Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-06-27
2002-12-03
Zitomer, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S247000, C526S250000, C526S253000, C526S254000
Reexamination Certificate
active
06489420
ABSTRACT:
FIELD OF THE INVENTION
The invention pertains to fluoropolymers derived from (i) tetrafluoroethylene (TFE), (ii) vinylidene fluoride (VF2), (iii) at least one ethylenically unsaturated monomer of the formula CF
2
═CFR
f
, and (iv) a perfluorovinyl ether of the formula CF
2
═CFOCF
2
CF(R
f
)
a
OR′
f
where a, R
f
and R′
f
are defined below.
BACKGROUND
Polymers of tetrafluoroethylene (TFE) with other fluorinated monomers such as vinylidene fluoride (VDF) and hexafluoropropylene (HFP) are known. These polymers include both fluoroelastomers and melt processable fluoroplastics.
Fluoroelastomers with a high fluorine content have been shown to have excellent permeation resistance to fuels. (U.S. Pat. No. 4,696,989). However, high-fluorine elastomer systems based on tetrafluoroethylene (TFE), vinylidene fluoride (VDF) and hexafluoropropylene (HFP) have some limitations. When the TFE-content is too high, flexibility, and the ease of processing tends to be compromised. If the HFP content, at the expense of VDF is too high, the polymerization rate is much too low.
Another class of polymers with superior permeation properties are the melt-processable fluoroplastics THV (see Modern Fluoropolymers, Wiley, 1997). The terpolymers can have melting points up to 275° C. and show excellent permeation and low temperature properties. However, sealability and flexural properties sometimes do not meet industry requirements. The increased stiffness of those materials can lead to wrinkling when hoses are loaded onto forming mandrels. It can also lead to increased push-on force during hose installation and sealing concerns at connecting points. These fluoroplastic materials and their wide range of uses is described in more detail in “Modern Fluoropolymers”, Wiley, 1997, p. 257. They typically are derived from monomer compositions comprising from 30-75 weight % TFE, 5-40 weight % HFP and 5-55 weight % VDF and have a melting point range of 100° C. to 275° C.
Because of their permeation resistance, fluoropolymers are desired in a variety of products, including hose and fuel-line designs for automotive applications such as those disclosed in U.S. Pat. No. 5,804,670 and EP 824059. Other product applications where such polymers are useful include fuel filler neck hoses, fuel vent lines, vapor return lines, chemical handling hoses and the like.
These product applications are often multilayer constructions in which the fluoropolymer layer serves as a chemically resistant or vapor impermeable barrier. The remainder of these multilayer constructions typically comprises a layer of either a less expensive non-fluorinated polymer layer or another fluoropolymer. These other polymers can be thermoplastic or they can be elastomeric in nature. The constructions can also employ a tie layer between the various layers. In any event, the layers are generally covalently bonded to each other.
These constructions generally must be highly flexible to facilitate installation, provide good sealing around connectors and to withstand the formation of bubbles and/or ripples in pieces with sharp bends. Additionally, when they are used with a non-fluorinated elastomer, the fluoropolymer must be resistant to high temperatures to minimize the temperatures encountered during the manufacture and use of constructions that employ them.
While the use of fluoropolymers in applications such as those disclosed above has increased in recent years, a need still exists to provide improved fluoropolymers. The present invention provides such improved fluoropolymers.
SUMMARY OF THE INVENTION
The present invention provides fluoropolymers that comprise TFE, VF2, at least one perfluorinated ethylenically unsaturated monomer, and a perfluorovinyl ether. The polymers of the invention demonstrate excellent physical properties over a broad range of compositions. They also demonstrate superior flexibility.
In accordance with the present invention there is provided a fluoropolymer derived from interpolymerized units of (i) TFE, (ii) VF2, (iii) at least one ethylenically unsaturated monomer of the formula CF
2
═CFR
f
where R
f
is perfluoroalkyl of 1 to 8, preferably 1 to 3, carbon atoms, and (iv) a perfluorovinyl ether of the formula CF
2
═CF—(OCF
2
CF(R
f
))
a
OR′
f
where R
f
is a perfluoroalkyl of 1 to 8, preferably 1 to 3, carbon atoms, R′
f
is a perfluoroaliphatic, preferably perfluoroalkyl or perfluoroalkoxy, of 1 to 8, preferably 1-3, carbon atoms, and a has a value of from 0 to 3.
Also provided herein are multilayer articles comprising a first layer or strata of the polymer of the invention and a second layer or strata of the same or another polymer. The layers are preferably covalently bonded to one another either through a tie layer between them or by means of direct covalent bonding between the two layers. Other polymeric layers may also be employed in this embodiment of the invention.
Also provided in accordance with the present invention is an electrostatically dissipative (ESD) composition comprising an electrically conductive particulate material and the polymer of the invention.
Also provided herein is a method for improving the flexibility of a fluoropolymer containing interpolymerized units derived from TFE, VF2 and at least one ethylenically unsaturated monomer of the formula CF
2
═CFR
f
where R
f
is as described above. The method comprises the steps of providing these monomers and a monomer of the formula CF
2
═CFOCF
2
CF(R
f
)
a
OR′
f
and polymerizing the monomers.
The polymer of the invention offers advantages, in the production of multi-layer articles by means of extrusion or coextrusion; in injection molding; and in compression molding. Fluoroplastics of the invention offer benefits in optical applications such as polymer optical fibers; and in use as an electrostatically dissipative (ESD) fluoroplastic. These advantages are especially useful in the case of complicated shapes.
Specific examples of such multilayer and/or shaped articles include fuel management components e.g., fuel filler neck hoses, vent lines, vapor return lines, etc., where resistance to hydrocarbon fluids is important; chemical handling components (e.g., hoses containers, etc.) and polymer optical fibers. In this latter case the polymers of the invention can be used as the optical fiber itself or as a cladding around the optical fiber (typically an acrylate polymer).
DETAILED DESCRIPTION
The polymer of the invention is sometimes referred to herein as a quad polymer. In one preferred embodiment it is derived from 30 to 85 weight % TFE, 5 to 55 weight % VDF, and from 5 to 50 weight % of the unsaturated monomer having the formula CF
2
═CFR
f
and from 0.1 to 15 weight % of the vinyl ether. Included in this range of compositions are semi-crystalline and elastomeric fluoropolymers.
The molecular weight of the polymer of the invention is not critical and may vary over a wide range. Thus it may vary from low molecular weight to ultra high molecular weight. Furthermore, the fluoropolymers may have either a generally unimodal or a multimodal molecular weight distribution.
The molecular weight of a semicrystalline fluoropolymer according to the invention may be described by its melt flow index (MFI). MFI can be determined by following the procedures described in either ISO 12086 or ASTM D-1238 at a support weight of 5 kg and a temperature of 265° C.
The molecular weight of an elastomeric fluoropolymer according to the invention may be described by its Mooney viscosity (ML). This value can be measured according to ASTM D 1646 using a one minute pre-heat and a 10 minute test at 121° C.
The semi-crystalline fluoropolymers of the invention typically have a peak melting temperature in the range of 100° to 275° C. (preferably 120 to 250° C.) and a number average molecular weight of from25,000 to 1,000,000. Preferably they have a hydrogen content of less than 5% by weight and a fluorine content of from 65 to 76%. Most preferably the polymers of the invention consist essentially of interpolymerized units derive
Chen Lisa P.
Duchesne Denis
Hintzer Klaus
Kaspar Harald
Löhr Gernot
Dyneon LLC
Harts Dean M.
Lilly James V.
Zitomer Fred
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