U.S. patent application number 15/193553 was filed with the patent office on 2016-10-20 for elastomer compositions with silane functionalized silica as reinforcing fillers.
The applicant listed for this patent is SCHLUMBERGER TECHNOLOGY CORPORATION. Invention is credited to Agathe Robisson, Huilin Tu.
Application Number | 20160304635 15/193553 |
Document ID | / |
Family ID | 48654747 |
Filed Date | 2016-10-20 |
United States Patent
Application |
20160304635 |
Kind Code |
A1 |
Tu; Huilin ; et al. |
October 20, 2016 |
ELASTOMER COMPOSITIONS WITH SILANE FUNCTIONALIZED SILICA AS
REINFORCING FILLERS
Abstract
Certain embodiments described herein are directed to silane
functionalized fillers that may be, for example, covalently coupled
to a polymer. In some examples, devices that include the filler
reinforced polymer compositions are also described.
Inventors: |
Tu; Huilin; (Sugar Land,
TX) ; Robisson; Agathe; (Cambridge, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SCHLUMBERGER TECHNOLOGY CORPORATION |
Sugar Land |
TX |
US |
|
|
Family ID: |
48654747 |
Appl. No.: |
15/193553 |
Filed: |
June 27, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13335086 |
Dec 22, 2011 |
9403962 |
|
|
15193553 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08K 9/06 20130101; F04C
2/1075 20130101; C08F 8/42 20130101; C08K 3/36 20130101; C09C
1/3072 20130101; F04B 23/00 20130101; C07F 7/1804 20130101; F05C
2225/04 20130101; C09C 1/3081 20130101; C08F 2810/40 20130101; C08F
8/18 20130101; C08K 3/36 20130101; C08K 9/06 20130101; F04C 2230/91
20130101; C08L 27/12 20130101; C08L 27/12 20130101 |
International
Class: |
C08F 8/42 20060101
C08F008/42; C07F 7/18 20060101 C07F007/18 |
Claims
1. A method comprising: reacting a filler with at least one silane
coupling agent having the formula Q.sub.m-Si--Z.sub.n, where Z
comprises one or more groups that can provide covalent attachment
to the filler, Q is --R''-G or --CR'.sub.2--CR'--R''-G, where R' is
a hydrogen or a fluorine, R'' is optional and is a linear or
branched C1-C18 alkyl group, optionally containing one or more
ether oxygen atoms and optionally fluorinated, G is a halogen, a
nitrile group, or a vinyl group, and the sum of m+n is equal to
four to covalently couple the silane to the filler; and reacting
the covalently coupled silane-filler with a polymer to covalently
couple the polymer to the covalently coupled silane-filler.
2. The method of claim 1, further comprising forming free radicals
of the polymer during the reacting the covalently coupled
silane-filler with a polymer to couple the polymer at unsaturated
sites of the silane of the covalently coupled silane-filler.
3. The method of claim 2, further comprising reacting the filler
with the at least one silane until substantially all surface sites
of the filler comprise the silane coupling agent.
4. The method of claim 3, further comprising reacting the filler
with the at least one silane coupling agent in the presence of an
initiator.
5. The method of claim 1, further comprising processing the
covalently coupled polymer-silane-filler using one or more of a
mixer, a mill, a mold, a calendering device and an extruder.
6. A silane coupling agent having the formula of
Q.sub.m-Si--Z.sub.n, where Z comprises one or more groups that can
provide covalent attachment to a filler, Q is --R''-G or
--CR'.sub.2--CR'--R''-G, where R' is a hydrogen or a fluorine, R''
is optional and is a linear or branched C1-C18 alkyl group,
optionally containing one or more ether oxygen atoms and optionally
fluorinated, G is a halogen, a nitrile group, or a vinyl group, and
the sum of m+n is equal to four.
7. The silane coupling agent of claim 6, in which Z is selected
from a hydroxy, an alkoxy, an acyl-oxyl, a halogen and an
amine.
8. The silane coupling agent of claim 6, selected from the
following formulae: ##STR00003##
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 13/335,086, filed Dec. 22, 2011.
FIELD
[0002] Examples disclosed herein relate generally to
silica-reinforced elastomer compositions. More particularly,
certain embodiments disclosed herein are directed to silane
coupling agents and/or silane-functionalized fillers effective to
covalently couple a filler to a polymer such as, for example, a
fluoropolymer.
BACKGROUND
[0003] Fillers can be added to elastomer compounds and other
polymers. However, limited reinforcement effect of fillers is
achieved due to the weak interactions between the fillers and the
polymer.
SUMMARY
[0004] In one aspect, embodiments disclosed herein relate to a
composition that includes a fluoropolymer covalently coupled to a
filler through a silane coupling agent, the silane coupling agent
having a chemically similar reactive moiety as a cure site moiety
of the fluoropolymer to which the silane coupling agent is
bonded.
[0005] In another aspect, embodiments disclosed herein relate to a
method that includes reacting a filler with at least one silane
coupling agent having the formula Q.sub.m-Si--Z.sub.n, where Z
comprises one or more groups that can provide covalent attachment
to the filler, Q is --R''-G or --CR'.sub.2--CR'--R''-G, where R' is
a hydrogen or a fluorine, R'' is optional and is a linear or
branched C1-C18 alkyl group, optionally containing one or more
ether oxygen atoms and optionally fluorinated, G is a halogen, a
nitrile group, or a vinyl group, and the sum of m+n is equal to
four to covalently couple the silane to the filler; and reacting
the covalently coupled silane-filler with a polymer to covalently
couple the polymer to the covalently coupled silane-filler.
[0006] In yet another aspect, embodiments disclosed herein relate
to a silane coupling agent having the formula of
Q.sub.m-Si--Z.sub.n, where Z is one or more groups that can provide
covalent attachment to a filler, Q is --R''-G or
--CR'.sub.2--CR'--R''-G, where R' is a hydrogen or a fluorine, R''
is optional and is a linear or branched C1-C18 alkyl group,
optionally containing one or more ether oxygen atoms and optionally
fluorinated, G is a halogen, a nitrile group, or a vinyl group, and
the sum of m+n is equal to four.
[0007] In yet another aspect, embodiments disclosed herein relate
to a moving or progressive cavity motor or pump assembly having an
inlet end and an outlet end, the motor or pump includes a housing
and a rotor and a stator disposed within the housing. The surface
of the rotor or the stator is made of an elastomer material which
permits a seal to form between contacting surfaces of the rotor and
the stator. The elastomer material comprises a polymer covalently
coupled to a filler through a silane coupling agent, the silane
coupling agent having a chemically similar reactive moiety as a
cure site moiety of the fluoropolymer to which the silane coupling
agent is bonded
[0008] Additional aspects, examples, features and embodiments of
the technology will be apparent to the person of ordinary skill in
the art, given the benefit of the instant specification.
BRIEF DESCRIPTION OF THE FIGURES
[0009] Certain features, aspect and examples are described in more
detail below with reference to the accompanying figures in
which:
[0010] FIGS. 1A-1C show one process of covalently coupling a silane
coupling agent to a surface of a filler, in accordance with certain
examples;
[0011] FIG. 2 is an illustration of a filler particle covalently
coupled to a silane coupling agent, in accordance with certain
examples;
[0012] FIG. 3 is an illustration of a filler particle covalently
coupled to a polymer through a silane coupling agent, in accordance
with certain examples;
[0013] FIG. 4 is an illustration of a thermally induced cure
mechanism between a polymer and a silane coupling agent covalently
coupled to a filler particle;
[0014] FIGS. 5A-5C are illustrations showing particle dispersions
and phases, in accordance with certain examples;
[0015] FIG. 6 shows a detailed view of a power section of a
downhole motor; and
[0016] FIG. 7 is a cross-sectional view of the power section of the
downhole motor, taken along section line 7-7 of FIG. 6
[0017] It will be recognized by the person of ordinary skill in the
art, given the benefit of this disclosure, that the compounds shown
in the figures and used throughout the text may be shown with
disproportionate bond lengths, bond angles and the like to
facilitate a better understanding of the technology described
herein. Unless otherwise specified, no particular stereochemistry
is implied in the illustrative chemical compounds drawn and
described herein.
DETAILED DESCRIPTION
[0018] Certain examples described herein provide advantages over
existing coupling agents and/or fillers and materials produced
using such coupling agents and/or fillers including, but not
limited to, improved elastic modulus stability at high temperature,
reduction of the Payne effect in fillers modified with the silane
coupling agents (i.e., reduced tangent delta), and increased use
life of parts or components produced using the materials disclosed
herein. These and other advantages will be recognized by the person
of ordinary skill in the art, given the benefit of this
disclosure.
[0019] Certain embodiments of the polymers produced using the
coupling agents and/or fillers disclosed herein may be used in
numerous industrial, medical and mechanical applications, and are
particularly suited for environments where high temperature, high
pressure, aggressive chemicals and mechanical loads may be required
or encountered. For example, certain embodiments of the
cross-linked polymers may be particularly suited for use in oil
field service (OFS) industry such as, for example, the heavy oil
market in: (1) structural component and insulation applications
such as electrical pads and cables, feed-through, housing and
packaging material of electrical and chemical devices, valves,
pumps, and etc.; (2) elastomeric applications: general-purpose
seals including o-rings and gaskets, packers for exploration and
production tools including mechanical packers, inflatable packers
and swellable packers, mud motor, actuators, cables and etc.
Certain examples of polymers produced using the coupling agents
and/or fillers and other materials disclosed herein may also be
used in down-hole applications such as chemical, wear, and heat
resistant piping, sleeves, wire and cable jacketing, coatings,
connectors, liners, tubes and similar devices. In addition, the
polymers disclosed herein have additional uses such as, for
example, in snap fit parts, parts used in load bearing
applications, heat shrinkable molded parts, and other parts used in
the electrical, automotive, aerospace, medical industries and oil
field service industries.
[0020] In certain embodiments, the polymers produced using the
coupling agents and/or fillers disclosed herein may be used by
themselves or in combination with one or more other polymers,
metals or non-metals, or structural components to provide an
assembly configured for a desired use. These and other applications
and uses of the materials described herein will be readily selected
by the person of ordinary skill in the art, given the benefit of
this disclosure.
[0021] The compositions produced using the silane functionalized
fillers described herein provide for covalent coupling of the
polymer to the filler through the silane functionalization. The
term covalent coupling refers to attachment through one or more
covalent bonds but not necessarily direct attachment to a
particular species without any intervening atoms. The fillers may
be pre-modified with the silane functionalization prior to being
compounded with the polymer or may be reacted with the silane
during compounding.
[0022] Fillers used in fluoroelastomer compounds are different from
those in conventional elastomers. Limited reinforcement effects of
active fillers are observed due to the weak interactions at the
interface of active fillers and fluoroelastomers. Non-active or low
active carbon black or mineral fillers in loadings up to 50 phr may
be used. In non-limiting examples, MT-black N990 filler is used
because of its large particle size and low structure, as well as
its lower pH that leads to shorter curing time. Other fillers
including various grades of other carbon blacks, fibrous calcium
silicate, barium sulfate, titanium oxide, iron oxide, silica,
poly(tetrafluoroethylene) (PTFE) powders, etc., may also be
used.
[0023] Strong interactions can be achieved at the
filler-fluoropolymer interface if the fillers are covalently bound
to the polymers. Silane coupling agents, which are capable of
forming covalent bonds directly to the polymer, can be used to
enhance the adhesion between the polymer and the fillers, such as
silica fillers. The fillers may be pre-modified with the silane
coupling agents to possess silane functionalization prior to being
compounded with the polymer or the fillers may be reacted with the
silane coupling agent during compounding. In either case, the
silane may covalently bind the filler to the polymer and thus be
referred to a silane coupling agent. In embodiments, the silane
coupling agent may possess at least one moiety that is the same as
the reactive or cure site monomer or moiety of the polymer being
modified.
[0024] Certain embodiments described herein are directed to
thermally stable silane coupling agents which are effective to
provide covalent bonding between silica fillers and
fluoroelastomers, perfluoroelastomers, fluoroplastics and other
polymers. The advantages provided in at least certain embodiments
include, but are not limited to: (1) the reactivity of the cure
site moiety in these silane coupling agents should be the same as
or chemically similar to the cure site moiety on the polymer so
that the silane coupling agent can react well with the polymer
matrix to form cross-links providing a reinforcing effect; (2) the
thermal stability of these silanes and the produced cross-links are
excellent so that reinforcing effect will be present even at high
temperatures; and/or (3) similar to conventional coupling agents,
these functional silanes can also improve the dispersion of silica
fillers by changing their surface polarity.
[0025] In one embodiment, the silane coupling agents have a general
structure as shown in formula (I):
Q.sub.m-Si--Z.sub.n (I)
where Q comprises one or more groups that can provide covalent
attachment to the polymer and Z comprises one or more groups that
can provide covalent attachment to the filler.
[0026] In certain embodiments, the Z group of formula (I) may be
selected such that reaction with one or more groups on the filler
surface results in covalent bond formation between the coupling
agent and the filler. In certain examples, Z may be a hydrolyzable
group including, but not limited to, a hydroxy, an alkoxy, an
acyl-oxyl, a halogen, an amine or other suitable hydrolyzable
group. In some examples, the Z group(s) may be labile and cleaved
or otherwise removed through dehydration or other suitable
mechanisms such that the Si group of formula (I) can covalently
bond to a surface moiety on the filler to covalently couple the
silane to the filler. For example, Z may be a hydroxyl group that
can protonate and leave as water with subsequent or concurrent
formation of a covalent bond between the filler and the coupling
agent. In some examples, Z may be an alkyl group comprising a
hydroxyl group including, but not limited to, methoxy, ethoxy,
propoxy, butanoxy or other oxygen containing alkyl groups which may
be saturated or unsaturated. In addition, where more than one Z
group is present, the Z group may be the same or may be
different.
[0027] The sum of m+n is normally equal to four, with each of m and
n independently selected from zero, 1, 2, 3 and 4. In some
examples, n is 3 and m is 1 or n is 2 and m is 2 or n is 1 and m is
3. It is also possible for m to be 4 and n to be zero or for m to
be zero and n to be 4 depending on the exact substituents selected
for Q and Z.
[0028] As mentioned above, in embodiments, the silane coupling
agent may possess at least one moiety that is the same as or
chemically similar to the reactive or cure site moiety of the
polymer being modified. This cure site moiety on the silane
coupling agent may be represented as Q in formula (I) above. The
cure site moiety of the polymer being modified may depend on the
particular curing mechanism being used. For example, a free radial
curing mechanism may require a cure site monomer, discussed below,
to be incorporated into the polymer backbone to allow for
crosslinking. By having a similar moiety as the cure site monomer
present in a silane coupling agent, the polymer may also form
covalent bonds with the filler (through the silane coupling agent)
during curing of the polymer. Cure site monomers may generally have
the formula CR'.sub.2.dbd.CR'--R''-G, where R' is a hydrogen or a
fluorine, R'' is optional and may be a linear or branched alkylene
group, optionally containing one or more ether oxygen atoms and
optionally fluorinated, and G is a halogen, such as Br or I, a
nitrile group, or a vinyl group. Thus, Q may have a similar
chemistry of --CR'.sub.2--CR'--R''-G or --R''-G, where R' is a
hydrogen or a fluorine, R'' is a linear or branched C1-C18 alkyl
group, optionally containing one or more ether oxygen atoms and
optionally fluorinated, and G is a halogen, such as Br or I, a
nitrile group, or a vinyl group.
[0029] For fluoropolymers not containing a cure site monomer, such
as polymers cured by a bisphenol or diamine curative, curing may
involve dehydrofluorination at a vinylidene fluoride site, followed
by nucleophilic substitution by a hydroxy group of bisphenol or an
amine addition. Thus, in such cases, the silane coupling agent may
include a terminal vinylidene fluoride group, i.e., Q may have a
chemistry of --CR'.sub.2--CR'--R''--CR'.dbd.CR'.sub.2 or
--R''--CR'.dbd.CR'.sub.2, where R' is a hydrogen or a fluorine, R''
is optional and may be a linear or branched C1-C18 alkyl group,
optionally containing one or more ether oxygen atoms and optionally
fluorinated.
[0030] In certain embodiments, the silane coupling agent may take
the form of a compound as shown in the below formulae:
##STR00001## ##STR00002##
In the above formulae, the Q group is shown to be based on reaction
of a silane with CR'.sub.2.dbd.CR'--R''-G containing a vinyl (or
vinylidene fluoride) group. It is envisioned that the Q group on
the silane may be the same as the pendant group of the cure site
monomer hanging off of the polymer backbone, or the cure site
monomer may be reacted with a silane (as shown above) through a
vinyl or vinylidene fluoride group such that there additional C2
group within Q as compared to the pendant group of the cure site
monomer extending from the polymer backbone and thus the Q group is
the same as the cure site monomer chemistry (pre-polymerized).
Further, while ethoxy groups are shown as the Z substituents in the
above formulae, it is intended that any Z group described above,
including hydroxyl, alkoxy, acyl-oxyl, halogen and amine groups may
be used, in any combination within a single coupling agent.
[0031] The silane coupling agent may be present in amounts ranging
from 0.5 to 25 parts per hundred parts of resin. In another
embodiment, the silane coupling agent may be present in an amount
ranging from 0.1 to 5 parts per hundred parts of resin.
[0032] The illustrative examples of the silane coupling agents
described herein may be synthesized using known methods of
producing silane compounds. For example, halo- or alkoxysilanes may
be reacted with Grignard reagents (RMgX where R is an organic group
and X is a halogen) or alkali metal organics, e.g., RLi where R is
an organic group as shown in the reaction schemes below.
RMgCl+HSiCl.sub.3--->RHSiCl.sub.2+MgCl.sub.2
RLi+SiCl.sub.4--->RSiCl.sub.3+LiCl
Another method of synthesizing silane coupling agents is through
hydrosilyation of an olefin in the presence of a catalyst such as,
for example, chrloroplastinic acid, t-butylperoxide and amine
complexes. The silicon in general ends up on the least substituted
carbon.
RCH.dbd.CH.sub.2+HSiCl.sub.3--->RCH.sub.2CH.sub.2SiCl.sub.3
Hydrosilylation may occur, for example, in the presence of Karstedt
catalyst (Pt.sub.2{[(CH2.dbd.CH)Me.sub.2Si].sub.2O}.sub.3) to
silylate an unsaturated side chain. In other examples,
organosilanes may also be produced by direct synthesis of an
organohalide with silicon using heat and a copper catalyst.
RCl+Si--->RSiCl.sub.3+R.sub.2SiCl.sub.2+R.sub.3SiCl
[0033] In certain embodiments, the silane coupling agents may react
with the filler through various mechanisms. In one route, the
silane may first react with additional silane coupling agents to
provide a condensed product having polysiloxy linkages. Next,
hydrogen bonding of the organo group(s) of the silane to the
surface of the filler may first occur. Protons from the surface may
be donated to the organo groups of the coupling agent followed by
loss of water (dehydration) and subsequent linkage between the
filler surface and the silane may then occur with loss of water. An
illustration of the overall process is shown in FIGS. 1A-C using a
generic silane.
[0034] Illustrative organo groups that may be used in the silane
coupling agents include, but are not limited to, --SiCl.sub.3,
--SiBr.sub.3, --SiF.sub.3, --Si(OMe).sub.3, --Si(OEt).sub.3,
--Si(OnPr).sub.3, --Si(OnBu).sub.3, --Si(OEtBu).sub.3, and
--Si(OAc).sub.3 where Me is methyl, Et is ethyl, nPr is n-proply,
nBu is n-butyl, and Ac is acetyl. The substituents of the silane
group need not be the same. In some examples, three of the
substituents may be the same, two of the substituents may be the
same or the three substituents may be different. It is desirable
that the substituents of the silane be hydrolyzable groups whether
or not the substituents are the same or not.
[0035] In certain embodiments, to synthesize the silane coupling
agent compounds, the base structure may be hydrosilylated, e.g., a
Q-Cl base structure can be hydrosilylated. For example,
hydrosilylation of Q-Cl with proper tri-functional (triethoxy,
trimethoxy, or trichloro) silanes at the presence of Karstedt
catalyst can provide the silane coupling agents.
[0036] In certain embodiments, by modifying the filler surface,
different properties are achieved. First, the surface polarity of
the silica filler is dramatically changed. For example, before
silanization, silica fillers (fumed or precipitated) have very high
surface energy. They tend to form large agglomerates in a polymer
matrix which often become the crack-initiation sites and thus
degrade the mechanical properties of the composites. When silica
fillers are treated with silane coupling agents, their surface
energy is lowered and it becomes similar to that of
fluoroelastomers. These modified fillers will absorb much less
moisture, or even not absorb water vapor if complete silane
coverage is achieved. As a result, the fillers will disperse well
in fluoroelastomers when compounded with fluoroelastomer gums.
Second, the silanes are reactive. At the curing conditions of
fluoroelastomers and etc., the cure site moiety of these silanes
will react (leading to cross-links at the filler surfaces) with the
cure site moieties on the polymers and thus bind the fillers
covalently to the polymers. For example, there may be covalently
bound rubber on the filler surfaces. The bound rubber can affect
the mechanical properties of rubbers.
[0037] When comparing bound rubber content and properties in
different systems or at different conditions for one particular
polymer-filler system, several factors should be considered as
bound rubber is sensitive to the chemical and physical nature of
the polymers and fillers, as well as the experimental conditions
(temperature, solvent and etc.) at which the bound rubber is
isolated and measured. Covalent bound rubber obtained using the
silane coupling agents described herein is very different from that
in polyolefin-carbon black systems where physical attractions
tether the polymer layer near the filler surfaces. The bond
dissociation energies of silicon-oxygen, silicon-carbon and
carbon-carbon (single) bonds, which are the major types of chemical
bonds at the cure site moiety-silane series modified silica
surface, are about 370-570 kJ/mol. As a comparison, the absorption
energy of polyolefins on carbon blacks is in general about 10-35
kJ/mol (at least one order of magnitude weaker). The exceptionally
strong bonding present in the covalently bound rubber can assist in
providing excellent high-temperature resistance of the polymer
compounds.
[0038] In certain embodiments, the surface modification of silicate
surfaces using these silane coupling agents can be carried out by
standard procedures. The coupling agents can be applied to the
substrates by deposition from aqueous alcohol, deposition from
aqueous solution, bulk deposition onto powders by a spray-on
method, integral blend method, anhydrous liquid phase deposition,
vapor phase deposition, spin-on deposition and spray application.
For chlorosilanes, they can be deposited from alcohol solution.
Notwithstanding which particular application procedure may be
selected, the reaction of the silane coupling agents can be
categorized into four steps for convenience purposes. First,
hydrolysis of the three hydrolyzable groups occurs (water is
present in the solvent or absorbed at the surface from air).
Condensation to oligomers follows. The oligomers then form hydrogen
bonds with hydroxyl group on the surface. Finally, during drying or
curing, a covalent linkage is formed with the substrate with
concomitant loss of water. One example of the hydrolytic deposition
of silanes is shown in FIGS. 1A-C. An illustration showing a cure
site moiety-containing silane covalently coupled to the surface of
a silica particle is shown in FIG. 2. In use, the silica filler is
seldom present as a single spherical particle as shown in FIG. 2.
In many instances, the silica fillers arrange themselves similar to
strings of pearls.
[0039] In certain embodiments, an excess of silane coupling agent
may be used such that substantially all accessible hydroxyl sites
(or other reactive sites) on the filler surface can be modified
with a silane coupling agent. In other examples, complete coverage
with silane coupling agents may not be required. High-temperature
silanes such as phenyltriethoxysilane,
pentafluorophenyltriethoxysilane, p-tolyltrimethoxysilane,
p-trifluoromethyltetrafluorophenyl-triethoxysilane and etc. can be
mixed with the silane coupling agents to dilute the surface
concentration of the coupling silanes. These high-temperature
silanes serve as covering agents which modify the surface polarity
of the fillers and do not form covalent bonds to any substantial
degree.
[0040] In certain examples, the exact filler used with the silane
coupling agents is not of great consequence. In particular many
different types of fillers may be used, and in certain instances
more than one type of filler may be used. Illustrative types of
fillers that can be used include, but are not limited to, silica,
precipitated silica, amorphous silica, vitreous silica, fumed
silica, fused silica, quartz, glass, aluminum, aluminum-silicate
(e.g., clays), copper, tin, talc, inorganic oxides (e.g.,
Al.sub.2O.sub.3, Fe.sub.2O.sub.3, TiO.sub.2, Cr.sub.2O.sub.3),
steel, iron, asbestos, nickel, zinc, silver, lead, marble, chalk,
gypsum, barites, graphite, carbon black, treated carbon black such
as, for example, silicon treated carbon black and other particles,
powders and materials that include, or can be chemically modified
to include, one or more surface reactive groups. Fumed silica
Cab-o-Sil M5 (Cabot) is one example of a filler than can be used.
Fillers may be incorporated in amounts ranging from about 1 to 50
parts per hundred parts of resin. Some embodiments may use at least
2 parts per hundred parts of resin, at least 5 parts per hundred
parts of resin, at least 10 parts per hundred parts of resin or at
least 20 parts per hundred parts of resin.
[0041] Similar to the fillers, the exact polymer used with the
silane coupling agents may vary. In one embodiment, polymers that
include one or more of a double bond, halogen, leaving groups or
that can react by free radical, amine curing, bisphenol curing, or
thermal curing mechanisms may be used with the silane coupling
agents described herein. Illustrative polymers include, but are not
limited to a high density polyethylene, a nylon, a polycarbonate, a
polyether sulfone, a polyphenylene oxide, a polyphenylene sulfide,
a polypropylene, a polystyrene, a polyurethane, a polysulfone, a
polyvinylchloride, a polyamide, a polyimide, a polyamide-imide, a
polybutylene, a polybutylene terphthalate, a polyepoxide and other
polymers. In some examples, a single type of polymer, different
polymers, blends of polymers and the like may be used. Thus, in
examples described herein that use a fluoropolymer in combination
with a coupling agent, the fluoropolymer may be substituted with,
or used in combination with, one or more other polymers. In some
examples, the coupling agent may be particularly suited for use
with polymers in high temperature applications such as, for
example, those greater than or equal to about 150.degree. C.
[0042] In one embodiment, a halopolymer such as a fluoropolymer, a
chloropolymer, and a bromopolymer may be used. Mixed halo polymers
including two or more different halo substituents, such as, for
example, chlorofluoropolymers and bromofluoropolymers, may also be
used. Halopolymers may also include heteroatoms including, but not
limited to, nitrogen, oxygen, sulfur and heterogroups formed from
nitrogen, oxygen and sulfur. Of particular interest for use with
the cross-linkers disclosed herein are fluoropolymers, which are
difficult to cross-link due to the inertness of the carbon-fluorine
bond. Fluoroelastomers in general are synthesized by radical co-,
ternary or tetrapolymerizations of fluoroalkenes. Examples of
fluoroelastomers include copolymers comprising units of vinylidene
fluoride (VDF or VF.sub.2) and units of at least one other
copolymerizable fluorine-containing major monomer such as
tetrafluoroethylene (TFE), hexafluoropropylene (HFP),
chlorotrifluoroethylene (CTFE), vinyl fluoride (VF), ethylene (E),
propylene (P), and a perfluoro(alkyl vinyl ether) (PAVE). Specific
examples of PAVE include perfluoro(methyl vinyl ether) (PMVE),
perfluoro(ethyl vinyl ether) and perfluoro(propyl vinyl ether).
Depending on the type of curing mechanism to be used, the polymer
may also incorporate at least one cure site monomer therein to
allow a radical to be formed by a peroxide and then crosslinked by
a co-agent. Cure site monomers may be incorporated into
fluoroelastomer in an amount ranging from about 0.1 to about 10 (or
from about 0.2 to about 5) weight percent, based on the total
composition of the fluoroelastomer. The remaining units in the
fluoroelastomers may be comprised of at least two different
copolymerized monomers, different from each other and said cure
site monomer, selected from the group consisting of fluoromonomers,
hydrocarbon olefins and mixtures thereof. Fluoromonomers include
both fluorine-containing olefins (fluoroolefins) and
fluorine-containing vinyl ethers (fluorovinyl ethers). Specific
examples of fluoroelastomers that may be employed (cure site
monomers omitted for clarity) include, but are not limited to
copolymerized units of TFE/PMVE, VF.sub.2/PMVE, VF.sub.2/TFE/PMVE,
TFE/PMVE/E, TFE/P and TFE/P/VF.sub.2.
[0043] Examples of suitable cure site monomers include, but are not
limited to: i) bromine-containing olefins; ii) bromine-containing
vinyl ethers; iii) iodine-containing olefins; iv) iodine-containing
vinyl ethers; v) fluorine-containing olefins having a nitrile
group; vi) fluorine-containing vinyl ethers having a nitrile group;
and vii) non-conjugated dienes.
[0044] Brominated cure site monomers may contain other halogens,
such as fluorine. Examples of brominated olefin cure site monomers
are bromotrifluoroethylene (BTFE);
4-bromo-3,3,4,4-tetrafluorobutene-1 (BTFB); vinyl bromide;
1-bromo-2,2-difluoroethylene; perfluoroallyl bromide;
4-bromo-1,1,2-trifluorobutene-1;
4-bromo-1,1,3,3,4,4-hexafluorobutene;
4-bromo-3-chloro-1,1,3,4,4-pentafluorobutene;
6-bromo-5,5,6,6-tetrafluorohexene; 4-bromoperfluorobutene-1 and
3,3-difluoroallyl bromide. Brominated vinyl ether cure site
monomers may include 2-bromo-perfluoroethyl perfluorovinyl ether
and fluorinated compounds of the class
CF.sub.2Br--R.sub.f--O--CF.dbd.CF.sub.2 (R.sub.f is a
perfluoroalkylene group), such as
CF.sub.2BrCF.sub.2O--CF.dbd.CF.sub.2
CF.sub.2.dbd.CFOCF.sub.2CF.sub.2CF.sub.2OCF.sub.2CF.sub.2Br, and
fluorovinyl ethers of the class ROCF.dbd.CFBr or ROCBr.dbd.CF.sub.2
(where R is a lower alkyl group or fluoroalkyl group) such as
CH.sub.3OCF.dbd.CFBr or CF.sub.3CH.sub.2OCF.dbd.CFBr.
[0045] Suitable iodinated cure site monomers include iodinated
olefins of the formula: CHR.dbd.CH-L-CH.sub.2CHR--I, wherein R is
--H or --CH.sub.3; L is a C.sub.1-C.sub.18 (per)fluoroalkylene
radical, linear or branched, optionally containing one or more
ether oxygen atoms, or a (per)fluoropolyoxyalkylene radical as
disclosed in U.S. Pat. No. 5,674,959. Other examples of useful
iodinated cure site monomers are unsaturated ethers of the formula:
I(CH.sub.2CF.sub.2CF.sub.2).sub.nOCF.dbd.CF.sub.2 and
ICH.sub.2CF.sub.2O[CF(CF.sub.3)CF.sub.2O].sub.nCF.dbd.CF.sub.2, and
the like, wherein n=1-3, such as disclosed in U.S. Pat. No.
5,717,036. In addition, suitable iodinated cure site monomers
including iodoethylene, 4-iodo-3,3,4,4-tetrafluorobutene-1 (ITFB);
3-chloro-4-iodo-3,4,4-trifluorobutene;
2-iodo-1,1,2,2-tetrafluoro-1-(vinyloxy)ethane;
2-iodo-1-(perfluorovinyloxy)-1,1,-2,2-tetrafluoroethylene;
1,1,2,3,3,3-hexafluoro-2-iodo-1-(perfluorovinyloxy)propane;
2-iodoethyl vinyl ether; 3,3,4,5,5,5-hexafluoro-4-iodopentene; and
iodotrifluoroethylene are disclosed in U.S. Pat. No. 4,694,045.
Allyl iodide and 2-iodo-perfluoroethyl perfluorovinyl ether may
also be useful cure site monomers.
[0046] Useful nitrile-containing cure site monomers may include
those of the formulas shown below.
CF.sub.2.dbd.CF--O(CF.sub.2).sub.n--CN where n=2-12;
CF.sub.2.dbd.CF--O[CF.sub.2--CF(CF.sub.3)--O].sub.n--CF.sub.2--CF-
(CF.sub.3)--CN where n=0-4;
CF.sub.2.dbd.CF--[OCF.sub.2CF(CF.sub.3)].sub.x--O--(CF.sub.2).sub.n--CN
where x=1-2, and n=1-4; and
CF.sub.2.dbd.CF--O--(CF.sub.2).sub.n--O--CF(CF.sub.3)CN where
n=2-4.
[0047] Examples of non-conjugated diene cure site monomers include,
but are not limited to 1,4-pentadiene; 1,5-hexadiene;
1,7-octadiene; 3,3,4,4-tetrafluoro-1,5-hexadiene; and others, such
as those disclosed in Canadian Patent 2,067,891 and European Patent
0784064A1. A suitable triene is
8-methyl-4-ethylidene-1,7-octadiene.
[0048] Of the cure site monomers listed above, for situations
wherein the fluoroelastomer will be cured with peroxide, brominated
or iodinated cure such monomers such as
4-bromo-3,3,4,4-tetrafluorobutene-1 (BTFB);
4-iodo-3,3,4,4-tetrafluorobutene-1 (ITFB); allyl iodide;
bromotrifluoroethylene, or a nitrile-containing cure site monomer
such as perfluoro(8-cyano-5-methyl-3,6-dioxa-1-octene) may be used.
When the fluoroelastomer will be cured with a polyol, 2-HPFP or
perfluoro(2-phenoxypropyl vinyl) ether may be used. When the
fluoroelastomer will be cured with a tetraamine, bis(aminophenol)
or bis(thioaminophenol), a nitrile-containing cure site monomer
(e.g., 8-CNVE) may be used. When the fluoroelastomer will be cured
with ammonia or a compound that releases ammonia at curing
temperatures (e.g., urea), a nitrile-containing cure site monomer
(e.g., 8-CNVE) may be used. Further, it is also within the scope of
the present disclosure that other cure site monomers may be used,
where the silane coupling agent would possess the same type of
chemical moiety for its Q group as the selected cure site
monomer.
[0049] Some embodiments may involve a silane coupling agent having
a chemically identical Q group as the cure site moiety on the
polymer. Some embodiments may involve a silane coupling agent
having a chemically identical Q group as the pendant group of the
cure site monomer. Other embodiments may involve a silane coupling
agent having a chemically similar Q group as the pendant group of
the cure site monomer, i.e., if the cure site monomer is a
bromine-containing olefin, such as those described above, the Q
group may be any bromine-containing alkyl group.
[0050] In certain embodiments, fluoroelastomers can also be
produced in an emulsion polymerization process using a
water-soluble polymerization initiator and an excess amount of
surfactant. The resulting fluoroelastomer may exit the reactor in
the form of a latex which is degassed (e.g., freed from unreacted
monomers), coagulated, filtered and washed. Fluoroelastomers can
also be produced in a suspension polymerization process, where
polymerization is carried out by dispersing one or more monomers,
or an organic solvent with monomer dissolved therein, in water and
using an oil-soluble organic peroxide. No surfactant or buffer in
general is used and fluoroelastomer is produced in the form of
polymer particles which may be directly filtered, e.g., without the
need for coagulation, and then washed, thus producing a cleaner
polymer than that resulting from an emulsion process. Also, the
fluoroelastomer polymer chains are substantially free of ionic end
groups so that the Mooney viscosity is relatively low and the
polymer has improved processability compared to polymer produced by
an emulsion process.
[0051] In certain embodiments, perfluoroelastomers can be used with
the silane modified fillers described herein. Perfluoroelastomers
are generally amorphous polymeric compositions having copolymerized
units of at least two principal perfluorinated monomers. Generally,
one of the principal monomers is a perfluoroolefin while the other
is a perfluorovinyl ether. Representative perfluorinated olefins
include tetrafluoroethylene and hexafluoropropylene. Suitable
perfluorinated vinyl ethers include those of the formula
CF.sub.2.dbd.CFO(R.sub.mO).sub.n(R.sub.kO).sub.jR.sub.f where
R.sub.m and R.sub.k are different linear or branched
perfluoroalkylene groups of 2-6 carbon atoms, m, n and j are
independently 0-10, and R.sub.f is a perfluoroalkyl group having
1-6 carbon atoms. Perfluoroelastomers have achieved outstanding
commercial success and are used in a wide variety of applications
in which severe environments are encountered, in particular those
end uses where exposure to high temperatures and aggressive
chemicals occurs. For example, these polymers are often used in
seals for aircraft engines, in oil-well drilling devices, and in
sealing elements for industrial equipment used at high
temperatures. The outstanding properties of perfluoroelastomers can
be attributed to the stability and inertness of the copolymerized
perfluorinated monomer units that make up the major portion of the
polymer backbones in these compositions. Such monomers include
tetrafluoroethylene and perfluorinated vinyl ethers. In order to
develop elastomeric properties fully, perfluoroelastomers are in
general cross-linked, e.g., vulcanized. To this end, a small amount
of cure site monomer can be copolymerized with the perfluorinated
monomer units.
[0052] In other embodiments, poly(perfluoro-alkylene oxides)
terminated with polymerizable functional groups can be polymerized
to prepare certain polymers, e.g., polyurethanes, having low glass
transition temperatures and low-temperature flexibility. For
example, poly(perfluoroalkylene oxide) peroxides can be used with
ethylenically unsaturated monomers in making block copolymers
having good low-temperature flexibility. Fluorinated ethers with
nonfunctional terminal moieties are sold under the trademarks
"Krytox" and "Fomblin" for use as vacuum pump fluids, see e.g., G.
Caporiccio et al., 21 IND. ENG. CHEM. PROD. RES. DEV. 515-19
(1982).
[0053] In certain examples, compositions of fluoroelastomers
cross-linked with dihydroxypolyfluoroethers may be used. The
dihydroxypolyfluoroethers may contain either branched moieties, are
random copolymers containing --CF.sub.2O-- repeating units or
contain partially fluorinated repeat units. In other examples,
perfluoropolyether polymers may be prepared as described, for
example, in U.S. Pat. No. 5,026,786. These perfluoropolyethers
comprise randomly distributed perfluoroxyalkylene units. European
Pat. Pub. No. 222,201 describes vulcanizable rubber blends
comprising certain perfluoropolyether which can also be used with
the coupling agents described herein. These perfluoropolyethers
have brominated or fluorinated end groups. European Pat. Pub. No.
310,966 describes rubber blends comprising certain
perfluoropolyethers. These perfluoropolyethers comprise
perfluoroalkyl end groups.
[0054] In certain embodiments, certain classes of fluorinated ether
compositions comprising functional fluoroaliphatic mono- and
polyethers may be used, as described, for example, in U.S. Pat.
Nos. 5,384,374 and 5,266,650.
[0055] The polymers suitable for use with the silane modified
fillers including, but not limited to, fluoroelastomers,
perfluoroelastomers and the like, are commercially available from
numerous sources including, but not limited to, DuPont Performance
Elastomers LLC (Wilmington, Del.), DuPont-Mitsui Fluorochemicals
Co. (Japan), AGC Chemicals America (Exton, Pa.), Solvay Solexis
(Italy), Daikin Industries (Japan), Zeon Corporation (Japan),
Exfluor Research Corporation (Austin, Tex.) and other chemical
suppliers.
[0056] In preparing the compositions, the silane coupling agent may
be linked to the filler surface in a first step and the resulting
product can be reacted with the polymer in a second step. In other
examples, the silane coupling agent may be reacted with the polymer
in a first step and then reacted with the filler surface in a
second step. In yet other examples, the polymer, filler and silane
coupling agent may be mixed or blended together to provide a
composition that includes a polymer coupled to a filler through the
silane coupling agent. Notwithstanding the exact sequence of event
used, the resulting composition includes a filler covalently
coupled to a polymer through the silane coupling agent. An
illustration of the resulting composition is shown in FIG. 3.
[0057] In certain examples, free radicals are first generated using
suitable species such as, for example, branched alkyl molecules
including one or more heteroatoms such as, oxygen, nitrogen or
sulfur. In this initiation step, the free radicals may be generated
by exposing the alkyl molecules to light, heat, initiators such as
peroxides (organic peroxides which are particularly effective
curing agents for fluoroelastomers include dialkyl peroxides which
decompose at a temperature above 50.degree. C.), chlorine gas,
bromine or other commonly employed free radical initiators. The
formed free radicals may react with the silane-modified fillers to
form silane-modified fillers that include a free radical. The free
radical filler can react with the polymer in one or a series of
propagation steps to covalently couple the polymer to the silane
modified filler and/or to generate more free radicals. In one or
more termination steps, the free radical filler may react with
multiple polymer molecules and result in polymer being covalently
coupled to the filler through the silane coupling agent. Such free
radical reactions and conditions suitable for performing them will
be readily selected by the person of ordinary skill in the art,
given the benefit of this disclosure.
[0058] As mentioned above, curatives used in forming the present
compositions may include peroxides, amine curatives and polyhydroxy
(e.g., bisphenol) curatives. In general, the curative may be used
in amounts of from about 0.5-5 parts by weight per hundred parts by
weight resin (phr).
[0059] Example peroxide curatives may include tert-butylcumyl
peroxide (e.g., Trigonox.RTM. T),
2,5-dimethyl-2,5-di(t-butylperoxy)
hexyne-3,2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane (e.g.,
Trigonox.RTM. 101),
alpha,alpha-bis(tert-butylperoxy-isopropyl)benzene (Perkadox.RTM.
14/40 and Perkadox.RTM. 14 (without carrier)), and
2,5-dimethyl-2,5-di(t-butyl-peroxy)hexane (Varox..RTM. DBPH-50 or
Varox.RTM. DBPH (liquid form)).
[0060] A co-agent may be used in combination with the peroxide
curative. Some co-agents for peroxide curing of fluoroelastomers
include, but are not limited to, triallylisocyanurate (TAIC),
trimethallylisocyanurate (TMAIC) and triallylcyanurate (TAC),
triacrylformal, triallyl trimellitate,
N,N'-m-phenylenebismaleimide, diallyl phthalate,
tetrallylterephthalamide, tris(diallylamine)-s-triazine, triallyl
phosphate, N,N,N',N'-tetrallyl-malonamide; trivinyl-isocyanurate;
2,4,6-trivinyl-methyltrisiloxane;
N,N'bisallylbicyclo-oct-7-ene-disuccinimide (BOSA), and
N,N-diallylacrylamide. Generally, the co-agent may be used in an
amount of 0.1 to 10 parts by weight per 100 parts by weight of
resin.
[0061] Examples of amine curatives are organic aliphatic or
aromatic diamines such as ethylenediamine or hexamethylenediamine,
or their carbamates, hydrochlorides, oxalates, or reaction products
with hydroquinone. Specific examples include hexamethylene diamine
carbamate, such as DIAK (trademark of DuPont Dow Elastomers) no. 1,
dicinnamylidene diamine carbamate, such as DIAK no. 3, and
4,4'-bis(aminocyclohexyl)-methane carbamate, such as DIAK no. 4.
Examples of bisphenol curatives are fluorinated bisphenol A,
4,4'-hexafluoroisopropylidene diphenol (i.e., bisphenol AF) and
derivatives thereof. Other polyhydroxy compounds may also be
used.
[0062] In some instances, the compositions may be cured without the
addition of a curative, but by thermal curing. For example,
crosslinking may be thermally induced in nitrile-containing
elastomers by formation of a triazine ring, between nitriles in the
polymer and/or present within the Q group of a silane coupling
agent, as illustrated in FIG. 4.
[0063] Additional components may be used in or with the
polymer-silane coupling agent-filler composition. For examples,
additives, viscosity modifiers, processing aids and the like may be
used. Examples of such additional components include, but are not
limited to, antiozonants, antioxidants, plasticizers, resins, flame
retardants, lubricants, one or more curing agents such as, for
example, sulfur, sulfur donors, activators, accelerators,
peroxides, thickeners, thinners, solvents, salts and other
materials.
[0064] In processing the materials, various devices such as mills,
mixers, molds, calendering devices, extruders and the like may be
used. For example, the materials may be blended, open milled, mixed
with an internal mixer (which may include temperature control to
avoid scorching) or otherwise combined in a suitable device. One
pass or multi-pass mixing may be used. High shear mixing may be
used to obtain good dispersion. The materials may be reworked in
one or more additional stages to further assist in mixing.
Illustrative molding processes that may be used with the materials
include, but are not limited to compression, transfer and injection
molding, extrusion and calendering. In compression molding, a
preform may be used to provide a desired shape or mass to the
resulting material. In injection molding, the material may be
injected at high pressure into a mold. Calendering may be used to
produce sheets of material. The compounds for calendaring may be
used with viscosity modifiers to provide medium or low viscosity
materials to facilitate the calendaring process. The materials may
also be shaped by extrusion. For example, the material may be
forced through a shaping die below a curing temperature to impart a
desired shape. Release agents may be used in the preforms, molds
and other parts to facilitate removal of the compressed or produced
material from these devices.
[0065] The presence of a silane on the surface of the filler can
have a great effect on the filler dispersion and resulting
mechanical properties of the composition. FIGS. 5A, B and C are
schematic views of a polymer filled with the thermally stable
silane coupling agent modified silica at different filler
concentrations. FIG. 5A shows the local structure of one cluster
formed by primary silica aggregates. FIG. 5B shows aggregated
filler clusters below the gel point .PHI.*, and FIG. 5C shows
aggregated filler clusters above the gel point .PHI.*. By modifying
the surface of the filler with a silane, and subsequent coupling to
a polymer through the silane, a reduction in the Payne effect (also
known as the Fletcher-Gent effect) may be achieved. The Payne
effect is the non-linearity appearing at small strains (a few tens
to a few % strain) due to breakage of the filler three-dimensional
network. When the strain is removed or reduced back to the original
level, the network reforms and this process generates a hysteresis.
The hysteresis generates heat that can be detrimental for the
component lifetime. Adding a silane coupling agent to the filler
surface and covalently coupling the modified filler to the polymer
can reduce this hysteresis and therefore energy dissipation, which
in turn can increase the overall use life of the part or component
that is produced from the material.
[0066] In certain examples, the compositions disclosed herein may
be used in downhole tools and devices such as packers used in
extraction of fuels through a wellbore. For example, downhole
tools, such as modular wireline tools or drilling tools with
evaluation capabilities, that employ probes for engaging the
formation and establishing fluid communication may be used to make
the pressure measurements and acquire the fluid samples. Fluid in
general is drawn into the downhole tool through an inlet in the
probe. In some instances, such as for tight, low permeability,
formations, sampling probes are often replaced by dual inflatable
packer assemblies. Examples of such probe and packer systems are
depicted, for example, in U.S. Pat. Nos. 7,392,851, 7,363,970,
7,331,581, 6,186,227, 4,936,139, 4,860,581 and 4,660,637 and
assigned to Schlumberger, the entire contents of which are hereby
incorporated herein by reference for all purposes. In one
configuration, a packer comprises, for example, a resilient
element, a housing and a rupture disk. The resilient element is
adapted to seal off an annulus of the well when compressed, and the
housing is adapted to compress the resilient element in response to
a pressure exerted by fluid of the annulus on a piston head of the
housing. The housing includes a port for establishing fluid
communication with the annulus. The rupture disk is adapted to
prevent the fluid in the annulus from entering the port and
contacting the piston head until the pressure exerted by the fluid
exceeds a predefined threshold and ruptures the rupture disk. In
another configuration, dual packer elements may be used with either
or both of the packer elements comprising one or more of the
materials described herein. For example, packer elements may be
spaced apart along a downhole tool conveyed by a wireline in a
borehole penetrating a subsurface formation. Although a wireline
tool is illustrated, other downhole tools conveyed by drill string,
coiled tubing, etc., are also suited for such tasks. When inflated,
the packer elements cooperate to seal or isolate a section of the
borehole wall, thereby providing a flow area with which to induce
fluid flow from the surrounding formation(s). Other packers and
elements of packer assemblies may be produced using one or more of
the compositions described herein. In one embodiment, the
compositions may be used in a swellable packer for open-hole zonal
isolation. For example, a fluoroelastomer composition as described
herein can be used as the barrier coating for swellable materials
to slow down the rate of swelling.
[0067] In certain embodiments, the compositions disclosed herein
may be used to coat one or more devices such as, for example, a
coating on the stator or rotor of a mud motor. For example, the
composition may be used in a motor that imparts rotational drive to
a drilling assembly. Illustrative mud motors and assemblies using
them are described, for example in commonly assigned U.S. Pat. Nos.
7,289,285, 6,419,014, 5,727,641, 5,617,926, 5,311,952, the entire
disclosure of each of which is hereby incorporated herein by
reference for all purposes. Referring now to FIGS. 6 and 7, an
example mud motor using compositions of the present disclosure is
shown.
[0068] FIGS. 6 and 7 show details of the power section 18 of a
conventional downhole motor. The power section 18 generally
includes a tubular housing 22 which houses a motor stator 24 within
which a motor rotor 26 is rotationally mounted. The power section
18 converts hydraulic energy into rotational energy by reverse
application of the Moineau pump principle. The stator 24 has a
plurality of helical lobes, 24a-24e, which define a corresponding
number of helical cavities, 24a'-24e'. The rotor 26 has a plurality
of lobes, 26a-26d, which number one fewer than the number of stator
lobes and which define a corresponding plurality of helical
cavities 26a'-26d'. In accordance with embodiments, the stator 24
and/or rotor 26 are formed of an elastomeric material having a
composition of the present disclosure that provides the lobe
structure of the stator and/or rotor. The rotor and stator are
dimensioned to form a tight fit (i.e., very small gaps or positive
interference) under expected operating conditions, as shown in FIG.
6. Other embodiments may use an elastomeric rotor. The rotor 26 and
stator 24 form continuous seals along their matching contact points
which define a number of progressive helical cavities. When
drilling fluid (mud) is forced through these cavities, it causes
the rotor 26 to rotate relative to the stator 24. During drilling,
the mud motor elastomers in general experience severe mechanical
stress and deformation (mainly dynamic), aggressive downhole
fluids, and high temperature and high pressure. The compositions of
the present disclosure may possess silanes (and derived crosslinks)
having an improved thermal stability so that reinforcing effect of
the fillers will be present even at high temperatures (e.g.,
temperatures greater than 150.degree. C., which is considered the
upper limit for conventional elastomers used in mud motors).
[0069] In certain examples, the compositions described herein may
be used in a formation tester such as MDT (Modular Formation
Dynamics Tester) from Schlumberger, permeability probes, power
drive pads and other components and tools commonly used downhole
for oilfield and gas exploration.
[0070] When introducing elements of the examples disclosed herein,
the articles "a," "an," "the" and "said" are intended to mean that
there are one or more of the elements. The terms "comprising,"
"including" and "having" are intended to be open-ended and mean
that there may be additional elements other than the listed
elements. It will be recognized by the person of ordinary skill in
the art, given the benefit of this disclosure, that various
components of the examples can be interchanged or substituted with
various components in other examples.
[0071] Although certain aspects, examples and embodiments have been
described above, it will be recognized by the person of ordinary
skill in the art, given the benefit of this disclosure, that
additions, substitutions, modifications and alterations of the
disclosed illustrative aspects, examples and embodiments are
possible.
* * * * *