Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-10-09
2002-08-20
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, C526S255000, C526S348800
Reexamination Certificate
active
06437066
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a novel class of fluorovinyl ether monomers which are useful as cure site monomers in fluoroelastomers, a process for the preparation of these fluorovinyl ether monomers and to curable fluoroelastomer copolymers having copolymerized units of these fluorovinyl ether monomers.
BACKGROUND OF THE INVENTION
Elastomeric fluoropolymers (i.e. fluoroelastomers) exhibit excellent resistance to the effects of heat, weather, oil, solvents and chemicals. Such materials are commercially available and are most commonly either dipolymers of vinylidene fluoride (VF
2
) with hexafluoropropylene (HFP) or terpolymers of VF
2
, HFP, and tetrafluoroethylene (TFE). While these di- and terpolymers have many desirable properties, including low compression set and excellent processability, their low temperature flexibility is not adequate for all applications, nor is their resistance to attack by alkaline solvents.
It is known that incorporation of perfluorinated ether monomer units into vinylidene fluoride elastomers improves low temperature properties, i.e. cured articles made from these polymers seal well at low temperatures. For example, Carlson, in U.S. Pat. No. 5,214,106 discloses that when perfluoro(methyl vinyl) ether (PMVE) is substituted for HFP, the resultant VF
2
/PMVE/TFE copolymers have glass transition temperature (T
g
) values which are 10°−20° C. lower than those of the corresponding VF
2
/HFP/TFE copolymers. T
g
is often used as an indicator of low temperature: flexibility because polymers having low glass transition temperatures maintain elastomeric properties at low temperatures.
Other common fluoroelastomers include the copolymers of TFE with one or more hydrocarbon olefins such as ethylene or propylene, and, optionally VF2 (for example U.S. Pat. No. 4,758,618). These copolymers are generally more resistant to attack by alkaline solutions than other types of fluoroelastomers. The copolymers may also contain a perfluoro(alkyl vinyl) ether (PAVE) in order to impart good low temperature sealing properties (U.S. Pat. No. 4,694,045).
Many of the fluoroelastomers listed above require incorporation of a cure site monomer into their polymer chains in order to crosslink efficiently. Without such a cure site monomer, the fluoroelastomer may not react at all with curing agents, it may only partially react, or reaction may be too slow for use on a commercial scale. Seals made from poorly crosslinked elastomers often fail sooner than might otherwise be expected. Unfortunately, disadvantages are associated with many of the cure site monomers in use today. For example, monomers which contain reactive bromine or iodine atoms can release byproducts during the curing reaction that are harmful to the environment. Other cure site monomers (e.g. those which contain double bonds at both ends of the molecule) may be so reactive that they disrupt polymerization of the fluoroelastomer by altering the polymerization rate, terminating polymerization, or by causing undesirable chain branching, or even gelation to occur. Lastly, incorporation of a cure site monomer into a fluoroelastomer polymer chain may negatively impact the properties of the fluoroelastomer (both physical properties and chemical resistance).
There thus exists a need in the art for cure site monomers which are environmentally friendly, do not disrupt polymerization and which do not detract from the properties of the fluoroelastomer.
SUMMARY OF THE INVENTION
The present invention is directed to a fluorovinyl ether monomer of the formula CF
3
CHFCF
2
—(O)
n
—(CH
2
)
m
—(CF
2
)
p
—R
f
—OCF═CF
2
, wherein R
f
is a C
1
-C
8
perfluoroalkyl group or a C
1
-C
8
petfluoroalkoxy group, n is 0 or 1, in is an integer from 1 to 3, and p is an integer from 1 to 4.
The present invention is also directed to a process for the preparation of the above fluorovinyl ether. The process comprises the steps of
A. chlorinating an hydroxy vinyl ether compound of the formula HO—(CH
2
)
m
—(CF
2
)
p
—R
f
—OCF═CF
2
to produce a chlorinated hydroxy ether of the formula HO—(CH
2
)
m
—(CF
2
)
p
—R
f
—OCFCl—CF
2
Cl;
B. condensing said chlorinated hydroxy ether with hexafluoropropene to produce a chlorinated ether of the formula CF
3
CHFCF
2
—(O)
n
—(CH
2
)
m
—(CF
2
)
p
—R
f
—OCFCl—CF
2
Cl; and
C. dechlorinating said chlorinated ether to produce a fluorinated vinyl ether of the formula CF
3
CHFCF
2
—(O)
n
—(CH
2
)
m
—(CF
2
)
p
—R
f
—OCF═CF
2
.
The present invention is also directed to a fluoroelastomer composition comprising
A. copolymerized units of a first monomer, said first monomer being a fluoroolefin selected from the group consisting of vinylidene fluoride and tetrafluoroethylene;
B. copolymerized units of a second monomer, different from said first monomer, said second monomer selected from the group consisting of i) fluoroolefins, ii) hydrocarbon olefins, iii) perfluoro(alkyl vinyl)ethers and iv) perfluoro(alkoxy vinyl) ethers; and
C. copolymerized units of a fluorinated vinyl ether cure site monomer of the formula CF
3
CHFCF
2
—(O)
n
—(CH
2
)
m
—(CF
2
)
p
—R
f
—OCF═CF
2
, wherein R
f
is a C
1
-C
8
perfluoroalkyl group or a C
1
-C
8
perfluoroalkoxy group, n is 0 or 1, m is an integer from 1 to 3, and p is an integer from 1 to 4.
The present invention is also directed to a polyhydroxylic curable composition of the above fluoroelastomer.
DETAILED DESCRIPTION OF THE INVENTION
The fluoroelastomers utilized in the curable compositions of the present invention are copolymers capable of undergoing crosslinking reactions with polyhydroxylic compounds to form cured elastomeric compositions that exhibit excellent physical properties and chemical resistance. Furthermore, the cure site monomers employed in the fluoroelastomers of this invention do not adversely affect the polymerization process, nor do byproducts of the curing reaction pose an environmental concern.
The fluoroelastomers of this invention comprise copolymerized units of A) a first monomer which is a fluoroolefin selected from the group consisting of vinylidine fluoride and tetrafluoroethylene; B) a second monomer, which is not the same as the first monomer, and which is selected from the group consisting of fluoroolefins, hydrocarbon olefins, perfluoro(alkyl vinyl)ethers and perfluoro(alkoxy vinyl) ethers; and C) a fluorovinyl ether cure site monomer of the formula CF
3
CHFCF
2
—(O)
n
—(CH
2
)
m
—(CF
2
)
p
—R
f
—OCF═CF
2
, wherein R
f
is a C
1
-C
8
perfluoroalkyl group or a C
1
-C
8
perfluoroalkoxy group, n is 0 or 1, m is an integer from 1 to 3, and p is an integer from 1 to 4.
Optionally, the fluoroelastomers of this invention may further comprise copolymerized units of at least one additional monomer, different from said first, second and cure site monomers. The additional monomer or monomers may be selected from the group consisting of perfluoro(alkyl vinyl) ethers, perfluoro(alkoxy vinyl) ethers, fluoroolefins and hydrocarbon olefins.
In addition, the fluoroelastomer copolymers of this invention may optionally contain up to about 1 wt. % iodine bound to polymer chain ends, the iodine being introduced via use of an iodine-containing chain transfer agent during polymerization.
Examples of fluoroolefin monomers useful as the second monomer and as the optional additional monomer in the fluoroelastomers of this invention include, but are not limited to vinylidenefluoride (VF
2
), tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), pentafluoropropylene, vinyl fluoride and the like.
Hydrocarbon olefin monomers which may be employed as the second monomer and as the optional additional monomer in fluoroelastomers of this invention contain no fluorine atoms. Examples of such hydrocarbon olefins include, but are not limited to ethylene (E), propylene (P), butylene -1 and isobutylene.
Perfluoro(alkyl vinyl) ethers suitable for use as comonomers include those of the formula
CF
2
═CFO(R
f′
O)
n
(R
f″
O)
m
R
f
(I)
where R
f′
and R
f″
are different linear o
Hung Ming-Hong
Schmiegel Walter W
DuPont Dow Elastomers L.L.C.
Zitomer Fred
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