Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2002-02-06
2004-03-02
Wu, David W. (Department: 1713)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C526S214000, C526S250000, C526S227000
Reexamination Certificate
active
06700023
ABSTRACT:
FIELD OF THE INVENTION
A new class of low temperature initiators has been found, C
n
F
2n+1
(CH
2
)
a
CF
2
(C═O)O—O(C═O)CF
2
(CH
2
)
b
C
m
F
2m+1
, wherein n and m are each independently 1 to 4, and a and b are each independently 1 or 2, enabling fluoroolefin polymerizations at relatively low temperatures.
TECHNICAL BACKGROUND
Diacyl peroxides of diverse structure have been patented as fluoroolefin polymerization initiators, for example,
[RO(CH
2
CF
2
CF
2
O)
n
CH
2
CF
2
(C═O)O—]
2
, U.S. Pat. No. 4,663,407, issued May 1987, to Daikin Industries,
[—O(C═O)CFR
f
(C
3
F
6
O)
h
(C
2
F4O)
m
(CF
2
O)
n
(C
g
F
2g
O)
a
CFR
f
(C═O)O—]
x
, U.S. Pat. No. 3,882,193 (issued May 6, 1975 to Minnesota Mining and Manufacturing Company); [X(CF
2
)
n
(C═O)O—]
2
, U.S. Pat. No. 3,528,954 (issued Sep. 15, 1970 to E.I. du Pont de Nemours and Company); XC
m
F
2m
(C═O)OO(C═O)C
n
F
2n
X, EP 0606 492 A1 (published Jul. 9, 1993, to Daikin Industries) and
Cl
2
FC(C═O)OO(C—O)CCl
2
F U.S. Pat. No. 5,569,728 (issued Oct. 29, 1996, to Ausimont, SpA.). The best diacyl peroxide for a particular application can often be determined by its half-life. By “half-life” we mean the elapsed time it takes for half of the initiator in a system to decompose thermally to radicals. An initiator needs to last long enough for homogeneous mixing to occur with monomer but not so long as to make polymerization uneconomically slow. Half-lives on the order of 15 minutes to several hours are desirable.
Polymerization temperature can affect fundamental aspects of final polymer structure such as molecular weight and branching. Thus, a preferred polymerization temperature is chosen first and an initiator with an appropriate half-life chosen second. As used herein “HFPO is hexafluoropropylene oxide. For example were a polymerization's temperature set to 30° C., dimer peroxide (DP) with a half-life of 0.98 hours would be a faster and better choice than heptafluorobutyryl peroxide (4P) with a half-life of 8.8 hours (Table 1). If, however, the same polymerization needed to be run at 0° C., the half-life of DP would increase to 64 to 92 hours (Table 1), threatening an uneconomically slow process.
The potential advantages of faster, lower temperature initiation include increased productivity, increased polymer linearity, decreased chain transfer, increased polymer molecular weight, decreased monomer oligomerization during product letdown, decreased acid fluoride end group formation in the polymer, and decreased reactor pressure in condensed media such as liquified hexafluoropropylene (HFP) or CO
2
. The fastest (i.e., lowest temperature), well documented prior art diacyl peroxide, 1H3P, has a 16 hour half-life at 10° C. (see Table 1, J. Org. Chem., 47, 2009 (1982) and Japanese Pat. 61152653 A2, Chem. Abstracts 106:120380). Trichloroacetyl peroxide, which has been reported to have a 10 hour half-life at −3.9° C. (see U.S. Pat. No. 5,688,838) is still faster than 1H3P (“HCF
2
CF
2
—”) but has two disadvantages. First, the —CCl
3
group tends to chain transfer and, second, the initiating Cl
3
C* radical remains attached to the polymer chain as a potentially unstable end group. At 10° C., the inventive bis(2,2,5,5,5-pentafluoropentanoyl) peroxide (hereinafter “4H5P”) and bis(2,2,5,5,6,6,7,7,8,8,8-undecafluorooctanoyl) peroxide (hereinafter “4H8P”) initiators disclosed herein are 13 times faster and 9 times faster, respectively, than 1H3P. Holding the rate of radical generation constant, this represents a 10° C. to 20° C. advantage in polymerization temperature for the inventive peroxides of the present invention. Unlike trichloroacetyl peroxide, 4H5P and 4H8P will not introduce undesirable chlorine into either the polymer or the reaction mixture. Thus 4H5P, 4H8P, and the related peroxides disclosed herein appear particularly attractive as low temperature fluoroolefin polymerization initiators.
Commonly owned U.S. Pat. No. 5,763,552 discloses partially fluorinated surfactants of the formula R
f
—(CH
2
)
m
—R′
f
—COOM useful in the polymerization of fluorinated monomers. These surfactants are synthetic precursors, several steps removed, for many of the diacyl peroxides disclosed herein.
SUMMARY OF THE INVENTION
Disclosed in this invention are diacyl peroxides having the structure I,
R
f
CXX′(CYY′)
e
CF
2
(C═O)OO(C═O)CF
2
CWW′(CZZ′)
e′
R
f
′ I
wherein e and e′ are independently 0 or 1; and
when e=0, at least one of X, X′ is H and any of the other X, X′ is H or F; when e′=0, at least one of W, W′ is H and any of the other W,
W′ is H or F;
when e=1, at least one of X, X′, Y, Y′ is H and any of the other X, X′, Y, Y′ is H or F;
when e′=1, at least one of W, W′, Z, Z′ is H and any of the other W, W′, Z, Z′ is H or F;
wherein R
f
=C
n
F
(2n+1)
, n=1 to 4; and
wherein R
f
=C
m
F
(2m+1)
, m=1 to 4.
Also disclosed is a method for preparing a new class of diacyl peroxides, comprising:
contacting at least one acid halide of the formula II
RCXX′(CYY′)
e
CF
2
(C═O)L II
wherein e=0 or 1, and when e=0, at least one of X, X′ is H and any of the other X, X′is H or F, and when e=1, at least one of X, X′, Y, Y′ is H and any of the other X, X′, Y, Y′ is H or F;
wherein L is Cl or F, and
wherein R is R
f
or R
f′
; and wherein R
f
=C
n
F
(2n+1)
, n=1 to 4 and R
f
=C
m
F
(2m+1)
, m=1 to 4;
with a peroxide, to generate a diacyl peroxide of the structure
R
f
CXX′(CYY′)
e
CF
2
(C═O)OO(C═O)CF
2
CWW′(CZZ′)
e′
R
f
′ I
wherein e and e′ are independently 0 or 1; and
when e=0, at least one of X, X′ is H and any of the other X,
X′ is H or F; when e′=0, at least one of W, W′ is H and any of the other W, W′ is H or F;
when e=1, at least one of X, X′, Y, Y′ is H and any of the other X, X′, Y, Y′ is H or F;
when e′=1, at least one of W, W′, Z, Z′ is H and any of the other W, W′, Z, Z′ is H or F;
wherein R
f
=C
n
F
(2n+1)
, n=1 to 4; and
wherein R
f′
=C
m
F
(2m+1)
, m=1 to 4.
A further disclosure of this invention is a method for using a diacyl peroxide of the structure I, comprising:
R
f
CXX′(CYY′)
e
CF
2
(C═O)OO(C═O)CF
2
CWW′(CZZ′)
e′
R
f′
I
wherein e and e′ are independently 0 or 1; and
when e=0, at least one of X, X′ is H and any of the other X, X′ is H or
F; when e′=0, at least one of W, W′ is H and any of the other W, W′ is H or F;
when e=1, at least one of X, X′, Y, Y′ is H and any of the other X, X′, Y,Y′ is H or F;
when e′=1, at least one of W, W′, Z, Z′ is H and any of the other W, W′, Z, Z′ is H or F;
wherein R
f
=C
n
F
(2n+1)
, n=1 to 4; and
wherein R
f′
=C
m
F
(2m+1)
, m=1 to 4
(i) contacting at least one diacyl peroxide having the structure I with a monomer;
(ii) optionally, in the presence of a reaction medium selected from the group consisting of fluorocarbon, chlorofluorocarbon, and hydrocarbon fluids; fluorocarbon, chlorofluorocarbon and hydrocarbon mixed with water, wherein hybrid polymerization conditions form; and liquid or supercritical carbon dioxide; and
(iii) polymerizing the monomer, under suitable polymerization temperature and pressure whereby fluoroolefin polymerization occurs.
Another disclosure of this invention is a process for fluoroolefin polymerization, comprising the steps of:
(i) contacting at least one diacyl peroxide having the structure I
R
f
CXX′(CYY′)
e
CF
2
(C&b
Hung Ming-Hong
Wheland Robert Clayton
E. I. du Pont de Nemours and Company
Hu Henry
Wu David W.
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