Hydro-fluoroalkylvinylethers and process for obtaining them

Details Hydro-fluoroalkylvinylethers and process for obtaining them Hydro-fluoroalkylvinylethers and process for obtaining them

1999-07-29

2001-10-09

Keys, Rosalynd (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C568S615000, C568S616000, C568S618000, C568S669000, C568S683000, C568S684000, C568S685000, C525S276000, C525S298000, C525S312000, C525S314000

Reexamination Certificate

active

06300526

ABSTRACT:

The present invention relates to fluoroalkylvinylethers showing high reactivity in the polymerization processes with totally or partially fluorinated ethylenically unsaturated monomers.
More specifically the present invention relates to hydro-fluoralkylvinylethers giving TFE polymers thermally more stable than the known hydro-fluoroalkylvinylethers, the hydrogen atoms being equal. Furthermore the fluoroalkyl-vinylethers of the invention are obtainable with high yields by an industrially simpler process in comparison with the known processes since it requires very mild reaction conditions.
It is known that partially or totally fluorinated fluoroalkylvinylethers are used to obtain thermoplastic or elastomeric fluorinated polymers, the commercial importance of which is based on their sole property combination, among which the high thermal and chemical stability.
It is known that some fluoropolymers, such as for example polytetrafluoroethylene, are processable with difficulty since they have a very high melt viscosity. In the art the tetrafluoroethylene (TFE) polymer processability is improved by TFE copolymerization with other ethylenically unsaturated molecules, such as for example (per)fluorovinyl-ethers.
The totally fluorinated vinylethers show low reactivity in the polymerization process. In these processes it is necessary to recover the unreacted vinylether, making the cost of the polymeric manufactured article more expensive.
The synthesis methods used to obtain hydrofluoroalkylvinylethers are unsatisfactory since they require an anhydrous reaction enrvironment, high TFE pressures and high reaction temperatures around 80-100° C.
GB patent 812,116 relates to hydro-fluorovinylethers having the formula CH
2
═CF—O—R
T
, wherein R
T
is equal to alkyl or to a fluorinated alkyl, their synthesis and polymerization. These vinylethers have an high reactivity and they easily copolymerize. The process for preparing the described vinylethers is carried out by reacting a R
T
—CH
2
—O
−
alcoholate with TFE giving yields of about 40%, but it requires rather drastic reaction conditions: high anhydricity, high TFE pressures (p>20 atm), high reaction temperatures in the range 85°-90° C.
EP patent 338,755 relates to a process for preparing perfluorinated copolymers comprising from 99.5% to 50% by moles of TFE and from 0.5% to 50% by moles of an hydrovinylether of formula CF
2
═CFOCH
2
C
n′
F
p
X′
m
H
(2n′+1−p−m)
(X′=Cl, Br, n′ is an integer comprising zero, p ranges from 0 to (2n′+1); m=0,1; p+m≦1n′+1). The copolymers obtained by reaction of the two monomers are fluorinated with elemental fluorine, obtaining more stable polymers. In the copolymers formed by TFE and CF
2
═CF—O—CH
2
—CF
2
—CF
3
the thermal degradation temperature of the non fluorinated polymer is 380° C. when the fluorovinylether molar percentage is 5.8% and it is 330° C. when the molar percentage is 25%. The thermal decomposition temperatures of the corresponding fluorinated polymers are higher than 60° C. and 80° C. respectively. This patent shows that the thermal stability of these copolymers depends on the vinylether amount and that the stability decreases as the molar percentage increases.
In the patent application WO 96/41823 elastomeric polymers obtained by TFE copolymerization with hydro-vinylethers of formula CF
2
═CF—O—R
B
wherein R
B
is a C
1
-C
6
alkyl group, are described. The thermal stability of the corresponding polymers with TFE is similar to that of the non fluorinated copolymers of EP 338,755.
The need was felt to have available hydro-fluorovinylethers ethers allowing to obtain polymers having an improved thermal stability.
The need was felt to have available a simpler process using milder reaction conditions and with high yields with respect to those of the prior art to obtain hydro-fluorovinylethers.
It has now been surprisingly and unexpectedly found that it is possible to meet said requirements with new hydro-fluorovinylethers giving TFE polymers with an improved thermal stability in comparison with the hydro-fluorovinylethers of the prior art (see for example EP 338,755 and Table 1).
It is an object of the present invention hydro-2,2-di-fluoroalkylvinylethers having the formula
CF
2
═CH—O—R
A
  (I)
wherein R
A
is an alkyl radical containing fluorine, optionally containing halogens such as Cl, Br, I; hydrogen, and R
A
is selected from the following:
linear or branched, saturated or unsaturated C
2
-C
20
fluoroalkyl group;
saturated or unsaturated C
4
-C
6
fluorinated cyclic group;
wherein optionally from 1 to 2 carbon atoms can be substituted with oxygen atoms forming ether bonds;
linear, branched saturated or unsaturated C
3
-C
15
fluorooxyalkylic group, containing one or more oxygen atoms forming ether bonds.
Preferably the R
A
radical has the following meanings:
CF
2
—R
C
wherein R
C
is selected from the following:
a linear or branched, saturated or unsaturated C
1
-C
19
fluoroalkyl group;
a linear or branched, saturated or unsaturated C
2
-C
14
fluorooxyalkyl group, containing one or more oxygen atoms forming ethereal bonds;
CF
2
—CFH—R
D
wherein R
D
is selected from the following:
a linear or branched, saturated or unsaturated C
1
-C
18
perfluoroalkyl group;
a linear or branched, saturated or unsaturated C
1
-C
13
perfluorooxyalkyl group, containing one or more oxygen atoms forming ether bonds.
R
A
optionally contains stable functional groups in the reaction conditions for the preparation of vinylether (I), for example, CN, COOR′, CON(R′)
2
, SO
2
OR′, wherein R′ is a linear or branched C
1
-C
5
alkyl.
The hydro-fluoroalkylvinylethers of the invention allow to obtain, the percentage by weight of the contained hydrogen being equal, polymers having an higher thermal stability than that of the polymers of the hydro-fluoroalkylvinyl-ethers of the prior art. See Table 1 for the TFE polymers.
The hydro-fluoroalkylvinylethers of the invention show in the polymerization an higher reactivity than the perfluorovinylethers of the art. See the Examples.
Polymers and copolymers can be obtained by copolymerizing with the hydro-fluoroalkylvinylethers of the present invention totally or partially fluorinated and non fluorinated comonomers having at least an unsaturation of ethylenic type.
Among the usable comonomers the following ones can be mentioned:
C
2
-C
8
perfluoroolefins, such as tetrafluoroethylene (TFE), hexafluoropropene (HFP), hexafluoroisobutene;
hydrogenated C
2
-C
8
fluorolefins, such as vinyl fluoride (VF) trifluoroethylene, perfluoroalkylethylene CH
2
═CH—R
f
, wherein R
f
is a C
1
-C
6
perfluoroalkyl;
chloro- and/or bromo- and/or iodo-C
2
-C
8
fluoroolefins, such as bromotrifluoroethylene;
(per)fluoroalkylvinylethers (PAVE) CH
2
═CFOR
f
, wherein R
f
is a C
1
-C
6
(per)fluoroalkyl, such as trifluoromethyl, bro-modifluoromethyl or heptafluoropropyl;
CF
2
═CFOX″ (per)fluoro-oxyalkylvinylethers, wherein X″ is: a C
1
-C
12
alkyl, or a C
1
-C
12
oxyalkyl, or a C
1
-C
12
(per)fluorooxyalkyl having one or more ether groups, for example perfluoro-2-propoxy-propyl;
perfluorodioxole (PD), perfluoro (2,2-dimethyl)-1,3-dioxole (PDD), perfluoro-4-methoxy-1,3-dioxole (TTD);
CF
2
═CF—O—CF
2
—O—CF═CF
2
(bis-vinyloxymethane, BVOM);
CF
2
═CF—O—CF
2
—CF
2—SO
2
F.
Optional comonomers which can be copolymerized are non fluorinated C
2
-C
6
olefins, such as ethylene, propylene, isobutylene.
The copolymerization products can be prepared by radical polymerizations, both in aqueous and organic medium.
In the polymerizations in aqueous medium, the polymerization initiator can be any substance able to produce radicals, such as for example peroxides, persulphates or azo-compounds. Optionally also a reducing agent can be used, such as for example an iron salt, in order to favour the initiator decomposition. Optionally, a chain transfer agent is used to obtain the desired molecular weight. The pol

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