Fluorine-containing polymer composition

Details Fluorine-containing polymer composition Fluorine-containing polymer composition

1998-12-11

2001-03-13

Pezzuto, Helen L. (Department: 1713)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S242000, C526S248000, C526S249000, C526S251000, C526S253000

Reexamination Certificate

active

06201085

ABSTRACT:

The present invention relates to a fluorine-containing polymer composition comprising a specific fluorine-containing solvent and a fluorine-containing amorphous polymer having a fluorine-containing ring structure in its main chain, dissolved in the solvent.
Perfluoro polymers represented by a polytetrafluoroethylene, a tetrafluoroethylene/perfluoro (alkyl vinyl ether) copolymer and a tetrafluoroethylene/hexafluoropropylene copolymer, usually have excellent characteristics such that the heat resistance and chemical resistance are high, and the refractive index and the dielectric constant are small. However, these fluorine-containing polymers are usually insoluble in solvents.
WO96/22356 discloses that an amorphous tetrafluoroethylene copolymer is dissolved or dispersed in a solvent such as C
5
F
11
OCH
3
, C
5
F
11
OC
2
H
5
or C
8
F
17
OCH
3
to obtain a coating composition. However, there is no Example wherein an amorphous tetrafluoroethylene copolymer is actually dissolved in such a solvent, and it is uncertain whether or not an amorphous tetrafluoroethylene copolymer is in fact soluble in such a solvent.
Whereas, a fluorine-containing polymer having a fluorine-containing alicyclic structure in its main chain, as disclosed e.g. JP-B-8-22929, shows an amorphous nature, as the crystallization of the polymer is hindered by the steric effect of the ring structure. This fluorine-containing polymer is soluble in a specific perfluoro solvent such as perfluoro(2-butyltetrahydrofuran) even though it may be a perfluoro polymer. Accordingly, there is a merit in that from a perfluoro solvent solution of this fluorine-containing polymer, it is possible to form a thin film of the fluorine-containing polymer free from pinholes.
In recent years, with a view to global environmental protection, particularly to protection of the ozone layer, use of fluorochlorohydrocarbons has been banned, and from the viewpoint of warming up of the earth, use and discharge of carbon dioxide gas or perfluorohydrocarbons are desired to be restricted.
Especially perfluoro compounds such as perfluorohydrocarbons are said to substantially contribute to warming up of the earth because of their strong infrared ray absorbing abilities and their remarkably long lives in the atmosphere. For example, the estimated value for the life of perfluorohexane in the atmosphere is said to be from a few hundreds to a few thousands years. Such a perfluoro compound absorbs infrared rays over a long period of time and stores the radiation heat from the earth, whereby the influence over the warming up of the earth is believed to be substantial.
Under these circumstances, it is an object of the present invention to provide a fluorine-containing polymer composition having “a fluorine-containing amorphous polymer having a fluorine-containing ring structure in its main chain” (hereinafter referred to simply as a fluorine-containing ring structure-containing polymer) dissolved in a solvent which has a low contribution to warming up of the earth.
The present invention provides a fluorine-containing polymer composition comprising a fluorine-containing solvent of the formula R
1
—O—R
2
wherein R
2
is a C
5-12
linear or branched polyfluoroalkyl group which may have an ether bond, and R
2
is a C
1-5
linear or branched alkyl group, and a fluorine-containing polymer having a fluorine-containing ring structure in its main chain, dissolved in the solvent.
In the present invention, the fluorine-containing solvent is a fluorine-containing solvent of the formula R
1
—O—R
2
wherein R
1
is a C
5-12
linear or branched polyfluoroalkyl group which may have an ether bond, and R
2
is a C
1-5
linear or branched alkyl group.
If the carbon number of R
1
is 4 or less, it tends to be difficult to dissolve the fluorine-containing ring structure-containing polymer, and if the carbon number of R
1
is 13 or higher, such a solvent is hardly industrially available. Accordingly, the carbon number of R
1
is selected within a range of from 5 to 12. The carbon number of R
1
is preferably from 6 to 10, more preferably from 6 to 7 or 9 to 10.
The polyfluoroalkyl group is a group having at least two hydrogen atoms of an alkyl group substituted by fluorine atoms, and it includes a perfluoroalkyl group having all hydrogen atoms of an alkyl group substituted by fluorine atoms, and a group having at least two hydrogen atoms of an alkyl group substituted by fluorine atoms and having at least one hydrogen atom of the alkyl group substituted by a halogen atom other than a fluorine atom. As the halogen atom other than a fluorine atom, a chlorine atom is preferred.
The polyfluoroalkyl group is preferably a group having at least 60% in the number of hydrogen atoms of the corresponding alkyl group substituted by fluorine atoms, more preferably a group having at least 80% so substituted. A more preferred polyfluoroalkyl group is a perfluoroalkyl group.
When R
1
has an ether bond, the number of ether bonds in R
1
is usually from 1 to 3, more preferably 1 or 2, since if the number of ether bonds is too much, the solubility will be impaired.
If the carbon number of R
2
is 6 or higher, the solubility of the fluorine-containing ring structure-containing polymer will be substantially impaired. A preferred example of R
2
is CH
3
or C
2
H
5
.
The molecular weight of the fluorine-containing solvent is preferably at most 1,000, since if it is too large, not only the viscosity of the fluorine-containing polymer composition increases, but also the solubility of the fluorine-containing ring structure-containing polymer decreases. Further, in order to increase the solubility of the fluorine-containing ring structure-containing polymer, the fluorine content of the fluorine-containing solvent is preferably from 60 to 80 wt %.
The following may, for example, be mentioned as preferred fluorine-containing solvents.
F(CF
2
)
5
OCH
3
,
F(CF
2
)
6
OCH
3
,
F(CF
2
)
7
OCH
3
,
F(CF
2
)
8
OCH
3
,
F(CF
2
)
9
OCH
3
,
F(CF
2
)
10
OCH
3
,
H(CF
2
)
6
OCH
3
,
(CF
3
)
2
CF(OCH
3
)CFCF
2
CF
3
,
F(CF
2
)
3
OCF(CF
3
)CF
2
OCH
3
,
F(CF
2
)
3
OCF(CF
3
)CF
2
OCF(CF
3
)CF
2
OCH
3
,
F(CF
2
)
8
OCH
2
CH
2
CH
3
,
(CF
3
)
2
CFCF
2
CF
2
OCH
3
,
F(CF
2
)
2
O(CF
2
)
4
OCH
2
CH
3
.
As an example, the estimated life in the atmosphere of the fluorine-containing solvent in the present invention is from about 1 to 5 years in the case of F(CF
2
)
5
OCH
3
and F(CF
2
)
5
OCH
2
CH
3
. As the fluorine-containing solvent in the present invention, F(CF
2
)
6
OCH
3
, F(CF
2
)
7
OCH
3
, F(CF
2
)
8
OCH
3
, F(CF
2
)
9
OCH
3
and F(CF
2
)
10
OCH
3
are preferred, F(CF
2
)
6
OCH
3
, F(CF
2
)
7
OCH
3
, F(CF
2
)
9
OCH
3
and F(CF
2
)
10
OCH
3
are particularly preferred.
Such fluorine-containing solvents may be suitably used in combination as a mixture of two or more of them. In a case of a solvent mixture of a fluorine-containing solvent with other solvent, such other solvent may be a solvent which is by itself incapable of dissolving the fluorine-containing ring structure-containing polymer.
As such other solvents, fluorine-containing ethers other than the fluorine-containing solvent in the present invention, such as F(CF
2
)
4
OCH
3
and F(CF
2
)
4
OC
2
H
5
, hydrocarbons such as hexane, hydrochlorocarbons such as chloroform, hydrochlorofluorocarbons such as dichloropentafluoropropane, fluorine-containing aromatic hydrocarbons such as m-xylene hexafluoride and benzotrifluoride, and alcohols such as methanol, ethanol, (perfluorohexyl)ethanol and pentafluoropropanol, may, for example, be used in combination. The blend ratio of such other solvents is suitably selected depending upon the concentration of the fluorine-containing ring structure-containing polymer, but is preferably from 0.1 to 50 parts by weight, more preferably from 1 to 30 parts by weight, per 100 parts by weight of the fluorine-containing solvent.
In the present invention, the fluorine-containing ring structure-containing polymer may, for example, be a fluorine-containing polymer having a fluorine-containing alicyclic structure (including a fluorine-containing imid

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