Amorphous tetrafluoroethylene-hexafluoropropylene copolymers

Details Amorphous tetrafluoroethylene-hexafluoropropylene copolymers Amorphous tetrafluoroethylene-hexafluoropropylene copolymers

2000-07-14

2002-11-26

Lipman, Bernard (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S247000, C526S248000, C526S249000, C526S250000, C526S253000, C526S254000

Reexamination Certificate

active

06486280

ABSTRACT:

FIELD OF THE INVENTION
This invention concerns copolymers containing hexafluoropropylene and tetrafluoroethylene which are amorphous. They may be produced by a novel high pressure continuous process.
TECHNICAL BACKGROUND
Amorphous fluorinated polymers, particularly perfluorinated polymers, are highly useful, particularly as coatings and encapsulants, because of their unusual surface properties, low refractive index, low dielectric constant., and the relative ease of coating or encapsulating objects with such polymers. However, the use of such polymers has been limited because of their high cost, which usually derives from the high cost of the monomers and/or the high cost of the polymerization process to make the polymers. Therefore, such polymers, and the processes for making them, which are lower in cost are constantly being sought.
U.S. Pat. No. 3,062,793 describes amorphous copolymers of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) which are made by a high pressure free radical polymerization. The only process described therein is a batch process which has a relatively low productivity.
SUMMARY OF THE INVENTION
This invention concerns a continuous polymerization process, comprising, contacting at a pressure of about 41 MPa to about 690 MPa, and a temperature above about 200° C., preferably about 200° C. to about 400° C., tetrafluoroethylene, hexafluoropylene, and a radical initiator, to produce an amorphous polymer which contains at least 30 mole percent, of repeat units derived from said hexafluoro-propylene, at least 1 mole percent of repeat units derived from said tetrafluoro-ethylene, and provided that said continuous polymerization has an average residence time of about 5 seconds to about 30 minutes.
This invention also concerns an amorphous polymer, consisting essentially of repeat units of the formula:
(a) at least about 30 mole percent of
—CF
2
—CF(CF
3
)—  (I)
(b) at least about 1 mole percent
—CF
2
—CF
2
—  (II)
 and
(c) 0 to about 10 mole percent
wherein X is —C
n
F
2n+1
or —OC
n
F
2n+1
, m is 2, 3 or 4, and n is either an integer of 2 to 20 with alkyl groups —C
n
F
2n+1
or an integer of 1-20 with alkoxy groups —OC
n
F
2n+1
.
provided that in said polymer less than 20 mole percent of (I) is present in the form of triads.
The invention also concerns a continuous polymerization process, comprising, contacting at a pressure of about 41 MPa to about 690 MPa, and a temperature of about 200° C. to about 400° C., tetrafluoroethylene, hexafluoro-propylene, and a third monomer and a radical initiator, to produce an amorphous polymer which contains at least 15 mole percent, preferably 30 mole percent of repeat units derived from said hexafluoropropylene, at least 0-70 mole percent of repeat units derived from said tetrafluoroethylene, and 0-70 mole percent of repeat units derived from said third monomer, and provided that said continuous polymerization has an average residence time of about 5 seconds to about 30 minutes.
This invention also concerns a compound of the formula (C
4
F
9
)
2
NSCF
3
.
A novel compound herein is R
6
R
7
CFSO
2
R
8
wherein R
6
is perfluoroalkyl, perfluoroalkyl containing one or more ether oxygen atoms, perfluoroalkoxy or perfluoroalkoxy containing one or more ether oxygen atoms, R
7
is perfluoroalkyl or perfluoroalkyl containing one or more ether oxygen atoms, and R
8
is perfluoroalkyl. It is preferred that each of R
6
, R
7
and R
8
independently contain 1 to 30 carbon atoms. It is also preferred that R
8
is perfluoro-n-alkyl containing 1 to 20 carbon atoms. It is more preferred that R
6
is perfluoro-n-propoxy, R
7
is trifluoromethyl, and R
8
is perfluoro-n-octyl. This compound is useful as an initiator for the polymerizations described herein.
Also disclosed herein is an amorphous polymer containing repeat units derived from:
27-60 mole percent hexafluoropropylene, up to 35 mole percent total of one or more second monomers, and the balance tetrafluoroethylene, provided that at least one mole percent of TFE is present in the polymer, and wherein said second monomer is ethylene, vinyl fluoride, trifluoroethylene, 3,3,3-trifluoro-propene, 2,3,3,3-tetrafluoropropene, 4-bromo-3,3,4,4-tetrafluoro-1-butene, CH
2
═CHO(C═O)R
2
wherein R
2
is perfluoro-n-alkyl containing 1 to 8 carbon atoms, CH
2
═CHR
3
wherein R
3
is perfluoro-n-alkyl containing 1 to 8 carbon atoms, CH
2
═CH(C═O)OR
4
wherein R
4
is C
n
F
x
H
y
wherein x+y=2n+1 and n is 1 to 8, chlorotrifluoroethylene, or allyltrimethoxysilane;
27-60 mole percent hexafluoropropylene, up to 5 mole percent total of one or more fourth monomers and the balance tetrafluoroethylene, provided that the polymer contains at least 1 mole percent tetrafluoroethylene, wherein said fourth monomer is perfluorocyclopentene, perfluorocyclobutene, CF
2
═CFCF
2
CN, CF
2
═CFR
5
wherein R
5
is perfluoroalkyl optionally containing one or more of one or more ether groups, one cyano group, or one sulfonyl fluoride group, perfluoro-(2-metylene-4-methyl-1,3-dioxolane), perfluoro(2-methyl-2,3-dihydro-1,4-dioxin), or FSO
2
CF
2
CF
2
OCF(CF
3
)CF
2
OCF═CF
2
; or
up to 30 mole percent total of one or more second monomers and up to 5 mole percent total of one or more fourth monomers.
Described herein is an amorphous copolymer, consisting essentially of:
(a) >15 mole percent of the repeat unit
—CF(CF
3
)—CF
2
—  (I)
(b) at least 1 to about 60 mole percent of the repeat unit
—CF
2
—CF
2
—  (II)
(c) about 0.1 to about 85 mole percent of the repeat unit
—CH
2
—CF
2
—  (IV)
wherein no more than about 20 mole percent of (I) is present in triads.
Also described herein is an amorphous copolymer, consisting essentially of repeat units of the formula:
(a) >15 mole percent of the repeat unit
—CF(CF
3
)—CF
2
—  (I)
(c) about 0.1 to about 85 mole percent of the repeat unit
—CH
2
—CF
2
—  (IV)
wherein no more than about 20 mole percent of (I) is present in triads.
Described herein is an amorphous copolymer, consisting essentially of:
(a) >10 mole percent of the repeat unit
—CF(CF
3
)—CF
2
—  (I)
(b) up to about 32 mole percent of the repeat unit
—CF
2
—CF
2
—  (II)
(c) about 53 to about 85 mole percent of the repeat unit
—CH
2
—CF
2
—  (IV)
wherein the sequence
—(CH
2
CF
2
)—(CH
2
CF
2
)—(CF
2
CH
2
)—  (S1)
is present in an amount according to an equation
mole percent
S
1≧0.23(mole percent
VF
2 in polymer)−10.2.
DETAILS OF THE INVENTION
The TFE/HFP copolymer made herein is amorphous. By an amorphous polymer is meant that the polymer has a heat of melting of less than 1 J/g when measured by Differential Scanning Calorimetry (DSC) at a heating rate of 10° C./min, in the case of a TFE/HFP dipolymer. This is measured on a “first heat”, that is virgin polymer is heated to at least 300° C. in the DSC (at 10° C./min), and the heat of melting, if any, is measured. In the case of terpolymers, where the residual third monomer is often removed from the polymer by heating for about four hours, at 150° C., in a vacuum oven, DSC “second heats”, at 10° C./min to at least 200° C., were used.
These polymers are made via a continuous polymerization process in which the initial ingredients are fed to the reactor in an essentially continuous manner and in which the product stream is essentially continuously withdrawn at approximately the same rate at which the ingredients are added. Such types of reactions are generally known to the artisan, see for instance H. F. Mark, et al., Ed., Kirk-Othmer Encyclopedia of Chemical Technology, 3rd Ed., vol. 19, John Wiley & Sons, New York, 1982, p. 880-914. Such continuous reactors include continuous stirred tank reactors and pipeline (tubular) reactors. Under the conditions employed in the process as described herein, the productivity of the process is exceptionally high. By productivity herein is meant the weight of polymer produced in a unit volume of reactor in a unit volume of time. P

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