Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-09-18
2002-02-12
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...
C526S227000, C526S230500, C526S231000, C526S242000
Reexamination Certificate
active
06346587
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for the production of partially fluorinated fluoropolymers, in accordance with which fluoromonomers are free-radically polymerized in the presence of polyfluoropropanes or polyfluorobutanes of the formulae CF
3
—CH
2
—CF
2
H, CF
3
—CHF—CF
2
H, CF
3
—CH
2
—CF
3
, CHF
2
—CF
2
—CH
2
F, CF
3
—CH
2
—CF
2
—CH
3
and CF
3
—CHF—CF
2
—CH
3
and optionally a chain-transfer agent.
BACKGROUND OF THE INVENTION
Fluoropolymers are produced on an industrial scale substantially using known aqueous emulsion or suspension polymerization processes, as described, for example, in
Modern Fluoropolymers
, John Wiley & Sons Ltd., Chichester, 1997, pp. 77 and 609. Water-soluble auxiliaries, such as fluorinated emulsifiers, dispersants, initiators etc. are required in these processes which, once the resultant polymer dispersion has been worked up, may be found in part in the product and in part in the waste water, where they cause problems with regard to product properties or the environmental compatibility of the process.
Non-aqueous processes have hitherto been based upon chlorofluorocarbons, such as 1,2-dichlorotetrafluoroethane or 1,1,2-trichlorofluoroethane. However, these compounds have an elevated ozone degrading potential, for which reason industrial use thereof is already prohibited in many industrial nations.
U.S. Pat. No. 4,243,770 mentions the possibility of using other inert compounds containing fluorine, such as perfluoro(1,2-dimethylcyclobutane), perfluorocyclohexane, perfluoro(tributylamine) and compounds of the type H(CF
2
)
n
H and CF
3
O(C
2
F
4
O)
n
CF
2
CF
3
, apart from the stated chlorofluorocarbons, as solvents for the polymerization of fluoromonomers.
U.S. Pat. No. 5,182,342 describes the use of fluorinated hydrocarbons which satisfy certain criteria with regard to the F/H ratio and the position of the hydrogen atoms and may optionally contain ether oxygen atoms for this purpose, such as for example 1,1,2,2-tetrafluorocyclobutane, 1-trifluoromethyl-1,2,2-trifluorocyclobutane, CF
3
(CF
2
)
n
CFH(CF
2
)
m
CF
3
, CF
3
(CF
2
)
n
CFHCFH(CF
2
)
m
CF
3
, CF
3
(CF
2
)
n
CH
2
(CF
2
)
m
CF
3
, CF
3
(CF
2
)
n
CFHCH
2
(CF
2
)
m
CF
3
, C
4
F
9
CH
2
CH
2
C
4
F
9
. However, compounds which, with the exception of the permitted structural unit —CF
2
OCH
3
, contain a hydrogen atom on the terminal (primary) C atom are explicitly excluded.
Fluorinated hydrocarbons having terminal hydrogen atoms, for example CF
3
(CF
2
)
n
H, CF
3
(CF
2
)
n
CH
2
CH
3
, as well as those of the type CF
3
CF(CF
3
)CFHCFHCF
3
, are described in U.S. Pat. No. 5,494,984 in addition to those mentioned above as polymerization media for fluoromonomers.
It has not hitherto been possible to use fluorinated hydrocarbons having fewer than 4 C atoms in known processes for the production of fluoropolymers. The compounds hitherto used have also been very highly fluorinated compounds, in which partially fluorinated fluoropolymers, which also comprise —CH
2
sequences in addition to fluoro-substituted carbon atoms, are very sparingly soluble. Moreover, on grounds of price and availability, none of these compounds is suitable as a polymerization medium. The production thereof generally proceeds by oligomerization/telomerisation of fluoromonomers (tetrafluoroethylene, hexafluoropropene, hexafluoropropene oxide) and subsequent hydrogenation or hydrogen fluoride addition.
However, increasing the H/F ratio as a pre-requisite for improving polymer solubility generally results in an increase in the transfer potential, which is undesirable for a polymerization solvent, as this latter property is usually also associated with a terminating chain transfer.
SUMMARY OF THE INVENTION
The object of the present invention was accordingly to provide a simple production process for partially fluorinated fluoropolymers which operates without using ozone-damaging compounds.
It has now been found that partially fluorinated fluoropolymers may be produced in a very simple manner by using certain polyfluoropropanes or polyfluorobutanes.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a process for the production of partially fluorinated fluoropolymers, in accordance with which fluoromonomers are free-radically polymerization in the presence of fluorinated hydrocarbons of the formulae CF
3
—CH
2
—CF
2
H, CF
3
—CHF—CF
2
H, CF
3
—CH
2
—CF
3
, CHF
2
—CF
2
—CH
2
F, CF
3
CH
2
—CF
2
—CH
3
and/or CF
3
—CHF—CF
2
—CH
3
, preferably 1,1,1,3,3-pentafluoropropane, and optionally a chain-transfer agent.
Partially fluorinated fluoropolymers for the purposes of the invention have a main chain formed of carbon atoms, which chain also comprises —CH
2
sequences as well as fluoro-substituted sequences. These may be either homo- or copolymers of vinylidene fluoride with other fluorinated and also non-fluorinated monomers or copolymers of fluorinated monomers, containing no hydrogen, with non-fluorinated monomers.
Fluoromonomers which may be used for the purposes of the invention are fluorinated, optionally substituted ethylenes, which, apart from fluorine, may contain hydrogen and/or chlorine, such as for example vinylidene fluoride, tetrafluoroethylene and chlorotrifluoroethylene, fluorinated 1-alkenes having 2-8 carbon atoms, such as for example hexafluoropropene, 3,3,3-trifluoropropene, chloropentafluoropropene, hexafluoroisobutene and/or perfluorinated vinyl ethers of the formula CF
2
═CF—O—X, where X=C
1
-C
3
perfluoroalkyl or —(CF
2
—CFY—O)
n
—R
F
, wherein n=1-4, Y=F or CF
3
and R
F
=C
1
-C
3
perfluoroalkyl.
Olefins containing no fluorine, such as ethylene, propene, isobutene, alkyl vinyl ethers or vinyl esters, such as for example vinyl acetate, which are copolymerizable with fluoromonomers may furthermore additionally be used as comonomers.
Examples of such copolymer combinations are, for example, vinylidene fluoridelhexafluoropropene, optionally together with tetrafluoroethylene and/or perfluoro(methyl vinyl ether), tetrafluoroethylene/ethylene, tetrafluoroethylene/vinylidene fluoride, tetrafluoroethylene/propene, tetrafluoroethylene/propene/vinylidene fluoride and tetrafluoroethylene/vinyl acetate.
It is additionally possible also to use copolymerizable monomers containing iodine or bromine, such as for example bromotrifluoroethylene, 4bromo-3,3,4,4-tetrafluoro-1-butene, as described in U.S. Pat. No. 4,035,565, or 1-bromo-2,2-difluoroethylene for the production of peroxide-vulcanisable fluororubbers.
In a preferred embodiment of the invention, water is additionally present in a quantity of 10 to 900 parts by weight relative to 100 parts by weight of the polyfluoropropenes or polyfluorobutanes used according to the invention.
The free-radical polymerization is preferably initiated by means of initiators.
Organic or fluoro-organic dialkyl peroxides, diacyl peroxides, dialkyl peroxy-dicarbonates, alkyl peresters and/or perketals, such as for example tert.-butyl peroxypivalate, tert.-butyl peroxy-2-thylhexanoate, dicyclohexyl peroxydicarbonate, bis(trifluoroacetyl peroxide) or the peroxide of hexafluoropropene oxide dimers {(CF
3
CF
2
CF
2
O CF(CF
3
)COO}
2
are preferably used as the initiator. The initiator which is used and the quantity in which it is used is determined by the particular reaction temperature, at which the half-life of the peroxide to be selected should be between 30 and 500 min. Quantities of between 0.05 and 1.0 part by weight of peroxide per 100 parts by weight of monomers to be reacted are preferred.
When the polymerization is performed as suspension or emulsion polymerisation in the presence of water, which is additionally added to the fluorinated hydrocarbons according to the invention, it is also possible to use water-soluble initiators or redox systems, in which one or both of the components (reducing and oxidizing agent) are water-soluble, such as for example potassium peroxydisulfate, potassium permanganate/oxalic acid or peroxydisulfate/perfluoroalkyl sulfinate.
The molecular weights and thus the viscositie
Heilig Gerhard
Krüger Ralf
Sommerfeld Claus Dieter
Bayer Aktiengesellschaft
Cheung Noland J.
Gil Joseph C.
Zitomer Fred
LandOfFree
Method for the production of partially fluorinated... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for the production of partially fluorinated..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for the production of partially fluorinated... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2985103