U.S. patent application number 09/745097 was filed with the patent office on 2001-07-19 for fluoroelastomer, production thereof, crosslinkable composition and curing product.
Invention is credited to Abe, Katsumi, Tatsu, Haruyoshi.
Application Number | 20010008922 09/745097 |
Document ID | / |
Family ID | 18482914 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008922 |
Kind Code |
A1 |
Abe, Katsumi ; et
al. |
July 19, 2001 |
Fluoroelastomer, production thereof, crosslinkable composition and
curing product
Abstract
A fluoroelastomer comprising constituent units derived from
vinylidene fluoride (a) and constituent units derived from
perfluoro(methoxypropyl vinyl ether) (b), optionally together with
constituent units derived from tetrafluoroethylene (c) and/or
constituent units derived from a perfluoroalkyl vinyl ether (d),
wherein the constituent units (a) are contained in an amount of 65
to 85 mol %, the constituent units (b) in an amount of 0.5 to 30
mol %, the constituent units (c) in an amount of 0 to 10 mol % and
the constituent units (d) in an amount of 0 to 25 mol %. The
fluoroelastomer can be produced by a process comprising
copolymerizing vinylidene fluoride and perfluoro(methoxypropyl
vinyl ether), optionally together with tetrafluoroethylene and/or a
perfluoroalkyl vinyl ether, in the presence of an iodated
brominated compound represented by the general formula
RBr.sub.nI.sub.m [I]. Further, there is provided a crosslinkable
composition comprising the above fluoroelastomer and a peroxide
crosslinking agent. Still further, there is provided a curing
product produced by curing the above crosslinkable composition, and
having excellent resistances to heat, cold and solvents.
Inventors: |
Abe, Katsumi;
(Chigasaki-shi, JP) ; Tatsu, Haruyoshi;
(Hitachi-shi, JP) |
Correspondence
Address: |
Russell D. Orkin
700 Koppers Building
436 Seventh Avenue
Pittsburgh
PA
15219-1818
US
|
Family ID: |
18482914 |
Appl. No.: |
09/745097 |
Filed: |
December 20, 2000 |
Current U.S.
Class: |
525/326.3 ;
526/247; 526/255 |
Current CPC
Class: |
C08K 5/14 20130101; C08K
5/14 20130101; C08L 27/16 20130101 |
Class at
Publication: |
525/326.3 ;
526/247; 526/255 |
International
Class: |
C08F 008/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 1999 |
JP |
364885/1999 |
Claims
What is claimed is:
1. A fluoroelastomer comprising: constituent units derived from
vinylidene fluoride (a), and constituent units derived from
perfluoro(methoxypropyl vinyl ether) (b), optionally together with
constituent units derived from tetrafluoroethylene (c) and/or
constituent units derived from a perfluoroalkyl vinyl ether (d),
wherein: the constituent units (a) are contained in an amount of 65
to 85 mol %, the constituent units (b) are contained in an amount
of 0.5 to 30 mol %, the constituent units (c) are contained in an
amount of 0 to 10 mol %, and the constituent units (d) are
contained in an amount of 0 to 25 mol %.
2. The fluoroelastomer as claimed in claim 1, wherein the
constituent units (b) are contained in an amount of 6 to 25 mol
%.
3. The fluoroelastomer as claimed in claim 1 or 2, further
comprising constituent units (e) derived from a brominated
compound, an iodated compound or an iodated brominated compound
represented by the general formula: RBr.sub.nI.sub.m [I] wherein R
represents any of a fluorohydrocarbon group, a
chlorofluorohydrocarbon group, a chlorohydrocarbon group and a
hydrocarbon group, these groups optionally having a functional
group X, X representing --O--, --S--, .dbd.NR, --COOH, --SO.sub.2,
--SO.sub.3H or --PO.sub.3H; and each of n and m is 0, 1 or 2.
4. The fluoroelastomer as claimed in claim 3, wherein the
constituent units (e) are contained in an amount of 0.001 to 5
parts by weight per 100 parts by weight of the sum of the
constituent units (a), (b), (c) and (d).
5. A process for producing a fluoroelastomer, comprising
copolymerizing vinylidene fluoride and perfluoro(methoxypropyl
vinyl ether), optionally together with tetrafluoroethylene and/or a
perfluoroalkyl vinyl ether, in the presence of a compound
represented by the general formula: RBr.sub.nI.sub.m [I] wherein R
represents any of a fluorohydrocarbon group, a
chlorofluorohydrocarbon group, a chlorohydrocarbon group and a
hydrocarbon group, these groups optionally having a functional
group X, X representing --O--, --S--, .dbd.NR, --COOH, --SO.sub.2,
--SO.sub.3H or --PO.sub.3H; and each of n and m is 0, 1 or 2.
6. A crosslinkable composition comprising the fluoroelastomer
claimed in claims 1, 2 and 4 and a peroxide crosslinking agent.
7. A curing product produced by curing the crosslinkable
composition claimed in claim 6.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a fluoroelastomer, a
process for producing the fluoroelastomer, a crosslinkable
composition containing the fluoroelastomer and a curing product
from the crosslinkable composition.
BACKGROUND OF THE INVENTION
[0002] Properties such as resistances to heat, cold and solvents
(including fuel oil and other oils) are required for molded items
such as oil seals and fuel hoses for automobiles, aircrafts, etc.
Thus, there is a demand for the development of resin materials
which possess these properties in desirable balance.
[0003] For example, Japanese Patent Publication No. 54(1979)-1585
describes a fluorinated polymer composition comprising an organic
peroxide and a fluorinated polymer obtained by copolymerization
with an olefin containing 3 mol % or less of bromine. However, the
product of peroxide crosslinking obtained from this composition,
although exhibiting cold resistance to a certain extent, has a
drawback in that the solvent resistance is poor.
[0004] On the other hand, Japanese Patent Publication No.
58(1983)-4728 describes a fluorinated multisegmented polymer
obtained by copolymerization with the use of an iodated compound as
a chain transfer agent. However, because the iodated compound used
as a chain transfer agent has a small molecular weight, there is a
problem that an improvement of cold resistance cannot be expected
at all.
[0005] The inventors have made extensive and intensive studies with
a view to solve the above problems of the prior art. As a result,
it has been found that, when use is made of a crosslinkable
composition containing a specified fluoroelastomer, there can be
obtained a curing product which is excellent in resistances to
heat, cold and solvents. The present invention has been
accomplished on the basis of this finding.
OBJECT OF THE INVENTION
[0006] An object of the present invention is to solve the above
problems of the prior art. Specifically, objects of the present
invention are to provide a fluoroelastomer from which a curing
product excellent in resistances to heat, cold and solvents, can be
obtained and to provide a crosslinkable composition containing the
same and a curing product therefrom.
SUMMARY OF THE INVENTION
[0007] The fluoroelastomer of the present invention comprises:
[0008] constituent units derived from vinylidene fluoride (a),
and
[0009] constituent units derived from perfluoro(methoxypropyl vinyl
ether) (b),
[0010] optionally together with constituent units derived from
tetrafluoroethylene (c) and/or constituent units derived from a
perfluoroalkyl vinyl ether (d),
[0011] wherein:
[0012] the constituent units (a) are contained in an amount of 65
to 85 mol %,
[0013] the constituent units (b) are contained in an amount of 0.5
to 30 mol %,
[0014] the constituent units (c) are contained in an amount of 0 to
10 mol %, and
[0015] the constituent units (d) are contained in an amount of 0 to
25 mol %.
[0016] It is preferred that the constituent units (b) be contained
in an amount of 6 to 25 mol %.
[0017] The fluoroelastomer of the present invention may further
comprise constituent units (e) derived from a brominated compound,
iodated compound or iodated brominated compound represented by the
general formula:
RBr.sub.nI.sub.m [I]
[0018] wherein R represents any of a fluorohydrocarbon group, a
chlorofluorohydrocarbon group, a chlorohydrocarbon group and a
hydrocarbon group, these groups optionally having a functional
group X, X representing --O--, --S--, .dbd.NR, --COOH, --SO.sub.2,
--SO.sub.3H or --PO.sub.3H; and each of n and m is 0, 1 or 2.
[0019] The above constituent units (e) are preferably contained in
an amount of 0.001 to 5 parts by weight per 100 parts by weight of
the sum of the constituent units (a), (b), (c) and (d).
[0020] The process for producing a fluoroelastomer according to the
present invention comprises copolymerizing vinylidene fluoride and
perfluoro(methoxypropyl vinyl ether), optionally together with
tetrafluoroethylene and/or a perfluoroalkyl vinyl ether, in the
presence of a compound represented by the general formula:
RBr.sub.nI.sub.m [I]
[0021] wherein R represents any of a fluorohydrocarbon group, a
chlorofluorohydrocarbon group, a chlorohydrocarbon group and a
hydrocarbon group, these groups optionally having a functional
group X, X representing --O--, --S--, .dbd.NR, --COOH, --SO.sub.2,
--SO.sub.3H or --PO.sub.3H; and each of n and m is 0, 1 or 2.
[0022] The crosslinkable composition of the present invention
comprises the above fluoroelastomer and a peroxide crosslinking
agent. The curing product of the present invention is produced by
curing this crosslinkable composition.
BRIEF DESCRIPTION OF THE DRAWING
[0023] FIG. 1 is a chart of .sup.19F-NMR spectrum of the
fluoroelastomer obtained in Example 1.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The fluoroelastomer, process for producing the same, the
crosslinkable composition and the curing product therefrom
according to the present invention will be described in detail
below.
[Fluoroelastomer]
[0025] The fluoroelastomer of the present invention is a copolymer
comprising constituent units derived from vinylidene fluoride (a)
and constituent units derived from perfluoro(methoxypropyl vinyl
ether) (b), optionally together with constituent units derived from
tetrafluoroethylene (c) and/or constituent units derived from a
perfluoroalkyl vinyl ether (d).
[0026] Vinylidene fluoride from which the constituent units (a) can
be derived, perfluoro(methoxypropyl vinyl ether)
[CF.sub.2.dbd.CFOCF.sub.2CF- .sub.2CF.sub.2OCF.sub.3] from which
the constituent units (b) can be derived and tetrafluoroethylene
from which the constituent units (c) can be derived can be produced
by known processes. These are also commercially available.
[0027] The perfluoroalkyl vinyl ether from which the constituent
units (d) according to the present invention can be derived may be,
for example, any of perfluoro(methyl vinyl ether), perfluoro(ethyl
vinyl ether) and perfluoro(propyl vinyl ether). Of these,
perfluoro(methyl vinyl ether) is preferably employed. These
perfluoroalkyl vinyl ethers can be produced by known processes and
are also commercially available.
[0028] The fluoroelastomer may further comprise constituent units
(e) derived from a brominated compound, iodated compound or iodated
brominated compound represented by the general formula:
RBr.sub.nI.sub.m [I]
[0029] wherein R represents any of a fluorohydrocarbon group, a
chlorofluorohydrocarbon group, a chlorohydrocarbon group and a
hydrocarbon group, and each of n and m is 0, 1 or 2.
[0030] These compounds are not limited as long as chain transfer
and other effects are not lost by any side reactions under
conditions of polymerization. For example, the group R is generally
selected from among fluorohydrocarbon groups,
chlorofluorohydrocarbon groups, chlorohydrocarbon groups and
hydrocarbon groups each having 1 to 10 carbon atoms. All the groups
may have a functional group, such as --O--, --S--, .dbd.NR, --COOH,
--SO.sub.2, --SO.sub.3H or --PO.sub.3H, bonded thereto.
[0031] The compound represented by the general formula [I] can be a
brominated compound, an iodated compound or an iodated brominated
compound.
[0032] The brominated compound may be, for example, any of
brominated vinyl compounds and brominated olefins, such as vinyl
bromide, 1-bromo-2,2-difluoroethylene, perfluoroallyl bromide,
4-bromo-1,1,2-trifluorobutene, 4-bromo-3,3,4,4-tetrafluorobutene,
4-bromo-1,1,3,3,4,4-hexafluorobutene, bromotrifluoroethylene,
4-bromo-3-chloro-1,1,3,4,4-pentafluorobutene,
6-bromo-5,5,6,6-tetrafluoro- hexene, 4-bromoperfluorobutene-1 and
3,3-difluoroallyl bromide.
[0033] Among the iodated brominated compounds represented by the
general formula [I], saturated or unsaturated aliphatic or aromatic
iodated brominated compounds wherein n and m are simultaneously 1
are preferably employed. When one of n and m is 2, formed
fluoroelastomer has a three-dimensional structure. Therefore, such
a compound is preferably used in such an amount that any
processability deterioration would not be caused.
[0034] The iodated brominated chain compound of the general formula
[I] can be, for example, any of 1-bromo-2-iodoperfluoroethane,
1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane,
2-bromo-3-iodoperfluorobutane,
1-bromo-2-iodoperfluoro(2-methylpropane),
monobromomonoiodoperfluorocyclobutane,
monobromomonoiodoperfluoropentane,
monobromomonoiodoperfluoro-n-octane,
monobromomonoiodoperfluorocyclohexan- e,
1-bromo-1-iodo-2-chloroperfluoroethane,
1-bromo-2-iodo-2-chloroperfluor- oethane,
1-iodo-2-bromo-2-chloroperfluoroethane, 1,1-dibromo-2-iodoperfluo-
roethane, 1,2-dibromo-2-iodoperfluoroethane,
1,2-diiodo-2-bromoperfluoroet- hane,
1-bromo-2-iodo-1,2,2-trifluoroethane,
1-iodo-2-bromo-1,2,2-trifluoro- ethane,
1-bromo-2-iodo-1,1-difluoroethane, 1-iodo-2-bromo-1,1-difluoroetha-
ne, 1-bromo-2-iodo-1-fluoroethane, 1-iodo-2-bromo-1-fluoroethane,
1-bromo-2-iodo-1,1,3,3,3-pentafluoropropane,
1-iodo-2-bromo-1,1,3,3,3-pen- tafluoropropane,
1-bromo-2-iodo-3,3,4,4,4-pentafluorobutane,
1-iodo-2-bromo-3,3,4,4,4-pentafluorobutane,
1,4-dibromo-2-iodoperfluorobu- tane,
2,4-dibromo-1-iodoperfluorobutane,
1,4-diiodo-2-bromoperfluorobutane- ,
1,4-dibromo-2-iodo-3,3,4,4-tetrafluorobutane,
1,4-diiodo-2-bromo-3,3,4,4- -tetrafluorobutane,
1,1-dibromo-2,4-diiodoperfluorobutane,
1-bromo-2-iodo-1-chloroethane, 1-iodo-2-bromo-1-chloroethane,
1-bromo-2-iodo-2-chloroethane, 1-bromo-2-iodo-1,1-dichloroethane,
1,3-dibromo-2-iodoperfluoropropane,
2,3-dibromo-2-idoperfluoropropane,
1,3-diiodo-2-bromoperfluoropropane, 1-bromo-2-iodoethane,
1-bromo-2-iodopropane, 1-iodo-2-bromopropane, 1-bromo-2-iodobutane,
1-iodo-2-bromobutane,
1-bromo-2-iodo-2-trifluoromethyl-3,3,3-trifluoropro- pane,
1-iodo-2-bromo-2-trifluoromethyl-3,3,3-trifluoropropane,
1-bromo-2-iodo-2-phenylperfluoroethane,
1-iodo-2-bromo-2-phenylperfluoroe- thane,
3-bromo-4-iodoperfluorobutene-1, 3-iodo-4-bromoperfluorobutene-1,
1-bromo-4-iodoperfluorobutene-1, 1-iodo-4-bromoperfluorobutene-1,
3-bromo-4-iodo-3,4,4-trifluorobutene-1,
4-bromo-3-iodo-3,4,4-trifluorobut- ene-1,
3-bromo-4-iodo-1,1,2-trifluorobutene-1,
4-bromo-5-iodoperfluoropent- ene-1,
4-iodo-5-bromoperfluoropentene-1,
4-bromo-5-iodo-1,1,2-trifluoropen- tene-1,
4-iodo-5-bromo-1,1,2-trifluoropentene-1, 1-bromo-2-iodoperfluoroet-
hyl perfluoromethyl ether, 1-bromo-2-iodoperfluoroethyl
perfluoroethyl ether, 1-bromo-2-iodoperfluoroethyl perfluoropropyl
ether, 2-bromo-3-iodoperfluoropropyl perfluorovinyl ether,
1-bromo-2-iodoperfluoroethyl perfluorovinyl ether,
1-bromo-2-iodoperfluoroethyl perfluoroallyl ether,
1-bromo-2-iodoperfluoroethyl methyl ether,
1-iodo-2-bromoperfluoroethyl ethyl ether, 1-iodo-2-bromoethyl ethyl
ether and 1-bromo-2-iodoethyl 2'-chloroethyl ether. These iodated
brominated compounds can be produced by appropriate known
processes. For example, fluorinated monobromomonoiodoolefins can be
obtained by reacting iodine bromide with fluorinated olefins.
[0035] The aromatic iodated brominated compound among the iodated
brominated compounds can be, for example, any of substituted
benzenes such as 1-iodo-2-bromo-, 1-iodo-3-bromo-, 1-iodo-4-bromo-,
3,5-dibromo-1-iodo-, 3,5-diiodo-1-bromo-,
1-(2-iodoethyl)-4-(2-bromoethyl- )-,
1-(2-iodoethyl)-3-(2-bromoethyl)-,
1-(2-iodoethyl)-4-(2-bromoethyl)-,
3,5-bis(2-bromoethyl)-1-(2-iodoethyl)-,
3,5-bis(2-iodoethyl)-1-(2-bromoet- hyl)-,
1-(3-iodopropyl)-2-(3-bromopropyl)-,
1-(3-iodopropyl)-3-(3-bromopro- pyl)-,
1-(3-iodopropyl)-4-(3-bromopropyl)-,
3,5-bis(3-bromopropyl)-1-(3-io- dopropyl)-,
1-(4-iodobutyl)-3-(4-bromobutyl)-, 1-(4-iodobutyl)-4-(4-bromob-
utyl)-, 3,5-bis(4-iodobutyl)-1-(4-bromobutyl)-,
1-(2-iodoethyl)-3-(3-bromo- propyl)-,
1-(3-iodopropyl)-3-(4-bromobutyl)-, 3,5-bis(3-bromopropyl)-1-(2--
iodoethyl)-, 1-iodo-3-(2-bromoethyl)-, 1-iodo-3-(3-bromopropyl)-,
1,3-diiodo-5-(2-bromoethyl)-, 1,3-diiodo-5-(3-bromopropyl)-,
1-bromo-3-(2-iodoethyl)-, 1-bromo-3-(3-iodopropyl)-,
1,3-dibromo-5-(2-iodoethyl)- and
1,3-dibromo-5-(3-iodopropyl)benzenes; and substituted
perfluorobenzenes such as 1-iodo-2-bromo-, 1-iodo-3-bromo-,
1-iodo-4-bromo-, 3,5-dibromo-1-iodo- and
3,5-diiodo-1-bromoperfluorobenzenes.
[0036] The iodated compound can be, for example, any of
1,2-diiodotetrafluoroethane, 1,3-diiodohexafluoropropane,
1,4-diiodooctafluorobutane, iodoperfluoroethylene,
iodo-1,1-difluoroethylene, iodoethylene, 2-iodoperfluoroethyl vinyl
ether, 1,7-diiodoperfluoro-n-octane, 1,12-diiodoperfluorododecane,
1,16-diiodoperfluorohexadecane,
1,3-diiodo-2-chloroperfluoro-n-propane and
1,5-diiodo-2,4-dichloroperfluoro-n-pentane.
[0037] Furthermore, compounds of the general formula [I] wherein R
has a functional group are also preferably employed.
[0038] As such compounds, there can be mentioned, for example,
brominated vinyl ethers of the general formula [I] wherein n=1,
m=0, and R is R.sup.1--O--CF.dbd.CF.sub.2 [R.sup.1 representing a
perfluoroalkyl group]. Examples of the brominated vinyl ethers
include:
[0039] CF.sub.2BrCF.sub.2OCF.dbd.CF.sub.2,
[0040] CF.sub.2Br(CF.sub.2).sub.2OCF.dbd.CF.sub.2,
[0041] CF.sub.2Br(CF.sub.2).sub.3OCF.dbd.CF.sub.2,
[0042] CF.sub.3CFBr(CF.sub.2).sub.2OCF.dbd.CF.sub.2, and
[0043] CF.sub.2Br (CF.sub.2).sub.4CF.dbd.CF.sub.2.
[0044] These brominated vinyl ethers can be synthesized by known
processes, for example, the process described in U.S. Pat. No.
4,745,165.
[0045] Also, use can be made of brominated vinyl ethers of the
general formula [I] wherein n=1, m=0, and R is R.sup.2OCF.dbd.CFBr
or R.sup.2OCBr.dbd.CF.sub.2 [R.sup.2 representing a lower alkyl
group or a fluoroalkyl group]. These brominated vinyl ethers can be
synthesized by known processes, for example, the process described
in U.S. Pat. No. 4,564,662.
[0046] The brominated compound, iodated brominated compound or
iodated compound according to the present invention acts as a chain
transfer agent for forming crosslink sites in the copolymer and
regulates the molecular weight of the copolymer to thereby enable
to enhance the processability of the crosslinkable composition.
[0047] With respect to the above compounds, for example, the
iodated brominated compound, it is presumed that, at the time of
polymerization, the formation of organic peroxide radicals induces
easy radical cleavage of iodine and bromine from the iodated
brominated compound, monomer additive propagation reaction is
realized by the high reactivity of thus generated radicals, and
thereafter the reaction is terminated by abstraction of iodine and
bromine from the iodated brominated compound, with the result that
the fluoroelastomer having iodine and bromine bonded to molecular
terminals thereof, can be provided. The iodine and bromine atoms
bonded to the molecular terminals of the fluoroelastomer act as
crosslink sites at the time of peroxide curing.
[0048] In the fluoroelastomer of the present invention, vinylidene
fluoride from which the constituent units (a) are derived is used
in an amount of 65 to 85 mol %, preferably 70 to 80 mol %. When the
amount of vinylidene fluoride is smaller than 65 mol % in the
copolymerization, the curing product from the crosslinkable
composition containing the fluoroelastomer may suffer deterioration
of low-temperature properties. On the other hand, when the amount
exceeds 85 mol %, the curing product from the crosslinkable
composition containing the fluoroelastomer may suffer deterioration
of resistances to solvents and chemicals.
[0049] Perfluoro(methoxypropyl vinyl ether) from which the
constituent units (b) according to the present invention are
derived is used in an amount of 0.5 to 30 mol %, preferably 6 to 25
mol %, and still preferably 8 to 20 mol %. The use of
perfluoro(methoxypropyl vinyl ether) in the above amount in the
copolymerization is preferred not only from the viewpoint that
there can be obtained a curing product of crosslinkable composition
containing fluoroelastomer with excellent low-temperature
properties but also from the economic viewpoint.
[0050] Tetrafluoroethylene from which the constituent units (c)
optionally contained in the present invention are derived is used
in an amount of 0 to 10 mol %, preferably 4 to 8 mol %. When the
amount of tetrafluoroethylene exceeds 10 mol % in the
copolymerization, the curing product from the crosslinkable
composition containing the fluoroelastomer may suffer from
deterioration of low-temperature properties.
[0051] Perfluoroalkyl vinyl ether from which the constituent units
(d) optionally contained in the present invention are derived is
used in an amount of 0 to 25 mol %, preferably 5 to 15 mol %.
[0052] Moreover, the total usage of monomers from which these
constituent units (a), (b), (c) and (d) are derived is 100 mol
%.
[0053] When the compound of the general formula [I] is used, it is
preferably added in an amount of 0.001 to 5% by weight, still
preferably 0.01 to 3% by weight, based on the total of vinylidene
fluoride and perfluoro(methoxypropyl vinyl ether), optionally
together with tetrafluoroethylene and/or perfluoroalkyl vinyl
ether. When the amount of the compound is in the above ranges, a
curing product exhibiting not only excellent compression permanent
set characteristics but also excellent elongation ratio can be
obtained.
<Copolymerization Reaction>
[0054] The fluoroelastomer of the present invention is obtained by
copolymerizing the vinylidene fluoride and the
perfluoro(methoxypropyl vinyl ether), optionally together with the
tetrafluoroethylene and/or the perfluoroalkyl vinyl ether.
[0055] The copolymerization of the present invention can optionally
be performed in the presence of a compound selected from a
brominated compound, an iodated brominated compound and an iodated
compound.
[0056] The copolymerization of the present invention can generally
be performed by the emulsion polymerization technique wherein the
reaction is effected in a water- base medium in the presence of a
water-soluble peroxide catalyst, preferably a redox catalyst
thereof. The copolymerization can also be performed by the radical
solution polymerization technique in which use is made of a
fluorinated solvent.
[0057] The polymerization according to the emulsion polymerization
technique will hereinafter be described.
[0058] For example, persulfate salts such as ammonium persulfate,
potassium persulfate and sodium persulfate are preferably used as
the above water-soluble peroxide catalyst in the emulsion
polymerization.
[0059] As an agent for effecting emulsification, use can be made
of, for example, fluorinated emulsifiers such as fluorinated
aliphatic carboxylates and fluorinated alcohol phosphates or
sulfates, or common emulsifiers such as higher aliphatic alcohol
sulfates and aromatic sulfonates. These water-soluble emulsifiers
can be used either individually or in combination.
[0060] It is preferred that each emulsifier be used in an amount of
about 0.001 to 10% by weight, especially about 0.01 to 5% by
weight, based on the water-base medium.
[0061] The emulsion polymerization in the presence of the above
water-soluble peroxide catalyst and emulsifier is carried out at
about 0 to 80.degree. C., preferably about 20 to 60.degree. C. When
the reaction temperature exceeds 80.degree. C., the formed
copolymer may have an unfavorably low molecular weight. Further,
the decomposition rate of polymerization catalyst may become so
high as to incur an efficiency lowering. On the other hand, when
the reaction temperature is lower than 0.degree. C., the
polymerization rate may become too low to realize practical
operation. With respect to the polymerization pressure, the higher,
the more desirable, as long as the copolymer of homogeneous
composition can be obtained. Generally, however, the employed
pressure is about 100 kg/cm.sup.2G or below.
[0062] Although the molecular weight of the fluoroelastomer
obtained as the copolymer according to the present invention is not
particularly limited, it is generally preferred that, for example,
the number average molecular weight (Mn, measured by GPC in a
solvent of THF) be in the range of 10,000 to 1,000,000, especially
50,000 to 300,000. The solution viscosity, .eta..sub.sp/C (at
35.degree. C. in methyl ethyl ketone), as an index of molecular
weight is preferably in the range of 0.1 to 5 dl/g, still
preferably 0.5 to 3.5 dl/g.
[0063] In the present invention, the molecular weight of obtained
fluoroelastomer can be regulated by adding a chain transfer agent,
such as methanol, ethanol, isopentane, diethyl malonate or carbon
tetrachloride, at the time of polymerization for obtaining the
copolymer, if necessary.
[0064] The fluoroelastomer thus obtained is a copolymer
comprising:
[0065] constituent units derived from vinylidene fluoride (a),
and
[0066] constituent units derived from perfluoro(methoxypropyl vinyl
ether) (b),
[0067] optionally together with constituent units derived from
tetrafluoroethylene (c) and/or constituent units derived from a
perfluoroalkyl vinyl ether (d),
[0068] wherein:
[0069] the constituent units (a) are contained in an amount of 65
to 85 mol %, preferably 70 to 80 mol %,
[0070] the constituent units (b) are contained in an amount of 0.5
to 30 mol %, preferably 6 to 25 mol %, and still preferably 8 to 20
mol %,
[0071] the constituent units (c) are contained in an amount of 0 to
10 mol %, preferably 4 to 8 mol %, and
[0072] the constituent units (d) are contained in an amount of 0 to
25 mol %, preferably 5 to 15 mol % (provided that
(a)+(b)+(c)+(d)=100 mol %).
[0073] When this fluoroelastomer further comprises the compound
represented by the general formula RBr.sub.nI.sub.m [wherein R
represents any of a fluorohydrocarbon group, a
chlorofluorohydrocarbon group, a chlorohydrocarbon group and a
hydrocarbon group, and each of n and m is 0, 1 or 2], it is
preferred that the above constituent units (e) be contained in an
amount of 0.001 to 5 parts by weight, especially 0.001 to 5 parts
by weight, per 100 parts by weight of the sum of the constituent
units (a), (b) , (c) and (d)
[Crosslinkable Composition and Curing Product]
[0074] The crosslinkable composition of the present invention
comprises the above fluoroelastomer and a peroxide crosslinking
agent.
[0075] The fluoroelastomer-containing crosslinkable composition of
the present invention can be cured by various conventional
vulcanization methods, for example, the peroxide vulcanization
method using an organic peroxide, the polyamine vulcanization
method using a polyamine compound, the polyol vulcanization method
using a polyhydroxy compound and the irradiation method using
radiation or electron beams. Of these, the peroxide vulcanization
method is especially preferably employed because the crosslinkable
composition upon being cured is excellent in mechanical strength
and forms carbon-carbon bonds ensuring stable crosslink point
structure to thereby provide a composition which is excellent in
resistances to chemicals, wear and solvents.
[0076] The organic peroxide for use in the peroxide vulcanization
method can be, for example, any of
2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane,
2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane-3, benzoyl peroxide,
bis(2,4-dichlorobenzoyl) peroxide, dicumyl peroxide, di-tert-butyl
peroxide, tert-butyl cumyl peroxide, tert-butylperoxybenzene,
1,1-bis(tert-butylperoxy)-3,5,5-trimethylcyclohexane,
2,5-dimethylhexane-2,5-dihydroxy peroxide,
.alpha.,.alpha.'-bis(tert-buty- lperoxy)-p-diisopropylbenzene,
2,5-dimethyl-2,5-di(benzoylperoxy)hexane and
tert-butylperoxyisopropyl carbonate.
[0077] In the peroxide vulcanization method using these organic
peroxides, as a co-crosslinking agent, there can simultaneously be
employed a polyfunctional unsaturated compound such as
tri(meth)allyl isocyanurate, tri(meth)allyl cyanurate, triallyl
trimellitate, N,N'-m-phenylenebismalei- mide, diallyl phthalate,
tris(diallylamino)-s-triazine, triallyl phosphite,
1,2-polybutadiene, ethylene glycol diacrylate or diethylene glycol
diacrylate. The simultaneous use of this co-crosslinking agent
enables to obtain a crosslinkable composition which is excellent in
vulcanization characteristics, mechanical strength and compression
permanent set characteristics.
[0078] If desired, the crosslinkable composition can be loaded with
a bivalent metal oxide or hydroxide, such as an oxide or hydroxide
of calcium, magnesium, lead, zinc or the like, as a crosslinking
auxiliary. These compounds also act as an acid receptive agent.
[0079] With respect to the proportion of these components added to
the peroxide vulcanization system, it is preferred that the organic
peroxide be added in an amount of 0.1 to 10 parts by weight,
especially about 0.5 to 5 parts by weight, optionally the
co-crosslinking agent added in an amount of 0.1 to 10 parts by
weight, especially about 0.5 to 5 parts by weight, and optionally
the crosslinking auxiliary added in an amount of up to 15 parts by
weight, especially 2 to 10 parts by weight, per 100 parts by weight
of fluoroelastomer.
[0080] The crosslinkable composition of the present invention can
be prepared by directly adding the above components to the
fluoroelastomer and milling them. Alternatively, the above
components can be diluted with carbon black, silica, clay, talc,
diatom earth, barium sulfate or the like, or formed into a master
batch dispersion with the fluoroelastomer. The crosslinkable
composition can appropriately be loaded with conventional filler,
reinforcing agent, plasticizer, lubricant, processing auxiliary,
pigment, etc. in addition to the above components. When carbon
black is used as the filler or reinforcing agent, carbon black is
preferably added in an amount of about 10 to 50 parts by weight per
100 parts by weight of fluoroelastomer.
[0081] The curing of the crosslinkable composition can be
accomplished by heating the same after the mixing of the components
by common mixing methods such as the roll mixing, kneader mixing,
banbury mixing and solution mixing methods. Generally, the heating
thereof is preferably performed by press vulcanization at about 100
to 250.degree. C. for about 1 to 120 min, or by oven vulcanization
(post-cure) at about 150 to 300.degree. C. for 0 to about 30
hr.
EFFECT OF THE INVENTION
[0082] Curing product having excellent resistances to heat, cold
and solvents can be obtained by the use of the fluoroelastomer and
crosslinkable composition thereof according to the present
invention.
EXAMPLE
[0083] The present invention will further be illustrated below with
reference to the following Examples which in no way limit the scope
of the invention.
Example 1
[0084] A 500 ml autoclave was charged with:
[0085] 44 g (69.3 mol %) of vinylidene fluoride (VdF),
[0086] 6 g (6.1 mol %) of tetrafluoroethylene (TFE),
[0087] 24 g (14.6 mol %) of perfluoro(methyl vinyl ether)
[0088] (FMVE) and 32 g (10.0 mol %) of perfluoro(methoxypropyl
vinyl ether) (MPVE),
[0089] 5 g of ammonium perfluorooctanoate,
[0090] 0.54 g of Na.sub.2HPO.sub.4.multidot.12H.sub.2O,
[0091] 0.02 g of NaHSO.sub.3,
[0092] 200 ml of water, and
[0093] 1.0 g of CF.sub.2.dbd.CFOCF.sub.2CF.sub.2Br.
[0094] The mixture was heated to 50.degree. C., and 0.1 g of
ammonium persulfate was added thereto to thereby initiate a
polymerization. The reaction was performed for 8 hr, and the
mixture was cooled to about 30.degree. C. Unreacted gas was
released, and the polymerization was terminated.
[0095] The obtained product was subjected to salting out with the
use of a 2% aqueous solution of calcium chloride, and dried. Thus,
there was obtained 100.6 g (polymerization ratio: 94.0%) of white
fluoroelastomer.
[0096] The solution viscosity, .eta..sub.sp/C (at 35.degree. C. in
methyl ethyl ketone), of the fluoroelastomer was 3.06 dl/g.
[0097] .sup.19F-NMR analysis showed that the composition of this
fluoroelastomer was VdF/TFE/FMVE/MPVE=73.4/7.1/10.1/9.4 (molar
ratio). The results are given in Table 1. The .sup.19F-NMR spectrum
is shown in FIG. 1.
Example 2 and Comparative Examples 1 and 2
[0098] Polymerization was carried out under the same conditions as
in Example 1, except that the components were charged in the
amounts specified in Table 1 in place of the recipe of Example 1.
Thus, a fluoroelastomer was obtained. The results are given in
Table 1.
[0099] The solution viscosity, .eta..sub.sp/C (at 35.degree. C. in
methyl ethyl ketone), of the fluoroelastomer obtained in Example 2
was 1.96 dl/g. The solution viscosity, .eta..sub.sp/C (at
35.degree. C. in methyl ethyl ketone), of the fluoroelastomer
obtained in Comparative Example 1 was 0.98 dl/g.
Examples 3 and 4 and Comparative Examples 3 and 4
[0100] 100 parts by weight of each of the fluoroelastomers obtained
in Examples 1 and 2 and Comparative Examples 1 and 2 was loaded
with:
[0101] MT carbon black 30 parts by weight
[0102] triallyl isocyanurate (60%) 7 parts by weight
[0103] organic peroxide (Perhexa 2,5 B-40, produced by Nippon Yushi
K.K.) 1.4 parts by weight
[0104] zinc oxide (ZnO) 6 parts by weight.
[0105] The mixture was blended by means of a twin-roll mill and
subjected first to press vulcanization at 180.degree. C. for 10 min
and thereafter to oven vulcanization (post-curing) at 230.degree.
C. for 22 hr.
[0106] With respect to the cured sheets thus obtained, there were
measured the original-state properties (measured in accordance with
DIN 53505, 53504), the heat resistance (heat aging resistance test
at 230.degree. C. for 70 hr), the cold resistance (TR.sub.10 and
TR.sub.70) and the solvent resistance (ratio of volume change after
immersion in methanol at 25.degree. C. for 70 hr). The results are
given in Table 2.
1 TABLE 1 Comp. Ex. Comp. Ex. Example 1 Example 2 1 2 charged
monomer wt. VdF (g) 44 50 41 44 MPVE (g) 32 70 -- -- TFE (g) 6 -- 9
-- FMVE (g) 24 -- 30 32 charged monomer compsn. VdF (mol %) 69.3
78.2 70.0 78.0 MPVE (mol %) 10.0 21.8 -- -- TFE (mol %) 6.1 -- 10.0
-- FMVE (mol %) 14.6 -- 20.0 22.0 formed fluoroelastomer compsn.
VdF (mol %) 73.4 80.8 72.2 82.2 MPVE (mol %) 9.4 19.2 -- -- TFE
(mol %) 7.1 -- 10.0 -- FMVE (mol %) 10.1 -- 17.8 17.8
[0107]
2TABLE 2 Example Example Comp. Ex. Comp. Ex. 3 4 3 4
fluoroelastomer Example Example Comp. Ex. Comp. Ex. as feedstock 1
2 1 2 original-state properties hardness (Shore A) 70 64 75 70
(pts) tensile strength 14.6 9.7 18.4 18.0 (MPa) elongation (%) 280
260 250 310 heat aging resistance test A.sub.H (pts) 0 +1 0 0
A.sub.C (% T.sub.H) -6 +1 -7 -8 A.sub.C (% E.sub.H) -7 +8 +8 +3
cold resistance TR.sub.10 (.degree. C.) -36.3 -42.4 -30.9 -32.4
TR.sub.70 (.degree. C.) -25.6 -8.8 -23.4 -24.5 solvent resistance
31.6 21.7 79.6 153.5 methanol (%)
* * * * *