Perfluoroelastomers

Details Perfluoroelastomers Perfluoroelastomers

2002-10-16

2003-11-04

Teskin, Fred (Department: 1713)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S206000, C526S242000, C525S326300, C525S366000, C525S368000, C525S369000, C525S370000, C525S371000, C525S372000

Reexamination Certificate

active

06642331

ABSTRACT:

The present invention relates to perfluoroelastomers having a very good combination of mechanical properties, compression set and at low temperature properties and to the process for preparation thereof.
It is well known that perfluoroalkylvinylethers are generally used as monomers for the copolymerization with tetrafluoroethylene (TFE) to obtain perfluoroelastomers which are used in the space-, oil-, petrochemical and semiconductor industry. The introduction of perfluorovinylether high amounts in crosslinkable fluoroelastomers implies elasticity properties at low temperature of fluorinated rubbers.
The need was felt to have available perfluoroelastomers having improved properties at low temperatures in combination with good mechanical and compression set properties.
To solve said technical problem fluorovinylethers with various structural properties have been proposed in the prior art. However from the prior art the obtained perfluoroelastomers do not show the combination of the above properties.
U.S. Pat. No. 3,132,123 describes the preparation of perfluoroalkylvinylethers, of the respective homopolymers and copolymers with TFE. The homopolymers are obtained under extreme experimental conditions, by using polymerization pressures from 4,000 to 18,000 atm. The homopolymer of the perfluoromethylvinylether (MVE) is an elastomer: however its Tg is not sufficiently low. The general formula of the described vinylethers is the following:
CF
2
═CFOR
0
F
wherein R
0
F
is a perfluoroalkyl radical preferably from 1 to 5 carbon atoms.
U.S. Pat. No. 3,450,684 relates to vinylethers of formula:
CF
2
═CFO(CF
2
CFX
0
O)
n′
CF
2
CF
2
X
0
wherein X
0
═F, Cl, CF
3
, H; n′ can range from 1 to 20.
Homopolymers obtained by UV polymerization are also described. The exemplified copolymers are not characterized with their mechanical and elastomeric properties at low temperatures.
U.S. Pat. No. 3,817,960 relates to the preparation and polymerization of perfluorovinylethers of formula:
CF
3
O(CF
2
O)
n″
CF
2
CF
2
OCF═CF
2
wherein n″ can range from 1 to 5. Characterization data on the above properties are not described.
U.S. Pat. No. 4,487,903 relates to the fluoroelastomeric copolymer preparation wherein perfluorovinylethers of formula:
CF
2
═CF(OCF
2
CFY
0
)
n
0
OX
2
are used, wherein n
0
ranges from 1 to 4; Y
0
═F, Cl, CF
3
, H; X
2
can be C
1
-C
3
perfluoroalkyl, C
1
-C
3
&ohgr;-hydroperfluoroalkyl, C
1
-C
3
&ohgr;-chloroperfluoroalkyl. The polymer has a fluorovinylether unit content ranging from 15 to 50% by moles. Said vinylethers give copolymers having at low temperatures properties superior to those of the above perfluorovinylethers of PVE (perfluoropropylvinylether) and MVE type. Also in this case data relating to the above properties of the cured elastomer are not indicated.
EP 130,052 describes the polymerization of the perfluorovinylpolyethers (PVPE) which leads to the obtainment of amorphous perfluoropolymers having a T
g
ranging from −15° to −100° C. The described polymers have T
g
values which reach −76° C.; the further T
g
decrease is obtained by using perfluoropolyethers as plasticizers. In the patent copolymers and terpolymers of TFE and MVE with vinylethers (PVPE) of formula:
CF
2
═CFO(CF
2
CF(CF
3
)O)
n′″
R
0
f′
are described, wherein n′″ ranges from 3 to 30 and R
0
f′
is a perfluoroalkyl. Due to purification difficulties, the used vinylethers are mixtures of vinylethers with different values of n′″. According to this patent the most marked effect on the T
g
decrease is shown when n′″ is equal to or higher than 3, preferably higher than 4.
U.S. Pat. No. 4,766,190 relates to the polymerization of perfluorovinylpolyethers (PVPE), similar to those described in U.S. Pat. No. 4,487,903, with TFE and low percentages of perfluoro propene, to increase the mechanical properties of the obtained polymers. No improvement of the mechanical and elastomeric properties at low temperatures is described.
U.S. Pat. No. 5,268,405 discloses the preparation of perfluorinated rubbers having a low Tg, by using perfluoropolyethers having a high viscosity as plasticizers of perfluorinated rubbers (TFE/MVE copolymers). The obtained manufactured articles have the drawback that during the use, exudations of the perfluoropolyethers (PFPE) take place, in particular when PFPE has low molecular weight (low viscosity): in the patent it is therefore disclosed the use of PFPE having high viscosity; those having low viscosity must be previously removed.
U.S. Pat. No. 5,401,818 relates to the perfluorovinylether preparation of formula:
R
1
f
(OCF
2
CF
2
CF
2
)
m′
—OCF═CF
2
(wherein R
1
f
is a C
1
-C
3
perfluoroalkyl radical; m′ is an integer raanging from 1 to 4) and of the respective copolymers having improved properties at low temperature. The preparation of said perfluorovinylethers requires also a perfluorination with elementary F
2
which from the industrial point of view requires supplementary process unities.
Furthermore it is well known that by increasing the perfluorooxyalkylene units which are part of the side perfluorooxyalkylene substituent of perfluorooxyalkylvinylethers, the Tg of the obtained amporphous copolymers decreases. However it is not possible to obtain polymers with the optimal combination of the above properties.
The amorphous copolymers of TFE with perfluoromethylvinylether have T
g
of about 0° C. or a little lower (Maskornik, M. et al. “ECD-006 Fluoroelastomer—A high performance engineering material”. Soc. Plast Eng. Tech. Pao. (1974), 20, 675-7). The extrapolated value of the MVE homopolymer T
g
is of about −5° C. (J. Macromol. Sci.-Phys., B1(4), 815-830, December 1967).
In patent application EP 1,148,072 fluorovinylethers allowing to lower the Tg of the respective copolymers are described, but the mechanical and elastomeric properties of the obtained manufactured articles are not described.
The perfluoroelastomers described in the prior art do not show the optimal combination of the above properties, in particular it would be desirable to have available perfluoroelastomers which when cured show the following combination of properties:
good mechanical and elastomeric properties,
high resistance to low temperatures such as for example shown by TR 10 (ASTM D 1329 method),
much lower Tg with respect to vinylethers having the same oxygen number and carbon atoms,
maintenance of good mechanical and elastomeric properties even at high temperatures to have a high thermal range of the perfluoroelastomer use,
higher productivity of perfluoroelastomer in Kg of polymer/(hour×liter of water).
The Applicant has surprisingly and unexpectedly found that it is possible to solve the above technical problem as described hereinafter.
An object of the present invention are perfluoroelastomers, curable by peroxidic route, obtainable by polymerizing the following monomers:
a) tetrafluoroethylene (TFE);
b) fluorovinylethers of general formula:
CFX═CXOCF
2
OR  (I)
 wherein
R has the following meanings:
C
2
-C
6
linear or branched (per)fluoroalkyl,
C
5
-C
6
cyclic (per)fluoroalkyl,
C
2
-C
6
linear or branched (per)fluoro oxyalkyl, containing from one to three oxygen atoms,
X═F, H;
c) bis-olefins having general formula:
R
I
1
R
I
2
C═CR
I
3
—Z—CR
I
4
═CR
I
5
R
I
6
  (IA)
 wherein
R
I
1
, R
I
2
, R
I
3
, R
I
4
, R
I
5
, R
I
6
equal to or different from each other, are H or C
1
-C
5
alkyl;
Z is a C
1
-C
18
linear or branched alkylene or C
4
-C
18
cycloalkylene radical, optionally containing oxygen atoms, preferably at least partially fluorinated, or a (per)fluoropolyoxyalkylene radical;
d) optionally, one or more fluorinated olefinic comonomers selected from the following:
C
3
-C
8
perfluoroolefins, such hexafluoropropene (HFP), and/or chlorotrifluoroethylene (CTFE);
perfluoroalkylvinylethers (PAVE) CF
2
═CFOR
2
f′
wherein R
2
f
is a C
1
-C
6
perfluoroalkyl, for example t

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