Process for producing liquid composition and process for producing catalyst layer-forming coating liquid
A process for producing a liquid composition, which includes holding a fluorinated polymer having —SO 2 F groups at from 140 to 160° C. for at least 45 minutes, cooling it to less than 110° C. at a rate of at least 50° C./min, converting the —SO 2 F groups in the fluorinated polymer to ion exchange groups to obtain a fluorinated polymer having ion exchange groups, and mixing the fluorinated polymer having ion exchange groups and a liquid medium.
1. A process for producing a liquid composition, which comprises
holding a fluorinated polymer having —SO 2 F groups at from 140 to 160° C. for at least 45 minutes,
cooling it to less than 110° C. at a rate of at least 50° C./min,
converting the —SO 2 F groups in the fluorinated polymer to ion exchange groups to obtain a fluorinated polymer having ion exchange groups, and
mixing the fluorinated polymer having ion exchange groups and a liquid medium.
2. A process for producing a liquid composition, which comprises
cooling a fluorinated polymer having —SO 2 F groups in a melt state to from 140 to 160° C. and holding it at from 140 to 160° C. for at least 10 minutes,
cooling it to less than 110° C. at a rate of at least 50° C./min,
converting the —SO 2 F groups in the fluorinated polymer to ion exchange groups to obtain a fluorinated polymer having ion exchange groups, and
mixing the fluorinated polymer having ion exchange groups and a liquid medium.
3. The process for producing a liquid composition according to claim 1 , wherein the fluorinated polymer having —SO 2 F groups has either one or both of structural units represented by the following formula (u1) and structural units represented by the following formula (u2), and structural units derived from tetrafluoroethylene:
wherein Q 1 is a single bond or a perfluoroalkylene group which may have an etheric oxygen atom, Y 1 is a fluorine atom or a monovalent perfluoroorganic group, s is 0 or 1; Q 21 is a pefluoroalkylene group which optionally having an etheric oxygen atom, Q 22 is a single bond or a perfluoroalkylene group which optionally having an etheric oxygen atom, Y 2 is a fluorine atom or a monovalent perfluoroorganic group, and t is 0 or 1.
4. The process for producing a liquid composition according to claim 3 , wherein the fluorinated polymer having ion exchange groups has an ion exchange capacity of from 0.5 to 1.8 meq/g dry resin when it has structural units represented by the formula (u1) and has no structural units represented by the formula (u2), or from 0.5 to 2.8 meq/g dry resin when it has structural units represented by the formula (u2).
5. The process for producing a liquid composition according to claim 1 , wherein the TQ value of the fluorinated polymer having —SO 2 F groups is from 150 to 350° C.
6. A process for producing a catalyst layer-forming coating liquid, which comprises preparing a liquid composition by the process for producing a liquid composition as defined in claim 1 , subjecting the liquid composition to filtration through a filter, and mixing the liquid composition subjected to filtration through a filter and a catalyst to prepare a catalyst layer-forming coating liquid.