U.S. patent application number 11/970892 was filed with the patent office on 2009-01-15 for method of bonding perfluoroelastomeric materials to a surface.
This patent application is currently assigned to Greene, Tweed of Delaware, Inc.. Invention is credited to Ronald R. Campbell, Christopher Corrado, Carmin Quartapella, Gary Reichl, Robert Anthony Rey, Brian Alan Ux.
Application Number | 20090018275 11/970892 |
Document ID | / |
Family ID | 39674456 |
Filed Date | 2009-01-15 |
United States Patent
Application |
20090018275 |
Kind Code |
A1 |
Campbell; Ronald R. ; et
al. |
January 15, 2009 |
Method of Bonding Perfluoroelastomeric Materials to a Surface
Abstract
The invention includes a method of bonding a perfluoroelastomer
material to first surface that includes: (a) contacting a first
surface with a bonding agent comprising a curable perfluoropolymer
and a curing agent; (b) curing the bonding agent to form a
perfluoroelastomer material that is bonded to the first surface. In
the practice of such method, the bonding agent may be a solution
prepared by dissolving the curable perfluoroelastomer and the
curing agent in a solvent. In an embodiment of the invention, the
perfluoroelastomer material formed in step (b) is a coating layer
or, alternatively, the first surface is a surface of a
perfluoroelastomer member and the perfluoroelastomer material
formed is a perfluoroelastomer weld.
Inventors: |
Campbell; Ronald R.;
(Harleysville, PA) ; Corrado; Christopher;
(Hatfield, PA) ; Ux; Brian Alan; (Red Hill,
PA) ; Rey; Robert Anthony; (Schwenksville, PA)
; Reichl; Gary; (Coopersville, PA) ; Quartapella;
Carmin; (Schwenksville, PA) |
Correspondence
Address: |
FLASTER/GREENBERG P.C.;8 PENN CENTER
1628 JOHN F. KENNEDY BLVD., 15TH FLOOR
PHILADELPHIA
PA
19103
US
|
Assignee: |
Greene, Tweed of Delaware,
Inc.
Wilmington
DE
|
Family ID: |
39674456 |
Appl. No.: |
11/970892 |
Filed: |
January 8, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60897660 |
Jan 26, 2007 |
|
|
|
60897651 |
Jan 26, 2007 |
|
|
|
Current U.S.
Class: |
525/416 ;
156/327; 156/331.7; 427/331; 427/384; 525/540; 528/397 |
Current CPC
Class: |
B29K 2027/12 20130101;
C09J 171/00 20130101; B29C 65/4835 20130101; B29K 2027/18 20130101;
B29C 65/14 20130101; B29C 65/485 20130101; C08F 8/30 20130101; B29K
2995/0058 20130101; C08J 5/12 20130101; C08K 3/36 20130101; B29C
66/742 20130101; B29L 2031/26 20130101; B29C 65/526 20130101; B29C
65/7841 20130101; B29C 65/5057 20130101; C08J 2315/02 20130101;
B29C 65/52 20130101; B29L 2031/06 20130101; B29K 2305/12 20130101;
B29C 35/02 20130101; B29L 2031/7096 20130101; B29C 66/71 20130101;
B29C 66/5268 20130101; C08K 5/14 20130101; B29C 65/1406 20130101;
B29K 2027/18 20130101; B29K 2305/02 20130101; C08F 14/18 20130101;
B29K 2027/12 20130101; B29C 66/71 20130101; C08F 8/30 20130101;
B29C 66/71 20130101; B29C 66/5261 20130101; C08F 8/30 20130101;
B29C 66/1142 20130101; C09J 127/20 20130101; C08F 14/18 20130101;
B29C 65/523 20130101; B29C 65/1412 20130101; B29C 65/522 20130101;
B29K 2019/00 20130101 |
Class at
Publication: |
525/416 ;
156/327; 156/331.7; 427/331; 427/384; 528/397; 525/540 |
International
Class: |
C08L 101/04 20060101
C08L101/04; B32B 37/12 20060101 B32B037/12; C08G 73/00 20060101
C08G073/00; B05D 3/00 20060101 B05D003/00 |
Claims
1. A method of bonding a perfluoroelastomer material to first
surface comprising: (a) contacting a first surface with a bonding
agent comprising a curable perfluoropolymer and a curing agent; and
(b) curing the bonding agent to form a perfluoroelastomer material
that is bonded to the first surface.
2. The method of claim 1, wherein the bonding agent is a solution
prepared by dissolving the curable perfluoroelastomer and the
curing agent in a solvent.
3. The method of claim 2, wherein the solvent is a fluorinated
solvent.
4. The method of claim 2, wherein the perfluoroelastomer material
formed in step (b) is a coating layer.
5. The method of claim 2 wherein the bonding agent is prepared by a
method comprising: (i) forming a first solution of the curable
perfluoropolymer and a first solvent; (ii) forming a second
solution of the curing agent and a second solvent; and (iii)
combining the first solution and the second solution.
6. The method of claim 5, wherein the first solvent and the second
solvent are identical.
7. The method of claim 1, wherein the curing step (b) further
comprises heating for a time period sufficient to effectively cure
the perfluoroelastomer material.
8. The method of claim 1, wherein the curing step further comprises
heating to about 149.degree. C. (300.degree. F.).
9. The method of claim 1, wherein step (a) comprises spraying the
bonding agent onto the surface.
10. The method of claim 1, wherein the curable perfluoropolymer has
at least one curesite monomer comprising a cyano group.
11. The method according to claim 1, wherein the curing agent is
selected from the group consisting of a monoamidine, a
monoamidoxime, an aryldioxime, perfluorooctamidine,
heptafluorobutyrlamidine, a bisphenol or a derivative thereof, a
tetraphenyltin, a triazine, and a peroxide-based curing system.
12. The method of claim 1, wherein the first surface is a surface
of a perfluoroelastomer member and the perfluoroelastomer formed is
a perfluoroelastomer weld.
13. The method of claim 12, wherein step (a) further comprises
contacting the bonding agent to a second surface and step (c)
further comprises curing the bonding agent to form a
perfluoroelastomer weld between the first surface and the second
surface, wherein upon curing the perfluoroelastomer weld comprises
essentially the same perfluoroelastomer as the perfluoroelastomer
member.
14. The method of claim 13, further comprising post-curing the
perfluoroelastomer weld.
15. The method of claim 14, wherein the perfluoroelastomer weld is
about 95% cured.
16. The method of claim 14, wherein the perfluoroelastomer member
and the weld form a part and the method further comprises
post-curing the part.
17. The method of claim 13, wherein the bonding agent is produced
by the steps comprising: compounding a perfluoroelastomer
formulation to form a compound; and dissolving the compound in a
solvent to form a solution, wherein the bonding agent is contacted
with the first surface by coating the first surface with the
bonding agent.
18. A method of forming a perfluoroelastomer coating comprising (a)
dissolving a curable perfluoropolymer and a curing agent in a
solvent to form a solution, (b) applying the solution to a surface;
and (c) curing the perfluoropolymer to form a cured
perfluoroelastomeric coating on the surface.
19. The method according to claim 18, wherein step (c) comprises
heating the coating layer for a sufficient period of time to
effectively cure the perfluoropolymer.
20. The method according to claim 18, wherein the curing step
further comprises heating the coating layer to about 149.degree. C.
(300.degree. F.).
21. The method according to claim 18, wherein step (a) further
comprises (i) forming a first solution of the curable
perfluoropolymer and a first solvent; (ii) forming a second
solution of the curing agent and a second solvent; and (iii)
combining the first solution and the second solution.
22. The method according to claim 21, wherein the first solvent and
the second solvent are identical.
23. The method according to claim 18, wherein step (b) comprises
spraying the solution onto the surface.
24. The method according to claim 18, wherein the curable
perfluoropolymer has at least one curesite monomer comprising a
cyano group.
25. The method according to claim 18, wherein the curing agent is
selected from the group consisting of a monoamidine, a
monoamidoxime and an aryldioxime.
26. The method according to claim 25, wherein the curing agent is
perfluorooctanaidine or heptafluorobutyrlamidine.
27. The method according to claim 18, wherein the solution
comprises about 1% to about 25% by weight of the perfluoropolymer
based on the total weight of the solution.
28. The method according to claim 27, wherein the solution
comprises about 1% to about 10% by weight of the perfluoropolymer
based on the total weight of the solution.
29. The method according to claim 28, wherein the solution
comprises about 1% to about 5% by weight of the perfluoropolymer
based on the total weight of the solution.
30. The method according to claim 29, wherein the solution
comprises about 0.01% to about 5% by weight of the curing agent,
based on the total weight of the solution.
31. The method according to claim 30, wherein the solution
comprises about 0.01% to about 1.5% by weight of the curing agent
based on the total weight of the solution.
32. The method according to claim 31, wherein the solution
comprises about 0.25% to about 1% by weight of the curing agent
based upon total weight of the solution.
33. A coated substrate comprising a cured perfluoroelastomer
coating applied on at least one surface of the substrate.
34. The coated substrate according to claim 33, wherein the
perfluoroelastomer coating is formed by a curing reaction of a
curable perfluoropolymer and a curing agent in a solution applied
to the surface of the substrate.
35. The coated substrate according to claim 34, wherein the curable
perfluoropolymer has at least one curesite monomer having a cyano
group and the curing agent is a monoamidine, monoamidoxime or
aryldioxime.
36. The coated substrate according to claim 35, wherein the curing
agent is perfluorooctanamidine or heptafluorobutyrlamidine.
37. A method of bonding a perfluoroelastomer member to a surface,
comprising: (a) contacting a first surface of a perfluoroelastomer
member with a bonding agent comprising: a curable perfluoropolymer,
and a curing agent; (b) placing the bonding agent also in contact
with a second surface; and (c) curing the bonding agent to form a
perfluoroelastomer weld between the first and second surface,
wherein upon curing the perfluoroelastomer weld comprises
essentially the same perfluoroelastomer as the perfluoroelastomer
member.
38. The method of claim 37, further comprising post-curing the
perfluoroelastomer weld.
39. The method of claim 38, wherein the perfluoroelastomer weld is
about 95% cured.
40. The method of claim 38, wherein the perfluoroelastomer member
and the weld form a part and the method further comprises
post-curing the part.
41. The method of claim 40, wherein the part is a seal.
42. The method of claim 40, wherein the part is homogeneous.
43. The method of claim 38, wherein the perfluoroelastomer weld is
homogeneous with the perfluoroelastomer member.
44. The method of claim 38, wherein the first and second surfaces
are on the same perfluoroelastomer member.
45. The method of claim 38, wherein in step (a) the
perfluoroelastomer member is about 75% to about 95% cured.
46. The method of claim 37, wherein step (b) further comprises:
placing the first surface and the second surface within a fixture;
and positioning the first surface, the bonding agent and the second
surface within the fixture, such that the first surface, the
bonding agent and the second surface are in contact.
47. The method of claim 37, wherein step (c) further comprises
heating the bonding agent for a sufficient period of time to
effectively cure the bonding agent.
48. The method of claim 37, wherein step (c) further comprises
heating the perfluoroelastomer bonding agent to about 149.degree.
C. (300.degree. F.).
49. The method of claim 37, wherein the bonding agent further
comprises a solvent and the bonding agent is contacted with the
first surface by coating the first surface with the bonding
agent.
50. The method of claim 49, wherein the solvent is a fluorinated
solvent.
51. The method of claim 37, wherein the curing agent is at least
one of a bisphenol or a derivative thereof, a tetraphenyltin, a
triazine, and a peroxide-based curing system.
52. The method of claim 37, wherein the bonding agent is produced
by the steps comprising: compounding a perfluoroelastomer
formulation to form a compound; and dissolving the compound in a
solvent to form a solution, wherein the bonding agent is contacted
with the first surface by coating the first surface with the
bonding agent and the bonding agent is contacted with the first
surface by coating the first surface with the bonding agent.
53. The method of claim 52, wherein the step of dissolving
comprises: forming the compound into pieces; adding about 70% to
about 95% by weight solvent to the pieces of the compound, and
dispersing the particulates of the pieces while dissolving the
pieces on a ball mill.
54. The method of claim 52, wherein the solvent is added in an
amount of about 90% to about 95% by weight of the solution.
55. A method of bonding a perfluoroelastomer seal to a gland,
comprising: placing a bonding agent comprising a curable
perfluoropolymer and curing agent within gaps formed between a
perfluoroelastomer seal and a gland; and curing the bonding agent;
wherein upon curing, the perfluoropolymer forms essentially the
same perfluoroelastomer as the perfluoroelastomer seal.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application Nos. 60/897,660, filed Jan. 26, 2007 and 60/897,651,
filed Jan. 26, 2007, the contents of each of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] Perfluoroelastomers have readily been used to form various
types of O-rings or seals. Such seals are commonly manufactured by
first producing a complete mold for the seal in the desired seal
configuration and then compression molding a compound that includes
perfluoropolymers along with curing agents to form a completely
cured perfluoroelastomer seal or other part. However, with the
ever-increasing need for larger and larger seals or unusual
configurations, molding complete parts becomes more and more
expensive and less of an economical practicality. This is because
to form such parts requires not only the molds but also an
infrastructure sufficient to handle the large or unusually sized
molds, including presses and pumps related to molding
operations.
[0003] One approach developed to address this need has been to
produce seals from rod stock and splice the two rod stock ends
together to form the required size seal. Traditional splicing
techniques have not proven very successful with
perfluoroelastomers. Splicing with an adhesive provides a weak
point in the seal that is prone to attack because adhesives
developed in the past generally do not match the chemical
resistance of perfluoroelastomers.
[0004] Methods of bonding a cured perfluoroelastomer to itself
using a thermoplastic perfluoropolymer bonding agent have been
disclosed. However, such processes result in fusing of the
perfluoroelastomer ends leading to an intermediate fusing layer
i.e., a layer of fused perfluoropolymer. This provides a
non-homogenous section within the perfluoroelastomer part i.e., the
fused perfluoropolymer layer. Thus, the fused perfluoropolymer
could result in a "weak" point due to increased susceptibility to
chemical or physical attack, increased compression set and reduced
low temperature compliance than the rest of the perfluoroelastomer
seal material. There is, therefore, a need in the art for an
improved method of bonding and/or welding perfluoroelastomers and
parts formed from them that is simple and economical and provides
for a homogenous finished part that substantially retains the
strength of a solid finished piece.
[0005] In addition to the challenges associated with joining
perfluoroelastomer surfaces, it is noted that perfluoroelastomers,
by virtue of the manner in which they are typically cured and
formed as noted above, and their unique vulcanization properties
(included physical and solubility properties) have not, however,
been successfully adopted for certain uses and applications in
which their chemical resistance and elastomeric properties would
otherwise be advantageous, such as in surface passivation or other
coating use.
[0006] Whereas attempts have been made to dissolve curable
perfluoropolymers in fluorinated solvents, such as, Fluorinert.RTM.
FC-40, FC-75 and FC-77 to try to prepare coatings, the resulting
coatings are typically not resistant to flow or to certain
solvents, because the coatings were not cross-linked. Attempts to
incorporate curatives, such as, organic peroxides with associated
co-curatives; such as, triallyl isocyanurate (TAIC), were
unsuccessful due to the poor solubility of such
hydrocarbon-containing curatives in the highly fluorinated solvents
needed to dissolve the uncured perfluoropolymer. Likewise,
bisphenyl-based curatives, such as bisaminophenol (BOAP) typically
also exhibit poor solubility in such highly fluorinated solvents
needed to dissolve perfluoropolymers curable with BOAP such as
those with cyano-group containing curesite monomers.
[0007] This lack of the ability to cure high molecular weight
curable perfluoropolymers in solution has restricted the use of
perfluoroelastomer coatings to non-critical applications where
"flow" of the uncured material is acceptable.
[0008] Attempts have been made to form perfluoroelastomer coatings
in the past, however, the uses and particular perfluoropolymer
systems formed into coatings are limited. U.S. Pat. No. 6,523,650
provides one example of use of a perfluoroelastomer coating on an
electrostatic printing component as an outer coating. The patent
describes dissolving an elastomeric DuPont Kalrez.RTM.
perfluoroelastomer, derived from 3-phenoxypropylvinyl ether and at
least one fluorine-containing ethylenically unsaturated monomer, in
solvent and applying it as a coating. However, the patent does not
describe whether the perfluoroelastomer is in a cured state upon
dissolution and/or how the cure system is affected by
dissolution.
[0009] U.S. Pat. No. 5,268,002 teaches coating of pellicles for
photomask applications with a coating formed of a low molecular
perfluoroelastomer polymer that acts as an antireflective coat for
the pellicles. Such pellicles have a core layer of a polymer, such
as nitrocellulose, among others. The perfluoroelastomer polymers
include tetrafluoroethylene (TFE), perfluoroalkylvinyl ether (PAVE)
and a curesite monomer such as
perfluoro-(8-cyano-5-methyl-3.6-dioxa-1-octene) (8-CNVE). The
patent uses such polymers to form low molecular weight
perfluoroelastomers having these components by pyrolyzing the
elastomer noted above and then dissolving the low molecular weight
polymer in a fluorocarbon solvent such as Fluorinert.RTM. FC-40,
Fluorinert.RTM. FC-75 or Fluorinert.RTM. FC-77. The pyrolysis
enhances the solubility to enable the resulting materials to be
used in coating form. See also, U.S. Pat. No. 5,256,747.
[0010] Moreover, there is a need in the art for an easy-to-form
surface coating that can incorporate the advantages of a standard
perfluoroelastomeric coating (as opposed to a low molecular weight
coating), including allowing for use of a standard cure system and
final cured perfluoroelastomer compound without complex process
steps, while maintaining desired coating properties suitable for
use on process equipment and the like and a process for preparing
the same. The invention disclosed herein addresses this need and
the need for a method of perfluoroelastomer joining or splicing
disclosed above.
BRIEF SUMMARY OF THE INVENTION
[0011] Included within the several embodiments of the invention is
a method of bonding a perfluoroelastomer material to first surface
that includes: (a) contacting a first surface with a bonding agent
comprising a curable perfluoropolymer and a curing agent; and (b)
curing the bonding agent to form a perfluoroelastomer material that
is bonded to the first surface. In the practice of such method, the
bonding agent may be a solution prepared by dissolving the curable
perfluoroelastomer and the curing agent in a solvent. In an
embodiment of the invention, the perfluoroelastomer material formed
in step (b) is a coating layer or, alternatively, the first surface
is a surface of a perfluoroelastomer member and the
perfluoroelastomer material formed is a perfluoroelastomer
weld.
[0012] In one embodiment of the method, the first surface is a
surface of a perfluoroelastomer member, the bonding agent is also
contacted to a second surface and step (c) further includes curing
the bonding agent to form a perfluoroelastomer weld between the
first surface and the second surface. Upon curing, the
perfluoroelastomer weld includes essentially the same
perfluoroelastomer as the perfluoroelastomer member.
[0013] An embodiment of the invention also includes method of
forming a perfluoroelastomer coating that includes: (a) dissolving
a curable perfluoropolymer and a curing agent in a solvent to form
a solution, (b) applying the solution to a surface; and (c) curing
the perfluoropolymer to form a cured perfluoroelastomeric coating
on the surface. Additionally, coated substrates including a cured
perfluoroelastomer coating applied on at least one surface of the
substrate are also within the scope of the invention.
[0014] In another embodiment of the invention a method of bonding a
perfluoroelastomer member to a surface is disclosed. The method
includes (a) contacting a first surface of a perfluoroelastomer
member with a bonding agent comprising: a curable perfluoropolymer,
and a curing agent; (b) placing the bonding agent also in contact
with a second surface; and (c) curing the bonding agent to form a
perfluoroelastomer weld between the first and second surface,
wherein upon curing the perfluoroelastomer weld comprises
essentially the same perfluoroelastomer as the perfluoroelastomer
member.
[0015] In another embodiment, a method of bonding a
perfluoroelastomer seal to a gland is disclosed and includes
placing a bonding agent comprising a curable perfluoropolymer and
curing agent within gaps formed between a perfluoroelastomer seal
and a gland; and curing the bonding agent; wherein upon curing, the
perfluoropolymer forms essentially the same perfluoroelastomer as
the perfluoroelastomer seal.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0016] FIG. 1 is a flowchart of a method embodiment of forming a
perfluoroelastomer coating;
[0017] FIG. 2 is an enlarged perspective for cross-sectional view
of a perfluoroelastomer coating made in accordance with an
embodiment of the present invention;
[0018] FIGS. 3a and 3b are perspective views of a conventional rod
stock material;
[0019] FIG. 4 is a perspective view of an embodiment of a splicing
fixture of the present invention;
[0020] FIG. 4a is a partial, enlarged, exploded side elevational
view of the rod stock material in FIG. 3a;
[0021] FIG. 4b is a partial cross-sectional view of the rod stock
material in FIG. 4a taken along line 4b-4b in FIG. 4;
[0022] FIG. 5 is a plan view of a perfluoroelastomer seal within a
gland;
[0023] FIG. 5a is a cross-sectional view of the perfluoroelastomer
seal of FIG. 5;
[0024] FIG. 6 is a flowchart of a method of bonding a
perfluoroelastomer;
[0025] FIG. 7 is a flowchart of a method of bonding a
perfluoroelastomer seal to a gland; and
[0026] FIG. 8 is large perfluoroelastomer seal made in accordance
with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0027] Described herein are methods of bonding a perfluoroelastomer
material to first surface and, optionally, a second surface. Also
included are articles, such as seals and coated substrates that are
made using the methods. A perfluoroelastomer material, as used
herein, may be any cured elastomeric material derived by curing a
perfluoroelastomer (as defined herein) that includes a curable
perfluoropolymer having a crosslinking group to permit cure. A
perfluoroelastomer is substantially fluorinated, and preferably
completely fluorinated with respect to the carbon atoms on the
backbone of the perfluoropolymer. It will be understood that some
residual hydrogen may be present in perfluoroelastomers within the
crosslinks due to use of hydrogen in the functional crosslinking
group in some perfluoroelastomer formulations. In general,
perfluoroelastomers, once cured are used, for example, as
cross-linked polymeric formed articles such as seals.
[0028] The perfluoropolymers used to form perfluoroelastomer
material upon cure are themselves formed by polymerizing one or
more perfluorinated monomers, one of which is preferably a
perfluorinated curesite monomer having a functional group to permit
curing.
[0029] As used herein, a perfluoroelastomer is a polymeric
composition that includes a curable perfluoropolymer formed by
polymerizing two or more perfluorinated monomers, including at
least one perfluorinated monomer that has at least one functional
group to permit curing i.e., at least one curesite monomer. Such
perfluoroelastomer can include two or more of various
perfluorinated copolymers of at least one fluorine-containing
ethylenically unsaturated monomer, such as tetrafluoroethylene
(TFE), a perfluorinated olefin, such as hexafluoropropylene (HFP),
and a perfluoroalkylvinyl ether (PAVE) which includes alkyl groups
that are straight or branched and which include one or more ether
linkages, such as perfluoro(methyl vinyl ether), perfluoro(ethyl
vinyl ether), perfluoro(propyl vinyl ether) and similar compounds.
Useful examples of PAVEs include those described in U.S. Pat. No.
5,001,278, and in WO 00/08076, of which the disclosures related to
types of PAVEs are herein incorporated by reference. Other suitable
PAVEs are described, for example, in U.S. Pat. No. 5,696,189 and
4,983,697, of which the disclosures related to types of PAVEs are
also herein incorporated by reference.
[0030] Preferred perfluoropolymers are those which meet the
industry accepted definition of a perfluoroelastomer listed as an
FFKM in ASTM D-1418-05 and, are also preferably terpolymers or
tetrapolymers of TFE, PAVE, and at least one perfluorinated cure
site monomer which incorporates a functional group to permit
crosslinking of the terpolymer, at least one of which is a curesite
capable of being cured by the curatives described herein.
[0031] Preferred perfluoroelastomer polymers for use in the present
invention are either commercially available as curable
perfluoropolymers or are known to be manufactured and/or sold by
Daikin Industries, Inc., Solvay Solexis, Dyneon, E.I. Du Pont de
Nemours, Inc., Federal State Unitary Enterprise S. V. Lebedev
Institute of Synthetic Rubber in Russia, and Nippon Mektron in
Japan.
[0032] In an embodiment, the invention includes perfluoroelastomer
materials that are perfluoroelastomer coatings, and methods of
manufacturing such coatings, and perfluoroelastomer materials that
are welds acting to connect or splice a first surface to a second
surface.
[0033] Embodiments including these are formed, in part, by cure of
a perfluoroelastomer by a curing agent. Preferred are
peroxide-curable systems as well as cyano-curable systems. With
regard to peroxide-curable systems, preferred polymers include
terpolymers of TFE, PAVEs such as those described in U.S. Pat. No.
5,001,278 (incorporated herein in relevant part reference), and a
curesite monomer having a perfluorinated structure with a
peroxide-curable functional group including those known or to be
developed in the art, such as halogenated alkyl and other
derivatives, and partially- or fully-halogenated hydrocarbon
groups.
[0034] Regarding cyano-curable systems, most preferred are
perfluoropolymers as described in WO 00/08076, incorporated herein
by reference or other similar structures. The monomers in the
tetrapolymer of WO 00/08076 include tetrafluoroethylene,
perfluoromethylvinyl ether and two curesite monomers, a secondary
cyano curesite monomer,
CF.sub.2.dbd.CFO(CF.sub.2).sub.3OCF(CF.sub.3)CN and a primary cyano
curesite monomer,
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.2CN. Preferred
compounds are those having a Mooney viscosity (measured at
100.degree. C. on a TechPro.RTM. viscTECH TPD-1585 viscometer) of
about 45 to about 95, and preferably of about 45 to about 65.
[0035] Primary curing agents for are peroxide-based cure systems
may be any known peroxide curing and co-curing agents known or to
be developed in the art, such as organic and dialkyl peroxides. For
the cyano-based polymers, preferred primary curing agents include
monoamidines and monoamidoximes as described as U.S. Patent
Publication No. US-2004-0214956-A1, the disclosure of which is
incorporated herein by reference in relevant part. While such
monoamidines and monoamidoximes are described as potential cure
accelerators or as curatives in the prior art, in the present
invention they are preferably used as primary curing agents.
[0036] The amidine-based and amidoxime-based materials include
monoamidines and monoamidoximes of the following formula (I)
described further below. Preferred monoamidines and monoamidoximes
may be represented by formula (I):
##STR00001##
[0037] wherein Y may be a substituted alkyl, alkoxy, aryl, aralkyl
or aralkoxy group or an unsubstituted or substituted fully or
partially halogenated alkyl, alkoxy, aryl, aralkyl or aralkoxy
group having from about 1 to about 22 carbon atoms. Y may also be,
and preferably is, a perfluoroalkyl, perfluoroalkoxy,
perfluoroaryl, perfluoroaralkyl or perfluoroaralkoxy group of from
1 to about 22 carbon atoms and more preferably a perfluoroalkyl or
perfluoroalkoxy group of from about 1 to about 12 carbon atoms, and
more preferably from 1 to 9 carbon atoms; and R.sup.1 may be
hydrogen or substituted or unsubstituted lower alkyl or alkoxy
groups of from one to about 6 carbon atoms, oxygen (such that
NHR.sup.1 is a NOH group) or an amino group. R.sup.2 may be
independently any of the groups listed above for R1 or hydroxyl.
Substituted groups for Y, R.sup.1 or R.sup.2 include, without
limitation, halogenated alkyl, perhalogenated alkyl, halogenated
alkoxy, perhalogenated alkoxy, thio, amine, imine, amide, imide,
halogen, carboxyl, sulfonyl, hydroxyl, and the like. If R.sup.1 and
R.sup.2 are both selected as oxygen and hydroxyl, such that there
are two NOH groups on the compound (a dioxime can be used), and in
that case, formula (I) can be further modified to accommodate a
dioxime formula in which the carbon atom and the Y group together
form an intervening aromatic ring and in which the NOH groups are
located ortho-, para- or meta- to one another on the ring, such as
with p-benzoquinonedioxime.
[0038] Preferred embodiments include those according to formula (I)
in which R.sup.2 is hydroxyl, hydrogen or substituted or
unsubstituted alkyl or alkoxy groups of from 1 to 6 carbon atoms,
more preferably hydroxyl or hydrogen. Also preferred are
embodiments in which R.sup.1 is hydrogen, oxygen, amino or a
substituted or unsubstituted lower alkyl of from 1 to 6 carbon
atoms while R.sup.2 is hydrogen or hydroxyl. Most preferred are
embodiments where R.sup.1 and R.sup.2 are both hydrogen. Further
preferred embodiments include those in which Y is perfluoroalkyl,
perfluoroalkoxy, substituted or unsubstituted aryl groups and
substituted or unsubstituted halogenated aryl groups having the
chain lengths as noted above, particularly preferred are when
R.sup.1 and R.sup.2 are both hydrogen and Y is
CF.sub.3(CF.sub.2).sub.2-- (i.e., when the compound is
heptafluorobutyrlamidine) or a similar amidoxime compound.
[0039] Exemplary monoamidine-based and monoamidoxime-based
curatives according to formula (I) include perfluoroalkylamidines,
arylamidines, perfluoroalkylamidoximes, arylamidoximes and
perfluoroalkylamidrazones. Specific examples include
perfluorooctanamidine, heptafluorobutyrylamidine, benzamidine,
trifluoromethylbenzamidoxime, and trifluoromethoxybenzamidoxime,
with heptafluorobutyrlamidine being most preferred. Curatives as
noted according to formula (I) may be used alone or in
combinations, such as in combinations of preferred and/or exemplary
compounds noted hereinabove or with secondary curatives.
[0040] The curatives according to formula (I) are preferably
capable of curing perfluoroelastomeric compositions, particularly
those with at least one cyano curesite monomer.
[0041] Other curative (curing agents) may include
perfluoroelastomer formulations can include bisphenols and their
derivatives, tetraphenyltin, triazine, peroxide-based curing
systems (e.g., organic peroxides such as dialkyl peroxides), or
combinations thereof. Other suitable curing agents include
oganometallic compounds and the hydroxides thereof, especially
organotin compounds, including ally-, propargyl-, triphenyl- and
allenyl tin, curing agents containing amino groups such as diamines
and diamine carbamates, such as
N,N'-dicinnamylidene-1,6-hexanediamine, trimethylenediamine,
cinnamylidene trimethylenediamine, cinnamylidene ethylenediamine,
and cinnamylidene hexamethylenediamine, hexamethylenediamine
carbamate, bis(4-aminocyclohexly)methane carbamate,
1,3-diaminopropane monocarbamate, ethylenediamine carbamate,
trimethylenediamine carbamate, bisaminothiophenols, bisamidoximes,
and bisamidrazones. Most preferably a peroxide cure system
(including any necessary co-agents) is used.
[0042] The curing system does not require, but may also optionally
include a variety of secondary curatives, such as bisphenyl-based
curatives and their derivatives, tetraphenyltin, triazine,
peroxide-based curing systems (e.g., organic peroxides such as
dialkyl peroxides) (if not used as a primary agent or if used in a
combination of peroxides, or combinations of these systems. Other
suitable secondary curing agents include oganometallic compounds
and the hydroxides thereof, especially organotin compounds,
including ally-, propargyl-, triphenyl- and allenyl tin, curing
agents containing amino groups such as diamines and diamine
carbamates, such as N,N'-dicinnamylidene-1,6-hexanediamine,
trimethylenediamine, cinnamylidene trimethylenediamine,
cinnamylidene ethylenediamine, and cinnamylidene
hexamethylenediamine, hexamethylenediamine carbamate,
bis(4-aminocyclohexly)methane carbamate, 1,3-diaminopropane
monocarbamate, ethylenediamine carbamate, trimethylenediamine
carbamate, and bisaminothiophenols.
[0043] Other optional additives for use with the various
perfluoroelastomer formulations can include the addition of fillers
such as graphite, carbon black, clay, silicon dioxide, polymeric
graphite, fluoropolymeric particulates (e.g., TFE homopolymer and
copolymer micropowders), barium sulfate, silica, titanium dioxide,
acid acceptors, cure accelerators, glass fibers, or polyaramid
fiber such as Kevlar.RTM., plasticizers, or other additives known
or to be developed in the perfluoroelastomeric art. However, it is
preferred for coating compositions used in semiconductor and other
particulate-sensitive applications, that such optional fillers not
be used, or that clean fillers (silica, barium sulfate or
fluoropolymer particulates) be used.
[0044] The bonding agent, which bonds to the first and/or to the
second surface (particularly for forming a weld-type connection),
includes a curable perfluoropolymer and a curing agent. The
components of the bonding agent may be individually dissolved and
then combined followed by an in situ curing cycle. However, it is
also within the scope of the invention to first compound the
components and then dissolve the compound in a solvent. Methods of
compounding bonding agent components may be according to any known
technique in the art or any to be developed and a detailed
explanation of the compounding and processing methods are not
necessary for a complete understanding of the present invention.
For example, conventional methods of compounding are described in
International Plastics Handbook, 3.sup.rd Edition, Saechtling, p.
54-55. However, it is preferred that the primary individual
components are each first dissolved in a solvent(s) prior to
combination.
[0045] In dissolving the components or formulation, the preferred
solvent for dissolution of the curable perfluoropolymer is a
fluorosolvent that is able to dissolve at least the curable
perfluoropolymer component, and more preferably, that is able to
also dissolve the curative(s). Solvents having the desired
characteristics are known in the art and include Fluorinert.RTM.
FC-87, FC-84, FC-75, FC-77 and/or FC-43, commercially available
from 3M and any similar solvents. However, it should be understood
that while such fluorinated solvents are preferred, any solvent
which is known or to be developed, that is capable of dissolving
the compounded curable perfluoropolymer, and preferably the
curative and/or the primary components in the compounded
perfluoroelastomer formulation (i.e., the perfluoropolymer and the
curative aside from any additives) may be used within the scope of
this invention.
[0046] Preferably the total amount of solvent to be used is about
70% to about 95% by weight, more preferably about 90% to about 95%
by weight, and most preferably about 94% to about 95% by weight of
the finished solution prior to cure.
[0047] The curable perfluoropolymer is preferably present in a
finished solution in an amount about 1% to about 25% by weight,
more preferably about 1% to about 10% by weight, and most
preferably about 1% to about 5% by weight, based on the total
weight of the finished solution. The curing agent is preferably
present in an amount of about 0.01% to about 5%, more preferably
about 0.01% to about 1.5%, and most preferably about 0.25% to about
1% based upon total weight of the finished solution prior to cure.
It is preferred that the weight percentage ratio of
perfluoropolymer to curing in the finished solution be about 30:1
to about 10:1, and more preferably about 20:1.
[0048] In making the finished solution, the bonding agent may be
initially compounded to form a compounded bonding agent and then
dissolved in solvent in accordance with the above preferred
percentages. In such a method, the compounded fluoropolymer might
first be formed into small pieces by, for example, a clicker die,
although any other die cutter, knife, scissor, or similar cutting
apparatus suitable for the intended use can be used. Preferably the
pieces range from about 0.010 inches to about 0.250 inches in size
and more preferably about 0.030 inches on average. The pieces can
optionally be ground into finer sized pieces. Preferably, the
pieces are then added to a solvent, such as those mentioned above,
and then mixed. Mixing the pieces in the presence of a solvent, for
example on a ball mill, facilitates the dissolution of the
perfluoropolymer formulation into the solvent.
[0049] More preferably, each of the primary components of the
bonding agent is first dissolved in solvent. In such a method, a
first solution (solution A) is formed by combining the curable
perfluoropolymer with a solvent in an amount of about 2 to about
50% by weight curable perfluoropolymer, more preferably 2 to 20% by
weight and most preferably 5 to 10% by weight based on the total
weight of the first solution. A separate solution (solution B) is
formed by combining the cure agents with a solvent in an amount of
about 0.02% to about 10%, more preferably about 0.02% to about 3%,
and most preferably about 0.50% to about 2% based on the total
weight of the second solution. Then the two solutions are
subsequently combined by taking equal parts of each solution and
combining them to achieve the desired percentage of the curable
perfluoropolymer and curative(s) in the finished solution. If
additives are used, they may be added in either of the two initial
solutions or in the finished solution in accordance with this
particular method.
[0050] In an embodiment where the bonding agent is applied to the
surface of a perfluoroelastomer member, the bonding agent of the
present embodiment is made using the same or substantially the same
perfluoroelastomer formulation as used to produce the rod stock to
which it is to be welded. In the present embodiment, the bonding
agent can include any of the compounded perfluoroelastomer
formulations as described above, which include a curative(s).
[0051] In an embodiment, the invention includes a method of bonding
a perfluoroelastomer material to a first surface by contacting a
first surface with a bonding agent comprising a curable
perfluoropolymer and a curing agent and curing the agent to form a
perfluoroelastomer material that is bonded to the first surface
such that the perfluoroelastomer material formed is a coating
layer. In such embodiments, the bonding agent may be a solution
that can be applied to a surface of a substrate by any number of
conventional means such as spray coating, dip coating, brushing,
layering, and the like. With reference to FIG. 2, a coated
substrate, generally referred to as 10, is formed by applying the
finished solution to an uncoated substrate 12. Once the bonding
agent solution is applied, it is cured in situ to form a coating
14. Once the substrate is coated a heat cycle is applied. The heat
cycle will vary depending upon the specific perfluoroelastomer
formulation used for the curing agent, however the heat cycle can
be configured to provide a sufficient amount of heat for a
sufficient amount of time to effectively cure the bonding agent.
Alternative curing can be used including ultraviolet, infrared or
other radiative curing methods as well as optional use of pressure.
While the invention should not be restricted to any specific cure
or cure cycle, it is preferred that heat is used at about
149.degree. C. (300.degree. F.) for about eight minutes. However,
the curing temperature will vary depending upon the type of
perfluoropolymer and curing agent used in the perfluoroelastomer
formulation. Such curing temperatures can range from about
138.degree. C. (280.degree. F.) to about 177.degree. C.
(350.degree. F.), and preferably about 149.degree. C. (300.degree.
F.) to about 177.degree. C. (350.degree. F.). One of ordinary skill
in the art will understand that curing conditions vary with
elastomer systems and that such temperature ranges are not intended
to be limiting with respect to the scope of the invention, since a
variety of perfluoroelastomer formulations can be used.
[0052] After heat curing, post curing may optionally, but not
necessarily be applied at about 180.degree. C. (356.degree. F.) or
other suitable post-cure temperature for about seven to eight hours
or other suitable cure cycle times, depending on the resulting
properties desired. An additional cool down time of one hour can
then optionally be applied.
[0053] Although the present embodiment has been described for
coating a single substrate, the process may also be used to bond
two substrates together as an adhesive or bonded layer formed in
situ between two opposing surfaces (not shown) such as in a
laminated or other multi-layered structure. It may also be used to
bond on three-dimensional, non-planar surfaces.
[0054] The application of the present embodiment is not limited to
any particular substrate surface type, but instead can be used to
form a perfluoroelastomer coating on any type of solid surface.
Such perfluoroelastomer coatings can be used to coat foamed
materials, metals, metal alloys, glass, elastomers, plastics,
composites and the like. As a result of the uniquely elastomeric
and inert character of such coatings, they have application in a
wide variety of areas, including, semiconductor processing parts,
doors, and equipment; surface passivation; handling or mechanical
tools; medical equipment and devices; automotive and aerospace
parts and surfaces, equipment subject to high corrosion (e.g., oil
field and catalytic process equipment) and the like. In addition,
the coatings as formed are highly chemically inert and
insoluble.
[0055] The coatings may also be used to affect a seal in
applications in which the features are too small for conventional
molded seal parts, such as in "lab-on-a-chip" applications in which
a very thin silica or plastic layer must be sealed with a heat- and
chemically-resistant material. The material coatings may also be
used as sealants on metal surfaces such as those in aircraft engine
parts where in-service use conditions exceed the temperature range
for other elastomers such as nitriles or standard fluoroelastomers
(such as Viton.RTM.).
[0056] When pressures or temperatures exceed the capabilities of
typical elastomer seals, there are current uses involving
metal-to-metal seals. However, these seals must be highly polished
to affect a seal. It substantially increases the cost of forming
such seals. However, application of a thin coating as described
herein on such a substrate can affect a seal between metal parts
using a less polished and less expensive metal surface.
[0057] Such solutions and cured coatings can also be used to repair
or adhere to surfaces of expensive perfluoroelastomer molded parts
(such as O-rings, seals, gaskets and the like).
[0058] In an embodiment, the present invention provides for a
method (as illustrated in FIG. 6) of bonding perfluoroelastomer
("FFKM") members, for example to form a seal (e.g., an O-ring or
similar shaped seal) out of rod stock. The term "rod stock" as used
herein means any preformed stock material, regardless of shape or
cross-sectional configuration that can be used to make a seal.
[0059] The rod stock 11, 20 (FIGS. 3a and 3b) is pre-formed using
any conventional molding process such as extrusion or compression
molding. Such molding processes are well known in the art and a
detailed explanation of them is not necessary for a complete
understanding of the present invention. During the pre-form
process, which is typically extrusion, some heat applied to the
mold at least partially cures the compounded perfluoroelastomer
formulation transforming the perfluoropolymer into at least
partially cured perfluoroelastomer. The remaining curing typically
occurs during post pre-form processes, such as press-molding or
oven post-cure.
[0060] With reference to FIGS. 3a and 3b, the perfluoroelastomer
pre-form or rod stock 11, 20 (as illustrated in FIGS. 3a and 3b) is
initially formed from a compounded perfluoroelastomer formulation.
Preferably the perfluoroelastomer rod stock 11, 20 is at least
about 25% to about 95% cured. Methods of compounding
perfluoroelastomer formulations may be according to any known
technique in the art or any to be developed and a detailed
explanation of the compounding and processing methods are not
necessary for a complete understanding of the present invention.
For example, conventional methods of compounding are described in
International Plastics Handbook, 3.sup.rd Edition, Saechtling, p.
54-55, the contents of which are incorporated herein.
[0061] The rod stock 11 has a first end 13a with a preferred
cross-sectional surface 15 in a shape which is generally circular.
The cross-sectional shape can alternatively be any other shape
consistent with the intended use such as an oval, square,
rectangle, or the like. The rod stock 11 also has a second end 13b
with a cross-sectional surface 15 with a generally circular
shape.
[0062] As used herein, the term "weld" is meant to broadly
encompass any joining together of two surfaces through use of a
bonding agent therebetween, whether in liquid or solid "plug" form,
physically and preferably using curable chemical crosslinking
and/or bonding between each of the two opposing surfaces to be
welded and the bonding agent, however, it should be understood that
the two opposing surfaces need not be formed of the same material.
The first end 13a of the rod stock 11 can be welded to the second
end 13b of rod stock 11 to form a circular ring. Alternatively, the
first end 13a can be welded to a second rod stock 20 having ends
22a, 22b (as shown in FIG. 3a) which can be formed from the same
perfluoroelastomer formulation as rod stock 11. The weld for
joining various ends of perfluoroelastomer rod stock is formed by
coating or applying at least one end of the rod stock with a
bonding agent.
[0063] The bonding agent, either in the form of an extruded preform
of the perfluoroelastomer formulation to form a solid "plug" or in
the form of a solution of the compounded perfluoroelastomer
formulation is employed. As a solution, it is applied to the
surface of the rod stock 11. The bonding agent is then contacted
with at least one of the surfaces to be welded. It can be applied
in liquid form as a coating to a single surface such as 13a, or
both opposing surfaces, such as 13a, 13b or 22a, 22b, that are to
be welded together. As a solid "plug," it can be merely inserted
between two surfaces to be welded in a manner such that the plug
will contact the surfaces upon later curing and processing. As a
plug, the preform is situated next to, for example, a rod stock 11
surface, preferably contacting the surface.
[0064] In operation, when using a bonding agent in solution to weld
two ends of perfluoroelastomer rod stock together, for example to
form an O-ring, at least one surface of one of the ends e.g., 13a
is initially coated with the bonding agent. The coating can be
applied by any number of conventional means such as spray coating,
dip coating, brushing, layering, and the like. The second end 13b
of the rod stock 11 may also optionally be coated with the bonding
agent when welding two ends of the same rod stock. The two ends of
the coated rod stock 13 are then placed in a fixture 30 (e.g., a
splicing fixture as shown in FIG. 4) to secure one end 13a adjacent
to or in contact with the second end 13b of the rod stock 10 (as
shown in FIG. 4a). The fixture 30 can be configured to accommodate
the rod stock 11 for size and alignment and to allow heat and
pressure to be exerted on the rod stock 11 to hold them in place
within the fixture 30. The heat and pressure are generally supplied
by a press, in which the fixture is mounted and operated. The
fixture 30 can optionally act to apply a heat cure cycle to the
bonding agent.
[0065] The fixture 30 includes a bottom portion 32 and a top
portion 34. The top 34 and bottom 32 portions include channels 36a,
36b respectively for seating the rod stock material. A hinge 38
connects the top 34 and bottom 32 portions to allow the fixture 30
to open and close and to align the top and bottom portions of the
channel 36a, 36b.
[0066] After placing the coated rod stock 10 in the fixture 30, the
fixture 30 is closed and a heat cycle is applied. The heat cycle
will vary depending upon the specific perfluoroelastomer
formulation used for the curing agent, however the heat cycle can
be configured to provide a sufficient amount of heat for a
sufficient amount of time to effectively cure the bonding agent. An
effectively cured bonding agent is one that results in at least a
partially cured perfluoroelastomer (preferably one which is cured
greater than about 75%). The bonding agent is typically cured about
75% to about 95%, or up to about 99%. In the present embodiment,
the heat cycle includes heat of about 300.degree. F. for about 8
minutes. However, the curing temperature of the heat cycle will
vary depending upon the type of perfluoropolymer and curing agent
used in the perfluoroelastomer formulation and employ temperatures
are detailed above in the coatings context. One of ordinary skill
in the art will understand that curing conditions vary with
elastomer systems and that such temperature ranges are not intended
to be limiting with respect to the scope of the invention, since a
variety of perfluoroelastomer formulations can be used.
[0067] This heat cycle contributes to substantially if not fully
completing the cure reaction of the perfluoropolymer and curing
agent(s) within the bonding agent that subsequently results in the
same or substantially the same perfluoroelastomer as the
perfluoroelastomer of the rod stock. After the heat cycle, the
spliced ends can be post cured at about 180.degree. C. (356.degree.
F.) or other suitable post-cure temperature for about seven to
eight hours or other suitable cure cycle times. An additional cool
down time of one hour can then optionally be applied. Preferably
the bonding agent forming the perfluoroelastomer splice is cured to
about 95% as noted above. In addition to heat cure cycles, it is
also within the scope of the invention to use infrared, UV, or
other radiative curing techniques.
[0068] This welding process can be applied to a variety of rods
having multiple ends to form a variety of sealing rings of varying
sizes, shapes, and configurations. The resulting seals, which can
be very large in size, have a cured, indistinguishable, and
homogenous weld(s) compared to seals wholly formed from a
single-step mold operation. That is, the perfluoroelastomer weld
has the same or substantially the same chemical composition as the
perfluoroelastomer rod stock. This advantageously results in the
seal having the same highly resistant chemical composition
throughout. Thus, there are no weak points or welded ends that are
more vulnerable to chemical and/or physical attack than the rod
stock bulk seal material.
[0069] Although the present embodiment has been described for
bonding two surfaces of the same rod stock or two different pieces
of rod stock made from the same perfluoroelastomer, the present
invention is not limited to bonding such materials only. The
present invention can also be used to weld two different pieces of
rod stock made from different perfluoroelastomers, such as any of
the perfluoroelastomers described above. Further, the invention can
be used to bond or weld various other types of perfluoroelastomers
surfaces not in rod form--in sheet form, molded form, lamination
form and various other shapes.
[0070] In another embodiment, the present invention provides for a
method of potting a perfluoroelastomer seal 40 as illustrated in
FIGS. 5 and 7 using a bonding agent as described in any of the
above embodiments. As used herein and shown in FIG. 5a, the term
"potting" means filling in of gaps 42 or spaces between a seal 40
and a seal gland 44. The seal gland 44 is typically formed from
materials that are highly resistant to chemical attack such as
aluminum and stainless steel. In this embodiment, the bonding agent
is placed within the gaps 42 between the seal 40 and the seal gland
44. After potting the bonding agent, the entire construct i.e., the
seal 40, seal gland 44, and potted bonding agent, is heated to
about 149.degree. C. (300.degree. F.) for about eight minutes. The
heat cures the bonding agent and as a result forms a
perfluoroelastomer bond between the seal 40 and the seal gland 44.
An advantage of the present embodiment is that the
perfluoroelastomer seal 40 then is securely bonded to the seal
gland 44 which advantageously lowers particulation or degradation
of the primary sealing material due to the additional
perfluoroelastomer from the weld and because there is then
minimized gapping between the seal 40 and the gland through which
particulation may migrate. In addition, the bond eliminates the
relative motion and hence abrasion, between the seal and gland,
further contributing to lower particulation.
[0071] The application of the present embodiment is not limited to
potting such as seal against a gland having any particular
composition, but instead can be used to pot a perfluoroelastomer
seal on a variety of gland surfaces, for example, formed of metals,
metal alloys, plastics, composites and the like. However, metallic
and metallic alloy surfaces are most typically encountered in such
applications of use. Such potting uses can be used in various
bonded gland applications, including, semiconductor doors, gates,
and other pre-bonded surface sealing applications, and are
particularly useful when such applications are subject to high
corrosion such as semiconductor manufacturing conditions.
EXAMPLE 1
[0072] In this example, a large perfluoroelastomer seal was made
using Chemraz.RTM. molded subsections which had been cured, but not
post-cured. One section was rectangular in configuration, wherein
the rectangle had rounded corners. Two other circular sections were
prepared. The rectangular section was sliced transversely across
the long-sided portions of the rectangle. After cutting, two
half-rectangular end pieces were formed. The circular sections were
then sliced so as to form a rod, and shortened to the appropriate
length to form two straight sections of desired length. The
resultant two rectangular end pieces were joined to the two
straight sections using a bonding agent and a splicing fixture to
form a resultant part having the shape shown in FIG. 8.
[0073] The bonding agent used was prepared by first compounding a
perfluoroelastomer formulation having the following constituents,
as noted in parts by weight:
TABLE-US-00001 Components Parts by Weight Curable Perfluoropolymer
100 Silica 9 Peroxide-Based Curing Agent 1.5 Peroxide-Based Cure
System 4 Co-Agent Barium Sulfate 32
[0074] After compounding, the compounded formulation was cut into
small pieces, approximately 0.25 inches in size in the largest
dimension using a die cutter. The pieces were then added to a jar
having Fluorinert.RTM. FC-77 solvent. The solvent was added so as
to make-up 94% by weight of the total solution. The jar was then
placed on a jar mill and continuously rolled for about forty-eight
hours to form the bonding agent.
[0075] The bonding agent was coated on one end of a first rod stock
member and placed within a sealing fixture such as that shown in
FIG. 4, to be welded to a second rod stock member. The second rod
stock member was also coated and placed so that its end was pressed
against the coated end of the first rod stock member. The sealing
fixture was then closed and heated to about 149.degree. C.
(300.degree. F.) for about eight minutes to cure the bonding agent.
This welding process was performed four times at each desired weld
to form the finished part and to create the welds to form a
large-formed seal. The overall rectangular dimensions of the
finished part as shown in FIG. 8 were approximately 2.1 meters
long.times.0.17 m wide with a transverse cross-sectional diameter
(being generally circular in transverse configuration) of about 0.6
cm (the shape formed at the weld was not perfectly round, but was
very close). The part was then post-cured at 180.degree. C.
(356.degree. F.) for 7.25 hours followed by a one hour cool down
period.
EXAMPLE 2
[0076] A perfluoroelastomer coating was made by forming a first
solution (Solution A). Solution A was formed by dissolving 100
parts by weight of a curable cyano-curable perfluoropolymer
prepared in accordance with WO 00/08076 (a perfluoroelastomer gum
having a primary and secondary cyano curesite) in 900 parts by
weight of Fluorinert.RTM. FC-43 fluid solvent from 3M. A second
solution (Solution B) was made by dissolving 5 parts by weight of
heptafluorobutyrlamidine as a curing agent in 995 parts by weight
of the same solvent used to form Solution A. Solutions A and B were
then combined in equal parts by weight to form a finished coating
solution. The finished coating solution was applied on a metallic
substrate surface and subjected to a heat curing cycle of
100.degree. C. (212.degree. F.) for about four hours. The resulting
cured perfluoroelastomer coating was clear. Similar coatings were
also prepared on glass, plastic and synthetic rubber.
* * * * *