Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-12-29
2002-06-25
Mulcahy, Peter D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S413000, C524S423000, C524S425000, C524S448000, C524S449000, C524S450000, C524S496000, C524S544000, C524S545000, C524S546000
Reexamination Certificate
active
06410630
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to fluoroelastomer compositions and, more particularly, to a high solids content, solvated, fluoroelastomer composition which is workable and is useful for both horizontal and vertical applications.
BACKGROUND OF THE INVENTION
High solids content, solvated, fluoroelastomer compositions are typically used to fill voids, coat, adhere, seal, and protect various substrates from chemical permeation, corrosion, abrasion, etc. Similar low solids content compositions are used as coatings to protect the surface of different substrates. The properties of the sealants, caulks, adhesives, and coatings are commonly adjusted for structural stability and to impart resistance to chemicals, pressure, abrasion, and temperature.
Such compositions often comprise fluoroelastomers which commonly consist of polymers of hexafluoropropylene (HFP), vinylidene fluoride (VF
2
), and tetrafluoroethylene (TFE). These fluoroelastomer polymers can be cured by a variety of curing agents, for example, amines, bisphenols, and peroxides. Metallic oxides are commonly used to react with HF generated during the curing reaction. In addition, ketones, such as methyl ethyl ketone, and acetates are common solvents used with these fluoroelastomers. One well-known commercial product line comprised of such fluoroelastomers is that referred to as VITON® fluoroelastomers (a product of DuPont Dow Elastomers L.L.C.). VITON® fluoroelastomers are comprised of HFP, VF
2
, and TFE. Another well-known commercial fluoroelastomer, named Fluorel™/Dyneon™ (a product of Dyneon of Oakdale, Minn.), incorporates similar compounds, such as HFP, VF
2
, and TFE. Such fluoroelastomer compositions have been used often in molded seal products (sealants), less commonly in coatings, and even less commonly in caulks.
Low molecular weight copolymers of VF
2
and HFP display high heat and chemical resistance and can be used as components of seals, wire coatings, and diaphragms in equipment which are exposed to high temperatures and corrosive liquids and gases.
Known high solids content, solvated, fluoroelastomer compositions generally have a solids content of less than 75%. With higher levels of solids, these compositions are not easily manipulable and are unworkable. Such compositions are also prone to cracking, blistering, and bubbling caused by air trapped in the compositions. Lower solids content compositions also typically encounter shrinkage problems when they dry, thus requiring multiple passes. Because of the additional time and expense necessary in using lower solids content compositions, they are less useful.
SUMMARY OF THE INVENTION
The present invention comprises a high solids (at least 75% by weight) content fluoroelastomer composition containing HFP, VF
2
,and/or TFE fluoroelastomers of which at least 40% by weight is vinylidene fluoride. The composition further comprises a solvent, typically an acetate or ketone, and a low solvent absorptive filler (LSA filler). Optionally, the composition may comprise additional additives to effect various properties of the composition, including other fillers. The LSA filler is one which has a combination of properties, such as surface area, particle size, and oil absorption, that, when incorporated into the composition of the present invention, yields a workable, solvated, fluoroelastomer composition.
The composition of the present invention can be used for both horizontal and vertical applications depending on the type and amount of filler and other additives used. Further, in certain embodiments of the invention, the composition includes a low-temperature curing agent containing polyfunctional amines, amino silanes, and ketimines.
Generally, the average Mooney Viscosity of the fluoroelastomer used in the present invention, when measured at 250° F., is less than about 60. Mooney Viscosity is calculated as ML 1+10@250° F. where “ML” represents the minimum torque value for a Mooney Viscometer and the numerical values following “ML” represent the amount of time it takes for the sample to heat up (1 minute) and the amount of time the machine runs at temperature (10 minutes), respectively.
The composition may also comprise a thixotropic agent which regulates the shear thinning index of the composition.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention comprises a high solids content, solvated, fluoroelastomer composition which is workable and usable in both vertical and horizontal sealing applications to fill voids, coat, adhere, seal, and protect various substrates from chemical permeation, corrosion, abrasion, etc. After placement, the composition hardens to form a seal at the filling site. The hardening may be caused by solvent evaporation, chemical cross-linking of the polymer, or a combination of the two effects. The term “workable” means that it is possible to stir, pour, and apply the product to a wide variety of surfaces without difficulty. For vertical applications, it is important, however, that the flowability of the composition be sufficiently low to prevent spontaneous flow after placement.
The fluoroelastomer component contains hexafluoropropylene (HFP), vinylidene fluoride (VF
2
), tetrafluoroethylene (TFE), and/or any other fluoroelastomer having suitable properties for incorporation into a high solids composition. Specifically, copolymers of HFP and VF
2
or terpolymers of HFP, VF
2
, and TFE generally form the fluoroelastomer component of the composition, of which preferably at least 40% (more preferably 60%) by weight is vinylidene fluoride. The average Mooney Viscosity (ML 1+10@250° F.) of these compounds should be less than about 60, preferably less than about 40, more preferably less than about 10.
Generally, such fluoroelastomers, as are useful in the present invention, will have an average molecular weight at or below 100,000 Daltons.
Fluoroelastomer solutions with lower solution viscosities (usually attributable to a low molecular weight and low compound viscosity of the fluoroelastomers) are prepared so that the compositions of the present invention can be fluid at the desired higher solids content formulations. Table 1 shows the compound and solution viscosities of four fluoroelastomers commonly used in the composition of the present invention, namely Dyneon™ FC 2210X, VITON® A-100, Dyneon™ FC 2211, and VITON® A. Each of these fluoroelastomers is a copolymer of HFP and VF
2
. The compositions are tested for solution viscosity at a 65% solids content in methyl ethyl ketone (MEK) and no filler is included. Fillers would enable compositions of a higher solids content, such as in the present invention.
TABLE 1
Solution Viscosity
Fluoroelastomer
Mooney Viscosity
(centipoises (cps))
Polymer
(ML 1 + 10 @ 250° F.)
65% solid in MEK
Dyneon ™ FC 2210X
<1
160
VITON ® A-100
12
45,000
Dyneon ™ FC 2211
14
90,000
VITON ® A
40
>2,000,000
The solids content of the composition of the present invention is at least about 75% , by weight, preferably from about 80% to about 95% , more preferably from about 80% to about 90%. Solids contents above 95% may also be usable, so long as the molecular weight and the solution viscosity of the fluoroelastomer, the filler content, and other variables are adjusted to maintain the workability of the composition. The high solids content in the composition allows for a reduction in the amount of undesirable volatile organic compounds (VOC's) produced.
The composition further comprises a solvent component and a filler component. The solvent component may include ketones or acetates, or compounds having similar chemical moieties. The solvent component may include at least one high boiling point solvent, i.e., having a boiling point of at least about 100° C., preferably between about 100° C. and 200° C. High boiling point solvents reduce air trapped in the compositi
Hoover Gary Scott
Ross, Jr. Edwin William
Mulcahy Peter D.
Pelseal Technologies, LLC
Ratner & Prestia
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