl provided the vinyl functionality 
is at least 2, and 
EQU 0&lt;s/r&lt;1,350&lt;r+s&lt;2700. 
By the phrase the functionality is at least 2 it is meant that in the 
formula for each molecule there must be at least a total of 2 vinyl groups 
in the A", B" and any of the several R" sites within the formula. In the 
presence of suitable catalysts such as solutions or complexes of 
chloroplatinic acid or other platinum compounds in alcohols, ethers or 
divinylsiloxanes reaction occurs with temperatures of 100.degree. C. to 
250.degree. C. with the addition of polyfunctional silicon hydride to the 
unsaturated groups in the polysiloxane chain. Typical hydride crosslinkers 
are methylhydrodimethylsiloxane copolymers with about 15-70 percent 
methylhydrogen. Elastomers so produced exhibit increased toughness, 
tensile strength and dimensional stability. Typically, these materials 
comprise the addition of two separate parts of the formulation, part A 
containing the vinyl terminated polyorganosiloxane, the catalyst and the 
filler, part B containing the same or another vinyl terminated 
polyorganosiloxane, the crosslink moiety such as a hydride functional 
silane and the same or additional filler where part A and part B are 
normally in a ratio of one to one. During the additional curing operation 
the material is crosslinked via the equation 
EQU .tbd.SiH+CH.sub.2 =CHSi.tbd..fwdarw..tbd.SiCH.sub.2 CH.sub.2 Si.tbd. 
and since hydrogen is added across the double bond no offensive byproduct 
such as acids or alcohols is obtained. 
Accordingly and by way of example in the above formula for the 
polyorganosiloxane having substituents A, B, and R, typical substituted 
alkyl groups include alkoxy and substituted alkoxy, chloropropyl, 
trifluoropropyl, mercaptopropyl, carboxypropyl, aminopropyl and 
cyanopropyl. Typical substituted alkoxy substituents include 
glycidoxypropyl, and methacryloxypropyl. Typical alkenyl substituents 
include vinyl and propenyl, while substituted alkenyl include halogen 
substituted materials such as chlorovinyl and bromopropenyl. Typical aryl 
or substituted groups include phenyl and chlorophenyl. Hydrogen, hydroxy, 
ethoxy and vinyl are preferred because of superior crosslinkability. 
Methyl, trifluoropropyl and phenyl are preferred in providing superior 
solvent resistance, higher temperature stability and surface lubricity. 
The ratio of 
EQU m/n 
being between 0 and 1 identifies the polyorganosiloxane as a copolymer and 
the sum of m+n being greater than 350 identifies it as an elastomeric 
material. 
The crosslinking agent used in the composition is for the purpose of 
obtaining a material with sufficient crosslink density to obtain maximum 
strength and fatigue resistance. The amount of crosslinking agent employed 
is not critical as long as the amount used is sufficient to sufficiently 
crosslink the active groups of the polymer used. 
Crosslinking catalysts are well known in the art and include among others, 
stanneous octoate, dibutyltindilaurate, dibutyltindiacetate and 
dibutyltindicaproate for the condensation cured polyorganosiloxanes. The 
amount of catalysts employed is not critical, however, too small an amount 
of catalyst may lead to a very small reaction which is impractical. On the 
other hand, excessive amounts of catalysts may cause a breakdown of the 
crosslinked polymer network at high temperatures to yield a less 
crosslinked and weaker material, this adversely affecting the mechanical 
and thermal properties of the cured material. 
As previously mentioned the mica-type layered silicate have laminae of the 
order of 10 angstroms in thickness. They also have a large length to 
thickness ratio because of the plate like structure which is referred to 
hereinafter as having a high aspect ratio. Typically the mica-type layered 
silicates have a maximum length on the order of 1 micrometer and an aspect 
ratio of length to thickness of from about 100 to about 1000. As a result 
the mica-type layered silicates when used as a filler to enhance the 
thermal conductivity or modulus of the silicone elastomer form a 
continuous touching path to conduct heat. Accordingly, the mica-type 
layered silicates are typically used in amounts up to about 10% by weight 
of the total weight of the elastomer composition to provide the desired 
thermal stability and swell resistance. In certain embodiments of the 
present invention, beyond about 10% by weight of the elastomer 
composition, additional amounts of the mica-type layered silicate may 
merely provide a filler effect without further enhancing the desired 
properties. While not wishing to be bound to any theory, it is believed 
that the sheets of the mica-type layered silicate provide antioxidant 
properties due to their large surface area which thermally stabilizes the 
area that surrounds it. Further and with regard to swell resistance, the 
mica-type layered silicates provide a large surface area barrier to the 
silicone release agent, thereby resulting in reduction of swelling of the 
silicone elastomer. 
Attention is directed now to FIG. 3 wherein the manufacture of thermally 
stable swell resistant elastomer compositions is schematically 
illustrated. In this schematic, the first area 100 illustrates the 
laminated mica-type layered silicates 102 in a polyorganosiloxane monomer 
104 which when subjected to mechanical shear such as, for example, by 
simple stirring or mixing in a ball or pebble mill delaminates or 
exfoliates the layers of the mica-type layered silicate such that the 
polyorganosiloxane monomer 104 and individual layers of the mica-type 
layered silicate 102 are relatively uniformly mixed as illustrated in the 
second area 106 of the Figure. Upon the addition of suitable amounts of 
crosslinking agent and catalyst that are sufficient to crosslink the 
polyorganosiloxane to a silicone elastomer and following the desired 
shaping such as by dipping or spraying onto a substrate surface such as a 
roll or by molding in the form of a roll and curing the shaped silicone 
elastomer composition to provide a silicone elastomer filled with a 
mica-type layered silicate a delaminated nanocomposite is formed and is 
illustrated in the third area 108 of the FIG. 3 with silicone elastomer 
110 inserted among the delaminated layers of the mica-type layered 
silicate 102. The intercalated phenomenon starts with surface treating the 
MTS with long chain alkylamines or amino acids such as dodecylamine or 
dodecylamino acid to give the MTS an organophilic nature. This will then 
enhance the wetting of the MTS by silicone materials. On mixing the 
surface treated MTS with silicone, the silicone penetrates the MTS 
lamellae causing each lamella to be surrounded by silicone as the MTS 
exfoliates. 
With respect to the alternative embodiment wherein the silicone elastomer 
composition forms a fusing surface, experiments to conduct swelling 
evaluations of the silicone elastomer compositions according to the 
present invention have shown that the presence of only 5% by weight in the 
elastomer composition of the mica-type layered silicates, when made into a 
silicone elastomer according to the present invention and subjected to 
swelling in the presence of polydimethylsiloxane oil, resulted in a 
reduction in swelling of 50%. That is, the amount of swell was reduced by 
one-half with the presence of only 5% by weight of the mica-type layered 
silicate over that which would have been obtained without any mica-type 
layered silicate. As discussed in more detail later, FIG. 5 illustrates 
the swelling due to toluene in a silicone composition containing the 
stated volume fractions of the mica-type layered silicate. Since the 
ordinate axis represents the ratio of volume swell of silicone with MTS 
added to the volume swell of the silicone with no MTS added, there are no 
units and 1.0 represents the volume swell with no MTS added. 
Other additives or agents may be incorporated in the elastomeric 
composition in accordance with the present invention as long as they do 
not affect the integrity of the elastomer. Such agents include coloring 
agents, processing aids, accelerators and polymerization initiators which 
may be used in addition to the crosslinking agents and catalysts referred 
to above. MTS alone or in combination with low hardness fillers may be 
dispersed in the elastomer material in any suitable or convenient form or 
manner. It is preferably uniformly dispersed in the elastomer during 
compounding. For example, when the elastomer is in the form of a gum, the 
MTS and other filler may be milled into the gum prior to curing to form 
the elastomer. In general, the MTS and any filler are dispersed in the 
elastomer by mixing with the elastomer gum or other millable form of the 
elastomer compound preferably prior to solution or homogenization before 
application to the base member. The MTS and other filler present may be 
dispersed in the elastomer by conventional methods known to those skilled 
in the art. For example in a pebble mill, the MTS and elastomer may be 
compounded during which the MTS may be reduced in particle size. The 
compounding, however, should not be carried out to such a degree or level 
extent that the MTS loses its general leaf structure. 
The fuser member may then be prepared by applying the elastomer having the 
MTS and any filler dispersed therein directly to the base member in one 
application or by successively applying layers of the elastomer 
composition to the base member. The coating is most conveniently carried 
out by spraying or dipping in a light solution of homogeneous suspension 
containing the MTS. Molding, extruding and wrapping are also alternative 
techniques which may be used to make the fuser members. Typically, an 
elastomeric surface fusing layer is from about 1.0 mm to about 100 mils 
thick. In the alternative embodiment when the elastomer composition is 
used as an intermediate layer it is from about 50 mils to about 100 mils 
in thickness. In a particularly preferred embodiment, the silicone 
elastomer is an intermediate layer with a toner fusing surface layer of an 
FKM hydrofluoroelastomer from about 1 to about 5 mils in thickness. When 
the desired thickness of elastomer compound is coated onto the base or 
substrate member, the elastomer composition is cured and thereby fused to 
the base member. 
The FKM hydrofluoroelastomers, according to the present invention, are 
those defined in ASTM designation D1418-90 and are directed to 
fluororubbers of the polymethylene type having substituent fluoro and 
perfluoroalkyl or perfluoroalkoxy groups on a polymer chain. 
The fluoroelastomers useful in the practice of the present invention are 
those described in detail in U.S. Pat. No. 4,257,699 to Lentz, as well as 
those described in commonly assigned U.S. Pat. Nos. 5,017,432 to Eddy et 
al. and 5,061,965 to Finsterwalder et al. As described therein, these 
fluoroelastomers, particularly from the class of copolymers and 
terpolymers of vinylidenefluoride hexafluoropropylene and 
tetrafluoroethylene, known commercially under various designations as 
Viton A, Viton E60C, Viton E430, Viton 910, Viton GH and Viton GF, are 
suitable in the practice of the present invention. The Viton designation 
is a Trademark of E. I. DuPont deNemours, Inc. Other commercially 
available materials include Fluorel 2170, Fluorel 2174, Fluorel 2176, 
Fluorel 2177 and Fluorel LVS 76, Fluorel being a Trademark of 3M Company. 
Additional commercially available materials include Aflas a 
poly(propylenetetrafluoroethylene) copolymer, Fluorel II a 
poly(propylenetetrafluoroethyelene-vinylidenefluoride) terpolymer both 
also available from 3M Company. Also, the Tecnoflons identified as 
FOR-60KIR, FOR-LHF, NM, FOR-THF, FOR-TFS, TH, TN505 are available from 
Ausimont Chemical Company. Typically, these fluoroelastomers can be cured 
with a nucleophilic addition curing system, such as a bisphenol 
crosslinking agent with an organophosphonium salt accelerator as described 
in further detail in the above referenced Lentz Patent, and in U.S. Pat. 
No. 5,017,432 to Eddy et al. or with a peroxide as described in DuPont's 
literature. 
In the Examples below, unless otherwise specified, all parts and 
percentages are by weight. 
EXAMPLE 1 
With reference to FIG. 4, the thermal stability of a silicone elastomer was 
evaluated containing 0% and 10% by weight of the elastomer composition of 
a mica-type layered silicate. The two samples were prepared as follows: to 
100 parts of a 750 centipoise alpha, omega-dihydroxysilicone obtained from 
United Chemical Technologies, Inc. and designated as PS342.5, 2.5 parts of 
tetraethoxysilane crosslinker obtained from Aldrich Chemical Company and 2 
parts of Tin(II)ethylhexanoate catalyst obtained from Chemat and 
designated as T722 were added. The three ingredients were well mixed using 
a micro-tip Ultrasound probe available from Sonics & Materials. One 
sample, with 0% MTS, was poured into a 2 cm.times.2 cm.times.0.5 cm Teflon 
mold and cured for 12hours at room temperature and atmospheric pressure. 
Another sample had 10 parts of montmorillonite (surface treated with an 
amine surfactant) mixed into the 104.5 parts of 
dihydroxysilicone-crosslinker-catalyst material via the microtip 
Ultrasound probe. This latter sample was then poured into a Teflon mold of 
dimensions similar to the one above and also cured for 12 hours at room 
temperature and atmospheric pressure. This graphical representation of 
FIG. 4 illustrates the weight percent loss of water and formaldehyde at 
various temperatures for the silicone elastomer composition. As may be 
observed by the addition of a small amount, 10% by weight of the mica-type 
layered silicate based on the weight of the elastomer composition, a 
rather greatly improved thermally stable silicone elastomer composition 
was achieved and in particular has a greatly improved thermal stability 
over the range of 400.degree.-500.degree. C. where at the same temperature 
range the weight of the silicone elastomer composition without any 
mica-type layered silicate dropped from 100% to almost 0%. The ordinate 
axis represented how much of the original weight of silicone compound was 
still present after heating to the progressively higher temperatures. 
Starting at room temperature, the samples were heated at a rate of 
10.degree. C. per minute. 
It is believed that the improvement in thermal stability is particularly 
effective in those applications wherein the silicone elastomer composition 
is used as an intermediate in a fuser member composition between the fuser 
member substrate and the actual fusing surface. 
EXAMPLE 2 
The three MTS incorporated silicone specimens were formulated in the 
following manner: to 100 parts of a 750 centipoise alpha, 
omega-dihydroxysilicone obtained from United Chemical Technologies, Inc. 
and designated as PS342.5, 2.5 parts of tetraethoxysilane crosslinker 
obtained from Aldrich Chemical Company and 2 parts of 
Tin(II)ethylhexanoate catalyst obtained from Chemat and designated as T722 
were added. The three ingredients were well mixed using a micro-tip 
Ultrasound probe available from Sonics & Materials and the montmorillonite 
(surface treated with an amine surfactant) was also added and mixed into 
the dihydroxysilicone-crosslinker-catalyst mixture using the micro-tip 
Ultrasound probe. The specimens utilized for the toluene swell experiments 
were made using samples ranging from 3 to 10 weight percent of surface 
treated montmorillonite (3 to 10 parts per hundred of the PS342.5). The 
crosslinked samples were made by pouring the various mixtures into open 2 
cm.times.2 cm.times.0.5 cm Teflon molds and curing of the material 
occurred at room temperature and atmospheric pressure for 12 hours. The 
first point in FIG. 5 at about 0.013 volume fraction of nanocomposite 
represented 3 parts of the surface treated montmorillonite per hundred 
parts of the 750 centipoise dihydroxysilicone and tetraethoxysilane 
mixture. At this 3 part per hundred level of surface treated 
montmorillonite the volume swell of the silicone network in toluene 
dropped by about 38%. The next points at 0.032 and 0.048 represented 5 and 
10 part per hundred levels of surface treated montmorillonite. As can be 
seen from FIG. 5 the additional loadings of the surface treated 
montmorillonite reduced the volume swell of the silicone network still 
further to about 55% of the swell in toluene obtained for the silicone 
network without any added montmorillonite. The reduction in toluene swell 
is important because it indicates to what degree the silicone and 
montmorillonite compound swell in the commonly used toner release agent, 
silicone oil, will be reduced. Since swelling of an elastomer network such 
as silicone greatly reduces its physical strength and thus its functional 
life, a reduction of the amount of swelling increases its physical 
strength and extends its useful life. 
Thus, according to the present invention a thermally stable and swell 
resistant silicone elastomer composition has been provided. In addition to 
increased thermal stability and resistance to swell in oil, the addition 
of small amounts of mica-type layered silicate to a silicone elastomer 
composition provides a longer roll life, one which has a reduced failure 
mode due to hardness and one which is easy to fabricate since it merely 
requires stirring with mild shear. In addition, the relatively low amount 
of mica-type layered silicate material characterized as a filler enables 
an inexpensive material and method of manufacture. 
While the invention has been described in detail with reference to specific 
and preferred embodiments, it will be appreciated that various 
modifications and variations will be apparent to the artisan. For example, 
while the invention has been described with reference to the formation of 
a fuser member in the configuration of a fuser roll, it will be equally 
well understood that it may be used in the configuration of a belt or a 
pad. In addition, while the fuser member has been illustrated as a fuser 
roll, it may in addition be employed as a pressure roll or a release agent 
donor roll. All such modifications and embodiments as may readily occur to 
one skilled in the art are intended to be within the scope of the appended 
claims.