Curable fluoroelastomers

Details Curable fluoroelastomers Curable fluoroelastomers

2002-04-23

2003-12-16

Wu, David W. (Department: 1713)

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

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C524S543000, C524S545000, C525S326300, C526S247000, C526S250000, C526S255000

Reexamination Certificate

active

06664338

ABSTRACT:

The present invention relates to curable fluoroelastomers, able to give cured fluoroelastomers with improved sealing properties, i.e. improved compression set on O-ring, improved mechanical properties shown as improved combination of stress and elongation at break.
More specifically the curable fluoroelastomers of the invention are cured by ionic route. The cured fluoroelastomers of the present invention are used in the preparation of O-rings, gaskets, shaft seals, fuel hoses, etc. The O-rings obtained with the curable invention compositions show an improved compression set value and an improved combination of stress at break and elongation at break. The shaft seals show an improved combination of stress at break and elongation at break. Besides the curable fluoroelastomers of the present invention crosslink in short times.
It is well known that one of the most important applications of fluoroelastomers relates to the preparation of O-rings. They are obtained from fluoroelastomeric copolymers based on units deriving from vinylidenfluoride (VDF), hexafluoropropene (HFP), optionally tetrafluoroethylene (TFE).
The fluoroelastomers used in said application must have high elastomeric properties at low and at high temperatures and must show a good processability so that they can be easily injection moulded with automatic cycles.
The need was felt to have available curable VDF-based fluoroelastomers to prepare the above manufactured articles having the optimal combination of the mentioned properties.
An object of the present invention are fluoroelastomers curable by ionic route based on vinylidene fluoride (VDF) comprising:
a) 100 parts by weight of fluoroelastomer based on vinylidene fluoride (VDF) substantially polar end group free;
b) from 0.05 to 5 phr of accelerant;
c) from 0.5 to 15 phr of curing agent;
d) from 1 to 40 phr of one or more inorganic acid acceptors, preferably bivalent metal oxides;
e) from 0 to 2.5 phr, preferably from 0 to 1.5 phr of one or more basic compounds preferably hydroxides of bivalent metals or of weak acid metal salts;
f) from 0 to 80 phr of reinforcing fillers.
The fluoroelastomers component a) comprise VDF copolymers containing at least another ethylenically unsaturated fluorinated comonomer. This can be selected for example from the following:
C
2
-C
8
perfluoroolefins, such as hexafluoropropene (HEP), tetrafluoroethylene (TFE);
C
2
-C
8
fluoroolefins containing hydrogen and/or chlorine and/or bromine and/or fluorine, such trifluoroethylene, pentafluoropropene, chlorotrifluoroetheylene (CTFE), bromotrifluoroethylene;
fluorovinylethers (VE) preferably selected from:
(per) fluoroalkylvinylethers (PAVE) CF
2
═CFOR
f
wherein R
f
is a C
1
-C
6
(per)fluoroalkyl, for example trifluoromethyl, bromodifluoromethyl, pentafluoropropyl;
perfluoro-oxyalkylvinylethers CF
2
═CFOX, wherein X is a C
1
-C
12
perfluoro-oxyalkyl having one or more ether groups, for example perfluoro-2-propoxy-propyl;
CF
2
═CFOCF
2
OCF
2
CF
3
(A-III) and CF
2
═CFOCF
2
OCF
2
CF
2
OCF
3
(A-IV).
The fluoroelastomers object of the present invention can also contain units deriving from non fluorinated ethylenically unsaturated monomers, in particular non fluorinated C
2
-C
3
olefins (Ol), such as ethylene and propylene.
In the polymer also small amounts in the range 0.01-5% by moles of units deriving from a fluorinated bis-olefin, can be present. The bis-olefins described in European patent 661,304, herein incorporated by reference, can for example be used.
Preferred compositions of the fluoroelastomers component a) are the following (% by moles):
VDF 45-35%, HFP 15-45%, TFE 0-3%;
VDF 20-30%, HFP 15-40%, TFE OL 5-30%, PAVE 0-35%;
VDF 60-75%, HFP 10-25%, VE 0-15%, TFE 0-20%.
The fluoroelastomers component a) as said are substantially polar end group free. With end groups, all the groups present at the ends of the main polymer chain or of the optionally present side chains, are meant. With polar groups it is meant groups both of ionic type, such carboxylate —COO
−
and sulphate —OSO
3
−
groups, and of non ionic type, such alcoholic —CH
2
OH, acylfluoride —COF, amidic −CONH
2
groups, and so on. With “substantially polar group free” it is meant that the amount of polar end groups is lower than 3% by moles, preferably lower than 1% by moles with respect to the total amount of the end groups present in the polymer, still more preferably it is zero. It is meant that the amount of polar groups is zero when the amount of each type of polar end groups present is lower than the detectability limit according to the method reported in the Examples, i.e. lower than 1 mmole/Kg of polymer.
The usable accelerant component b) is formed by an organic-onium derivative. The organic-onium derivatives usable for the invention generally contain at least one heteroatom, for example, N, P, S, O linked to organic or inorganic groups. The organic-onium compounds suitable to be used in the invention are for example those described in U.S. Pat. Nos. 3,655,727, 3,712,877, 3,857,807, 3,686,143, 3,933,732, 3,876,654, 4,233,421, 4,259,463, 4,882,390, 4,912,171, 5,591,804, EP 182,299, EP 120,462; West and Holcomb, “Fluorinated Elastomers”, Kirk-Othmer; Encyclopedia of Chemical Technology, vol. 8, 3rd Ed. John Wiley & Sons, Inc., pp. 500-515 (1979).
The organic -onium compounds which can be used belong for example to the following classes:
A) compounds having general formula:
wherein:
Q has the following meanings: nitrogen, phosphor, arsenic, antimony, sulphur;
X
I
is an organic or inorganic anion such for example halide, sulphate, acetate, phosphate, phosphonate, hydroxide, alkoxide, phenate, bisphenate;
n is the valence of the X
I
ion;
R
2
, R
3
, R
4
, R
5
, independently the one from the other, have the following meanings:
C
1
-C
20
alkyl, C
6
-C
20
aryl or arylalkyl, C
1
-C
20
alkenyls, or a combination thereof;
halogen, selected from chlorine, fluorine, bromine; or cyano groups, —OR
B
and COOR
B
, wherein R
B
. is an alkyl, aryl, arylalkyl or alkenyl having the above meanings;
wherein two radicals of the R
2
, R
3
, R
4
, R
5
group can form with the heteroatom Q a cyclic structure;
when Q is a sulphur atom one of the R
2
, R
3
, R
4
, R
5
radicals is not present;
B) amino-phosphonium derivatives having the following general formulas:
mI[
P(NR
6
R
7
)
n
IR
8
4−nI]
30
Y
mI−
  (II)
R
9
[P(NR
6
R
7
)
r
R
8
3−r
]
2+
p
Y
mI−
  (III)
wherein:
R
6
, R
7
and R
8
, equal or different, have the following meanings:
C
1
-C
18
, preferably C
1
-C
12
alkyl, cycloalkyl, C
6
-C
18
, preferably C
6
-C
12
, aryl or arylakyl;
oxyalkyl or poly(oxyalkyl) wherein the alkyl is as above and the polyoxyalkyl radical has a free or etherified terminal OH function; R
6
, R
7
and R
8
can optionally contain halogens, ON, OH, carbalkoxy groups; wherein R
6
and R
7
can form with the nitrogen atom an heterocyclic ring;
R
9
is a C
1
-C
6
bivalent alkylenic, oxyalkylenic or C
6
-C
12
arylenic radical;
nI is an integer from 1 to 4;
r is an integer from 1 to 3;
mI is an integer from to 1 to 2 and corresponds to the Y ion valence;
p is a coefficient such that mI×p=2;
Y is an anion having valence m and can be organic or inorganic; or example Y can be selected from halides, perchlorate, nitrate, tetrafluoroborate, hexafluorophosphate, oxalate, acetate, stearate, haloacetate, para-toluensulphonate, phenate, bisphenate, hydroxide; Y can also be a complex anion for example ZnCl
4
2−
, CdCl
4
2−
, NiBr
3
−
:
C) phosphoranes, in particular triarylphosphoranes, having formula:
wherein:
Ar is phenyl, substituted phenyl (as for example methoxyphenyl, chlorophenyl, tolyl), naphthyl;
R
10
is hydrogen, methyl, ethyl, propyl, carbalkoxy;
R
11
is carabalkoxy, C
1
-C
8
alkyls, cyano, and amidic;
or R
10
with the carbon, atom of the P═C bond forms a cyclic group, example cyclopentadiene;
D) iminium salts having formula
[N(R
12
)
2
]
c+
X
c
c−
  (V)
wherein:
R
12
is a mo

Affiliated with

Also associated with

Rating

Curable fluoroelastomers does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Curable fluoroelastomers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Curable fluoroelastomers will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3156613