Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-09-30
2001-08-14
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S200000, C525S326200, C526S247000, C526S255000
Reexamination Certificate
active
06274677
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process of the preparation of a perfluorovinyl ethersulfonic acid derivative, and a copolymer comprising such a derivative. In particular, the present invention relates to an improved process for synthesizing a perfluorovinyl ethersulfonic acid derivative which can be used as a monomer to prepare a strongly acidic fluorine-containing polymeric electrolyte, and the use of such a derivative as a monomer of a block copolymer.
PRIOR ART
In general, perfluorovinyl ethersulfonic acid derivatives are synthesized according to a reaction path shown in following Scheme 1:
In the conventional reaction, the intramolecular cyclization of a compound takes place in the final pyrolysis step depending on the number of n (see Scheme 1), and thus, the yield of intended vinyl ethers may decrease, or the cyclization reaction selectively proceeds particularly when n is 0. Therefore, CF
2
═CFOCF
2
CF
2
SO
2
F (II) cannot be obtained.
Accordingly, a compound of the formula (I) in which n is 1 or 2 is selected and practically used as a monomer for a sulfonic acid type ionomer.
Carboxylic acid type ionomers are also proposed as such ionomers, and a crystalline copolymer comprising CF
2
═CF[OCF
2
CF(CF
3
)]
n
OCF
2
CF
2
COOH and tetrafluoroethylene is commonly used.
Sulfonic acid type ionomers and carboxylic acid type ionomers have their own advantages and disadvantages, and they have complementary characteristics to each other. It is known that their properties are improved by various methods such as modification or compounding, when they are used in the form of an ion-exchange membrane.
The above compound (II) has a good copolymerizing reactivity with various olefins, and can be easily copolymerized with, in particular, tetrafluoroethylene to give an ionomer having a large ion-exchange capacity. In view of such utility of the compound (II), it has been proposed to synthesize the compound (II) according to the reaction path of following Scheme 2 while avoiding the formation of cyclic compounds in Scheme 1:
However, this process has a problem that it should use a special chlorine-containing epoxy compound. A method is also known, which comprises ring opening the cyclic compound in Scheme 1 with an alkali metal alcoholate to obtain the compound (II), but no satisfactory result has been attained.
Such known copolymeric ionomers are crystalline and designed so that they are not swelled with or dissolved in water. Thus, it has been believed that copolymers having a high ion-exchange capacity of 600 g/mole or less would have less utility. However, water-soluble amorphous copolymers having a high ion-exchange capacity can be readily obtained, when the compound (II) is used in the form of a water-soluble salt having the formula:
CF
2
═CFOCF
2
CF
2
SO
3
Na (III)
is used and copolymerized with tetrafluoroethylene, trifluoroethylene, vinylidene fluoride, ethylene, etc.
When such amorphous copolymers are further subjected to a living radical polymerization, which is known as “an iodine-transfer polymerization method” (see “KOBUNSHI RONBUNSHU” (Collected Papers on Polymers), Vol. 49, No. 10 (1992) 765-783, and Polymeric Materials Encyclopedia, Vol. 5, 3847-3860 (CRC Press)), to obtain block or graft copolymers with water-insoluble polymers such as copolymers of tetrafluoroethylene with hexafluoropropylene or a perfluoroalkyl vinyl ether (e.g. CF
2
═CFOC
3
F
7
), which are known as “FEP” or “PFA”, polyvinylidene fluoride, or other fluoropolymers, the obtained polymers become water-insoluble and have a minimum swelling property in water. Accordingly, ionomers having a large ion-exchange capacity of 600 g/mole or less and good mechanical properties can be obtained.
The same measures can be applied to the carboxylic acid type ionomers.
From such a viewpoint, an effective synthesis method of a sulfonic acid derivative having a minimally stable structure such as a compound of the formula (III) is desired to design an ionomer having a large ion-exchange capacity.
SUMMARY OF THE INVENTION
As the result of extensive studies, it has been found that, when a raw material having a —SO
2
F group used in the final reaction step in Scheme 1 is once converted to a sulfonate salt (e.g. —SO
3
Na), completely dried and then pyrolyzed, the raw material can be converted to a desired product while suppressing the cyclization reaction.
Accordingly, the present invention provides a process for the preparation of a vinyl ethersulfonic acid derivative comprising the steps of:
converting a compound of the formula (1):
FSO
2
CFXCF
2
O(CFXCF
2
O)
n
CF(CF
2
Y)COF (1)
wherein X is a fluorine atom, a chlorine atom or a trifluoromethyl group, Y is a fluorine atom, a chlorine atom, a bromine atom or an iodine atom, and n is a number of 0 to 5, preferably 0, 1 or 2 to a compound of the formula (2):
MOSO
2
CFXCF
2
O(CFXCF
2
O)
n
CF(CF
2
Y)COOM
1
(2)
wherein X, Y and n are the same as defined above, and M and M
1
independently represent an alkali metal atom or an alkaline earth metal atom, and
pyrolyzing a compound of the formula (2) at a temperature of 150 to 250° C. to obtain a compound of the formula (3):
MOSO
2
CFXCF
2
O(CFXCF
2
O)
n
CF═CF
2
(3)
wherein X, M and n are the same as defined above.
REFERENCES:
patent: 4804727 (1989-02-01), Ezzell et al.
patent: 5981673 (1999-11-01), DeSimone et al.
patent: 57-85367 (1982-05-01), None
patent: 58-500567 (1983-04-01), None
patent: 63-310988 (1988-12-01), None
patent: 5221880 (1993-05-01), None
Asinovsky Olga
Daikin Industries Ltd.
Nutter Nathan M.
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