A fluorine-containing polymer composition comprising a solvent containing a block compound composed of a polyfluorinated segment and a hydrocarbon segment and a fluorine-containing polymer having a fluorine-containing aliphatic cyclic structure dissolved in the solvent.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a fluorine-containing polymer composition. 
2. Discussion of Background 
It is known from Japanese Unexamined Patent Publication No. 129254/1990 
that a polymer having a fluorine-containing aliphatic cyclic structure not 
only shows characteristics of a conventional fluorinated resin but also is 
soluble in a certain specific solvent. The specific solvent is a perfluoro 
compound such as perfluoroalkane, a perfluorocyclic ether or a 
perfluoroalkylamine. By properly selecting the type of the solvent, it is 
possible to prepare a composition suitable for use under particular 
coating conditions or drying conditions, and a uniform transparent coating 
film can be obtained. However, a solution obtainable by such a perfluoro 
solvent is usually of high viscosity, and there has been a problem that if 
the polymer concentration in the solution is increased to form a thick 
film, the viscosity of the solution tends to be very high, whereby 
defoaming or filtration tends to be difficult. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to solve the above-mentioned 
drawbacks inherent to the prior art and to provide a fluorine-containing 
polymer composition, whereby there will be no substantial increase in the 
viscosity of the solution even when the polymer concentration is 
increased, and defoaming or filtration can easily be conducted. 
The present inventors have found anew that the polymer having a 
fluorine-containing aliphatic cyclic structure is soluble not only in the 
perfluoro compound hitherto known but also in a block compound composed of 
a polyfluorinated segment and a hydrocarbon segment. Further, it has been 
found that the viscosity of the solution can be made relatively low when 
this block compound is used as the solvent. 
The present invention has been accomplished on the basis of these 
discoveries and provides anew a fluorine-containing polymer composition 
comprising a solvent containing a block compound composed of a 
polyfluorinated segment and a hydrocarbon segment and a 
fluorine-containing polymer having a fluorine-containing aliphatic cyclic 
structure dissolved in the solvent. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the present invention, when the specific block compound is used as a 
solvent, the viscosity of the solution at the same concentration can be 
reduced over the case where the above-mentioned perfluoro compound is used 
as a solvent, by the effects attributable to the presence of the 
hydrocarbon unit in the molecule, whereby it is possible to obtain a 
solvent which is excellent in the operational efficiency from the 
viewpoint of defoaming, filtration, etc. Otherwise, at the same level of 
viscosity, the concentration of the solution can be increased, whereby it 
is possible to obtain a solution excellent in thick coating properties. 
The concentration of the solution is usually from 1 to 30 wt%, preferably 
from 1 to 20 wt%. 
In the block compound to be used in the present invention, the 
polyfluorinated segment is a segment having at least two fluorine-bonded 
carbon atoms linked to one another. Specifically, it includes, for 
example, a polyfluoroalkyl group having at least two carbon atoms, such as 
a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group or 
a 1,1,2,2,3,3-hexafluoropropyl group, a polyfluoroalkylene group such as a 
perfluoroethylene group or a perfluorobutylene group, and a 
polyfluoroalkenyl group such as CF.sub.2 .dbd.CFCF.sub.2 CF.sub.2 --. 
Further, it may be the one partially substituted by a halogen atom such as 
chlorine or by an oxygen atom. 
The hydrocarbon segment is basically a group composed solely of carbon and 
hydrogen, but may contain a hetero atom such as an ether-type oxygen atom. 
Specifically, it includes, for example, an alkyl group such as a methyl 
group, an ethyl group, a propyl group or a butyl group, an alkenyl group 
such as a vinyl group or an allyl group, and an alkylene group such as an 
ethylene group or a butylene group. It is especially preferred with a view 
to reduction of the viscosity of the solution that the hydrocarbon segment 
has at least two carbon atoms. 
The block compound comprises at least one such polyfluorinated segment and 
at least one such hydrocarbon segment linked to one another. Specifically, 
its basic structure may, for example, be Rf--Rh, Rf--Rh--Rf or Rh--Rf--Rh 
wherein Rf represents the polyfluorinated segment and Rh represents the 
hydrocarbon segment. 
From the viewpoint of the solubility of the fluorine-containing polymer, 
the block compound is preferably such that the total number of carbon 
atoms constituting the polyfluorinated segment is larger than the total 
number of carbon atoms constituting the hydrocarbon segment. It is 
particularly preferred that the total number of carbon atoms constituting 
the polyfluorinated segment is at least twice the total number of carbon 
atoms constituting the hydrocarbon segment. 
If the total number of carbon atoms is too large, the block compound will 
no longer be in a liquid state at room temperature, or its boiling point 
will be so high that it will no longer be suitable as a solvent for 
coating. The total number of carbon atoms is preferably not larger than 
30. Further, if the number of carbon atoms of the polyfluorinated segment 
is too small, the solubility of the fluorine-containing polymer will be 
low, such being undesirable. The number of carbon atoms constituting the 
polyfluorinated segment is preferably at least 6. It is further preferred 
that the polyfluorinated segment is completely fluorinated. 
By properly selecting the combination and types of the polyfluorinated 
segment and the hydrocarbon segment of the block compound, the boiling 
point, the viscosity and the solubility can be selected within wide 
ranges, respectively, and it is accordingly possible to prepare a 
composition suitable under particular coating conditions or drying 
conditions and to obtain a uniform coating film having an optional 
thickness. 
Further, the block compound of the present invention may be mixed with a 
conventional perfluoro solvent such as perfluorotributylamine or 
perfluoro-2-butyltetrahydrofuran at an optional ratio and can be used as a 
solvent mixture. 
In the present invention, Rf-Rh wherein Rf is a C.sub.6-12 perfluoroalkyl 
group, and Rh is a C.sub.1-4 alkyl group or a C.sub.2-4 alkenyl group, may 
be mentioned as a preferred block compound. Here, the Rh segment is not 
particularly limited so long as it is the one having from 1 to 4 carbon 
atoms, and it may, for example, be --CH.sub.3, --CH.sub.2 CH.sub.3, 
--CH.dbd.CH.sub.2, --CH.sub.2 CH.dbd.CH.sub.2, --CH.dbd.CHCH.sub.3, 
--C(CH.sub.3).dbd.CH.sub.2, --CH.sub.2 CH.sub.2 CH.sub.3, --CH.sub.2 
CH.sub.2 CH.dbd.CH.sub.2, --CH.sub.2 CH.dbd.CHCH.sub.3, 
--CH.dbd.CHCH.sub.2 CH.sub.3 or --CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.3. 
Such a compound may be synthesized, for example, as follows: 
##STR1## 
Namely, compound (2) (m=1 or 2) can be obtained by reacting compound (1) 
with ethylene in the presence of a radical initiator. Here, when the 
pressure of ethylene is at a level of from 3 to 8 kg/cm.sup.2.G, a 1 mol 
adduct is selectively produced. When the pressure of ethylene is at a 
level of from 20 to 25 kg/cm.sup.2.G, a 2 mol adduct will be formed as the 
main product. Compound (3) can be quantitatively obtained by heating and 
stirring compound (2) and a basic aqueous solution in the presence of a 
phase transfer catalyst. Compound (4) can be obtained by hydrogenating 
compound (3) in the present of a hydrogenation catalyst such as Raney 
nickel. 
Compound (5) can be obtained by reacting compound (1) with propylene in the 
presence of a radical initiator. Compound (6) can quantitatively be 
obtained by heating and stirring compound (5) and a basic aqueous solution 
in the presence of a phase transfer catalyst. Compound (7) can be obtained 
by hydrogenating compound (6) in the presence of a hydrogenation catalyst 
such as Raney nickel. 
Here, the Rf group is a C.sub.6-12 linear or branched perfluoroalkyl group, 
and the following groups may, for example, be mentioned: 
##STR2## 
The polymer having a fluorine-containing aliphatic cyclic structure 
includes a wide range of such polymers including known or well known 
polymers having a cyclic structure in the main chain, which are obtainable 
by polymerizing a monomer having a fluorine-containing cyclic structure or 
which are obtainable by cyclic polymerization of a fluorine-containing 
monomer having at least two polymerizable double bonds. 
The polymers having a cyclic structure in the main chain, which are 
obtainable by cyclic polymerization of a fluorine-containing monomer 
having at least two polymerizable double bonds, are known, for example, in 
Japanese Unexamined Patent Publications No. 238111/1988 and No. 
238115/1988. Namely, they can be obtained by homopolymerization of a 
monomer such as perfluoro(allylvinyl ether) or perfluoro(butenylvinyl 
ether) or by copolymerization of such a monomer with a radical 
polymerizable monomer such as tetrafluoroethylene. 
The polymers having a cyclic structure in the main chain, which are 
obtainable by polymerizing a monomer having a fluorine-containing cyclic 
structure, are known, for example, in Japanese Examined Patent Publication 
No. 18964/1988. Namely, they may be obtained by homopolymerization of a 
monomer having a fluorine-containing cyclic structure such as 
perfluoro(2,2-dimethyl-1,3-dioxol), or by copolymerization of such a 
monomer with a radical-polymerizable monomer such as tetrafluoroethylene. 
Further, the fluorine-containing polymer may be a polymer obtainable by 
copolymerizing a monomer having a fluorine-containing cyclic structure 
such as perfluoro(2,2-dimethyl-1,3-dioxol) with a fluorine-containing 
monomer having at least two polymerizable double bonds, such as 
perfluoro(butenylvinyl ether). 
The polymer having a fluorine-containing aliphatic cyclic structure is 
preferably a polymer having a cyclic structure in the main chain. The one 
containing at least 20 mol% of a cyclic structure is preferred from the 
viewpoint of the transparency and mechanical properties. 
Now, the present invention will be described in further detail with 
reference to Examples. However, it should be understood that the present 
invention is by no means restricted by such specific Examples.

PREATION EXAMPLE 1 
Preparation of a Polymer Having a Fluorine-Containing Aliphatic Cyclic 
Structure 
35 g of perfluorobutenyl vinyl ether, 5 g of R113 
1,1,2-trichlorotrifluoroethane), 150 g of deionized water and 90 mg of 
((CH.sub.3).sub.2 CHOCOO).sub.2 as a polymerization initiator, were 
charged into a pressure resistant glass autoclave having an internal 
capacity of 200 ml. The interior of the system was flushed three times 
with nitrogen, and then suspension polymerization was conducted at 
40.degree. C. for 22 hours, to obtain 28 g of polymer A. The polymer had a 
glass transition temperature of 108.degree. C., and it was a glass-like 
polymer which was tough and transparent at room temperature. Its 10% heat 
decomposition temperature was 46.degree. C., and its light transmittance 
was at least 95%. 
PREATION EXAMPLE 2 
Preparation of a Polymer Having a Fluorine-Containing Aliphatic Cyclic 
Structure 
Perfluoro(2,2-dimethyl-1,3-dioxol) and tetrafluoroethylene were subjected 
to radical-copolymerization to obtain copolymer B having a glass 
transition temperature of 160.degree. C. This polymer was colorless and 
transparent. The refractive index was 1.3, and the transmittance was also 
high. 
EXAMPLE 1 
Polymer A prepared in Preparation Example 1 was dissolved in CF.sub.3 
(CF.sub.2).sub.7 CH.dbd.CH.sub.2 (boiling point: 150.degree. C.) and 
CF.sub.3 (CF.sub.2).sub.7 CH.sub.2 CH.sub.3 (boiling point: 155.degree. 
C.) to obtain solutions having a solid content concentration of 9 wt%, 
which were designated as compositions A and B, respectively. The 
viscosities of these solutions are shown in Table 1. 
COMATIVE EXAMPLE 1 
Polymer A was dissolved in a perfluoro solvent Afrude E-16 
(perfluorotributylamine, manufactured by Asahi Glass Company Ltd.) 
(boiling point: 155.degree. C.) having a boiling point close to CF.sub.3 
(CF.sub.2).sub.7 CH.dbd.CH.sub.2 and CF.sub.3 (CF.sub.2).sub.7 CH.sub.2 
CH.sub.3 used in Example 1, to obtain a solution having a solid content 
concentration of 9 wt%, which was designated as composition C. The 
viscosity of this solution is shown in Table 1. This solution was filtered 
through a membrane filter manufactured by Advantec, whereby the filtration 
speed was very slow, and clogging was observed. Further, coating onto a 
glass substrate was conducted by means of a spin coater, whereby inclusion 
of foams was observed, and it was impossible to obtain a uniform coating 
film. 
Compositions A and B had low viscosities as compared with composition C and 
were excellent in the operational efficiency such as defoaming or 
filtration. 
TABLE 1 
______________________________________ 
Boil- Viscosity 
ing of a 9 wt % 
Composi- point solution 
tion Solvent (.degree.C.) 
(cp) 
______________________________________ 
Example 1 
A CF.sub.3 (CF.sub.2).sub.7 CH.dbd.CH.sub.2 
150 300 
B CF.sub.3 (CF.sub.2).sub.7 CH.sub.2 CH.sub.3 
155 450 
Compara- 
C Afrude E-16 155 890 
tive 
Example 1 
______________________________________ 
EXAMPLE 2 
Polymer A was dissolved in CF.sub.3 (CF.sub.2).sub.5 CH.sub.2 CH.sub.3 
(boiling point: 116.degree. C.) to obtain a solution having a solid 
content concentration of 9 wt%, which was designated as composition D. The 
viscosity of this solution is shown in Table 2. 
COMATIVE EXAMPLE 2 
Polymer A was dissolved in a perfluoro solvent Afrude E-10 
(perfluoro-2-butyltetrahydrofuran, manufactured by Asahi Glass Company 
Ltd.) (boiling point: 100.degree. C.) having a boiling point close to 
CF.sub.3 (CF.sub.2).sub.5 CH.sub.2 CH.sub.3 used in Example 2, to obtain a 
solution having a solid content concentration of 9 wt%, which was 
designated as composition E. The viscosity of this solution is shown in 
Table 2. 
Composition D had a low viscosity as compared with composition E and was 
excellent in the operational efficiency such as defoaming or filtration. 
TABLE 2 
______________________________________ 
Boil- Viscosity 
ing of a 9 wt % 
Composi- point solution 
tion Solvent (.degree.C.) 
(cp) 
______________________________________ 
Example 2 
D CF.sub.3 (CF.sub.2).sub.5 CH.sub.2 CH.sub.3 
116 90 
Compara- 
E Afrude E-10 100 150 
tive 
Example 2 
______________________________________ 
EXAMPLE 3 AND COMATIVE EXAMPLE 3 
Using CF.sub.3 (CF.sub.2).sub.7 CH.sub.2 CH.sub.3 and Afrude E-16 as 
solvents, solutions of polymer A having a viscosity of 250 cp were 
prepared, which were designated as composition F (Example 3) and 
composition G (Comparative Example 3), respectively. The solid content 
concentrations were 8.3 wt% and 6.9 wt%, respectively. Then, using these 
solutions, coating films were formed on a glass substrate under the 
following conditions by means of a spin coater. 
Film-forming Conditions 
Rotational speed of the spin coater: 2,000 rpm 
Drying condition: 160.degree. C. for one hour 
As a result, from composition F, a coating film having a thickness of 1.3 
.mu.m was obtained, and from composition G, a coating film having a 
thickness of 0.8 .mu.m was obtained. Thus, composition F was superior in 
the thick coating properties. 
EXAMPLE 4 AND COMATIVE EXAMPLE 4 
The operation was conducted in the same manner as in Example 3 and 
Comparative Example 3 except that polymer A was changed to polymer B, 
whereby the composition using CF.sub.3 (CF.sub.2).sub.7 CH.sub.2 CH.sub.3, 
had a higher concentration as a solution than the composition using Afrude 
E-18 and thus was superior in the thick coating properties. 
The fluorine-containing polymer composition of the present invention has an 
advantage such that it gives a uniform transparent coating film of 
fluorine resin by coating. Further, by using a compound having a 
hydrocarbon segment in its molecule, as a solvent, it is possible to 
accomplish a reduction in the viscosity of a solution as compared with a 
case where a perfluoro compound is used as a solvent, thus providing a 
merit that the operational efficiency is thereby improved. Further, at the 
same viscosity, the concentration of the solid content can be made high, 
whereby it is possible to obtain a solution excellent in the thick coating 
properties.