Organic compounds -- part of the class 532-570 series – Organic compounds – Azides
Reexamination Certificate
2001-12-13
2002-07-09
Henderson, Christopher (Department: 1713)
Organic compounds -- part of the class 532-570 series
Organic compounds
Azides
Reexamination Certificate
active
06417379
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to both fluoroalkanesulfonyl azide compounds which are useful as functional monomers in fluoropolymers and to the fluoropolymers which contain units derived from such fluoroalkanesulfonyl azide monomers.
BACKGROUND OF THE INVENTION
Fluoroelastomers must generally be cured in order to develop the physical properties necessary for most end use applications. Often, the fluoroelastomer must contain a curesite monomer such as CF
2
═CFOCF
2
CF(CF
3
)OCF
2
CF
2
—CN (U.S. Pat. No. 4,281,091) in order to be cured. Such curesite monomers require long exposure to high temperature and the presence of catalyst(s) to complete the curing. However, catalyst residues may adversely affect the properties of the cured fluoroelastomer article, or byproducts of the curing reaction may pose environmental problems. Long exposure to high temperatures may increase manufacturing costs and can cause polymer degradation
Thus, there is a need for curesite monomers which do not require catalysts or long exposure to high temperatures in order to crosslink fluoroelastomers.
There is also a need for fluoropolymers having functional side groups for improving the adhesion of fluoropolymers to other substrates (such as metal surfaces or other polymers), for improved durability of fluoropolymer coatings, and for providing crosslinking to improve the mechanical properties of the fluoropolymers.
SUMMARY OF THE INVENTION
The present invention provides a new class of functional monomers having a sulfonyl azide group. Copolymerizing these monomers with at least one other (i.e. different) fluorinated monomer, and (optionally) a fluorine-free monomer, provides a fluoropolymer having a reactive fluoroalkanesulfonyl azide side group which can form crosslinks in fluoropolymers without the need for catalysts or exposure to high temperatures for long periods of time. The sulfonyl azide side group may also be used to enhance adhesion between the fluoropolymer and another substrate, improve the durability of coatings, and increase the mechanical properties of the fluoropolymer through crosslinking.
Specifically, an embodiment of this invention is a fluoroalkanesulfonyl azide compound of the formula
CF
2
═CF—(O)
p
—R
f
—(CH
2
)
n
—S(O)
q
N
3
(I)
wherein p=0 or 1; n=0-4; q=1 or 2; and R
f
is a C
1
-C
16
perfluoroalkyl or perfluoroalkoxy group. Preferably, p=1; n=0; q=2 and R
f
is selected from the group consisting of —CF
2
CF(CF
3
)OCF
2
CF
2
— and —(CF
2
)
m
—, wherein m=2-4.
A second embodiment of this invention is a fluoroalkanesulfonyl azide compound of the formula
CX
1
X
2
═CX—(O)
p
—R
f
—(CH
2
)
n
—S(O)
q
N
3
(II)
wherein X, X
1
, X
2
are independently H or F (with the proviso that X, X
1
, and X
2
can not all be F, so that compound II is not identical to compound I); p=0 or 1; n=0-4; q=1 or 2; and R
f
is a perfluoroalkyl or perfluoroalkoxy group. Preferably, X, X
1
, X
2
are H; p=0; n=0; q=2; and R
f
is —CF
2
CF
2
OCF
2
CF
2
— or —(CF
2
)
y
—, wherein y=1-8.
A third embodiment of this invention is a copolymer comprising units derived from compound (I) or compound (II) and units derived from at least one other fluorinated monomer.
DETAILED DESCRIPTION OF THE INVENTION
It has been discovered that certain fluoroalkylsulfonyl azide compounds are useful as monomers in making fluoropolymers, and are particularly useful in minor amount to introduce highly reactive functional side groups into the fluoropolymer. Such fluoropolymers are useful materials in the areas of curable elastomers and elastoplastics, adhesion enhancement, coatings, thermosetting resins, grafting polymers and the like. Under the appropriate thermal or photo initiation conditions, the sulfonyl azide functional group is able to generate a highly reactive nitrene species. The nitrene intermediate may then undergo either a coupling or an insertion reaction, thereby crosslinking the fluoropolymer chains.
A first embodiment of this invention is a fluoroalkanesulfonyl azide compound of the formula
CF
2
═CF—(O)
p
—R
f
—(CH
2
)
n
—S(O)
q
N
3
(I)
wherein p=0 or 1; n=0-4; q=1 or 2; and R
f
is a C
1
-C
16
perfluoroalkyl or perfluoroalkoxy group. Preferably, p=1; n=0; q=2 and R
f
is selected from the group consisting of —CF
2
CF(CF
3
)OCF
2
CF
2
— and —(CF
2
)
m
—, wherein m=2-4. Specifically, these species include, but are not limited to, CF
2
═CFOCF
2
CF(CF
3
)OCF
2
CF
2
—SO
2
N
3
(8-SAVE); CF
2
═CFOCF
2
CF
2
—SO
2
N
3
; CF
2
═CFOCF
2
CF
2
CF
2
—SO
2
N
3
; and CF
2
═CFOCF
2
CF
2
CF
2
CF
2
—SO
2
N
3
.
A second embodiment of this invention is a fluoroalkanesulfonyl azide compound of the formula
CX
1
X
2
═CX—(O)
p
—R
f
—(CH
2
)
n
—S(O)
q
N
3
(II)
wherein X, X
1
, X
2
are independently H or F (with the proviso that X, X
1
and X
2
can not all be F); p=0 or 1; n=0-4; q=1 or 2; and R
f
is a perfluoroalkyl or perfluoroalkoxy group. Preferably, X, X
1
, X
2
are H; p=0; n=0; q=2; and R
f
is —CF
2
CF
2
OCF
2
CF
2
— or —(CF
2
)
y
—, wherein y=1-8. A specific example is CH
2
═CHCF
2
CF
2
OCF
2
CF
2
—SO
2
N
3
.
When q=1 in formula I or II, the monomers of this invention are more correctly described as “fluoroalkanesulfinyl azides”. However, for simplicity, the monomers of this invention are collectively referred to herein as fluoroalkanesulfonyl azides, regardless of whether q=1 or 2.
The general process for making the fluoroalkanesulfonyl azide compounds of this invention is to react sodium azide with the appropriate fluoroalkanesulfonyl fluoride, fluoroalkanesulfonyl bromide, or fluoroalkanesulfonyl chloride at a temperature between −20° to 50° C. (preferably between 0° to 20° C.) in a solvent such as methanol, acetonitrile, acetone, or mixtures thereof.
Copolymers of this invention comprise i) units derived from either compound (I) or compound (II) of this invention and ii) units derived from at least one other fluorinated monomer. By “other fluorinated monomer” is meant a copolymerizable fluoromonomer other than a fluoroalkanesulfonyl azide. In addition, copolymers may contain units derived from one or more fluorine-free monomers.
Preferably, units derived from compound (I) or compound (II) are present in minor amounts in the copolymers of this invention. Typically, copolymers contain 0.02-10 mole percent (based on the total monomer units in the polymer) of units derived from either compound (I) or compound (II), preferably 0.1-5 mole percent and most preferably 0.3-3 mole percent.
Fluorinated monomers suitable for forming copolymers with compound (I) or compound (II) include, but are not limited to: tetrafluoroethylene (TFE); chlorotrifluoroethylene (CTFE); trifluoroethylene; vinylidene fluoride (VF2); vinyl fluoride (VF); hexfluoropropylene (HFP); 1- or 2-hydropentafluoropropylene, 3,3,3-trifluoropropylene; hexafluoroisobutylene; perfluoro(alkyl vinyl ethers) (PAVE) having alkyl groups containing 1-5 carbon atoms (preferably 1-3 carbon atoms); perfluoro(alkoxy vinyl ethers) having alkoxy groups containing 1-5 carbon atoms; perfluoro-(2,2-dimethyl-1,3-dioxole) (PDD) and perfluoro-(2-methylene-4-methyl-1,3-dioxolane) (PMD). Also included in this group of fluorinated monomers are perfluoro(alkyl vinyl ethers) which contain functional groups such as acid fluorides or esters. Examples of these ethers include CF
2
═CFOCF
2
CF(CF
3
)OCF
2
CF
2
SO
2
F (PSEPVE) and CF
2
═CFOCF
2
CF(CF
3
)OCF
2
CF
2
COOCH
3
(EVE). Preferably, at least one of the fluorinated monomers is selected from the group consisting of TFE, CTFE and VF2.
Fluorine free monomers that can be used in the copolymers of this invention include: ethylene, propylene, n-butylene, iso-butylene, vinyl acetate (VAc), and vinyl ethers such as methyl vinyl ether.
The copolymers of this invention may be glassy, thermoplastic or elastomeric. They may b
DuPont Dow Elastomers L.L.C.
Henderson Christopher
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