Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-04-29
2004-09-21
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S326400, C525S351000, C525S355000, C525S359200, C525S374000, C525S375000, C525S379000
Reexamination Certificate
active
06794457
ABSTRACT:
TECHNICAL FIELD
This invention relates to curing fluoropolymer compositions having nitrogen-containing cure-site components.
BACKGROUND
Fluorine-containing polymers (also known as “fluoropolymers”) are a commercially useful class of materials. Fluoropolymers include, for example, crosslinked fluoroelastomers, uncrosslinked fluoroelastomer gums, semi-crystalline fluoroplastics, and or glassy fluoroplastics. Fluoroplastics are generally of high thermal stability and are particularly useful at high temperatures. They may also exhibit extreme toughness and flexibility at very low temperatures. Some have very low dielectric loss and high dielectric strength, and may have unique low friction properties.
Fluoroelastomers exhibit significant tolerance to high temperatures and harsh chemical environments. Consequently, they are particularly well-adapted for use as seals, gaskets, and other molded parts in systems that are exposed to elevated temperatures and/or corrosive chemicals. Such parts are widely used in the chemical processing, semiconductor, aerospace, and petroleum industries, among others.
Fluoroelastomers often include a cure-site component to facilitate cure in the presence of a catalyst. One class of useful cure-site components includes nitrogen-containing monomers. Organotin catalysts are typically used as cure catalysts. Such catalysts, however, are toxic and can leave undesirable extractable metal residues in the cured product.
SUMMARY
In one aspect, the invention relates to a composition that includes (a) a fluoropolymer having interpolymerized units derived from a nitrogen-containing cure site monomer, and (b) a catalyst composition that includes a compound having the general formula:
wherein the group HA is an inorganic or organic acid, e.g., HCl, HNO
3
, C
7
F
15
COOH, and wherein R
1
, R
2
, and R
3
are each, independently, the same or different alkyl groups having from 1 to about 20 carbon atoms, which may be cyclic or heterocyclic, and one R group may instead be a bond to another R group such that the nitrogen is bonded to or part of an alkenyl, cycloalkenyl, or aromatic group. The substituents may also be olefinic, e.g., mono, di, and trialkyl amine salts, and pyridine salts. R
1
, R
2
, and R
3
may be fluorinated groups such as R
f
(CH
2
)
x
— wherein R
f
is a C
1
-C
8
linear or branched and at least partially fluorinated (i.e., fluorinated or perfluorinated) alkylene, cycloalkylene, or oxyalkylene, and x is 1 to 4 (more preferably 1 or 2). Examples of catalyst compositions include compounds of the formula:
wherein m and n are, independently, 2 to 20.
When a compound has more than one nitrogen atom, the mono, di, and higher salts are also useful.
The composition may further include a second catalyst composition comprising a compound having the formula R
1
C(OR
2
)═NH, and salts thereof, where R
1
and R
2
are, independently, a substituted or unsubstituted C
1
-C
20
(preferably C
1
-C
10
, more preferably C
1
-C
7
) alkyl, aryl, aralkyl, alkenyl, cycloalkyl, or cycloalkenyl group.
In other aspects, the invention provides a method for curing this composition, as well as curable and cured articles comprising these compositions.
The compositions retain the advantages of the use of nitrogen-containing cure site monomers such as the high temperature performance properties and chemical resistance typically achieved when organotin compounds are used as the catalyst system with such cure site monomers. At the same time, the compositions exhibit markedly improved compression set values. The compositions are useful in applications where polymer stability (e.g., thermal stability) and/or chemical resistance are important. They are also useful in silicon wafer fabrication.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and from the claims.
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Grootaert Werner M. A.
Hintzer Klaus
Kolb Robert E.
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